Compression Molding

Thermosets.
Silicones.
Large structural.

Q: Production economics?

Compression molding sweet spot: 500-10,000 parts annually. Below 500: CNC or casting often cheaper. Above 10,000: injection molding typically better (faster cycle, lower per-part cost). For complex thermoset parts, compression remains optimal across all production volumes because thermosets cannot be injection molded.

Q: Lead times?

Compression mold tooling: 6-10 weeks. First article production: 1-2 weeks after tool. Production delivery: 2-4 weeks per order. Compression molding cycle times are slower than injection — 2-15 minute cure times mean lower per-day output. Plan longer lead times for compression programs vs injection programs.

Compression molding for thermoset materials not suitable for injection molding. Phenolic, epoxy, polyester thermosets. Silicone rubber (HTV). Composite SMC/BMC for structural applications. Larger part sizes possible, lower tooling cost than injection.

Compression Molded Quote Rapid injection molding

Thermoset + silicone Larger than IM Lower tooling cost Structural composites

01 · Compression molding materials

Compression molding material families.

Compression molding handles materials injection molding cannot — particularly thermosets that cure rather than melt, and very large parts beyond injection press size.

Phenolic

Historic thermoset

Phenol-formaldehyde molding for electrical insulators, automotive brake linings, ashtrays, and kitchen appliance handles.

Epoxy

Structural thermoset

Epoxy compression molded parts for aerospace, electrical insulation, high-temperature applications.

Polyester (unsaturated)

Building products

Low-cost thermoset for building components, bathroom fixtures, automotive body panels.

Silicone HTV

High-temp elastomer

High-temperature vulcanized silicone for gaskets, seals, baby products, medical grade.

EPDM rubber

Weather-resistant

EPDM rubber for automotive weather strips, outdoor seals, roofing.

SMC

Sheet molding compound

Pre-impregnated glass-reinforced polyester for automotive panels, electrical enclosures.

BMC

Bulk molding compound

Bulk-form glass-polyester for complex geometry. Electrical, automotive, industrial.

Melamine

Decorative thermoset

Decorative laminate molding for consumer products, tableware, industrial surfaces.

02 · Compression molding applications

Where compression molding wins.

Electrical insulators

Phenolic and polyester electrical insulators for transformers, switchgear

Automotive body panels

SMC body panels for specialty vehicles — lighter than steel, cheaper than carbon fiber

Silicone gaskets

Custom silicone gaskets too large for injection molding tooling

Appliance handles

Phenolic handles for cookware, laundry appliances — heat resistant

Brake linings

Asbestos-free brake friction materials molded from phenolic composite

Electrical switchgear

Arc chutes, insulator plates in switchgear — thermoset required

Bathroom fixtures

Vanity tops, shower pans in cultured marble (polyester composite)

Ammunition shells

Phenolic shotgun shells — combustible at specific temperature

Billiard balls

Phenolic billiard balls — dimensional stability and specific weight

FAQ

Compression Molded questions.

Injection molding: thermoplastic melts in barrel, injects into cold mold, cools and solidifies. Cycle 20-90 seconds. Compression molding: material placed in heated mold, pressed, cures via heat + time. Cycle 2-15 minutes. Injection is faster, lower cost for high volume, limited to thermoplastics. Compression handles thermosets, has lower tooling cost, allows larger parts, lower volume economics.

Thermosets offer: higher heat resistance (phenolic: continuous 150°C; thermoplastics: 80-130°C typical). Better chemical resistance for some chemistries. Higher stiffness at elevated temperature. Better electrical insulation. Cannot be remelted (once cured, stays cured). For heat-critical, structural, or electrical applications where thermoplastics reach their limits, thermosets extend capability.

Compression mold tooling: $5,000-20,000 for typical parts. Injection mold tooling: $15,000-80,000. Compression tooling simpler (no runners, no gates, less complex design). Lower tooling cost makes compression economical at lower volumes — below 1,000 pieces annually. For higher volume, injection molding amortizes faster.

Compression molding handles larger parts than injection: up to 2m × 2m practical maximum. Injection molding limited by press size and clamp tonnage — typically < 1m in any dimension without massive machines. For large parts (automotive body panels, bathroom fixtures, industrial covers), compression molding enables sizes impossible for injection.

Compression molding sweet spot: 500-10,000 parts annually. Below 500: CNC or casting often cheaper. Above 10,000: injection molding typically better (faster cycle, lower per-part cost). For complex thermoset parts, compression remains optimal across all production volumes because thermosets cannot be injection molded.

Compression mold tooling: 6-10 weeks. First article production: 1-2 weeks after tool. Production delivery: 2-4 weeks per order. Compression molding cycle times are slower than injection — 2-15 minute cure times mean lower per-day output. Plan longer lead times for compression programs vs injection programs.