DEFECT ANALYSIS OF HAND WHEEL CASTING … Regmi Assistant Professor, Nepal College of Information Technology, Kathmandu ABSTRACT In the present casting arena, emphasis is laid on the

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International Journal of Mechanical Engineering and Technology (IJMET) Volume 7, Issue 5, September–October 2016, pp.46–56, Article ID: IJMET_07_05_006

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DEFECT ANALYSIS OF HAND WHEEL CASTING

USING COMPUTER AIDED CASTING SIMULATION

TECHNIQUE

Bijendra Prajapati

Asst. Professor, Institute of Engineering, Western Regional Campus, Pokhara.

Hari Dhakal

Assistant Professor, Nepal Engineering College, Kathmandu

Mukesh Regmi

Assistant Professor, Nepal College of Information Technology, Kathmandu

ABSTRACT

In the present casting arena, emphasis is laid on the precise and defect free casting, minimum

production cost, develop the components on demand in short period of time accompanied by high

yield of production for casting units & foundries. In order to achieve this level, Fish-bone diagrams

and computer simulation technique are inevitably necessary. The paper studies on the shrinkage

defect prevailing in the Hand wheel casting and its remedy with the help of casting simulation

software ADSTEFAN.

Due to the lack of standard acceptable theoretical procedures, the design processes are

normally carried on a trial-and-error basis. Systematic studies & analyses are carried out to

understand the reasons for occurrence of defects and suitable remedial measures are identified.

Then, computer assisted casting simulation technique is used to analyze the casting defects.

Shrinkage porosity analysis is performed using this technique by introduction of a new gating

system design, followed by various iterations that include changing of the length of runner and

introducing a riser.

The results show a significant reduction in shrinkage porosity and improvement in yield. This

can be of great economic value due to reduction in material consumption and less unit price for

production. The proposed approach reduces the rejection due to casting defects in foundries. This

will especially help SME foundries to significantly improve their quality levels.

Key words: Hand wheel, Casting Simulation, Fish Bone Diagram, ADSTEFAN, Shrinkage, Yield.

Cite this Article: Bijendra Prajapati, Hari Dhakal and Mukesh Regmi, Defect Analysis of Hand

Wheel Casting using Computer Aided Casting Simulation Technique. International Journal of

Mechanical Engineering and Technology, 7(5), 2016, pp. 46–56.

http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=7&IType=5

Defect Analysis of Hand Wheel Casting using Computer Aided Casting Simulation Technique


1. INTRODUCTION

One of the oldest manufacturing processes, Casting, is still extensively used to produce complicated metal

shapes with little or no further machining in a very economical way. Casting is a manufacturing process by

which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape,

and then allowed to solidify [1]. There are two main consecutive stages, filling process and solidification

process in casting production.

Casting process design is important for production quality and efficiency. Casting quality is heavily

dependent on the success of gating/riser system design, which currently is conducted mainly relied on

technicians’ experience. Therefore there is a need for the development of a computer-aided casting process

design tool with CAD, simulation, and optimization functions to ensure the quality of casting [2].

With regards to the project work, defect analysis of Hand wheel casting has been selected. Hand wheel

can be defined as a wheel worked by hand. Hand wheels are used to adjust a variety of machine functions

and are great for any application where adjustments need to be made via a turning mechanism. Out of

different casting processes, shell molding process is best suited casting process to manufacture Hand

wheels since shell molding offers better surface finish, high productivity and precision of the process.

No process is full-proof or perfect. Casting process also has some shortcomings namely casting defects.

That’s why Casting process is also known as process of uncertainty. An undesired irregularity in the metal

casting process is termed as casting defect. Even in a completely controlled process, defects are found in

casting. Such defects challenge explanation about the cause of casting defects. The complexity of the

process is credited to the involvement of the various disciplines of science and engineering with casting. It

is found that the cause of defects is often a combination of several factors rather than a single one. To

tackle them, the methods like fish bone diagram, casting simulation technique & Campbell’s 10 rules for

making reliable castings have been proposed to ensure defect free castings with maximum yield. The main

concern is shrinkage defect. Shrinkage is reducing the volume of the casting material when metal is

cooling and solidifying that produces the line, holes in the casting, it’s called the shrinkage defect.

For the casting simulation of Hand wheel, ADSTEFAN software has been employed. ADSTEFAN

stands for Advanced Solidification Technology for Foundry aided by numerical Simulation. ADSTEFAN

is casting simulation software that accurately simulates the entire casting process providing a quick and

reliable solution for real casting problems. Casting simulation should be used when it can be economically

justified for at least one of the following three reasons:

• Quality enhancement by predicting and eliminating internal defects like porosity

• Yield improvement by reducing the volume of feeders and gating channels per casting

• Rapid development of a new casting by reducing the number of foundry trials [3].

