Vibration artefacts on Y-Axis  

RE: Vibration artefacts on Y-Axis

I still have the Y axis artefacts. I've flashed the IS RC firmware today and the artefacts are still there. The belt is currently tensioned to "a little too high" and it's still artefacting, just a bit less. The artefacts are way more noticeable when the bed moves towards the motor. This is unacceptable quality from a "no VFA motors" printer.

RE:

Posted by: @shushuda

I still have the Y axis artefacts. I've flashed the IS RC firmware today and the artefacts are still there. The belt is currently tensioned to "a little too high" and it's still artefacting, just a bit less. The artefacts are way more noticeable when the bed moves towards the motor. This is unacceptable quality from a "no VFA motors" printer.

This is no VFA. They (vibrations) are much smaller. This is induced by your motion system. Thats the part im sure on it. My theory for your ringing (not VFA!) is either a belt rubbing against the top or bottom of a pulley or your X-gantry. When moving in Y there is no motion in X, so the printhead is vibrating, not your bed while moving.

RE: Vibration artefacts on Y-Axis

Ah, I've planned on updating this thread, but forgot. Tldr, my issue turned out to be a faulty motor pulley on Y axis. It made that ripple. It's now pretty much gone.

You can see the photos and a few explanations in PrintFixFriday, as I've shown those to Grant on his Discord. It's the headline of the episode lol.

As for other artefacts, I still have a weird orange peel that happens on Y axis only and starts at around 45mm/s and only increases with speed. It's actually very strong at 45, meaning the default best looking IS profile (structural) is significantly worse than no-IS profiles. It's worse than Ender quality, to be frank, as those printers can be updated to Marlin 2 with IS or Klipperized and they don't have this artefact despite pushing higher accels and speeds. This orange peel happens on both stable and IS firmware, it's not affected by LA, PA, IS, whatever. It's just speed. As if the motion system of this printer wasn't designed with anything over 40mm/s in mind and higher speeds got introduced only because of the very recent market shift.

As a side note, I do have VFA. On 20mm/s even. I did a dragon bust print and one side of his face is covered in VFA, it's exactly the same as on the comparison photo Prusa posted to market MK4 motors as "no VFA". My print looks like the MK3 example.

This VFA has its peak at around 40mm/s too, for that matter. It's pretty much visible only on silk filaments at 20-25mm/s, but at the structural profile it's so strong I can feel it under my finger. Seems to happen on accels and deaccels, so it must be somewhere around 35-40mm/s. It makes the "best quality" profile of the IS fw look disgustingly bad, as these peak speeds are constantly happening throughout the print. The VFA disappear on the IS speed profile, but then the orange peel artefact increases.

In general, I can't print slow because VFA. I can't print fast because orange peel. And I can't print in the middle because both at once.

I went through new Y bearings, a new Y belt, 3 Y motors and none affect the orange peel nor VFA. The VFA happens at a specific angle closer to X than Y, also on the other side (when mirrored). I'm awaiting a CS email currently, the person I talked to is supposed to review my case and write to me. But I'm not the only person with these artefacts, both VFA and orange peel.

Posted by: @rhotix

 

Posted by: @shushuda

I still have the Y axis artefacts. I've flashed the IS RC firmware today and the artefacts are still there. The belt is currently tensioned to "a little too high" and it's still artefacting, just a bit less. The artefacts are way more noticeable when the bed moves towards the motor. This is unacceptable quality from a "no VFA motors" printer.

 

This is no VFA. They (vibrations) are much smaller. This is induced by your motion system. Thats the part im sure on it. My theory for your ringing (not VFA!) is either a belt rubbing against the top or bottom of a pulley or your X-gantry. When moving in Y there is no motion in X, so the printhead is vibrating, not your bed while moving.

RE: Vibration artefacts on Y-Axis

Same artefacts on y.

Waited 16weeks for top quality 

RE:

@shushuda

Can you explain the specific issue with the old pulley that you think was causing this problem?

Your photo screenshotted from Grant's video:

RE: Vibration artefacts on Y-Axis

I wish I could. I have no idea why the old one was behaving the way it was. It looks as if that middle toothed section was badly attached or something, but truth be told - I don't know. That black stuff on the side is not only belt residue. There's a tiny black line going inbetween the toothed section and the flange, as if those parts weren't attached properly to each other. That's the only thing I've noticed. Customer support also didn't see anything weird and I've sent them a lot of additional photos from all sides to give them as much info as possible.

If your printer makes these wide ripples that look like belt teeth - trying out a new pulley won't hurt.

Posted by: @coreyansgar

@shushuda

Can you explain the specific issue with the old pulley that you think was causing this problem?

Your photo screenshotted from Grant's video:

RE: Vibration artefacts on Y-Axis

I just replaced the y-motor pulley on my MK4 and the artefacts are gone.

