Just finished up my latest sword, and I have to say, the combination of conductive probing + auto-leveler makes a big difference to the ease of engraving / repeat-ability of cut.
A little background - I've been working on building replicas of the Bride's sword (from Kill Bill) for a couple of years now. I think I'm up to number 6 at this point. Each time, I try to do a better, more controlled, more exact job.
On my latest, I knew I wanted to have my CNC in tip-top condition, so I:
1. Upgraded to the aluminium gantry.
2. Upgraded the spindle
3. Chose better bits (pyramid vs sign-making bits). Still using .6 mm bits for the leaf, though.
4. Bolted the CNC down
5. Added automatic CNC spindle control
6. Moved all the controllers/electronics to a nice, enclosed container (directly below the CNC)
7. Make better clamps for both sword blades and scabbards.\
8. Make a MDF table for the CNC with T-Nut hold downs.
9. Make my CNC probe routine more stable - use conductive vs mechanical, and make sure there is a pull-up resister on my probe input.
10. And then started experimentins with aluminum tape + autoLeveller
Anyhow, my current workflow for engraving now looks like this:
1. Do the design
2. Run the gcode through auto-leveler, which I modded to be able to subtract a "tape thickness" from each z move. I think my masking tape + aluminum tape combo came in at .2 mm, but I'd have to check to verify that.
3. Take that generated gcode over to my LinuxCNC machine
4. Clamp down what I'm working on
5. Apply a layer of blue masking tape to the surface I'm working with - squeegee it down nicely.
6. Apply a layer of aluminum duct tape (the really sticky kind) over the masking tape. Squeegee that.
7. Attach an alligator clip to the aluminum tape, and another to the spindle.
8. Plug the alligator clip leads into the CNC probe input port.
9. Touch off on x,y and z axis (using the probe to set the Z)
10. Run the probing job. When that pauses, remove the clips and the tape. Then click the "pause" button to un-pause the job.
11. Watch the magic happen.
Here's a couple of pics of my latest engravings. They are the most clean I have ever produced, and I'm very happy with the quality and repeat-ability.