Some photo's of how your X axis pulleys are mounted ?

Bearings/Motors/Belts/Gears/Etc.

Some photo's of how your X axis pulleys are mounted ?

Postby educa » Sun Jan 01, 2012 8:50 pm

Could somebody please take some pictures of how the pulleys are mounted on the x axis on a 2.x machine?

I have seen drawings, but most are deprecated (and using an ugly screw as axis) , so I wonder how you mount both pulleys ?
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Re: Some photo's of how your X axis pulleys are mounted ?

Postby bdring » Sun Jan 01, 2012 10:54 pm

I think the 11/9/2011 rev drawing on the drawings page is correct.

Here is a link

http://www.buildlog.net/cnc_laser/erp/g ... ber=D30043

Here is a clip. Is this what you are talking about? The screw is still the axis, but the screw no longer rotates. This means no matter how many things contribute to inaccuracies the runout is only in the bearings.

gantry pulley.jpg
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Re: Some photo's of how your X axis pulleys are mounted ?

Postby educa » Sun Jan 01, 2012 11:05 pm

Thats indeed what I was talking about.

So you attach the pulley with a screw as axle and then in the so called bearing block you just fix the screw ?

Doesn't that loosen up?

Are there no ball bearings used in this ?

Regards,

Bart
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Re: Some photo's of how your X axis pulleys are mounted ?

Postby educa » Sun Jan 01, 2012 11:26 pm

by the way Bart, what size of aluminiumextrusion do you use on that x axis? it looks like width is twice the hight?
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Re: Some photo's of how your X axis pulleys are mounted ?

Postby bdring » Mon Jan 02, 2012 12:31 am

The screw is fixed to the bracket. Bolted to the screw are 2 bearings separated by a spacer. A delrin wheel presses onto the two bearings. The dual bearings virtually eliminate any axial wobble. The spacer makes sure only the inner races contact. The smooth idler, as I call it, is used in at least a dozen open source designs and everyone so far has liked it.

This image shows an exploded view next to a completed assembly.

smooth_idler.jpg
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Re: Some photo's of how your X axis pulleys are mounted ?

Postby szx » Mon Jan 09, 2012 6:10 am

A somewhat related question: it looks like the nylon spacer is bigger than the metallic part of the inner race (but on the other hand so is the shim washer). I was wondering what's the maximum diameter that spacer, or nut for that matter, can be without interfering with rotation. I see the laser design uses both .312" and .375" OD nylon spacers for the idler wheel and v-wheel respectively, so I'm guessing either works?
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Re: Some photo's of how your X axis pulleys are mounted ?

Postby bdring » Mon Jan 09, 2012 1:59 pm

The inner race protrudes slightly beyond the shield so the metal spacer between bearings is not a problem. The nylon spacer normally should not be a problem, but the surface of some of the larger diameter spacers is cupped slightly or has mold flash. I think this is due to shrinkage after molding. Some people have reported that when the larger diameter spacers are tightened very tight, the inner race can cut into the the spacer. That, along with the cupped surface, can allow a little rubbing of the spacer on the shield. I have not seen/heard that on the 0.312 spacer. I am looking for a low cost metal spacer in the less than $0.25 range at a 1000 piece order.
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