Very slight systematic waves every about 2mm on the prints

luc

Tried loosening the whole spring of the dual drive extruder without getting any change.

Checked all rollers and pulleys and.....incredible!!!
I have never seen such a thing!!! Belt rubber or maybe dust stuck in the tooth recesses!!!
I can clean it but with the occasion I put two new pulleys.

Notepad

@luc This could be many things, and is generally referred to as VFAs (Vertical Fine Artifacts)
Whilst there is not much you can do about it as it could be a variety of issues, I have a few tips that might be able to help find out where the problem lies.

Belt tension, If the belts are too tight the tooth patten may show up in the printed surface
Motor accuracy. Motors have predefined "steps" which the microcontroller smoothes out. Try printing the part faster or slower, and see if that changes the surface regularity. If it does, then it means you might have a printing speed close to the motors resonant frequency
If speed doesn't fix it, then it might be a bearing, either the motion system or the extruder.

In general on a 20T belt pulley, I find printers have 2 resonant speed frequencies, 60-80mm/s or 100-130mm/s. Try to find out which one your motor doesn't like, and avoid those speeds.
You also want to loosen your belts as much as possible without compromising your accuracy or risk belt slippage. its VERY easy to overtighten your belts if you don't have measurement equipment.

o_lampe

@Notepad said in Very slight systematic waves every about 2mm on the prints:

you might have a printing speed close to the motors resonant frequency

Interesting stuff! In car gearboxes they often use gears with a prime number toothcount to avoid such stuff. There it's torque-curve related, which is similar to the stepper motor.

I wonder if the resonance frequencies would be an issue with 17 or 19 tooth pulleys?
I may resin-print some pulleys to test this theory.

luc

Cleaning the pulleys slightly improved that effect but did not solve it.
I am waiting for new pulleys that I will install along with a new belt but I don't think I am getting any improvement.

I tried printing with a higher speed without getting any change.

I have tried printing at 45° with no change.

I tried printing with a 0.3 layer instead of 0.2 and got no change.

I tried redoing the PID of the bed and found no change.

By now it has become a war....me against her!

Translated with DeepL.com (free version)

luc

@o_lampe
The engines I use on X and Y are these:
https://www.omc-stepperonline.com/it/nema-17-bipolare-0-9deg-46ncm-65-1oz-in-2a-2-8v-42x42x48mm-4-fili-lunghezza-d-cut-completa-17hm19-2004s1

o_lampe

@luc said in Very slight systematic waves every about 2mm on the prints:

I tried printing with a 0.3 layer instead of 0.2 and got no change.

This should at least change the distance between the lines?

Your motors are perfectly fine. What we discussed about resonance is a common thing among steppers.

luc

@o_lampe said in Very slight systematic waves every about 2mm on the prints:

@luc said in Very slight systematic waves every about 2mm on the prints:

I tried printing with a 0.3 layer instead of 0.2 and got no change.

This should at least change the distance between the lines?

Your motors are perfectly fine. What we discussed about resonance is a common thing among steppers.

No, almost nothing changes. Maybe very little for the better but the imprint of those vertical waves remains.

luc

@luc
To assess whether the motors are the cause, I might try setting a different current.
They are currently set at M906 1700.

Are you thinking of trying a print at 1800 or 1600 or less?

Notepad

@o_lampe OO very interesting, I never considered the difference between 19 20 and 21 tooth. Id say start with 21 tooth as bigger pulley = more grip

Notepad

@luc Less current normally means less vibration force. If it works, Try 1200 or 1400

luc

Hello everyone,
I put on the new pulleys (even though the old ones were just to be cleaned) and with the occasion also the new belt and I can't get rid of those vertical marks that seem to be spaced just under 2mm apart.

Does anyone have any ideas?
Thanks

3DPMicro

@luc since the 2mm spacing suggests its related to tooth pitch flip the belt so the teeth aren't engaged, tension to provide enough grip to execute a test print.

o_lampe

@Notepad In my theory, 20 teeth is the worst, since if syncs "perfectly" with the 200 steps/turn torque curve.
21 isn't a prime number, so I'd go for 19 or 23

luc

I was able to find a way to turn the belt temporarily just to make a print.

The cause is not the belt or even the pulleys.

I'm beginning to think it may be the motors:
https://www.omc-stepperonline.com/it/nema-17-bipolare-0-9deg-46ncm-65-1oz-in-2a-2-8v-42x42x48mm-4-fili-lunghezza-d-cut-completa-17hm19-2004s1

What are your thoughts on these motors?

droftarts

@luc The motors seem fine, but it might be an imbalance in how the coils have been wound. What hardware and firmware version are you running? Send M122 and post the response. Also please post your full config.g.

Ian

luc

@droftarts said in Very slight systematic waves every about 2mm on the prints:

@luc The motors seem fine, but it might be an imbalance in how the coils have been wound. What hardware and firmware version are you running? Send M122 and post the response. Also please post your full config.g.

Ian

Here is what is required
Thank you

config.g
M122.txt

droftarts

@luc I can't see anything obvious in your config or M122 that would be causing the issue. You could try using the latest 3.6.0-rc.2 firmware to see if it makes any difference, but I'd think the issue is either the motors as already discussed, or mechanical, ie a bad bearing on the belt run (if it affects all axes, look at the bearings not on the X carriage, as those don't move with Y axis movement). Overtightened belts can also cause issues. Finally, check that you haven't mixed up the belt and pulley types, ie running Gates GT2-2mm belts with 2GT pulleys, as the tooth profile is very slightly different.

Ian

luc

@droftarts
I don't think it could be the firmware but I'll try it last.

All pulleys and bearings looked good but your point about doing it on all faces I could I had to check to rule out the fixed bearings not on X axis was very helpful in fact, since I had them new, I decided to change both bearings and pulleys.

