Depth of cut and setup of home position

Im doing a carve on 5.5mm plywood with a 1.0mm bit. Ive got the depth of pass set between 0.5-0.7mm. sometimes I set the home position and its perfect and other times it barely skims the surface of the wood, I intend to use double sided tape to prevent bowing of the material. Has anyone got any tip for fine setup or are people just using the sliding the paper under the bit technic.

The only problems I can think of are uneven material from the factory, bowing, and I’m not setting the home correctly.

Any input would be appreciated cheers guys / gals!!!

Your wasteboard may not be perfectly level. I know that mine has a .030" dip in the middle of the X direction on the front half. If you’re using a small piece of plywood, you could always make a secondary wasteboard and just cut a small pocket in it for your material to sit in. That way you know it’s level X and Y, at least until seasonal humidity changes cause it to start changing slightly. Then you do another quick run to level it out.

As for setting home, I use a little homemade touchplate to set my Z:

To use it, I attach the alligator clip to the bit. I know the material in the corner is .065" tall, so when the LED is solid I go up .035", then down .100" to my Z0.

If you have uneven material sitting on work surface, non of this methods will work for proper Z zero. If you’re carving sign or similar, you can press the bit a little further after touch the paper. But if surface is important and needs to be precise, you have to flatten the surface with flat bit before starting to carve. One simple pocket operation needed. That’s what I do. I start with 0 depth, (it will touch the surface anyway) give a little more depth if still there is untouched spots until all surface clean. Hope this clears your question.