Rapid casting solutions: a reviewMunish Chhabra
Department of Mechanical Engineering, Moradabad Institute of Technology, Moradabad, India, and
Rupinder SinghDepartment of Production Engineering, Guru Nanak Dev Engineering College, Ludhiana, India
AbstractPurpose – This paper seeks to review the industrial applications of state-of-the-art additive manufacturing (AM) techniques in metal castingtechnology. An extensive survey of concepts, techniques, approaches and suitability of various commercialised rapid casting (RC) solutions withtraditional casting methods is presented.Design/methodology/approach – The tooling required for producing metal casting such as fabrication of patterns, cores and moulds with RC directlyby using different approaches are presented and evaluated. Relevant case studies and examples explaining the suitability and problems of using RCsolutions by various manufacturers and researchers are also presented.Findings – Latest research to optimize the current RC solutions, and new inventions in processing techniques and materials in RC performed byresearchers worldwide are also discussed. The discussion regarding the benefits of RC solutions to foundrymen, and challenges to produce accurate andcost-effective RC amongst AM manufacturers concludes this paper.Research limitations/implications – The research related to this survey is limited to the applicability of RC solutions to sand casting and investmentcasting processes. There is practically no implication in industrial application of RC technology.Originality/value – This review presents the information regarding potential AM application – RC, which facilitates the fabrication of patterns, coresand moulds directly using the computer-aided design data. The information available in this paper serves the purpose of researchers and academicians toexplore the new options in the field of RC and especially users, manufacturers and service industries to produce casting in relatively much shorter time andat low cost and even to cast complex design components which otherwise was impossible by using traditional casting processes and CNC technology.
Keywords Additive manufacturing, Rapid casting solutions, Rapid investment casting, Rapid sand casting, Metalworking industry,Foundry engineering, Sand casting, Investment casting
Paper type General review
Abbreviations
3DP Three dimensional printingABS Acrylonitrile-butadiene-styreneAM Additive manufacturingBPM Ballistic Particle manufacturingCAD Computer-aided designDMLS Direct metal laser sinteringDSPC Direct shell production castingEARP European action on rapid prototypingEOS Electro optical systemFDM Fused deposition modellingIC Investment castingIT International toleranceLENS Laser engineered net shapingLOM Laminated object manufacturingMMII Model maker IIMSFC Marshal Space Flight CenterPS PolystyreneRC Rapid castingRCT Rapid casting technique
RIC Rapid investment castingRP&T Rapid prototyping and toolingRTV Room temperature vulcanizingSL StereolithographySLS Selective laser sinteringZCorp ZCorporation
1. Introduction
After nearly 20 years of research, development and use, the
additive manufacturing (AM) industry continues to grow with
the addition of new technologies, methods and applications
(Wohlers, 2007). In the early development of AM
technologies, the emphasis was directed towards the
creation of “touch-and-feel” models to support the design
(Chua et al., 1998). But, because of frequent changing
requirements of manufacturing industry due to short product
life cycles, fickle consumer demands, complex shaped
designs, higher quality, reducing the cost and time to
The current issue and full text archive of this journal is available at
www.emeraldinsight.com/1355-2546.htm
Rapid Prototyping Journal
17/5 (2011) 328–350
q Emerald Group Publishing Limited [ISSN 1355-2546]
[DOI 10.1108/13552541111156469]
The authors are thankful from the core of their hearts to Avi Cohen(Head of Medical Solutions Objet Geometries LTD), Joe Hiemenz(Stratasys, Inc.) and Ellen J. Kehoe (Senior Editor, Publications SME) forgranting permissions to use figures from their sources. The authors aregrateful to Management, Director General Prof. R. Yadav and HOD MEProf. Vineet Tirth of Moradabad Institute of Technology, Moradabad formotivation and moral support.
Received: 6 December 2009Revised: 17 February 2010, 26 June 2010, 6 September 2010,4 November 2010Accepted: 7 November 2010
328
market for new product and shorter product development
times, industry has been searching solutions for fabricating
direct metal parts since the earliest day of AM. Presently,direct metal fabrication AM technologies (also called as rapid
manufacturing) are used in a wide variety of industries, from
automotive and aerospace to electronics and dentistry(Wohlers, 2006). There are only few AM techniques
available which can manufacture metal parts directly, but
they are just the tip of the iceberg.Although, direct manufacturing of metal parts with AM is not
well developed, indirect methods have been found and shownfeasible through the combination of AM and traditional metal
casting (Detlef et al., 1999). The application of AM in metal
casting process to produce metal cast parts is regarded as rapidcasting (RC). The most important part for any casting process is
to design and produce pattern for the production of moulds intowhich to cast metal. Further, for some casting processes
(like sand casting), designing and preparation of core boxes and
gating system upon which the overall quality of casting dependsare most time consuming and costly process especially in case of
complex design castings. The use of AM technologies in the
creation of casting patterns allows a foundry to manufacture ametal part without the use of tooling for small quantities
(Rosochowski and Matuszak, 2000). In particular, patterns,
cores and cavities for metal casting can be obtained through RC(Wang et al., 1999; Bernard et al., 2003; Chua et al., 2005). The
relevance of RC techniques consists, above all, in a short timefor part availability. Traditionally, in order to produce cast
prototypes, a model and eventual cores have to be created
involving time and costs that hardly match the rules ofcompetitive market (Bassoli et al., 2007). Now, it is possible to
fabricate a complex pattern and other tooling required for
casting in a matter of hours and provide a casting in a matter ofdays.
The art of foundry is ancient, dating back to the dawn ofcivilization. It is a revolutionary change in manufacturing
industry that one of the oldest metal manufacturing
techniques, which dates back to 4000-6000 BC, is beingused with one of the most modern technology-rapid
prototyping. The first use of AM-fabricated patterns as
sacrificial patterns in traditional investment casting (IC)started in 1989 (Greenbaum and Khan, 1993). Since then all
major AM techniques have been used in different castingmethods to provide RC solution for producing metal parts.
The aim of this paper is to present valuable information
about the application of AM in investment and sand castingtechnology. A little step has been taken to collect and review
the information available about commercialised RC solutions
invented by various researchers and technocrats in order toprovide information and implementation of concurrent
engineering approach in producing prototype, pre-series andfor customized production metal casting to manufacturing
industry. In order to explain how RC solutions may be
successfully used in foundry applications, a few examples andcase studies have also been included. A list of various major
commercialised RC solutions based on different AM
processes and their suppliers is presented in Table I.
2. AM applications in IC
IC is a precision casting process which employs wax pattern assacrificial pattern to produce solid-metal parts. These
sacrificial patterns are used to create a ceramic mould by
investing refractory ceramic coatings on the patterns. Oncompletion of the coating, the expandable wax patterns areremoved at about 1408C and 200 KPa in a steam autoclave(Groover, 1996). The mould is further hardened by heating,the procedure called “firing”, and the molten metal is thenpoured while it is still hot. When the casting is solidified, themould is broken and the casting taken out during theknockout process (Jain, 2009). IC produces high quality andgeometrically complex near net shaped metal parts with tighttolerances economically in case of mass production. Theeconomic benefits of IC are limited to mass production.
Limitations of traditional IC:. Traditional IC requires the production of metal tooling for
the injection of wax material to produce sacrificial patternswhich leads to cost justification problems for prototyping,pre-series, customized and single casting and small andmedium quantity production.
. Major part of the total lead time is consumed inproduction of metal tooling required for wax patterngeneration.
. Before committing to manufacturing, numbers of designiterations are performed by tool makers by evaluatingdifferent mould design which further incorporate anadditional cost and lead time (Beaman et al., 1997).
2.1 Rapid investment casting (RIC)
The term RIC represents the employment of RP&T techniquesin IC (Cheah et al., 2005). The cost involved in designing andfabrication of metal tooling for wax injection process can beovercome by using AM techniques to fabricate sacrificialpatterns for IC. AM also facilitates to reduce the overall leadtime involved in production of prototype casting with excellentquality. By employing AM-fabricated patterns to produce theprototypes, there is no need to commit to production tooling forsingle part or small quantity production (Chua et al., 2005). AMtechniques provide various cost effective solutions by which pre-series casting can be produced very economically. Presently,almost all commercialised AM techniques have been employedto produce IC patterns with varying success and many RCsolutions in IC are being used by various industries andresearchers.The use ofAM in IC is in three basic forms.Figure 1shows the three basic approaches used as RC solutions in RIC.
3. Direct fabrication of IC sacrificial patterns(approach1)
AM techniques have been employed to produce direct ICsacrificial patterns in wax and non-wax forms for producinginvestment cast parts.
Direct wax IC patterns
The selective laser sintering (SLS), Fused depositionmodelling (FDM), stereolithography (SL) and model makerII (MMII) systems have been found capable of producing waxpatterns, which can be used directly in IC (Dickens et al.,1995; Chua et al., 2005). The main problem of using directwax patterns is the brittleness of waxes and due to that thereare chances of damaging of these patterns while transportthem to foundry. These are also not recommended for thinwall castings.
Direct non-wax IC patterns
The non-wax patterns are having strength, durability andtoughness by which these can be used to produce thin
Rapid casting solutions: a review
Munish Chhabra and Rupinder Singh
Rapid Prototyping Journal
Volume 17 · Number 5 · 2011 · 328–350
329
wall castings. Non-wax patterns also allow finishing operations
for improving the surface quality of patterns which further
improve the surface quality of final casting. The problem of
ceramic shell cracking and two other main problems related to
incomplete pattern burning out and residual ash have been
observed and reported by various researchers during the use of
non-wax patterns for IC. Case study 1 explains the project
performed by tooling and casting subgroup of the European
action on rapid prototyping (EARP) to investigate the
problems associated with using AM sacrificial wax and non-
wax patterns for IC. Introduction and practical application of
major commercial RIC solutions based on direct fabrication of
IC patterns are presented in following sections.
3.1 RIC using FDM technique
The Stratasysw FDM-AM system offers a different approach
as compared to traditional IC method practiced by thousands
of IC foundries across the world. This AM technique is used
Table I Commercialised RC solutions & their application in metal casting
AM process Manufacturer RC solution and their applications in metal casting
Stereolithography (STL) 3D systems Quick Cast 1.0, Quick Cast 1.1 and QuickCast 2.0 patterns for IC
Epoxy patterns for sand casting and soft tooling
OPTOFOTM patterns for sand casting
EOS EOS-stereolithography (acrylate resin) patterns for IC
Selective laser sintering (SLS) DTM Corp.
(presently 3DSystems)
Investment casting wax, polycarbonate and TrueForm pattern for IC
Rapid tool for direct fabricating moulds for IC
TrueForm, composite nylon, polycarbonate for sand casting and soft tooling
CastForme PS patterns for IC
CRP Tech WindFormwPS patterns for IC
EOS EOSINT-S laser sintering AM to produce sand casting moulds and cores
directly from CAD solid model using polymer coated green sand
EOSINT – P IC patterns fabricating using polystyrene material
Fused deposition modelling (FDM) Stratasys Wax & ABS patterns for IC
ABS patterns and core boxes for sand casting
Laminated object manufacturing (LOM) Helisys
(Currently Cubic Tech.)
Laminated paper master patterns for sand casting and IC
Drop-on-powder deposition inkjet
printing technology(3DP)
Soligen DSPC for ceramic investment casting mould fabricated directly from CAD
solid model
ExOne ProMetal RCT to produce sand casting moulds and cores directly form CAD
files
ZCorporation Starch patterns for IC
Plaster based material patterns for sand casting
ZCaste direct metal casting process for sand casting
Drop-on-drop deposition inkjet printing technology Objet PolyJete for photopolymer resin patterns for sand casting
3D systems Thermojet for producing wax patterns directly for IC
Solidscape
(Sanders prototype)
MM II pattern for IC
Solid ground curing Cubital Wax patterns for IC
Ballistic particle manufacturing BPM Wax pattern for IC
Figure 1 Approaches used as rapid casting solutions in rapid investment casting
Rapid investment casting
RP-fabricated mouldsfor wax injection
(approach2)
Wax patterns Non wax patterns
RP-fabricated ICsacrificial patterns
(approach1)
Direct fabrication ofceramic IC shell moulds
(approach3)
Direct toolingIndirect tooling
Rapid casting solutions: a review
Munish Chhabra and Rupinder Singh
Rapid Prototyping Journal
Volume 17 · Number 5 · 2011 · 328–350
330
to create pattern directly from either acrylonitrile-butadiene-
styrene (ABS) or wax materials. Both wax and ABS patterns
constructed from the FDM process have proven to be suitable
for burn out from the ceramic shell with minimal modification
to the standard foundry processes (Grimm, 2003). The parts
produced by FDM-ABS have a much higher surface
definition than those produced in wax, owing to the good
powdering characteristics of the ABS, which allows final
surface finishing to be carried out[1]. The key strength of
employing FDM-fabricated pattern over MMII-fabricated
patterns includes short-built time for the process to build a
part. For the build of the benchmark model, MMII process
took more than 80 hours while the FDM process took only
16 hours (Chua et al., 2005). The use of this RIC solution is
presented as a case study in Section 3.1.1.
