x belt grinds against idler flange [Solved]

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Re: x belt grinds against idler flange

Postby bdring » Fri Apr 27, 2012 7:03 pm

On my unit the belt does rub the one bolt ever so slightly. I have known about that since the beginning and decided it was not something to worry about.

Initially the step was a little thicker, but a few of them were a tight fit, so I gave extra room for the belt. If you clamp it right you can get it to stay flush with the plate.

The only real solution is to increase the space below the carriages. I always wanted a few eccentric spacer height options, but shortest possible height yields the stiffest machine.

Right now I don't plan to change the design.
Bart
"If you didn't build it, you will never own it."
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Re: x belt grinds against idler flange

Postby rogue555 » Fri Apr 27, 2012 8:44 pm

dzach wrote: It looks like the belt clamp step, which gives the belt a guard distance from the gantry plate, is 0.5mm too high.


My kit included the two-part belt clamp. I had thought the belt would go directly against the carriage plate. How does it look if you flip the clamp around so the other face is against the carriage?
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Re: x belt grinds against idler flange

Postby dzach » Fri Apr 27, 2012 10:37 pm

rogue555 wrote:My kit included the two-part belt clamp. I had thought the belt would go directly against the carriage plate. How does it look if you flip the clamp around so the other face is against the carriage?

With this arrangement, the part of the belt that comes into and leaves the clamp is stationary relative to the plate so even if they touch it might not cause the belt to wear. However, the height of the belt in its return path, which is not stationary related to the plate is mostly set by the clamp's step so if this is eliminated by flipping the clamp around then the moving gantry plate will possibly be rubbing the moving opposite part of the belt

I was thinking of lowering the clamp step by about 0.5 mm, but will rather leave it for later since the touch is very little.

The limit switch on the gantry might also touch the belt but it too is stationary relative to the plate so no wear can happen there either.
2012-04-27-180514.jpg

By the way, the aluminum spacers seen in the picture replaced the nylon x-axis stepper spacers.
Boy! is this machine rigid!
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Re: x belt grinds against idler flange

Postby dzach » Sat Apr 28, 2012 1:07 pm

bdring wrote:[...]If you clamp it right you can get it to stay flush with the plate.
How can I do that without overriding the step?

In any case, I reduced the clamp by 0.8mm by grinding the step side and now the problem is gone: turning the belt in one direction leaves an approx. 0.4mm gap while in the other direction I can just see the light passing between the belt and the screw head. Reducing the step by 1.0mm could possibly be best.

Here is how it looks:
2012-04-28-145555.jpg

2012-04-28-145348.jpg
The other side of the clamp is untouched.
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Re: x belt grinds against idler flange

Postby movlw » Sat Apr 28, 2012 8:12 pm

Thanks for all the suggestions regarding my problem.

I tried out some other M5 bolts, both screw and nut from the hardware store. Also tried replacing the nylon standoff with three steel washers but all attempts had similar problems.

I'm not exactly sure what fixed the problem as I performed a few things at once. I did file ever so slightly on one end of the nylon spacer where I thought it possibly looked uneven. I also enlarged the center hole very little with a round file since the nylon standoff initially was really tight on the screw which made the screw thread the nylon the last few millimeters instead of it moving freely on the screw. I also loosened up the motor mount, idler pulley mount and retightened everything.

After these actions the problem is gone, or rather the opposite of it, the belt is now riding a bit low but not so much grinds so I am happy with that. Things sure are tight around the belt drives and I agree with dzach that some small modifications will be good for improved clearance.

Love the machine. It looks great. Can't wait for the electronics and filament to arrive.
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Re: x belt grinds against idler flange [Solved]

Postby cozmicray » Sat Sep 22, 2012 2:40 am

I saw this problem on my current build of Hadron (ATI kit).
It appears the idler has a cupped side (bearing down inside delrin)
and a proud side (bearing sits up above plastic)
I found that that putting the cupped side down with the nylon spacer
lowers the belt so it won't rub.

I was ready to make up thinner nylon spacers but this seems to have solved it.

I guess you have to be careful to just clamp the inner race of the bearing
so it spins on bearing and just doesn't spin on bolt, or binds up the bearing?

This applies to all the wheels on the build.
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