Overflow flash

Excess material overflows at the parting line and forms flash. Flash is distributed along the parting line, slide joint surfaces or ejector pin hole edges, in the form of thin sheets or irregular burrs, with the same material as the product but extremely thin thickness. Flash on the assembly surface of the product will seriously affect the fitting accuracy, causing assembly interference or sealing failure; detached flash fragments may get stuck in moving mechanisms or contaminate the product. Repeated flash generation will also wear the mold parting line, causing the mold accuracy to continuously decline, forming a vicious cycle.

1. Process parameter factors: excessive feeding amount, excessive molding pressure, large mold gap, insufficient clamping force. 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: reduce the feeding amount, lower the molding pressure, repair the mold parting line, increase the clamping force. 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.

The root cause of flash is that the mold-opening force generated by the cavity internal pressure exceeds the closing force of the clamping system. The logic chain of the solution is: first reduce the cavity pressure peak through process adjustment, then check and repair the clamping system to ensure sufficient closing force, and at the same time repair the parting line to ensure sealing conditions.