3.1.1 Case study: RIC using direct FDM-ABS patternsGouldsen and Blake (1998) reported the results of a program
in which six foundries had participated to evaluate the use of
ABS parts created from FDM-AM system as a substitute for
the injected wax patterns in RIC. In IC with this approach, wax
gates and vents are attached to the ABS pattern by the foundry.
The ceramic slurry is then invested on the pattern to make
ceramic shell similar to traditional IC process. Now the major
difference in this approach is that the shell is placed into a flash
fire furnace where temperatures reach upward of 1,0938C and
the pattern combusts, giving off gas possibly leaving a small
amount of ash in the hollow shell mould. The gates and vents
allow gas to escape the mould during burn out and allow
molten metal to be poured into the mould. An autoclave may
not be used, because the ABS thermoplastic does not melt at
those relatively low temperatures (approximately 3508C)
(Jain, 2009). The shells are removed from the furnace and
inspected for cracks and residual ash. If any ash remains, it is
removed by rinsing or high-pressure air. From this point on,
apart from having to reheat the moulds, there is no difference
in the process than if wax were being used.Based on the results demonstrated by all participated
foundries, the authors claimed that the patterns built from
FDM-ABS offer a number of quality advantages over patterns
made by other AM processes, namely, clean burn-out,
robustness, the ability to be handled without damage,
dimensional stability and ease of pattern preparation. One
major disadvantage with this approach is that the surface layer
and built style produces a very rough surface condition. So,
surface finish preparation of the pattern is important to
achieve the best results.Example: Hydro Quebec, an electrical power company in
Canada has been producing IC since 1997. Figure 2 shows a
set of six FDM-ABS patterns that were cast in aluminium at
Shellcast in Montreal, Canada.
3.2 RIC using MMII technique
Solidscape’s MMII system based on drop-on-drop deposition
inkjet printing technology uses two drop-on-demand inkjets to
build patterns. One inkjet is used for build material
(thermoplastic) and the other is for support material (wax).
The supports are removed by washing it away with an ATOS
solvent (Chua et al., 2005). The important feature of MMII is
that it is the highest resolution additive process having capability
to build fine castings from wax patterns using 0.0125 mm thick
layers (Wohlers, 1995a). Each layer is milled resulting in very
precise models that are especially well suited for the precision
casting of precision parts (Gebhardt, 2003). The feasibility ofemploying MMII system to fabricate sacrificial IC patterns byusing direct and indirect tooling approach is presented as casestudy in Sections 3.2.1 and 4.2, respectively.
3.2.1 Case study: RIC using MMII fabricated patternsThe feasibility of employing patterns fabricated by MMII assacrificial IC patterns to produce metal casting was studied byChua et al. (2005). The build material “protoform” is used inMMII system having the properties similar to those of thefoundry wax material. Researchers investigated two castingsolutions by using MMII-AM system. The first is by usingMMII fabricated pattern directly as sacrificial IC pattern(approach1) and second solution is an indirect tooling(approach2) involving the utilization of room temperaturevulcanizing (RTV) silicon rubber moulding with an MMII-fabricated master pattern to produce sacrificial IC-wax pattern.The researchers claimed better accuracy by employing MMII-fabricated patterns over FDM-fabricated patterns.
In the direct method, the MMII-fabricated pattern wasdirectly used as a sacrificial pattern in IC. Researchersinvestigated this approach to produce aluminium alloy IC andclaimed that:. The microstructure of MMII part was built more densely
as compared to FDM or SLS.. There was no porous structure in MMII part and no
sealing or coating was needed on the MMII part surface.. The pattern produced in this approach melted off at
relatively low temperatures with little or no residual ashleft (due to similarity between material characteristics ofMMII patterns and foundry wax).
. No sign of shell mould cracking was observed during theIC process.
. By using direct approach, there is a significant amount oftime saving and cost saving can be achieved as comparedto the conventional metal tooling method for patternproduction.
. This approach will be economical when only three to fivemodels are required and component having complicateddesign.
3.3 RIC using QuickCast 1.0 technique
A problem of ceramic shell cracking has been reported byvarious researchers while using non-wax AM patterns in IC.One example is use of SL’s acrylic patterns, which expandduring burn-out process and crack the ceramic shell duringIC. The latest method is the 3D system’s QuickCast buildstyle (consisted of triangular geometry), which eliminates95 per cent of the internal mass of a part made of epoxy resin(Rosochowski and Matuszak, 2000). The concept ofQuickCast is based on the fact that hollow structures wouldsoften at lower temperatures and collapse inwards upon itselfbefore critical stress levels are developed (Jacobs, 1993). Theidea of QuickCast is to build the pattern such that it collapsesinwards under the influence of heat, rather than expandingoutwards and cracking the ceramic shell (Yao and Leu, 1999).Using QuickCast, users can produce patterns for metalcastings in a fraction of time (Wohlers, 1995b). Aluminium,titanium, stainless steel, tool steel and copper alloys have allbeen cast successfully using IC with QuickCast patterns atFord (McMains, 1995) and QuickCast has also successfullyapplied for building tooling required for production of plasticparts, casting patterns, dies and other tooling item in Fordmotor company (Denton, 1994).
Rapid casting solutions: a review
Munish Chhabra and Rupinder Singh
Rapid Prototyping Journal
Volume 17 · Number 5 · 2011 · 328–350
331
3.3.1 Case study: project of EARPEARP has carried out a project to find out the problemsassociated with using AM models as sacrificial pattern for IC by
accessing the accuracy and surface finish of the models andcastings (Dickens et al., 1995). Models were manufactured bydifferent AM processes, namely, 3D systems-QuickCast 1.0,
DTM-SLS, Cubital – Solider (waxes from acrylic mould),FDM (wax models), laminated object manufacturing (LOM),
electro optical system (EOS)-SL and three foundries were usedto produce casting from a given set of models. The project wascompleted in three phases: computer-aided design (CAD)
modelling, AM model productions and IC.The CAD modellingwas performed on pro-engineer and a stereolithography (STL)
file supplied to different AM machines to produce models forIC. Some models received surface finishing to smoothing thesurface by abrasive bead blasting.
The most accurate sets of models were produced by 3Dsystems – QuickCast and from DTM Corporation’s SLS
among all AM processes.The greatest variation was observedonSL models. Three foundries were used to produce aluminium
ICs from the model received from different AM processes.
Major findings of the project. Most models did not suffer any damage during
transportation to foundries except those from FDM.. Owing to porous structure of SLS models, researchers
reported that a sealing with thin layer of wax must beemployed to SLS models before investing the shell
material. Figure 3 shows the results of casting producedby using sealed SLS model and not sealed SLS model.
. The great surprise from the results of this project was thelack of accuracy observed in various models. Models fromall the AM processes were much less accurate than
expected. The 3D system’s – QuickCast models weregenerally the most accurate and these models also
produced the most accurate castings.
3.4 RIC using QuickCast 1.1 & QuickCast 2.0
Ashley (1995) reported various problems of using patternsfabricated with QuickCast1.0 in IC. Major problem is theformation of pinholes during the removal of supports from
downward-facing surfaces, which led to the ceramic slurryentering the casting pattern’s interior. QuickCast parts often
exhibited drainage and void-ratio problems, especially in thin-curved sections. Finally, the less-than-optimal 80-per centyield of aerospace industry-acceptable castings attainable with
QuickCast 1.0 was found to be caused primarily by shell
cracking due to solid, incompletely drained patterns with low-
void ratios. To overcome these problems 3D systems
introduced QuickCast 1.1 (Jacob, 1995). This involved the
change in the geometry of build style from triangular to
square. The build style features triple up-facing and down-
facing skins 27 times stronger than they were previously,
which eliminate pinholes and sag which further improve the
surface finish. With these features QuickCast1.1 produced
lower expansion stresses on ceramic IC shells; bringing
casting yields up to 95 per cent. QuickCast 1.1 is being used
to produce castings of unprecedented quality from an AM
pattern (Wohlers, 1995b). The another development in this
process is the development of QuickCast 2.0, which is the
result of the involvement of changing the build style from
square to an “offset” hexagon. QuickCast 2.0 patterns
produce less than one-third the shell stress of QuickCast 1.1
during pattern burnout, significantly reducing the probability
of shell cracking (Hilton and Jacob, 2000).
3.5 RIC using Thermojet technique
Thermojet modeller based on the drop-on-drop deposition
inkjet printing technique (Dimitrov et al., 2008) is the ideal
wax prototyping machine. Using 3D-CAD data files in STL
format, the part to be cast can be programmed for the current
shrink and orientation. This AM technique produces patterns
by additively spraying layers of tiny wax droplets on to a
platform surface, much like an inkjet printer. These wax
patterns are used directly in IC and having ability to be
autoclaved easily. This process has been accepted widely
within the industry owing to the ease of use within the
foundry (Tromans, 2004). Thermojet from 3D systems is
capable of producing parts very quickly, whereas the Model
Maker series from Solidscape produces fine detailed parts,
but is rather slow (Hopkinson, 2002).
3.6 RIC with three dimensional printing (3DP)
technique using Zp14 pattern material
Starch-based Zp14 material is introduced by ZCorp to
produce parts which after infiltration with wax are used
extensively as patterns for IC without using moulds[2]. This
Zp14 material is used to fabricate patterns for IC by printing
on ZCorp’s 3DP machines. Then a ceramic shell is invested
on the pattern using traditional IC method and then
evacuated to obtain the cavity for pouring metal. Figure 4
shows the process stages of producing 3,16l exhaust
manifold of a racing car using this RC solution at
Figure 2 Aluminium investment casting using FDM ABS patterns
(a)Notes: (a) ABS patterns; (b) Al castingsSource: Gouldsen and Blake (1998)
(b)
Rapid casting solutions: a review
Munish Chhabra and Rupinder Singh
Rapid Prototyping Journal
Volume 17 · Number 5 · 2011 · 328–350
332
University of Michigan[3]. Bassoli et al. (2007) has verifiedthe feasibility to produce thin-walled parts and evaluated thedimensional accuracy of the patterns and the parts producedby using this RC solution.
3.6.1 Case study: project of Marshal Space Flight Center (MSFC)(sponsored by NASA)Copper and Wells (2000) have evaluated the capabilities ofvarious AM processes and produced quality test hardwaregrade IC models at MSFC, a sponsored project by NASA,Washington, DC. The IC patterns of a selected propulsionhardware component, a fuel pump housing, were rapidprototyped on several AM processes. Table II shows the AMprocesses with pattern materials used to cast the selectedcomponent for this study. The shelled models were fired andcast with NASA-2, a test hardware material. Researchers havereported after this investigation that each AM processes wereof varying degrees of success and each proved a significantcost advantage over conventional manufacturing techniques.
The major findings of this research. The SLS-TrueForm model provided the most acceptable
casting followed by FDM-wax and SLS pattern built
15 times faster than FDM pattern (four hours verses
65 hours).. The least expensive model was the ZCorp pattern, which
also was the fastest to complete at 3.5 hours, and also one
of the least accurate.. Researchers recommended that the ZCorp patterns will
be more suitable for initial prototype casting, i.e. near-net-
shape castings.
