Manhole Cover Process

1. SMC molding process
Preparation before pressing (mold temperature rise, press process parameter setting) —
SMC sheet material cutting — mold feeding — holding pressure —- demoulding —-
processing (removing waste edges, etc.) —- finished product.
1. Preparation before pressing (mold temperature rise, press process parameter setting): Usually, the mold temperature is generally between 140° and 160°, (the detection temperature of the mold is about 135° for the lower mold and about 145° for the upper mold). The cavity temperature must be uniform.
Deviation should be controlled within 30C. The molding pressure is 15-25 MPa.
2. Before pressing, to check the temperature and whether the material sticks to the mold, you can put a little less material to test the pressure; when the temperature is low or the mold finish is poor, it will stick to the mold. Generally use zinc stearate, beeswax, or paraffin as a release agent. But it should not be used for
many purposes, otherwise, the surface of the product will be polluted. When the film is not sticky, a release agent is not needed.
3. SMC sheet cutting material:
Cut SMC sheet to prepare for mold feeding. When SMC is cutting, first cut longitudinally, then transverse Cutting, as shown:
4. Mold feeding:
After rigorous weight calculation, put the SMC sheet into the mold, usually, the feeding area is between 60% and 80%. SMC should be placed in spokes (as shown in the figure) to facilitate exhaust. Otherwise, the product is easy to form an interlayer.

SMC molded manhole cover production process parameters.