Ch 6 METBD 470

Chapter 9 – Plastic and Polymer Composite Fabrication Processes

1. Injection Molding (or compression or transfer)2. Extrusion3. Thermo-Forming4. Blow Molding (injection blow molding with

preforms or extrusion blow molding with parison)

5. Rotational Molding (combination of 3 and 4)

Ch 6 METBD 470

Ch 6 METBD 470

Molding Processes for PE:

Molding Processes for Nylon (30% GF):

© MFA and DC 2005

Desired Batch Size

Screen on batch size*

*Using the CES EduPack Level 2 DB

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its)

1

10

100

1000

10000

100000

1e+006

1e+007

1e+008

Blow Moulding

Powder methods

Injection Moulding

Sheet forming

Die Casting

Compression Moulding

Expanded foam molding

Rotational Moulding

Rolling and forging

Resin transfermolding (RTM)

Electro-discharge machining

Thermoforming Rapid prototyping

Lay-Up methods

Sand castingPolymer Casting

Economic batch size

Demo: the Process data-table

Ch 6 METBD 470

You Tube Videos:

Blow Molding: http://www.youtube.com/watch?v=vSabFFQUr9E&feature=related

Extrusion: http://www.youtube.com/watch?v=kpPS6S_EB4Q

Injection: http://www.youtube.com/watch?v=bit-D1NnfjI&videos=BeAyHeQIsiY&playnext_from=TL&playnext=1

Thermoforming: http://www.youtube.com/watch?v=NPLWxxyIJcE

Ch 6 METBD 470

• Injection Molding – most common (60-70%)– Process

Plastic pellets are heated in the injection unit and forced through a runner system/gate(s) into a cavity in a mold.

Batch Process

Ch 6 METBD 470

• Injection Molding – Equipment

• Clamping Unit (Ejection System)• Injection (Plasticating) Unit• Frame

Ch 6 METBD 470

• Injection Molding –Main functions of Plasticating unit

1.Convey solid material/melt

1.Mix to produce homogeneous melt

1.Melt material– Range of 300º F (PVC) to 740º F (Polysulphone)

1.Develop pressure for injection

Ch 6 METBD 470

• Injection Molding –Materials•Both amorphous and semi-crystalline are done easily•Narrow molecular weight distribution

•With modifications to the equipment – thermoset materials and liquid Silicone can be used

Ch 6 METBD 470

• Injection Molding –Parts•Three dimensional •Can be very complex•Multiple cavitation is common (128 cavities)

Ch 6 METBD 470

• Injection Molding –Tooling - Molds

•Generally steel, but some Aluminum tooling is used•High pressure process – molds are ‘beefy’

– Plastic pressures around 30,000 psi– Weight – LXWXH/4 (in inches)

•Tooling is expensive and can take a long time to create

Ch 6 METBD 470

• Extrusion –ProcessPlastic pellets or powders are heated in a

plasticating unit and the melt is forced through a forming die.

Continuous Process

Ch 6 METBD 470

•Extrusion – Equipment

• Injection (Plasticating) Unit• Frame

Ch 6 METBD 470

• Extrusion –Materials•Both amorphous and semi-crystalline are done easily•Wide molecular weight distribution

Ch 6 METBD 470

• Extrusion–Parts•Two dimensional

– Sheet– Hoses– Line– Rod

– Vinyl siding– Pipes

Ch 6 METBD 470

• Extrusion–Tooling - Dies

•Generally steel – Aluminum is common though•Low pressure process

– Tooling can be expensive– Shorter lead times

Ch 6 METBD 470

• Thermoforming–ProcessSheet is heated and formed to the desired shape

Can be a batch or continuous process

Some consider Thermoforming to be a secondary process because the material needs to be formed into sheet prior to being thermoformed.

Ch 6 METBD 470

• Thermoforming–Process

Ch 6 METBD 470

• Thermoforming–Process

Ch 6 METBD 470

• Thermoforming–Process

Ch 6 METBD 470

•Thermoforming– Equipment

• Heating unit• Vacuum unit• Tool or die

Ch 6 METBD 470

• Thermoforming –Materials•Both amorphous and semi-crystalline are done

– Semi-crystalline are more difficult

•Wide molecular weight distribution

Ch 6 METBD 470

• Thermoforming–Parts•Three dimensional •Generally simple shapes

Ch 6 METBD 470

• Thermoforming–Tooling – Dies or molds

•Generally Aluminum, but prototypes are commonly made epoxy, wood, plaster, and composite materials•Low pressure process

– Tooling is relatively inexpensive– Shorter lead times

Ch 6 METBD 470

• Blowmolding–Process–2 basic types

•Extrusion Blow Molding–consists of an extruder that melts the plastic and forms it into a

molten tube called a parison. Die closes around parison which seals both ends. Blow pin is insereted and inflates the parison to assume the contoru of the die. See http://www.youtube.com/watch?v=RcXB0NbbQzg&feature=related

•Injection Blow Molding (large volumes)–Uses preforms - The preform is transferred on a metal shank, called

the core rod and into a blow mold.

Ch 6 METBD 470

Blowmolding Equipment• Depends on type of blowmolding

you are doing– Extrusion

» Extruder» Dies and Blowpins» Clamping system

– Injection» Preforms (Injection molding

machine)» Heating unit» Blowing machine

Ch 6 METBD 470

• Blowmolding –Materials•Both amorphous and semi-crystalline are done

– Semi-crystalline are more difficult– Highly Crystalline materials (Nylon) are very difficult

•Wide molecular weight distribution

Ch 6 METBD 470

• Blowmolding–Parts•Three dimensional •Generally simple shapes•Hollow•May need trimmed

Ch 6 METBD 470

• Blowmolding–Tooling – Dies or tools

•Generally Aluminum (some may have brass inserts)

– Steel Pinchoff areas

•Low pressure process – Tooling is relatively inexpensive– Shorter lead times