Overflow flash

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: transfer pressure too large, large mold gap, insufficient clamping force, excessive feeding amount. 2. Runner and gate design factor: In transfer molding, the material needs to enter the cavity through runners and gates; the runner length, cross-sectional shape and gate size directly affect pressure loss, fiber breakage and filling balance, and unreasonable design is the root of many quality problems.

1. Process parameter optimization and adjustment: lower the transfer pressure, repair the mold parting line, increase the clamping force, reduce the feeding amount. 2. Systematic troubleshooting method: Troubleshooting of transfer molding problems follows the order of 'runner -> feeding -> parameters -> mold'. First check whether the runners and gates are blocked or worn, then verify the feeding amount and material preheating, then adjust the transfer pressure and speed, and finally check the mold venting and temperature uniformity. 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.