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Extrusion - PowerPoint PPT Presentation

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Extrusion. A typical extruder. Extrusion is the method that produces the largest volume of plastic products. Extruded products are generally long uniform and solid or hollow complex cross-sections. Sheet and Film Extrusion. Other types: Tubing, Electrical wire coating, Pipes.

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A typical extruder.

Extrusion is the method that produces the largest volume of plastic products

Extruded products are generally long uniform and solid or hollow complex cross-sections

Sheet and Film Extrusion

Other types: Tubing, Electrical wire coating, Pipes

To extrude thin film, air is forced into an extruded sheet and then either pinched or cut.

A common dye to produce sheets is referred to as the coathanger dye.

Injection Molding

Injection molding is similar to extrusion only a mold replaces the die.

Injection Molding Process

  • The polymer is pushed into the mold.

  • The part is cooled within the mold.

  • Once cooled, the part is eased out of the mold with ejector pins


  • Cold runner, Two-plate mold

  • Cold runner, Three-plate mold

  • Hot runner mold


  • Cost range: $85,000 - $140,000

  • Die cost: $20,000 - $200,000

  • Mold cost: approx. $100,000

  • Process: 5 sec. – 60 sec.

Extrusion Blow Molding

A polymer is extruded and clamped within a mold. Air is then pushed is and the part is made. The mold is removed and excess pieces are removed as well.

Injection Blow Molding

The polymer is injected into a closed mold with a blow pin and parison. Air is blown in and the part is made. The blow pin is then removed.

19.6 - Thermoforming

  • Sheets available in multitude of sizes, thicknesses, and fillers (to create specific properties).

  • Parts cannot include holes and openings.

  • Material: thermoplastics, must exhibit high, uniform elongation

  • Packaging trays, signs, appliance housings, refrigerator liners, shower stalls

19.7 – Compression Molding

  • Done at temperatures of 200 C (400 F) and higher

  • Pressures range from 1400- 22000 psi

  • Material: usually thermosetting plastics, sometimes thermoplastics

  • Cures in die

  • Dishes, handles, container caps, fittings, electrical components, housings

  • Fiber reinforced parts with chopped fibers use this process exclusively.

19.8 -Transfer Molding

  • Pressures may reach 43,000 psi

  • Viscous flow also raises temperature and homogonizes material

  • High complexity and dimensional control

  • More expensive

19.9 - casting

  • Thermosets and thermoplastics may be used

  • Slow and simple yet cheap

  • Flexible molds can be used

  • Continuous casting can be used

  • Centrifugal casting

  • Potting and encapsulation (electrical components)

19.10- foam molding

  • Polystyrene beads are the raw material.

  • Beads, blowing agent, and heat

  • Pre-expanded beads may be shaped just as plastics

  • Structural foam molding created hard outer shell and light cellular core, outside is cooled rapidly

  • Polyurethane foam processing utilizes chemical reactions to create foam which is poured into molds or sprayed on surfaces for insulation.

19.11- cold forming and solid phase forming

  • Many of the cold working processes that apply to metals can also be used on plastics.

  • Thermosets are used because of their ductility at room temperature.

  • Advantages: strength, toughness, improved dimensional accuracy, and faster cycle times

  • Solid phase forming is carried out at temperatures 10-20 C. Below the melting point.

19.12 Processing Elastomers

Processing elastomers uses processes similar to shaping thermoplastics

These include:

Extrusion (tubing, hoses, molding)

Injection molding (components for automobiles


  • Used to form rubber and thermoplastic sheets.

  • Process:

    • Warm mass fed into series of rolls to create a flat sheet

    • End product usually 0.3 to 1mm thick

  • Uses:

    • Tines

    • Belts for machinery


  • Process:

    • Dip metal form into a liquid elastomer compound

    • Compound adheres to form, creating item

  • Uses:

    • Rubber gloves

19.13 Processing Polymer-Matrix Composites

  • Polymer-matrix composites are also known as reinforced plastics

  • Special methods required to shape due to complex structure:

    • Molding

    • Filament winding

    • Pultrusion

    • Pulforming

Motorcycle parts made of reinforced plastics


  • Process: continuous fibers aligned and subjected to surface treatment, then dipped into a resin bath to form a tape

  • Uses: flat architectural panelling

  • Example of use: F-14 fighter jet horizontal stabilizer

F-14 fighter jet

Sheet-Molding Compound (SMC)

  • Process: continuous fibers cut into short fibers and deposited in random orientation over layers of resin paste

  • Use: random orientation gives the product strength in many directions, instead of just one, like in unidirectional fiber products

Molding of Reinforced Plastics

  • Different types of molding used for reinforced plastics:

    • Compression molding

    • Vacuum bag molding

    • Contact molding

Mold for hull of a catamaran

Compression Molding

  • Process: Polymer-Matrix composite is placed between two molds and compressed

Vacuum-Bag Molding

  • Process: material is placed in a mold, covered by a plastic bag, and a vacuum is created to compress the material into the shape of the mold

Contact Molding

  • Two types:

    • Spray Lay-up: spray into mold evenly to the thickness desired

    • Hand Lay-up: painted onto the mold

Jet ski hull made by hand lay-up



Filament Winding

  • Resin and fibers are combined at curing

  • Process: fiber wound on a rotating mandrel while within resin bath.

  • Benefits: very strong and heavily reinforced

  • Uses: Aircraft (engine ducts, propellers), spherical pressure vessels


  • Process: prepeg pulled through resin bath, heated in a die, and but to length after sufficient cooling time

  • Uses: parts with uniform cross-sections that are made continuously (aluminum ladders)


  • Process: similar to pultrusion

    • Prepeg pulled through resin bath, then clamped between two halves of die. Cut piece and repeat.

  • Uses: parts with non-uniform cross-section

19.14 Processing Metal-Matrix and Ceramic-Matrix Composites

  • Metal-Matrix Composites (MMC)

    • Liquid-phase processing

    • Solid-phase processing

    • Two-phase (liquid-solid) phase processing

  • Ceramic-Matrix Composites (CMC)

    • Slurring infiltration

Ceramic-matrix turbine


  • Liquid-Phase Processing:

    • Casting together liquid material (ex. Aluminum) and solid reinforcement (ex. Graphite)

  • Solid-Phase Processing:

    • Consists of powder metallurgy techniques.

    • Proper mixing important to obtain even distribution of fibers (ex. Tungsten-carbide tools)



  • Two-phase processing

    • Involves liquid and solid states

    • Reinforcing fibers are mixed with a matrix that contains liquid and solid phases of the metal

  • Slurry infiltration

    • Slurry: mixture of matrix powder, carrier liquid, and organic binder

    • Prepare a fiber preform, and hot press it with the slurry

Chapter 20 Rapid Prototyping

  • Produces and example of a part from a CAD drawing before production.

  • Additive, subtractive and virtual.

20.3 Additive Processes

  • Parts are broken down into layers and constructed slice by slice, usually .004-.020 in. thick.

  • Stereolithography, fuse-deposition modeling, ballistic-particle manufacturing, three-dimensional printing, selective laser sintering and laminated-object manufacturing.



Fuse-deposition Modeling


Selective Laser Sintering

Selective Laser Sintering

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