Figure 3 Aluminium casting
(a)
Notes: (a) Using not sealed SLS model; (b) using sealed SLS modelSource: Dickens et al. (1995)
(b)
Figure 4 Investment casting of 316 l exhaust manifold of a racing car using Zp14 IC patterns
(a) (b)
Notes: (a) CAD model; (b) starch pattern; (c) shell moulds; (d) final casting[3]
(c) (d)
Table II AM processes with pattern materials used for MSFC project
S. no. AM process Pattern material
1 SLS Polycarbonate casting pattern material
2 SLS Trueform polyamide
3 FDM IC wax
4 LOM High performance paper
5 3DP (ZCorp) Starch (cellulose)
6 FDM ABS plastic
7 Stereolithography (SL) Epoxy 1570
8 MMII IC resins
Rapid casting solutions: a review
Munish Chhabra and Rupinder Singh
Rapid Prototyping Journal
Volume 17 · Number 5 · 2011 · 328–350
333
3.7 RIC with SLS technique using CastForme
polystyrene pattern material
CastForme (CF) polystyrene (PS) is a polystyrene – basedmaterial developed by DTM Corp. in 1999 to fabricate ICpatterns by using SLS machines (DTM Corporation, 1999).Presently, 3D systems Corp[4] is the supplier of CF material,which acquired DTM in 2001. SLS system using CF materialis one of the fastest and most cost-effective techniques forrapid fabrication of small quantities of wax-like patterns forIC. CF is a low-ash pattern material that produces high-quality castings, even with high-reactive alloy such astitanium[5]. The pattern fabrication using this techniqueinvolves two stages: first the building of green part, and secondits infiltration with wax (Dotchev et al., 2007). The main ideabehind this two-stage process is to fabricate a pattern withproperties very close to those of conventional wax patterns,and therefore, and to be compatible with standard foundrypractices for IC. Post – processes necessary for CF patternsinclude dipping in liquefied wax to seal surface porosity and toincrease pattern strength (Cheah et al., 2005). Dotchev andSoe (2006) analyzed experimentally all stages of CF patternfabrication process and reported that the cleaning and waxinfiltration are the main leading reasons for inferior quality,part distortion and breakage. CRP Technology[6], a divisionof the Cevolini Group, is the first to use CF material forfabrication of IC patterns with DTM-SLS system for RC ofhard to cast shapes of Minardi F1 car components (uprights,suspension supports, clutch box, steering box and gear box)with the titanium alloy (Ti-6Al4V)[7]. With the combinationof SLS and CF formula, CRP saved cost and time to producecomponents having very complicated shapes and geometriesand gained freedom to investment cast parts in the alloy ofchoice (Titanium, Aluminium, Steel alloys or Super alloys)[8].Figure 5 shows the CF disposable pattern fabricated forF1upright titanium RC.
3.8 RIC with SLS technique using Windformw PS
pattern material
Windformw PS is a new PS-based material developed by CRPTechnology to fabricate IC patterns using SLS technique[9].It is particularly suited for the foundry, since the main
applications are fabrication of complex IC patterns and
casting with highly reactive alloys like titanium, in addition totypical cast alloys. Compared to other polystyrene materials
available, Windformw PS has:. improved surface quality and details reproduction; and. very low-ash content suitable for highly reactive alloys,
namely, Ti, Al, Mg, steel and Ni alloys.
4. Fabrication of moulds for producing IC-waxpatterns (approach2)
For producing large quantity of IC-wax sacrificial patterns, itis feasible to employ wax injection mould fabricated byvarious AM techniques. For mould fabrication, further two
approaches, namely, direct tooling and indirect toolingapproaches are used which are further classified as soft and
hard tooling (Chua et al., 1999). In direct tooling approach,the mould fabricated by AM techniques will not use any
intermediate steps. For improving the accuracy, strength andsurface finish of moulds, some post-processing techniques
may be used. In indirect tooling approach, AM fabricatedmaster patterns are employed to create the necessary moulds.
The materials used for fabrication of moulds in indirecttooling are polymers and silicon rubbers, which result in
relatively weaker moulds. Different direct and indirect toolingapproaches for fabrication of moulds for producing IC-wax
patterns have been reported by various researches (Chua et al.,1999; Rosochowski and Matuszak, 2000; Dickens et al., 2000;
Cheah et al., 2005).Direct tooling. In this approach, moulds fabricated on AM
machines are used for fabricating multiple wax patterns (Paland Ravi, 2007). Some pioneering processes such as direct
metal laser sintering (DMLS), Rapid Tool, ProMetal, LENSand DirectAIM have been used successfully for direct
fabrication of moulds for producing wax patterns. Thisapproach is employed in medium to high-volume production
and when reduction in time-to-market the product is majorgoal for manufacturer (Karapatis et al., 1998).
Indirect tooling. This approach involves fabrication of mouldfrom an AM master pattern, which is used for fabricating wax
IC patterns. Silicon rubber tooling (RTV), Epoxy resintooling, Keltool tooling and Spray metal tooling as indirect
approach for mould fabrication have been applied successfullyfor moulding wax patterns (Smith et al., 1996). All of them,
like the best-known called “Silicon rubber tooling (RTV)”, donot relate directly to AM, but are used for fabrication of
moulds by using AM master patterns. In silicon rubbertooling process, the AM master pattern is equipped with
runners put in a frame and covered with silicon rubber. Afterhardening, the solid block of silicon rubber is cut according to
the parting line and the master is removed, leaving therequired cavity. The resulting cavity is cast with wax, which
used as wax pattern in IC. Figure 6 shows the steps involvedin fabrication of IC-wax pattern using silicon rubber tooling.
Practical application of indirect tooling for mould fabricationusing FDM-ABS and MMII master patterns are presented in
Sections 4.1 and 4.2, respectively.
4.1 Case study: RIC using FDM-ABS pattern and wax
pattern moulded through RTV moulds, moulded by
FDM ABS master pattern
Lee et al. (2004) investigated the feasibility of employing
FDM process to built sacrificial IC patterns (using direct
Figure 5 CF disposable pattern (laser sintering and red wax infiltration)fabricated for F1Upright Titanium rapid casting
Rapid casting solutions: a review
Munish Chhabra and Rupinder Singh
Rapid Prototyping Journal
Volume 17 · Number 5 · 2011 · 328–350
334
and indirect approach) by using ABS material to produce metal
casting rapidly. Researchers investigated and compared the
FDM system, FDM3000 for creating direct sacrificial IC
pattern in ABS material and by producing injected wax pattern
via silicon rubber moulding (indirect tooling approach). The
study showed substantial advantages when employing ABS
models as direct IC patterns or as master patterns for producing
silicon rubber moulds to cast wax IC patterns in terms of cost
and time savings, relatively accurate final castings with
reasonable surface quality and the complete elimination of
hard tooling required in conventional IC process. The
researchers claimed that it is much more beneficial for
foundries to employ FDM-ABS-fabricated patterns in IC for
single or small quantity production of castings (,5) and to
employ the indirect approach of fabricating IC patterns via
silicon rubber moulding for medium quantity (tens of casting)
production.
4.2 Case study: RIC using wax pattern moulded through
RTV moulds fabricated with MMII master pattern
In this approach, researchers have employed an MMII-
fabricated master pattern to create RTV silicon rubber mould
(Chua et al., 2005). From the rubber mould, wax patterns
were cast and used as sacrificial pattern in IC. Researchers
claimed that this approach will be more economical to
fabricate a silicon rubber mould with MMII fabricated master
pattern and produce wax pattern from the silicon rubber
mould for IC when several tens of models are required.
5. Direct fabrication of ceramic IC shell(approach3)
This RC technique fabricates the ceramic mould (negative)
with integral cores directly from the CAD model for the IC of
metals. This technique provides a greater advantage over
traditional IC method and other RIC techniques by removing
the steps of wax pattern generation, ceramic shell production,
autoclaving and firing of mould. An introduction of
commercialised RC solution “Direct shell production
casting (DSPC)” based on this approach is given in
Section 5.1. The major advantages of this technique are:. Reduction in cost and lead time (in traditional method,
making of metal dies for production of wax pattern are
typically expensive and time consuming, with lead time
ranging from two to six months).. Less risk of damaging of shells during transportation by
preserving dimensional tolerances.
. No risk of core shifting in casting of complex shapes that
require core inserts, because shell and core are fabricated
as a single structure.. Furthermore, cores can be made hollow, leaving less
material to be leached out.. It is possible to adjust the ceramic shell thickness during
fabrication, which further helps to control the rate of heat
transfer from the casting.
5.1 Direct shell production casting
Soligen Technology Inc. (Northridge, CA) is one of the
licensees of 3DP AM technology developed at the MIT
(Cambridge, MA) and produced DSPC system in 1993[10].
By using 3DP AM technique, this system directly fabricates
the ceramic moulds (negative) with integral cores for IC of
metals. This eliminates the need for wax patterns and tooling
for cast metal parts (Wohlers, 1992). The DSPC process
utilizes the bonding approach and requires post processing
(Carrion, 1997). In this process, alumina (refractory)
powders are held together through the spraying of colloidalsilica binder with multi-jet print head. The unbound powder
is removed and the resulting shell is fired to create a rigid
ceramic mould prior to pouring the molten metal of any
castable alloy. DSPC can be used to produce parts of virtually
any shape. Diverse metals, including copper, bronze,
aluminium, cobalt chrome, stainless steel and tooling steel,
have been successfully cast in the ceramic shells produced by
this process. Metal parts can generally be produced in two to
three days (McMains, 1995). Sachs et al. (1991) reported the
use of DSPC-fabricated ceramic shells for production of
nickel super alloy casting. DSPC is used for fabrication of
prototype and small quantity of fully functional castings.Figure 7 shows a metal casting of an automotive component
produced by using DSPC process. Figure 8 shows the
orthopedic knee casting using ceramic mould made by 3DP.
6. AM applications in sand casting
Sand casting is the most widely used casting process inmanufacturing industry in which components are cast by
pouring liquid metal into the cavity of sand mould. Among
the sand casting processes, moulding is most often done with
green sand, which is a mixture of sand grains, clay, water and
other materials, which can be used for moulding and casting
processes (Heine et al., 1997). The detailed process sequence
for sand casting is shown in Figure 9 (Groover, 1996). The
basic steps involved in sand casting processes are:
Figure 6 Steps involved in fabrication of IC-wax pattern using silicon rubber tooling
(a) (b)
Notes: (a) CAD model; (b) SLA fabricated master pattern; (c) RTV mould; (d) Wax pattern for ICSource: Pal and Ravi (2007)
(c) (d)
Rapid casting solutions: a review
Munish Chhabra and Rupinder Singh
Rapid Prototyping Journal
Volume 17 · Number 5 · 2011 · 328–350
335
. preparation of the pattern;
. making the mould (ramming of sand around the pattern,
gating system for the entry of the molten metal);. core making and core setting in mould;. closing and weighting; and. pouring liquid metal into the cavity;
6.1 Rapid sand casting
Traditionally, for sand casting process, skilled workers used to
fabricate patterns and core boxes by taking design data either
from 2D drawings or from hand crafted prototypes of clay,
wood, plastic or other materials. This time consuming process
can now be performed by using a number of different AM
processes. This approach may also be referred to as rapid sand
casting process because by using AM techniques, patterns,
cores and gating system can be fabricated in a relatively short
period of time. The use of AM process has proved to be a cost
effective and time efficient approach for producing pattern,
core boxes and gating system for sand casting (Wang et al.,1999). AM helps to fabricate pattern with added cores by
disregarding internal cavities and designing core prints. LOM
is fairly popular for this application, since LOM moulds have
the feelings and look of wood, which is a traditional foundry
tooling material (Rosochwski and Matuszak, 2000). Pak and
Klosterman (1997) have documented the use of LOM AM
process to fabricate the tooling required for sand casting.
Pereira et al. (2008) have reported the advantages gained with
the application of FDM patterns in sand moulding. Many
commercialized AM techniques have been employed to
produce tooling required for sand casting with varying
success and many RC solutions in sand casting are
being used by various industries and researchers as shown
in Table I.There are mainly three approaches by which application of
AM techniques can be used in sand casting technology
(Kouznetsov, 2004). Figure 10 shows the basic approaches
used as RC solutions in rapid sand casting. By using direct
tooling approach, AM generated objects can be utilized
directly as patterns in sand moulding in case of small or
medium volume casting production as a substitution for
traditionally employed wooden patterns. The objects
fabricated by almost all AM techniques can be used as
patterns. Indirect tooling approach in sand casting can be
efficiently employed in case of large-volume production and
when great durability of pattern is required. The most
common approach is the use of AM generated model as
pattern for moulding RTV and the pouring urethane into the
mould. The resulting plastic part can be used as a pattern for
sand moulding. Third and latest approach is the use of AM
technique to direct fabrication of sand moulds (pattern less
moulds). EOS DirectCastw, ProMetal rapid casting
Figure 8 Orthopedic knee casting made of medical cobalt chrome alloyby using ceramic mold made by 3D printing[11]
Figure 9 Process sequence for sand casting
Fabricatecore boxes
Fabricatepattern
Moldcore
Preparesand
Meltingmetal
Source: Groover (1996)
Buildmold
Pourcasting
Sand
Rawmetal
Corematerial
Break outraw casting
Solidificationand cooling
Finishedcasting
degate andclean
inspection
Figure 7 Intake manifold casting produced by using DSPC[10]
Rapid casting solutions: a review
Munish Chhabra and Rupinder Singh
Rapid Prototyping Journal
Volume 17 · Number 5 · 2011 · 328–350
336
technology (RCT), and ZCast501 processes have been usedsuccessfully for direct fabrication of moulds in casting
industry.Based on these approaches, introduction of major
commercially used rapid sand casting solutions and somecase studies and examples related to them are presented in the
next sections.
