Originally Posted by
jalsina
Mike,
You mentioned that the idler bearings should be positioned .002" to .005" above the top of the upper belt surface. For people not using super-straight 8020 and the like, it could be very hard to ensure that the suface supporting the belts is parallel to the linear guides within such a small tolerance, especially over longer distances.
I thought about spring-loading the idlers, but the tension would have to be greater than the force exerted on the belt, or the belt would lift the idler up instead of the idler keeping the belt down. But a 425 oz-in stepper with 4:1 belt reduction and a 10-tooth T5 drive belt could exert more than 300 lbs on the belt. I don't think the belts would like being pushed on with that kind of force 24 hours a day. Ditto for the linear bearings and rails.
Any suggestions on how to address this issue? Thanks.
Well, that .002-.005 is just ideal for tooth engagement. As the gap gets bigger, it's easier to pull the belt out of engagement down below, then ZZZZZrpp, and you have to reset everything. The closer you get the belt to the linear bearings, the better. spring loading wont kill it, I think, but as you say, spring force needs to me more than your max linear drive force.
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