Yeah, there is that. Closed hardware is a blessing and a curse, eh?
Thanks!
2 Likes
Bambu sets motor currents for X, Y and Z using G or M command. If you dig through your start GCode, you can actually spot it several times 
1 Like
When I said ācurrentā I meant āwhat itās set to nowā. Youāre right that motor current values can be set, but thatās not relevant in this discussion.
1 Like
What it is set to now:
M17 X1.2 Y1.2 Z0.75 ; reset motor current to default
1200 mA for X and Y, 750 mA for Z
@Botanic2000 , please read the whole thread. Weāre not talking about motor current, but rather X/Y/Z steps.
2 Likes
From my understanding we need to set the step values in order to use a more steps per mm motor
My question now is arenāt there higher quality motors with the same steps per mm that have better output control between steps ?
Iām thinking a higher quality stepper motor that can handle the accelerations better might resolve some of the resonance coming off the factory motors
The Voron guys seem to focus a lot on the vibration frequency of the steppers for fine tuning at higher printing speeds
I donāt know about the rest of everybody on this thread but Iām learning a lot through others trial and error
It is much appreciated
1 Like
I actually dove a bit into the world of input shaping and CoreXY on some other printers. Hereās my sort of unfortunate answer after a lot of testing with both a heavily used (700+ hours) X1C and brand new P1P, both of which had nearly identical VFA patterns.
My suspicion is that these patterns are in nearly every Bambu printer to different degrees, but many users do not notice this level of surface imperfection. Iām included in this group - I didnāt notice the ringing until I read the complaints and did a VFA test myself and started experimenting to better understand it. Looked back at all the models I already printed and realized that those patterns frequently showed up in regions where the printer had to slow down for cooling.
Those waves are resonances of the mechanical system of the printer, even after input shaper which corrects for mechanical resonances. This is why you can literally hear the frame vibrate at the speeds that cause the worst VFA during the VFA test. They could be mitigated by improved algorithms, but that only goes so far without mechanical changes, some of which could very likely make the printer better at low speed printing but worse at high speed printing. I have some very warranty-voiding ideas to temporarily remove high speed printing capabilities if you absolutely need to print at low speeds (TPU comes to mind), but maybe Iāll mention that another timeā¦
Iām starting to think that this is just a brave new world of high speed printing - many high speed (e.g. non-bed-slinger) printers actually have resonances in what used to be the ānormal printing speedā ranges.
I have a totally different delta printer that Iām running the same VFA pattern in OrcaSlicer and it actually also has noticeable ringing in certain directions at low speed (very different kinematics, so different patterns but similarly velocity-dependent ringing). It is similarly optimized to print at 200-400mm/s with input shaper correction, and actually can print as fast as Bambu on its defaults (but took ages to set up and calibrate and I am in fact an engineer)
Bambuās happens to be better than my delta printer at high speed and worse at low speed. Itās possible that this is also representative of a CoreXY frame of this size. My feeling is that most people going for CoreXY designs are speed demons, and they really justā¦donāt look very hard at low speed printing. Theyād rather speed up everything up about the printer so that you never even think about printing below 200mm/s if possible.
Iām getting very off topic here, but I have a feeling that a certain other printer company hasnāt released their IS firmware due to wanting to reduce similar resonance patterns after already optimizing the frame to print well at low speeds. They have had complaints about VFA in the past, but maybe there just really isnāt an easy way to get this level of surface quality in a printer at both very high speeds and very low speeds in the same frame. Thatās also why I kind of suspect the whole idea of switching to 0.9 degree steppers could be a bit of a bad idea - I suspect it just doubles the resonance frequency or something along those lines, and youād suddenly be fine printing at low speeds but ruin high speed performance in the 200mm/s range.
Anywho, letās cross our fingers and hope some brilliant improvements to the input shaper algorithms or motion control tricks in the Bambu can improve low speed performance. Itās most likely going to be a firmware fix.
2 Likes
well said. IIRC Bambu already answered to a user recently that theyāll be releasing a firmware update which should address the resonance issues reported. So yeah, letās see what theyāll deliver 
1 Like
Thatās all well and good, but just to be clear, this is very much a mechanical problem and no amount of software trickery will fix it; I have three X1Cs and one has no VFAs, and the other two are absolutely junk with VFAs.Therefore, Bambu needs tighter hardware QC controls.
1 Like
Could you send pics of the actual OrcaSlicer VFA test? I only have two but both exactly have largely the same VFA patterns over print speed. My assumption right now is that all of them have exactly the same VFAs if youāre actually running an exact head-to-head test. I only have two so thatās not enough to be sure, but they were surprisingly very similar.
1 Like
Hey there! Alright, so all of them are printed with PolyMaker Polylite PLA Pro using the built in PLA profiles. I am using the latest OrcaSlicer updated today. This is the 60 deg face of the VFA test
The last one is the good one, the other two are terrible
EDIT: 90 face, NOT 60 face. Typo.
I can not see any VFAs on the flat surfaces. On the inner arcs I believe it is not VFAs, but model arc approximation defects. They are present on all angles on mine and not affected by the speed.
Worst case for VFA is a shiny darker colored plastic under a harsh directional light.
Usually it looks like this (ignore moire):
On mine X1C it is the worst on 65mm/s 30 degrees. From 150 to 200mm/s it completely disappears.
1 Like
Your definition of terrible is very different to mine. This is what I have:
I would love to get the practically perfect quality you are getting.
Oh man, I wish I could see that 
Yeah, think the lighting and resolution means I basically canāt see any VFA artifacts at all :((
I would love to see the good one, my running theory right now (which might be wrong and you might be able to break) is that itās just on all of them, and people notice it more or less on some models than others. But if you have a perfect VFAā¦as someone who likes messing with hardware, Iād love to figure out how the heck I could match that.
1 Like
Ah I think I get what you guys are getting at. Yeah I think mine may not be so bad after all.
Since I notice these where the angle curve (only on two machines; I think someone called them āmodel arc approximation defectsā), is what I am noticing on the curves related to something else?
Wonder if the newly released Creality K1 has similar behavior at low,and high speeds? The motion mechanism is definitely different
2 Likes
Well, I have decided that I am going to wait in the gallery to see how that one does. If I was in the market for a P1P I would add the K1 to my list as potentials, but I plan on another X1C.
K1Max has more features but not out yet.
New X1CC user here. Just received my unit and first print was a benchy with the included PLA. Probably the best benchy Iāve ever printed. Next two prints are a zero clearance insert for a miter saw printed in Bambu ABS. The one on the left was printed first and exhibits little to no ringing. The one on the right was printed the next day and shows ringing. The only differences are that the one on the right was scaled to 100.76% to adjust for ABS shrinkage and was printed without a brim and normal Timelapse enabled. All other settings in Bambu Studio were the same. Both were printed diagonally on the build plate in the same exact orientation. The printer was not moved or changed between these prints other than being powered down for the night. Any idea why the second print has ringing and the first did not? Maybe belt tension changed since this is a brand new unit? Do I need to clean the CF rod with IPA after every ABS print?
1 Like
This thread has been a huge help to me. I was getting a rough knocking sound that was resolved by soaking the CF rods in IPA and moving the head over it, then lightly lubing all the rods, pulleys and tensioners. Squared the gantry with the jig mentioned above and had what I feel is a good result on the VFA test. Thanks for all the help! Iām generally satisfied with this level of quality, but still jealous of those who somehow pull off perfect prints lol
Any idea what causes this one off line? It looks to be at one of the speed change points.
