If someone uses “mold swelling” to describe visible mold movement, a parting-line gap, or flash on a molded part, first identify the actual observation. The term alone does not establish a root cause. This guide uses mold deflection or mold opening for movement that allows material to escape at a parting line, and treats flash as a symptom that must be investigated against the tool, machine, material, and process.
Flash can have more than one cause
Autodesk Moldflow troubleshooting lists possible contributors including worn or poorly fitted mold plates, insufficient clamp force, overpacking, molding conditions, and venting. Autodesk also notes that excessive cavity pressure late in filling can contribute to mold opening and flash. The visible defect alone does not prove that the mold plates have permanently deformed or that trapped gas is the cause.
Do not assume that adding gates, increasing clamp force, changing vent dimensions, or creating a pre-compressed gas space will solve the problem. Any correction depends on evidence from the actual mold and molding process, and a change intended to address one defect can create another.
Collect evidence before selecting a correction
- Map the defect. Photograph and mark where flash occurs, which cavity is affected, when it first appeared, and whether it follows a recent tool, material, or process change.
- Check the parting interface. Review the affected shut-off or parting line for wear, fit, contamination, damage, and evidence of uneven contact.
- Review the machine and process record. Confirm the machine and mold configuration, resin grade and lot, shot and packing conditions, and the approved velocity-to-pressure switchover record. Compare actual results with the qualified process window rather than applying a generic setting.
- Separate venting symptoms. Short shots, burn marks, or air traps may involve venting, but should be diagnosed separately from evidence of parting-line opening.
- Verify the correction. Record the approved tool or process change and inspect samples for flash, dimensions, appearance, and any new defect under the agreed acceptance plan.
Autodesk’s flash troubleshooting guide discusses multiple tool, clamp-force, packing, process, and venting factors. Its velocity/pressure switchover guidance explains that switching too late can contribute to mold opening and flash. These references support investigation; they do not set a universal machine recipe or repair procedure.
For related production and inspection topics, see DAYIN’s mold-processing guide và hướng dẫn kiểm tra chi tiết injection molding của DAYIN. To discuss a project-specific tooling or molding issue, provide the part drawing, resin grade, defect location, and available sample records through the trang liên hệ.