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workbee deflection Z axis

Discussion in 'CNC Mills/Routers' started by XelNaha, Mar 10, 2019.

  1. XelNaha

    XelNaha New
    Builder

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    Hi all,

    This will be my first post here, so please go easy on me :)

    I have had a workbee CNC for a while now, screw driven. I got this machine as I saw plenty of people cut aluminium with it, with good surface finishes.

    For some reason I cannot get it to cut aluminum decently, and even acrylic comes out all wringkly. When I made aluminum cuts as per recommended settings by Ooznest (700mm, 0.2mm DOC) the z-axis seems to deflect a lot. It also seems to be directional.

    I Have tightened the exccentric nuts however that doesn't seem to help much. Any ideas where this deflection comes from and how to solve it?

    Thanks

    edit: few example videos of what I mean:
    Dropbox - IMG_2060.MOV
    Dropbox - IMG_2062.MOV
    Dropbox - IMG_0016 2018-08-16 08_59_56.MOV
    Dropbox - IMG_2061.MOV
    Dropbox - IMG_0017 2018-08-16 08_59_55.MOV
     
    #1 XelNaha, Mar 10, 2019
    Last edited: Mar 10, 2019
  2. GrayUK

    GrayUK Openbuilds Team Elder
    Staff Member Moderator Builder

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    Hi XelNaha and Welcome.
    I guess, to save a lot of time, a video of what's happening or at least some pictures, is what is needed here to be able to help you better.
     
  3. Gary Caruso

    Gary Caruso OpenBuilds Team
    Staff Member Moderator Builder

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    Hi XelNaha, Something does look loose, maybe your collars on your z are not tight or your getting screw flex in compression on the longer axis?
    With Trochoidal tool-paths (the way to go IMO for aluminum cutting on these soft machines) you should be able to do 3mm or more DOC and you can move faster.
    Since this video below, I like standard 2 flute 1/8", been liking these linked.. Found with ~4mm DOC the chips clear more reliable and I don't have to babysit the machine at all.
    The step-over advance for the cut is only 4 to 4.5% of bit diameter, my machine can't do more than that without random bit breaking. 4% finish pass, full depth on 1/4" material or 1/4" at a time on 1/2" material.
    55% width for better chip clearing and lower radial contact, also cut in Climb direction (looks like you are already).

     
    #3 Gary Caruso, Mar 10, 2019
    Last edited: Mar 10, 2019
  4. GrayUK

    GrayUK Openbuilds Team Elder
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    Thanks for the videos. It is hard to tell when you're holding the camera, whether the movement is the machine or the camera, but that last video seemed to show a fair bit of flex. Is there some way you could temporarily wedge something between the router and the back support, as high as possible, to try to eliminate some of that flex? It won't matter if it moves the tip away from the norm, just as long as it is a constant stress without movement.
     

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