RE:
CORE ONE VFA MAYBE SOLVED?
Here is a summary as of 2nd September 2025 - I will mark it as best answer until we get any significant progress from Prusa or here.
Timeline 2025:
11 Feb - Reported my VFA Issues to Prusa Support
25 Feb - Sent My Core One back
24 Apr - Received Refund
...
19 June - Prusa officially Looking into widespread VFA problems ( https://www.reddit.com/r/prusa3d/comments/1lf9mjv/psa_lets_address_the_vfa/)
1st July - Prusa VFA update 2 - investigating adjusting tensioning ( https://www.reddit.com/r/prusa3d/comments/1lp3eo7/psa_vfa_update_2/)
17 July - New firmware with Phase Stepping - No difference
20 July (?) - New Belt Tensioning App suggests higher tension (95hz vs old 85hz) improvements minimal - VFA still there
1st September - Prusaslicer and tensioner updates to tackle VFA - WAITING FOR TESTING ( https://blog.prusa3d.com/new-in-prusaslicer-consistent-surface-finish-and-nerfing-vfas_120400/)
Forum Investigations:
Things that don't work:
- Changing to toothed idlers has very little effect - It's been done to death and doesn't resolve it ( )
- Phase Stepping Calibration - No change
- Input Shaping Calibration - No change
- Creating belt soft mounts in the kinematics - No change
Things that slightly work:
- Changing to 1.5GT Belts and pulleys - Requires a change on the printer config to scale the model correctly to compensate, reduces VFAs considerably
- Tensioning Very high (~100hz) - Reduces VFAs but they are still there and the tension will slip over time - may damage printer long term
- Printing fast - If you print fast enough the filament will be matte and it will hide the VFA - it will still be there
Things that need testing:
- New PrusaSlicer profiles and tensioning regime - Can someone follow the suggestions on this blogpost, tensioning and prusaslicer on a Core One and test print a gridfinity box with the "balanced" profile with silk/shiny filament and inspect the result under light?
Gridfinity print-in-place test model (2x1): https://www.printables.com/model/465050-gridfinity-container-with-lid-print-in-place/files
Here is the original g-code for comparison prints: https://drive.google.com/file/d/1T7X2J3Gm2UYetzKfY6ZBBM5pxz3wiFaG/view?usp=drive_link
Help! I have VFA on my Core One, what do I do?
The best you can do right now is tension your belts high (100hz), print as fast as possible (avoid structural and stealth modes) and use filaments that minimise the effect. Currently Prusa suggest following their new tensioning regime and using the latest and greatest PrusaSlicer profiles (Balanced) - although this has yet to be confirmed by the community.
RE: VFA Artifacts on X+Y Straight Edges
If I'm not mistaken, Prusa is saying that both SPEED and BALANCED have about the same surface quality. It's just that balanced will produce somewhat stronger prints, and speed will be somewhat faster.
RE:
I dunno if its just me, but this new balanced profile seems a fair bit quieter as well, which is always good.
You seeing any change in print quality?
Not personally, but I'm not printing anything that's likely to show up VFAs right now.
RE: VFA Artifacts on X+Y Straight Edges
Well I just printed up the core one VFA test print… and I compared it to a prior one that I did and it’s definitely a little bit better. There is absolutely one speed range that utterly sucks… otherwise it’s definitely better.
I used the “balanced” .20mm layering in a .4 mm HF nozzle.
I suppose real question does the G code supersede any of the features they put in the beta version of the slicer?
RE: VFA Artifacts on X+Y Straight Edges
My input here is two-fold.
First off, I'm really happy for these improvements, and I look forward to the stable version of PrusaSlicer 2.9.3 in order to start using them.
Simultaneously, I still desperately hope that Prusa will add a toggle switch into the firmware to allow those who want to enjoy the clear benefits of GT1.5 belts. The above example prints from @xzess, along with various other test prints we've seen here and on youtube, make it pretty clear that there is a way to further improve print quality at their source, in addition to the various belt tension and software adjustments. If the reasons given for not doing this include having to recalculate more complicated functions to be optimized to the new belt pitch...I would counter by pointing out that all of the tests we've seen from those who have converted belts have been done with all other slicing and firmware configs aligned the same as the GT2 belts, with ONLY the scaling adjusted. It would be such a simple thing for them to offer those of us who are willing to spend the extra $ and time to retrofit. After-all, they'd be silly to keep putting GT2 belts on their future release printers while all of their competitors have swapped to 1.5 belts and will be enjoying the improved finish. So why hold off on allowing their current model to enjoy those benefits?
