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  1. #1

    Join Date
    Mar 2019
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    3

    milling part off in Z

    I am a Jeweler cutting wax on my Minitech mini mill 2 and having some problems with the items not being true as in the thickness not being even from side to side or the thickness dimension is less then it should be. Are there any websites for jewelers not machinist with cnc milling machine issues?
    Where should I start in the troubleshooting process?
    Thanks George

  2. #2
    Registered
    Join Date
    Aug 2006
    Posts
    570

    Re: milling part off in Z

    I would start with your work holding. If you start with your part at an angle no matter how well your mill is trammed you'll always produce tapered parts.

  3. #3
    Gold Member
    Join Date
    Apr 2004
    Posts
    4782

    Re: milling part off in Z

    As well as work-holding (cheap vises tend to tilt the work as they tighten) look at tram. The bed of the mill needs to be in the same plane as the sweep of the spindle. You can test it by putting something in the spindle like a fly-cutter (at the most basic) or a dial indicator on an arm (which is easier to use and more precise), which you can turn by hand and see where it contacts something flat (the disk out of an old hard drive works well) that's laid on the bed. Side-to-side discrepancies are easy to adjust; front-to-back out-of-tramness may require shimming to correct.
    Andrew Werby
    Website

  4. #4

    Join Date
    Mar 2019
    Posts
    3

    Re: milling part off in Z

    The part is is in a sherline rotary, I cut the top side first and all looks good, then it rotates 180 and that is where the part starts off being good 2mm but as it goes Y+ it gets thinner to 1.5mm.
    Go figure....

  5. #5
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    Join Date
    Aug 2006
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    570

    Re: milling part off in Z

    well silly question, but are you sure the rotary is actually incrementing a full 180? If it only does 179.5, you'll be cutting a taper into your part.

  6. #6

    Join Date
    Mar 2019
    Posts
    3

    Re: milling part off in Z

    I checked the rotary by putting a line on the both sides of the rotary and all seams good.

  7. #7
    Registered
    Join Date
    Dec 2005
    Posts
    330

    Re: milling part off in Z

    First thing is to see if the manufacturer has instructions for setup and calibration.
    Second is support services from the manufacturer.

    Machining in rotary axis is very suseptible to errors, so setup and calibration is important.
    The rotary axis may have backlash, so take it out before each cut
    Make sure the rotary axis is locked with a screw while machining.
    Make sure the rotary axis is clamped flat to the milling machine.

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