Shapeoko 3 belt tensioning technique(s)

Assembly questions and answers for the Shapeoko 3 CNC Mill
WillAdams
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Shapeoko 3 belt tensioning technique(s)

Post by WillAdams » Fri Apr 17, 2015 12:28 pm

Okay, got mine pretty much together and after a successful jogging last night will be back to tensioning the belts.

Initially, I'd misliked the idea of slots and ovals for the motor mounting, but on the way in to work this morning had the idea of taking advantage of them and the weight of the machine to get consistent belt tension:

- position the motors at their lowest point
- connect the belts, trying to make them reasonably and consistently tight --- ensure that they're centered in the too wide (and ready for upgrading to wider belts!) slots

in turn:

- slide the carriage to the opposite side and center the gantry
- loosen the motor on the side opposite the carriage
- lift the machine up by the motor
- tighten the motor

- repeat that for each motor --- belt tension will be equal (same half weight of the machine) for the Y-axis

Does that seem like a reasonable technique? is ~half the weight of the machine a reasonable amount of tension? Anyone have suggestions on the Z-axis?

Anyway, if Edward already came up w/ this idea, great minds think alike and all that.
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Hans
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Re: Shapeoko 3 belt tensioning technique(s)

Post by Hans » Fri Apr 17, 2015 12:39 pm

It's a very innovative way to get consistent tension out of the box, but what happens when you upgrade? Tension will still be even between belts, but it could become twice as much with a size increase. Did you try the frequency method talked about in this thread? http://www.shapeoko.com/forum/viewtopic.php?f=7&t=5827

I'll be giving the app a try myself this weekend.
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WillAdams
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Re: Shapeoko 3 belt tensioning technique(s)

Post by WillAdams » Fri Apr 17, 2015 4:23 pm

Yeah, the app is neat, and better than my previous idea of using a guitar tuner.

Upgraded machines will definitely need something different, but I was hoping this would be useful for the base case scenario of a stock machine.
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Hans
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Re: Shapeoko 3 belt tensioning technique(s)

Post by Hans » Fri Apr 17, 2015 4:40 pm

I do think your idea is about as good as it gets for stock tensioning. Total tension should be 10-12 pounds from this method, based on half of a ~55 lb machine over two sides of the belt minus a little friction. Based on my research (not experience, because I dunno how tight my MXLs are), that's right in the butter zone for the stock belts.
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WillAdams
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Re: Shapeoko 3 belt tensioning technique(s)

Post by WillAdams » Fri Apr 17, 2015 11:05 pm

Thanks!

I just finished tensioning the belts on my machine and they seem good and consistently taut.

Finishing up some odds and ends, then have to make up an adapter and see about repurposing the dust shoe I have and I should be good to cut.
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Hans
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Re: Shapeoko 3 belt tensioning technique(s)

Post by Hans » Mon Apr 20, 2015 6:03 pm

Update on the app: didn't work for me. My belts aren't loud enough for the app to read them. I think I could get a louder tone if I could get the tension higher, but the original raised belt configuration doesn't allow much tension and is difficult to adjust.
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twforeman
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Re: Shapeoko 3 belt tensioning technique(s)

Post by twforeman » Tue Apr 21, 2015 9:53 pm

I actually did not use this method to tension my belts. I found I got a pretty good amount of tension just by leaving the bolts for the belt anchor loose, pulling the belt tight, and then tightening the belt anchors.
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edwardrford
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Re: Shapeoko 3 belt tensioning technique(s)

Post by edwardrford » Tue Apr 21, 2015 10:13 pm

Tim - your method exactly the method to use. I'll mention that in the instructions during the next revision.

The intended routing is as follows:
1.) Over top of clamp to rear slot
2.) Down through rear slot
3.) Back towards front of clamp
4.) Up through front slot
5.) The belt should now be pointing in the reverse direction as it started.

I'll try to add an image to help clarify.
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WillAdams
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Re: Shapeoko 3 belt tensioning technique(s)

Post by WillAdams » Wed Apr 22, 2015 12:55 am

twforeman wrote:I actually did not use this method to tension my belts. I found I got a pretty good amount of tension just by leaving the bolts for the belt anchor loose, pulling the belt tight, and then tightening the belt anchors.
I did that first, but then I couldn't get the tension even betwixt the two Y-belts.
edwardrford wrote:Shapeoko 3 #2 - Stock
Hey! What happened to #s 0 and 1?
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edh
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Re: Shapeoko 3 belt tensioning technique(s)

Post by edh » Wed May 13, 2015 8:02 pm

Here a link to the belt routing in case anyone needs it. Edward was kind enough to share this with me when we were working through an issue.

This is from a SO2, but should be a good visual.

http://docs.shapeoko.com/content/belt-r ... ng-066.jpg

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