The 1100-kg/hr V-PET Model packaging sheet line from Welex features a 130-mm vented extruder and minimizes the need for predrying A-PET. This size of hopper-to-winder sheet extrusion system was developed specifically to satisfy the demand for lines that produce 1 ton/hr of thermoforming sheet. It can also run HIPS at similar capacity or PP at somewhat lower capacity, without any changes.
After experimenting with different roll configurations, it was concluded that the vertical roll arrangement offers the optimal configuration for all packaging sheet applications. This take-off features a compliment of 300/600/600-mm rolls in a downstack configuration. The upper roll set uses a deflection compensating design for perfect sheet flatness. The rolls are cooled via a closed loop refrigerated water system with modulating valve control for stepless control. Each roll has a circulating volume in excess of 40 cu m/hr (100 gpm) for closest temperature uniformity.
These double shell rolls are also distinguished by relatively thin outer shells for maximum heat transfer. The thin outer shells are supported via spiral baffles by a heavy inner shell for rigidity. All of these rolls are surfaced with welded stainless steel overlay under hard, mirror-finish chrome plating. This ensures resistance to deformation by a hardened PET sheet, and at the same time allows the use of thinner outer shells than are possible with conventional prehardened tubing, which is only available in a limited range of dimensions.
A single digital a-c vector drive powers all rolls with a chain drive system. Pneumatic roll closing permits the precise and gentle roll pressure control required for PET sheet. A thickness gauging and control system is used to maintain desired minimum sheet thickness.
The finished sheet is wound on a centerless turret winder with precision tension control to produce rolls up to 1200 mm in diameter. An integral sheet accumulator is included for roll change at low speeds. The entire line is controlled and monitored by a Windows-compatible pendant-mounted microprocessor control system.
Blue Bell, PA