BMC & SMCMolds · Compression & Injection Molded Parts
SMC tooling
SMC compression molds for enclosures, panels and covers
In SMC compression molding, plies cut from the sheet are stacked into a charge, laid on the hot lower half of the mold and pressed. The charge spreads out to fill the cavity and cures under pressure. The mold has to steer that flow, trap the compound at the shear edge and keep the whole molding surface at an even temperature.
Typical parts for these molds are electrical enclosures and meter boxes, switchgear panels and covers, sectional water tank panels, EV battery covers and other large structural parts.
Design features we specify
- Telescoping shear edge, typically about 0.05–0.10 mm clearance per side
- Hardened shear-edge inserts that can be reground or replaced
- Polished, hard-chrome plated cavity and core
- Electric heaters or oil/steam channels, thermocouples in both halves
- Stops that set the final part thickness
- Ejector pins or air ejection for a hot, rigid part
- Molded-in inserts and side cores where the part needs them
- Vacuum-assisted molding for deep ribs and parts that trap air
SMC compression mold at a glance
| Process | Compression molding of SMC (sheet molding compound) |
|---|---|
| Mold temperature | Typically about 140–160 °C, held evenly over the cavity and core |
| Heating | Electric cartridge heaters, or oil or steam channels; thermocouples in both halves |
| Shear edge | Telescoping, typically about 0.05–0.10 mm clearance per side; hardened or insert type |
| Steel | P20-type pre-hardened for lower volumes; hardened grades for long runs |
| Surface | Polished and hard-chrome plated; textures possible with extra draft |
| Ejection | Ejector pins, stripper or air ejection |
| Options | Molded-in inserts, side cores, vacuum-assisted molding |
SMC compression mold FAQ
How large can an SMC part be?
SMC is used for parts from small brackets to panels well over a meter long. The practical limit is the platen size and tonnage of the press, so the mold is designed around the press it will run in.
How do you control flash on SMC parts?
With a telescoping shear edge that has a tight, even clearance, stops that set the final thickness, and a charge sized to fill the part without much excess. The thin flash that remains is removed in deflashing.
Can SMC parts have holes and inserts?
Yes. Through-holes can be molded with pins or machined after molding, and threaded or press-fit metal inserts can be molded in or added later, depending on tolerance and load.