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C-Beam machine for PCB milling

Discussion in 'CNC Mills/Routers' started by drpeej, Feb 23, 2016.

  1. drpeej

    drpeej Well-Known
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    I am looking for a CNC router primarily to isolation-route PCB boards. The C-Beam seems to be about the right size and I wonder if it is suitable.

    One thing I have been advised is that the lead screw is not precise enough and I should consider using an 8x1.5 Acme screw instead of the supplied 8x8. However I cannot find anything about this on the web.

    Can someone please advise?
     
  2. David the swarfer

    David the swarfer OpenBuilds Team
    Staff Member Moderator Builder

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    I think a C-beam will do it just fine for PCB milling.

    8x8 leadscrew can give you about , well, lots of resolution (-:
    200 step per rev motor, using 16 microsteps, will give you 0.0025mm per step. overkill!
    however, not all microsteps are created equal so rather user 4x or 8x.
    8x would give you half a hundreth, 0.005mm per step
    4x would give you 0.01mm per step, and a lot more power and accuracy. My OX will use this setting (-:

    Another thing that will affect your PCB success is flatness of the frame and bed. When milling a PCB your cut depth is very small, so small variations in bed flatness will affect the cut depth and thus cut width, a lot. (assuming you are using a V bit)
    So, align the frame as best you can, make sure it is on a stable table that will not move and affect the frame.
    Make the bed in 2 parts, a main bed as is shown in the OX/C-beam instructions, and a bit of 1/2" MDF on top that you can flatten before every PCB cut session. Consider using vacuum to hold the PCB flat to the nicely flat bed, PCB likes to curl a little...

    Now, getting things super flat can be tricky, so an alternative is to use software to 'virtually ' flatten it for you. Assuming your controller is GRBL based, you can use bCNC and a probe to compensate the Gcode for the 'non-flatness' of the bed.
    GitHub - vlachoudis/bCNC: GRBL CNC command sender, autoleveler and g-code editor
     
  3. drpeej

    drpeej Well-Known
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    Thanks for the advice - that's really helpful. I am currently using a micro-mill hat I have adapted to CNC but it is too small for my needs.

    I currently use Arduino/GShield and GCode Sender and I hope to use the same controller setup. I have heard about the auto leveller but I thought it only worked with Mach3.
     

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