Strange Ringing artifacts on coreXY

Phaedrux

I meant that I wonder how many other people have the problem but just don't notice it or ignore it or get frustrated and give up trying to fix it.

I'm also trying to chase down the exact cause of it. Is it the belt? Is it the tooth profile? Is it an eccentric pulley?

What is different between the people who have the problem and the people who don't?

robm

@phaedrux
I suspect most 3d printers have the problem, the users just don't notice it or consider it normal. When I started recognising it, I realised I had it on some of my oldest prints, with completely different frame, extruder, hotend, motors. I see the problem in most images of printed parts online now.

Probably more massive printers like Deckingman's avoid it.

Mine seems to be stepper motor vibration, Here's some things I have found can affect it:

PETG vs ABS : I think PETG solidifies faster and locks in the waves, while ABS stays soft and they even out. Also PETG tends to be more shiny so the pattern is more noticeable. I don't use PLA (don't have a fan), but my previous experience was it is very soft and slow to harden so should not show the problem.
lower belt tension - causes other problems of course, but my theory is that the vibrations are not transferred as well with lower tension. Created this tensioner so I could vary the belt tension in a controlled fashion to test this. @kuhnikuehnast interesting idea to replace with fishing line, but again this might be just reducing the tension and hence the linkage between the vibration and the extruding filament at the nozzle.
more steps per mm as noted elsewhere (so 16t pulleys, created this GT2 belt clip to help with that, and 0.9 degree stepper motors).
in my case it seems to be a constant frequency around 25 Hz (with 1.8 degree steppers), so the pattern is most pronounced printing at 30mm/sec. Slower speeds run the peaks together so the surface is rougher but without the pattern, higher speeds spread the peaks out so they are less noticeable. If yours is belt teeth or a wheel issue I would expect the pattern to be consistent regardless of print speed.

kuhnikuehnast

@robm said in Strange Ringing artifacts on coreXY:

@phaedrux
I suspect most 3d printers have the problem, the users just don't notice it or consider it normal. When I started recognising it, I realised I had it on some of my oldest prints, with completely different frame, extruder, hotend, motors. I see the problem in most images of printed parts online now.

Probably more massive printers like Deckingman's avoid it.

Mine seems to be stepper motor vibration, Here's some things I have found can affect it:

PETG vs ABS : I think PETG solidifies faster and locks in the waves, while ABS stays soft and they even out. Also PETG tends to be more shiny so the pattern is more noticeable. I don't use PLA (don't have a fan), but my previous experience was it is very soft and slow to harden so should not show the problem.

lower belt tension - causes other problems of course, but my theory is that the vibrations are not transferred as well with lower tension. Created this tensioner so I could vary the belt tension in a controlled fashion to test this. @kuhnikuehnast interesting idea to replace with fishing line, but again this might be just reducing the tension and hence the linkage between the vibration and the extruding filament at the nozzle.

Interesting thing is, with the "normal" setup I used before (toothed Idler): As I reduced the belt tension, the ringing increased. Only as I used the flipped belt, I could improve the quality by a reduction of tension.

more steps per mm as noted elsewhere (so 16t pulleys, created this GT2 belt clip to help with that, and 0.9 degree stepper motors).

The more steps/mm idea didn't help as written above (200/mm vs. 80/mm)

in my case it seems to be a constant frequency around 25 Hz (with 1.8 degree steppers), so the pattern is most pronounced printing at 30mm/sec. Slower speeds run the peaks together so the surface is rougher but without the pattern, higher speeds spread the peaks out so they are less noticeable. If yours is belt teeth or a wheel issue I would expect the pattern to be consistent regardless of print speed.

here you are right... It is independent of print speed. (although I could notice a small reduction while printing at horrible fast speed. (but this also reduced the overall print quality).

For me it is just really really strange! I print the same filament (PETG) as with my Anet A8 (converted to an Am8). And this damn printer (A8) worth with all the updates ~200€ prints so damn perfect compared to this 3k-machine... I can't print almost nothing that has to fit together because of this damn ringing! argh!

May I just ended up with bad luck as I bought the Idlers and have to give another try? Any source of good quality Idlers around in europe?

and @the problem of vibration: Already thought about "undock" the motor from the normal belt? (e.g. using a double Pulley with an endless belt?)

robm

A few more thoughts:

even with the metal frame your Anet probably flexes more than the corexy and thus dampens vibration?
In your image I count more bands in the bottom strip compared to the top.
I found this app useful in characterizing the problem

DocTrucker

Morning. I've a thingverse d-bot core xy at work and an ormerod 2 at home. The Dbot is running a duet ethernet (recently upgraded from duet 0.6) and 0.9 degree high torque steppers on the xy plane. The Ormerod has the metal x arm and bed support, and an adjustable foot but is otherwise standard with the Duet 0.6 and 1.8 degree steppers.

