How you can benefit from a mechatronic polishing stack in the production of thermoforming sheets

Technology

Flat Film

Manufacturers who cool, polish and shape their thermoforming sheet with high precision in the extrusion process achieve better product quality. The mechatronic polishing stack from the MIREX-MT series allow precise and reproducible adjustment of the roller gap. They therefore enable fast film thickness changes and increase the OEE of the thermoforming sheet line enormously.

A precise polishing stack is the starting point for high film quality. After all, it ensures that the plastic melt is cooled, polished and shaped in thermoforming sheet lines. “The polishing stack is crucial for ensuring that the plastic films later perform as they should,” says Mark Schuster, Product Manager, Reifenhäuser Cast Sheet Coating.

Very good initial quality of the thermoforming sheets

For example, the polishing stack influences the surface quality and thermoforming properties of films that are processed into tubs and trays for margarine, meat and fruit as well as coffee capsules. “Our customers benefit from our patented MIREX-MT polishing stack technology,” explains Schuster, “Thanks to more precise gap adjustment compared to other processes, we achieve a very uniform thickness profile even with larger film widths, which in turn improves the thermoforming properties. Precise control of the roller drives, coupled with good temperature control of the film in the polishing stack, enables us to achieve outstanding shrink properties that are unparalleled on the market.”

Significantly thinner films

In combination with the high precision, the high feed forces allow the production of extremely thin films. “With PET, we can reduce the thickness to as little as 100 µm,” says Schuster. By further developing the raw materials and the subsequent thermoforming process, material consumption can be reduced and an important contribution made to sustainability.

Plastic material	Minimum film thickness (in µm) depending on MIREX-MT type	Maximum film thickness (in µm) depending on MIREX-MT type
PET	100 - 200	2,500
PP	200 - 400	2,500
PS	200 - 300	2,500
PLA	250	2,000

Precision taken over from CNC machines

The MIREX-MT polishing stack differs from other systems in that it has a mechatronic drive unit. The absence of a hydraulic system saves energy and guarantees clean production, even in clean rooms. “The mechatronics of our systems are based on CNC machines, which work very precisely in milling and turning technology,” explains Sofija Bertasa from the Technical Sales Team at Reifenhäuser Cast Sheet Coating. Accordingly, the calenders can be adjusted fully electrically, but are also very easy to operate. The system is also integrated into the c.Hub digitalization solution from RE: GmbH, which leads to data transparency in production. This allows machine operators to keep an eye on all process parameters in real time and make quick adjustments if necessary. The process parameters required for product changes can be loaded onto the system from the recipe management system within seconds.

“It was important for us to make it as easy as possible for machine operators to control the systems. Both in terms of recipe management and operability,” says Bertasa. This has several advantages for manufacturers:

Product qualities are 100 percent reproducible

The position of the rollers in the polishing stack does not have to be changed manually. With MIREX-MT, the operator enters the desired gap dimensions into the system and the rollers are automatically and precisely positioned mechatronically. The desired gap dimension can therefore be reproduced 100 percent.

Faster start-up times and product changes

This also enables faster start-up times and product changes. Thanks to the mechatronics, the rollers can be brought into the correct position twice as quickly as hydraulic systems. This is an invaluable advantage when several different products are running on the system during a shift, each of which requires the polishing stackto be adjusted.

Save material and reduce waste

Faster start-up times and product changeovers also enable manufacturers to maximize their output, use raw materials efficiently and avoid waste.

Thanks to the mechatronic polishing stack, we can increase the OEE of our extrusion lines by 1.5 percent or more. Manufacturers can produce up to 100 tons more film per year on systems with an output of 1,000 kg/h. That is a clear competitive advantage.

Mark Schuster

Product manager, Cast Sheet Coating

Vertical, horizontal or inclined roller arrangement

The Mirex-MT polishing stack is not only installed in new Reifenhäuser Cast Sheet Coating systems. Reifenhäuser can also retrofit existing systems with the system. Manufacturers can choose between different types of MIREX-MT technology. They differ, for example, in the arrangement of the rollers - optimized for the requirements of different raw materials and products.