Squaring the Desktop bed?

[Chelmite]

Hi, I have a ShopBot Desktop. I'm trying to come up with coordinates for making various jigs that fit the extruded bed. The slots are 1.5" apart, but they're not parallel to the X axis of the gantry. It seems off by as much as 1/8" (I can get more accurate measurements if anyone want.), which means a 1/4 bit traveling straight down a slot would run into the aluminum (yeah, bad idea). Is there a way to align the extruded tracks so they line up with the X axis and I don't have to go through complicated formulas to figure out where my jigs' or works' mounting holes will go?

Thanks

[bob_dodd]

Steve

I never checked mine as I use a spoil board ( it uses wedges and fences ) on top of the extrusions , and then surfaced it to be flat and adjust it to be square to 0,0 . The cut files and pictures are on the thumb drive that came with the DT .
You can loosen the machine screws that hold the extrusions down and maybe adjust them , I would also check that the extrusions are at the same height across entire surface Hope this helps

[Brady Watson]

If you plan on cutting all the way through, a spoilboard is pretty much the way to go. You don't have to run a large one like came with the tool, but you should have some kind of 'pad' underneath to prevent you from running your bit into the aluminum...because that's bad news. The 'ShopBot paradigm' is that you use a spoilboard that you routinely clean up/flatten as you 'spoil' it with your cutter. If you are a new CNC user, you are going to 100% ruin your spoilboard in short order. This is normal. I'd rethink using the AL as your Z0 point.

In regards to locating your jigs, you can do this in a number of ways. I will often use a v-bit to catch the edge of the spoilboard like an indicator, and move the spoilboard until it is aligned. I also use a 1/4" metal rod, where I move the spoilboard .125" in the negative for X or Y, and then pull the board to it, then I check it.

You can also drill 'witness marks' on your fixture using your bit at specific locations (say like 1,1 and 8,1) & then command the tool to those locations and bring the Z down. Then align the material to the machine OR align the machine to the material, using the VA command. There are lots and lots of ways.

Bob's setup is a good solution - you should take a closer look. He's been at this stuff longer than me :) Sup Bob?

-B

[Chelmite]

Hi Bob, your spoil board looks very useful.
What kind of fences & wedges do you use?

Thanks,
Chelmite

[bob_dodd]

Steve

The spoil board is 3/4" MDF , the wedges and fence are 1/2" MDO plywood ,you could use 3/4" also . The spoilboard and wedges was designed by Bill Young and the cut files are on the thumb drive you got from Shopbot, There are many versions of this system posted on this forum, I made mine wider to help keep the Y rails/slides cleaner . Scott Plaisted has designed one with inserts as to a more solid fence system , There are a few more

[scottp55]

Steve, Got a lot of info and help when I asked almost the same question a while ago. Thread here.
http://www.talkshopbot.com/forum/showthread.php?t=19057&highlight=desktop+jigging