7. Fabrication of sand casting patterns usingdirect tooling approach
7.1 Rapid sand casting using LOM technique
LOM is an AM process developed by Helisys Inc. (USA) and
currently, Cubic Technologies, successor to Helisys Inc., isthe exclusive manufacturer of the LOM-AM machines
(Chua et al., 2003) in which a part is built sequentiallyfrom layers of paper, plastic, metal or composite sheets, allcoated with a thermally activated adhesive (Chua, 1994;
McMains, 1995; Upcraft and Fletcher, 2003). The slices ofmaterial sheets are cut in required shape from roll of material
by using laser beam. The cutting material sheet is laid onmachine platform and bonded to the previous sheet using a
hot roller, which activates a heat sensitive adhesive. Afteraddition of all sheets, the solid part of the material is removed
from the platform. Surrounding material and material inregions of the part that are hollow must be removed in a
“Decubing” post processing step (Wang et al., 1999). LOM isallegedly five to ten times faster than other AM processes,because the laser beam need only trace the outline of each
cross section, not the entire area (Chua, 1994). LOMtechnique is widely used in fabrication of patterns for both
sand casting and IC. Castings produced by LOM patternswere found to be well within the acceptable quality range and
gave 25 per cent cost saving (Mueller and Kochen, 1999).LOM is fairly popular for sand casting, since LOM models
have the feeling and look of wood, which is a traditionalfoundry tooling material. The paper patterns of the LOMprocess also work well with IC. The paper can be burnt out
with little expansion, however, the ash residue may besubstantial (Rosochwski and Matuszak, 2000). A case study
proving time and cost savings in sand casting using LOMtechnique is presented below in Section 7.1.
7.1.1 Case studyWang et al. (1999) have investigated experimentally the specific
considerations that are relevant to using the LOM AM processto fabricate patterns and core boxes for sand casting. Authors
have also proposed that to make high-quality patterns and coreboxes for sandcasting using the LOM process, several importantissues must be considered, such as compatibility of the part
geometry, error source generation and propagation, shrinkage
considerations, and deterioration due to environmental effects
and repeated use. The process flow for fabricating the sand
casting tooling using LOM process is shown in Figure 11. The
time and cost saving in fabricating a part by using this approach
has been presented as an example given below.
Example: casting of ballistic projectile by using LOMtechnique. Authors of this investigation have also reported an
example of casting of 25 mm ballistic projectile by using LOM-
AM technique, which was provided by Lufkin Industries, Inc. of
Lufkin, TX. The CAD design of part, match plate, pattern and
core box shown in Figure 12. The final LOM pattern and core
box together with cores and sand cast part are shown in
Figure 13. Technical tooling details are given below:. part envelope dimensions (mm): 83.68 £ 27.94 £ 27.94;. match plate dimensions (mm): 431.80 £ 304.80 £ 76.20;. core box dimensions (mm): 203.20 £ 127 £ 44.45;. LOM machine: LOM 2030;. LOM paper thickness: 0.09 mm double layered;. finish material: sanding lacquer sealer and lacquer spray;
and. application: sand casting of ductile iron.
The authors have reported a 50 per cent saving in time and
cost compared to aluminium tooling by using LOM AM
technique in sand casting. Part geometry of thin wall may not
be suitable for LOM-based rapid tooling. The authors have
also mentioned that the LOM process introduces a variety of
errors into the pattern and core-box fabrication process,
which should be carefully understood and controlled to
ensure the realization of time and cost saving.
7.2 Rapid sand casting using OPTOFORM technology
SMC Colombier Fontain Company has carried out a study
based on tooling manufacturing with a new AM process in order
to reduce “time – to – market” and the cost of the product
development in the sand casting process (Bernard et al., 2003).
The study was based on tooling manufacture by integrating
CAD softwares and a new AM process “OPTOFORM” which
is a paste polymerization process. Part designing, assembly,
filling of molten metal and the solidification simulation was
done with the CAD software to validate the sand mould. The
pattern plates and core boxes were designed with the cluster
modelling. Master patterns were manufactured with a new
rapid tooling process, which was introduced by OPTOFORM
in 1998 and which was purchased by 3D systems in 2001.This process, close to SL, brings into play material
exploitable in paste form, which allows a large-application
range. Indeed, the resin paste permits a high level of
additional material, which increases the mechanical
properties. The paste is set down into thin layers with
Figure 10 Approaches used as RC solutions in rapid sand casting
Rapid sand casting
AM-fabricated patternand core boxes
(direct tooling approach)
AM-fabricated patternand core boxes
(indirect tooling approach)
Direct fabricationof shell moulds
(Pattern less mould)
Rapid casting solutions: a review
Munish Chhabra and Rupinder Singh
Rapid Prototyping Journal
Volume 17 · Number 5 · 2011 · 328–350
337
specific scrapers, and then solidified by a laser. This process
also uses a ceramic paste to obtain parts and cores. In this
research, ceramic component and tools and alumina and
metallic parts were manufactured for the validation of the
process. A total of 500 moulds were produced and the results
were very good. The OPTOFORM process for sand casting
was validated without any problem with the small production.Researches claimed that there was 20 per cent improvement
in average time of all the operations that composed the
industrialization with the numerical channel (integration of
CAD and AM) then with the traditional techniques. But the
overall development costs were about 15 per cent more with
the numerical channel than with the traditional techniques.
This problem was due to the difficulty to realize the complex
moulding study with the CAD tools (CATIA, Pro-engineer,
etc.). SMC solved this problem by using the new user-friendly
CAD software – SolidWorks. It introduced a new outlook
on the CAD. For the parts without core, it highlights
the reduction of the design costs owing to a difference ofabout 20 per cent cheaper with the numerical channel
(AM and SolidWorks) than with the traditional techniques.By the achievements of this study, SMC has introduced a
new AM technology to manufacture the production tooling
for the sand casting process. The result proved the importancein simulation reliability due to good metallurgical results, in
spite of wall thickness reduction (to 4 mm) under the process
limits. The successful introduction of SolidWorks reduced the
part design time and CAD hourly rate. Since then, all the new
products have been designed and industrialized using the
numerical chain and design methodology in SMC.
7.3 Rapid sand casting using PolyJete technology
Objet’s patented PolyJete technology based on 3DP system
provide high resolution RC solution to sand casting process.The process provides a complete 3DP solution for virtually
any sand casting application by using Objet FullCurew
material (photopolymer resin) and Objet software (Cohen,
2008). The concept is based on the use of photopolymers as
building materials. A wide area inkjet head layer wise deposits
both build and support material. It subsequently completely
cures each layer after it is deposited with a UV flood lamp
mounted on the print head. The support material, which is
also a photopolymer, is removed by washing it away in asecondary operation (Dimitrov et al., 2008). Sand casting
facilities use Objet’s PolyJete technology to create mould
patterns (solid and split) as they offer high-resolution printing
and utilize materials that fit the requirements of this
application niche. Both solid and split patterns can have
cores inserted to complete the final part shape[12].
The Figure 14 shows the rapid sand casting of brass
component with PolyJete technology.
8. Direct fabrication of sand moulds (pattern lessmoulds)
8.1 Rapid sand casting using EOSINT-SLS machine
EOS GmbH, Munich, Germany have been marketed
EOSINT-S Laser Sintering AM machine in which sand
Figure 11 Process flow for fabricating the sand casting tooling using LOM
2D drawing ofpattern and core box
CAD solid model ofpattern and core box
Conversion of CADmodel in to. stl format
Fabrication onLOM machine
Post processing (decubing,smooth and seal)
Traditional sandcasting process
Finalcasting
Figure 12 The CAD design of part, match plate, pattern and core box
Source: Wang et al. (1999)
Figure 13 Final LOM pattern and core box together with cores andsand cast part
Source: Wang et al. (1999)
Rapid casting solutions: a review
Munish Chhabra and Rupinder Singh
Rapid Prototyping Journal
Volume 17 · Number 5 · 2011 · 328–350
338
casting moulds and cores fabricated directly from CAD solid
model using polymer-coated green sand[13]. The process is
based on the powder-based laser fusion process. Lightman
(1997) reported that this machine is a modification of EOS’
standard sintering machines, in which coated refractory sand
is used as the powder. Sand moulds and cores are produced
by using a CO2 laser that causes the sand particles to adhere
by heating and binding their coating. Moulds for complex
parts can be built quickly, and castings can be made directly
into the sand mould (Figure 15). EOS has named the process
DirectCastw (Freitag et al., 2003) which has been allowed
patent status in the USA in 2000[14]. Presently, EOS
producing two laser sintering machines such as EOSINT
S700 and EOSINT S 750, which use dual lasers to fabricate
complex moulds and cores using foundry sands EOSINT
Zircon HT and EOSINT Quartz 4.2/5.7 (Chua et al., 2003).
8.2 ProMetal RCT
ExOne (formerly Extrude Hone Corporation) has offered
three commercial 3DP machines R10, SR-2 and RCT S15
based on 3DP technique in 2005, which are used to perform
two processes, namely, ProMetal Direct Metal Printing and
ProMetal Rapid Casting [15]. Using the 3DP technology,
RCT S15 and RCT S-Max produce complex sand casting
moulds and cores directly from a CAD model without using
any physical pattern or core box. RCT tends to cast
geometrically complex shapes which are often impossible to
create by conventional means. A layer of sand (bonded with
furan resin) mixed with the hardener is spread evenly on a
machine build platform and a binding agent is then applied
using print heads at the specified areas determined by the
CAD data. The hardening agent contained in the sand
hardens the binder and creates the objects one layer at a time
from top to bottom[16]. The sand moulds and cores
fabricated with this process are poured immediately without
using secondary operation. Figure 16 shows the mould of
automotive intake manifold manufactured by this process and
the final casting. The key advantage of this RC solution is that
it provides flexibility to produce complex and pattern less
castings. Multiple and unique moulds can be produced at the
same time while reducing production costs and time to
market. Table III provides the information regarding material
being cast with these processes and their application areas.
RCT process can be used to produce prototype castings
economically and to validate mould designs. In certain
applications, it could be used to eliminate core boxes or to
produce especially intricate cores.RCT S15 is a factory-floor solution which provides
everything necessary to produce casting moulds and cores
directly form CAD files. This system includes a process
station, unloading station and a mixing unit that prepares and
stages sand for use during the process. The S15 system by
using 512 jets provides the maximum size of mould up to
1,500 £ 750 £ 700 mm and is the only system using foundry
grade materials (Wohlers, 2003). ProMetal RCT S-Max
machine is also in the market for the manufacturing of most
complex moulds and core with larger build size of
1,800 £ 1,000 £ 700 mm[17].
8.2.1 Example: use of ProMetal RCT for DiMora’s1,200 HPengine components of world’s most expensive vehicle, the NataliaSLS 2Car-designer Alfer J. DiMora has emphasized through an
article in 2007, the importance of using the RCT methods for
technically advanced engines[18]. He stated that the extreme
complexity of the 16-cylinder DiMora Volcano engine
requires the flexibility and precision that only RCT can
provide. Advanced Technology & Design Inc. president
Clifford Sands added in the same article that:
By removing the constraints of hard tooling, RCT allows extreme enginedesign to become a reality. At 14 liters displacement and producing1,200HP, the proprietary DiMora Volcano V16 is an extreme engine design.We take DiMora’s CAD data file and design the sand mould assembly whichwill be used to create this cutting-edge engine.
Figure 14 (a) 3D model printed using PolyJete technology; (b) sand casting mould; (c) the pattern is removed from the mould; and (d) final casting ofbrass component
(a) (b)
Source: Cohen (2008)
(c) (d)
Figure 15 Sand mould, sand positive, and aluminium casting producedwithin one day by using EOSINT-S laser sintering
Source: Lightman (1997)
Rapid casting solutions: a review
Munish Chhabra and Rupinder Singh
Rapid Prototyping Journal
Volume 17 · Number 5 · 2011 · 328–350
339
8.3 ZCast 501 direct metal casting
ZCast501 Direct Metal Casting is an RC solution developed
by ZCorp for sand casting of non-ferrous materials[19].
