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IndustryArena Forum > MetalWorking Machines > Benchtop Machines > Optimum BF20L cnc conversion accuracy problem
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  1. #1
    Join Date
    May 2008
    Posts
    2

    Question Optimum BF20L cnc conversion accuracy problem

    Hello everyone,

    I have just finished conversion of my benchtop milling machine. (I did not change screws). Now i am facing with accuracy problems. X and Y axis run accurately when i operate single axis. In circular interpolation mode results are disappointing. Photo is attached. What am i doing wrong?

    Attachment 368040

    Attachment 368042

    Attachment 368044

    Attachment 368046

  2. #2
    Join Date
    Dec 2009
    Posts
    1416

    Re: Optimum BF20L cnc conversion accuracy problem

    I'm not sure what I'm looking at there, but I'm guessing that is the mill drawing with a pen in the spindle.


    Circular (good) interpolation requires very low backlash. The trouble usually shows up at the quadrants. Where X or Y is coming to a stop and then reversing direction. Any backlash means the transition to the reverse direction does not occur on time and deforms the circle. That seems like it could be what we are seeing there. X continues on moving but Y has not actually started to produce the reversed motion yet even though the motor is turning the screw correctly. When it finally does 'catch' and start moving, that creates the weird flat - to - elbow mark in the circle.

    Check your Y axis backlash all around the table. I suspect that is the (main) culprit at the moment. Recheck all the mounting links from the ACME nut to the saddle on down to the bearings in the Y axis motor mount. Looks to me like something has some serious slop in it.
    CNC: Making incorrect parts and breaking stuff, faster and with greater precision.

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