Re: [CAD_CAM_EDM_DRO] CNC Milling PCB's

i am very interested in what you are doing , i to want to make some
circuit boards for my own use in electronic projects using the
routing method, i would like to get away from chemical etching
i do have a question on routing PCB how narrow can the cuts be
made also how narrow can the runs be made ?

On Tue, 27 Nov 2001 09:19:20 -0000 ian@... writes:

> Around 6 Weeks ago I decided as I had a CNC mill I should produce
> PCB's by milling an isolation slot. During investigating the process
>
> I posted to various news groups for information and several people
> asked me to let them know the results of my searches. This is how I
> finally got G code to mill and drill the first board. (Note I
> haven't
> actually machined a real board yet, I guess that will be another
> story). I decided early on I would like to first do a single sided
> board, milling and drilling the bottom of the board with the copper
> side up which meant I had to mirror all data. Something else I
> should
> have decided early on was what units to work in. I would recommend
> imperial units for a number of reasons despite being based in the
> UK.
> I had a Gerber file generated from my PCB software so first I had to
>
> convert it to G code. Someone suggested KellyCam for this and it
> worked on a very simple file but not on the actual job I wanted to
> do
> (the resulting G code cut the tracks where they should not be cut!)
> and the author has suspended support for the time being. The next
> suggestion was Eagle PCB software which has the capability of
> generating suitable code. First I had to get the Gerber file into
> Eagle format. I found 2powtool_gbr2scr1_20.exe in the user files on
> the Eagle Web site and tried that. It would not import my files
> properly. They came in OK but all 45 degree tracks were not joined
> to
> the horizontal section of the same track although 90 degree tracks
> were fine. I contacted the author Falk Stricker and by return
> received a later version to try. Unfortunately that didn't work
> either and so I sent my file to Falk. His support was first class
> and
> within a day he came back to me and advised the problem was in Eagle
>
> in that it was incorrectly identifying the tracks as being on
> different circuits and therefore was isolating them. This problem
> only occurs in Eagle 4 not 3 and the solution is to alter the wire
> clearance in Eagles rules to 0. Having done this time my Gerber file
>
> came in perfectly. Incidentally like a lot of processes in Eagle
> what
> Falk's programme does is generate a script file. You run the
> generated script from within Eagle to draw the board. Also by this
> time I had discovered it was better to mirror the Gerber file in my
> PCB software because I knew how to control the X value of the mirror
>
> line which is something I still have not figured out how to do in
> Eagle. I also discovered that it is much easier to use a Gerber file
>
> in extended format that contains all the D code values otherwise you
>
> need a separate file that contains all the pad and track size data.
> By this time I knew more about Gerber format than I ever really
> wanted to know. The next thing was how to generate the cuter path
> around the Eagle tracks and pads. A search of the Eagle site came up
>
> with outlines.ulp a user programme that did just that and it works.
> (
> I did not know at that time there was a version of this on the
> CAD_CAM_EDM_DRO group that produces G code directly, more of this
> later) The version that comes with Eagle generates a script file
> that
> when run produces a narrow PCB track on a different layer that runs
> round the outside of all the actual circuit pads & tracks and if a
> small cutter followed this track it would isolate the pad and track
> just as I required. A couple of points if you intend to use it. In
> the dialogue box that opens You must set Device to "Script", Width
> to
> a value other than 0 (I used 0.1) & Layer to the layer your actual
> circuit is on, 16 in my case as this is the "Bottom" layer in Eagle.
>
> Also check exactly where the script file is going to end up. I had
> real fun with scripts of the same name in different directories,
> caused a lot of confusion to start with. Hit the OK button and once
> again a script is generated. This can take a long time with a
> complicated board on a slow computer. At first I did not think any
> thing was happening so give it time. Eventually it stops and you can
>
> run the script and the new tracks are generated before your eyes.
> You
> get an error message about layers but it does not stop it working.
