I used the opportunity to finally swap out the extruder for the upgrade I purchased during Bambu’s P1 upgrade package offering last summer as well as swapping out the PTFE. I had already swapped out the nozzle.
After wasting all that time - and learning a lot in the process - I came out of it with a theory. When I went back to basics and measured the problem filament, I noticed that the stringiest of filaments were all 1.75’ish. However, the filaments that had no stringing were closer to 1.74 and 1.73’ish. Now contrast that with some filament that I returned two months ago that just plain jammed because of a 2mm lump every ten meters(multicolor filament) and it occurred to me that maybe smaller diameter is OK while larger larger is definitely not.
So the theory here is starting to look like filament drag in the tube as a possibility contributing to poor retraction and therefore stringing. There is one YouTuber who demonstrates that if you’re in a bind and need a quick and dirty way of getting past some stringing problem on an emergency basis, to uses a dab of olive oil to temporarily adding extra lube to the PTFE. No thank you I refused to try that because I have no idea what it might do to my new extruder and Nozzle. Besides, I’m printing, not making a garden salad.
And for those who would ask, yes, I did try to dry and calibrate these PLAs for both temp and retraction to no avail. After 100g and many wasted hours? Back in the box to Amazon and a black mark on my spreadsheet tracker.
Two of the offending stringy filaments BTW were Bambu Matte colors both red and grey and gold Silk. Both classes of filament have high friction leading me to believe that maybe I also need a larger diameter PTFE to reduce friction.
So the question remains, has anyone gone through the process of double checking their filament diameter? I’ve tested a number of filaments over the last few months and it seems by my small sample or straw poll, that 1.75 is purely a guideline, not a rule.
I do not believe your theory is correct. Resistance in the PTFE tube won’t be an issue for the short motion required for a retract. The tube just changes radius slightly to make room for the filament, the filament isn’t pushing all the way back to the filament buffer.
If I ignore all the other data points you’ve included, I’d say the problem was water absorption in the “fatter” filament. Water absorption will cause the filament to swell, and water will cause the filament to string.
Seeing you say you did dry it, I’d suggest the drying time/temp might not have been sufficient. Try it again but max out temp and go for 24 hours. Maybe the stuff is just really, really soggy…
I would have thought moisture was an issue too but what I didn’t mention was that drying the spool for six hours only netted a 4g weight reduction. At the time, I had used less than 50g of filament so that indicates a less than 1% moisture content. Truth be told, I was hoping it would be that easy and I’d have my solution but that was not to be.
Interesting side note. I compared some side by side first layer samples of Matte black filament and this one filament that I returned was quite a bit more translucent.
I wish I could find a way to measure the chemical signature of these filaments. I’m starting to develop a theory though in particular regarding matte filaments. There have been some reports I’ve read that the way that the matte finish is achieved, is through additives. In one case, there was a filament that advertised Eco friendly and when you burrowed into the literature they seem to imply and organic additive. On an unrelated maker of filament, they stated they used corn starch.
That all being said, given the high translucence of some filaments and the opacity of other filaments, are we seeing a “watering down” or dilution of base materials in order to stretch their respective formulas. It’s not like anyone is testing these guys and it’s still the wild west.
Well, many filament manufacturers make a point of emphasizing their quality control. Some will just be lying, but some will be telling the truth. Just have to find one that’s actually doing what they say and stick with them.
I’ve had good luck with filament, but I don’t buy no-name brands. I haven’t used a lot of BBL filament, but I haven’t had any issues with that, when I have. Including the PA which is definitely a little over-sized on the roll I measured (24 hours drying at 70ºC).
Maybe take a look at your PTFE tube routing. Filament can definitely bind in the tubes if they’re curved at too sharp an angle. The BBL design kind of makes the tubes “free range”, they go where they want. But some judicious re-bending might correct your issue (but I honestly don’t think the filament has to move much or at all inside the tube for a retract. It’s just not enough motion to matter unless the filament is binding right at the printhead.
I actually did re-route the tube to provide for a more bend-free path. There wasn’t a lot of bend to begin with but I did unclip it from the cable management track to experiment and left the tube free-floating. There was zero difference.
Incidentally, last night I got in a spool of Overture just to do a side by side and precisely because I wanted to see how close the pre-defined Bambu Studio tuning was - it wasn’t even in the ballpark BTW. Overture had a marked difference in performance but not at the prices they are charging. The Overture price is quite often also 60% higher at between $17 - $24. I don’t mind paying, I do mind over-paying.
As of now, the clear winner in my catalog of filament shoot-outs continues to be Colido which consistently comes in at $14/Spool. And from time to time I will go with Jayo when they have their act together. Jayo fluctuates wildly at $10-$16/spool. I would not put Jayo up against a Colido or Overture for quality but they do serve a purpose when they are sub $13. This is especially the case when I am doing design work where I am discarding most of my prints as I refine a design. I save the good stuff for the final print.
