Debugging Skills for Unbalanced Ejection in Plastic Molds

Unbalanced ejection is a common structural issue in injection molds, causing deformation, whitish marks, cracks, sticking, or pin breakage. This guide provides practical on-site debugging methods.

Quick Identification of Unbalanced Ejection

Local whitish marks, cracks, or depressions on the product.

Uneven wear on ejector pins, with some pins overloaded.

Obvious tilting, warping, or one-sided sticking during ejection.

Abnormal noise or tilting of the ejector plates.

Main Causes

Unbalanced layout of ejector pins: Insufficient pins or uneven distribution in high-clamping-force areas.Unequal lengths of ejector components: Ejector pins/blocks with inconsistent heights cause asynchronous ejection.Insufficient rigidity or poor guidance of ejector plates: Deformed plates or worn guide pillars lead to tilting.Uneven package force: Asymmetric product structure causes uneven clamping force on the mold.Excessive holding pressure or uneven cooling: Increases mold sticking and amplifies force imbalance.

On-Site Debugging Skills

Level the ejector plate: Ensure all ejector components contact the product simultaneously; grind or adjust pin heights.Strengthen ejection in high-force areas: Add ejector pins/blocks near deep cavities, ribs, or undercuts to distribute force.Improve guidance: Replace worn guide pillars/bushings and ensure proper lubrication for smooth movement.

Optimize injection parameters: Reduce holding pressure, balance mold temperature, and adjust ejection speed.Enhance venting and draft angles: Widen vents to reduce vacuum sticking; increase draft angles on deep cavities.Use structured ejection systems: Adopt plate ejection or multi-stage ejection for large/complex parts.

Long-Term Prevention

Distribute ejectors evenly during design, prioritizing ribs, pillars, and deep cavities.

Control machining tolerances to ensure uniform ejector height.

Perform regular maintenance on ejection components to prevent wear/deformation.

Solve structural issues during trial molding instead of relying on parameter adjustments.