Cutter jumping/bouncing?

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  • #10802

    Just got my KNK Force a few days ago and so far I really like it. I tried cutting some very thin Lexan (.03″) and am seeing some strange behavior. I recorded it in this video. The weird action starts at about 1:04.

    I’m using the following settings: Blue blade (brand new), BT: 3, CD: 10, CS: 10, US: 20, PS: 30, LS: 40

    Here’s the strange thing. It seems like it can cut through the material just fine, even at a higher cutting depth and cutting speed, until it moves at a particular angle. If you look at the video you can see the behavior is very consistent across a half dozen attempts with various settings. It always fails at the last point of the star.

    I also tried a different file (just the letter “A”) and saw the same thing. It works fine until the blade moves in that one direction.

    Any advice as to what the problem could be or what I could do differently?


    For anyone encountering similar behavior, I lowered my blade tension to 2 and that seems to have fixed the issue.


    One more update. Reducing the BT to 2 worked until I got deeper in the material and then it started binding again.

    Reducing it closer to 1.5 seems to have eliminated the binding but now it doesn’t apply enough force to cut through the material.

    Most recently, I’ve set the passes to 20, starting depth to 18, ending depth to 370, cutting speed to 10. It still binds when going in a particular direction.

    Does this mean it’s simply not possible to cut through .03″ lexan, or are there other things I could try?


    Darrel Farris

    Cutting polycarbonate is not a recommended task to perform with a blade.  The jumping and stuttering is the motor being unable to move the tool holder when the blade gets stuck the material.  Be wary of that when cutting anything as it has potential to damage your machine.

    Other users do this type of cutting with the rotary tool and a bit appropriate for acrylic/plastics.  Generally speaking, standard acrylics cut more readily than polycarbonate/Lexan.

    A good litmus test for blade cutting is “Could I do this with a steady hand and an X-Acto knife?”

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