My z plane isn't perfectly level

[rdlohr]

If have a 14" x 14" cutting area and the Z plane not perfectly level .  Its off by .04" worst case measured in the corners.  This matters when cutting slots in Lexan that go most of the way through the Lexan.  This extra 4/100" error sometimes allows too little material left under my slots.  I'm considering shimming under my table mounts, but I wondered if Mach 3 allows me to program in this offset.  I can't be the first person to have this problem.

Thanks
Rick

[RICH]

Rick,
Can you post a pic of the machine?
I think fixing the machine would be better than a programing solution.
RICH

[rdlohr]

Thanks.  It's a K2CNC machine.
http://www.k2cnc.com/shop/proddetail.asp?prod=KT%2D1414%2D09&cat=26

I would have to remove the table top and put shims under it of various thicknesses at about 12 screw locations.  While this is doable and not a big deal, it would be easier to pull up a screen that let me put in an offset for each of four corners.  Actually, you would only need three assuming the fourth point would be at zero referenced to the other three.

Rick

[RICH]

Rick,
Fix the the bed and eliminate the problem or just mount a piece of your choice and machine / face the mounted piece.

RICH
 

[ger21]

Typically you bolt a sacrificial bed in place, and machine it flat. That's what most router owners do.

[rdlohr]

Thanks for the input.  I had considered that.  In my case, I'm milling Lexan and to produce a clean edge underneath, I have a 1/4" air gap under the Lexan I am machining.  I had some melting problems when I had a sacrificial Lexan sheet underneath initially.  I have a fixture that is held on all the edges that has a 14" X 14" cutout for the area that I do my cutting in.  I guess I could do a different hold down scheme utilizing a sacrificial board underneath that has been milled.

I guess Mach 3 doesn't have an easy way to do this.

[BluePinnacle]

a little late perhaps, but how about a metal plate table? it would tend to sink heat out of the plastic. Also, do you have any cooling arrangements in place? Compressed air jets to the tool may help, or water vapour, depending on your electrical arrangements and sealing.

[rdlohr]

All cooling is done by a vacuum.  Actually, when I had the heat problem I think it was prior to having a vacuum in place.

To solve my problem, I shimmed the table top underneath and now it is accurate to about .005 so it works great.  Thanks for the inputs.

Rick