2. OBJECTIVES

The main objective is to minimize the rejections of the Hand wheel casts through defect analysis by using

casting simulation software namely “ADSTEFAN”.

Apart from this, the secondary objectives of the study are

• Selection of appropriate process variables such as Pouring temperature, Filling time, Shell mold, Chemical

property of the molten metal for simulation and others.

• Develop a 3D model of Hand wheel pattern for simulation by “ADSTEFAN software” along with mold

filling & solidification analysis.

• Investigate Effect of gating system to overcome shrinkage defect.

• Find out the reduction in shrinkage defects & improvement in Yield after applying modifications in design

& use of casting simulation software.

Bijendra Prajapati, Hari Dhakal and Mukesh Regmi


3. LITERATURE REVIEW

An extensive literature review has been done with few of the selected papers related to Casting defects &

Casting simulation technique. The main focus areas of these papers are the occurrence of shrinkage defects

in the casting piece and the application of the casting simulation technique to optimize the defects

effectively. These papers discuss on the various types of defects that are studied for different casting

processes, the materials used, methodologies involved, different types of casting simulation software’s

used, different parameters considered for the defect analysis and so on.

Swapnil A. Ambekar and Dr. S. B. Jaju [2] have studied about the need of foundry to manufacture

defect free castings with minimum production cost. Due to the lack of existing theoretical procedures the

designing processes are normally carried on a trial-and-error basis. Different optimisation approaches like

Multi-Objective Evolutionary Algorithm (MOEA), Theory of Inventive Problem Solving (TRIZ), and

Design of Experiments (DOE) have been discussed. It is concluded that with a more reasonable gating

system obtained by analysis of casting simulation results, the need can be achieved with other added

benefits.

Dr. B. Ravi [3] has studied the benefits of casting simulation (both tangible and intangible), bottlenecks

(technical and resource related) and some best practices to overcome the bottlenecks. It has explained all

five stages of simulation projects in detail. Major concerns relating to simulation have been properly

addressed & illustrated with industrial examples. Bhupendra [4] studied & found that about 90% of the

defects in castings are due to wrong design of gating & risering system and only 10% due to manufacturing

problems. Casting simulation process can be used to solve those problems. He studied detection of hot

spots in casting of Release Bearing Housing with the help of casting simulation software called ProCast.

The simulated results are also compared with the experimental works.

Vipul Vasava and Dhaval Joshi [5] have studied about the Shrinkage cavity that is detrimental to

mechanical performances of casting parts. They have found that Design engineers often use large safety

factors in many designs due to insufficient understanding of quantitative effects of shrinkage cavity

defects.

Harshwardhan et al. [6] have studied that the methods layout of a casting is an important activity in

tooling development. It involves critical decisions regarding part orientation in mold, parting line, cores,

cavity layout, feeders, feed aids and gating system. Optimization of methoding parameters with the help of

simulation is discussed and it is tried to minimize efforts and avoid conventional trial and error practice.

The simulation model is built to assess the methoding parameters using Auto Cast simulation software.

Yeh-Liang Hsu and Chia-Chieh Yu [7], In this research, a casting simulation software is used to

simulate the casting process of aluminium wheels. The casting simulation is done iteratively until the mold

temperature converges to a stable temperature with the help of ProCast. Shrinkage Index (SI) is defined to

describe quantitatively the level of casting shrinkage from casting simulation. This paper also discusses the

influence of cooling process parameters on SI, including initial mold temperature, and geometry of the

wheel, which verifies engineers’ empirical data. They concluded that this iterative simulation process and

SI can be used to predict the casting quality of aluminium wheels and to find the optimal parameters of the

casting process.

The review of literature has provided lots of information & insights about the defect analysis, various

methodologies related to defect analysis, different causes and remedies of the casting defects and various

types & working of the casting simulation softwares.

4. PROBLEM STATEMENT

The casting defect in Hand wheel has been considered for the study. The problem belongs to SME,

Matruchaya Engineering that manages to get the order of hand wheels as per the drawing specifications.

Following the shell casting process, the hand wheels have been manufactured but the main concern is the

occurrence of shrinkage defect as shown in the figure. 1.1



It was noticed that these defects are frequently occurring at particular locations and are of the irregular

shape & size. The defects are found inside the drilled portion of hand wheel which are otherwise invisible

before drilling. Its occurrence is found to be about 35-40 in every 100 casts. Since, the rejection is so high,

it is to be solved to attain 3-5 defects.