> Eventually I hacked outlines.ulp to always produce a script of a 0.1
>
> track to a named layer to avoid the error message. Now I had a
> narrow
> PCB track to machine but how to get that to G code. At this time I
> did not know about PENGUIN CNC web site that has a programme that
> takes the Gerber code produced by the standard cam processor in
> Eagle
> and converts it to G code. Why do you always discover on the
> Internet
> that some one else has solved your problem AFTER you go through the
> process yourself..... I searched for hours on Gerber and G code
> isolation without success. Perhaps this is the "First Law of
> Internet
> Searching". Fortunately the Cam Processor in Eagle is controlled by
> an ASCII file that you can add to and after studying the
> documentation I added a section called Fanuc and with a fair bit of
> trial & error I got code suitable for my control software. I use
> Ahha
> and that follows the Fanuc standard very closely. However there was
> still a major problem. I could not get Eagle to output a decimal
> point in the code which Ahha needs and despite a number of posts to
> the Eagle news groups I could not find out if it was even possible.
> I
> should point out at this stage I am using the free Eagle version so
> I
> am not eligible for support from Eagle. By editing in decimal points
>
> manually I proved that the code generated was good so I trawled the
> web for a parsing programme that would put in the decimal point,
> without success. I have done some programming so I put together a
> simple programme using Visual Basic being the quickest I could code
> in and after the usual debugging got a result that generated a copy
> of the Eagle output with the decimal point. Hallelujah, the code
> produces perfect tracking on my g code simulator. Now to drill the
> holes. Well there is no drill information in the Eagle file produced
>
> from the imported Gerber file so I went back to my original PCB
> software. There it was Excellon output, great what does it produce
> and how can you get mirrored data? Quick look at the Excellon file
> and what is it, just a string of X Y data, no Z information , no
> decimal point, and in my PCB software no means of mirroring. Back to
>
> the Basic programme and add all the stuff to convert Excellon files
> and also mirror around a specific value. Some time later I was
> getting a result. A bit more debugging and I at last I am getting
> perfect simulation with isolation milling and holes drilled in the
> right places. This time I did not bother to search the Web and if I
> had have done I would have found that Hans WEDEMER who is well known
>
> on the CAD_CAM_EDM_DRO group has already written an Excellon to G
> code converter available for down load from his web site. All I have
>
> got to do now is rig up a high speed spindle and try it out. Having
> got to this stage I also discovered during a web search that there
> is
> in the CAD_CAM_EDM_DRO files section an Eagle programme called
> outlines_gcode.ulp. I immediately tried it and it certainly
> generated
> G code. The format was not quite right for my control and the
> simulation did not look quite right but had I discovered it earlier
> I
> would have pursued modifying that as it removes 2 steps from the
> process that I have to go through. Still I guess that's life.
> Details
> of all the CNC milling of PCB resources I have found which may be
> useful to others:-
>
> Eagle software free version at http://www.cadsoft.de/
>
> Gerber Importer 2powtool_gbr2scr1_20.exe from Falk Stricker in user
> files at http://www.cadsoft.de/
>
> Outlines.ulp Comes with Eagle outlines_gcode.ulp at
> http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/MaxNC-
> PCB/outlines_gcode.ulp
>
> Gerber format to G code programme or direct web processing if
> preferred by Henry Palonen at http://www.yty.net/cnc/
>
> Excellon to G code converter from Hans Wedemeyer at http://hans-
> w.com/
>
> If any one would like the Fanuc section I produced to insert in the
> Eagle.def Cam processor definitions file I can upload it to the
> files
> section of the CAD_CAM_EDM_DRO
> If any one would like the programme I have written let me know but
> be
> warned it is pretty crude and being Windoze weighs in about 2.8 Meg
> or the VB source which is about 47k zipped.
> I know, it could probably be 100K for the executable in C but then I
>
> would still be writing it..........
> If any one else can add to this any other information or tips about
> producing PCB's by CNC milling and drilling I would be pleased to
> hear from them.
>
> I hope this helps someone.
>
> Regards Ian Eagland
>
>
>
>
>
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