Shapeoko 3 XXL belt skipping

I’m starting to become rather frustrated because I find myself constantly duking it out with the Shapeoko 3. I finally have been able to use it the other day and now it’s not homing correctly and belts are skipping when doing rapid positioning.

What do I have to fix now?

Belt skipping:

Are the belts and/or pulleys on the motor shaft loose?

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They don’t feel loose. Good tension on all belts. Also, the position reading for the bottom left:

-825.00 and -765.00

XXL, I assume? double check the set screws on the pulleys and make sure theyre on the flat spot of the shaft.

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Yes, it is the XXL.

Do you recommend that I tighten them further? They already feel tighten. I did manage to take pictures of the pulleys and set screws. All but the X-axis motor since it’s sitting behind a plate. Do you have any recommendations on how to check it without taking it apart? The X and the Z carriages came pre-assembled so I’m not exactly sure how to take it apart.

Btw, thanks for the help!

Y-Axis Motor 1

Y-Axis Motor 2

Z-Axis Motor

Your belt isn’t skipping your machine is crashing into the gantries.

Can you screen shot your settings.

When you turn it on, do you home the machine? Then when homes do you set position on all axis to 0?

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Since this is an XXL shouldn’t the table settings be 850/850 instead of 840/840 as per your video. Dunno if you originally changed these to see if that had any effect.

One some machines, when first set up, 850 will result in a crash — wish that we were suggesting some more conservative number there — I actually modified my homing switch placement using washers so as to ensure that I wasn’t hitting the belt anchors or otherwise reducing travel and it still happened.

My suggestion would be to initially only go to the half-way point, measure that location, adjust the value so as to get it perfectly centered, then see if one can go more-or-less edge-to-edge.

Arguably, we should start w/ a distance guaranteed to fall short, then calibrate for belt stretch, and only then enter actual table dimensions


I aggree. Thats what it looks like to me.
I think its going to one corner, crashing, losing steps, then because it doesn’t know it’s losing steps, it crashes back in the opposite corner exactly the same way.
850 mm was too big for mine too, but Im not sure what it’s at now., I just lowered it to about 1/4" away from hitting.

If I could like this twice, I would. Took me a while to figure out that in addition to the grbl settings the carbide motion settings need to be potentially adjusted as well.

I’m an idiot :smile:

So you guys are right that it’s crashing rather than skipping. I checked once again this morning and it’s a clearance issue. The X-axis drag drain didn’t give proper clearance for the X-Z Carriage thus causing this resistance.

Anyway, thanks you guys for the swift response! This community is awesome.

Also, I have it setup to 840x840 because it would crash at 850. This thread was the reason why I switched: Shapeoko belt slips when doing rapid positioning to the far left


Now lookee here, bud… There ain’t enough room in this forum for TWO idiots… you’ll have to leave - I’m already feeling claustrophobic.