Cocked/Tilted Necks 

“Cocked neck" or "tilted neck" defects happen when there is an uneven distribution of material in the neck or shoulder area of the container. As a result, one side cools and contracts unevenly from the other. 

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cocked neck close up

Plastic Material Types at Risk of Cocked or Tilted Necks

Cocked or tilted necks primarily occur in High Density Polyethylene (HDPE) and Polyethylene Terephthalate (PET) plastic during Extrusion Blow Molding (EBM), One-Step Blow Molding (ISBM), and Stretch Blow Molding (RSBM) processes. 

Common Causes of a Cocked or Tilted Neck

In addition to uneven material distribution, the following can cause a cocked or tilted neck:

  • Inadequate container design
  • Incorrect loading of the preform into the blow mold
  • Handling of the bottle before proper cooling   

General Troubleshooting

Check your blow molding alignment and cooling temperatures to ensure containers are properly cooled and set before handling. Some tilted neck defects can be detected on ALPS leak testers by using non-tilting probes with harder seal durometers. 

ALPS Inspection is proud to be a market leader in manufacturing in-line leak inspection equipment for empty plastic containers of all sizes, shapes, and materials. Our team of experts provides thorough defect analysis and feasibility testing services, giving you the valuable insight needed to improve defect detection and ensure optimal leak detector performance.