Flexipet Unveils Redesigned PET Thermoforming Sheet Extrusion Line
SML announces the launch of the FlexiPET, a brand-new production-scale demonstration line for thermoforming sheet located at SML’s Technology Centre. The sheet extrusion line features a completely redesigned machine architecture, and delivers smart innovations at every level: most notably SML’s new twin-screw extruder TSE80 for polyester, a modernised roll stack, and the new W650 winder.
The FlexiPET is a co-extrusion sheet line configured for a classic 3-layer structure (A/B/A), but which also has the versatility to operate as a 2-layer line (A/B) as required.
Extrusion excellence: TSE 80 combined with high-performance vacuum unit
“At the heart of the line lies the new TSE 80 – a state-of-the-art parallel co-rotating twin-screw extruder designed in-house by SML and specifically optimised for PET,” explains Martin Kastner, R&D Engineer at SML. Equipped with a low-maintenance, water-cooled main drive delivering 348 kW, the TSE 80 achieves an output capacity of up to 1000 kg/h for PET.
The TSE 80 demonstrates exceptional material versatility. It is optimised for processing large volumes of materials with low bulk densities – such as flakes or regrind. The concept is also an excellent choice for processing PET/PE flakes, as well as PETG and its post-industrial flake stream (GAG). With its compact design, the TSE 80 ensures high rates of energy efficiency. In addition, the short residence time in the extruder retains the natural, clear colour of PET, preventing the yellowing of the film.
To ensure the highest melt quality for processing PET without pre-drying, the TSE 80 is combined with SML’s high-performance vacuum unit. This frequency-controlled two-stage vacuum system employs a roots vacuum pump for high volume flow rates with a dry-running rotary screw pump for low pressure levels. This configuration achieves absolute pressure levels as low as 1 mbar. Due to the dry-running vacuum pumps, the unit ensures high levels of energy efficiency and environmental compatibility.
A gravimetric batch blender with three stations for main components (virgin, flakes, regrind) and two additive dosing stations offers expectional flexibility for complex formulations.
The co-extruder in the FlexiPET line is an SML single-screw extruder (ES 60/28D) powered by a 64 kW main drive motor. It is designed for processing pre-dried material with an output of up to 200 kg/h for PET.
Precision calendering
Downstream, the horizontal roll stack ensures a high specific output, even for thin gauges as low as 150 µm. It uses the proven Smart Parallel Gap (SPG) polishing roller technology for superior thickness tolerances. “A major innovation is the roll stack movement, equipped with servo positioning drives and linear guides, which enables precise, 100 % reproducible positioning in both the horizontal and vertical directions,” Martin Kastner continues. This feature includes automatic start-up processes, collision protection between the roll stack and flat die, and the ability to store production positions in the SMILE control system. The design complies with Calander standard DIN EN 12301-2021-12, ensuring safety without affecting the visibility of the smoothing roller gap.
W650: new winder for thermoforming film
The FlexiPET concludes with the new W650 winder, a development that combines the best of two worlds. It offers the user-friendly roll handling of a cantilever winder – where the shaft remains in place during changes – combined with the large winding capacities of an A-frame winder (diameters of up to 1,500 mm and 2,000 kg roll weight). A movable winding shaft support ensures the production of perfectly straight-edged reels.
The W650 basic version also includes semi-automatic cantilever operation with automatic cross-cutting via flying knife. Energy-efficient asynchronous servo motors with resolver feedback, combined with SML’s in-house winding controller, enable precise winding from the first layer. The W650 is fully modular and can be upgraded with optional modules for specific requirements, such as FFS winding or the processing of two webs on a single shaft. All these modules are currently installed on the demonstration line at SML’s Technology Centre.
Key facts:
- Maximum output: up to 1,200 kg/h of PET
- Layer structures: A/B/A or A/B
- Thickness range: 150 – 1,400 µm
- Final net film width: up to 1,000 mm
- Winding diameter: up to 1,500 mm
- Number of webs: up to 2
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