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Emilian Popa Injection Molding Design Guide Manual 2012
Compression and Transfer Molding
Compression Molding
Compression Molding
- Change is placed in cavity of matched mold in the open position
- Mold is closed by bring the two halves together.
- Pressure is exerted to squeeze the resin so that it fills the mold cavity
- While under pressure the mold is heated which cures the resin
o Thermosets
Compression Molding
- Mold closure types- Flash
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Emilian Popa Injection Molding Design Guide Manual 2012
Compression Molding
- Standard thermosets of various types- Molding compounds (mixtures of materials)
o
Thermoset resin (30%)o Reinforcement fibers (10%)
o Fillers (60%0
- Bulk Molding Compound (BMC)- Sheet Molding Compound (SMC)
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Emilian Popa Injection Molding Design Guide Manual 2012
Compression Molded Parts
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Emilian Popa Injection Molding Design Guide Manual 2012
SMC Equipment
Sheet Molding Compound Compression Molding
- Change is made up from thermoset materials
- Charge is rolled flat
- Multiple layers of SMC can be used in a mold- Longer fibers than BMC
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Emilian Popa Injection Molding Design Guide Manual 2012
Compression Molding
- Compression molded parts
o Total force needed per part is determined by:
Projected area of the part (A)
Required cavity pressure for the resin (PA)
Pressure factor that accounts for depth ()
Depth in excess of the minimum amount (de)
Compression Molding
- Compression molding machineso Total force that can be exerted is called:
Press capacity
Machine rating
Machine size
Rated in Newtons or Tons
o Determined by the area of the hydraulic ram and the hydraulic pressure in the line.
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Emilian Popa Injection Molding Design Guide Manual 2012
Compression Molding vs Injection Molding
Transfer Molding
- Mixed resin is placed in the transfer chamber- Resin is heated to liquid state
- Plunger presses liquid resin through sprue and runner system to mold cavities.
- Mold is heated- After resin is cured, parts are removed
Transfer Molding
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Emilian Popa Injection Molding Design Guide Manual 2012
Product Considerations
- Practically all thermosets can be compression or transfer molded
o Liquids
o Pastes
Liquid resin with filler
o Doughs
Pastes with reinforcement
o Granules
B-staged resin (phenolics)
o Preforms
Granules pressed into a pre-measured shape for easier handling
Cold Forming, Sintering and Ram Extrusion
- Used where heat processing is difficult or impossible
- High pressures- Lower temperatures
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