Heavy Y bed best X Y jerk and acceleration settings



  • Hi , Doing the finishing touches to my very much over engineered CR-10s like machine , The Y axis is using a 450x450mm 6mm cast aluminium plate which is HEAVY , and doesn't like to be jerked about too fast or it screams in pain.
    I want to print at about 40mm/sec which is a nice multi material speed ( petg / pla ), With the setting below it is working o.k , but a little slow double what Cura says is the print time.
    Which should I increase and which should I keep low due to the bed mass ?

    M566 X400 Y400 Z12 E120 ; Set maximum instantaneous speed changes (mm/min)
    M203 X9000 Y9000 Z1000 E1200 ; Set maximum speeds (mm/min)
    M201 X250 Y250 Z150 E150 ; Set accelerations (mm/s^2)
    M906 X800 Y1200 Z800 E800 I30 ; Set motor currents (mA) and motor idle factor in per cent

    Thanks in advance Peter


  • administrators

    Your M201 X and Y accelerations are very low and will severely limit the actual speeds reached. Try increasing them.

    Large, heavy beds are better moved in the Z direction than in the Y direction - but you've probably already realised that.



  • Also, a big heavy bed moving Y will be better served with a big heavy motor. I note that your motor current is set to 1200mA. Can you increase it or is that the limit? (Generally 85% of rated current seems to be the advised setting). If the current is at the limit, try a bigger motor (say 2 Amp) set to 1700 or 1800 mA. Check here for advice on choosing steppers.



  • Large, heavy beds are better moved in the Z direction than in the Y direction

    As Roger whittaker once sang "If I know then , what I know now !!!!"

    Can you increase it or is that the limit?

    It is the biggest Nera17 ( high torque ) motor I can find , so I can increase the current if needed ?.



  • @peter247:

    It is the biggest Nera17 ( high torque ) motor I can find , so I can increase the current if needed ?.

    Yes, up to about 85% of the rated current but no more than the Duet maximum limit which, the last time I looked was 2 Amps. For info, I throw around a very print head (about 4 kg) using motors rated at 2 amps which I run at 1800mA. Acceleration set to 1000 with instantaneous speed chnage set to 600 ad it will go higher.

    BTW , my bed is 10mm thick aluminium 400 x 400 with 6mm glass on top and insulation underneath but this only moves in Z. 🙂

    Another option if upping the motor currents doesn't do the trick is to use gearing. A small pulley on the motor driving a larger one on the bed. For example, a 20 tooth pulley driving 40 tooth pulley will give you twice the torque. You'd need to double the steps per mm of course but that's safe to do as you are nowhere near the limits of pulse generation frequency.

    HTH



  • Hi , I made a macro just to see how it goes :-

    M566 X600 Y600 Z12 E120 ; Set maximum instantaneous speed changes (mm/min)
    M203 X9000 Y9000 Z1000 E1200 ; Set maximum speeds (mm/min)
    M201 X500 Y500 Z150 E150 ; Set accelerations (mm/s^2)
    M906 X800 Y1800 Z800 E800 I30 ; Set motor currents (mA) and motor idle factor in per cent

    Cant see any bad results from the change and it look to be keeping to Curas time table which is 2 hours from 3 hours before a .2mm benchy .


  • administrators

    I suggest for now you keep the XY jerk low and just increase the XY acceleration.



  • I have a decently large bed too in an "i3" configuration, 6mm cast aluminium with 20 alloy resistors screwed to the bottom. So it's rather weighty. I got around this problem by running another motor and belt system (nema17). I almost went with a nema23 but it's cheaper to just pop on another 17. My jerk is 900 and Accel is 2000. I get more ringing from my X axis due to the long belt from being corexz



  • 6mm cast aluminium with 20 alloy resistors screwed to the bottom. So it's rather weighty.

    oh yes , when I received the bed my first thought "this is heavy I should have gone with 4mm" ?

    I think I should be alright with a single high torque motor , but I think the 1800ma is a little high because it getting a little too hoooot for my liking .



  • Hi Peter247,
    When you print round shape something that is 2 or 3 mm diameter, if circularity is good probably your maximum instantaneous speed changes (M566) value is right, but if not you should decrease the value.



  • @peter247:

    I think I should be alright with a single high torque motor , but I think the 1800ma is a little high because it getting a little too hoooot for my liking .

    It's quite normal for stepper motors to run hot (or hooot 🙂 ) They are usually rated at about 80 deg C. Having said that, if you can still get the desired acceleration with a lower motor current, then there is no harm in it.



  • It could be a good idea to get some guidelines concerning this.
    I'm currently playing around with the same setting. Running a Prusa style printer with an aluminum 4.75mm Y-carriage and a 330x300x6mm cast aluminum bed. I'm using a 48mm nema17 rated at 1600ma max with a 20t pulley. When i figure out some decent settings i'll share them along with the weight of my components.



  • I`ve found that these figures look to be on the safe , but reliable side.

    M566 X600 Y600 Z12 E120 ; Set maximum instantaneous speed changes (mm/min)
    M203 X9000 Y9000 Z1000 E1200 ; Set maximum speeds (mm/min)
    M201 X1000 Y1000 Z150 E150 ; Set accelerations (mm/s^2)

    I`ve tried a print at 80mm x 300% where the print bed was a blur and could not see any difference from printing it slowly.


 

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