Checking for square

[charles48]

I recently checked my shopbot for square by using the pythagorean theory. I used a 45 degree v-bit to put a dot at 0,0 I made it a sixteenth of an inch deep leaving a dimple w/ an obvious center. I jogged the bot to x33 & y33 and made another dimple. The distance between these should be 46.667" (46 21/32")by the pythagorean theory. I also figure that in 66"(the width of my rails) whatever error would double which is why chose 33 for a test. My Shopbot was very very close. If it was off say 1/4" I was thinking about clamping blocks on my rails tight against one side and the distance away I calculated on the other side. I would unhook my steppers from the control box then loosen my bolts on the x axis gantry and pull the side tight against the block, and retighten my bolts. Does any more experienced Shopbot users see anything negative about my corrective actions.

[Brady Watson]

Charles,
Sounds like you are headed in the right direction. There's a whole bunch of suggestions on squaring up the machine if you search the archives.

Be sure to turn off the control box and disconnect the steppers before moving them...motors can also be generators.

-Brady

[charles48]

Thanks to Alan for senting me this way of squaring the shopbot.

Like most ShopBot owners, I too took the approach of trying to square the
y-axis carriage using a formula (Pythagorean's). This does work, however it
is cumbersome and leaves room for error. I also took the approach of using
a large framing square, however this just isn't big enough, and I found now
matter how many times I 'squared' it up, it still wasn't square when I
tested it with the 'Bot. So I came up with a much easier and straight
forward approach.....

I start out with mounting a new spoilboard that is exactly parallel to the
X-axis. Use a couple of blocks of wood to space the spoilboard over an
equal distance from the x-rails.. (also make sure that the new sheet has 90
degree edges!).

Then with your motors engaged on the x-axis and disengaged on the y-axis,
set the 'right - hand' side of a straight router bit to just barely touch
the left edge (i.e.; x would equal -.125" ) of the spoilboard. Make sure
you do this first step with y somewhere in the y=1 or y=2 range. You are
just using this as reference point. Now roll your y-axis carriage to
something like y=46 or y=47 and NOW make your adjustments to your y-axis
carriage. Lightly snug things up. Now roll your y-axis carriage back to
y=2 and recheck that the leading edge of the bit is still just grazing the
edge of the spoilboard.