First, the bubble

Is due to gas pressure BMC substrate resulting in the surface of the product protruding.

Possible Causes and Corrective Actions Possible Causes and Corrective Actions Possible Causes and Corrective Actions:

1. The "dry glass" in the BMC feedstock causes voids in the molding compound plies which may expand into gas bubbles when they are collected during the forming process. To completely correct the process is to change the process or reduce the glass fiber content in the preparation of BMC.

2. BMC raw materials are moisture, press oil, oil or mold release agent contaminated during the heating may be converted into steam and bubbles, calcium carbonate and stearate are hydrophilic so easy Contaminated with water.

3. The opportunity to capture air should be minimized, depending on the area and location of the BMC bedding, in fact using a reduced area for paving, similar to the pyramid laying in the center of the mold is effective, can force the air in the molding Run in front of the BMC stream and escape.

4. When clamping to the last dimension, the mold closing speed should be minimized. Lower mold closing speed will reduce material agitation and impair the chance of capturing air.

5. The lower mold closing speed described above, combined with the lower mold temperature, results in a smoother flow and less pre-gelation and reduces the chance of capturing air, but the curing time must be extended.

6. Reducing molding pressure is effective, creating a flatter stream, reducing the chance of capturing air.

7. Check the parallelism of the mold installation and the parallelism of the press itself. Chattering (uneven flow) of the flow due to loss of mold installation increases the chance of capturing air.

8. Excessive initiator or inhibitor can cause pre-gelation and uneven flow. Similarly, low-shrink additives can cause gas generation. At the moment, it is necessary to improve the formulation of BMC.

9. Material viscosity greatly affects the flow, it is necessary to adjust to the appropriate range, usually pay attention to the different viscosity levels will affect the bubble to the extent and location of the frequency.

10. Product variable cross-section thickness of the site can change the flat flow, too thick cross-section in the curing can not get enough heat and pressure, this can be from the product design review.

11. The air trapped in the mold usually causes the product to lack of flesh, spontaneous combustion and bubbles, so proper discharge fins are necessary to facilitate venting.

12. Excessively dry pellets cause instability of the flow, resulting in gel, pinholes and bubbles.