Extrusion
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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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Extrusion

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Extrusion

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


Extrusion

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

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


Injection molding process

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


Molds

Molds

  • Cold runner, Two-plate mold

  • Cold runner, Three-plate mold

  • Hot runner mold


Machine

Machine

  • 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

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

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

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

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

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

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

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

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

19.12 Processing Elastomers

Processing elastomers uses processes similar to shaping thermoplastics

These include:

Extrusion (tubing, hoses, molding)

Injection molding (components for automobiles


Calendering

Calendering

  • 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


Dipping

Dipping

  • Process:

    • Dip metal form into a liquid elastomer compound

    • Compound adheres to form, creating item

  • Uses:

    • Rubber gloves


19 13 processing polymer matrix composites

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


Prepegs

Prepegs

  • 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

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

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

Compression Molding

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


Vacuum bag molding

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

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

(b)

(a)

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


Pultrusion

Pultrusion

  • 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)


Pulforming

Pulforming

  • 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

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

wheel


Extrusion

  • 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)

Tungsten-Carbide

tools


Extrusion

  • 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

Chapter 20 Rapid Prototyping

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

  • Additive, subtractive and virtual.


20 3 additive processes

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

(a)

(a)

Fuse-deposition Modeling


Stereolithography

Stereolithography


Selective laser sintering

Selective Laser Sintering


Selective laser sintering1

Selective Laser Sintering


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