Flow Calibration

[CptHungarian]

I tried to get answers to these questions several times on other platforms, let's see if I have better luck this time.

What does the flow calibration do exactly?
Does it actually adjust the flow ratio or is it just a linear/pressure advance calibration?
Where is the calibration data stored and how long does the printer retain it?

Here is an example of my recent prints where I printed the top part without any calibration.
Then I decided to do a "flow calibration" and the bottom part suffered from washed out details, rounded edges, etc.
Exactly what bad linear/pressure advance calibration would cause.

The next day I reprinted the same part without running the calibration and all these problems disappeared... (apart from the terrible ringing, but that's a different topic)

My theory is that the printer only stores the linear/pressure advance calibration values temporarily and these values are only valid for the current print.

[steezyprintz]

I would also like to know more about the flow calibration is stored etc. I am assuming its stored in its memory until another one over writes it at the moment as it seems to be happening to mine.

What I have learnt recently with my X1C is that the colour of the filament does make a noticeable difference to how well the flow cal works and then how well prints come out. For example dark colours like black and grey they too much like the build plate and I was getting errors/warning about exposure from the lidar. Adding more light didn't help much, So I changed to yellow in the same material / brand and the z seam and the corners sooo much better for it. I ran the flow cal and printed a small box in yellow, I then switched to printing what I wanted in black same material and brand (esun PLA+), print came out very nice after that in black. I am pretty sure I read about this on the facebook page several weeks ago from someone experiencing the same.

I would really like the flow calibration to be a displayed value that can then be added to custom/3rd party material settings to avoid needing to do that process too many times. Being able to set it up would be ideal as bambu labs range of materials is rather limited currently.

I would really like Bambu labs to sell the RFID tags that we can stick onto 3rd party materials spools and use it like their own, storing the flow cal on to the RFID tag, how much used, the colour and material type etc.

[psiberfunk]

It would seem that flow calibration does NOT, as you would expect, actually adjust the flow ratio! Here's the proof in a print:

When I set my flow ratio to 0.15 .. this is what happens. It looks like the "flow calibration" pattern is printed at a fixed flow ratio (maybe 100%?) regardless of what you tell the slicer. This is why these purple calibration lines printed OK. It looks like it uses this to inspect for linear/pressure advance tuning (K values) . However, when it comes to my print , which SHOULD be in the red circled area.. there's nothing. So it's clearly blindly using my flow ratio in the slicer and NOT calibrating for it.

This means what Bambu labs advertises as "flow calibration" is really linear/pressure advance and NOT Flow ratio!

[psiberfunk]

I would suggested @wuyifanfancy , that perhaps when you get back from the holiday, that this ought to be tagged as a bug ? It's either a bug that you say you do flow calibration and you don't (e.g. rename what you call it)... or it's a bug in the sense that flow calibration SHOULD be happening, but does not.

[steezyprintz]

yeah so the translation of flow calibration or the meaning of it is like you say @psiberfunk I don't think anyone here was misunderstanding it to mean flow ratio.

I would love for the flow ratio to be measured and adjusted for automatically as well as other filament dependent settings like the shrinkage, if bambu labs can do this they will make me very happy but also move home 3D printing actuate parts for n00bs so much further forward to being the magic plug and play!

[psiberfunk]

I personally actually did misunderstand it to mean flow ratio from the marketing videos and such until I ran my tests on my new printer !

[Liamnerf]

Hopefully Bambu lab, in future, can modify their code in order for the LiDAR to calibrate flow as well linear advance. Perhaps when they develop a standalone flow calibration process. Presumably any flow ratio settings set by the user in Bambu studio would need to be disabled.

[CptHungarian]

@YifanWuBambu So can someone from Bambu answer these questions please? To be honest, this information should be publicly available for all users either in the wiki or user manual, as this is one of the main selling points of the printer.

[psiberfunk]

@steezyprintz : Clearly others, including Bambu's own folks are finding this confusing. This information is now getting misrepresented by Bambu's own wiki team ! Here: https://wiki.bambulab.com/en/x1/manual/manual-flow-rate-tuning it suggests that "The X1 is able to automatically calibrate the flow rate based on the filament used" but that you can do better by "tuning it manually". The reason is because.. shocker.. it's not tuning the flow ratio at all as the wiki page explains how to do manually.

It's not a good thing when even Bambu's own people are conflating the difference between flow ratio and linear advance. It's abundantly clear that this needs to be rectified/clarified.

Could Bambu please address this confusion before it gets worse @YifanWuBambu ? This is beginning to become more of a "bug" than a feature request considering the confusion it's causing.

Update: it looks like they reworded that particular wiki page to be more technically accurate.. but it still doesn't resolve the marketing and other confusion.

[RobinWhitfield]

The reason is because.. shocker.. it's not tuning the flow ratio at all as the wiki page explains how to do manually.

Are you 100% sure this is the case?

The flow rate provided in the slicer could very easily be a multiplier on top of automatic calibration.

If there is no flow rate calibration happening, then surely the pattern printed to the left of the PA lines would be totally superfluous.

I 100% agree that we need clarity from the Bambu team on this though. It's not like it's a big secret that cannot be revealed in order to protect their IP.

[psiberfunk]

The flow rate provided in the slicer could very easily be a multiplier on top of automatic calibration.

@RobinWhitfield
Well, first, i'm not sure how that logically makes sense. The automatic calibration is against linear/pressure advance. Flow ratio calibration would be a different thing entirely.. I'm not sure how you could just apply a multiplier to a pressure advance value to get a flow rate... but maybe I misunderstand what you're getting at ?

But regardless of whether it makes sense or not, I'm pretty sure. Take a look at the test print pic (purple filament) I ran above where I reduced the slicer flow ratio setting but left auto-calibration on. It was a disaster, proving that no sort of flow-ratio calibration is going on at all... or if it is, the slicer setting hammers it, even when the calibration is ON... which, in practice, is pointless, because you're always going to have a setting in the slicer.... this effectively means there is no such thing as flow-ratio auto-calibration.

[Merlwynd]

I would also like to get clarity or confirmation on this. Important simply to know limitations so one can calibrate properly using common tools (i.e. hollow calibration cube). Doesn’t look like anyone at Bambulab yet assigned to provide answer?