Tomorrow morning I will use the laser to measure backlash and travel. But I'm pretty sure it's the rubber belt stretching. To partly test that I'll try lessening the tension on the belt. I can see how bearing friction could make the belt stretch. It is only .0009" after all. Since I'm used to working to "tenths" they seem bigger to me than they really are. Since micrometers and indicators amplify the reading it's easy to regard them this way. The system as it stands now consists of the encoder shaft riding in ball bearings and two other wheels made of plastic riding on polished steel shafts. At first this seemed fine but now it doesn't. I thought about using 50 lb. test stainless fishing line but it is plastic coated. Maybe McMaster-Carr has some good cable or belting. But belting of any type is probably no good because the coating around the fibers is compliant. And the final encoder setup needs to work well because it's for the Z axis of the lathe and the X axis is going to have the added complication of doubling the encoder travel with respect to the actual X axis travel. It may be that using an encoder shaft .15915 in diameter will work but that's a pretty small diameter to be bending the cable around. The cable would have to be very flexible and not very stretchy. ERS
- posted
18 years ago