How square is square enough

[hubrigant]

I'm to the point in my RMv2 build where the version 2 instructions are telling me to tighten the towers.

My framing square is old, something I inherited from my grandfather, so I did a quick check to see how square it is. I used the square to draw a right triangle, figuring I could measure the lengths of the sides and compare the length of the hypotenuse to the "ideal" length calculated via Pythagorean theorem.

As measured, length of a=10.5", b=9.875", and c=14.4375". The square root of a^2 + b^2 = 14.4140773205".

Now, I'm not a mathematician or an engineer by trade, nor am I someone who builds stuff much yet, so it's certainly possible that there are measurement and/or math errors involved. If not, does being off by 0.03" close enough, or should I be looking for a more accurate square to use?

[hubrigant]

Doing more work, it's looking like the square is actually 91.9 degrees. Looks like I'm off to the hardware store

[Captain Starfish]

FWIW easiest way to check a square is to put it against a flat edge and draw a line along the perpendicular, flip it over and repeat. The angle you just drew is twice the error of 90º.

[jdurand]

If it's a machinist square, you can probably tap it back into alignment. Check, check the other way. Tap. Repeat.

[hubrigant]

My old square is a framing square, stamped out of sheet metal. It was too far off, so I bought a new one and used that.

I've got the towers tightened now, but I'm not sure. The Onyx itself doesn't seem to be completely flat, it looks to be higher in the center than at the edges. Not much, perhaps 1/32". Did I do something wrong when I was installing the bed? Is that margin of error within acceptable tolerances?

[jram]

Good question, I'm at the same spot in my build on a Max v2 and the edges are lower than the middle, even with a precision straight edge across the bed. I posted the question in troubleshooting and haven't seen a reply as of yet. I'm wondering if the glass bed helps with the issue once it's on..?

[add1ct3dd]

I didn't bother too much with ensuring it's square, if it's off 1 degree you can compensate that anyway when you calibrate it :]

[bdjohns1]

I didn't bother too much with ensuring it's square, if it's off 1 degree you can compensate that anyway when you calibrate it :]

Trust me - it's much easier to build it square than to try and calibrate out the non-squareness. I believe Repetier-Firmware can handle rotation of a tower, but it might not be able to handle a tower that's tilted in/out with respect to the center.

[Nylocke]

Build your machine right. You can't correct for towers leaning in or out from what I know. It changes the radius as you go higher up, pretty sure the firmware assumes the towers are perpendicular to the bed.