Electric screw actuators are the most common type of calender roll end positioning system. The screw and nut operate under very high loads and thus experience significant wear even with proper lubrication.
As the actuators wear, back lash develops. As the back lash increases, the response to small changes or corrections deteriorates. Also with increased backlash the number of corrections required would increase, which in turn causes increased wear.
In addition, most calenders still have fixed speed electric motors with mechanical brakes. The breaks particularly need periodic maintenance. Sticky brakes will adversely affect gauge control results.
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