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Twin screw gearbox reliability

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BamaSlammer

Mechanical
Apr 11, 2013
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I work in a facility running 5 twin screw co-rotating extruders processing polyamides. All 5 of the extruders run Eisenbeiss gearboxes, 3 are their “high torque” versions and 2 are standard torque. We’ve been plagued with issues with the high torque units since day 1. We understand the root cause of our issue and working a path to correct. Essentially, the helical gears on the output side of the gearbox generate a force in the direction of the process that is dependent on torque, we do not generate enough process pressure to counteract the gear force so our net force is in the process direction. The thrust bearing on the process side of output shafts is tiny so we see a failure in this bearing. The design intent of the gearbox is to have net force towards the gearbox into a much larger thrust bearing.

On to the second part… The standard torque gearboxes have historically been much more reliable for us even though they have a similar design. Likely do in part to the fact they run at lower torque levels then the high torque boxes. But recently we have seen a severe decline in reliability of these boxes as well, same failure mode as the high torque boxes. We have not made changes to our process.

Has anyone else experienced similar issues with Eisenbeiss or other manufacturers of twin screw co-rotating gearboxes?
 
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