Images: old vs. new (same gcode)

RE: Vibration artefacts on Y-Axis

I have 3 mk4 printers.  2 are older (#1 and #2, ordered release day), one received this month (#3).

Printers #1 and #2 exhibit this vertical line VFA this post discusses, and has always done so.  Both x and y axes are affected. I have iterated thru almost all firmware releases, no change (currently on 5.0.0).  I have iterated thru almost all prusaslicer releases, no change.  Problem affects models sliced for IS and not-IS.  Problem affects all prints, regardless of speed, material, etc.  It's not ringing, as 1) the lines are always vertical and not influenced by other model contours and 2) the lines don't dissipate with distance.  Pitch between lines is 2mm, a perfect match to the belt tooth pitch.

Printer #3 does not present this VFA whatsoever.  The same files printed on #1 and #2 do not have VFAs when printed on #3 (same g-code, same USB stick).  Firmware is same as printers #1 and #2.

After reading this post, and seeing the suggested solution of replacing the motor pulley, I was near certain the motor pulleys were the cause of my issues as well.  

Being that I had printers both WITH and WITHOUT the issue, an easy way to verify was to swap motor pulleys between "good" and "bad" machines and observe for differences.  If the VFA's followed the pulleys, then cause verified.

First, I printed a file on all machines to establish a baseline result.  Again, printer #2 had the VFA, printer #3 did not. Then, I swapped the y-axis pulley between printer #2 ("bad") and and #3 ("good") and reprinted the same file.  

Result is that the faces parallel to the y-axis on machine #2 went from yes-VFA to no-VFA.  On machine #3, faces parallel to the y-axis went from no-VFA to yes-VFA.  Furthermore, VFAs on faces parallel to the x-axis were unaffected by the change (yes-VFA on #2, no-VFA on #3), which was predicted as those pulleys were not swapped.  

Conclusion is that direct cause of the VFAs is the motor pulley. The problem follows the motor pulley.

Root cause is not clear, though.  I took measurements of both #2 and #3 pulleys and found them to be nearly identical (by caliper only, I don't have access to the proper tools such as mics and plug gauges).  Visually, despite a little belt residue, they're indistinguishable.  Something was odd about the ID on the #2 pulley, though, as it was a struggle to get it on/off the motor shaft on both #2 and #3 machines.  It also wouldn't spin 360 around the shaft, but rather bind at a certain orientation.  I think it's slightly obround.  I can't foresee how this would cause a VFA with a pitch equal to each belt tooth, though.

RE: Vibration artefacts on Y-Axis

I ran into the same exact problem that I slowly started to notice over time.  When I came across this thread I just went ahead and replaced the Y axis pulley, sure enough it seems to have alleviated the worst of the problem.  This definitely seems to be a problem, I'm curious if the idler is wearing over time or if there was just a bad batch of them.  Like others I cannot discern a different between the pulleys.

RE: Vibration artefacts on Y-Axis

To anyone else coming across this issue, check my reply at https://forum.prusa3d.com/forum/english-forum-original-prusa-i3-mk4-assembly-and-first-prints-troubleshooting/heavy-vfa-on-a-no-vfa-printer/paged/2/#post-681364 for a similar (the same?) looking artifacts. Apparently I hijacked that thread (sorry shushda) but was able to almost completely resolve my artifacts.

I tried swapping motors, pulleys, etc but the thing that did it for me was replacing the smooth idlers with toothed. I remixed Prusa’s parts to fit the slightly wider idlers and I’ve been happy ever since.

RE: Vibration artefacts on Y-Axis

Edit to my reply above, I’m not saying toothed idlers will absolutely resolve any specific artifact issue, only that it’s something else worth trying.

RE: Vibration artefacts on Y-Axis

Hi, I had exactly the same artifacts on the y-axis and was about to order a new pulley. But then I saw that my belt was running on the edge of the pulley as well as on the edge of the idler pulley. I fixed it by aligning the motor mount and the idler pulley mount, underlaying them with paper. Now the belt doesn't always run perfectly in the middle and wanders a little to the left and right, but it no longer comes to the edge. The artifacts have now completely disappeared. 🤓 

RE: Vibration artefacts on Y-Axis

Here's my odyssey...

I've currently the same problem, or at least the same artifacts on the walls that are printed in y-axis direction (so to be exact, the walls, that are printed by only moving the print bed back and forth) on my upgraded MK4. Before the upgrade (which I did like two weeks ago), the same printer was a MK3S, which worked quiet good, and did not have any of such issues at all. I also printed all of the parts for the upgrade on that MK3S, and visually, they were just near perfect.

The artifacts on the upgraded MK4 are less strong with slower print speeds, and less strong using the structural IS profile as well, but they are still there and in the same frequency. So I began to try out different mutual solutions for this problem:

First try was to re-check the belt tension (of the y-axis, but I also re-checked the x-axis as well). I did that multiple times, and always after changing anything else regarding the y-axis. Also tried to increase the tension a little bit, but that didn't change that much either, so I sticked with the default tension since then.

