Got a Math Problem for Those Who are Trying for Tight Tolerances.......

[cnsranch]

Been working on some corbels for a customer - their thickness has to be correct in order to fit into slots in his cabinet.....

He gave me the one good one he has, and I scanned it, etc. Carved 3 or 4 tests to see where I am, and this is what I've got......

I've solved my alignment problem with my two sided carve on the corbels, but I've got a small thickness problem - maybe the bottom line is that I'm expecting too much from my machine.

If you look at the mpc below, you'll see that I have the depth of the carve at its thickest at .002. I want the finished thickness to be .375 (3/8")

Now, the board thickness is set to .383 in Designer. If you take that and subtract the .002 from each side, you should get 3.77 - pretty darned close.

I used my drum sander and a digital gauge and started with right at .383 for the real board. Finished carve actually took about .03 from each side, not .002. So, I ended up with a thickness of .320, not .375.

I can start with a thicker real board, say, .430. If I do, and all other things are equal, I should get a finished thickness of .430 - .06 = .370......still close enough.

I'm using a sled.

What do you think - again, am I expecting too much??

[fwharris]

Jerry,

I just replied to your PM but will post here also.

I was having the same issue with trying to do stl slices and when put together they needed to be the same size as the stl dimensions. Even though in designer it showed the height being at 0.0 on the board it would still carve off the top making the final to thin. I had to go to a thicker board.

The only other way to get around this would be to use a shim on top of the board when the machine is doing the finding surface step.