Flash / Burr

Thin sheet-like plastic overflows at the parting line and insert gaps. Flash is distributed along the parting line, the sliding block joint surface, or the edge of the ejector pin hole, appearing as thin sheets or irregular burrs, with the same material as the part but extremely thin thickness. Flash on the assembly surface of the part will seriously affect the fitting accuracy, causing assembly interference or sealing failure; fallen flash fragments may jam moving mechanisms or contaminate the product. Repeated occurrence of flash also wears the mold parting line, causing the mold accuracy to continuously decline, forming a vicious cycle.

1. Process parameter factors: insufficient clamping force, excessive injection pressure, mold parting line wear, platen deformation. 2. Temperature factors: the settings of barrel temperature and mold temperature directly affect melt fluidity, cooling rate, and crystallization behavior; low temperature is a common cause of filling and molding quality problems, and precise control is required according to the material's recommended processing window.

1. Process parameter optimization and adjustment: increase clamping force, reduce holding pressure, regrind the parting line, check platen parallelism. 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.

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.