Peter C. Wallace wrote: >> > Like Jon Elson said, check the encoders. ISTR a situation where a hair > in the encoders got pulled into the sensor area in one direction of > rotation and pushed away in the other direction, so it only lost > counts in one direction! Any dirt, oily mist, coolant that has crept past seals, etc. can foul the optics in an encoder and cause difficult to reproduce problems like this. It can also be VERY hard to fix, depending on encoder construction. Some are quite easy to get into, and there is a place where at least the encoder disc can be very gently swabbed with alcohol on a Q-tip. You can't clean the analyzer gratings without removing the disc. This can be done pretty easily on modular encoders, but can be almost impossible on "can" encoders which were never designed for service. Improper loads applied to the shaft due to misalignment or just long hours running back and forth can wear out the bearings and cause the disc to crash into the gratings, wearing off the fine stripe pattern. Then it is just time for a whole new encoder.
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