How to avoid black specks in PET preform production

The production of PET preforms is based on a multi-stage moulding process. The following example of a food packaging company illustrates the issues involved. How was the manufacturer able to identify and solve the problems associated with carbonization and colour change – and why was the cooperation with Chem-Trend crucial?

A food packaging company was experiencing a series of challenges in their manufacturing process of PET preforms. Quality problems stemming from carbonization and colour change issues in the injection moulding process were not being detected prior to shipment. Chem-Trend set out to find a solution – and finally managed to solve the problem in close collaboration with the customer.

Defective preforms result in customer complaints and batch rejections

The main issue the food packaging company had to face during the PET production process: Defective preforms needed to be identified and discarded before they made their way into bottles. Chem-Trend analyzed the situation together with the customer and figured out: a major obstacle to quality control was the packaging company’s short cycle times and high volume 24/7 preform production schedule limiting the chance for effective cleaning maintenance.

How Chem-Trend identified the problem

During a technical assessment, the team identified the extruder and shooting pot areas of the machine as the main sources for material degradation and carbonization, which resulted in black specks, and focused on finding out an opportune time for maintenance to take place without hindering production. Subsequently, Chem-Trend’s technical experts determined a window for preventive purging during routine mould and product change that helped the customer to resolve the common, yet challenging issues of PET preform production.

The solution: Ultra Purge™ purging compounds

In order to find a suitable solution to readjust the client’s PET preform manufacturing process, Chem-Trend recommended to use the Ultra Purge™ purging compound technology during colour and tool change processes. The result quickly became apparent: All signs of contamination from carbon and black specks were removed in the subsequently produced preforms, leading to a dramatic improvement in product quality.

Results of using Chem-Trend’s Ultra Purge™ in a nutshell

• 25% decrease in scrap alongside light colour change
• 45% decrease in scrap alongside difficult colour change
• 100% fewer rejected end products due to removal of black specks contamination

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