Blow Molding Troubleshooting: Parison Control, Wall Thickness, Die Swell
Optimizing parison programming and die design.
Process Optimization
Parison programming: axial wall thickness control by moving die gap. Die swell: 15-40% depending on material and shear rate. Wall thickness: programmed 0.5-2.0mm variation along bottle height. Parison sag: gravity causes thinning. Countered by fast mold close and programmed die gap. Die land length: 8-15x die gap for stable parison.
| Issue | Cause | Solution |
|---|---|---|
| Thin neck | Die gap too small | Open gap at parison start |
| Thick bottom | Excessive material | Adjust parison programming curve |
| Weld line | Poor pinch-off | Check pinch edge clearance (0.02-0.08mm) |
| Weight variation | Melt temp change | Stabilize extruder temp +-2C |