-J
RE: VFA Artifacts on X+Y Straight Edges
Well I just printed up the core one VFA test print… and I compared it to a prior one that I did and it’s definitely a little bit better. There is absolutely one speed range that utterly sucks… otherwise it’s definitely better.
I used the “balanced” .20mm layering in a .4 mm HF nozzle.
I suppose real question does the G code supersede any of the features they put in the beta version of the slicer?
If you've just used old gcode. it's not going to use any of the new features/profiles recently added in the beta....Gcode is already sliced.
The slicer makes the gcode.
So no surprise you haven't seen any changes.
What did make me chuckle is reddit is full of posts about how the new settings/profile have solved VFAs, most of the attached pictures are either matte or filled filaments 😂
I think what Josef said about looking for them with VFA tests is right, all 3d printers (especially Core XY) will show them, its just physics...the task is reducing them to an acceptable level. So maybe the VFA tests are always going to show them to some level or another.
Real world tests are what its all about, so maybe printing that gridfinity bin that @baztm linked to earlier would be a fairer test...plus it means not wasting hours/filament on stuff that's ultimately going to end up the bin.
RE: VFA Artifacts on X+Y Straight Edges
My input here is two-fold.
First off, I'm really happy for these improvements, and I look forward to the stable version of PrusaSlicer 2.9.3 in order to start using them.
Simultaneously, I still desperately hope that Prusa will add a toggle switch into the firmware to allow those who want to enjoy the clear benefits of GT1.5 belts. The above example prints from @xzess, along with various other test prints we've seen here and on youtube, make it pretty clear that there is a way to further improve print quality at their source, in addition to the various belt tension and software adjustments. If the reasons given for not doing this include having to recalculate more complicated functions to be optimized to the new belt pitch...I would counter by pointing out that all of the tests we've seen from those who have converted belts have been done with all other slicing and firmware configs aligned the same as the GT2 belts, with ONLY the scaling adjusted. It would be such a simple thing for them to offer those of us who are willing to spend the extra $ and time to retrofit. After-all, they'd be silly to keep putting GT2 belts on their future release printers while all of their competitors have swapped to 1.5 belts and will be enjoying the improved finish. So why hold off on allowing their current model to enjoy those benefits?
-J
Any improvements with these belts really seem anecdotal at this point though. They're not going to implement features for the tiny percentage of users who went to all that hassle.
Plus Prusa's investigation that VFA pitch doesn't even align with the belt pitch would further point to 1.5mm belts not helping.
RE: VFA Artifacts on X+Y Straight Edges
Simultaneously, I still desperately hope that Prusa will add a toggle switch into the firmware to allow those who want to enjoy the clear benefits of GT1.5 belts. The above example prints from @xzess, along with various other test prints we've seen here and on youtube, make it pretty clear that there is a way to further improve print quality at their source, in addition to the various belt tension and software adjustments.
Has it really been proven beyond doubt that this is the case?
Something will change, but is it really a positive improvement in all aspects?
Regardless of the source, who has what intention? Positive or negative towards Prusa.
Or is it to achieve as many clicks as possible on YouTube videos?
That's the impression I get from some people here in the forum.
If Prusa explicitly offers this function, they should also guarantee it and offer support for it.
Above all, first examine all aspects of how it affects all areas in detail.
This will certainly not happen so quickly, perhaps it will happen in the background and a Core One S, or all other printers, will get such an upgrade.
Prusa will not offer a two-pronged approach.
If you want to do it anyway, you can. It is no problem to add the Gcode or change the firmware accordingly.
If it is widespread enough, someone will certainly make the firmware available.
suppose real question does the G code supersede any of the features they put in the beta version of the slicer?If you use the old Gcode, you only test the hardware changes.
If you use the old Gcode, you only test the hardware changes.
I also doubt that the VFA test will be better with the new slicer settings.With this test you want to make the VFA explicitly visible via the speed. In other words, purely to analyze the mechanical part in order to avoid problematic speeds. However, if the slicer cannot maintain this speed because it slows it down due to the layer times, you may be back in a critical area.
The new slicer functions should now improve this by placing this slowdown in invisible areas.Ideally, the outer walls are all equally fast in order to achieve a uniform appearance at an optimum speed. There are also other optimizations to reduce the vibration of the print head.
RE:
Yeah exactly this. Those tests are basically hunting for VFAs, something no one is going to do in the real world.
That's why finding a real-world model, slicing it with the beta and comparing results vs old slicer (or with old profiles and new consistent surface options disabled) is the only way of determining if any improvement has been made.
Regrading the belts we saw in here that improvements were only noticed by some who changed to 1.5 belts, that alone shows its anecdotal at best... and any improvements could be be down to something as simple as re-tensioning the belts after they were swapped out.
