What flash is on an injection-molded part, why the press makes it, and what to check before the next shot. Louisville, Ohio.
Flash is plastic that escaped the cavity and froze on the parting line. The part looks finished until you feel a thin fin.
What you are looking at
Flash is not a mystery defect. The melt found a gap that should have been closed. Common gaps are a worn parting line, a clamp force that is too low for the projected area, a vent that was opened until it became a leak, or a shutoff that no longer meets. If the fin is only in one corner, start there instead of raising the clamp on the whole tool.
Look at the last good part and the first bad one from the same mold. If flash showed up after a mold change, check the setup: platens clean, clamps seated, and the process sheet the current revision. Dirty platens and a mold that is not pulled up evenly will flash one side. Process changes that push flash are higher pack pressure, a longer pack time, or a melt hotter than the sheet. Those changes are sometimes made to hide a short shot. Fixing flash by dropping pressure can bring the short shot back.
A whiteboard does not tell the next shift which process sheet was running when the flash started. Mold setup tracking keeps the mold, the press, and the sheet revision on one queue. Estimate the hours with the mold setup time calculator, then read the injection molding software page if the plant needs that queue in production.
Live products: SetupLens, EduMatrix Pro, ImanQuest.
Mold setup time calculator · What is mold setup tracking software? · Start Project Discovery
