CUSTOM MIXING SCREW FOR HIGH-END COSMETIC PACKAGING

Improved colour dispersion. Better process stability. One geometry, multiple successful applications.

Several manufacturers of premium cosmetic packaging using injection stretch blow moulding machines from a leading Japanese machine manufacturer faced the same challenge: achieving perfect colour dispersion when processing compounds containing glitter and special-effect masterbatches.
The aesthetic standards required by the cosmetic industry leave virtually no room for colour variations, poor pigment distribution or process instability.

The Technical Challenge

The initial request was to improve the visual appearance of the finished product.
A technical analysis carried out by Euroviti demonstrated that the issue was not related solely to the masterbatch itself, but to the entire plasticization process. The original screw geometry did not provide the level of melt homogenization required for these demanding applications.

Euroviti’s Engineering Approach

Rather than reproducing the OEM screw, Euroviti developed a completely new screw profile specifically engineered for this application.
The new geometry was designed to:

• improve melt homogenization;
• optimize colour and glitter dispersion;
• maintain stable melt temperature;
• control material residence time;
• preserve process stability and productivity.

The project was initially developed for a single machine and subsequently extended to three different plasticizing unit sizes belonging to the same machine family.
Following the success of the first installations, the same screw geometry has now been successfully adopted by several processors operating with the same technology, becoming a proven solution for this specific application.

Beyond the Screw

The experience gained during the project also led to the redesign of the screw-tip assembly (tip, valve and seat ring) for an international customer operating multiple production plants.
The new non-return valve geometry improved melt flow control and helped standardize process performance across different production sites, ensuring greater consistency in product quality.

Results

The customized screw profile delivered significant process improvements:

• Better colour and glitter dispersion
• Higher aesthetic consistency of the finished product
• Improved process repeatability
• More uniform cooling of moulded parts
• Reduced cycle times

The subsequent optimization of the screw-tip assembly further improved melt flow control and process consistency across multiple production facilities.
This project demonstrates how modern plasticizing units are no longer simple replacement components. When engineered around the material and the production process, a screw can become a powerful tool for improving product quality, process stability and overall manufacturing efficiency.