The plant has a “dip and bake” operation in which parts are dipped into a varnish vat and then run through an oven tunnel to dry. This is all on a conveyor; the parts hang on hooks.
The conveyor motor is the frequent subject of calls to the maintenance department. Most of the failures occur on third shift, but some occur early on the first shift. A recording digital multimeter (DMM) found no power spikes, the motor is correctly sized for the application, and no varnish has been found on the motor.
How might you find the likely culprit?
The DMM isn’t the best tool for capturing power events, but if you had power problems this would not be the only frequent failure. The timing is instructive. Unless there is some gross temperature change in the varnish area on third shift, suspect operator error. Find a way to observe without being observed.
This was a real case. The operator thought the parts should stay in the vat longer, so he would sometimes stop the conveyor by jamming a long metal rod into it. When maintenance personnel were visible in the area, the operator didn’t do this. But thanks to a newly installed camera, their suspicions were confirmed.
