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My router cuts out of place

Discussion in 'CNC Mills/Routers' started by El Oso, Nov 8, 2020.

  1. El Oso

    El Oso New
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    Hello!
    Recently I finished building my router, it uses a Dremel 3000, Nema 17 motors, Arduino UNO, and A4988 drivers with a cooling fan. I am making my cutting programs with Vectric and run them with GRBL.

    The issue I am observing, is that after a couple of cuts, my router starts cutting out of place, for example, it cuts some holes in the right place, moves to the next position and the place where it plunges is out of place i.e the final part is not correct.

    I have been playing a while with accelerations (my leadscrews advance 2mm per rev, and acceleration is currently at 18 mm/s^2) trying to fine tune the machine but I havent reached the sweet spot yet, any siggestions are highly appreciated.
     
  2. Giarc

    Giarc OpenBuilds Team
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    Are those A4988 drivers overheating and loosing steps? Those are pretty much 3D printer drivers.
     
    #2 Giarc, Nov 9, 2020
    Last edited: Nov 9, 2020
    Peter Van Der Walt likes this.
  3. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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  4. El Oso

    El Oso New
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    Hello Giarc, thank you for your reply.

    Due to the fan that is continuously blowing over the drivers and shield, they don´t get hot. I don´t think that the drivers are loosing steps, the contours look exactley the way they should, the only issue is that they are not in the right place. For example, I tried to cut a smiley face. The cutting program was set to cut the eyes and smile first and the face contour afterwards. The eyes and smile positions match with each other and cut depth is ok, however the face´s circle is off.

    Do you think there could be another issue besides a bad driver? I was thinking maybe acceleration or another parameter could be causing the router to go crazy.

    Thanks.
     
  5. Giarc

    Giarc OpenBuilds Team
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    What software are you using to create your tool paths? What do you mean by:
    Do you have a picture?
     
  6. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Between cuts, are fast rapid moves. Useless little A4988s skip when asked to move fast because they dont give enough current for accelerating to seek move. Dial down Max Feedrate settings in Grbl settings to suit the max speed your machine can actually move without stalling - probably under 2000mm/min with A4988s
     
  7. El Oso

    El Oso New
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    Thanks for the info Peter. Hopefully I will improve my HW when I have some $$, in the meantime i will try what you suggest.
     
  8. El Oso

    El Oso New
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    Hello, here is an example. The hole should be centered in the oval contour and it is moved. The cutting program was made with Vectric Aspire. First it makes the hole and then it moves to cut the outer oval contour.
     

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  9. Giarc

    Giarc OpenBuilds Team
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    Does it look ok when you do "Preview tool paths"?
     
  10. El Oso

    El Oso New
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    Hello.

    Yes, the simulation in vectric looks ok, it just behaves strange when I run the cut in the machine.
     
  11. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Did you adjust your max feedrate yet. Those drivers cannot handle fast moves - seek moves between sections of the cut happen at the speed set in Grbl settings > max feedrate

    If you did, go down some more.


    Or just get a BlackBox :) all that wasted stock (and frustration) will soon add up to more than the cost of a BlackBox
     
    David the swarfer likes this.

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