Hello
I am looking for a machine to produce printed circuits in CNC
Delimitation of tracks
drilling
Delimitation of the map.
All this compatible with Kicad
I make circuits small 12cm * 9cm maximum
And if this machine is also a 3D printer, i will enjoy !
Thank you for sharing your experiences.
Yves Accard
http://www.onebus.fr/video/CNC.jpg
It is possible to do PCBs on this sort of set up but it is not easy to get good results.
The workflow I have used is KiCad -> Gerber -> Rapid-pcb.com -> Gcode -> LinuxCNC. I have also tried Flatcam but had some problems setting it up on a mac. There is quite an well featured ULP for Eagle that does PCB->GCode directly so you could bring your board into Eagle and then export the GCode once you had done all the proper design work using KiCad 
Some of the problems you might find are;
-
Board is never flat! There are a variety of auto leveller solutions which probe the board first to produce a contour map and offset the gcode to allow for the unevenness. Isolation cuts of 0.1mm are all that is needed but if part of the board is low you may not cut an isolation track and if too high you may not have any track left! Vacuum tables help but you still need to level.
-
You don’t have a solder mask - SMT component placement is possible but not easy. 1206 is doable, not tried anything smaller.
-
Two sided boards need a mounting jig to ensure alignment.
-
You need a very high speed spindle and good dust removal.
-
I am not sure the gantry you picture would be sufficiently rigid for milling board out unless you were very careful with your step-down.
I have seen people advocating using this sort of setup to use a sharp point to score through a resist (e.g. permanent felt tip drawn over the copper) and then etch. (you then have all the mess of etching and the problem of aligning the drilling).
On the plus side, you have the board in your hand in a very short time.
The place I work has two CNC machines similar to the picture. They do NOT use them for PCB’s - they are used to machine mechanical parts (panels, brackets, mounts, handles, etc, etc) from HDPE sheet. Based on my experience in that environment, everything @John_Pateman mentioned is true - VERY true!
The machines at work have working areas on the order of 2 ft X 2 ft (approx 65 cm X 65 cm). They are designed for machining wood and plastic parts where errors in location, flatness, and perpendicularity on the order of 5 to 10 mils is acceptable. I imagine that scaling these machines down to something like 25 cm X 25 cm may improve that performance but it still falls short of the quick-turn board houses.
The machines at work seem to require a fair amount of maintenance. They use routers mounted on the carriage, which need replacement every few months. (The machines are in use about 20 hours/week.) The cutters (router bits) need sharpening or replacement every month or so. The tracks and slides need regular cleaning and lubrication. A typical job probably requires 20 to 30 minutes of the operator’s time to set up and align.
Of course, soldermask, legend (silkscreen) and anything more than two layers are unresolved problems.
Like @John_Pateman said, something like this may be useful for one-off boards that are needed in a day or two. It’s close, but doesn’t quite meet the requirements for producing general prototype boards and certainly wouldn’t produce even low-rate production parts.
Dale
I have owned and built a few of these machines over the past 20 years or so and they have all produced good useable pcb’s.
I was lucky enough to find an old lpkf92 on ebay for $500. The lpkf has a router head that compensates for non-flatness of the pcb on the machine table and this makes the job a whole lot easier. If you can find a machine with this feature it is well worth paying extra for it.
The picture shows a 0.5mm qfp footprint I did a few weeks ago
2 Likes
@slc I can confirm that PBC production with a CNC is a useful tool for prototype testing and getting the final layout nailed down.
CurrentlyI am using Target 3001 which has a nice Wizard to greate all required files for the CNC router. However, I really would like to move to Kicad and I’d be interested in any proved setups for exporting the PCB as C-code and drill files.
Also I’d be interested if anyone got some experience with doing plastic solder masks with a standard CO2 laser cutter/engraver. I might have access to one, but would’nt like to ask if its a waste of time…
I doubt one can use the same rules for cnc production as for normal production. (Clearance will be larger, possibly min width is also larger.)
Meaning getting the finalized layout tested is not really an option. (Unless you are prepared to use these much larger clearances instead of the capabilities of your fab.)
I see what you mean. I was more thinking about the placement of parts, mechanical capability during product assembly, heat distribution under load etc. So indeed, “finally nailed down” would need another step to optimize for serial production, emc etc.
If I need different set of design rule checks for the CNC and fab version, I would have thought threre is a way in Kicad to handle that.
Right now I would be happy if getting the pcb done on a CNC router can be set up with Kicad and whatever tool to work as a robust and easy to use process. With robust I mean good usability, easy to change parameters, sync behind the scenes between the tools, etc.
The Bantam Tools Desktop PCB Milling Machine claims to be able to support 6 mil trace and clearance.