Conventionally, metal castings are produced by using sand
casting tooling, techniques and procedures as mentioned in
chart 2. Instead of utilizing this costly and time-consuming
process, the ZCast process creates the shell moulds directly
from CAD data by using 3DP-AM technology. It eliminates
the pattern creation phase of the traditional sand casting
process in a revolutionary way, resulting in a drastic reduction
of the casting lead time from weeks to days (Krouth, 2002).
ZCast provides three basic methods to fabricate moulds to
produce casting rapidly. Bak (2003) reported that the
accuracy and surface finish are consistent with sand casting
by using ZCast process. Singh (2010) reviewed the use of this
RC solution for generating prototype castings.Material. ZCast 501 powder is a plaster-ceramic composite
suitable for non-ferrous materials. Various manufacturers and
researches have been produced successful castings in
aluminium, zinc, bronze, magnesium and lead. Zb56 binder
solution and Zc5 cleaning solution is commonly used for
making moulds.
Major features:. ZCast501 mould is recommended for non-ferrous metals
with pouring temperature below 1,1008C.. The recommended shell mould wall thickness range is
minimum 13 mm and maximum 25.4 mm[20].. Before pouring, ZCast moulds must be baked in an oven
from 1808C to 2308C for between four and eight hours
(based on volume), until it is “bone” dry.. Customers cast metal into these 3DP moulds for
prototype evaluation or fully functional parts.
8.3.1 ZCast methodsDirect pour method. The process is based on 3DP using ZCast
material to fabricate a complete mould set including cores and
gating system and provides facility of casting directly bypouring molten material into the mould.
Shell method. This method is used to manufacture largermould than used in the direct pour method and when thegating system would require very large ZCast components.If the size of the mould exceeds the working volume of theprinter, the shell method is recommended[20]. The mouldcavity is formed by a shell of ZCast material and is held in placeby backing it with conventional sand. The gating system isconstructed in the foundry sand by using traditional foundrytooling. In this method, designer is allowed to mount ZCastpieces on a pattern board, which align them with respect to therest of the mould. The ZCast shells have to be so designed thatthey provide connections to the gating system vents and risers,and they must have features that anchor them to the backing offoundry sand. The printed mould pieces consist of cores and auniform shell that surrounds the mould cavity. A flange(containing vent holes, core prints and alignment pin) ofsimilar thickness extends out on the parting line. The mouldpieces are built in sections and aligned together on a blockingboard. The blocking board assembly is placed in a mouldingbox. Standard gating forms are provided in moulding box andfoundry sand is placed around the printed parts.
Combination method (production intent casting). In thismethod, only cores are printed with the ZCast material andused in conventional sand moulds for producing hollowcastings. The sand mould can be created with traditionalmachined pattern or AM fabricated pattern. The mainadvantage of using this method is that cores and inserts can bemade without any special tooling (e.g. core boxes) that wouldlengthen the time to produce the prototype casting.
8.3.2 Research based on ZCast processDimitrov et al. (2007) have presented the results obtained fromthe experimental studies on different RC solutions (all threemethods of ZCast and fiber glass tooling) based on 3DPtechnology in order to improve the design and manufacture offoundry equipment that is used for sand casting of prototypes infinal material. Based on this research authors have suggestedthat in cases where up to four cast components of highcomplexity are required, the ZCast-Direct pour methodprocess should be used. On the other hand, in cases, wheremore than 15 parts or higher runs are needed, or if the tools areexpected to undergo heavy handling, the production intentcasting or even the Fibreglass Tooling process is recommended.
Bassoli et al. (2007) have investigated through experimentsto verify the feasibility and evaluation of the dimensional
Figure 16 Automotive intake manifold
(a)
Notes: (a) Sand mould prepared with ProMetal RCT; (b1, b2) final casting[17]
(b1) (b2)
Table III ProMetal RCT casting materials and application areas
S. no. Material Application areas
1 Al Automotive, prototyping
2 Cu alloys Marine, bearings, fittings
3 Ferrous alloys (grey iron,
ductile iron, steel)
Automotive, general purposes
Rapid casting solutions: a review
Munish Chhabra and Rupinder Singh
Rapid Prototyping Journal
Volume 17 · Number 5 · 2011 · 328–350
340
accuracy of two RC solutions based on 3DP technology.
The first solution was IC starting from 3D-printed starch
patterns and the second solution was ZCast process for the
production of cavities for light-alloys castings. For the second
solution, a design of manufacturing analysis was performed
on the selected benchmark with SOLIDCastw software.
Starting from the CAD model of the casing, complete with
feeding runners and riser, the mould was modelled with a
wall thickness between 12 and 25 mm, minimizing the ZCast
material to limit production time and cost. Researchers
reported that the ZCast technique provided satisfactory
results, limited at present to the field of light alloys. In a
latest research, the mechanical performances of parts
produced by ZCast process were also optimized by varying
thermal treatment parameters (heat treatment by varying
temperature and time) and proved that in the heat treatment
of ZCast parts time has a negligible effect on the compressive
strength, whereas temperature has significant effect for best
mechanical response (Bassoli and Atzeni, 2009).Kaplas and Singh (2008) performed experimental study to
investigate the feasibility of decreasing the shell wall thickness
of mould from 12 to 2 mm thickness using ZCast process to
evaluate the dimensional accuracy and mechanical properties
of castings of zinc-alloy produced by this RC solution.
Dimensional tolerances and mechanical properties were
compared to verify the suitability of castings and further
results were supported by radiography analysis.Singh and Verma (2008) verified the feasibility of
decreasing the shell wall thickness of shell mould from 12 to
2 mm thickness using ZCast process in order to evaluate
the dimensional accuracy for aluminium castings. Further
consistency with the tolerance grades of the castings has been
checked as per IT grades along with mechanical properties of
the aluminium castings.Singh and Singh (2009c) investigated the feasibility of
decreasing the shell mould wall thickness using ZCast RC
solution for brass and lead alloy castings. The study suggested
that the production of sound casting for minimum wall
thickness depends upon pouring temperature and weight
density. The results suggest that for small castings below a
mass of 10 g, shell thickness can be reduced from the 12 to
0.5 mm for lead alloy and 12 to 2 mm for brass alloy castings.
Singh and Singh (2009a,b) also reported the investigation of
this process under statistically control for the best shell wall
thickness in case of low brass (2 mm) and lead (0.5 mm).Based on the results of these researches, it has been found
that it is feasible to reduce the shell wall thickness of moulds
prepared by using ZCast501 from the recommended
thickness (13 mm)[20] and to save the cost and time for
the production of various non-ferrous material castings.
The information in this regard is presented in Table IV.
The researches have proved that the investigated ZCast
solution is effective in obtaining cast technological prototypes
in short times and with low cost, with dimensional tolerances
that are completely consistent with metal casting processes.
The previous major research accessed the feasibility of
decreasing the shell wall thickness of mould obtained using
ZCast solution to evaluate the dimensional accuracy and
mechanical properties of castings of various non-ferrous
alloys. The literature is still lacking in finding the reasons or
factors for obtaining the minimum shell wall thicknesses of
mould by using ZCast solution for a particular material.An attempt has been planned by the authors of this paper to
investigate the means for generating cost effective RCs using
3DP technique[21]. To achieve this objective ZCaste Direct
Metal Casting RC solution will be used to produce shells for
casting to verify the feasibility of decreasing shell wall
thickness from 12 to 2 mm (12,11,10,9,8,7,6,5,4,3,2 mm) as
shown in Figure 17d in order to reduce the cost and time for
the production of Al, Cu and brass castings. Starting from the
identification of benchmark, component and shells have been
modelled using UNIGRAPHICS version NX5 and materials
(Al, Cu and brass alloy) have also been selected to produce
technological prototype castings at different shell wall
thicknesses using 3DP (Z Print machine, Model Z510) with
ZCast501e powder. Consistency of the tolerance grades of
the castings (IT grades) will be evaluated as per UNI EN
20286-I (1995) standards for casting process. Measurements
on a coordinate measuring machine (CMM) with GEOPAK
v2.4.R10 CMM software will be used in calculating the
dimensional tolerances of the castings. Microstructure
analysis and some important mechanical properties will
be compared to verify the suitability of the castings. Further
the dependence of optimum shell wall thickness on change in
volume of casting, pouring temperature, weight density and
heat transfer rate of molten material will also be evaluated.The specific objectives of this proposed research study
include:. effect of change in volume of casting for obtaining
optimum shell wall thickness;. effect of pouring temperature of molten metal for
obtaining optimum shell wall thickness;. effect of weight density of molten material for obtaining
optimum shell wall thickness;. effect of rate of heat transfer for obtaining optimum shell
wall thickness; and. process capability study of optimum shell wall thickness of
materials, namely, Al, Cu and brass experimentation.
Figure17 shows a pilot experiment processing steps from
CAD design of shells to final aluminium casting of benchmark
Table IV Optimum minimum shell wall thickness achieved and reduction in cost and time in comparison to recommended 13 mm thickness usingZCast501by various researches
Researches Casting material
Optimum minimum shell wall
thickness achieved
Production cost
saved (%)
Production time
saved (%)
Kaplas and Singh (2008) Zinc alloy 7 mm 41 37
Singh and Verma (2008) Aluminium alloy 5 mm 54.6 55.4
Singh and Singh (2009a) Lead alloy 0.5 mm 45.75 43
Singh and Singh (2009b) Brass alloy 2 mm 40.05 32.84
Rapid casting solutions: a review
Munish Chhabra and Rupinder Singh
Rapid Prototyping Journal
Volume 17 · Number 5 · 2011 · 328–350
341
using ZCast501 with Z510 printer based on this current
research.
9. Discussion
The survey regarding RC solutions reported in this paper does
not present a complete picture of this incredible technology.
The result from this review is that there is still considerable
room for improvement and innovation of RC solutions.
Despite the invention of various RC solutions, many factors
need to be researched out for the implementation of RC
in traditional foundry practices. These factors are: AM
materials, AM systems, accuracy, surface finish, geometry
flexibility, build time, machine building size, mechanical and
thermal properties, cost and post processing of patterns,
moulds and cores. The major deciding factor to adopt RC
solutions is the cost, because AM systems and materials are
very much expensive when compared to traditional casting
tooling. Presently, RC is economical when the component to
be cast is in the initial stages of design cycle and required in
low quantity. Furthermore, RC is also economical when there
is a need to produce geometrically complex castings and
requirement of changes in design are high. Many researchers
and manufacturers are involved worldwide into the
development of potential new AM systems and materials
used in IC and sand casting.
9.1 Direct fabrication of IC patterns
Although generation of prototype is a natural application of
AM, it is proved that any AM generated component, which
can be flash fired without damaging the ceramic shell can be
used as a substitute of wax IC pattern. Since 1989, many AM
materials have been invented to be used commercially to
produce direct pattern for IC. The main stress has been given
on finding the new materials used for fabricating non-wax IC
patterns without creating the problems of ceramic shell
cracking, incomplete pattern burning out and residual ash
after autoclaving. Although many RC solutions are available
for the production of wax patterns (namely, FDM, MMII,
Thermojet and BPM) directly, non-wax AM patterns are
more popular due to the property of durability and strength
and can be employed for casting of thin wall structure.
Further, to improve the surface quality of patterns, finishing
operation can be performed on non-wax patterns due to their
toughness property. Many AM materials used to produce
non-wax patterns having capability to counter the problems of
ceramic shell cracking, incomplete pattern burning out
and residual ash have been introduced by various
AM manufacturers. The pioneers amongst them are FDM-
ABS, CastForm PS, WindForm PS and ZCorporation’s
starch patterns. As far as ZCorporation’s starch patterns are
concerned, no residual ash appears after burnout process.
Furthermore, starch patterns also have the capability to create
high-quality castings with excellent surface finish. Bassoli et al.(2007) claimed after experimental investigation that the
feasibility of these starch patterns was proven even in the case
of thin walls. Table V presents the advantages and
disadvantages of various AM materials for producing IC
patterns. Mechanical properties and general properties of
some RIC pattern materials are presented in Tables VI and
VII, respectively.
