That’s hard. But in your drawing, you show a square that is rotated. Are you sure it isn’t a parallelogram?

As far as I studied the docs and much available info, no.

I would not touch these. I would in no case see this as a way to solve your problem. The set screws are for ensuring the vertical alignment of the Rails one over the another. Also the possible amount of movement would probably not be high enough.

The topic that Derek posted a link to is what has been discussed recently.

The question whether the optional QCW Frame may help ensure X/Y-squareness is still open.

Please check Y too. You want to be sure that the assumption of the machine being out of square is right.

E. g. your workpiece, has it a right angle (or could you mill a workpiece which has one, a 90° corner), and then could you hold a joiner’s square to it? Is it square or parallelogram then?

One possibility would be to measure the distance of the outer corners of the feet, like this (imagine these little raspis were the machine’s feet):

1.5mm over 3" (seriously, did you just mix mm & inches in the same reference? ) is about 15mm over the entire travel, which is huge. It sounds to me like your machine is not homing correctly. A slight error can be had just from machine assembly, but it normally wouldn’t be that severe. The only way to correct this sort of error is to be able to measure squareness of travel. This can be as intricate as using a dial indicator, or as crude as using a long straight-edge & carpenter’s square, eyeballing the edge of a cutter across the X travel. Either way, it requires a direct measurement of X perpendicularity to Y. If your homing is incorrect, I would advise using identical length hard stops off the front Y blocks instead of relying on the bearings as bump-stops to ensure squareness.

This was an image I shared on another thread, but it shows the concept of how to measure it.

one simple way to verify X/Y-squareness of the machine is taking a workpiece nearly as big as the workarea, fixing it at marked points to ensure repeatability, then program four holes that form an exact square to be milled in the outer corners of the workpiece, milling them, and then rotating the workpiece by 90° and repeat the program. Et voilà.

It simpler than the tiled cut example which also shows if the machine has un-squareness.

I’m still having a hard time picturing why measuring outer corners of the feet is better than say, mounting an indicator and sweeping a vise or fixture plate. Is there something I’m missing or is this a different measurement than squareness?

I’m ~80% sure this is out of square, though it could also still be a parallelogram. Here’s one example piece I tested yesterday where the tilt is most obvious visually. I did cut a square test pocket and visually it has a similar tilt to it. The pocket is roughly equal on the diagonals and flats according to my quick check with some calipers.

Are you talking about X/Y squareness or X/Z squareness?

Anyway if you want an angle to be 90° (=if you want your machine to be X/Y-squared), then you measure X and you measure Y and then, with knowing the angle you want (90°), you compute the diagonal that has to be there. Then you check by measuring the diagonal.

Remember that if one diagonal is shorter than the computed value, the other will necessarily be longer. So to ensure a 90° angle, it will be enough to shift one axes’ ends until the diagonals are identical.

One simple way to ensure squareness of X to Y on the machine is ensure by measuring that both diagonals are identical. It’s as simple than that.

At first sight, this looks as if the letters are rotated in comparison to the rectangle.
If we have rotation here, then it is not a X/Y out of square issue.

Do I understand it right, you milled the letters, or the shape of the rectangle or both or what?

Here’s what I used on mine. Works great! At 20mm long, they are just about 1mm longer than the .750" bearing stick-out (look at me, mixing mm & inch in the same reference. )

if your machine is a parallelogram, i.e. if the angle between X and Y is no right angle, then the X axis will have a tendency to square itself during movement over the Y axes. But if Y steppers are stall homed and the machine has X and Y not in right angle, one of the Y gantry blocks will reach home before the other (remember, even if buildbotics controller is prepared for driving the two Y steppers with one single driver, on Onefinity CNC each Y stepper has its own driver and control). The question is, if one Y stepper reaches stall homing, will the controller stop the other Y stepper then or will it stall home independently, after the other? If yes, then Y stall homing will “twist” the X Axe then in order to reach stall home on both Y steppers.

In every case the first thing I would look at, is if your machine really has right angle between X and Y.

On side not, to me it looks like your stock was just not in squarely or your reference line was off. Doesn’t mean you don’t have a square ness issue. I recommend putting down a large test piece. Trace the boundary, carving a fine line, then put a large square to it.

Ah, okay. I’m assuming the machine itself is square and the relation between the machine and the work is “out of square.” I’m also a n00b with this, so take whatever I say with a grain of salt.

The letters are not rotated, the entire toolpath is rotated. This is a pre-cut plaque and then I did the engraving for the letters.

The stock is in a vise on a fixture plate which also has the machine bolted on it, so the machine and the fixture plate are “out of square” I think. This is the same as the stock not being square to the machine.