New XXL Z axis belt slips (tension bolt needed?)

Hey guys,

I just assembled my first XXL and did a test run.

I noticed that when my shapeoko gets close to cutting the sacrifice sheet (3/4" MDF) it’s prone to slipping vertically.
When I say “slip” the belt slips. I think the shapeoko’s z plate is stretching the springs too far? So basically my theory is that the springs and combination of the spindle plunging into the material allows just enough slack or rebound in the belt allowing the springs to pull the z plate vertically up a few clicks. Is this a common problem?

Will just adding more tension to the belt fix this problem? and what is the bolt size I need to push the tensioner down for the new xxl ? A M5 doesn’t fit and we don’t get the tension bolt as part of the shipped package.


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I had to use a pry bar as notedin a forum post linked here:

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So if any one was wondering. a M4 x 20 fits perfectly :stuck_out_tongue:
(if your like me and didn’t want to estimate how much force i would put on the pry bar. )

now i’m cutting 1.5" mahogany perfectly. :smiley:

Remember to recalibrate your z travel after you adjust the belt tension so your z depth of cut is accurate.

I’m late to the party on this one, but it looks like you figured it out. It is indeed a standard M4 thread.

WARNING: If you over-tension the z-axis belt, with the mechanical force of the screw, you can pretty easily bend the stepper motor shaft, so don’t go crazy on it :slight_smile: