Introduction of the straightening machine
Straightening machines have been built with various methods of driving the rolls. Some machines have a separate drive motor for each roll, whereas the majority of modern machines usually use 2 drive motors, one motor for the top set of rolls and one for the bottom rolls. Regardless of the way the rolls are driven it is important that all rolls revolve at the same speed within about 1 to 2 rpm at maximum machine speed. In addition it is usual for the manufacture to build in an electronic load sharing system to ensure that the power needed to straighten is shared equally between the driving motors. Each time the rolls are changed a check of roll rpm and motor loading should be carried out.
If the rolls are not revolving at highly similar speeds, under load, tube straightness will be poor, roll wear will be rapid and under high straightening loads the motors may run out of power and stall.