9.2 Fabrication of mould for producing wax IC patterns
This approach utilizes direct and indirect rapid tooling
techniques to fabricate moulds for production of large
number of wax IC patterns economically and with better
accuracy. This approach further relieves the manufacturer
from the problems related to non-wax pattern and using
relatively costly direct AM wax patterns. The indirect tooling
technique is feasible and economical when usually 5-10 AM
patterns of complex shape are required in short period
(one to five weeks) which otherwise required machine tooling
Figure 17 Pilot experiment processing steps from CAD design of shells to final Al casting of benchmark using ZCast501 with Z510 printer
(a) CAD model of upper shell, component and lower shell
(b) Shells in stl. formet in machine software
(c) Printing of shells in Z510 machine
(d) Shells with different wallthicknesses (12-2mm)
(e) Shell ready for pouring (f) Shell poured withmolten metal
(g) Final casting obtainedusing Zcast process
Rapid casting solutions: a review
Munish Chhabra and Rupinder Singh
Rapid Prototyping Journal
Volume 17 · Number 5 · 2011 · 328–350
342
Table
VA
dvan
tage
san
ddi
sadv
anta
ges
ofA
Mfa
bric
ated
ICpa
tter
ns
QuickC
ast
patterns
FDM
ABS
patterns
FDM
WAX
patterns
Model
Mak
erII
patterns
TrueForm
patterns
CastForm
PS
patterns
Windform
wPS
patterns
Thermojet
patterns
Zp14patterns
Advantages
Easy
burn
out
No
risks
of
dam
agin
gdu
ring
clea
nup
proc
ess
Easy
burn
out
Easy
burn
out
Post
finis
hing
isno
t
requ
ired
Low
burn
out
tem
pera
ture
Post
curin
gis
not
requ
ired
Easy
burn
out
Bes
tsu
rfac
efin
ish
asco
mpa
red
to
othe
rno
n-w
axA
M
patt
erns
Bet
ter
surf
ace
finis
has
com
pare
d
toFD
M-w
ax
Cas
ting
tech
niqu
es
usin
gFD
M-w
ax
patt
erns
are
norm
alas
trad
ition
alw
ax
patt
erns
with
out
any
chan
ges
inth
e
conv
entio
nal
IC
proc
ess
Goo
dsu
rfac
efin
ish
Goo
dsu
rfac
efin
ish
Proc
essi
ngof
CF
patt
erns
asno
rmal
wax
patt
erns
with
out
any
chan
ges
in
conv
entio
nal
IC
proc
ess
Hig
hsu
rfac
efin
ish
Exce
llent
up-f
acin
g
surf
ace
finis
h
Due
tow
ax
mat
eria
ls,
patt
erns
can
beus
ed
dire
ctly
inIC
Low
ash
cont
ent
afte
rbu
rnou
tdu
e
toho
neyc
omb
stru
ctur
e
Patt
erns
can
be
tran
spor
ted
easi
ly
due
tohi
gh
stre
ngth
of
mat
eria
l
No
ash
cont
ents
No
supp
ort
stru
ctur
eis
requ
ired
Low
ash
cont
ent
(,0.
02%
)af
ter
burn
out
Low
ash
cont
ent
(,0.
02%
)af
ter
burn
out
No
sepa
rate
mat
eria
lre
quire
d
for
supp
ort
stru
ctur
e
Qui
ckC
ast
build
styl
epa
tter
nsar
e
succ
essf
ulin
coun
terin
gsh
ell
crac
king
durin
g
auto
clav
ing
Less
mat
eria
lis
requ
ired
to
prod
uce
patt
erns
due
toho
neyc
omb
stru
ctur
e
No
risk
ofsh
ell
crac
king
Less
chan
ces
of
shel
lcr
acki
ngdu
e
tolo
wpa
tter
n
expa
nsio
ndu
ring
the
shel
lfir
ing
Cap
able
ofbe
ing
auto
clav
ed
No
risk
ofsh
ell
crac
king
Bui
ldm
ater
ial
can
bere
cycl
ed
Enab
leto
prod
uce
cast
ing
with
high
accu
racy
Hig
hac
cura
cyas
com
pare
dto
FDM
patt
erns
Bet
ter
accu
racy
Patt
erns
prod
uced
with
tight
tole
ranc
es
Hel
pto
redu
cele
ad
time
ofca
stin
gas
com
pare
dto
trad
ition
alIC
Perf
ect
for
Al
and
stee
lca
stin
g
Suita
ble
toca
st
mat
eria
lsw
ith
diff
eren
tm
eltin
g
tem
pera
ture
rang
e
such
asA
l,M
gto
titan
ium
Cas
tw
ithal
lca
st
allo
ysan
dhi
ghly
reac
tive
allo
ys
Patt
ern
can
be
prod
uced
quic
kly
Low
prod
uctio
n
time
and
cost
(con
tinue
d)
Rapid casting solutions: a review
Munish Chhabra and Rupinder Singh
Rapid Prototyping Journal
Volume 17 · Number 5 · 2011 · 328–350
343
Table
V
QuickC
ast
patterns
FDM
ABS
patterns
FDM
WAX
patterns
Model
Mak
erII
patterns
TrueForm
patterns
CastForm
PS
patterns
Windform
wPS
patterns
Thermojet
patterns
Zp14patterns
Abi
lity
topr
oduc
e
thin
wal
lpa
tter
ns
Faci
litat
ein
cast
ing
ofhi
ghly
deta
iled
com
pone
nts
like
jew
elle
ry
Enab
leto
cast
very
thin
wal
lse
ctio
ns
Enab
leto
prod
uce
com
plex
cast
ing
with
inte
rnal
cavi
ties
havi
ngth
in
wal
lth
ickn
esse
s
Enab
leto
prod
uce
cast
ings
of
com
plex
geom
etry
Enab
leto
prod
uce
com
plex
cast
ing
with
vary
ing
thic
knes
s
Disad
vantages
Cas
ting
with
Qui
ckC
ast
patt
erns
requ
irem
ore
expe
rienc
ean
d
spec
ial
proc
essi
ng
asco
mpa
red
to
othe
rno
n-w
axA
M
patt
erns
Poor
surf
ace
finis
h
asco
mpa
red
to
wax
patt
erns
fabr
icat
edw
ith
trad
ition
alw
ax
tool
ing
proc
ess
Slow
build
spee
d
ofsy
stem
Not
suita
ble
for
titan
ium
allo
y
Dow
n-fa
cing
surf
ace
finis
his
poor
Rem
oval
of
supp
ort
mat
eria
l
requ
ires
mor
etim
e
and
spec
ial
care
Cos
tlypr
oces
sing
Furn
ace
isre
quire
d
for
auto
clav
ing
due
tohi
ghm
eltin
g
tem
pera
ture
of
AB
Sm
ater
ial
Wea
kpa
tter
ns
Tran
spor
tatio
nto
a
foun
dry
requ
ires
spec
ial
care
Supp
ort
mat
eria
lis
diff
eren
tfro
mbu
ild
mat
eria
l
Solv
ent
isre
quire
d
for
clea
ning
the
supp
ort
mat
eria
l
Take
sla
rge
cast
ing
time
asco
mpa
red
toC
Fpa
tter
nsas
it
requ
ires
tota
llydr
y
cera
mic
shel
l
befo
reau
tocl
avin
g
Patt
erns
are
frag
ile
and
can
bebr
oken
durin
gcl
eani
ng
and
wax
infil
trat
ion
stag
e
Wax
infil
trat
ion
incr
ease
s
man
ufac
turin
g
time
and
intr
oduc
esfu
rthe
r
dim
ensi
onal
erro
rs
Pres
ently
,ve
ryfe
w
indu
strie
sha
ve
expe
rienc
ed
Win
dFor
mPS
Patt
erns
are
britt
le
inna
ture
and
diffi
cult
to
tran
spor
tto
foun
dry
Diffi
cult
tore
mov
e
supp
ort
stru
ctur
e
Expe
nsiv
ebu
ild
mat
eria
l
Dim
ensi
onal
varia
nce
indu
ced
durin
gw
axdi
ppin
g
stag
e
Rapid casting solutions: a review
Munish Chhabra and Rupinder Singh
Rapid Prototyping Journal
Volume 17 · Number 5 · 2011 · 328–350
344
which take six-25 weeks to build. Furthermore, indirecttooling requires very simple processing and post processing
technique and less equipment and material cost as compared
to direct tooling technique.Direct tooling technique for mould fabrication requires post-
processing steps like infiltration, de-binding, sintering and
finishing operations to fabricate mould with high accuracy and
quality. The major constraint to use this technique to generatewax IC pattern is the lead time require for mould production.
Even though some pioneering processes such as DMLS, Rapid
Tool, ProMetal, LENS and DirectAIM have been used
successfully for direct fabrication of moulds for injection ofwax patterns, which result in relatively strong moulds and
suitable for large volume production.
9.3 Direct fabrication of IC ceramic shells
In continuation to progress made in RIC, a novel casting
solution “DSPC” is moving with a stunning pace inmanufacturing industry to facilitate direct fabrication of the
IC ceramic moulds (negative) with integral cores to produce
parts of virtually any shape and material. This techniqueprovides a greater advantage over other RIC techniques by
removing the steps of wax pattern generation, ceramic shell
production, autoclaving and firing of mould.
9.4 Sand casting
Similar to RIC, extensive worldwide research is being
undertaken by various organizations to improve the existingRC solutions for sand casting. All AM fabricated patterns
having strengths to bear the pressure of moulded sand and
ability to withstand the chemicals in the sand can be used assand casting patterns. As far as dimensional accuracy is
concerned, it is not a critical issue for rapid prototypes to be
used as concept models for visualization purpose. However,
for producing AM-fabricated patterns and core boxes for sandcasting, any error in these casting tooling will be conveyed to
the final cast components. Wang et al. (1999) mentioned in an
investigation that the LOM process introduces a variety of
errors into the pattern and core box fabrication process forsand casting and further the part geometry of thin wall may
not be suitable for LOM-based rapid tooling.A great need of RC solutions having capability of
fabricating ready to pour moulds (pattern less casting) has
been raised by the manufacturers worldwide. Presently, EOS
DirectCastw, ProMetal RCT and ZCast501 are being usedsuccessfully to produce patternless casting by producing
direct sand casting moulds and cores directly from a CAD
model. The introduction of these systems eliminated the
thousand-year-old requirement of physical patterns used tocreate sand moulds. Using this system highly complex and
intricate designed component can be cast very quickly and at
low cost, which was earlier impossible for the traditional
foundry practice. This feature also motivates foundries toproduce spare parts of any product whenever demanded by
the customer. These systems also help to make job shop type
of production economical and feasible for an industry byproducing different designed components with fast
production rate. Table VIII presents the technical features
and Table IX presents the advantages and disadvantages of
these direct sand mould RC solutions. The ProMetal’s RCTS-max machine with largest build area amongst other
available RC solution is a revolutionary invention in the
field of RC to produce large-size component of any geometryof any castable material. The EOS DirectCastw and ProMetal
RCT are also capable produce functional metal casting
in batches.Available AM materials and machines used to fabricate
patterns, moulds and cores for sand casting are being improved.
3D-printed sand used for RC is a latest development in rapid
sand casting. A recent study has been performed to investigatethe behaviour of 3D-printed sand in contact with molten metal
(at elevated temperature) in order to measure the thermal
distortions of the chemically bonded sand binder systems usedto print cores and moulds (Rebros et al., 2007).
Based on applications of various RC solutions, case studies
and examples as discussed above, the major benefits of RC tofoundrymen and challenges amongst the AM manufacturers,
researchers and developers of RC solutions are summarized
below.
9.5 The benefits of RC to foundrymen
1 Cost saving. Cost is saved due to the elimination oftraditional casting tooling required to cast prototype or low
volume production castings. The cost involved in
modifying a poor-designed component and iterationsrequired before finalization of design is also reduced by
using RC solutions. Casting tooling does not need to be
ordered until the design is finalized and frozen.
Table VI Mechanical properties of RIC pattern materials
CastForm PS FDM ABS Zp14
Tensile strength 2.8 MPa 34.45 MPa (ASTM D638) 10.8-15 MPa
Elastic modulus 1,604 MPa 2,495 MPa (ASTM D638) 3,000-4,000 MPa
Elongation – .10% (%at yield) –
Impact strength ,11 J/m 107 J/m (notched Izod test) 12-13 J/m
Hardness (shore D-scale) – 78 68-74
Table VII General properties of RIC pattern materials
WindForm PS Thermojet88 CastForm PS
Density 0.43 g/cm3 (ASTM D4164) 0.846 g/cm3 0.46 g/cm3
Ash content ,0.02% (ASTM D482) 0.00-0.01% (gray wax) 0.02% (ASTM D482)
Glass transition temp 87.5oC (DSC) 85-95oC 89oC
Rapid casting solutions: a review
Munish Chhabra and Rupinder Singh
Rapid Prototyping Journal
Volume 17 · Number 5 · 2011 · 328–350
345
Table
VIII
Tech
nica
lfe
atur
esof
dire
ctsa
ndm
ould
RC
solu
tions
RCtechnology
Machine
Compan
y
Core
technology
Builden
velope
(X,Y,Z)(m
m)
Additional
supports
required
?