5. PROPOSED STUDY

In order to obtain remedy, the project work has been destined to study the following perspectives:

• Finding the root cause of occurrence of defects in the rejection of casting

• Taking necessary steps to reduce the defects and to improve the casting yield

• Techniques like cause-effect diagrams and casting simulation technique to be used

6. MATERIALS & METHODOLOGIES

Though various types of metals like cast iron, grey cast iron, S G iron and others can be used, based on the

requirement to the respective requirement, S G iron 400/12 has been selected. Essentially ductile cast iron

consists of graphite spheroids dispersed in a matrix similar to that of steel.

For the defect analysis of the hand wheel, two methods have been employed namely Fish bone diagram

and casting simulation technique. Third method has been proposed to ensure proper foundry practices for

reliable castings.

6.1. Fishbone Diagram/ Cause-Effect Diagrams

Ishikawa diagrams (also called fishbone diagrams, herringbone diagrams, cause-and-effect diagrams, or

Fishikawa) are causal diagrams created by Kaoru Ishikawa (1968) that show the causes of a specific event.

Common uses of the Ishikawa diagram are product design and quality defect prevention, to identify

potential factors causing an overall effect. Each cause or reason for imperfection is a source of variation

The possible causes are:

• Volume contraction of the metal, either from liquid contraction of the melt or from contraction during phase

change from liquid to solid

• Insufficient feed metal in defect areas.

• Improper Gating, feeding system and part design

• Aggressive mixing, Improper pouring, Moisture contamination, Improper ramming of mold box [8].

6.2. Casting Simulation

Not all defects can be accurately simulated. Solidification shrinkage defects (macro, micro and centerline

shrinkage) can be predicted fairly accurately. Flow-related defects (cold shuts and blow holes) can be

simulated but may not always match actual observations. Cooling stress related defects (cracks), micro-

structure and mechanical properties are difficult to simulate, and extensive calibration experiments may be

needed for practical use [3].

The figure 2.1 shows the systematic procedures that leads to casting simulation and ultimately to

optimization of the process.

6.3. Campbell’s 10 Rules for Making Reliable Castings

The guidelines for effective production of reliable castings continue to evolve. A significant increase and

improvement in the understanding of the casting process has led to new insights and criteria. Now ten rules

have been identified that incorporate the latest technology for the production of reliable castings.

Rule 1: Good-Quality Melt

Rule 2: Liquid Front Damage

Rule 3: Liquid Front Stop



Rule 4: Bubble Damage

Rule 5: Core Blows

Rule 6: Shrinkage Damage

Rule 7: Convection Damage

Rule 8: Segregation

Rule 9: Residual Stress

Rule 10: Location Points [10]

7. DEFECT ANALYSIS

As soon as the defect has been identified properly, all the causes must be studied in order to identify the

true root causes of the problem. Until and unless the causes of defect are identified, the problem cannot be

solved out. This should be a team effort that involves study of foundry related books, journals and advices

from foundry experts to uncover all possible contributions to know the reasons behind defect and the

mitigating factors that lead to corrective action.

The defect analysis involves the application of computer simulation technique in both existing and

modified pattern to achieve the objective. That’s why the stages of casting simulation technique have been

employed using ADSTEFAN software as follows:

• Step1: 3D Modeling of Hand wheel & Pattern

• Step 2: Meshing

• Step 3: Define Process for Filling

• Step 4: Material Properties setting

• Step 5: Fluid flow settings

• Step 6: Analysis in Filling

• Step 7: Analysis of solidification

• Step 8: Analysing result

The simulation program was installed at Abhishek Alloys, Belgaum. The material database was

defined with experiments to suit the melt used in the foundry. The experiments were carried out with shell

castings and pattern casting accompanied with various sizes of runner, Gating system and presence or

absence of feeder. A number of iterations were carried out by changing the size of runner, modifications in

gating system as well as riser.

The tests showed that the prediction & subsequently reduction of the casting defects depending on the

type of pattern by use of the ADSTEFAN simulation software. The difference in simulated porosities

between two pattern castings is shown as:

8. FOR EXISTING DESIGN

The 3D Modeling of existing Pattern is shown in figure 3.1. After, the model is fed to ADSTEFAN in the

form of a stp file from Solid Edge V19, meshing is performed. The casting method is set as Gravity

casting. The next step is to set the material properties giving the required parameters like material type

(FCD450), density (7.1 gm/cc for SG iron), Initial temp.(1450◦c), volumetric shrinkage (2%) and so on.