I see the problem in my machine too, and you can see it on a photo where I was asking for help with another issue. I'll add the link when I find it. Changing the duet card, and from 1.8 to 0.9 steppers had no effect on the pattern.

I've only recently started to work om the ormerod but don't see the pattern on there.

The belts on the Ormerod are twisted to run smooth side on the idlers. They are also much shorter, so assuming all else equal (think ormerod has gxl belts and dbot is whatever ooznest put in the dbot kit) will be much stiffer - stretching far less for the same load.

The dbot was built as per the build manual amd the belts run toothed side over the rear idlers at least. I had thought about running toothed idlers but that isn't a small mod. I will try twisting the belts to get smooth side on the idlers though!

Edit: Here's the link to my post about a seperate issue but showing the wobble.

https://forum.duet3d.com/topic/5052/extrusion-not-always-starting-correctly/2

AlexLin

make sure the pulleys on the motors are centered. If Y jitters with x-movement, some pulley/idler is out of center. This can happen when you have tightened you grub screw a bit uneven. Calculate whether 1 revolution of motor equals the the distance between the peaks in the pattern

kuhnikuehnast

@robm said in Strange Ringing artifacts on coreXY:

A few more thoughts:

even with the metal frame your Anet probably flexes more than the corexy and thus dampens vibration?

In your image I count more bands in the bottom strip compared to the top.

I think that's just because of the photo... As the part is printed just 1 layer in vase mode it tends to bend and you can't take a photo exactly...

I found this app useful in characterizing the problem

Tried a similar thing yesterday for android... The frame isn't vibrating at all.... It is just the Carriage "vibrating" back and forward on the y- respectively x-axis.

@alexlin said in Strange Ringing artifacts on coreXY:

make sure the pulleys on the motors are centered. If Y jitters with x-movement, some pulley/idler is out of center. This can happen when you have tightened you grub screw a bit uneven. Calculate whether 1 revolution of motor equals the the distance between the peaks in the pattern

This was also a thought I had... But as I also tried 0.9 stepper motors, they have round shafts. So The Pulleys are almost perfectly centered as they are installed...

This problem really ride me nuts! What would you think is the best idea to test next:

re-design all printed parts to run with a 9 mm belt? (maybe the thickness of the belt is just to small? (but couldn't recognize a difference as changed from 6 mm to 5 mm belts)
Switch the whole system to "fishing-line-driven" (using v-slot bearings and this "motor-line-mount" http://forums.reprap.org/read.php?246,818734 )
Trying to use a 2-sides-fixed Pulley instead of the motor shaft at the ends? (could build a double-sided Pulley-Mount and run the motors "uncoupled" with an endless belt)

kuhnikuehnast

This is a photo of the results as I used the fishing line... 0_1527087901206_20180521_170337 (Large).jpg

dc42

Could it be that the pulley teeth don't have the right profile for a GT2 belt, so the belt doesn't fit snugly on them? Or that the belt teeth do not have the correct profile?

I had a similar problem with Chinese-made MXL pulleys a while ago. The tooth profile of the pulleys didn't match the belts at all. I eventually solved the problem by switching to UK-made belts and pulleys.

robm

@dc42 said in Strange Ringing artifacts on coreXY:

Could it be that the pulley teeth don't have the right profile for a GT2 belt, so the belt doesn't fit snugly on them? Or that the belt teeth do not have the correct profile?

I had a similar problem with Chinese-made MXL pulleys a while ago. The tooth profile of the pulleys didn't match the belts at all. I eventually solved the problem by switching to UK-made belts and pulleys.

Was this apparent by looking at the belt wrapped around the pulley, or was it more subtle?

robm

@kuhnikuehnast said in Strange Ringing artifacts on coreXY:

@robm said in Strange Ringing artifacts on coreXY:

I found this app useful in characterizing the problem

Tried a similar thing yesterday for android... The frame isn't vibrating at all.... It is just the Carriage "vibrating" back and forward on the y- respectively x-axis.

I would play with more variations then, just to see if you learn anything new. With this instrument you don't need a working printer to test individual pieces.

What is the relationship between the main vibration peak Hz and the speed of the carriage? Is that relationship constant as you vary speed (motor current, microstepping, X or Y offset, other stuff) ? Can you explain the relationship in terms of belt teeth, pulley geometry or something else?
Does it change as you expect if you remove either belt independently, both belts, replace each belt one at a time with fishing line? Perhaps remove a belt and clamp the carriage on that axis and confirm the peak is gone.

This is just a troubleshooting technique I try when I am stuck. If I understand the the system correctly, I can perturb it and it changes as I predict. If it doesn't I have found a new weakness in the problem to chip away at.

kuhnikuehnast

@dc42 said in Strange Ringing artifacts on coreXY:

Could it be that the pulley teeth don't have the right profile for a GT2 belt, so the belt doesn't fit snugly on them? Or that the belt teeth do not have the correct profile?

