Base / petaloid deformation
Cause
Insufficient base cooling or material distribution causes rocking or stress cracking at base.
Corrective action
Improve base mold cooling, optimize material in base, verify petaloid design and clamp force.
Diagnosis guide: Base diamond / petaloid distortion
What you will see
Petaloid base does not form symmetric diamonds — some petals are deeper, some shallower, or twisted. Bottle stability and pressure rating compromised.
Likely causes
- Preform centered incorrectly in mold (off-axis stretching)
- Stretch rod alignment off
- Base mold halves not parallel
- Pre-blow asymmetric across cavity
Do this first
Inspect preform centering and stretch rod alignment.
How to diagnose it
- Photograph base from underneath on 10 bottles per cavity
- Measure diamond depth at each petal
- Verify stretch rod runout < 0.1 mm
- Check mold parallel alignment with dial indicator
How to fix it
- Re-align stretch rod centerline with mold centerline
- Balance pre-blow flow per cavity
- Adjust mold base alignment