Make · process

Compression moulding

A charge pressed and cured between heated mould halves

A measured charge — a sheet or bulk moulding compound of chopped fibre in resin, or a rubber blank — is placed in a heated mould and squeezed to shape until it cures. Fast enough for automotive volumes, and the home of SMC and BMC composites.

Moderate–high
Volume
High — matched steel
Tooling
Minutes
Cycle
Moderate–tight
Tolerance
How it works
  1. 1
    Place a measured charge in the lower heated mould.
  2. 2
    Close the mould and apply high pressure.
  3. 3
    The charge flows to fill the cavity and cures under heat.
  4. 4
    Open, eject and trim the flash.
Strengths & limits
Strengths
  • Faster than layup — automotive volumes
  • Handles chopped-fibre compounds (SMC/BMC)
  • Good for large, moderately complex parts
  • Consolidates ribs and inserts in one shot
Limits
  • Two-sided steel tooling is expensive
  • Chopped fibre gives lower properties than continuous
  • Flash to trim
Typical parts & materials

Typical parts: Automotive panels and structural parts, electrical housings, rubber seals

Commonly run in — open one for its cited properties:

PolyesterVinyl esterEpoxyE-glass

Part of the Make map of manufacturing processes. Browse the cited database, or see where these parts end up in the application domains.