I am suddenly having this “stitching” on both my P1S printers. It appears related to a new batch of Bambu ABS filament. I don’t normally dry ABS, but I am drying a couple of spools now. While I wait for that I figured I would ask if anyone has seen this before?
Two of the photos shows a good print on the left for comparison. These models have been printed hundreds of times without problem.
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Drying the filament is an excellent first step and that would be my leading theory.
However, did you weigh your filament before you placed it in the dryer?
I ask because this is a critical step to diagnosis which so many folks overlook. So you put it in the dryer and it magically works. But how do you know if it was moisture that was the root cause? It could have been something else. If one weighs the filament before and after, not only can you be certain that moisture was remove, but also how much moisture was removed. The other consideration is; how will you know it’s totally dry unless you weigh it. A decent dryer should dry filament within four hours bur the only sure fire way to know is to measure the weight and when it stops losing weight, you know for certain that the moisture has been fully expunged.
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Are both the old and the new problem parts printed with the same gcode file or were the parts printed with different sliced files?
I had 1 successful print after 6hrs of drying but of course I was not that scientific about it! I’ll do more testing today.
What sort of weight reduction should I expect? Only a couple of grams or more?
I just reprinted from the cached g-code file. (Hit reprint on Bambu Handy history).
Okay so it should be the same file which would point the blame at the filament as you suspected.
That’s the $64,000 question that’s behind this method. You shouldn’t “expect” anything. That would be a biased answer. What you looking for is “anything”. If the result is zero weight loss after drying, then it means one of two things, either there was zero moisture to begin with or your scale isn’t working.
To answer your question though. On average, I observe a decrease of 2-4g. But YMMV.
I’ve noted occasions where I observed a weight decrease of over 6g on brand-new factory-sealed spools. However, there are documented cases where YouTubers mentioned that cardboard spools can retain moisture. Out of curiosity, I took some empty PLA spools I had never dried and placed them in a dryer for 12 hours. Surprisingly, in one case—I can’t recall the maker—the cardboard spool contained 4g of moisture. To put that into perspective, a teaspoon holds 5g of water.
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The mystery continues… The 2nd print was back to the photos above on the same g-code and same spool of filament.
I rolled back the firmware to 01.06.01.02 and hit reprint. Will report back.
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I’m going to make a post about this as a PSA later, but try calibrating your flow dynamics. I had this same issue with a large batch of ABS parts. They were printing fine and then all of a sudden looking like garbage. It turns out changing my flow rate K value for Bambu ABS to 0.015 solved my issues. I think a firmware or software update changed the ABS K value to 0.04 which is WAY off.
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Thank you so much, you saved me a lot of time!
I thought all the filament settings would be part of the g-code. I actually have the models sliced as generic ABS but didn’t have problems using Bambu ABS. Currently the K value for generic ABS is 0.02 but running the flow calibration on Bambu also showed 0.015 as the better option. Same as you.
I don’t use Bambu Studio for reprints. How would this work practically when I swop filament in the AMS? Will it remember that I want 0.015 for Bambu ABS or would I need to constantly update from the default setting?
No problem! I probably wasted at least a kg of filament and thought I was going crazy as I was trying everything possible to figure out the solution.
I believe the flow dynamics K value for the filament being used is stored on the AMS so you have to go onto your AMS settings in Bambu Studio to change that. I don’t see an option in Bambu Handy to change it… Hopefully Bambu Lab changes the K value for their ABS because it’s definitely incorrect.
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