RE: VFA Artifacts on X+Y Straight Edges
You obviously didn't read Jo Prusas 'Deep Dive' last week. He's gonna teach us how to fix it all by tensioning the belts a special way 😂
The trick is that you don't merely "tension" them, but you "tune" them! 😎
Well, and he alluded to printing speeds. I am really concerned that the official Prusa advice will also boil down to "just over-tighten your belts and print fast".
RE:
This is just it, Prusaslicer automatically slows down layers if they're below a certain duration, and if you disable that you're basically sacrificing dimensional accuracy.
I mean thats fine if you're just printing those daft articulated dragon things and other silly toys, and if that's all I'm printing I'd buy a Bambu...I bought a Prusa because dimensional accuracy is of high value to me and what I use my printer for.
The "just print fast" recommendation seems to imply that you can either have stable and dimensionally accurate parts, or parts with a non-rippled surface. Many applications will indeed require only one of the two, but it's certainly not a general "solution" for the VFA problem.
At normal circumstances speed does not affect dimensional accuracy. Even when you set fast print speeds, printer slows down for sharp turns and small features. Check the the "Actual speed" in sliced preview. Also input shaping and pressure advance compensates for any imperfections caused by fast accelerations and decelerations. You would have to mess with machine limits (or input shaping calibrations) to affect dimensional accuracy.
PrusaSlicer slow downs whole layer for cooling (Filament -> Cooling -> Slow down if layer print time is below). Which defaults to values that may not be always the right ones. Filament profiles may have adjustments for different nozzles (at least the predefined ones), but they doesn't change for different print settings, especially for layer heights (and extrusion widths). When printing for example 0.25mm SPEED or 0.15mm SPEED, the filament's layer time slow down limit is the same, even thou the actual volumetric flow rate and cooling demands are very different for these settings.
Filament settings may need adjustments for speed profiles printing (slightly higher temperature, disable slow down for fast layers, ...). It depends on actual model and other print settings. Actual speed and Actual volumetric flow rate in sliced preview are very useful and should be something everyone checks before printing.
I think the SPEED name of the print profiles is wrong and misleading. It should be named NORMAL (or DEFAULT, or something like that). Core One is fast printer by design. I "upgraded" from MK3S+ and it took me some time before I understood that Core One is not "MK3S+ in enclosure". Printing 45mm/s with STRUCTURAL profiles, like at MK3S+ speed, may be waste of time if I don't have special reasons to do that.
RE:
You obviously didn't read Jo Prusas 'Deep Dive' last week. He's gonna teach us how to fix it all by tensioning the belts a special way 😂
The trick is that you don't merely "tension" them, but you "tune" them! 😎
Well, and he alluded to printing speeds. I am really concerned that the official Prusa advice will also boil down to "just over-tighten your belts and print fast".
Don't be so cynical Jurgen
I have complete faith it's going to be a good couple of weeks...All the VFA issues finally resolved and if the Core One Camera roadmap is adhered to all the (big) problems with that will be resolved also. 🤣
Its like Xmas coming early 🎄🍻
Prusa will make a killing when we're all replacing bent stepper motors in 12-18 months !
RE: VFA Artifacts on X+Y Straight Edges
At normal circumstances speed does not affect dimensional accuracy. Even when you set fast print speeds, printer slows down for sharp turns and small features. Check the the "Actual speed" in sliced preview. Also input shaping and pressure advance compensates for any imperfections caused by fast accelerations and decelerations. You would have to mess with machine limits (or input shaping calibrations) to affect dimensional accuracy.
Speed might not directly, but the side effect of speed is insufficient cooling. Why do you think the (Filament -> Cooling -> Slow down if layer print time is below) option is on by default ? It guarantees good layer adhesion and it guarantees dimensional accuracy.
If I'm printing big parts, or a bed full of parts it's a non issue...but that's not always the situation I'm in.
RE: VFA Artifacts on X+Y Straight Edges
I agree - if run-out or shaft wobble contributes it might be twice per rotation but it should still manifest as a secondary pattern behind the clear pitch related issue. Wobble in particular I could see making mesh be less than ideal when the pulley isnt perfectly square to the belt, but I also suspect the belt has enough flex to accommodate.
RE: VFA Artifacts on X+Y Straight Edges
We have discussed it a couple of times -- in my opinion, run-out (whether from the pulleys or the motor axles) is an unlikely candidate for the root cause for belt ripple/VFAs.
I'm not saying it's the root cause. Root cause is the pulley (or rather, the meshing which pulley lottery solves by finding a well matching pair).
