Root Causes and Solutions
| Cause | Diagnosis | Solution |
|---|---|---|
| Return pins too short | Measure pin length vs stroke + mold close distance | Grind pins to correct length (all pins equal ±0.02 mm) |
| Spring fatigue (early return) | Check spring free length vs original spec | Replace springs at 80% of rated cycle life |
| Bore contamination | Inspect return pin bores for chips/debris | Clean bores; add ejector space covers |
| Insufficient lubrication | Check ejector leader pin lubrication condition | Re-grease; upgrade to oil-groove bushings |
Prevention: Add Plate Return Detection
The most reliable prevention is adding a plate return detection switch or proximity sensor. This provides cycle-by-cycle verification that the plate has fully returned, triggering a machine interlock if it hasn't.