Isolation routing copper plated pcb -> loosing z-steps. With wood no problem

with wood my MPCNC works fine. Now I wanted to mill a custom pcb plate.

After some time the graver goes deeper and deeper into the pcb.
I can’t say for sure that Z-axis is “loosing steps” because it’s just graving (0,1mm deep), so there should be no z-movement.

Graving on wood is fine, as you see on the picture.
This is how it should look like:

Here you see that after some movement (graving goes from bottom to top) it’s getting deeper and deeper.

Same here.

What is wrong, what can I do?

  • Stepper current should be right, as I have no problems, also not with hard wood
  • copper plate is even, i checked z=0 on all edges

That looks to me like your surface is not level. Wood being think would not show it, but that pcb being thin does.

@cybtrash I was thinking the same thing. The PCB plate my be flat and even, but your spoil board and your router may not in the same plane, causing this type of issue. Though you did say:

So much to ponder for me now…hmmmmm :thinking: :thinking:

Guys I found the cause. I plugged the end mill power cable into a plug of another room (with an extension cord) and the problem is much, much less. I was able to carve the whole pcb. In the end it still lost some z-height but only about 0,15mm.

I mean the problem only appears with the copper plate. If I turn it around I can carve without problem on its back. Let’s think. Copper plate can conduct electric power. But it is not connected to anything.

Must be some kind of electric interference. I just don’t know how I can explain this. But my issue is reproducible.

1 Like