Shenzhen Alu Rapid Prototype Precision Co., Ltd.

Flash, also known as burr or overflow, is a common defect in injection molding where excess molten plastic escapes from the mold cavity and solidifies along the parting line, ejector pins, or other gaps, forming thin, unwanted fins or layers on the part. This can affect aesthetics, functionality, and require post-processing like trimming.

Primary Causes of Flash

Flash typically results from a combination of mold, machine, and process factors that allow plastic to leak under pressure. Below is a summary of the most common causes, grouped by category:

These causes are interconnected—for instance, mold wear can amplify the effects of high pressure. Addressing flash often involves iterative troubleshooting, starting with checking the mold and clamping setup.