RE: VFA Artifacts on X+Y Straight Edges
I think there is at least enough clear understanding and anecdotal evidence that the root cause is mechanical in nature. That means that there are things we can change in the hardware to change or alleviate these defects. That becomes further clear by comparing different brand printers, that do use 1,5mm belts.
All of the changes done by Prusa on the slicer side and the new tuning for the belts is great. They even improved some aspects not really related to this issue. However, I find it strange that they simply brush aside all of the potential hardware changes. I understand it's almost impossible for Prusa to actually offer these hardware changes, except with an Core One S revision.
I still intend to test replacing the pulleys with the Mellow 3D brand ones I have here.
RE: VFA Artifacts on X+Y Straight Edges
Yeah exactly this. Those tests are basically hunting for VFAs, something no one is going to do in the real world.
That's why finding a real-world model, slicing it with the beta and comparing results vs old slicer (or with old profiles and new consistent surface options disabled) is the only way of determining if any improvement has been made.Regrading the belts we saw in here that improvements were only noticed by some who changed to 1.5 belts, that alone shows its anecdotal at best... and any improvements could be be down to something as simple as re-tensioning the belts after they were swapped out.
That's exactly what I did with cheap, shiny, black PETG.
So it could hardly be worse.
A print that also slowed down a part extremely because it is very thin there and the layertime is correspondingly low.
The first print looked really horrible.
You could feel the VFA, terrible.
I then even used the Orca Slicer to have the function that it doesn't slow down the speed on the outer lines to get a passable result.
Now I achieve a slightly better result with the new original profile of the Prusa Slicer than with my previous optimizations.
With the same filament that I will certainly not use again except for functional parts.
With other filaments, the prints already looked good before.
I am curious to see how the whole thing will behave in future real projects.
Also with other printers. The slicer function is not limited to the Core One.
RE: VFA Artifacts on X+Y Straight Edges
I think there is at least enough clear understanding and anecdotal evidence that the root cause is mechanical in nature. That means that there are things we can change in the hardware to change or alleviate these defects. That becomes further clear by comparing different brand printers, that do use 1,5mm belts.
All of the changes done by Prusa on the slicer side and the new tuning for the belts is great. They even improved some aspects not really related to this issue. However, I find it strange that they simply brush aside all of the potential hardware changes. I understand it's almost impossible for Prusa to actually offer these hardware changes, except with an Core One S revision.
I still intend to test replacing the pulleys with the Mellow 3D brand ones I have here.
I think it's good when lots of people test it. This makes the relevance of these changes all the greater.
But the thing with the smooth rollers on the toothed belt side, for example.
No matter on which printer there are totally different results.
With one everything is better, the other can't recognize any differences.
If 100 do it now and 95 see an improvement, it is easier to recognize a connection.
But perhaps it has only changed one other parameter, which is also known as a confirmation error.
Just because other printers using 1.5 belts are perhaps better in terms of VFA does not mean that this is the cause. Or that using it has no other disadvantages.
At some point, all manufacturers have used the 2.0. There must have been a reason for using them.
Which does not mean that alternatives cannot be tested. But you have to consider the entire system.
RE: VFA Artifacts on X+Y Straight Edges
However, I find it strange that they simply brush aside all of the potential hardware changes. I understand it's almost impossible for Prusa to actually offer these hardware changes, except with an Core One S revision.
It's not 'brushing it aside' if their findings point towards it not being a hardware issue, it's simple logic.
And I also have faith that their testing approach is going to be a damn sight more scientific and less scattergun than some enthusiasts just swapping things out.
It's quite clear in Josefs blog, the VFA pitch doesn't match the belts.
Look you can swap out whatever you like, but as the old saying goes, 'You can lead a horse to water, but you cant make him drink'.
RE: VFA Artifacts on X+Y Straight Edges
Plus Prusa's investigation that VFA pitch doesn't even align with the belt pitch would further point to 1.5mm belts not helping.
That's not what they said. Josef's exact words were:
Very early on, we ruled out the motors as the cause. The VFAs we see on the CORE One don’t match the specific pitch that would be caused by our motors. Plus, the motors, drivers, and voltage are well-tuned from the times of MK4, and the CORE One uses the same stack.
So I think the pitch that he's referring to and ruling out is related to the motor steps, not the belt/pulley pitch specifically.
Regarding the VFA test print, I agree that reusing old gcode will only show whether belt tension has had an effect - it can't possibly benefit from new slicer features. But even if you re-slice it, it's still going to miss most of the mentioned improvements to the profiles - it's vase mode, and it very deliberately sets the speed for each height step, so all the speed optimisations for outer perimeters will be bypassed. I think that test now has limited use, and real-world prints are a far better way of judging the performance. In fact they always have been, as Josef implies.