Building
material
Binder
Infiltration
agen
t
Layerthickn
ess
(mm)
Buildspee
d
Prices
(baseprice)
ProMetal
RCT
technique
RC
TS1
5Ex
One
Sand
3DP
(Dro
p-on
-Bed
)
1,50
0£
750£
700
NO
Sand
Res
inN
/A0.
15-0
.415
,000
cm3/h
$1.4
mill
ion
RC
TS-
Max
1,80
0£
1,00
0£
700
0.28
-0.5
59,4
00-
108,
000
cm3/h
$1.3
mill
ion
ZCastdirectmetal
casting
ZPr
inte
r
310p
lus
ZC
orp
3DP
(Dro
p-on
-Bed
)
203£
254£
203
254£
356£
203
NO
ZCas
t50
1Zb
56N
/A0.
089-
0.20
32-
4la
yers
/min
2la
yers
/min
$19,
900
–
Spec
trum
Z510
DirectCastEO
SINTS
EOSI
NT
S750
EOS
Sand
LS
720£
380£
380
700£
380£
380
NO
Qua
rtz
4.2/
5.7
N/A
N/A
0.2
2,50
0cm
3/h
e69
0,00
0
–
EOSI
NT
S700
Rapid casting solutions: a review
Munish Chhabra and Rupinder Singh
Rapid Prototyping Journal
Volume 17 · Number 5 · 2011 · 328–350
346
2 Gating system optimization. The major effort involved in
foundry is to optimize gating and runner system design.
The use of AM patterns for trial run castings facilitates
the optimization of gating system before placing the orderof production tooling.
3 Concurrent engineering approach. AM facilitates theimplementation of concurrent engineering approach by
creating a communication link between designers, pattern
makers, foundry men and customer simultaneously. This
approach helps to study the problems associated withevery stage of casting a product and also to analyze
product modification options by using AM models which
result in short time to market the product.4 RC allows the foundry to cast components with complex
geometry and intricate cavity which are either too
expensive or impossible to cast by conventional castingmethods.
5 Process optimization. Before manufacturing the production
tooling, the perfect positioning of parting lines, ejectingpins and inserts can be analyzed with prototype casting
produced by using RC solution. Optimization of
moulding parameter and evaluation of mould andpattern can be conducted effectively.
6 The use of RC solutions is found more economical and
feasible in emergency especially if quantities of castingsare required before the production tool is ready.
9.6 Challenges amongst AM developers for RC
1 The claim of available RC solutions to producedimensionally accurate, smooth surface finish and
durable casting with shorter time to market needs to
be further addressed, verified and improved.2 Although RC tends to generate complex casting, some
RC solutions require additional post-processing steps
which increase the cost and lead time required to castcomponents.
3 From the above discussion, it is obvious that each RC
solution possesses its own set of qualities. The real factis that some RC solutions are in their initial
development stages, and there is no clear evidence
that the use of these RC solutions will be beneficial in
terms of cost and lead time required to produce a unit of
final metal casting.4 Development of low cost RC materials and AM
machines for small scale foundries.5 Need to familiarize the casters and pattern makers with
available RC solutions, processes, parameters and
techniques to implement RC in the traditional foundry
practices.6 Development in AM machines to reduce the build time
required to produce casting tooling.7 Fulfill the requirement of mass production of metal
casting at commercial level.8 Development of new AM material and machines to
produce casting in metals, ceramic and composites
directly.9 Solutions for problems associated with application of
non-wax patterns in IC.10 Enhancement in work volume of AM machines to
produce large-size cast components.
10. Future trends in the development of RCT andtheir application
Rapid casting has gained acceptance worldwide by the
manufacturers and is expected to become one of the
important applications of additive technology in future. RC
solutions discussed in this paper are being improved
continuously, and new casting solutions are being
developed. It is anticipated that a number of new systems
dedicated to provide casting solutions directly (without using
any intermediate step) like DSPC, ProMetal RCT and
EOSINT S will be on the market in the next few years.
An important constraint to incorporate RC in foundry is the
high cost of AM machines, building materials and
consumables. Foundry industry requires cheaper machines
with low-cost building materials and consumables to produce
patterns or direct moulds for IC and sand casting.
Table IX Advantages and disadvantages of direct sand mould RC solutions
DirectCast with EOSINT S700/750 ProMetal RCT S15/SMax ZCast501 with Zprinter501
Advantages Minimum post processing is required
Cast any type of material from Al,
Mg to high alloy steel
Same sand material is used for support
structure
Enable to build large size castings
Patternless
Ability to make high quality fully functional
castings in small series
Enable to generate cost effective prototype
castings rapidly
No post processing is required
Suitable for ferrous and nonferrous castings
No support structure is required
Larger build area for producing large moulds
Patternless
System is provided with automatic loading
and unloading conveyors
Online mixing of sand and hardener
Ready to pour moulds
Ability to cast relatively low volume part with
good degree of complexity
Geometry independent process
Support is provided by the build material itself
Suitable in office environment just like office
printer
Patternless
Z510 printer is fastest 3D colour printer
Cost effective castings can be produced in a
short time
Disadvantages Relatively large space is required to install the
system
Consume high power due to use of lasers to
sinter the sand
System is dedicated to fabrication of sand
moulds and cores only
Large space required to install the system as
compared to other two processes
Suitable only for non-ferrous castings
Suitable for small size prototype castings
Costly build material and binders used as
compared to other systems
Rapid casting solutions: a review
Munish Chhabra and Rupinder Singh
Rapid Prototyping Journal
Volume 17 · Number 5 · 2011 · 328–350
347
The worldwide ongoing research in various fields of RC
and AM will give momentum to the following developments
in RC:. New wax like materials will be invented for IC patterns
which will produce patterns with high accuracy, surface
finish and without producing ash contents and shell
cracking during autoclaving.. Invention of material to produce pattern less moulds for
sand casting for ferrous and nonferrous material having
high melting temperature.. Invention of material having high strength for production
of patterns which can produce large number of moulds for
mass production of casting.. New AM machines will be available in the market with
large working platform to produce large-size patterns and
moulds for casting of large-size components.. With the development of AM machines having features
such as fast build speed, high resolution and capability of
producing parts with thin layer thickness, the mass
production of geometrically complex casting with desired
material will be possible.
There will be a great change in the attitude of foundry men by
adopting RC solutions in their foundries. Although various
RC solutions like EOSINT – S and ProMetal RCT are
available to produce moulds and cores directly using
conventional foundry sand, invention of new AM material is
possible in future, which will enhance flowability of pouring
metal and will also help to improve the microstructure of
casting. In addition, transparent material will also be
invented, so that the proper filling of cavity can be judged
on the spot. The possibilities seem limitless. One future
application is the development of expert system and
intelligent AM systems, a combination of AM, RT, RC and
artificial intelligence. Several expert systems based on RC will
be available in market for the selection of RC solutions, AM
systems and suitable materials for the required casting. RC
industry will also move toward standardization. All these
future developments will be possible only when foundry
industry will be willing to be an active partner in the
development and use of these RC solutions.
11. Conclusion
Based on the survey presented in this paper regarding RC
solutions, a conclusion can be drawn that the RC which has
evolved from AM, extends from its infant stage and is ready
to play a mature role in achieving the goal to produce fully
functional AM products in the required material. The main
aim of this review is to present the various commercialized RC
solutions in investment and sand casting technologies. One of
the most important contributions of RC in manufacturing
industry is the facilitation of concurrent engineering approach
in design, development and production of any type of casting.
The RC solutions reviewed in this paper for both IC and sand
casting will serve the purpose of researchers, academicians,
users, manufacturers and service industries to explore the new
options and further development in the field of RC.
The various approaches and techniques explained of using
AM in investment and sand casting processes may serve the
purpose of foundrymen in different working conditions.
The paper ends with a hope that in future, RC solutions will
emerge with the capability to provide dimensionally more
accurate and better surface finish castings of any size, shape
and material with more speed and at low cost. In order to
strengthen the manufacturing capabilities, especially for
developing countries to cope up with the impatient global
customer demands, RC solutions and AM machines should
be within the financial reach for small-scale foundries.
Notes
1 Project-Innovative production machines and systems
(2006), available at: www.iproms.org/system/files/
iproms_D4.9_APM_updated_State_of_the_Art_8_8_06.
pdf2 Z Corporation ZP14 investment casting processing
guide, ZCorporation, available at: www.zcorp.com3 http://um3d.dc.umich.edu4 www.3dsystems.com/products/sls/index.asp5 Italian Formula 1 Race Team Turns to Rapid
Prototyping and Manufacturing to Create High-
Performance Titanium Parts Made from CastForm PS
Patterns PR Newswire 21 July 2000, available at: www.
thefreelibrary.com6 www.crptechnology.com7 www.crp.eu8 Racers digs speed of rapid prototyping, MetlFax,
December 2000, available at: www.allbusiness.com/
manufacturing/9 www.windform.it/sito/en/windform-ps-new-polystyrene-
based-material.html10 Soligen Technologies Inc., www.soligen.com11 www.mit.edu/, tdp12 Sand Casting Applications, available at: www.2objet.com13 www.eos-gmbh.de14 US patent issued to EOS GmbH for sand-casting
application of laser-sintering: DirectCast, 13 October
2000, available at: www.thefreelibrary.com15 www.exone.com16 RCT takes layer-by-layer approach to mold, core
production, modern casting, 1 February 2005, available
at: http://goliath.ecnext.com17 www.prometal-rct.com18 Rapid casting technology is critical to “world’s most
expensive production vehicle”, Foundry Management
and Technology, 11 October 2007, available at: www.
foundrymag.com19 www.zcorp.com20 ZCast501 Direct Metal Casting, Design Guide,
September 2004, ZCorporation, available at: www.
zcorp.com21 Three dimensional printing: shortcut to the final
product, technology transition: NSF-funded research to
market, 6 May 2002, available at: www.nsf.gov
References
Ashley, S. (1995), “Rapid prototyping is coming of age”,
Mechanical Engineering, Vol. 117 No. 7, pp. 62-8.Bak, D. (2003), “Rapid prototyping or rapid production? 3D
printing processes move industry towards the latter”,
Assembly Automation, Vol. 23 No. 4, pp. 340-5.Bassoli, E. and Atzeni, E. (2009), “Direct metal rapid casting:
mechanical optimization and tolerance calculation”, RapidPrototyping Journal, Vol. 15 No. 4, pp. 238-43.
Rapid casting solutions: a review
Munish Chhabra and Rupinder Singh
Rapid Prototyping Journal
Volume 17 · Number 5 · 2011 · 328–350
348
Bassoli, E., Gatto, A., Luliano, L. and Violentte, M.G.
(2007), “3D printing technique applied to rapid casting”,
Rapid Prototyping Journal, Vol. 13 No. 3, pp. 148-55.Beaman, J.J., Barlow, J.W., Bourell, D.L., Crawford, R.H.,
Marcus, H.I. and McAlea, K.P. (1997), Solid FreeformFabrication: A New Direction in Manufacturing, Kluwer,Boston, MA.
Bernard, A., Deplace, J., Perry, N. and Gabriel, S. (2003),
“Integration of CAD and rapid manufacturing for sandcasting optimization”, Rapid Prototyping Journal, Vol. 9,
pp. 327-33.Carrion, A. (1997), “Technology forecast on ink-jet head
technology applications in rapid prototyping”, RapidPrototyping Journal, Vol. 3 No. 3, pp. 99-115.
Cheah, C.M., Chua, C.K., Lee, C.W., Feng, C. and
Totong, K. (2005), “Rapid prototyping and tooling
techniques: a review of applications for rapid investment
casting”, International Journal of Advanced ManufacturingTechnology, Vol. 25, pp. 308-20.
Chua, C.K. (1994), “Three-dimensional rapid prototyping
technologies and key development areas”, Computing &Control Engineering Journal, Vol. 5 No. 4, pp. 200-6.
Chua, C.K., Hong, K.H. and Ho, S.L. (1999), “Rapidtooling technology. Part 1: a comparative study”,
International Journal of Advanced Manufacturing Technology,
Vol. 15, pp. 604-8.Chua, C.K., Howe, C.T. and Hoe, K.E. (1998), “Integrated
rapid prototyping and tooling with vacuum casting for
connectors”, International Journal of AdvancedManufacturing Technology, Vol. 14, pp. 617-23.
