Meanwhile … Do it yourself 
The 2 in the back are still smooth pulleys unfortunately. Need to dismantle the printer much more to exchange them.
And yes, I think I lost somehow one washer underneath the pulley
And yes, I think I lost somehow one washer underneath the pulley
You MUSTN’T change the two on the back as they are on the slick side of the belts.
It seems to me that you forgot the washers as the toothed pulley isn’t centered, they aren’t really optional.
Your axis is really dirty too, it require cleaning. To know that you’re not supposed to lube the linear bearings, if you use the wrong oil or grease you can potentially damage them.
Its white thing on axis is grease from greasing the bearings as good as possible. Picture taken in the middle of mounting. I cleaned all rods after finished my work of course.
Seems to be no problem at all without the washer. I centered the pulley manual and it stays (up to now).
I will receive some other pulley, maybe they fit better. They should be a little wider. Will see.
In the back corners there are two idlers on the slick side and two on the other side. But yes, maybe they don’t make much difference. Also this two at the gantry don’t make much difference in VFA. Seems it is more from the stepper-motor resonances.
Well, I finally got the new pulleys in and had some time today to swap the new toothed idle X-axis in, with great excitement.
After installing it, I fired up the same VFA gcode that I ran before, with the same filament… and the result looks almost identical:
@Alkerion you said that you swapped in genuine Gates belts at the same time? Where did you get those?
Which pulleys did you install finally ?
I’ve changed the belts first, then I’ve installed the motor dampers and then the pulleys.
You can find the Gates 2GT rather everywhere on Amazon or Ali.
https://fr.aliexpress.com/item/1005005725753433.html?spm=a2g0o.productlist.main.5.363d62c2kvsJIN
Same pulleys as you did.
I can’t find a single listing on Amazon that looks like a genuine Gates belt. I just ordered some from West3D. Did you just pry off the stop wedges and glue them to the new belts?
Where did you notice the big reduction in the 2mm artifacts? After the pulleys and dampers I take it. I don’t want to do dampers, because of the positional uncertainty they add.
Maybe it’s the combination of the toothed idlers and the Gates belt, that wasn’t realized with just the belt.
Mine don’t seem to be riding the flange, but I can’t help but think interaction with the flange can add artifacts. I was thinking about asking Mellow if they can make a set of pulleys in the same height, but with no flange. I could knock the flanges off of these, but having full length tooth profile would be better.
I went looking for other potential sources.
This nearly 0.003" TIR on the B-Motor pulley isn’t helping anything…
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I didn’t notices any improvements with just the belts, and nearly nothing with dampers.
Only the pulleys solved the issue.
Other people did the modd and have really noticeable improvements like me.
Does your head move really freely on the carbon rods ? (when non attached with the belts)
Changing the belts is rather easy, I simply glue them together and added some tape.
My original X-axis with some hours on it moved very freely. I bought a new replacement for the idler experiment, and it is much tighter. So, even with a big change in X-axis rod friction and the toothed idlers, the print looks essentially identical.
Well, I put the Gates belts in today, and again no difference.
@Alkerion you did a great job! I do not have my X1C yet, but researching before purchase, so I can’t test it out, but: do I see correctly that just the whole black bracket holding 2 carbon rods is upside down? If we just rotate it by 180 degrees (and also rotate the tool head) - will it be easier than drilling them to swap the pulleys? I simply noticed, that ribbed pulley is on flat side of belt and the flat pulley on ribbed side of the belt, while the 2 black brackets holding the carbon rods seem to be symmetrical.
Did anyone try 180 degrees rotation of them - and the whole tool head? Seems to be the cleanest op, if they are indeed symmetrical…
There are no toothed idlers on the stock X axis assembly.
That has been covered already. Some renderings show toothed idlers. No printers have them, that I have seen.
Those are the locations we have switched to toothed. Lower left. Upper right.
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What you gentlemen have discovered here deserves respect and admiration. At the same time, I am surprised that bambu has never given a real answer to such a common problem, occurring in practically every printer, only “just print faster”. Do you think there is a chance that we will one day receive an official solution, along with repair parts from bambu?
100% agree. Those vfa are ruining my print finish and making them sometimes unusable for toght tolerance functional parts. For a 1000$+ printer, I expect that they offer a solution to existing owners as well.
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I asked the the support a while ago. Thats the response:
“The choice of a smooth idler pulley instead of a toothed one is because using toothed pulleys can cause vibrations between the gears, especially after some time when the belt tension is relatively loose. This vibration can significantly impact print quality. Through our testing, we have found that using a smooth idler pulley results in better printing results.”
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Thx a lot for sharing this!
Funny answer, they want us to believe they used smooth pulley because we can have artifacts when belts are loose.
Actually, based on my mod, what I see is that there is lot less print artifacts with toothed pulley than smoothed one.
And it’s really easy to tighten the belts if they are too loose.
I think it would have been easier, and most probably more honest, to recognize their mistake (deliberate cost saving choice from a buyer more probably, as the printer was designed with the right pulleys).
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Hi Alkerion,
I have been studying the subject for some time.
I think you identifyied the problem correclty.
However, my idea instead of replacing the pulleys would be to glue teeth against teeth a portion of timing belt where the smooth idler pulley runs.
Indeed, this portion of timing belt is never encountering the motor.
This would make the smooth idler puller run on a smooth belt surface, without heavy modifications, doing the gluing in place.
Will post with the results, if I find time to perform this.
Best regards.