I am trying to carve and engrave 3D shapes and lettering on thin acrylic sheets. For applications like this, or cutting traces on copper clad PCB material, getting the machine to be level with the surface of the material is crucial. I am finding up to 0.5mm variation across the 6x8" cutting area.
Do any of you have tricks for ensuring that when you set Z to the top of the material in one place, it will be within 0.1mm of that value at another place?

One approach with metal or wood is just to face the material, but I need to preserve the transparency of acrylic on both sides, in uncut regions.

I know the 3D printer folks go on and on about bed leveling, but a search of this forum for "leveling" turned up nothing.
Is there no one else there doing work that requires precision in Z?

Thanks,
Steve

Why not put down a 1/2" thick piece of scrap mood, and level that with a surfacing bit? Then place your work piece on top, and if it is uniform in thickness, the job is done.

That scrap mood is actually scrap wood.

Thanks, Wazza. That is sort of what I did, which is to carve a 6x8" pocket into my spoil board table and put a piece of acrylic into that. But to cut multiple pieces or a bigger work that requires indexing of tiles, I can't figure out a way to keep it all co-planar and leveled.

Steve,

If you're seeing a Z height discrepancy in the X direction--there's a bit of easy adjustment built into the X/Z carriage. The six large bolts that hold the carriage against the mid-wall of the handibot frame can be loosened to allow for the X to be set more parallel to the cutting surface. I'd recommend driving the bit down close to the material--then moving it from side to side while making tweaks to the alignment until you've got it level.
You'll also want to make sure that there is no debris under the tool that might be lifting it up in any direction.

Brian

Thanks, Brian, that is very helpful. Now, is there such an adjustment I can make for a non-level travel in the Y direction?