Hi all,
Not new to Bambu printers as such having a p1s and X1c then selling them both for 2 x H2S’
One thing that has been bugging me for a while and after various convos with chatgpt I still haven’t found an answer…
I see a lot of people calibrating their filaments when they get a new reel/supplier. I understand this, and do this so that the material changes the K factor and applies it during print.
What I don’t understand is, why do I need to do this if the machine as the auto calibrate function?
I tried this on my H2s and it just advised me to switch off auto calibrate.
Is there more to filament calibrations that I need to do other than the flow dynamics calibration for each filament?
Thank you
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Automatic calibration can be convenient, but it’s not always accurate enough for those who care about precision. The automatic process sometimes introduces noticeable errors and also consumes a small amount of filament every time it runs.
By manually calibrating, you avoid that waste while achieving tighter control over flow, pressure advance, and material behavior. For many users, the automatic calibration works fine and gives decent results, but if you want consistent precision and material-specific tuning, manual calibration is simply the better option.
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Thats great, thank you for that. Perhaps i’ll just have it off going forwards then.
I had an issue where my printers weren’t picking up the calibrated filaments on the HMI which was odd then it suddenly did pick them up.
Are there any other standard calibrations people carry out or is literally just the flow dynamics calibration per filament then done? I’ve seen the flow rate claibration on the bambu studio screen but never touched it.
I’m probably a bit of an odd user, but here’s how I do it:
First, I estimate a good starting K/PA value.
Then I print a completely hollow 20×20×20 mm cube (or something similar) and measure the wall thickness. It should match the number of wall loops; if it does, the flow ratio is correct. If not, divide the expected value by the measured value and multiply that by your current flow ratio. Print another test cube and measure again — repeat until you’re satisfied with the accuracy.
For some filaments, I don’t bother much with K/PA, but when I do, I print a 60×60 mm plate with a single-layer height and visually inspect it. I adjust the K/PA up or down until I’m happy with the result.
These are the basic calibrations. You can also fine-tune the actual MVS and temperature if needed, though temperature can depend on the model, which makes it a bit trickier. Ironing is another calibration you can do if necessary.
If you dive too deep into calibration, though, you might find yourself staying down that rabbit hole longer than it’s fun!
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Wow fair play that’s really indepth and thorough! Makes sense though once you’ve done it, it’s done.
I think what’s thrown me off is that when you see posts on facebook etc when people have issues with filament, peoples gut reply is to say “calibrate filament” so I assumed that worked alongside the auto calibration, I didn’t realise most people have auto cal turned off and relied on the filament calibration to sort these issues.
I’m lucky so far and not had any major issues with filaments but wanted to make sure I was doing everything the best I can to get the max out of the printers.
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No, it’s either automatic or manual — not both. Bambu Lab will use the automatic calibration if that option is selected. 
If everything is working fine, just let it run the automatic calibration. However, if you ever start having issues later on, doing a manual calibration might help you sort them out.
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Yeah, many things you could adjust and you have decide where to make the cut.
E.g., I’m always wary when people calibrate temperature using those temperature towers. If you want a meaningful result, you should test different temperatures at the print speeds you intend to use later. But even if you use the same profile for temp tower and real prints, issue is, that the towers have a really small cross section so that the slicer reduces speed to maintain minimum layer time and even then the layer time will me far shorter than for most regular prints. Most of the time, I just use the Bambu presets or around the upper 1/3 of recommended range. So far, only PETG has been a bit picky and I needed substantially different temperatures for different brands. That was with old non-HF PETG. Newer HF flavours have been far more relaxed.
For PA, I have been perfectly happy with the results from automatic calibration. Even on the X1C, prints with automatic calibration often looked better than with manual calibrations. Now with X2D it is always perfect and I have zero motivation to do it manually again. Why invest the effort with worse results.
Flow rate is the one thing I tune on every new roll. More than 2-3% off can be clearly visible on surfaces and layer adhesion / Z strength takes a serious hit at too low flow rates.
I use the built in manual test, they carried over from Orca slicer. It is only visible when you enable developer mode in the settings. Then a second “Calibration” menu appears above the regular menu bar. I typically skip the first pass and instead increase the flow ratio by 0,05 (5%) so that I cover ±5% around the suggested range. Would be great if they also carried over Orca’s YoLo test.
One other test I do once per brand from the hidden menu is the max flow rate test to see how fast I can go.
And once per brand I measure how much the prints shrink after cooling, using my own test model:
https://makerworld.com/en/models/803990-shrinkingtest-v4-1-by-alex_vg#profileId-744301
For bigger parts, that significantly improves accuracy.