kamenges
Electrical
- Oct 3, 2002
- 17
I recently had a customer contact me about a tension control issue on his machine, a web processing machine wiith loadcell based tension control. He said the machine ran fine except for a small speed range during accel and decel. I had seen this before and told him the machine was passing through a speed that caused the loadcell roll to rotate at the roll shaft natural frequency.
I went to his site and performed a test to excite the shaft and measure the natural frequency. I found the shaft natural frequency was exactly twice what I expected it to be, which caught me by surprise.
I found multiple references to excitation at half critical speed. However, the explanation provided by Roisum and Hartog seem to require a liveshaft roll or rotor of some type. They require either variable shaft springrate or variable shaft tangential loading due to imbalance, neither of which apply to deadshaft idlers.
i looked at this thread which was related (thread384-103687 ). But I can't find any explanation that directly applies to my case. Can I just assume there is a fairly imperceptable impact load that is causing the vibration or is there an explanation for half critical excitation that applies to deadshaft idlers?
Thanks,
Keith
I went to his site and performed a test to excite the shaft and measure the natural frequency. I found the shaft natural frequency was exactly twice what I expected it to be, which caught me by surprise.
I found multiple references to excitation at half critical speed. However, the explanation provided by Roisum and Hartog seem to require a liveshaft roll or rotor of some type. They require either variable shaft springrate or variable shaft tangential loading due to imbalance, neither of which apply to deadshaft idlers.
i looked at this thread which was related (thread384-103687 ). But I can't find any explanation that directly applies to my case. Can I just assume there is a fairly imperceptable impact load that is causing the vibration or is there an explanation for half critical excitation that applies to deadshaft idlers?
Thanks,
Keith