Concrete table?

[SaintJohnBosco@yahoo.com]

I've been testing out my ShopBot and moving at 2 inches a second air cutting and after about 300-400 lines I can be out of alignment by as much as 1/16 of an inch. With my cable drive it was between an 1/8 and a 1/4. I noticed my machine does a lot of shaking when moving at these speeds. Is it possible that this has been my biggest trouble with accuracy? I had planned on going steel because of insects, but b/c of costs I just stuck with my wooden table. I was contemplating building two concrete block walls to replace my current legs. Then I could fill the cavities with concrete & rebar and then bolt the table to the walls. I know this sounds crazy, so I thought I'd ask. My files have very short lines and a lot of them. I've reduce their numbers as much as possible, so now after looking at other posts on this forum I've got to wonder if its not my ShopBot but the vibrations and gyrations of my table throwing things out. Has anyone out there in ShopBot land atempted such a crazy and daring thing as Concrete? Now that I've ask I can get some sleep. Oh, by the way I tightened up my thrust boxes so that the pinnion gear is closer to the rack and my power went up 5 lbs. Still it is only at 45 now instead of 60. Is that resistor capable of reducing that much power? Good night!

[SaintJohnBosco@yahoo.com]

Ok I built those block wall legs. Now I have almost no vibration. I found a wire that I had not installed properly. Now my ShopBot is acurate to .02 doing 2 inches/second air cuts.
I know I can't expect to cut this fast, but when I engrave I only put my bit in .02" into the wood so I thought I should be able to get a little bit closer to the accuracy specs. Should I expect to be able to able to get the .002 inch acuracy?????? I do have switches set up and some software so that the machine rezeros itself every 20 lines of code. So at least I don't have to worry about accumulating errors.