Square Enough?...

[robinsoncr@naxs.net]

I have checked and adjusted sqaure for the x-y axis. I used a metal dowel rod centering tool, plunged it into the spoil board at 0,0; 0,53; 113,0 and 113,53.

I then measured diagonally from from point to point and found that the diagonal opposite to 0,0 was 4mm greater.

I snapped a line connecting the two dots 0,0 - 0,53 and then 113,53. Then I did the ole 3,4,5 square check. It was off about .03"

I tried adjusting the y-car in an attempt to improve this without luck. If I'm looking at this right, that says the machine is out of square 0.03" over 12 feet. Am I trying to achieve a result that exceeds the machines resolution?

Chris

[billp]

Chris,
I think I'd be thrilled to have a large machine that square! My questions would be, what are your plans for using the machine,will you really be cutting 12 feet in a single file, and can YOU live with those tolerances...? Bill P.

[gerald_d]

The 0.03" is plenty good enough for our work, but the 4mm is not. Doesn't sound like the same bot giving different results. My immediate reaction is that you are having measuring problems, and that you need to sort your measuring system out first, before you really know where you are on the squareness issue.

[rgbrown@itexas.net]

One of my methods of "checking square" is to put a 1/4" bit in the machine, screw a piece of plywood oe other sheet material on the machine and bore holes in three locations, at -say 0,0; 0,24; and 12,24. I then flip the board in the "X" direction, locate the board with bolts or dowel and move the machine to the 12,24 location and the "Z" to the surface. The "Hole Offset" to the bit will be twice what the machine is "off-square".

I don't get to play with the "Pythagorean Theorem", although I hear they are a fine band, and, I don't need to measure diagonals but, when the holes "match", all is right with the ShopBot.

[Robinsoncr@naxs.net]

Bill, I will be cutting cab parts out of 4x8 sheets of plywood and melamine. So, if the error is linear, all is fine.

Gerald, I did the 3,4,5 to test the original measurement that was diagonal vs. diagonal. I used a 1/4" bit to trim the edge off a 4x8 sheet of melamine and then measured the diagonals on that. It was out 1.5mm. In other words, one diagonal measured 1.5mm longer than the opposite. I think we are probably going to get this thing as square as I can considering the structural limiatations of the machine.

Ron, I'll try your method this week to see what it tells me.

Thanks,

Chris