Bit grabbing? Cuts destroyed

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This topic contains 6 replies, has 3 voices, and was last updated by Profile photo of Ryan Ryan 3 weeks ago.

Viewing 7 posts - 1 through 7 (of 7 total)
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  • #35059
    Profile photo of Bryan
    Bryan
    Participant

    Any hints as to why this is happening? I’ve had this happen a few times on both the X and Y axis. It will be humming along smoothly and then all of a sudden its like it catches and gouges the piece. I’m running the Dewalt 660 with a 1/4″ 2 flute upcut bit. 1.5mm cut depth and 10mm/s. Its pretty slow. The piece is 18mm thick plywood and the gouge happens at about 6-10mm depth. The bit has over 20mm on the cutting edge. The gantry seems tight without any play. Bearings all on the conduit. Anyone else experience this and come up with a solution? Its a cheaper bit I picked up off Amazon but it seems sharp.

    #35061
    Profile photo of Ryan
    Ryan
    Keymaster

    How about a picture of the whole machine, how long is the z axis, how you have the bit in the collet. What is you spindle. Do you have an 1/8 bit to try, Faster and much much less torque while cutting.

    Is you “spindle” perpendicular?

    #35064
    Profile photo of Dalton Porter
    Dalton Porter
    Participant

    I’ve had something similar happen because the friction from the dewalt power cord added just enough torque (when the bit was deep) to cause the bit to briefly become un-perpendicular and go nuts. Make sure there is nothing causing a torque on the top of your z-axis.

    #35065
    Profile photo of Bryan
    Bryan
    Participant

    I built this machine to be 18x36x4. Z is square to the table. The power cable for the router is hanging off the side but zip tied to the stepper with enough slack… however, i never really checked for drag… Might be on to something there. Thanks for that. I do have a number of 1/8” bits I can also try, though I’m not sure if they are long enough to cut through that thick of material. I took the quick change part off the router as its really annoying to change it like that.

    Thank you for the input! I love this machine​ and it works great other than this issue.

    #35081
    Profile photo of Ryan
    Ryan
    Keymaster

    Your belts are little loose. Probably the main issue.

    I have a “perpendicularity tester” on thingiverse. Even if your machine is good the mount can be a little off, it isn’t really an issue until you do deep cuts. Usually a carefully place piece of tape in the mount can straighten it up, worth the 10 minute print.

    #35132
    Profile photo of Bryan
    Bryan
    Participant

    Thanks for the reply! What is it you are seeing that makes you think the belts are loose? (hope that doesn’t come off as snarky… just wondering what it is you are seeing – read it in the tone of “hey buddy, what is it you are seeing because I’m ignorant” vs “just who do you think you are 2nd guessing my belt tightness, the nerve!”) When plucked they are down around A0 on a piano if I had to guess. I tried to make them roughly the same as whats on my 3D printer, figuring that works without issue so this should be the same. Maybe bad logic.

    I don’t have any issues at all with shallow cuts, so you are probably correct. I actually already printed that tester a while back but haven’t actually used it. I will be giving it a try.

    • This reply was modified 3 weeks ago by Profile photo of Bryan Bryan.
    #35135
    Profile photo of Ryan
    Ryan
    Keymaster

    No problem, I should clarify but I kind of get into auto complete mode sometimes. Lots of emails and questions in a row usually so hopefully I don’t come off snarky in my replies!

    What I am seeing is the shape of your zip ties. Usually at first they will have a bit of a roundness to them but after a day or two if you add another click or two they will be very straight with hard corners. And to add to that yours are a bit long so it makes it a little harder to get just right. I sinch one right up to the block as tight as I can get it and make the belt just long enough to have 1/2″ or so on the tensioning end. These are things I am still learning as well but doing it that way makes it a lot easier to only deal with one end.

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