PCB making using milling machine


#1

I noticed the milling machine had been used. Will it be available for everyone to use? I would like to have a go at making PCBs. I can buy and donate some materials and bits. Is there anyone who could help me out.? I have designed multi-layer and two layer PCBs in the past. I can have a go at a 1 layer design. Will probably be a small stamp sized board to start with. I can produce gerbers for a copper layer and routing and a drill file for any through hole components and mounting points.

I know for a milling machine its best to fill the copper to reduce the amount that needs to be removed. I usually add the printing to the copper layer. There is no need for a solder mask to start with. (Use tarnished copper and polish where you want to solder usually does it.)

We could try two layer but this adds the complication of flipping and aligning the PCB. Also we may have to get some vias. The prototyper I have used before used rivets as vias that were hand fitted. If there are no vias in the design then sometimes you can get away with soldering both sides of a through whole component.

Any advice of file formats, parts or tools needed, or anything else is very welcome. Any donations of scraps for testing very welcome.


#2

I’d also like to have a go at PCB milling, but have no experience of it. Let us know if you get anywhere with it


#3

Hi,
I’ve been playing with the shapeoko cnc and I assume this is the machine you are interested in.

The shapeoko is a ‘work in progress’ I have managed to get it connected up and cutting with G-code sent from my laptop; but thats about it, so its not a ‘turn key’ system.

I have no experience of PCBs so I can’t really advise there, however if you are prepared to get stuck in with the mill and experiment then I can show you what I’ve done to so far which should save you a couple of hours googling and head-scratching.

Are you able to make it to the wednesday night meet up?


#4

Some double sided boards have arrived. I will try and make it Wednesday and bring them along. Happy to leave a few for tinkering purposes. I will look into generating the gcode from Eagle. There looks to be some 1mm bits for milling PCB at the space but I think we need some 0.1 or 0.2mm V bits for the “engraving”. Do we have any? They are available to buy but are all different angles and I am not sure which to get. Looks like 15 - 60 degrees. I guess lower angles will give better tolerance. Perhaps, however, they will be weaker?


#5

I’m going to be there tonight. If you can make it we should be able to sort something out.


#6

Thanks for your help. I have written up some things on the wiki.

Still very much a work in progress. Lots of issues to address.

Not sure the Wiki it is organised sensibly.
http://www.cheltenhamhackspace.org/wiki/PCB_Prototyping
http://www.cheltenhamhackspace.org/wiki/CNC_Router
http://www.cheltenhamhackspace.org/wiki/PCB-Gcode

I milled a PCB that was unusable for a number of reasons but showed a proof of concept.


#7

Not so good progress last night. The fuse on the motor speed controller has gone. (5A 20mm)
Also I was hoping to run the “etch” then the “dill” job.
However it looks like the origin is taken as the position when you start the job, not the currently set zero.
Thinking about it I will try and return the bit to the origin before starting the drilling.
The sequence has to take into account that the drill and the etching bits may not be the same length.
I was unsure how to do this without crashing into the work, if the drill bit was longer than the etching bit.
However I think it can be done as follows.
Insert etching bit.
Choose an origin and reset zero.
Run etching.
This finishes in a position where the bit can be changed.
I think the steps should be…
Remove the etching bit.
Return to zero. (without the drill bit so it does not crash into the work)
Now raise the drill again and insert the drill bit.
Now reset the Z zero.
With the tip of the drill bit now at the original origin.
Run the drill sequence.


#8

A little better tonight. The mill is loosing accuracy when performing misc activities. There was a lot greater reproducibility when I change all the speeds to a low value. I found I had to change the setting in the mill too as some speeds are preset. Setting everything to 100 gave much better results. Still not able to maintain accuracy between etching and the drilling. Also there was a bit of a strange issue that the pilot holes done during the “etching” were very deep, a mm or two, not 0.2mm. I think I can turn of the pilot hole feature.


#9

Single sided looks to be working well. Last piece of the puzzle was to use double sided sticky for the PCB and clamp only the sacrificial base material, not the PCB. In this case foam was used as a base.

0.25mm depth engraving followed by 0.7mm drilling to a depth of 2mm, and then 1mm milling to 2mm depth.
It stopped engraving part way through due to a screen saver, but was engraved enough to carry on.

Historical issues.
Removed final command in exporter software so that origin is not reset between jobs.
Slop issues were due to loose cogs. These were tightened, may need to be tightened again.
I have increase current to the two Y steppers by adjusting the pot on the stepper controller.
Z axis zeroed using a piece of paper.
I reduced some of the speeds. I think the issue was the cogs so I will try again back at the default speeds.
Blew a drill motor fuse at some point, possibly a crash. Replaced this with same and no problems since.
Disabled the spot drilling done at the engraving stage as it was cutting deeper than it should be. The idea is the engraving leaves a center for the drilling stage. I did not see this used on any youtube vids.
Engraving/Drillinig alignment is not perfect but best mitigated with large pads in the design.