Trouble Squaring Pro XXL

I received my new Pro XXL and am having a tough time squaring up the machine. Have double checked that the hardware needing to be loose is loose. I get the start fine with the gantry touching the front end plates perfectly, and I tighten down the front shoulder bolts it is fine. As soon as I move onto the next shoulder bolts there is a decent gap almost immediately (front right end plate). Have been trying the process over and over but no luck. I have looked at some of the other information here and on other videos with washers, foil, shims you name it, but not real adept on those “fixes”. Is this something that is common with the new machine? Pretty frustrating, but I also understand these things do happen. Just need some guidance to some other methods to get this squared up properly without the addition of other hardware/items. Thanks !

I had the issue that a wire got caught between the backplate when assembling my XL. If I recall correctly it was the wire for the right rear limit switch near the controller. It came right into square once I got that unpinched. (Though it kept trying to jump back into the gap :grinning: )


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I had some aluminum chips stuck between where the end plates and the gantry - came from the factory that way. It was enough to throw it off square. Once I figured that out, I cleaned it up and it’s been square ever since.

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Ugh! I can imagine that could be the issue. We were trying to keep an eye out for any shavings we might come across, but maybe we missed something. Was planning on having this machine done this weekend, but looks like we will be dissassembling instead of assembling, to see if this could be the issue. Thanks for the information!!

Luckily that is not the issue…whew!

The Pro is entire machined on all aligning surfaces, so should go together quite squarely.

Usually what works is to have all the hardware loose, and then go around tightening non-adjacent hardware (as one would when changing a tire) until the structure of the machine begins to move, the switch to a different bolt — periodically measure the diagonals and ensure that they are equal, and if not, gently nudge the machine to bring things into square — repeat this until all bolts are sufficiently tight.

If that doesn’t address this, please send photos showing this gap in to and let us know what you’ve tried and we will do our best to get this sorted out w/ you.


Thanks Will, I will try again and see what the results are. I thought I had tried every combination of tightening that I could think of. I have the Shoulder bolts loose, drag chain supports loose and the Gantry end plates loose. When I bring the Gantry forward it is tight against each of the end plates. I tightened the most forward left and right shoulder bolts and it was still fine. I slid the Gantry back beyond the next shoulder bolts and when I tighten them down, the gap on the right forward end plate becomes evident.
I also tried when all shoulder bolts were loose, to hold the gantry against the end plates while tightening the most forward shoulder bolts. But again, as soon as I slide the gantry back and attempt to tighten the second set, that gap on the forward right plate appears…
Note: I would tightne one shoulder bolt (i.e. forward right, then left) same for the rest (next right shoulder bolt, then left)

If tightening hardware begins to pull things out of square, back off and switch to something else — it should only be an issue if you reach a situation where attempting to tighten any of the remaining loose hardware begins to pull things out of square.

When I put mine together I loosened the cross bracing on the bed. Only had to do the two middle braces. It was a pain in the backside.

Got it squared and have had no issues since.

Good Luck

Just to confirm: So I am at step 4.6 Square machine. I was following those instructions

If you continue to have difficulties, please write in to

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I have the EXACT SAME struggle with my new Pro XL! It is about a millimeter, maybe just shy. It all lines up, yet when you tighten it up, it is off slightly again. Like the belt itself is pushing that side back slightly. After trying a few times, I am running with it, finishing the build & will make a judgment then whether or not I can detect this slight offset over such a long span (since it is a long span, it may be very minimal). Still, I am going to read the responses you have gotten & follow this thread closely for the solution, as square will be better than this slight gap, any day of the week. Glad you posted this, thank you, I had been planning to make a thread, yet, I was having a bit of trouble wording it, you nailed it.

I tried alternating left-front, right-middle, left-back, then the same in reverse. I also tried doing just one side as the video of Winston Moy building the XXL showed, no dice there, either. I then went front-to-back, both screws - it always results in that slight gap in the front-right plate showing up & no longer touches while the front-left plate is touching with no problem. Still reading up on the thread.

Just a thought here…if you are moving the gantry on one side or the other that could cause a slight gap on the other side. Moving from the center will lessen the chance of a gap.


I corrected the issue by slightly tightening the belt on the side that has the gap. When installing the belts it is not really possible to count the teeth accurately to ensure that there are an equal number on each side. Adjusting the belt tension is an easy correction.