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Re: [Pcb2gcode-devel] PCB Board Expectations
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From: Filip D. <fil...@gm...> - 2012-12-11 15:19:07
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Instead of tinning, I usually email the PCB with fuse dissolved in ethanol. Not only it could provide chemical preservation of copper, but mainly it helps a lot with soldering SMD parts. But I have not seen my circuits after, say, 20 years; maybe the fuse will deteriorate. The fuse email also greatly simplifies the tinning of any thin parts of the PCB. Another improvement in milling thin routes (for TQFP) came when I spent an evening writing an G-code importer which prevents the tool from milling any route twice. (Write me please if you want the source.) Additionally, we are developing another PCB importing program which solves the problem of finding the cutting paths mathematically exactly in the sigma metric. Preliminary testing looks good and I will write to the mailinglist as soon as it proves to be working in practice. I am in favor to add the vector solver to PCB2GCODE and to let the user choose which engine will be used. What do you think about this? F. 2012/12/11, Ford Peterson <fo...@hi...>: > I think you found my problem(s). Thanks to Pat for taking the time to > consider my situation. > > I was leaving the copper foil on the board and the Gerber output was > defining it. So by leaving it on the board, suddenly pcb2gcode needed to > deal with those edges as well and started tweaking the insulation path on a > second pass. By eliminating the copper fill, only the meaningful traces > appear in the Gerber, and consequently the GCode for LinuxCNC. One pass. > > Also, the offset attribute is defined as being 1/2 the bit size. In a > perfect world, this is true. My world is far from perfect. My dremel tool > has some run out in the z-axis. I have a new spindle on order but won't be > here for another week or so. I disassembled the dremel and discovered they > took care in holding the shear motion (side pressure) on the cutter through > the use of ball bearings at each end of the spindle/motor shaft. Using a > V-bit, the tool wants to climb on top of the copper, forcing me to set the > depth deeper to put down pressure on the bit. I'm guessing this surplus > board stock has copper of roughly 0.003" or so. I need to set it at a > depth >>0.008" and a 0.010" is most reliable. In a reliable cut, this 0.004" bit > seems to cut a 0.012"-0.015" insulation width. So by setting the offset > attribute to 1/2 the average width (e.g. ~ 0.0075") I am able to get traces > down to 0.018" or so. That's a fairly small trace. I'm not sure how much > glue is left to hold the trace after soldering. > > Obviously, if I want decent output, it will have to start with a decent > spindle. I'm working on that. > > Chemically tinning the circuit board is important for long term reliability > (the copper will rust). Have others experimented with tinning? Does it > improve routing quality or make it more complex? > > Ford > > > -----Original Message----- > From: Patrick Birnzain [mailto:pbi...@us...] > Sent: Monday, December 10, 2012 6:45 AM > To: pcb...@li... > Subject: Re: [Pcb2gcode-devel] PCB Board Expectations > > On Sun, 9 Dec 2012 21:05:11 -0600 > "Ford Peterson" <fo...@hi...> wrote: > >> Good evening, >> >> >> >> I'm new to this forum. I'm trying to diagnose some problems with this > GCode >> conversion tool. >> >> >> >> Using KiCAD for circuit board design and layout, I'm able to extract > Gerber >> files. Pcb2gcode converts them for running LinuxCNC under Ubuntu 10.04 > LTS, >> which is the most recent stable version for running LinuxCNC. My router >> table seems to be able to reliably hold a repeatable trace. I have > several >> concerns and am hoping this list can provide some reliable answers. >> >> >> >> While the spindle on my CNC is light duty (a ball bearing dremel tool >> running a 0.1mm 60 degree V bit). I have a new spindle on order and may > not >> see it for another week or so. Adjusting the Z axis to obtain a cut >> sufficient to remove copper, the narrowest insulation I can obtain with > this >> 0.00397" V bit is about 0.030" using a micrometer. Thinking this >> through, >> am I observing the run-out in the bearing at being roughly 0.026" ? >> Inspecting the spindle I simply cannot believe there is that much play. >> I >> would certainly expect to visibly see 0.026" of play and I'm unable to >> observe ANY play in the spindle at rest. While I was expecting some >> play, > I >> was not expecting this much. Are my expectations unreasonable? > > I'm using a small proxxon rotary tool as well (quite successfully) and > a cheap, single-toothed bit. I noticed the isolation diameter changes > somewhat if the bit is turned in the collet, sometimes requiring > adjustment for boards with ICs in smaller packages (MLF). > Maybe the collet isn't that accurate, or the center axis of the ball > bearing is somewhat misaligned to the axis of the motor? Taking into > account how ball bearings work, the bit might even end up at a very > slight angle. I can't really tell as I'm not a mechanical engineer and > as long as it works reliably there's litte incentive to investigate. > >> >> >> Using a test circuit called TraceTest I've installed nine SM1206 resistor >> footprints and connected them in series using trace widths ranging from >> 0.018" to 0.042". I convert the Gerber to GCode with the following > command >> line: >> >> >> >> pcb2gcode --front TraceTest-Front.gbr --zsafe 0.08 --zchange 1 > --mill-feed >> 6 --zwork -0.08 --offset 0.002 --mill-speed 20000 >> >> >> >> Even though the Gerber files were produced by specifying a 0.004" bit, a >> 0.004" insulating band, pcb2gcode insists on retracing the board a second >> time. After a first pass, a 0.042" wide trace remains but only about > 0.010" >> wide. The second pass obliterates the traces and the pads. I either do > not >> understand the offset attribute or my spindle is simply a POS. >> >> >> >> I do not see an attribute for bit size. Only the -offset, which I've set > at >> 0.002" (half the bit size) It seems the second pass enlarges the > insulation >> by taking part of the trace. I experimented a little with a negative > offset >> and saw no real difference. > > Do you have the remaining copper in the gerber file? The pcb2gcode > algorithm expects you to have only the actual traces in the file. It > takes your parameters (offset, extra-passes etc.) and tries to mill the > board as close to your specifications as possible in a best-effort > approach. If the remaining copper is in there as well, it will be > treated just like everything else. > > I hope this helps, if not I can check your test file if you want. > > -- Patrick > > ---------------------------------------------------------------------------- > -- > LogMeIn Rescue: Anywhere, Anytime Remote support for IT. Free Trial > Remotely access PCs and mobile devices and provide instant support > Improve your efficiency, and focus on delivering more value-add services > Discover what IT Professionals Know. Rescue delivers > http://p.sf.net/sfu/logmein_12329d2d > _______________________________________________ > Pcb2gcode-devel mailing list > Pcb...@li... > https://lists.sourceforge.net/lists/listinfo/pcb2gcode-devel > > > ----- > No virus found in this message. > Checked by AVG - www.avg.com > Version: 2012.0.2221 / Virus Database: 2634/5449 - Release Date: 12/10/12 > > > ------------------------------------------------------------------------------ > LogMeIn Rescue: Anywhere, Anytime Remote support for IT. Free Trial > Remotely access PCs and mobile devices and provide instant support > Improve your efficiency, and focus on delivering more value-add services > Discover what IT Professionals Know. Rescue delivers > http://p.sf.net/sfu/logmein_12329d2d > _______________________________________________ > Pcb2gcode-devel mailing list > Pcb...@li... > https://lists.sourceforge.net/lists/listinfo/pcb2gcode-devel > |
