Squaring process sanity check...

[geneb]

I'm getting back to using my 2006 PRT Alpha 96 after leaving it idle for a number of years. I wanted to check and make sure that I had it square - for various reasons it was possible that it wasn't when I originally set it up.

I used some scrap material to set four 6mm pins at 2",2", 2",46", 94",46" and 2",94" (basically the four corners of the machine)

I'm using a 3D printed tool in order to do the measurement - one end holds the dumb end of the tape and the other part provides a straight line to check against, so I'm not measuring diagonally from center of pin to center of pin. (AFAIK, it doesn't matter what the measurements are, as long as they're consistent and eventually converge, right?)

I measure 2577mm going from left to right (as you're facing the machine and looking down the X axis), and 2574mm from right to left.

It's my understanding that if I were to move the stop block on the left side (longest dimension end point) about 1.5mm, (half the difference between the diagonals) this should result in a square X gantry (or at least start approaching that point).

My current start-up procedure involves powering the control box, then pulling the X gantry to the right stop block - the left side hits about 1/4" (ish - I've never measured it) before contacting the stop block on the right. I then hit Reset in order to energize the steppers.

Assuming the process I outlined above works, I can address the stop block position mismatch at a later date - moving the left stop block will of course increase the distance I've got to force the right side until it hits the block, but it shouldn't be much.

Thanks folks!

g.

[ken_rychlik]

Your thinking is mostly correct. As long as the long rails are parallel, the part about how far a stop is from the end doesn't matter. If you have to pull to hard to get it there, loosen the corner bolts on the y gantry, pull it to the stops, and tighten.

[geneb]

I'm not that concerned about how far the stop block is from the end - I was referring to using it as a way to square the gantry when the opposite end is pulled against its stop block.

tnx.

g.

[geneb]

Are the corner bolts you're referring to the ones outlined in red on this image? https://i.imgur.com/8WBQTuT.png

Thanks!

g.

[ken_rychlik]

Yes, but if it's out a lot, you may need to shim things on that one with the aluminum cross bars. I would try loosen move and tighten first.

[geneb]

Awesome, thank you.

I've been able to adjust it via stop-block tweak so that it's only 0.5mm out of square. Left to right is 2574 and right to left is 2574.5. I suspect breaking out the dial indicator in order to move a stop block 0.25mm is a bit much for a machine that eats wood.

g.