Mold sticking is a common issue in mass production that can easily lead to stress marks (whitening), breakage, surface tearing, and downtime for cleaning, thereby impacting production efficiency. This problem generally falls into two categories-sticking to the fixed (front) mold or the moving (rear) mold-and can be effectively resolved through process adjustments, equipment inspections, and mold modifications.
Temperature Optimization
Appropriately lower the barrel temperature to reduce adhesion caused by melt over-aging; lower the mold temperature and shorten the mold holding time; pay attention to the temperature difference between the front and rear mold halves, adjust the product's shrinkage direction, and ensure the part remains on the ejection side.
Injection Parameter Adjustments
Reduce injection pressure, holding pressure, and holding time to prevent product over-compaction and excessive clamping force; lower the injection speed to avoid high-pressure material infiltration into micro-cavities, which can cause the part to stick to the mold.
Cycle and Ejection Settings
Appropriately extend the cooling time to ensure the part fully hardens; configure the ejection speed in stages-starting slowly to prevent damage caused by sudden pulling forces-and optimize the ejection dwell time.
Raw Materials and Additives
Ensure raw materials are thoroughly dried; apply mold release agents in compliance with specifications and control the spraying frequency, as excessive application can lead to surface defects.
Check whether the pressure and flow rate of the ejection cylinder are sufficient, and verify that there are no abnormalities with the ejection limit settings.
Check the mold opening and closing balance of the injection molding machine to prevent slight mold misalignment caused by unbalanced clamping force;
Verify that the pressure settings for the robotic arm's suction cups and grippers are appropriate to prevent uneven stress or pulling on the product during mold extraction.
Polishing optimization: Avoid excessive mirror-finish polishing on the cavity; instead, strategically incorporate fine textures to reduce vacuum adhesion.
Upgraded venting eliminates mold sticking caused by vacuum negative pressure in enclosed cavities.
Add ejector pins, flat ejector pins, and ejector blocks to balance ejection force; install a vacuum intake valve to break the vacuum suction.
Check for undercuts and rounded corners, and correct draft angles; regularly clean the mold to remove carbon deposits and oil residue.
Widespread mold sticking: usually caused by excessive holding pressure or high mold temperature;
Localized mold sticking or scuffing: insufficient draft angle, poor polishing, or inadequate venting;
Cyclic/intermittent mold sticking: vacuum suction, uneven cooling.
Establish a standardized debugging sequence-prioritizing the adjustment of holding pressure and cooling, followed by optimizing ejection parameters and mold inspection-to minimize the waste of raw materials and labor hours caused by repeated mold trials.
