CNC 6040 - weak 4th axis


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Thread: CNC 6040 - weak 4th axis

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    Question CNC 6040 - weak 4th axis

    Did anyone else experience the 4th axis on the YOOCNC/carving-cnc 6040 to be very weak?
    The stepper is much smaller then on the other 3 axis, wich is fine (given it's limited travel distance and thus required speeds).
    But it is hardly geared down at all by this tiny belt.
    Even the slightest mechanical resistance between cutter and part sends the axis spinning backwards instead of holding it's position.

    Did any of you replace this axis or it's stepper?
    What could be a good choice?
    What settings do you have in MACH3 for this axis? (Maybe my settings are wrong. I had to change it a lot to make it do 360=360° instead of 360=multiple comlete turns.)

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    I bought one, but haven't used it yet - still coming to terms with using a flat bed.

    I am concerned about the lack of holding power - I must say I haven't really thought of a use for it yet - most of what I've seen appears to be rather naff decorative carvings (in my opinion at least!) although I do have the idea of using it to make light fitting bases from some kind of plastic, but if it can't be milled at a respectable rate without deflecting, the whole process could get a bit boring.



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    Question is: gearbox or stronger stepper motor.
    What size of stepper can the line driver card handle?
    I asked carving-cnc for the settings to use in MACH3 (they supplied only settings fox X,Y,Z but not A).

    RusselK: Did you get any settings to enter for the A axis into MACH3?
    What values are others using?(steps per degree, velocity, acceleration, step pulse, dir pulse, ...)
    obviously the XYZ-values cannot just be copied since moving the A-axis by 360 must be 1 full turn.

    Last edited by MarcusWolschon; 05-06-2013 at 01:48 PM.


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    I just got an answer from China (within minutes!!!) with the settings:

    steps per degree: 13.33
    velocity in degree per minute: 500
    acelleration in degree per second^2: 100
    step pulse: 3 (X,Y and Z have 10 here)
    dir pulse: 1 (X,Y and Z have 3 here)



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    I hooked up my 4th axis today just to see what Marcus was on about - I have to agree, it has bugger-all holding power. While I haven't actually tried using it to mill anything, I can't imagine it being of much use for anything but balsa wood or foam.

    Also, those velocity and acceleration figures seem ridiculously slow.

    I think if I am ever to use it, I'll need to replace the stepper with a bigger one, and perhaps replace the driver board, as it's much smaller than the ones for the other 3 axes, and maybe consider changing the pulleys to increase the mechanical advantage.



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    I'm having a hard time finding a planetary gearbox for that small NEMA23 stepper.
    They are also too long (stepper is 41mm deep, at >=63mm it would collide with larger mounted parts)
    Any idea what else to do?



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    I guess any power/torque increase is going to result in the stepper sticking out more. One option might be to extend the mounting plate so the stepper is further away.



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    And a larger stepper would probably require a new driver card.
    How much of a stepper can the driver card handle?
    Maybe we could do something to replace the belt?
    2 gears milled out of aluminum stock will probably not gear down enough.
    It's not thick enough to add holes for 2x 608 ball bearing supporting an additional axis, so we can use 4 gears.
    Maybe an L shaped motor holder and a worm-drive could work.
    Would replacing the 24V with a 48V power supply change torque?
    (I already gave that water pump it's own power supply as it's electrically extremely noisy and is the cause of lost steps.)



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    Question microstepping?

    Could it be that microstepping is active in the driver?
    How does it need to be jumpered to not use microstepping and thus give us the full force?


    Edit:
    According to http://www.cnczone.com/forums/chines...ing_steps.html
    You have turn both DIP switches to OFF to disable microstepping.
    Of cause the steps/degree in MACH3 also needs to be changed to reflect the lower number steps now.
    I'll try this next weekend.

    Holding force vs. Microsteps:
    Microstepping: Myths and Realities - MICROMO
    Microsteps/full step Holding Torque/Microstep
    1 100.00%
    2 70.71%
    4 38.27%
    8 19.51%
    16 9.80%

    Last edited by MarcusWolschon; 05-14-2013 at 01:43 AM.


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    Disabling microtepping (DIP 1 and 2 off = down) means you nee to set
    steps per degree=26.664 (instead of 13.33).

    You can set speed to 1500 and higher without problems.
    Sadly this doesn't solve the problem.
    The axis is still terribly weak. I can turn and stop it easily with just 2 fingers.

    So doesn't anybody know options?
    Replacement steppers or planetary gears or a cheap new 4th axis that has more force?
    I can't be the only one with this problem!



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    Can I just replace the 1.8A NEMA 23 with any 3A 3Nm(425 oz inch) high torque ones?
    The driver card seems to be identical to the other axis that use 3A steppers.
    Do I have to be careful about any other values of the stepper?

    Since its longer I plan to test it mounted like the current one but finally mount it from the other side using 4 spacers (to new research have stepper body and part collide).



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    My 3Nm stepper arrived.
    Will give it a try on Thursday.



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CNC 6040 - weak 4th axis
CNC 6040 - weak 4th axis