Plastic bottle-blowing machines operate under high temperature, high pressure, and continuous mechanical motion. During long-term production, various faults may occur, affecting bottle quality, production efficiency, and operational stability. Understanding common problems and their solutions helps manufacturers reduce downtime, improve yield rates, and maintain consistent bottle performance. This article summarizes the most frequent faults in plastic bottle-blowing machines and provides practical, production-oriented solutions.

Uneven Bottle Wall Thickness

Uneven wall thickness is one of the most common issues in bottle blowing. It often appears as thin areas at the bottle shoulder, bottom, or sidewall.

This problem is usually caused by uneven preform heating, incorrect stretching behavior, or improper blowing pressure distribution. If the preform temperature is inconsistent, the material will stretch unevenly during forming.

To solve this issue, operators should optimize the heating profile, ensuring uniform temperature distribution across the preform. Stretch rod alignment and stroke length should be checked, and pre-blow and high-pressure blow timing should be adjusted to allow even material flow into the Mold.

Bottle Bottom Deformation or Uneven Base

An unstable or uneven bottle bottom can cause bottles to wobble on conveyor lines or collapse under load.

This fault is often related to insufficient bottom heating, incorrect stretch rod positioning, or unbalanced mold cooling. In some cases, early demolding before full cooling can also deform the base.

Solutions include adjusting bottom heating zones, verifying stretch rod centering, balancing mold cooling water flow, and extending cooling time before mold opening.

Poor Bottle Transparency or Haze

Reduced clarity or haze in bottles is a quality concern, especially for PET packaging.

This issue is commonly caused by excessive heating, incorrect stretch ratios, or contaminated raw materials. Overheating can damage molecular orientation, while insufficient stretching reduces optical clarity.

To improve transparency, heating temperatures should be reduced slightly, stretching parameters optimized, and raw material quality checked. Using consistent, high-quality preforms also helps maintain visual clarity.

Bottle Shrinkage After Demolding

Bottle shrinkage occurs when the bottle changes shape after removal from the mold, often at the shoulder or bottom area.

This problem usually results from insufficient cooling time or excessive internal stress during forming. Rapid demolding while the material is still soft can cause deformation.

Increasing cooling time, optimizing mold temperature, and reducing excessive stretching force can significantly reduce shrinkage.

Air Leakage or Insufficient Blowing Pressure

If the bottle is not fully formed or lacks definition, air leakage or low blowing pressure may be the cause.

Common reasons include worn seals, leaking air valves, blocked air lines, or unstable air supply pressure.

Regular inspection of pneumatic components, replacement of worn seals, cleaning air pipelines, and maintaining stable compressor pressure help ensure reliable blowing performance.

Inconsistent Bottle Height or Shape

Variations in bottle height or shape often indicate mechanical or control-related issues.

Possible causes include unstable stretch rod movement, inconsistent preform length, or timing deviations in the control system.

Solutions include checking stretch rod guides for wear, calibrating motion systems, verifying preform consistency, and reviewing machine timing parameters through the control interface.

Mold-Related Defects

Scratches, dents, or incomplete details on the bottle surface are often caused by mold issues.

Dirty mold surfaces, damaged mold cavities, or poor venting can prevent proper material flow and surface replication.

Routine mold cleaning, polishing, vent inspection, and timely mold maintenance are essential to prevent surface defects.

Heating System Failures

Heating system faults can lead to unstable production and quality fluctuations.

Common problems include failed heating lamps, uneven lamp output, or temperature sensor malfunction.

Replacing damaged lamps, recalibrating temperature sensors, and maintaining clean reflectors help ensure stable and efficient heating performance.

Summary Table of Common Faults and Solutions

Preventive Maintenance Recommendations

Many bottle-blowing machine faults can be prevented through regular maintenance. Daily inspection of heating systems, pneumatic lines, molds, and mechanical components helps identify early signs of wear. Stable production parameters and standardized setup procedures further reduce defect rates.

Using a well-designed bottle-blowing machine with precise temperature control, stable air systems, and reliable mechanical structure also plays a key role in minimizing faults and improving long-term production consistency.

Conclusion

Plastic bottle-blowing machines may encounter various faults during operation, but most issues can be resolved through systematic analysis and proper parameter adjustment. By understanding common problems such as uneven wall thickness, bottom deformation, air leakage, and heating instability, manufacturers can take corrective action quickly and maintain high production efficiency. A combination of correct process control, routine maintenance, and reliable equipment ensures consistent bottle quality and stable long-term operation.