X and Y surging / hesitant / pulsing while returning from homing



  • This is my 2nd Duet build. This first one was more of a plug and play deal where this was more of a ground up, sort of... I am using a Creailty CR10S Pro from but changed all the steppers besides the dual Z's, changed the belts to Gates, installed the AC powered 1100 watt heated bed from E3D and using a direct drive setup via Bondtech>E3D V6.

    For the most part everything is working fine, but when returning from homeall all the steppers hesitate and its almost like they're surging. So, I hit homeall and it goes to all the endstops and then the IR sensor travels to the center of the bed; Z lowers to home all without issue, but like I said... while returning from the center of the bed X and Y have a few moments where they almost come to a complete stop ( but never do ) and then continue only to do it again and again. I'm sure Z would be doing the same thing if it had to travel more than the 5mm that it does. I have tried a few things like adjust speeds and power current but nothing seems to improve this issue.

    Any info, tips and/or tricks would be greatly appretiated. Thanking you in advance

    I have included my config.g and homeall.g files

    1_1551019819456_homeall.g 0_1551019819456_config.g


  • administrators

    I don't see anything wrong with your config.g files, except for your rather unusual combination of two M208 commands. You set all the minima in the first one, then override the X and Y minima (but not the Z minimum) in the second one.

    One possibility is that the VIN power is dropping below 9.5V when you move the motors. What PSU are you using? Try running M122 after the problem occurs and look for "under voltage events" in the report.



  • @excelon IMO your instantaneous speed change (jerk) of 10mm/min is crazy low and accelerations of 90mm/sec^2 aren't much better unless your gantry weighs 20Kgs or so ☺ . Try setting both to something like 1,000.



  • @dc42 said in X and Y surging / hesitant / pulsing while returning from homing:

    I don't see anything wrong with your config.g files, except for your rather unusual combination of two M208 commands. You set all the minima in the first one, then override the X and Y minima (but not the Z minimum) in the second one.

    One possibility is that the VIN power is dropping below 9.5V when you move the motors. What PSU are you using? Try running M122 after the problem occurs and look for "under voltage events" in the report.

    Thank you for the reply @dc42

    I am running a Meanwell 24v 500watt PS. Pretty sure it's the RSP 24 500 but I can confirm if your truly think that's an issues. I will adj the dual M208 commands and also check the status of the M122 command after I "homeall".



  • @deckingman said in X and Y surging / hesitant / pulsing while returning from homing:

    @excelon IMO your instantaneous speed change (jerk) of 10mm/min is crazy low and accelerations of 90mm/sec^2 aren't much better unless your gantry weighs 20Kgs or so ☺ . Try setting both to something like 1,000.

    @dpeckingman deckthank you as well for your input. Although, I didn't try 1000 for either i did try to increase both of those values because I had downloaded and printed a modified hotend with dual fans that were kind of loose and for that reason I had to lower the " jerk" value and then have come like the smoothness of the lower values. With that being said I did experience the hesitation from TOO LOW of the " jerk" value, but this is not the case, but I am willing to trying the 1000 value for both to see if it helps it for sure. I'm not opposed to trying anything if its recommended.

    Thanks again!
    Eric



  • @excelon Well your description was that the gantry almost comes to a complete stop at the end of a move. What happens is that at the end of a move, the gantry will decelerate down to the "jerk" speed before starting the next move. So your very low "jerk" setting of 10mm/minute combined with your very low acceleration setting would produce the behaviour that you are seeing.



  • I tried values for 1000 for both instant and jerk speed and it does the same thing only faster. Any other idea's?



  • It might help to see a video of it in action.

    Does the motion feel smooth if you disconnect the motor wires and move the carriage by hand?

    I suspect binding or maybe a loose grub screw on a pulley.



  • @phaedrux said in X and Y surging / hesitant / pulsing while returning from homing:

    It might help to see a video of it in action.

    Does the motion feel smooth if you disconnect the motor wires and move the carriage by hand?

    I suspect binding or maybe a loose grub screw on a pulley.

    That's what I thought also. I removed the whole bed and cleaned everything and re adj the tension.... same. I will upload a video tomorrow when I get home from work.



  • Here are two videos of the hesitation. Thanks again!

    https://1drv.ms/f/s!AlKKGWMmM2j4xWSi3ZFVDpF6B_du



  • I can't really tell that it's hesitating.



  • @phaedrux said in X and Y surging / hesitant / pulsing while returning from homing:

    I can't really tell that it's hesitating.

    Can you turn up the volume and hear the steppers? I did watch it also and thought the same thing. It's minor but its still not supposed to do that, right?



  • Ok with the volume up loud I can hear that the motor sound isn't fluid when returning to the home position.

    What happens if you do a test print?

    Are your motor currents within range of 85% of rated max?



  • No, I believe those steppers are rated for 1.68amps (1680)and I have it set to 0.8 ( 800 ). Could that cause it?

    I lowered the amps on everything because the steppers are too loud when @ rated amps



  • Do you have the spec sheet for the motors?

    Well we don't know whether the hesitation sound actually has any negative effect on printing. It'll be a balance between sound and power.



  • @phaedrux

    All the stepper motors are from E3D. Here is the link to the steppers.

    https://e3d-online.com/motors-compact-but-powerful-motor

    I do have to say that the pulsing and hesitation is getting worse. Now, instead of the steppers pausing once or twice while returning from home its doing it about every 15mm, or so... Could I have a bad board?



  • @dc42 and @Phaedrux

    So, I wanted to change out the Duet 2 wifi board to see if I had a faulty board so I removed the one from the Ender 3 that hasn't been turned on in months.

    Verdict? The steppers DID NOT jerk or hesitate while returning from homing, but as soon as I started a print it DID. Long story short ( I'll cut out how exactly I found this ) the steppers only jerk/hesitate when the mesh map is loaded and active.

    WHY?



  • the steppers only jerk/hesitate when the mesh map is loaded and active.

    WHY?

    Jerk set too low.

    https://duet3d.dozuki.com/Wiki/Using_mesh_bed_compensation#Section_Troubleshooting

    If you get jerky movements when the head moves across the bed at speed with mesh bed levelling enabled, but not with it disabled, this indicates that your Z jerk setting is too low for the travel speed you are using and the amount of compensation needed. Increase the Z parameter in the M566 command in config.g, or use a lower travel speed.



  • @phaedrux

    @excelon said in X and Y surging / hesitant / pulsing while returning from homing:

    @dc42 and @Phaedrux

    So, I wanted to change out the Duet 2 wifi board to see if I had a faulty board so I removed the one from the Ender 3 that hasn't been turned on in months.

    Verdict? The steppers DID NOT jerk or hesitate while returning from homing, but as soon as I started a print it DID. Long story short ( I'll cut out how exactly I found this ) the steppers only jerk/hesitate when the mesh map is loaded and active.

    WHY?

    Ok.... for 'Z'... I don't think I changed the Z axis. Only X and Y since though were the only ones giving me issues. Let me try this! Thank you



  • I have a very slow Z axis with a heavy bed and I use a jerk and acceleration value of 60 for each. Seems to work out ok.


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