Fiber exposure

Glass fiber is exposed on the product surface. When glass fiber is exposed, the product surface appears white or grayish-white hazy, feels rough to the touch, and is most conspicuous on dark-colored products. This is because the surface resin failed to fully wrap the glass fiber, and the fibers are directly exposed. Abnormal glass fiber orientation macroscopically manifests as different shrinkage rates in various directions, causing the product to have unpredictable warpage deformation. Fiber-related defects are especially critical in structural parts, because fiber distribution and orientation directly affect the strength and stiffness of the product.

1. Process parameter factors: improper resin-to-fiber ratio, resin loss during pressing, high mold temperature causing resin to flow too fast, insufficient pressure and fibers not wrapped by resin. 2. Preheating factor: The preheating temperature and time of the material (especially thermosetting molding compounds) directly affect its flowability and curing behavior; improper preheating will lead to poor filling or uneven curing, and it is a key control point unique to compression molding.

1. Process parameter optimization and adjustment: adjust the resin-to-fiber ratio, control the mold temperature to prevent resin loss, increase the molding pressure. 2. Systematic troubleshooting method: Troubleshooting of compression molding problems follows the order of 'material -> temperature -> pressure -> mold'. First check the preheating and flowability of the material, then verify the mold temperature distribution and curing time, then adjust the molding pressure and mold closing speed, and finally check the mold venting and demolding conditions. 3. Preventive management: Establish standardized process parameter cards and quality control limits for each set of mold/product, and regularly conduct process capability index (CPK) evaluations. For recurring problems, use fishbone diagrams or 5Why analysis to trace the root cause, and solidify the countermeasures as PFMEA control points.

This problem is a typical manifestation of fiber exposure in compression molding; the core of the solution lies in proper preheating of the material and assurance of flowability, as well as precise matching of mold temperature and molding pressure. It is recommended to adjust coordinately from both aspects of material state and process parameters.