Ch19 forming shaping

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Chapter 19Forming and Shaping Plastics and

Composite Materials


Characteristics of Forming and Shaping Processesfor Plastics and Composite Materials


Forming and Shaping Processes for Plastics, Elastomers, andComposite Materials

Figure 19.1 Outline of forming and shaping processes for plastics, elastomers, and compositematerials. (TP = Thermoplastics; TS = Thermoset; E = Elastomer.)


Extruder Schematic

Figure 19.2 (a) Schematic illustration of a typical screw extruder. (b) Geometry of anextruder screw. Complex shapes can be extruded with relatively simple and inexpensive dies.


Extrusion Die Geometries

Figure 19.3 Common extrusion die geometries: (a) coat-hanger die for extruding sheet;(b) round die for producing rods; and (c) dies for producing square cross-sections. Notethe nonuniform recovery of the part after it exits the die. Source: (a) Encyclopedia ofPolymer Science and Engineering (2nd ed.). Copyright © 1985. Reprinted by permissionof John Wiley & Sons, Inc.


Extrusion ofTubes

Figure 19.4 Extrusion of tubes.(a) Extrusion using a spider die(see also Fig. 15.8) andpressurized air. (b) Coextrusionfor producing a bottle.


Production of Plastic Film and Bags

Figure 19.5 (a) Schematic illustration of the production of thin film and plastic bags fromtube – first produced by an extruder and then blown by air. (b) A blown-film operation. Thisprocess is well developed, producing inexpensive and very large quantities of plastic film andshopping bags. Source: Courtesy of Windmoeller & Hoelscher.

(b)


Melt-SpinningProcess

Figure 19.6 The melt-spinning processfor producing polymer fibers. The fibersare then used in a variety ofapplications, including fabrics and asreinforcements for composite materials.


Injection Molding

Figure 19.7 Schematicillustration of injection moldingwith (a) plunger and (b)reciprocating rotating screw.


Injection Molding Sequence

Figure 19.8 Sequence of operations in the injection molding of a part with a reciprocatingscrew. This process is used widely for numerous consumer and commericial products,such as toys, containers, knobs, and electrical equipment (see Fig. 19.9).


Products Made by Injection Molding

Figure 19.9 Typical products made by injection molding, including examples of insertmolding. Source: (a) Courtesy of Plainfield Molding, Inc. (b) Courtesy of Rayco Mold andMfg. LLC.

(b)(a)


Mold Features for Injection Molding

Figure 19.10 Illustration of mold features for injection molding. (a) Two-platemold with important features identified. (b) Four parts showing details and thevolume of material involved. Source: Courtesy of Tooling Molds West. Inc.


Types of Molds used in Injection Molding

Figure 19.11 Types of molds used in injection molding: (a) two-plate mold; (b) three-platemold; and (c) hot-runner mold.


EPOCH Hip Stem

Figure 19.12 The EPOCH hip stem. Thisdesign uses a PAEK (polyaryletherketone)layer and bone-ingrowth pad around acobalt-chrome core in order to maximizebone ingrowth. Source: Courtesy ofZimmer, Inc.

Figure 19.13 An EPOCH hip isremoved from the mold after aninsert injection-molding operation.Source: Courtesy of Zimmer, Inc.


Injection-Molding Machine

Figure 19.14 A 2.2-MN (250-ton) injection molding machine. The tonnage is theforce applied to keep the dies closed during the injection of molten plastic into themold cavities and hold it there until the parts are cool and stiff enough to be removedfrom the die. Source: Courtesy of Cincinnati Milacron, Plastics Machinery Division.


Reaction-Injection Molding Process

Figure 19.15 Schematic illustration of the reaction-injection moldingprocess. Typical parts made are automotive-body panels, water skis,and thermal insulation for refrigerators and freezers.


Blow-Molding

Figure 19.16 Schematic illustrations of(a) the extrusion blow-molding processfor making plastic beverage bottles; (b)the injection blow-molding process;and (c) a three-station injectionmolding machine for making plasticbottles.


RotationalMolding Process

Figure 9.17 The rotational molding(rotomolding or rotocasting)process. Trash cans, buckets, andplastic footballs can be made bythis process.


