COMPOUNDING: New Device Automates Screw-Element Tensioning

No more torque wrenches needs to manually tighten segmented screws.

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KraussMaffei Berstorff  has developed A hydraulic device to facilitate the screw tensioning in twin-screw extruders and ensuring reproducible installation and pre-tensioning.

Before this development the common practice has been to tighten the segmented screws with a torque wrench. However, this method is subject to certain tolerances and, in the case of reconfiguring, involves a large amount of time. The pre-tensioner from KraussMaffei Berstorff applies an always reproducible, defined tensile load to the screw shafts, but no longer any torsional stress. The device is said to be easy to operate: The operator selects the correct pressure from the machine documentation and clamps the screw outside the extruder in the pre-tensioning device.

The system, consisting of screw mandrel, screw part and screw cup, is tightened at the press of a button in the elastic range using a high-performance hydraulic pump.  In addition to the time savings, the hydraulic pretension provides another positive “side effect” with clear cost benefits: The defined pretension forces prevent the melt from infiltrating between the screw part and screw mandrel. This avoids time-consuming and cost-intensive work such as disassembling or cleaning the extruder.

The device is available on the company’s ZE BluePower, ZE-UTX and UltraTorque (UT) series.