Post Shrinkage

The dimensions of the part continue to shrink during storage. Shrinkage problems manifest as continuous dimensional reduction of the part after demolding; the initial shrinkage rate is fast (70%-80% of the total shrinkage is completed in the first 24 hours), and then it slowly tends to stabilize. When shrinkage is uneven, the part shows dimensional differences or deformation; when the shrinkage is too large, the part exceeds the lower tolerance. The shrinkage of compression-molded and transfer-molded parts is significantly affected by curing conditions and post-curing processes, which is different from the thermoplastic shrinkage mechanism of '2079851475616104452.

1. Material factors: incomplete crystallization of crystalline materials, insufficient cooling time, environmental temperature influence. 2. Mold comprehensive factors: in addition to venting, mold design parameters such as cooling water channel layout, gate position and size, and demolding draft angle all have a systematic impact on part quality, and optimization is required from the source of mold design.

1. Process parameter optimization and adjustment: extend cooling time, increase mold temperature to promote crystallization, store parts in a constant temperature environment, and perform annealing treatment if necessary. 2. Systematic troubleshooting method: troubleshoot item by item in the order of "parameters -> material -> mold -> equipment". First adjust the parameters that are easiest to change, such as injection pressure and temperature, and observe the effect; if there is no improvement, check the drying and fluidity of the raw material; further check mold venting and gate design; finally check the mechanical condition of the equipment (check ring, screw). Change only one variable at a time to determine the root cause. 3. Preventive management: establish standardized process parameter cards and quality control limits for each mold/product, and regularly conduct process capability index (CPK) evaluation. For recurring problems, use fishbone diagram or 5Why analysis to trace the root cause, and fix the countermeasures as PFMEA control points.

This problem is a typical manifestation of post shrinkage in '2079851475616104452; the core of the solution lies in eliminating the root cause of the defect through systematic optimization of process parameters (temperature, pressure, speed) and rationality checks of mold design. It is recommended to start with process parameter adjustment and gradually go deeper into the equipment and mold levels.