On Sunday 08 April 2018 01:05:53 Chris Albertson wrote:
> Is anyone using a CNC mill to make PCBs? The video linked below shows
> someone doing this on a small mill with Mach 3. The PCB is certainly
> not high tech. The parts are all through hole with 0.1 inch lead
> pitch and it is one side only. Right out of the 1970's but it is
> exactly what I want to make. More complex PCBs can go to oshpark
> Is there a Linux based tool chain? The part I don't see is how to
> convert Gerber files to g-code files.
I have done that. Composed the things in eagle, then made gcode out of it
with pcb-gcode. Worked but not real well for double sided because in
the first instance I wasn't able to arrange it so I could solder both
sides if the board and had to use a thin iron tip and melt away the
sides of the photo-interrupters. But its been in my mini-lathe as the
spindle encoder for several years now. I should put a higher resolution
encoder on it as I've since found that an overkill times more resolution
encoder allows lots more Pgain to be used.
Registration of drill holes was done by putting a small brass tube for a
contact in one corner of the pallet holding the board, determining its
xy offsets, and zeroing the machine to that using a sewing machine
threader wire made quite sharp in profile mounted in a brass tube, and
writing a hole finder routine. Spin the wire in the chuck using g38.2 in
all 4 directions after driving the mill to put the spinning wire inside
the end of the tube. By spinning the wire it was electrically a perfect
cone. And the positioning repeatability was well within a thou.
I was able to drill a thru hole halfway thru the board from both sides
with good results, looked like I had drilled all the way thru, on an hf
micromill I've cnc'd with ball screws. Obviously I had to make a new
pallet for each size of pcb, using 0-80 flathead screws to fasten the
board into the pallet. And I had to fine sand the boards bottom side
once cut so the etching throw up on the edge of a trace didn't hold the
bottom of the board up off the pallet a thou or so. It worked, and I've
made several other boards that way, but really should have sent the
double sided stuff to oshpark. Quicker to a usable product. Try not to
cut any deeper than just enough to remove the copper, cutting into the
glass is hell on the v bit. FWIW, setting the bit to the boards surface
will offset the tool well into the glass as the drill chuck s tightened,
requiring a higher safe z setting when generating the gcode. Using a
drill chuck can also distort the cut, so use a suitable collet for top
> Then what tools work best? I think three are needed tiny end mill to
> route copper, Tiny spiral mill for cutting the PCB all the way through
> and a few micro side drill bits for the through holes.
> BTW it seems like the guy in the video could have saved a lot of time
> by using a (fake) ground plane that flooded all the empty space. No
> need to mill all that copper away.
Sounds like a lot of work, but I had fun proving I could do it. Next
week, I'd send it to oshpark... Or figure out how to plate thru-holes.
Cheers, Gene Heskett
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>
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