Large product post-shrinkage

The product dimensions continue to change after storage. Shrinkage problems manifest as the product's dimensions continuously shrinking after demolding, with a fast initial shrinkage rate (70%-80% of the total shrinkage completed in the first 24 hours), then slowly tending to stabilize. When shrinkage is uneven, the product shows dimensional differences or deformation; when the shrinkage amount is too large, the product exceeds the lower tolerance. The shrinkage of compression and transfer molded products is significantly affected by curing conditions and post-curing processes, which is different from the thermoplastic shrinkage mechanism of '2079851475616104452.

1. Comprehensive factors: incomplete post-curing, crystalline resin continuing to crystallize, ambient temperature change, large product wall thickness. 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: fully post-cure, control the storage environment temperature, optimize the product wall thickness, anneal if necessary. 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 large product post-shrinkage 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.