Then I completely dismantled the Y-carriage again, actually tried out all of the LM8UU bearings that I have in my personal spare on the y-axis smooth rods to use the three bearings that I felt had the most smooth movement and also made sure, that there aren't any scratches on the rods that are crossed by the bearing balls. Since the artifacts have such a stable "frequence", I was pretty sure that this wasn't the problem, and yeah, it didn't fix anything. I also checked three times, that the screws holding the bearings aren't too tight and the rods move smoothly after thightening the screws, but everything seems to be as it should here.

So, next try was to check the orientation of the belt, upper and lower part being in parallel to each other. Yeah, there was a little deviation, so I fixed that, but that did nothing regarding the artifacts. But I got aware, that the belt touched the inner wall of the motor pulley. I fixed that as well, so now the belt is in the middle of the motor pulley and as well in the middle of the idler pulley, not touching the walls of any of them. Still no luck in eliminating the artifacts.

That was the moment I found this thread. Assuming I might have a defect motor pulley as well, I just exchanged it with the motor pulley of my old MK3S parts (assuming it is an identical part and not having such a problem with said MK3S in the past). And that changed ... nothing. So I still get the identical artifacts.

Tomorrow, I will most likely get toothed idler pulleys and also some brand new motor pulleys and will try it with them. But actually, by slowly moving the print bed by hand, I just realised that the motor pulley (both the old and the new one) don't turn completely even (meaning that they don't only turn around their axis, but also "swinging around" a little bit). I will compare that tomorrow with the pulleys attached to the old MK3S motor (just moving it by hand again, because of course that one is not compatible with the MK4) trying to see something like that as well. If that's not the case, for me it rather seems like the little rod of the new MK4 z-motor is not moving correctly (like "swinging around" a little bit as well, leading to the pulley swinging). In that case I will contact Prusa support to hopefully get a motor replacement. Don't now if they have spare parts for that at the moment, since that motor is out of stock for some reason, but yeah, we will see.

RE: Vibration artefacts on Y-Axis

With the printer turned off,
If you unscrew the Y axis Idler, you can release the belt without disassembling the y belt fixing. with the belt released, flick it off the toothed Y motor gear, and the Y motor shaft should rotate with tiny back pressure as the motor poles pass the magnet poles, inside the motor. 

if your Motor does not rotate evenly, your motor is probably faulty... (Make sure that the hub of the toothed motor gear, is not rubbing on the body of the motor... 

regards joan

RE: Vibration artefacts on Y-Axis

@JoanTabb: Just tried that. Motor gear definitely not touching the motor body. I can't feel that much difference to the old 1.8° motor of the MK3S, meaning I can feel the single steps while turning, and it feels even. I can't feel any additional "friction" at certain points or something like that.

To make clear what I meant with "swinging around", as you look at the following picture, ideally the yellow dot would move onto the (perfect) red circle route around the motor axis. Instead it takes something like the blue ellipsed route, because (as i tried to show on the right hand side) the motor rod does not stay on the red axis, but moves a little bit in the blue directions.

Of course, the example ist exaggerated, the movement is not as strong as shown in the picture. And dont't be confused: this is the old motor of the MK3S, I just fotographed that one because it already lies next to me on my desk. This old motor - as far as I can see with my bare eyes - does actually not do this slightly uncircular movement.

I would still wait for the toothed idler and see if it changes anything regarding the artifacts, but actually, I already exchanged most parts of the y-belt-system (including the idler which I exchanged with the old one (including the old smooth pulley) of the MK3S, and it did not change anything, not even a little bit. So other than the motor, I'm currently out of ideas what could possibly be wrong here.

RE: Vibration artefacts on Y-Axis

That is Odd. 

I have never seen a motor like this, but I guess faults do happen. 
Have you chatted with Prusa support?  
regards Joan

RE: Vibration artefacts on Y-Axis

Posted by: @volker

I got it improved by increasing the tension of the y-belt - much higher than expected and measured by the App (resonanz frequency). I will see how this will effect the livetime of the belt

That app leaves much to be desired.  I didn't have good results until I closed the app out and used my eyes and ears. Listen for the twang.

RE: Vibration artefacts on Y-Axis

So i'll try two things now:

1.) Ordered Powge Motor Pulley (Very high Quality)

2.) Ordered a teethed idler

Let's see if we can eleminate those things. If not, i will start the refund process (Still within 60 Days)

RE: Vibration artefacts on Y-Axis

Hi!

I have exact the same problem on x-axis. I also tried to change the pulley, checked belt tension and so on… but the artefacts still appear… Did you contact the support? What do they say about that problem?

Greetings