I had a similar problem with Chinese-made MXL pulleys a while ago. The tooth profile of the pulleys didn't match the belts at all. I eventually solved the problem by switching to UK-made belts and pulleys.

This looks like a really good idea! I've been looking for high-quality pulleys for a long time but have not really found anything good so far. May you send me a name / brand / shop where you can buy UK-made belts and pulleys?

I definitely want to give a try!

dc42

@robm said in Strange Ringing artifacts on coreXY:

@dc42 said in Strange Ringing artifacts on coreXY:

Could it be that the pulley teeth don't have the right profile for a GT2 belt, so the belt doesn't fit snugly on them? Or that the belt teeth do not have the correct profile?

I had a similar problem with Chinese-made MXL pulleys a while ago. The tooth profile of the pulleys didn't match the belts at all. I eventually solved the problem by switching to UK-made belts and pulleys.

Was this apparent by looking at the belt wrapped around the pulley, or was it more subtle?

The main symptom was a lot of backlash. I could feel the belt sliding over the pulley a little because the grooves in the pulley were too wide for the belt teeth.

May you send me a name / brand / shop where you can buy UK-made belts and pulleys?

I got mine from motionco.co.uk but unfortunately they don't sell GT belts and pulleys, only MXL and HTD.

whosrdaddy

@kuhnikuehnast : If you have access to Misumi, they also have quality stuff (not cheap though ).

kuhnikuehnast

@whosrdaddy said in Strange Ringing artifacts on coreXY:

@kuhnikuehnast : If you have access to Misumi, they also have quality stuff (not cheap though ).

which parts would you recommend from misumi? As they offer a lot of different belts / idlers / stepper pulleys it seems quiet confusing!

But anyway, short update:
The problem still persists! Tried now the following:

Installed "TL-Smoother" (https://www.banggood.com/TL-Smoother-Addon-Module-With-Dupont-Line-For-3D-Printer-Stepper-Motor-p-1222339.html?utm_source=google&utm_medium=cpc_lang&utm_content=bruno&utm_campaign=fr-sds-ele-3dprinter&stayold=1&cur_warehouse=CN ) They are recommended usually for DVR8825 or A4988/2 drivers but I wanted to give a try--> didn't reduce the ringing
updated the whole system to flat idlers only and mounted the stepper motors at the back. (so the only toothed - belt- interaction would be of the stepper motors. And after a short distance, the belts are redirected by flat idlers so possible vibration caused by the toothed idlers would be minimized. ) - If anyone also wants to give a try, here is the thingiverse link: https://www.thingiverse.com/thing:2975496
--> this didn't work either...

I am now considering to upgrade to Hiwin rails, to gain more stability... But I don't know whether this will really help solving this damn problem...

Do you think upgrading to flanged bearings would maybe help? (If yes, which kind of bearings (type) would you recommend? And how would you clamp them? I think the usual way with 3 mm bolts isn't the best?

greetings kuhni

kuhnikuehnast

Btw. just had another Look at the e3d toolchanger: if theese holders shown in this picture are printed with their new toolchanger it seems they'd suffer the same probleme as I do... https://static.e3d-online.com/wp/wp-content/uploads/2018/03/above-calibration-600x450.jpg

mrehorstdmd

@kuhnikuehnast

I saw something in a Gates white paper about using smooth pulleys with belts, and they recommended using a pulley that is equivalent diameter to a 40 tooth pulley as a minimum. For GT2 belt, that would be about 25 mm diameter. I use stacked F608zz bearings for pulleys (22 mm diameter, so almost as large as the minimum recommended size) and have none of the vertical lines in print walls that you are seeing with the GT2 belt teeth contacting the smooth bearing surfaces. I use 8mm bolts for the axles, though shoulder screws might be better.

The mass is pretty high - there are 8 bearings and two big, heavy bolts on the ends of the X axis, so if you're one of those guys for whom speed is the prime measure of a printer's worth, you might want to find something smaller and lighter.

I mounted the pulleys in square aluminum tubing so that the top and bottom of the pulley axle would be supported to minimize inward flex caused by belt tension. The large bottom surface of the tubing is screwed down to the Y axis bearing blocks with 4 screws. It is very stable.

alt text

hussainsail2002

Has anyone managed to solve this issue ?.

Am running into the same issue with an e3d styled corexy gantry with the belts crossing over at the back.

Thanks !
Hussain!

kuhnikuehnast

@hussainsail2002 said in Strange Ringing artifacts on coreXY:

Has anyone managed to solve this issue ?.

Am running into the same issue with an e3d styled corexy gantry with the belts crossing over at the back.

Thanks !
Hussain!

Did this happen to a gantry using linear rails? Cause this was a possible solution I wanted to try next...