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Thread: PCB milling

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  1. #1
    Join Date
    Apr 2013
    Posts
    1899

    PCB milling

    I made my first PCB with my upgraded CNC. It is a pulse stretcher circuit to stretch step pulses so that they can be made visible with the LEDs I have in my control box. The circuit is pretty simple, just a few resistors and capacitors and two 74HC04 inverters.

    Attachment 342308

    Anybody interested can just make the same circuit. If you are not happy with the pulse lengths you can play with the four resistors (R1, R2, R3, R4) and/or the four capacitors (C1, C2, C3, C4) to change the behaviour of the circuit. I used Eagle to draw the circuit and to create the layout.

    Attachment 342312

    Once that was done I used PCB Gcode to generate the g-code. It is a free plugin for Eagle.

    The PCB turned out really nice, no additional work needed with cleaning the tracks or anything at all. Traces are beautifully milled follow what's been routed with the auto router of Eagle. Manually routing or double sided PCB would have created a more beautiful art work, but it's good enough. Due to lack of 1.2mm high speed PCB drill, I used a simple twisted drill, which was a mistake. It slide into the collet after a few holes, so I had to drill those missed holes manually on a pillar drill. I didn't use the auto levelling plugin of UCCNC, mainly because I did not like the limitations that the probing area is not definable. Perhaps I missed something, but it seems to be necessary for it to start at XY = 0 which is wrong, since that is the edge of the PCB, and it seems to do the first probing along that line, from X0 to Xmax, which in this case is X-100 since X is moving in negative direction during the work because the tracks are on the bottom side of PCB. Probing along X0 is totally wrong in this case, so I found it useless. Also, since my table is levelled and the PCB is pretty small, I decided to skip auto levelling and try without, and I am glad I did that, it saved me a lot of time. Like I said, perhaps I missed something, but for now it does not matter.

    Some details about the machining data:

    Spindle speed: 22,000rpm
    Cutter: 30 degree 0.2mm V-bit engraving cutter
    Drill bits: high speed PCB drills, 0.6mm and 1.2mm
    Maximum milling depth: 0.07mm
    Isolation distance: 0.2375mm
    PCB type: fibre glass 1.6mm, FR4 with 35um copper layer
    Feed rates: 450mm/min first pass, 650mm/min second pass
    Z plunge rate for drilling: 250mm/min

    If anybody is interested in more details please visit my blog.

    https://adapting-camera.blogspot.se/...d-diy-cnc.html

    I also made a video about it, if you want you can see the "Making of..." and the before/after. I am very happy with the results.

    https://youtu.be/EDK46k3F1f0

    Edit:

    I just noticed an error in the video. I mill the first pass at 0.04mm depth and the second pass at 0.07mm and nothing else. In the video I wrote that I mill the first pass at 0.4mm and the second at 0.7 and that is just too much for PCB milling. The copper layer is just 0.035mm, so there is no need to mill deeper but I double that value to be on the safe side, however, making it 20 times deeper than necessary would be crazy.

  2. #2
    Soldertraining Guest

    Re: PCB milling

    PCB milling is the process of removing areas of copper from a sheet of printed circuit board material to recreate structures, pads, and signal traces according to patterns from a digital circuit board plan which is also known as layout file. It is used for prototyping and special PCB designs. A CNC machine is used to process milling, drilling and cutting.

  3. #3
    Join Date
    Apr 2013
    Posts
    1899

    Re: PCB milling

    Quote Originally Posted by Soldertraining View Post
    PCB milling is the process of removing areas of copper from a sheet of printed circuit board material to recreate structures, pads, and signal traces according to patterns from a digital circuit board plan which is also known as layout file. It is used for prototyping and special PCB designs. A CNC machine is used to process milling, drilling and cutting.
    Oh well... thanks for telling us the obvious...

  4. #4
    Join Date
    Sep 2005
    Posts
    287

    Re: PCB milling

    Quote Originally Posted by Soldertraining View Post
    PCB milling is the process of removing areas of copper from a sheet of printed circuit board material to recreate structures, pads, and signal traces according to patterns from a digital circuit board plan which is also known as layout file. It is used for prototyping and special PCB designs. A CNC machine is used to process milling, drilling and cutting.
    To anyone who is awestruck with that extremely valuable and informative piece of knowledge, check out his other informative posts. You won't be disappointed.

    Einstein, eat your heart out.

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