Thermoforming Process

Figure 19.18 Various thermoforming processes for a thermoplastic sheet. These processescommonly are used in making advertising signs, cookie and candy trays, panels for showerstall, and packaging.


Compression Molding

Figure 19.19 Types of compression molding – a process similar to forging: (a) positive,(b) semipositive, and (c) flash, which is later trimmed off. (d) Die design for making acompression-molded part with external undercuts.


Transfer Molding

Figure 19.20 Sequence of operations in transfer molding for thermosetting plastics.This process is suitable particularly for intricate parts with varying wall thickness.


Processes for Plastics and Electrical Assemblies

Figure 19.21 Schematic illustration of (a) casting, (b) potting, and (c) encapsulationprocesses for plastics and electrical assemblies, where the surrounding plastic serves as adielectric.


Calendering

Figure 19.22 Schematic illustration of calendering. Sheets produced by thisprocess subsequently are used in thermoforming. The process also is used inthe production of various elastomer and rubber products.


Motorcycle Components

Figure 19.23 Reinforced plastic components for a Honda motorcycle. Theparts shown are front and rear forks, rear swing-arm, wheel, and brake disks.


Tapes used in MakingReinforced Plastic Parts

Figure 19.24 (a) Manufacturing process for polymer-matrix composite tape. (b) Boron-epoxy prepreg tape. These tapes are then used in making reinforced plastic parts andcomponents with high strength-to-weight ratios, particularly important for aircraft andaerospace applications and sports equipment. Source: (a) Courtesy of T. W. Chou, R. L.McCullough, and R. B. Pipes. (b) Courtesy of Avco Specialty Materials/Textron.

(b)


Tape and Tape-Laying System

(b)(a)

Figure 19.25 (a) Single-ply layup of boron-epoxy tape for the horizontal stabilizer for anF-14 fighter aircraft. (b) A 10-axis computer-numerical-controlled tape-laying system.This machine is capable of laying up 75- and 150-mm (3- and 6-in.) wide tapes oncontours of up to +/- 30 degrees and at speeds of up to 0.5m/s (1.7 ft/s). Source: (a)Courtesy of Grumman Aircraft Corporation. (b) Courtesy of The Ingersoll MillingMachine Company.


Production of Fiber-Reinforced Plastic Sheets

Figure 19.26 Schematic illustration of the manufacturing process for producing fiber-reinforced plastic sheets. The sheet still is viscous at this stage and later can be shpedinto various products. Source: After T. W. Chou, R. L. McCullough, and R. B. Pipes.


Vacuum-Bag Forming and Pressure-Bag Forming

Figure 19.27 Schematic illustration of (a) vacuum-bag forming, and (b) pressure-bag forming.These processes are used in making discrete reinforced plastic parts. Source: After T. H.Meister.


Open-Mold Processing

Figure 19.28 Manual methods of processingreinforced plastics: (a) hand lay-up, and (b)spray lay-up. Note that, even though theprocess is slow, only one mold is required.The figures show a female mold, but malemolds also are used. These methods alsoare called open-mold processing. (c) A boathull made by these processes.


Filament-Winding

(b)

Figure 19.29 (a) Schematic illustration of the filament-winding process; (b) fiberglass beingwound over aluminum liners for slide-raft inflation vessels for the Boeing 767 aircraft. Theproducts made by this process have high strength-to-weight ratio and also serve aslightweight pressure vessels. Source: Courtesy of Brunswick Corporation.


Pultrusion

Figure 19.30 (a) Schematic illustration of the pultrusion process. (b) Examples ofparts made by pultrusion. The major components of fiberglass ladders (usedespecially by electricians) are made by this process. Unlike aluminum ladders, theyare available in different colors but are heavier because of the presence of glass fibers.Source: Courtesy of Strongwell Corporation.

(b)


Design Modifications to Minimize Distortion in Plastic Parts

Figure 19.31 Examples of design modifications to eliminate or minimize distortion inplastic parts: (a) suggested design changes to minimize distortion; (b) stiffening thebottoms of thin plastic containers by doming – a technique similar to the processused to shape the bottoms of aluminum beverage cans; and (c) design change in arib to minimize pull-in (sink mark) caused by shrinkage during the cooling of thicksections in molded parts.


Production Characteristics of Molding Methods