Chua, C.K., Leong, K.F. and Lim, C.S. (2003), RapidPrototyping: Principles and Applications, World Scientific,Singapore.
Chua, C.K., Feng, C., Lee, C.W. and Ang, G.Q. (2005),
“Rapid investment casting: direct and indirect approachesvia model maker II”, International Journal of AdvancedManufacturing Technology, Vol. 25, pp. 26-32.
Cohen, A. (2008), “Sand casting applications using rapid
prototyping technology”, white paper, available at: www.
2objet.com (accessed 29 July 2008).Copper, K.G. and Wells, D. (2000), Application of Rapid
Prototyping to the Investment Casting of Test Hardware, Project
Report, NASA, Marshall Space Flight Center, Huntsville,AL.
Denton, K.R. (1994), “Investment casting plays major role in
Ford ‘rapid tooling’ project- a case study”, INCAST, Vol. 7No. 10, pp. 15-17.
Detlef, K., Chua, C.K. and Du, Z. (1999), “Rapid
prototyping issues in the 21st century”, Computers inIndustry, Vol. 39, pp. 3-10.
Dickens, P.M., Hague, R. and Wohlers, T. (2000), “Methods
of rapid tooling worldwide”, available at: www.moldmakingtechnology.com
Dickens, P.M., Stngroom, R., Greul, M., Holmer, B.,Hon, K.K.B., Hovtun, R., Neumann, R., Noeken, S. and
Wimpenny, D. (1995), “Conversion of RP models to
investment castings”, Rapid Prototyping Journal, Vol. 1
No. 4, pp. 4-11.Dimitrov, D., van Wijck, W. and de Beer, N. (2007),
“An introduction to rapid casting development andinvestigation of process chains for sand casting of
functional prototypes”, South African Journal of IndustrialEngineering, Vol. 18 No. 1, pp. 157-73.
Dimitrov, D., Schreve, K., Beer, N. and Christiane, P. (2008),
“Three dimensional printing in the South African industrial
environment”, South African Journal of IndustrialEngineering, Vol. 19, pp. 195-213.
Dotchev, K. and Soe, S. (2006), “Rapid manufacturing of
patterns for investment casting: improvement of quality and
success rate”, Rapid Prototyping Journal, Vol. 12 No. 3,
pp. 156-64.Dotchev, K.D., Dimov, S.S., Pham, D.T. and Ivanov, A.I.
(2007), “Accuracy issues in rapid manufacturing
CastForme patterns”, Journal of Engineering Manufacture(Proceedings – Institution of Mechanical Engineers Part B),Vol. 221 No. 1, pp. 53-67.
DTM Corporation (1999), The Synterstation Systems. Guide toMaterials: CastForm PS, DTM Corporation, Austin, TX.
Freitag, D., Wohlers, T. and Philippi, T. (2003), “Rapid
prototyping: state of the art”, Manufacturing TechnologyInformation Analysis, available at: www.dtic.mil/cgi-bin
Gebhardt, A. (2003), Rapid Prototyping, Hanser Gardener,
Cincinnati, OH.Gouldsen, C. and Blake, P. (1998), “Investment casting using
FDM ABS rapid prototype patterns”, available at: www.
stratasys.com (accessed 26 July 2008).Greenbaum, P.Y. and Khan, S. (1993), “Direct investment
casting of rapid prototype parts: practical commercial
experience”, Proceeding of 2nd European Conference on RapidPrototyping, Nottingham, 15-16 July, pp. 77-93.
Grimm, T. (2003), “Fused deposition modelling:
a technology evaluation”, Vol. 11 No. 2, available at:
www.time-compression.com (accessed 31 December 2007).Groover, M.P. (1996), Fundamentals of Modern Manufacturing:
Materials, Processes and Systems, Prentice-Hall, New York, NY.Heine, R.W., Loper, C.R. and Rosenthal, P.C. (1997),
Principles of Metal Casting, Tata McGraw-Hill, New Delhi.Hilton, P.D. and Jacobs, P.F. (2000), Rapid Tooling
Technologies and Industrial Applications, CRC Press,
Dallas, TX.Hopkinson, N. (2002), “Rapid manufacturing: what, why,
and how?”, Foundry Trade Journal, Vol. 176 No. 3590,
pp. 12-15.Jacobs, P.F. (1993), “Stereolithography 1993: epoxy resins,
improved accuracy & investment casting”, Proceedings of 4thInternational Conference on Rapid Prototyping, Dyton, OH,14-17 June, pp. 249-62.
Jacobs, P.F. (1995), “QuickCastTM1.1 and Rapid Tooling”,
Proceedings of the 4th European Conference on RapidPrototyping and Manufacturing, University of Nottingham,Nottingham, 13-15 June, pp. 1-25.
Jain, P.L. (2009), Principles of Foundry Technology, Tata
McGraw Hill, New Delhi.Kaplas, M. and Singh, R. (2008), “Experimental
investigations for reducing wall thickness in zinc shell
casting using three dimensional printing”, Proceedings ofInstitute of Mechanical Engineers, Part C: Journal ofMechanical Engineering Science, Vol. 222 No. 12, pp. 393-7.
Karapatis, N.P., van Griethuysen, J.-P.S. and Glardon, R.
(1998), “Direct rapid tooling: a review of current research”,
Rapid Prototyping Journal, Vol. 4, pp. 77-89.Kouznetsov, V.E. (2004), “New trends in rapid prototyping
and rapid manufacturing applications in metal casting”,
Business Exchange – News Letter, 1 October.Krouth, T.J. (2002), “Foundry tooling and metal castings in
days”, Proceedings from International Conference: Worldwide
Rapid casting solutions: a review
Munish Chhabra and Rupinder Singh
Rapid Prototyping Journal
Volume 17 · Number 5 · 2011 · 328–350
349
Advances in Rapid and High-Performance Tooling, EuroMold,
Frankfurt/M, Germany.Lee, C.W., Chua, C.K., Cheah, C.M., Tan, L.H. and Feng, C.
(2004), “Rapid investment casting: direct and indirect
approaches via fused deposition modelling”, InternationalJournal of Advanced Manufacturing Technology, Vol. 23,
pp. 93-101.Lightman, A.J. (1997), “Materials- ceramics”, JTEC/WTEC
Panel Report on Rapid Prototyping in Europe and Japan, RPAof the SME, available at: http://itri.loyola.edu/rp/02_02.htm
(accessed 29 September 2008).McMains, S.A. (1995), “Rapid prototyping of solid three-
dimensional parts”, Master’s project, Computer Science
Division, University of California, Berkeley, CA.Mueller, B. and Kochen, D. (1999), “Laminated object
manufacturing for rapid prototyping and pattern making in
foundry industry”, Computers in Industry, No. 1, pp. 47-53.Pak, S.S. and Klosterman, D.A. (1997), “Prototype tooling
and low volume manufacturing through laminated object
manufacturing (LOM)”, The 7th International Conference onRapid Prototyping, San Francisco, CA, pp. 325-31.
Pal, D.K. and Ravi, B. (2007), “Rapid tooling route selection
and evaluation for sand and investment casting”, Virtualand Physical Prototyping Journal, Vol. 4, pp. 197-207.
Pereira, A., Perez, J.A., Dieguez, J.L., Pelaez, G. and Ares, J.E.
(2008), “Design and manufacture of casting pattern plates by
rapid tooling”, Archives of Material Science, Vol. 29 Nos 1/2,
pp. 63-7.Rebros, M., Ramrattan, S.N., Joyce, M.K. and Ikonomov, P.G.
(2007), “Behavior of 3D printed sand at elevated
temperature”, AFS Transactions, Vol. 115 No. 4, pp. 7-136.Rosochwski, A. and Matuszak, A. (2000), “Rapid tooling: the
state of the art”, Journal of Materials Processing Technology,
Vol. 106, pp. 191-8.Sachs, E., Cima, M. and Cornie, J. (1991), “Three
dimensional printing: ceramic shells and cores for casting
and other applications”, Proceedings of the 2nd InternationalConference on Rapid Prototyping, University of Dayton,
Dayton, Ohio, 23-26 June, pp. 39-53.Singh, J.P. and Singh, R. (2009a), “Investigations for
statistically controlled rapid casting solution of lead alloys
using three dimensional printing”, Journal of MechanicalEngineering Sciences (Proceedings – Institution of MechanicalEngineers Part C), Vol. 223, C9, pp. 2125-34.
Singh, J.P. and Singh, R. (2009b), “Investigations for
statistically controlled rapid casting solution of brass alloys
using three dimensional printing”, International Journal of
Rapid Manufacturing, Vol. 1 No. 2, pp. 208-21.Singh, R. (2010), “Three dimensional printing for casting
applications: a state of art review and future perspectives”,
Advanced Materials Research, Vol. 83-86, pp. 342-9.Singh, R. and Singh, J.P. (2009c), “Comparison of rapid casting
solutions for lead and brass alloys using three dimensional
printing”, Journal of Mechanical Engineering Science(Proceedings – Institution of Mechanical Engineers Part C),
Vol. 223, C9, pp. 2117-23.Singh, R. and Verma, M. (2008), “Investigation for reducing
wall thickness of aluminium shell casting using three
dimensional printing”, Journal of Achievements in Materialsand Manufacturing Engineering, Vol. 31, pp. 565-9.
Smith, B.J., St Jean, P. and Duquette, M.L. (1996),“A comparison of rapid prototype technique for investmentcasting Be-Al”, Proceedings of Rapid Prototyping andManufacturing Conference, Dearbon, MI, 23-25 April, pp. 1-11.
Tromans, G. (2004), Development in Rapid Casting, Wiley,New York, NY.
Upcraft, S. and Fletcher, R. (2003), “The rapid prototypingtechnologies”, Assembly Automation, Vol. 23 No. 4,pp. 318-30.
Wang, W., Conley, J.G. and Stoll, H.W. (1999), “Rapid toolingfor sand casting using laminated object manufacturingprocess”, Rapid Prototyping Journal, Vol. 5 No. 3, pp. 134-40.
Wohlers, T.T. (1992), “The world of rapid prototyping”,Proceedings of the Fourth International Conference on DesktopManufacturing, SanJose, CA, 24-25 September, available at:www.wohlersassociates.com
Wohlers, T.T. (1995a), “Future potential of rapid prototypingand manufacturing around the world”, Rapid PrototypingJournal, Vol. 1 No. 1, pp. 4-10.
Wohlers, T.T. (1995b), “RP’s impact worldwide”, paperpresented at the 28th Symposium on AutomotiveTechnology and Automation (ISATA) Conference,Stuttgart, 18-22 September, available at: www.wohlersassociates.com
Wohlers, T.T. (2003), “Rapid prototyping: status andemerging technologies”, paper presented at the DOEWorkshop, Tooling Technology for Low – Volume VehicleProduction, Detroit, MI, 18 November, available at: www.wohlersassociates.com (accessed 29 September 2008).
Wohlers, T.T. (2006), “Wohlers report 2006: RP, RT, RMstate of the industry”, Annual Worldwide Progress Report,Wohlers Associates Inc., Fort Collins, CO.
Wohlers, T.T. (2007), “Wohlers Report 2007: ExecutiveSummary”, Annual Worldwide Progress Report, WohlersAssociates Inc., Fort Collins, CO, available at: www.wohlersassociates.com/2001-Executive-Summary.pdf
Yao, W.L. and Leu, M. (1999), “Analysis of shell cracking ininvestment casting with laser stereolithography patterns”,Rapid Prototyping Journal, Vol. 5 No. 1, pp. 12-20.
Further reading
Greul, M., Pintat, T. and Greulich, M. (1995), “Rapidprototyping of functional metallic parts”, Computers inIndustry, Vol. 28, pp. 23-8.
Shan, Z., Yan, Y., Zhang, R., Lu, Q. and Guan, L. (2003),“Rapid manufacture of metal tooling by rapid prototyping”,International Journal of Advanced Manufacturing Technology,Vol. 21, pp. 469-75.
Wohlers, T.T. (1991), “Rapid prototyping: an update on RPapplications, technology improvements, and developmentsin the industry”, available at: www.wohlersassociates.com
Corresponding author
MunishChhabra can be contacted at: [email protected]
Rapid casting solutions: a review
Munish Chhabra and Rupinder Singh
Rapid Prototyping Journal
Volume 17 · Number 5 · 2011 · 328–350
350
To purchase reprints of this article please e-mail: [email protected]
Or visit our web site for further details: www.emeraldinsight.com/reprints