I made a test print afterwards and did not solve it so I think it is useless to disassemble the other 4 X-axis bearings.

I only have one new motor in reserve. I don't know if it is worth doing a test by changing only one motor or is it better to do both together.

Edit
For GT2 or 2GT: With both old motor pulleys and belt and new ones I tried to see conme copied one over the other and I don't seem to have any doubts about that. They look okay to me.

Edit2:
Changed the left engine: Nothing....all the same as before!

luc

hello, it seems that my problem is identified with the term VFA “Vertical Fine Artifact” and it seems strange to me that from what you read around there is no solution.

What do you guys think about this?

https://ellis3dp.com/Print-Tuning-Guide/articles/troubleshooting/vfas.html

https://www.youtube.com/watch?app=desktop&v=-et5eMyLlUs

https://www.google.com/search? q=VFAs+%28Vertical+Fine+Artifacts&client=firefox-b-d&sca_esv=cc91aa7b516a412e&ei=1egHaKX7EZCN9u8PlJz78AQ&ved=0ahUKEwjluYKEq- yMAxWQhv0HHRTOHk4Q4dUDCBE&uact=5&oq=VFAs+%28Vertical+Fine+Artifacts&gs_lp=Egxnd3Mtd2l6LXNlcnAiHVZGQXMgKFZlcnRpY2FsIEZpbmUgQXJ0aWZhY3RzMgUQIRigAUiMCVAAWABwAHgAkAEAmAGJAaABiQGqAQMwLjG4AQPIAQD4AQL4AQGYAgGgAowBmAMAkgcDMC4xoAe0AbIHAzAuMbgHjAE&sclient=gws- wiz-serp

I have TL smoother that I used on an old printer. Can I try them on the duet 2 wifi or do I risk damaging the board?

droftarts

@luc said in Very slight systematic waves every about 2mm on the prints:

https://ellis3dp.com/Print-Tuning-Guide/articles/troubleshooting/vfas.html

This seems like a sensible page. It focusses particularly on belt/pulley/idler teeth for ~2mm spacing VFAs. I think this is the most likely cause of your ringing, mainly because the VFAs from a 0.9 degree motor doing 160 steps per mm like yours would be much closer together. VFAs from motors usually show up between one full step and the next. On a 1.8 degree motor 80 microsteps per mm, assuming x16 microstepping, the VFAs are 0.2mm apart. On a 0.9 degree motor like yours, they'd be 0.1mm apart, which is why they are less noticeable.

I don't know enough about the Prorifi3D motors to know if they are any good. I know Prusa spent a lot of time improving their stepper motors, and switched from 1.8 degree motors to 0.9, but still have VFA issues, even on the new Core One. Prusa introduced Phase Stepping on the Prusa XL, see https://blog.prusa3d.com/phase-stepping-how-we-busted-vibrations-and-improved-print-quality-on-the-xl-printer-with-just-a-firmware-update_94793/, but that only works with certain TMC drivers; 2240 on the Prusa XL, and 2160/5160 like on the Duet 3 6HC (though Duet have only partly enabled Phase Stepping so far).

TL smoothers were made to address a specific design flaw in DRV8825 drivers, and helped a little for old A4998 drivers. As far as I know, they won't make any difference on TMC drivers.

If you really want to go down the rabbit hole of looking at the stepper driver and motor, you could look at the developments in Klipper firmware. See
https://github.com/MakerBogans/docs/wiki/TMC-Driver-Tuning
https://github.com/andrewmcgr/klipper_tmc_autotune/tree/main

The idea here is that the default settings of the stepper driver may not be ideal for your motor, and that you can change the stepper driver settings to better match your motor. This should work for the TMC2660 drivers on the Duet 2, but hasn't been tested. I don't actually know of anyone who has tried!

Fortunately we don't have to install Klipper to run this; @Falcounet created an online calculator here, and @jay_s_uk made a macro that can run on a Duet, on the RRF Discord here

Using the values for your motor from here:

[motor_constants omc-17hm19-2004s]
resistance: 1.45
inductance: 0.004
holding_torque: 0.46
max_current: 2.0
steps_per_revolution: 400

from the online calculator we get

pwmgrad: 6
pwmofs: 46
maxpwmrps: 11.087794368735375
hstrt: 0
hend: 1

and from @jay_s_uk 's script we get

M98 P"0:/macros/TMC tuning"
pwmgrad = 6
pwmofs = 46
maxpwmrps = 11.08779
tblank = 0.0000019
tsd = 0.0000086
dcoilblank = 0.0115200
dcoilsd = 0.0125280
hstartmin = -1
hstrt = 1
hend = -2
hstrt1 = 0
hend1 = 1

The next bit is tricky, and I'm not sure if anyone has managed to get this right. If you have a Duet 3 (with TMC22xx or TMC51xx stepper drivers) you can set the stepper registers directly with M569.2. However, with the Duet 2 and TMC2660 drivers, you are limited to what can be set with the M569 F, C, B and Y parameters. And I'm not sure how those relate to the calculator's answers above. I believe the calculator answers relate to the stepper driver parameter names, so check the TMC2660 data sheet. You can also check at least some of the settings by send M569 P[driver number], eg on my Duet 3 Mini 5+ with TMC2209, I get:

M569 P0.0
Drive 0 runs in reverse, active low enable, timing fast, mode stealthChop, ccr 0x00053, toff 3, tblank 0, tpwmthrs 0 (inf mm/sec), pwmScaleSum 11, pwmScaleAuto 0, pwmOfsAuto 36, pwmGradAuto 14, pos 8

NOTE: Be VERY careful messing with stepper driver registers, it's easy to destroy stepper drivers!

Let me know if that helps.

Ian