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Cut depth is slightly off

Discussion in 'CNC Mills/Routers' started by Logan Blankenship, Apr 29, 2021.

  1. Logan Blankenship

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    Hey everyone,

    I'm working on making my first sign and noticed that my cut depths are slightly deeper than intended. I set my cut depth to be .0625" (1/16") which the machine does. Then it will go for a second pass at .1". I'm not sure why this is happening. It doesn't seem to be an "error" with the machine because it shows it's cutting at that depth on my interface controller. I'm just not sure why this is happening.

    I created my toolpaths and file using Fusion 360 and do have "multiple depths" selected but the max depth I have set is .0625".

    I'm wondering if I'm missing something on my file setup or not. However, any help diagnosing this would be appreciated. I've attached my file for reference.

    Machine: Lead 1515

    Thanks!
    Logan
     

    Attached Files:

  2. sharmstr

    sharmstr OpenBuilds Team
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    Maximum roughing step down doenst mean "this is as far as it will go". It means, "this is as far as it will go in a single pass". You have 0.0393701 in raw stock above the face of your sign. So in order to get to the bottom of the letters, its got to go .039... + .0635. That's your .1000. To fix this, go into your setup and change your Stop Top Offset to 0, then regenerate your code.
     
  3. Logan Blankenship

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    Thank you! I was aware what the max roughing step-down was but couldn't figure why it was taking that second pass past my desired depth. Looks like there was a default parameter set for the top offset like you mentioned. Lol

    So today I updated my file and code removing the top offset however I'm still off on the depth. The controller still reads properly but I can't seem to figure any other setting that would be causing it. For example I set a cut depth of 1/8th and I read just under 3/16ths with a micrometer. 20210430_125918.jpg
     
  4. sharmstr

    sharmstr OpenBuilds Team
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    Have you calibrated your motors steps/mm? If not, your cuts wont be accurate. If you're using OB Control, go into the wizards menu and calibrate each of your axis.
     
  5. Logan Blankenship

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    I have and did it again today to be safe. I'm still off slightly. When cutting at 1/8" I'm really getting 5/32".

    I tried calibrating by cutting a square and calculating my steps using theoretical and actual values along with lastly going through the wizards in the openbuilds control software.

    Any other thoughts?

    The only other thing I'm thinking that it may be is the plywood I'm testing on has some irregularities and is slightly higher in some spots?
     
  6. JustinTime

    JustinTime Journeyman
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    I don't know how you did you Z axis calibration but if you did it with a 1x2x3 block it may not be enough.
    Try calibrating the axis with a big a distance as possible. The bigger the distance the better the acuracy.
     
    Peter Van Der Walt likes this.
  7. Logan Blankenship

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    I used the method in this video () where I cut a 100mm x 100mm square with a 1/4" pocket on one corner. My X and Y are pretty dead on and even my Z didn't look very off on the calibration.

    I also tried using the wizards in the openbuilds control doing the default dimensions they set. 100mm x 100mm x 50mm
     
  8. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
    Staff Member Moderator Project Maker Builder Resident Builder

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    Defaults are small because some customers have MiniMills (; enter as big as you can
    Absolutely, unless you pay for the super premium stuff. Run a Surfacing job first to deck it off, then try again
     
    Logan Blankenship likes this.

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