The fluid flow settings are set by software after setting fill ratio to 98% then; filling time is shown as

5.56sec. Analysis in Filling is shown in figure 3.2 wherein the uniform distribution of colour suggests no

presence of unwanted gases, slags, inclusions, dross etc. Also as shown in figure 3.3, the discontinuity in

the solidification suggests that certain defects may prevail in the hand wheel. Lastly, figure 3.4 shows the

result as analyzed by the simulation software. It is observed that the shrinkage defects are occurring in

central portion of hand wheels. It is also observed that defects occurred in two hand wheels differ in value



i.e. values of shrinkage defect are different. As shown in figure 3.4, the shrinkage that are significant for

study have value of 0.697cm3, 0.666cm

3 and 0.002cm

3 resp. Rest two values of shrinkage are insignificant.

Hence, by studying the possible causes of shrinkage defect and analysing the result of casting

simulation of existing pattern, the following remedies have been proposed with help from experts, manuals

and so on.

• Proper foundry practices, including melt preparation and mold design can reduce the occurrence of these

defects.

• Avoid heavy isolated casting sections that are difficult to feed.

• Design the part with a progressive change in casting thickness

• Design the gating and feeding system to provide for directional solidification back to the risers.

• Limit the pouring temperature so that the liquid contraction is minimized.

• Trial & error method in optimizing

• Runner height/length

• Inclusion of riser/feeder

9. MODIFIED DESIGN

Some of the changes carried out in pattern design are:

• Changing the size of runner: length reduced by 65mm.

• Changing the gating system: making the gating system symmetric as shown in figure 3.5 and adopting

circular shapes of the gates & ingates for feeding the molten metal.

• Introduction of the riser: Riser is placed just above the center of hand wheel as shown in figure.3.5 where

shrinkage defect was often found.

The steps involved till analysis in filling are similar to that of existing pattern design. Only filling time is

shown as 4.05sec. The figure 3.6 shows the uniform distribution of colour suggesting no presence of

unwanted gases, slags, inclusions, dross etc. As shown in figure 3.7, though there is some discontinuity in

solidification, the presence of feeder suggests that defects that may prevail in the hand wheel will be

minimized to a greater extent.

The occurrence of the shrinkage defects have been significantly reduced as shown in the figure 3.8.

The shrinkages that are significant for study are 0.00083cm3 and 0.00083cm

3 whereas rest two values are

insignificant. The shrinkage now shown is almost negligible and this hand wheel casting is ready for

production.

10. RESULTS AND DISCUSSIONS

The shrinkage porosity in existing design is

(Sp)1 =(0.697+0.666+.002)cm3=1.365 cm

3 (from figure 3.4)

The shrinkage in the Modified design is

(Sp)2=(0.00083+0.00083)cm3=0.00166 cm

3 (from figure 3.8)

Thus, reduction in shrinkage=99.8%

This doesn’t consider the shrinkage defects prevailing in places other than the hand wheel since the

metal casts are going to be reused & are insignificant for the Hand wheel castings. Thus, there is

significant reduction in the shrinkage defect by the use of modified design.

Considering single shell molds in which two hand wheel are casted, the yield is being calculated.

Density of Ductile iron=7100 kg/m3 [11]

For Existing Design

(Yield)1=(wt. of good casting/wt. of molten metal)*100%



=2.05/4.877*100%=60.75%

For Modified Design

(Yield)2=(weight of good casting/weight of molten metal)*100%

=2.05/3.374*100%=42.03%

Improvement in Yield=18.72%

Reduction in wt. of molten material/cast=4.877-3.374 =1.503kg

Thus, there is also the significant improvement in the yield by using the modified design. The weights

have been calculated from Solid Edge V19 using Physical properties option and for two hand wheels, the

yield has been calculated. As a whole, the use of the modified design has helped to reduce the shrinkage

defect significantly and improve the yield immensely by using the casting simulation software

“ADSTEFAN”. The significant reduction in material consumption has become a boon to the SMEs, thus

leading to profit increment.

Figure 1.1 Shrinkage Defect in Hand wheel

Figure 2.1 Flowchart of analysis of casting defects using casting simulation technique



Figure 3.1 3D Modeling of existing pattern

Figure 3.2 Analysis in Filling

Figure 3.3 Analysis of solidification



Figure 3.4 Analysing result

Figure 3.5 3D Modeling of modified Pattern

Figure 3.6 Analysis in Filling



Figure 3.7 Analysis of solidification

Figure 3.8 Analysing result

11. CONCLUSION

Casting simulation and fish bone diagram are of great essence in carrying out the defect analysis. By using

them, it has been possible to find out all possible causes, their effects & ultimately using that information

for simulation in casting simulation software “ADSTEFAN” to get desired result.

