# How to mill copper laminate on CNC to make circuit board

#### BobTPH

Joined Jun 5, 2013
6,305
I do height mapping on my CNC3018 when milling copper laminate for making PCBs.
You just need to bridge the sense input to ground.

Since my spindle motor is mounted in a plastic bracket and insulated from ground, I connect a wire from the motor frame to the sense input. When the tip of the cutting tool touches a grounded copper laminate or a thin piece of grounded metal foil, zero height is sensed. This is only done during a mapping procedure or Z=0 probing where Z probing is done very slowly.
Did you get that to work? I tried for about 2 weeks, using all kinds of bits from cheapo to expensive ($35). I did the height map. I never got it this to work. The depth of cut (and hence the width) varied wildly as it went across the board. With the original spindle it would crash the software if the cut got anywhere deep. Tried snubbing network to no avail. Tried replacing spindle with a line powered Dremel with much higher RPM, and never got anything close to reasonable results. Moderator edit: New thread created from this. #### MrChips Joined Oct 2, 2009 28,137 Did you get that to work? I tried for about 2 weeks, using all kinds of bits from cheapo to expensive ($35). I did the height map.

I never got it this to work. The depth of cut (and hence the width) varied wildly as it went across the board. With the original spindle it would crash the software if the cut got anywhere deep. Tried snubbing network to no avail. Tried replacing spindle with a line powered Dremel with much higher RPM, and never got anything close to reasonable results.
Yes, it did work, both height mapping and engraving the copper laminate. You have to do some trial and error to get the proper results. You have to try different tools and depth of cut. I do not have the proper milling tool and just used what I had available. Also you do break a few bits so make sure that you have lots of spares.

#### BobTPH

Joined Jun 5, 2013
6,305
I did all of that, including breaking the bits. The problem I had was that, even with z-mapping, the depth of cut was never consistent.

#### MrChips

Joined Oct 2, 2009
28,137
I did all of that, including breaking the bits. The problem I had was that, even with z-mapping, the depth of cut was never consistent.
What were the dimensions of the laminate?
Was the board reasonably flat to begin with?
Was it firmly held down at four points?

#### BobTPH

Joined Jun 5, 2013
6,305
It was standard 1oz copper PCB blank. reasonable flat and I might have had only two hold downs, but it was secure, not rocking or anything. The board was 3 by 5 in but what I was trying to mill was maybe 1 by 2 in.

Whenever the spindle motor was strained it crash the host PC USB port. But it was not strained when cutting only through the copper layer, it was when it dug deeper that I had problems.

If I decreased the depth it would miss cutting through the copper in places. Very frustrating.

#### AlbertHall

Joined Jun 4, 2014
12,202

Joined Jul 18, 2013
26,686
I would have thought it hardly worth it considering the Very cheap costs of having boards made that come with the options of double-sided and through hole plating etc?

#### DNA Robotics

Joined Jun 13, 2014
637
I suggest milling the mounting surface flat then use double sided carpet tape.
If your machine isn’t sturdy enough to mill the mounting surface, use a dial indicator to adjust it flat like a 3-D printer platform.

#### MrChips

Joined Oct 2, 2009
28,137
@BobTPH Bob, I wonder if your height mapping is done correctly and is being applied during the milling?
That is the whole purpose of doing z-mapping, isn't it?
What CNC software are you using?
I am using Candle for PCB milling.

#### MrChips

Joined Oct 2, 2009
28,137
I would have thought it hardly worth it considering the Very cheap costs of having boards made that come with the options of double-sided and through hole plating etc?
You only need one piece single-sided board for a DIY project.
It cost you nothing since you already have the CNC machine and the PCB material.
Besides, you can't beat the turn-around time.

#### BobTPH

Joined Jun 5, 2013
6,305
This was a couple of years ago, so my memory is foggy on the details.

Candle was at least one of the programs I tried, there may have been others.

Bob, I wonder if your height mapping is done correctly and is being applied during the milling?
I certainly thought I was using it, but that is an interesting idea since it did not seem to improve the situation. Perhaps I will revisit this and ask for help here.

#### MrChips

Joined Oct 2, 2009
28,137
I suggest milling the mounting surface flat then use double sided carpet tape.
If your machine isn’t sturdy enough to mill the mounting surface, use a dial indicator to adjust it flat like a 3-D printer platform.
That is an idea that never crossed my mind.
You need a sacrificial layer under the copper laminate in any case. I use a piece of plywood, hardboard, or Masonite.
Why not use a more dense material and mill the surface with a face cutter.
Would this mean that the surface will now be level to the cutting tool and not require z-probing?
I doubt it, not for the precision required for PCB engraving.

#### DNA Robotics

Joined Jun 13, 2014
637
Done on an old milling machine that I made CNC.
Milled the sacrificial aluminum mounting surface flat then use double sided carpet tape.
NO Z mapping.

There is a 40 pin IC socket sticking up from underneath.