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Z belt tension

Posted by reece.arnott 
Z belt tension
July 27, 2008 09:05PM
I've been stuck trying to get the Z belt tension correct. I've read through the troubleshooting tips Ed put up and fixed a couple of minor issues. However, my main issue is the Z belt tension. I'll make this quite detailed so others can use my methods in the future.

I've respliced the Z belt a few times to try and get a belt thats almost right and just tighten it up but I'm having a few issues figuring out exactly what the issue is.

I resplice the Z belt by taping down the belt to the idlers on either side of the previous splice then I cut the belt at the splice point, run nail polisher over the superglue to unbind it and they dry it off and insert another piece of belt (the joining pieces have been filed as per the join instructions) and resuperglue it to the belt. This means I have the original belt plus an additional piece superglued at two points (my original belt was just a bit short).

Then, instead of using the tie brackets to put tension on the belt I've got a linked chain of cable ties that form a cross in the middle of the darwin structure with the tie in the end of each chain around the belt. This gives four additional places where you can tighten (but not loosen) the belt.

There is a critical point at which to get the right tension on the Z pulley and idlers the belt has to be pulled out of alignment too much and I should resplice the belt with a shorter additional piece but I'm not sure when that is.

There is another point at which the belt doesn't have enough tension and so the belt doesn't mesh with the teeth of the pulleys.

And of course, theres the point at which there is too much tension and the friction is too high for the pulleys to move the Z rods.

Also this is complicated by the fact that I am wearing down the teeth on the Z idlers and the belt so at some point its just not going to work.

My main problem is I'm not sure what signals that I've gone past these critical points. Could someone give me a quick list of things to look for and test.

The main thing seems to be that running the Z motor at low speeds the Z belt seems to slip over the rotating teeth most of the time no matter what I do.
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