A compression mold manufacturer builds the heated press tools that turn thermoset compounds — SMC sheet, BMC dough, phenolic powder, rubber stock — into finished parts in one closed-die cycle. No sprue or runner is needed: a pre-weighed charge is laid into an open cavity, and the press closes to flow and cure the material under heat and pressure. This guide covers what these tools look like and what to confirm before ordering.
What a compression mold manufacturer actually builds
- SMC BMC compression mold tooling for automotive panels, electrical housings and insulators
- Phenolic and melamine molds for heat-resistant handles, knobs and switchgear components
- Rubber and elastomer molds for gaskets, seals, boots and mats
- Insert-molding variants that place metal terminals into the cavity before pressing
- Transfer-mold hybrids where a separate pot feeds thin or deep cavities
Most tools use P20 or 718H pre-hardened steel at 30-35 HRC, with H13 reserved for high-fiber phenolic grades and abrasive fillers. Heating comes from cartridge heaters plus oil circuits holding ±3 °C across the parting surface; cooling channels still matter, because thick sections must manage exotherm without warpage.
Specifications to compare when sourcing press tooling
- Tool steel and hardness: P20 or 718H at 30-35 HRC standard; H13 for high-fiber phenolic grades
- Mold temperature: 135-170 °C with ±3 °C uniformity from cartridge and oil heating
- Clamping pressure: 10-30 MPa on projected area; 10-15 MPa typical SMC, 25-30 MPa for deep parts
- Cure time: about 40 s per mm of wall thickness, plus a venting dwell before opening
- Draft 1-2°, vent slots 0.05 mm x 5 mm, shut-height matched to 1000-1500 t presses
Process windows behind the tool
Thermoset compression molding runs at 135-170 °C — lower for thick parts to avoid exotherm cracking, higher for thin walls that must flow before gelation. SMC charges are weighed to ±1%, the 40 s per mm cure rule is adjusted for color, filler level and reactivity, and overflow grooves catch excess compound while RTD or dielectric sensors confirm cure before ejection.
Questions to ask a compression mold manufacturer
- Which steel and hardness will the tool use, and what shot life is guaranteed?
- How is heating controlled, and what uniformity is guaranteed at the parting line?
- What is the cure schedule per mm, and can you run T0 samples on our press?
- Are overflow grooves, vent slots and ejector access designed for our compound viscosity?
- What lead time applies, and are spare inserts or heater circuits available?
Compression tooling sits alongside the other families in our plastic molds category. If you are weighing closed-die pressing against melt-based processes, read our blow molding vs injection molding comparison; mold maintenance scheduling covers the upkeep side. Verified suppliers are listed in the company directory.
Related product categories
The materials and part types discussed above are grouped in our sourcing directory:
