Jerk/accel settings not working for me

deckingman

I'm leaning towards the impression that there is some underlying problem here that in itself is nothing to do with jerk and acceleration settings but more to do with the fact that setting them really low helps to mask this underlying problem. Thinking it through we know that the force to move an object = mass x acceleration. So logic dictates that by reducing the acceleration we reduce the force required. Therefore it would seem logical to deduce that one or more motors are not capable of supplying the torque required to accelerate the mass at anything like a reasonable rate.

Things to check off the top of my head.

I notice that the motor currents are set to 750 mA which would imply that they are maybe 1 amp motors? Are they adequate for the job - check the spec. Also, does it help if you increase the current to say 90% of the rated current.

Is the power supply adequate? What is lowest voltage that you see when printing?

Are all the axis is free of any binding?

Edit. Try running M122 at the end of a print and check for missed steps or under voltage events.

Ret

I do appreciate all of your help, very much so! Thank you!

I can confirm mechanically everything is okay. Swapped out the for the old board just to verify once again. Everything works near flawlessly with the rambo running marlin. I upgraded so I could have WiFi, quieter printer, and a nice display.

These are the default settings sent with the printer and they work great on the rambo with marlin and repetier. I have not had to change the jerk much but have lowered accel when i was printing with my old board running marlin.
Jerk X240 Y240 Z24 E60
Accel X3000 Y3000 Z30 E2000

After reading what was in M122, there were no errors/missed steps. The steppers were defined 0.75a in marlin firmware but I tried 0.85a and 1a as my steppers are 1a, There was no noticeable difference with any of those current changes. You'd think that the accel and jerk settings would all be somewhat the same among firmware, to a degree. Maybe marlin and repetier have more optimized jerk/accel code for 3D printing.

This is all pretty frustrating.

deckingman

I can't comment on what Marlin does as I have no experience if using it. One things that stands out with the settings you listed above is that the extruder jerk is very low. More normal settings would be in the order of 600. Try that.

Ret

I have indeed tried that as someone else recommended that, no difference. 60 was also set by the manufacturer, and it worked great prior.

dc42

Please post the GCode of the circles or ovals etc. that you are trying to print that print jerkily. We've seen issues before with slicers generating tiny non-extruding moves between extruding moves. S3D still does that when printing skirts, but thankfully not the rest of the time.

Extruder jerk of 60 is very low, and if you use pressure advance you will certainly need a lot more. I suggest at least 600.

Ret

Sorry for taking a bit to reply, I had to put my old board on for a bit to finish a project. 60 does seem low after looking at everyone else's, but it worked PERFECT on marlin which really throws me off that this firmware is so different when it comes to the jerk and accel. I have attempted it with 2 slicers, S3D and Idea maker, both same jerky motion, nothing is smooth. Here is my gcode though, feel free to check it out!

https://drive.google.com/file/d/1dwXWh0slnOdZQeG-oGh5iy_89H0ujWp4/view?usp=sharing

dc42

That's some of the worst GCode I have ever seen. It includes lots of really tiny segments, which means very low extrusion distances, but it's only giving the extrusion distance to 4 decimal places when it needs at least 5. So the extrusion rate is varying erratically.

I have seen S3D do this before when generating the skirt, but not for the actual print as it is here.

For Marlin to be printing this without jerking, it must be ignoring the extruder jerk limit completely.

You might get reasonable results if you set the extruder jerk limit very high in M566. But IMO a better solution is to use a slicer that generates better GCode.

Ret

I do appreciate your help with this.

I'm not seeing any "really tiny segments" that you wouldn't find in other sliced models using a different slicers. The gcode produced by ideamaker and cura look very similar to the one produced by S3D. The model has been exported in an average STL resolution and an extremely high 100MB version, which shows no difference either. Do keep in mind, its not only with this one item, its with all of my prints I have attempted. I've yet to produce a part that I would consider acceptable, which really bugs me since this has never been an issues for me. I love the screen, internet interface and the how quiet my printer is now, I'd love to switch all of my printers over to this system, but i need to address this issue first. Do you recommend a slicer that's better than Cura, S3d, or ideamaker, that would prove a point here that its the slicer and not firmware?

I cranked the extruder jerk up to 6k, then to 60k, no difference with quality one bit from 60 and 600.

Thanks!

dc42

Last time I compared the outputs, Cura produced better GCode than S3D.

Can you share the STL model you are starting from?

Ret

Since the part I've been printing is a customers, I can't share the actual part. But, I will post a small section of it below(its the section that was featured in the gcode above). Last night, I tried the same model in cura, with the same results I was getting on S3D.

https://drive.google.com/file/d/16teyQzuT7mKSkqpj_Cpv5Gk7gJUY4pch/view?usp=sharing

Ret

After playing with it this last week, I think I will be switching back to the rambo board with Marlin shortly since the only fix I've found for this jerk issue is printing at half of my normal speed which really isn't acceptable to me.

I will probably check back in a few months to see if any firmware updates have fixed the issue.

Thank you for all your help guys! I am still up for suggestions if you guys have any. I'd like to use this board over the rambo since the hardware capabilities are far superior.

deckingman

@Ret,

1. Before you do that, could you try an earlier version of firmware - prior to 1.20 (say 1.19). The reason I suggest it is that there are similarities in the behaviour that you are seeing and something I saw back in January. It's in this very long thread which is mostly related to pressure advance behaviour with multiple extruders (mixing hot end). https://www.duet3d.com/forum/thread.php?id=1999&p=3. Unfortunately I went off on my travels and since then I haven't had chance to do much printing this year. I'm still on 1.20 RC "something" so things may have changed again. At that time, David had recently changed something in the firmware that I think was to do with pressure advance behaviour but the result was that I was getting jerky behaviour on arcs. My memory is a bit hazy but IIRC it seemed that the firmware had become more sensitive to gcode which produced varying segment sizes for arcs.

2, If you do go back to Rambo / Marlin, please report back if it fixes your problem. I'm sure David will "pull out all the stops" to implement a fix if it can be shown that another board/firmware does something better than Duet.

dc42

@Ret, please share the gcode that Cura generated, so that I can see whether it has the same issue as the S3D gcode.

Phaedrux

I sliced the model STL sample that was posted earlier in Slic3r PE and the extruder moves were to 5 decimal places. Without the full model it's hard to know what the orientation it is printed in, but to test it I rotated it so that the flat part of the circle is to the bed. I did a test print of the first few mm.

The part is very thin, and I suspect that S3D is trying to lay a line thinner than the nozzle diameter and is breaking it up into small sections of extruding and not extruding.

You can force Slic3r to do similar behavior by turning off detect thin walls, which merges the inner walls into a single gap fill move. Slic3r seems to handle it a lot better.

That's just a thought though.

Here is what Slic3r generated

https://www.dropbox.com/s/pigl8mxi9h50fnu/TL_CUT.gcode?dl=0

deckingman

@Phaedrux,

Are the segments lengths for each curve all more of less the same size? I've had issues with Slic3R (PE) where they are not. This seems to cause havoc with printing curves, especially if pressure advance is employed.

dc42

The main problem with the file that @deckingman refers to news that the ratio of extrusion amount to XY movement amount was varying wildly, especially for the very short segments.

Another issue that causes jerky movements is when S3D inserts tiny G0 moves (no extrusion) in between extruding moves. It seems to do this always when generating curves in the skirt, but so far I haven't seen it do it in the main part of the print.

Ret

Deckingman,
I will give an earlier version a shot within the next day or so, thank you!

dc42,
https://drive.google.com/file/d/1bpdNy6O7MxUwSIXr4ZoWXPekSAoUQRRx/view?usp=sharing
This isn’t an exact copy of the other model used in the gcode link I sent with s3d. It is the same part but started at a different position. I still am unclear what you mean by little segments, but to me, visually, the outer layers look similar, maybe slightly cleaner with Cura.

Phaedrux,
Those varying internal extrusion widths are how I set it up. The problem occurs on all parts of the print(outer layers, inner layers, and infill). The outer and inner layers are consistent, but the infill segments vary to fill the space since it’s a unique geometry.
–---------
I have attempted printing with pressure advance (0.01-0.3), with no real notable change in quality. I did however have to modify jerk settings as I went higher with the pressure advance, but I believe that’s as to be expected.

Ret

I went back to 1.19, no real significant changes between the item printed (same gcode) on 1.21. 1.19 seemed to stutter more, at least it looked like it. There’s nothing smooth about the movements as opposed to my previous marlin.

DC42, have you ever looked into the acceleration and jerk code in marlin? You also did mention the extrusion value needed to be 5 decimal, instead of 4. Is that just a preference or does it actually NEED to be 5 for your firmware? Of course 5 will be quite a bit more accurate, but it seemed to work just great with the other firmware I was running. Cura using 5 has no noticeable impact as opposed to S3D’s 4 in my experiments with the duet.

dc42

This is on my list to look at. I strongly suspect that Marlin doesn't do extruder jerk planning at all.

Shen

I don't know if this is related, but I sliced a model using S3D that runs very badly on my printer. However, the printer runs fine if I comment out every other line in the gcode during cornering.
My custom printer running 2.0 alpha 1 printer makes loud noise at corners.
https://youtu.be/ZIlCNwHtu50

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