Corexy acceleration questions



  • I have a question about tuning my corexy printer.

    I used the online configurator to make my base files. Got everything set and tunned except the accelerations. Can someone tell me why it set the y value soo low compared to the x value on the m201 command?

    M566 X900 Y900 Z12 E120 ; Set maximum instantaneous speed changes (mm/min)
    M203 X10000 Y10000 Z1800 E2200 ; Set maximum speeds (mm/min)
    M201 X500 Y20 Z250 E250 ; Set accelerations (mm/s^2)
    M906 X800 Y800 Z800 E750 I30 ; Set motor currents (mA) and motor idle factor in per cent
    M84 S30 ; Set idle timeout

    Can i change the y to be the same as x?

    It prints fine just want to tune it to bring out the maximum potential of the printer.



  • Yes, X and Y should be configured the same, it makes no sense in coreXY mode.


  • administrators

    Y acceleration can be made a little lower than X, because there is more mass when moving the gantry than when moving just the X carriage. But it should be much higher than 20. Try 500 like the X axis for now. When you have the machine printing, you can probably increase both X and Y.



  • @whosrdaddy:

    Yes, X and Y should be configured the same, it makes no sense in coreXY mode.

    It does make a bit of sense. In X you are only moving the print head but in Y, you are moving the print head plus the rails and carriages on which it sits, so the mass in Y is considerably more than the mass in X.



  • @rar26. For info, I have a big and heavy CoreXY (actually it's a dual CoreXY so for homing it becomes CoreXYUV). Each gantry has a mass in Y of about 2kgs. For printing I use 500 mm/sec^2 and for non print moves I use 1,000 so you should be fine with those sort of values (unless your moving mass is greater than 2kgs).
    HTH

    Edit. There is a caveat to that - I am using bigger motors with the current set to 1800 mA. However, 500mm\sec^2 should still be fine if you have a "normal" print head and not the mass that I have to throw around.



  • So, for a CoreXY, X and Y accelerations refer to axes, and not to motors?



  • @fma:

    So, for a CoreXY, X and Y accelerations refer to axes, and not to motors?

    Yes. Because both motors contribute to movement. For pure X, the motors turn in the same direction and for pure Y they turn in opposite directions. So if acceleration was applied to motors rather than axes, one would accelerate faster than the other leading to angular movement rather than linear. Actually the worse case for acceleration is not pure Y moves but 45 degree moves because in this case, only one motor is employed and the other is stationary. Technically, we should refer to the motors on a CoreXY as Alpha and Beta rather than X and Y.



  • Yes, that's why I asked: X/Y is confusing on CoreXY; would be better using A/B for motors names, as for Delta.



  • @fma:

    Yes, that's why I asked: X/Y is confusing on CoreXY; would be better using A/B for motors names, as for Delta.

    Exactly so. The problem is, the Duet boards and I suspect every other board are labelled with X and Y motor connections in order to make them "universal". Likewise the firmware, so sometimes we just have to do a bit of mental algebra along the lines of X=A and Y=B 🙂


  • administrators

    On the next generation Duets I propose to number the motor outputs 1, 2, 3, 4… instead of X, Y, Z, E0 and so on.



  • thanks guys for the reply's just changed them to match and we will see what happens.


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