Injection molding ejection problems include parts that stick, drag marks, ejector-pin witnesses, distortion or inconsistent release. These symptoms can come from part geometry, mold surface, ejection layout, material behavior or the conditions at ejection. Record the defect and the affected cavity before changing the tool or process.
Describe the release problem precisely
Record whether the part remains on the core or cavity, where the marks appear, which cavities are affected, and whether the issue occurs at startup or during a stable run. Photograph the part and mold area. Identify the drawing revision, resin and color, surface texture, machine and tool, and any recent maintenance or process change. A stuck part, a scuffed surface and a bent part are different symptoms and should not be treated as one failure mode.
Review geometry, pull direction and surface
Ask the design and tooling team to review draft and undercuts against the actual pull direction, part depth, material and specified finish. Draft requirements are not one fixed angle for every surface: texture, polish, material and geometry affect the release condition. Check whether the problem appeared after a texture or polish change, or whether the drawing leaves the finish undefined.
Check the ejection system against the part
Review the ejector locations and contact surfaces against the shape and stiffness of the part. Look for concentrated marks, uneven movement, damaged or obstructed components, and whether the ejection method suits the part geometry. Deep draws, thin walls and side actions may need a different release review than a shallow part. Confirm any change in the mold assembly drawing and revision record.
Separate tool, vacuum and process evidence
Inspect the parting and venting strategy, undercut or side-action release, mold surface condition, cooling consistency and machine ejection records. Compare the ejection condition with the approved sample and the resin-specific process window. Part temperature and strength at release can affect deformation and ejector marks; do not apply a universal cooling time or ejection-speed recipe.
Validate the corrective action
Record the original condition, the proposed change, the cavities tested and the release result. Recheck appearance, dimensions and downstream fit or assembly. Repeatedly applying release agent can hide a draft, finish or venting problem and can be unsuitable for parts that are painted, bonded or otherwise finished. Agree on an approved sample and release criteria before returning the tool to production.
Autodesk explains how tapered walls can reduce friction during ejection and notes that draft depends on surface finish and part geometry in its tapering-walls guidance. For related project records, see DAYIN’s mold-debugging preparation guide, mold-processing checklist and dimensional-stability guide.