I'm saying the right motor's pulley position makes the situation worse and introduces its own faint ripple that is unfixable with a pulley swap.
RE:
I'm not saying it's the root cause. Root cause is the pulley (or rather, the meshing which pulley lottery solves by finding a well matching pair).
I'm saying the right motor's pulley position makes the situation worse and introduces its own faint ripple that is unfixable with a pulley swap.
And I'm saying that I can't see how the pulley position (and a potential wobble of the pulley) could make significant contributions to the problem, without also causing a longer-period component in the ripple pattern -- which has never been reported. 😉
RE: VFA Artifacts on X+Y Straight Edges
I just have one question for now: if they're not seeing VFAs in house (which seems to be plausible considering my motor/pulley mount blocks which are printed by Prusa and do not have VFAs), then what are they using to print the CoreOne parts that do not exhibit the VFAs?
RE: VFA Artifacts on X+Y Straight Edges
I just have one question for now: if they're not seeing VFAs in house (which seems to be plausible considering my motor/pulley mount blocks which are printed by Prusa and do not have VFAs), then what are they using to print the CoreOne parts that do not exhibit the VFAs?
Fibers in PC-CF effectively hides VFAs. Fibers, glitters, light fuzzy skin, ... anything that "breaks" surface hides VFAs.
At normal circumstances speed does not affect dimensional accuracy. Even when you set fast print speeds, printer slows down for sharp turns and small features. Check the the "Actual speed" in sliced preview. Also input shaping and pressure advance compensates for any imperfections caused by fast accelerations and decelerations. You would have to mess with machine limits (or input shaping calibrations) to affect dimensional accuracy.
Speed might not directly, but the side effect of speed is insufficient cooling. Why do you think the (Filament -> Cooling -> Slow down if layer print time is below) option is on by default ? It guarantees good layer adhesion and it guarantees dimensional accuracy.
If I'm printing big parts, or a bed full of parts it's a non issue...but that's not always the situation I'm in.
Cooling depends on model. It's there for preventing things like curl up above overhangs. But if you print for example box, you may be just fine with minimum cooling or cooling off.
RE: VFA Artifacts on X+Y Straight Edges
if they're not seeing VFAs in house
Then they are lying. Even their official marketing, such as YT shorts showcasing interesting prints, display visible VFA.
Timestamp - 0:12
Also Josef didn't state they don't see it in that Reddit post. He stated they don't see it at such a severity. Which leaves possibility they do see it and just don't care or deem it "normal for coreXY, nothing to do here".
which are printed by Prusa and do not have VFAs
As Biomech stated - PCCF hides artefacts fully.
RE: VFA Artifacts on X+Y Straight Edges
Ive got some ABS-GF that prints beautifully, and even some cheap and cheerful Amazon special PETG-CF that’s looks great for the money.
I’ve also been thoroughly impressed with Overture Matte PLA which is cheap as well.
I’ve said it before but Im convinced the Core One can/will be a really strong printer if Prusa can get a handle on this VFA issue. I would like the option to print glossy filaments well without shaking my house foundations.
RE: VFA Artifacts on X+Y Straight Edges
Heck, I had a super clean print in ASA after a change to a non-HF nozzle - first print in ASA so tested by printing a dessicant bottle I've printed in PLA and PETG before (former on speed, latter on structural) and both had artifacts I could feel - not so with the ASA. And till this Ive been able to feel VFA even if I can't easily see them. Leaves me hopeful.
Other issues I tuned out in the first few layers mind...
RE: VFA Artifacts on X+Y Straight Edges
I think there is potential for motor mounting angle to affect meshing and possibly produce belt ripple, but I've not tested the idea and it may not be an issue in practice. If a motor was skewed in any direction, the pulley teeth would no longer be perfectly perpendicular to the incoming or outgoing belt teeth, the meshing might not be as clean as one end of the tooth would enter the pulley before the other and could potentially create the disturbance in the belt that causes the ripple in prints.
I think overall belt/pulley tooth geometry mismatch is much more likely the problem. I can see why it is a difficult thing to get right, you have to take in to account the slight stretch of the belt at different tensions, aging changes, temperature changes, durability vs flexibility (a softer belt would potentially mesh in a more compliant way)....
RE: VFA Artifacts on X+Y Straight Edges
I think there is potential for motor mounting angle to affect meshing and possibly produce belt ripple, but I've not tested the idea and it may not be an issue in practice. If a motor was skewed in any direction, the pulley teeth would no longer be perfectly perpendicular to the incoming or outgoing belt teeth, the meshing might not be as clean as one end of the tooth would enter the pulley before the other and could potentially create the disturbance in the belt that causes the ripple in prints.
