Product whitening

Chalky white areas appear on the product surface. When this defect appears in products of Process No. 3, it is usually related to a specific process parameter range or equipment state. If it continues to appear, it will directly affect the product qualification rate and production rhythm, increasing material loss and rework costs. Timely diagnosis and elimination is a basic requirement for ensuring stable production.

1. Mold design factors: incomplete curing, release agent incompatible with the resin, mold temperature too low, material containing moisture. 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. 3. Molding pressure factor: In compression molding, pressure is not only used to overcome flow resistance, but also directly affects the compactness of the product and the degree of fiber impregnation; insufficient pressure is an important cause of product looseness and insufficient strength.

1. Process parameter optimization and adjustment: ensure complete curing, replace with a compatible release agent, raise the mold temperature, fully dry the material. 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 product whitening 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.