More thoughts on encoder mounting

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

Reply to
Eric R Snow
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Consider Spectra cord, available from Small Parts in various sizes by the foot. It is very flexible, while being considerably stronger than steel. I don't know how it's "stretch" compares to steel, but it doesn't stretch much!

Reply to
Don Foreman

I seem to recall being rebuked for suggesting that would happen.

Reply to
Richard J Kinch

Stronger? Cite some figures.

Reply to
Richard J Kinch

Eric R Snow wrote in news: snipped-for-privacy@4ax.com:

Eric, You are not using a timing belt to drive the encoder? You most certianly need a positive drive mechanism, such as a timing belt. All of our belt driven encoders are timing belts, and we machine to 0.001 mm (0.000039") tolerances.

Anthony

Reply to
Anthony

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