Shapeoko 3 - How I squared it

Just like a few others I had a ”gap problem” between the front plate and the left X-axis plate when pushed all the way to the front. I could get the base squared by measuring the distance between the Y-rails and then measure the diagonal distance. It was spot on. But the gap was still there.

At first I was pretty confident that I could fix it real quick by following the official guide and reading here on the forum. But after 10+ tries my confidence was a bit damaged. :sweat_smile:

So, I figured that I would try to find the source of the problem and disassembled everything. The X-axis plates came pre assembled and I saw that you could buy maintenance parts in the store so I stripped both plates.

I hope this can help someone else.

The front plate and the back plate had a tiny twist. When they lay down on a flat surface you could feel / hear it when pressed on the sides. That was fixed by hand, carefully twisting it in the opposite direction.

The front plate and the back plate had a small bend in the middle. When they lay down on a flat surface and the front is facing down (imagine the extrusions standing up) you could see some light slipping through in the middle. Same thing when they stood up (as they would with the waste board attached). All the screws for the waste board went in fingertip easy except the ones in the middle. They did go in easy, just not fingertip easy, so I can’t imagine that this need to be fixed.

The X-axis plates also had a small bend from top to bottom. The left one inwards and the right one outwards. I don’t think this need to be fixed since it’s 0.5mm across and it’s from the top to bottom. It can be corrected by leveling the extrusion.

The sides on the X-axis extrusion was not square. When it was mounted to the plates I had a 2mm diff across the whole length (measured from the left plate) and a 4mm diff across the whole length (measured from the right plate). I temporary shimmed it with folded foil so I could keep on but I will take it to a machinist to fix it for good. Now the diff is about 0.2mm on the left and 0.3 on the right (across the whole length).

After I shimmed the X-axis I did another assembly test (checked that the base was square first) just to see if there would be any difference. The gap was now on the right side. Meh…

The sides on the Y-axis extrusions (both) was not square. Right now I don’t care about the top and the bottom. Both diff a little bit but I correct that when I mounted them to the front/back plates.

The left extrusion had a 4mm diff across the whole length measuring from the inside/front and a -3mm diff across the whole length measuring from the inside/back. The outside had a -3mm diff across the whole length from the front and a 4mm diff across the whole length from the back.

The right extrusion had a 3mm diff across the whole length measuring from the inside/front and a -2mm diff across the whole length measuring from the inside/back. The outside had a -3mm diff across the whole length from the front and a 4mm diff across the whole length from the back.

The left extrusion length at the inside/top (where the V is) and the right extrusion length at the inside/top (where the V is) was pretty much identical.

After I shimmed (again with folded foil) both the extrusions (with the waste board on but not secured) I had to square the base with a little help from a strap that I secured diagonally.

When the base was squared I added the corrected X-axis extrusion (only the top wheels mounted to the plates) and checked for a gap. The gap is now 0.002mm at the front left side and 0.04mm at the back right side. It might be less after a machinist squares the extrusions but I think the numbers are just fine.

After this I mounted the motors and the bottom wheels and slowly tightened them until they where snug.

Now it’s time for the Z plate and then tramming I guess.


I just added additional washers between the plates and wheels in the corner where they were required. I took my digital caliper to the hardware store and measured washers to find a variety of thicknesses to give me some play.

But you’re right, the variance in the plates is the source of many a user’s squaring issue.

Perhaps someone (paging Mr. Beaver?) should devise a set of two wheels (top/bottom) with a threaded adjustment to help square the gantry.

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Dang, now I’m going to have to spend even more time getting my XXL up and running. Can’t stuff like that be part of receiving QC ant Carbide3D?

Flat is expensive, real expensive. All these things we seem to want would put any SO4 out of the cost range of the typical buyer.

Just shim it. Shimming is cheap and doesn’t take but ten minutes.


Thank you for going through the rebuild process: disassembly/analysis/modify/rebuild.
Maybe, a guide to shimming the Shapeoko is in our future?
I hope you don’t mind me suggesting that you christen your Shapeoko “The Shimpoko” after all that work.

I agree. For the price I really don’t mind spending the extra time. If all this would be included in QC we would have to pay a lot more.

Personally I see shimming as a temporary thing in order to track down errors but with the right material (not foil) I believe it can stay in shape for some time.

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I guide would be real nice actually. It seems that the most common error is the sides of the extrusions.

Haha, I like that name. “The Shimpoko” its is! :joy:

The problem with shimming the ends of extrusion is one of resolution.

Let me explain.

You have these plates on each side of the gantry. The plates extend several inches from either side of the extrusion. Due to this arrangement, variances (in square) at the ends of the extrusions will be multiplied by the plates.

Add the fact that the plates themselves are not perfectly flat, and what you’ll find is that you can waste a lot of time screwing around with shimming between the extrusions and that plates, to get the machine square.

Trust me, don’t bother with that. Instead, pick the pair of wheels (top/bottom in the front or back of one side of the extrusion) that if shimmed, will square the gantry. This is pretty easy to determine by looking at the direction of skew. Loosen the screws for the top/bottom wheel you think needs shimming and measure the gantry to the left or right y-axis extrusion to see if things are now square.

Now just determine how much extra washer thickness you need between that set of wheels, and the plate. Well-stocked hardware stores sell stainless and zinc-plated and plastic and fiber washers in all sorts of sizes and they’re all slightly different thicknesses. In my case I was able to find two thinner stainless washers that made my machine perfectly square. And it didn’t take but a few minutes.

Feel free to post back if you have any Q’s.


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