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  1. #1
    Join Date
    Feb 2020

    Default BF20LV CNC conversion

    Finally made the first metal cuts under full CNC control.
    The machine is a stock standard Optimum BF20LV purchased from H&F earlier this year.
    Retrofitted with stepper motors, linear encoders and a Raspberry Pi running LinuxCNC.
    Note that this conversion uses the standard ACME lead screws.
    Whilst the X+Y screws are OK, the Z axis screw leaves a lot to be desired.
    Backlash on X is 0.4mm and 0.2mm on Y-axis, however, the linear encoders are mounted directly onto the table so the control can compensate.

    Overall I am pleased with the outcome.
    But I have ordered ball screws to overcome the limitations of ACME screws and backlash.

  2. #2
    Join Date
    Apr 2009


    Congratulations on your first cuts, mine was only a few months ago - it is a great feeling.

    The use of a Raspeberry Pi is interesting.
    I am running LinuxCNC on an old desktop tower with Debian Wheezy, out of support but works fine.
    As this system is so old, I feel it prudent to have a fall-back option.
    Can you provide links to the sources and processes used ?

    Keep going,
    Keep well,

  3. #3
    Join Date
    Feb 2020


    Quote Originally Posted by electrosteam View Post
    Can you provide links to the sources and processes used ?
    Hi John,
    for the Raspberry Pi I used JT's instructions located here.
    Another set of instructions is here.
    Somewhere on the LinuxCNC forum I saw a reference to a downloadable image for the Pi ... maybe from andypugh?

    I've used Mesa's 7C81 card which connects to the Pi via SPI interface so you'll have no timing issues.
    I found the SPI interface a better solution for the Pi than the popular Mesa 7i76E Ethernet based card since the SPI is closer to the hardware core and isn't required for any other purpose.
    The stepper drives and encoders are connected via Mesa 7i85S card.

    A few more links with photos:
    Pi + Mesa 7C81
    Mesa 7i85S
    Siemens Digital IO modules

    Config files are on GitHub

    If you need any further information drop me an email on helioz2000 AT gmail DOT com
    Last edited by TheApprentice; 14th May 2020 at 11:18 PM. Reason: added detail

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