Strange Ringing artifacts on coreXY

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.

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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...