For what ever reason, we have a piece of equipment that employs
2 hollow shafts both with timing pulleys on the end of each and the inside pulley gets magnetized.The inside unit happens to be connected to the outer hollow shaft. these 2 shafts turn at different speeds and such that we have prox's mounted on a nonferrous plate aligned vertical into the timing teeth of these pulleys.
just picture 2 hollow shafts, one fits inside of the other, both having a pulley connected to them on the same end.
Both Prox are of the same type etc, I discovered a problem where the inside pulley had critical issues allowing the prox to properly sense the passing timing teeth. At slow RPM's it seems to work fine how ever, as RPM's increase the sensor goes into a latched output effect and simply stays in a constant on state, this is obvious via the monitoring equipment connected to it and scope I used. Pulling the prox away from the pulley allows for higher RPM's to develop before the output turns to a constant one state.
These units are basic N.O. NPN output..
Trying to assess as to why the pulley becomes magnetized which is causing the problem here.
I guess a mechanical engineer may have an answer to that. I did observe a mechanical thumping noise that could be a bearing issue on that shaft that has the magnetized pulley.
Apparently hitting it a few times with a hammer fixes it for a short period. I'm not a mechanical engineer but I do have some ideas in the back of my head on how to neutralize the mag in the pulley..
Any idea's?