I think overall belt/pulley tooth geometry mismatch is much more likely the problem. I can see why it is a difficult thing to get right, you have to take in to account the slight stretch of the belt at different tensions, aging changes, temperature changes, durability vs flexibility (a softer belt would potentially mesh in a more compliant way)....
Time for Kevlar belts!
RE: VFA Artifacts on X+Y Straight Edges
Also Josef didn't state they don't see it in that Reddit post. He stated they don't see it at such a severity. Which leaves possibility they do see it and just don't care or deem it "normal for coreXY, nothing to do here".
I can understand that. I myself wrote reviews for the MK4, MK4S, XL and CORE One and clearly noticed the VFA issue on the CORE One during my first Jet Black PETG print with straight walls. Now looking back to the XL, I can now see them too but I never noticed them before. At the time of the XL test I only noticed that the print quality was either better on the XL or the MK4 depending on the object. Now I know why.
A stupid idea I got while reading all the exchanges around the pulley and belt pattern matching, would it be possible to do a simple test by flipping the belts? Even at slower speed to avoid slippage. The idea behind is to confirm or not the pattern influence. The ideal would be to have non-toothed pulley too, but seems unlikely.
To go further, trapezoidal pulleys also exists (maybe not at this size unfortunately), with multiple grooves to improve contact area (easily doubling it). They can slip under severe constrains, but with good tension and well tuned acceleration it could do the job without any trace of belt pattern.
What do you think?
RE: VFA Artifacts on X+Y Straight Edges
I wonder about shallow toothed or even herringbone belts and pulleys
RE: VFA Artifacts on X+Y Straight Edges
They wanted to save money by reusing the MK4 motors, which clearly have way too short shafts for the way the belts run on a Core One. Now WE are paying for their penny-pinching.
To be fair, I think the re-use of the MK4S motors was to keep the upgrade path intact. If they didn't people would be unhappy because upgrading your printer from model to model is the expectation with a Prusa machine.
RE: VFA Artifacts on X+Y Straight Edges
To be fair, I think the re-use of the MK4S motors was to keep the upgrade path intact. If they didn't people would be unhappy because upgrading your printer from model to model is the expectation with a Prusa machine.
There is no upgrade path between MK4S and Core One. There is a conversion path. They didn't keep the upgrade path intact, they introduced a new conversion path between two completely different lines of printers.
People wouldn't be unhappy because Core One isn't the next i3 iteration. It's a new line just like the XL or Mini. People aren't complaining they can't convert their Mini+ into a MK4S nor are they complaining about converting to an XL from any other model. Why would they complain here?
MK4S -> Core One was never the expectation. Converting one model line into another was never the expectation. Prusa went out of their way to allow a conversion, and by doing so reused a massive amount of parts and made everything cheaper for themselves. The design of the Core One as a whole suffered by introducing this conversion as they had design constraints that wouldn't be present otherwise.
RE: VFA Artifacts on X+Y Straight Edges
At normal circumstances speed does not affect dimensional accuracy. Even when you set fast print speeds, printer slows down for sharp turns and small features. Check the the "Actual speed" in sliced preview. Also input shaping and pressure advance compensates for any imperfections caused by fast accelerations and decelerations. You would have to mess with machine limits (or input shaping calibrations) to affect dimensional accuracy.
It's interesting you say that. I printed the rocket motor that came with the Core One on the flash drive... for giggles really. I came out insanely well printed. There were three spots that did not print as they were supposed to based on the Prusa GCode for the small rocket motors. Otherwise, it was flawless. Honestly.
That told me that if you tweaked a build based on what you were seeing with the printer, then it would suffer almost no VFA. The includes things like slowing down in specific areas, etc. Which is was very clearly tweaked to do...
Also, I had them assemble the printer for me... so that likely means that I'm not seeing to worst of these reported issue because they performed all of the QC for me.
RE: VFA Artifacts on X+Y Straight Edges
MK4S -> Core One was never the expectation. Converting one model line into another was never the expectation. Prusa went out of their way to allow a conversion [...]
I believe Prusa mainly went for the conversion approach because it was one of the few differentiators (or the only one?) over other CoreXY printers. "Our printers are a long-term investment, you don't have to buy a new one every 2-3 years."
What else do they have, besides a door that does not break (but instead may bend when it gets too warm) and the promise that "we are the good guys, trust us that we will not lock you in or otherwise abuse your data"? The latter was the selling point for me, but with hindsight I am not sure I still want to treat the "good guys" benefit for the general organizational incompetence they are exhibiting.