Manufacturers of premium cosmetic packaging using injection stretch blow moulding machines from a leading Japanese manufacturer faced a similar processing challenge. The issue was to achieve adequate colour dispersion when processing compounds containing glitter and special-effect masterbatches. In the cosmetic packaging segment, aesthetic requirements are particularly high, so colour deviations, uneven pigment distribution or process instability can directly affect the perceived quality of the finished product. A technical analysis carried out by Euroviti showed that the source of the problem could not be linked solely to the masterbatch itself. The entire plasticization process was significant, particularly the geometry of the original screw, which did not provide the level of melt homogenization required for such demanding applications. The initial goal of the project was to improve the appearance of the finished product, but in practice the scope of work covered a broader optimization of processing conditions and plasticizing unit components.
Instead of reproducing the OEM solution, Euroviti developed an entirely new screw profile specifically designed for this application. The new geometry was intended to improve melt homogenization, optimize the dispersion of colour and glitter, maintain a stable melt temperature, control the material residence time in the system, and preserve process stability and productivity. The project was initially prepared for one machine and then extended to three different plasticizing units belonging to the same machine family. Following the success of the first installations, the same screw geometry was then also adopted by several other processors using the same technology. As a result, the solution became a proven configuration for this specific application.
Optimization beyond the screw
The experience gained during the project also led to the redesign of the screw-tip assembly, including the 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 parameters across different production sites. The purpose of these changes was to achieve greater repeatability and more consistent product quality between plants.
Implementation results
According to the project description, the use of the customized screw profile delivered a number of process and quality effects. These included better dispersion of colour and glitter, higher aesthetic consistency of the finished product, improved process repeatability, more uniform cooling of moulded parts, and reduced cycle times. Further optimization of the screw-tip assembly was also reported to improve melt flow control and process consistency across multiple production plants. This example shows that modern plasticizing units are no longer merely replacement components. When designed with the material properties and process specifics in mind, they can become a tool for improving product quality, production stability and manufacturing efficiency.
