Reduction of Production Costs and Improvement of Pipe Quality by Using Flex Ring Dies

Conventional pipe dies normally have no means to get rid of unsymmetrical differences of the local melt stream around the circumference of the die. That is why, even after the die has been centered in an ideal way, all produced pipes have thickness tolerances over their circumference. The development of Flex Ring Dies makes it possible to alter the gap of the flow channel at the die exit in a restricted region in regard to the circumference of the die. The revolutionary new die system brings the line operator into the position to slightly change the flow channel geometry at the exit of the die. It is comparable to slit dies used for film production where it is state of the art since many years to minimize tolerances in the film thickness by optimizing the gap at the exit of the die by locally adjusting the flexible lip. The adjustment of the flow channel gap at orifice of the Flex Ring Dies is accordingly achieved by deforming the flex ring at every wanted location according to the actual need while the line is running. As a rule conventional pipe dies can be easily retrofitted with a Flex Ring Tubing. It can be deformed purely elastically in a wide range, as it is partly multi-walled and as the single walls are extremely thin. By deforming it the geometry of the flow channel alters gradually so that no dead spots arise when adjusting the die. A new level of thickness constancy which is impossible with conventional dies can thus be reached.