SMC materials frequently encountered problems in the molding process and their treatment methods(2)

Three, warpage deformation
The main reason is the uneven curing of the molding compound and the shrinkage of the product after demolding.

Generation mechanism and countermeasures:
During the curing reaction of the resin, the chemical structure changes, causing volume shrinkage, and the uniformity of the curing makes the product tend to warp to the side that is cured first. Secondly, the thermal expansion coefficient of the product is larger than that of the steel mold. When the product is cooled, its unidirectional shrinkage is greater than the unidirectional heat shrinkage of the mold. To this end, the following methods are adopted to solve the problem:
①Reduce the temperature difference between the upper and lower molds and make the temperature distribution as even as possible.
③ Use cooling jigs to limit deformation.
④ Properly increase the molding pressure, increase the structural compactness of the product, and reduce the shrinkage rate of the product.
⑤ Properly extend the holding time to eliminate internal stress.
⑥ Adjust the curing shrinkage rate of SMC material.

Four, blistering
The semicircular bulge on the surface of the cured product.

Generation mechanism and countermeasures:
It may be that the material is incompletely cured, the local temperature is too high or the volatile content in the material is large, and the air traps between the sheets, which makes the semicircular bulge on the surface of the product.
① Increase the molding pressure appropriately.
②Extend the holding time.
③Reduce the mold temperature.
④Reduce the unwinding area.

Five, the surface color of the product is uneven

Generation mechanism and countermeasures:
① If the mold temperature is not uniform, and the part is too high, the mold temperature should be properly controlled.
②Poor fluidity of the molding material, resulting in uneven fiber distribution, generally can increase the molding pressure to increase the fluidity of the melt.
③Pigment and resin can't be mixed well in the process of color paste blending.