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Thread: V-carve - ridges left after cut

  1. #1
    Join Date
    Jan 2019
    Posts
    5

    Default V-carve - ridges left after cut

    Hi,

    Just curious if anybody has seen small little ridges left after a v-carve cut. The ridges seem to show between the toolpath operation of going up to create a sharp corner in the V-Carve and between doing a straight line or curve.

    I checked Z-Zero repeatability and it seems to change by .005-.010" after the cut is done. The Z actually goes downward which I found weird. Though it might adjust up a bit due to upward pressure when cutting. I reduced the cut depth to .1875 assuming it might be deflection. I am using a new collet and 1/2" 120deg v bit but this shows up with 90 degree bits as well.

    The gears in the XYZ appear to be fairly tight. There is a little click sound but very small movement.

    Any thoughts on things to try and check would be great!

    Thanks,

    Cory



    Picture 1.JPGPicture 2.JPG

  2. #2
    Join Date
    Jan 2011
    Location
    Buchanan Michigan
    Posts
    129

    Default

    Its difficult to see the issue in your photo. I would guess you have something lose in your gearing. Could be in X or Y or Z but something is allowing your cutter to move off of desired path. One practice that I have done, especially in harder material is to do your cut in two steps. No need to make two separate tool path programs, just zero your bit and then raise up maybe .02" and rezero, run the toolpath, then reset to true Z zero and rerun. Now your basically just cutting a small .02" of material with practically no tool deflection. Try it and see?

  3. #3
    Join Date
    Aug 2011
    Location
    Wilkesboro, NC
    Posts
    88

    Default

    One possibility is that your bit isn't truly 120 degrees or 90 degrees. That would cause over-cutting in the corners like you see on the body of the "I". You can test out cutting some sample shapes, with differing tool geometry. In your tool library, set your bit at 89.4 degrees and create a toolpath. Then repeat at 89.6, 89.8, 90.2, 90.4, 90.6 and see if any of those look better.

    I don't know if that is the solution to your problem, but it has worked for me in the past. My 90 degree bit was closer to 90.4.

    If you want to see an exaggerated version of this problem run you 120 degree toolpath with a 90 degree bit.

  4. #4
    Join Date
    Jan 2019
    Posts
    5

    Default

    Thanks for the suggestions. I just checked my my bits with a decent protractor. The 120 deg appears to be ~119 deg and the 90 deg looks like 87 deg which is quite a lot. My protractor could be out as well but this shows me there is probably a degree issue. I will try the cut test with the bits since that seems like a better way to hone in on the real angle. I am using the Amana insert V-Bits.

    I will also snug all my stepper motors in again to make sure everything is good.

    Cory

  5. #5
    Join Date
    Jan 2008
    Location
    Hobby-Tronics, Chiloquin Oregon
    Posts
    1,313

    Default

    You might also want to check to see if the collet is clean. Any debris in the fingers will allow the bit to be a little off and or move while cutting. Russ
    AKA: Da Train Guy

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