To conduct automated tolerance tests

The drawing die consists of two die lips:
- a “fixed” lower lip that operators adjust only to preset,
- an upper lip that can be adjusted manually or automatically.
The gap between the two lips -called the air gap- depends on the desired thickness of the product.
The upper lip can be adjusted thanks to 66 heating bolts cartridges that are distributed all along the top of the die lip. The heating bolts cartridges have to be adjusted one at a time, either manually by the operator by means of a key, or by "heating/cooling". While heating causes the heating bolt cartridges to dilate and the die lip to close.
At the calender's exit, the extrusion unit is equipped with a scanner that continuously measures the sheet thickness.
The measurements are displayed on the screen of the control system, and the information is then processed by the system that induces the opening or closing of an area of the upper die lip according to the measured thickness, in order to guarantee an extruded section of regular and constant thickness.
At the same time, according to the measured average thickness, the system automatically accelerates or decelerates the calender, to guarantee an average thickness within a specified range.