plastic_fabrication processes

1. Ch 6 METBD
470
Chapter 9 – Plastic and Polymer
Composite Fabrication Processes
1. Injection Molding (or compression or transfer)
2. Extrusion
3. Thermo-Forming
4. Blow Molding (injection blow molding with
preforms or extrusion blow molding with parison)
5. Rotational Molding (combination of 3 and 4)

2. Ch 6 METBD
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3. Ch 6 METBD
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Molding Processes
for PE:
Molding Processes for
Nylon (30% GF):

4. © MFA and DC 2005
Desired
Batch Size
Screen on batch size*
*Using the CES EduPack Level 2 DB
Economicbatchsize(units)
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 transfer
molding (RTM)
Electro-discharge machining
Thermoforming Rapid
prototyping
Lay-Up
methods
Sand casting
Polymer Casting
Economic batch size
Demo: the Process data-table

5. Ch 6 METBD
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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

6. Ch 6 METBD
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• 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

7. Ch 6 METBD
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• Injection Molding
– Equipment
• Clamping Unit (Ejection System)
• Injection (Plasticating) Unit
• Frame

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• 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

9. 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

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

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• 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

12. Ch 6 METBD
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• Extrusion
–Process
Plastic pellets or powders are heated in a plasticating
unit and the melt is forced through a forming die.
Continuous Process

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• Extrusion
– Equipment
• Injection (Plasticating) Unit
• Frame

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

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• Extrusion
–Parts
•Two dimensional
– Sheet
– Hoses
– Line
– Rod
– Vinyl siding
– Pipes

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• Extrusion
–Tooling - Dies
•Generally steel – Aluminum is common though
•Low pressure process
– Tooling can be expensive
– Shorter lead times

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• Thermoforming
–Process
Sheet 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.

18. Ch 6 METBD
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• Thermoforming
–Process

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• Thermoforming
–Process

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• Thermoforming
–Process

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• Thermoforming
– Equipment
• Heating unit
• Vacuum unit
• Tool or die

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• Thermoforming
–Materials
•Both amorphous and semi-crystalline are done
– Semi-crystalline are more difficult
•Wide molecular weight distribution

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• Thermoforming
–Parts
•Three dimensional
•Generally simple shapes

24. Ch 6 METBD
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• 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

25. Ch 6 METBD
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• 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.

26. Ch 6 METBD
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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

27. Ch 6 METBD
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• 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

28. Ch 6 METBD
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• Blowmolding
–Parts
•Three dimensional
•Generally simple shapes
•Hollow
•May need trimmed

29. Ch 6 METBD
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• 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