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During bottle production, blow molding machines may encounter issues such as poor transparency, uneven wall thickness, excessively thin bottle bases, visible parting lines, curling at the base or neck, and material accumulation. These problems stem from factors like improper heating control, moisture in compressed air, poor preform quality, flawed preform design, or incorrect blow/stretch ratio settings. Below are targeted solutions:
Issue 1: Perforation at the Bottle Base During Stretching
Causes:
- Insufficient heating, leading to incomplete material penetration.
- Excessive delayed stretching time or overly high stretching ratio.
- Preform base design is too thin, combined with an overly sharp stretching rod tip.
Solutions:
- Increase heating temperature.
- Reduce delayed stretching time and lower the stretching ratio.
- Optimize preform base design for adequate thickness.
- Round off the stretching rod tip to reduce sharpness.
Issue 2: Bottle Bursting
Causes:
- Inadequate preform heating (insufficient material softening).
- Stretching rod fails to reach its full position.
- Stretching rod movement speed is too slow.
- Temperature protection limits are set too high.
Solutions:
- Increase voltage to extend secondary blow time while maintaining output, or reduce output and lower voltage.
- After mold clamping, manually push the stretching rod to ensure full contact with the mold base and tighten the limit nut (applicable to mechanical limit cylinder adjustments).
- Maximize the throttle valve on the stretching cylinder.
- Adjust temperature limits: Set PET preform lower limit to 85–95°C and upper limit to 125–130°C.
Issue 3: Misaligned Bottle Base
Causes:
- Slow stretching rod movement speed.
- Insufficient delayed blowing time.
- Severe preform eccentricity.
Solutions:
- Maximize the throttle valve on the stretching cylinder to accelerate stretching.
- Extend delayed blowing time.
- Measure preform eccentricity; adjust curvature after proper heating if deviation is excessive.
- Ensure temperature protection functions operate correctly.
General Preventive Measures
- Temperature Control: Optimize heating zones and time to ensure uniform preform softening.
- Air Quality: Install dryers to remove moisture from compressed air.
- Preform Design: Improve preform geometry and wall thickness distribution.
- Equipment Calibration: Regularly inspect and adjust stretching rods, blow nozzles, and rotation devices.
By addressing these root causes and implementing corrective actions, manufacturers can enhance product quality, reduce defects, and maintain efficient production workflows. Regular maintenance and operator training are critical to sustaining optimal machine performance.