In practice, Casting defects are eliminated by iteratively designing casting filling (gating) system

through experience and experiments, but it requires large number of shop floor trials; taking huge amount

of resources (cost) and time.

With the introduction of Casting simulation software along with changes in the gating design, reducing

the runner length and using the feeder in pattern, it has helped to minimise the casting defects & rejections

as a whole. The proposed approach reduces the rejection due to casting defects in foundries, material

saving and reduction in per unit cost of production & increase in yield and ultimately profit.

Casting simulation technology thus, has become a powerful tool for casting defect troubleshoot in and

method optimization. It will reduce the lead time for the sample casting; improved productivity and

knowledge of software can be maintained for future use and for training new engineers.



12. FUTURE SCOPE

In order to continue with the defect analysis of casting, there are lots of fields for study. Some of them are

mentioned below:

• Study of the metallurgical failures, some other defects like sand drop, extra material deposits, shell crack etc

that are not taken into consideration during simulation.

• Study of the application of DOE methods for optimisation of various system parameters to minimise the

defects.

• Use of sleeves, chillers etc to minimise the casting defects and uniform solidification

• Use of pattern less technology for the casting simulation by use of the latest casting simulation software’s

like solid cast, flow3d etc.

ACKNOWLEDGEMENTS

The author wishes to thank all Professors for their suggestions, encouragement and support in undertaking

the present work. Also, the author would like to express our gratitude to A.S. Kulkarni, Proprietor, P. M.

Kulkarni, QA, Matruchaya Engineering. Madhav Acharya, MD, R.D. Rathore, QA senior engineer,

Abhishek Alloys, Belgaum deserve special thanks for their continuous help & support in carrying out the

work successfully.

REFERENCES

[1] E. Paul DeGarmo, J. T. Black, Ronald A. Kohser (2003), “Materials and Processes in Manufacturing”

(9th ed.), Wiley, ISBN 0-471-65653-4.pg 277

[2] Swapnil A. Ambekar, Dr. S. B. Jaju, “A Review on Optimization of Gating System for Reducing

Defect”, International Journal of Engineering Research and General Science Volume 2, Issue 1, January

2014,ISSN 2091-2730

[3] Dr. B. Ravi, “Casting Simulation-Best Practices”, transactions of 58th IFC, Ahmedabad (2010)

[4] Bhupendra J. Chudasama, “Solidification Analysis and Optimization Using Pro-Cast”, International

Journal of Research in Modern Engineering and Emerging Technology Vol. 1, Issue: 4, MAY: 2013

(IJRMEET) ISSN: 2320-6586

[5] Vipul Vasava, Dhaval Joshi, “Simulation of shrinkage Defect-A Review”, International Journal of

Engineering Trends and Technology (IJETT) – Volume 4 Issue 6- June 2013, ISSN: 2231-5381

[6] A. Harshwardhan Pandit, B. Uday Dabade, “Optimisation: Need of today’s Competitive Age A Case

Study on Simulation using Autocast”, International Conference on Current Trends in Technology,

‘nuicone – 2011

[7] Yeh-Liang Hsu, Chia-Chieh Yu, “Computer Simulation of Casting Process of Aluminium Wheels – A

Case Study”, JEM381 imeche 2006 Proc. Imeche Vol. 220 Part B: J. Engineering Manufacture

[8] Ishikawa, Kaoru (1956), “Guide to Quality Control”, Tokyo: JUSE.

[9] Aniruddha Joshi, Pritam Kadam, “An Application of Pareto Analysis and Cause Effect Diagram for

Minimization of Defects in Manual Casting Process”, Proceedings of Annual International Conference

IRAJ, 19th January 2014, Pune India. ISBN: 978-93-82702-54-2

[10] Campbell, John (2004), “Castings Practice – The 10 Rules of Castings”.

[11] http://www.iron-foundry.com/ductile-iron-density.html

[12] Vasdev Malhotra and Yogesh Kumar, “Casting Defects: An Literature Review”. International Journal

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Documents

DEFECT ANALYSIS OF HAND WHEEL CASTING … Regmi Assistant Professor, Nepal College of Information Technology, Kathmandu ABSTRACT In the present casting arena, emphasis is laid on the