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Using CNC to mill PCB traces? — Parallax Forums

Using CNC to mill PCB traces?

Martin HodgeMartin Hodge Posts: 1,246
edited 2010-01-31 18:35 in General Discussion
One can find a lot of videos on youtube showing printed circuit boards being "etched" in home made CNC mills. I watch these and think "Why?!". Is this really a legitimate way to make prototype PCBs? It seems exceedingly "Rube Goldberg" to me. What am I missing?

www.youtube.com/watch?v=bHCCCjdnbQ4

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Martin Hodge
webbolts.com
forumexperts.com

Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-01-28 04:32
    What you're missing are the nasty etching chemicals that not only pose disposal issues but instantly rust every tool and steel implement within 30 feet of their subtle, but noxious fumes. I've built boards this way on my CNC mill. It's not easy, since the board has to be absolutely flat, and precision depth control is essential. Also the optimum rotational speed for the tiny cutters normally used for this app is in the tens of thousands of RPMs, beyond the range of most CNC mills.

    -Phil
  • Martin HodgeMartin Hodge Posts: 1,246
    edited 2010-01-28 04:36
    I now see there are some commercial pcb milling machines. Huh, I never considered this. You learn something new every day.

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    Martin Hodge
    webbolts.com
    forumexperts.com
  • W9GFOW9GFO Posts: 4,010
    edited 2010-01-28 05:02
    I use my Sherline to mill PCBs. It works fine even though I have a 3,000 rpm spindle. I just have to be patient. Someday I'll get a Wolfgang spindle and cut my milling time to a few minutes rather than an hour.

    website_pics._021.2jpg.jpg

    Rich H

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  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-01-28 05:17
    Rich,

    I had a Sherline once, retrofitted for CNC work. You have my utmost respect (and sympathy) for engraving PCBs on that equipment! smile.gif

    -Phil
  • W9GFOW9GFO Posts: 4,010
    edited 2010-01-28 05:39
    Phil Pilgrim (PhiPi) said...
    I had a Sherline once, retrofitted for CNC work. You have my utmost respect (and sympathy) for engraving PCBs on that equipment! smile.gif

    I do remember this coming up before about your Sherline lacking in the accuracy dept, you now have a nice commercial machine I think - so I am jealous of that. wink.gif

    The biggest challenge I have is lining up the board just right to mill the other side. Once I verify (maybe make small adjustments) that it is milling evenly around the holes, whatever inaccuracies there are, are not apparent. I just walk away and let it do it's thing. So far, every board milled has been useable.

    I'm quite happy with my 4 axis CNC Sherline.

    Rich H

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    The Simple Servo Tester, a kit from Gadget Gangster.
  • CannibalRoboticsCannibalRobotics Posts: 535
    edited 2010-01-31 14:44
    Seems like a dremel tool, with it's 10,000 RPM speed would retrofit nicely?

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  • W9GFOW9GFO Posts: 4,010
    edited 2010-01-31 18:16
    CannibalRobotics said...
    Seems like a dremel tool, with it's 10,000 RPM speed would retrofit nicely?

    I think Dremels go up to around 30,000 but yes, it is an option that I have considered. Run out may be more than I'd like but probably not a problem for the boards I am making.

    Rich H

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    The Simple Servo Tester, a kit from Gadget Gangster.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-01-31 18:35
    Rich,

    Maybe you've tried this for aligning both sides, but here's what I would do: Before milling the first side, drill a rectangular pattern of four 1/8" holes through the edges of the board, in the margins, clear through and about 1/2" into a particleboard substrate. (The substrate has to be fixtured separately from the PCB.) When the first side has been engraved, flip the board over, and secure it through the holes with 1/8" pins or brass rivets. This will ensure accurate registration between the two sides.

    This is similar to the technique I use to router proto PCBs from a board house out of panel, except that the alignment holes are designed into the board. The first thing I do is drill the corresponding registration holes in the particleboard, then secure the board using rivets and masking tape. It eliminates having to line up and register the board manually.

    -Phil
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