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Ox CNC can't cut small circles

Discussion in 'CNC Mills/Routers' started by Kalevra1102, Feb 29, 2016.

  1. Kalevra1102

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    I recently build my first CNC router, the OX kit from SMW3D. So far everything is going well except for the fact that I can't seem to cut circles. As you can see from the picture the circles aren't quite round. I am using HSM inventor with the TinyG post processor so i don't think it is a software problem.

    I have cut other parts with rounded corners and the corners seems to be fine. From what I can tell the flat spots are parallel with the x and y axis. Has any one else had this problem? Can any one recommend a solution.

    Thanks
     

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  2. Bad Sequel

    Bad Sequel Veteran
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    I had problems with circles on my XCarve a while back and found a couple issues to fix. They might be relevant for you also.

    • The tiny screws holding the pulleys to the motor shafts can cause slip if not tightened enough.
    • Belt tension
    • Distance/time unit travel on the axis. if using GRBL that would be params $100 and $101
     
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  3. JustinTime

    JustinTime Master
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    Also check for backlash. Even if everything that Bad Sequel said it OK, you can still have backlash.
     
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  4. Chillimonster

    Chillimonster Journeyman
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    Are you running single or dual belts on each stepper?
     
  5. Kalevra1102

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    Thanks Bad Sequel, I will look at this as soon as I get a chance. I am out of town for a week now but I will post the results as soon as i get back. Appreciate the help.
     
  6. Kalevra1102

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    I am hoping it is not backlash. I was cutting MDF with a high spindle speed, brand new end mill and low feed rate. This machine is rumored to be able to cut aluminium, albeit with very small passes and slow feed rate, so I would hope that it can cut through 1mm of MDF
     
  7. Kalevra1102

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    I am not but I just looked it up and will defenately be changing my set up. Does any one know how much of an improvement this will be?
     
  8. Chillimonster

    Chillimonster Journeyman
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    Unsure of improvement, but i went straight to dual belts as it was easier to order the extra when i ordered my machine.

    In theory it should make a huge difference as it acts as a rack and pinion and the only 'streatchable' part of the belt is the 40-50mm from the last wheel to the pulley wheel
     
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  9. Kalevra1102

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    Thanks Chillimonster, I will definitely be looking into this.
     
  10. Bad Sequel

    Bad Sequel Veteran
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    Dual belts? How that works?
    You run a longer belt in a loop along an axis and have a couple more pulleys?
     
  11. Kalevra1102

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    Stainless OX | OpenBuilds

    It is explained pretty well in this build.
     
  12. Bad Sequel

    Bad Sequel Veteran
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    Thanx man! Much appreciated.
     
  13. David the swarfer

    David the swarfer OpenBuilds Team
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    the dual belts still need to be at the same tension!

    and, feedrates. 'slow' does not help really. the tool just rubs, creating heat, until it has flexed enough to exert enough pressure to cut, then it cuts too deep. rather calculate the correct feed speed and adjust the depth to what your machine can handle.
    I explained it at length just the other day (-:
    What cutter? | OpenBuilds
     
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