BMC injection molding process

BMC injection molding process

1) Barrel temperature and mold temperature. During processing, BMC is required to maintain low-viscosity flow dynamics for a long time at the barrel temperature. Generally, the barrel temperature should meet the low limit of BMC. The barrel temperature is generally divided into two or three sections, the lower end of the hopper is lower, and the temperature near the nozzle end is higher. Generally, the difference is 20~60°C, mold

The temperature is generally controlled at 135~185 °C.

2) Injection pressure. Due to the poor fluidity of BMC, fast curing and complex mold structure, the injection pressure should be higher, generally 80~160MPa.

3) Injection speed. The increase of injection speed helps to improve the surface quality of the plastic parts and shorten the curing time, but it is not conducive to exhaust gas and increase the orientation of the glass fiber. Therefore, a lower injection speed should be used on the premise of ensuring the surface quality of the plastic parts, usually 1.8 to 3.5 m/min.

4) Screw speed and back pressure. If a screw type injection molding machine is used, the screw has a large damage to the glass fiber when injecting BMC. In order to minimize the damage of the glass fiber, the screw rotation speed should be selected as a low value, generally 20 to 50 r/min. According to the viscosity of BMC, it is preferred to use a low back pressure, generally 1.4 to 2.0 MPa.

5) Molding cycle. Due to the size and complexity of the plastic parts, the process time of each section is also different. The general injection time is 2~20s, and the holding time is 10~20 (thickness).