For the record - I'm one of those 'anecdotes' regarding the 1.5mm belt swap. I did see a big improvement across the board, and I'm delighted with the print quality. I'm entirely happy with adding the scale correction gcode to my profiles, even if it means recreating them whenever Prusa issue new profiles. I suspect I'm not going to see the full benefits of some of the profile optimisations because the speeds that lead to the worst results are quite different between 1.5mm and 2mm belt setups. I'll give them a go though. I'm not about to swap back to 2mm for a comparison though!
RE: VFA Artifacts on X+Y Straight Edges
There is some confusion. In the post I link the original model for you to slice and the VFA afflicted gcode from the original post.
If the slicer truly works, your own sliced version should look better than the gcode version when printed
They are both provided for comparison on your specific machine. You should print both. There's no point printing just one.
RE: VFA Artifacts on X+Y Straight Edges
It's not 'brushing it aside' if their findings point towards it not being a hardware issue, it's simple logic.
It's quite clear in Josefs blog, the VFA pitch doesn't match the belts.
Josef said:
You won’t get rid of them, e.g., by replacing the belts. It’s multiple things stacking up.
He didn't say they're not hardware related, and he didn't say that belt pitch won't change them. I think he chose his words very carefully.
RE: VFA Artifacts on X+Y Straight Edges
There is some confusion. In the post I link the original model for you to slice and the VFA afflicted gcode from the original post.
If the slicer truly works, your own sliced version should look better than the gcode version when printed
They are both provided for comparison on your specific machine. You should print both. There's no point printing just one.
Agreed - yours is one of the real-world examples that should be used for testing. I was referring to the specific VFA test model that uses different speeds at different heights.
RE: VFA Artifacts on X+Y Straight Edges
For the record - I'm one of those 'anecdotes' regarding the 1.5mm belt swap. I did see a big improvement across the board, and I'm delighted with the print quality. I'm entirely happy with adding the scale correction gcode to my profiles, even if it means recreating them whenever Prusa issue new profiles. I suspect I'm not going to see the full benefits of some of the profile optimisations because the speeds that lead to the worst results are quite different between 1.5mm and 2mm belt setups. I'll give them a go though. I'm not about to swap back to 2mm for a comparison though!
If the change to 1.5 changes the speed range of the VFA, you would also have to adjust this in the slicer.
Or is it the case that the VFA are less overall?
But overall, all printers benefit from the new functions. It is not the case that it is now specifically tailored to the core one.
I still printed parts in gray ASA with the old slicer, but with higher tensioned belts.
They look absolutely great.
Although grey is a color that mercilessly highlights errors.
To be honest, I already had the parts for the conversion in my shopping cart.
But after Prusa published the report on the VFA, I wanted to wait and see.
Also for the reason you mentioned to keep things simple.
At the moment I see no reason to try it.
RE: VFA Artifacts on X+Y Straight Edges
He didn't say they're not hardware related, and he didn't say that belt pitch won't change them. I think he chose his words very carefully.
'While the 3D printing community has identified several potential sources for VFAs, including motor resonance and belt mechanics, our deep analysis of the affected community printers pointed overwhelmingly toward improper belt tension on the CORE One.'
I dunno, I just feel that if the belts/pulleys/idlers were going to make such a significant difference across the board, there would be more conclusive results mate. I'm yet to try the beta slicer and profile/settings with a filament or print that would actually suffer from VFAs, so I'm keeping my powder dry for now.
RE: VFA Artifacts on X+Y Straight Edges
If the change to 1.5 changes the speed range of the VFA, you would also have to adjust this in the slicer.
Or is it the case that the VFA are less overall?But overall, all printers benefit from the new functions. It is not the case that it is now specifically tailored to the core one.
I can dig out the VFA test photos that I posted earlier, but I think it's both. I felt that the amplitude of the VFAs was reduced, as well as the resonant frequencies being different. I don't want to say too much without checking the test prints again, but my recollection was that the VFAs appear reduced over most speeds, but the speeds where they show up most are different from the speeds that accentuate the problem with 2mm belts. Mostly those speeds don't affect Speed or Structural profiles, so I'm happy.
I haven't looked at what speeds the new Balanced profiles use, so I don't yet have an opinion on whether my 1.5mm setup will benefit from them. All I was saying is that it's a given that Prusa have optimised the Balanced profile for 2mm belts, and it's quite possible that the speed ranges that this profile uses could land my 1.5mm setup in the middle of the speed range that it doesn't like so much.
I agree that the other major change, to the ringing-type artefacts, should hopefully apply to all printers, including my 1.5mm setup.