Thermoset Plastic Molding Services

Cuyahoga Plastics has been molding various types of thermoset materials on a contract basis for many years.

Our injection presses are equipped to handle both granular and “dough” type materials (BMC’s).

The 52 presses located in our molding plant range in size from 50 tons to 500 tons clamp capacity, some with large size platens. We often become involved in projects at the “idea stage” and carry them on through tool design and procurement, then into final part production mode.

Insert molding is a common process for us.

Examples of the specific types of materials we mold are:

• Phenolics 
• BMC’s (reinforced thermoset polyesters)
• Epoxies
• SMC’s (sheet molding compound)
• Silicones
• Melamines
• Ureas
• DAP’s

We utilize the following processes to mold all brands and types of thermoset molding materials:

• Compression Molding
• Transfer Molding
• Injection Molding

Mold building suggestions and basic process guide for using Cuyahoga Plastics polyester BMC (Bulk Molding Compound)

Compression Molding Tool

• Mold base: DME #2 or equivalent
• Preferred Cavity Construction: full positive with vertical parting line flash
• Sub landed mold: a short horizontal land (.250) then transition vertical
• Landed: allow for ample venting area and consider a vacuum
• Cavity and core material: Hardened tool steel (48-56Rc)
• Finish: SPI#3 plus diamond draw polish (400 stone)
• Coating: Chrome plate or TiN
• Mold release agent: carnauba wax or thermoset mold release spray

Transfer Molding Tool

• Same as compression mold with the addition of hardened runner block and “sucker pin” under
• Transfer striker plate (also hardened).
• Vacuum recommended.

Injection Molding Tool

• As above compression mold with the addition of hardened runner block and gates and gate shut off pins.
• Cold sprue bushing and vacuum recommended.

Compression Molding Parameters
Mold temperature: 305-350ºF
Cavity Pressure: 1000-2000 PSI

Preheat temperature: 150 – 180 deg. F (can use microwave oven)
Preheating is not necessary but is recommended to pre-plasticize material.
This promotes better flow and can reduce cycle time.

Close time: 1-3 seconds for small parts / 3-5 seconds for medium / 4-7 seconds for large
Cycle time: 60 seconds or less for small parts / 60 seconds to 180 seconds for medium / 180 or more for large

Transfer Molding Parameters
Mold temperature: 305-350ºF
Transfer pressure: 400 PSI or more if needed

Preheat temperature: 150 – 180 deg. F (can use microwave oven)
Preheating is not necessary but is recommended to pre-plasticize material.
This promotes better flow and can reduce cycle time.

Transfer time: 2-5 seconds for small parts / 3-8 seconds for medium / 4-10 seconds for large
Cycle time: 60 seconds or less for small parts / 60 seconds to 180 seconds for medium / 180 or more for large

Injection Molding Parameters
Mold temperature: 305-350ºF
Barrel temperature: 150ºF

Injection pressure: 500 to 1000 psi (has a low viscosity when plasticized) Injection time: 1-2 seconds for small parts and 3-8 for medium Hold pressure: 500 psi or below Back pressure (or plasticizing pressure if you will): 25 – 75 psi

Screw RPM to match back fill at desired pressure

Extrudate temperature (injecting material through nozzle): 180 – 190 deg F and can go up to 215 deg F