Never had this happen to me so let me reach out to the group. I recently purchased PLA Silk+ Color :Blue (13604) from Bambu. However, between color changes the filament breaks on extraction. I don’t believe this is a printer setting because I’m using other PLA Silk filaments during the same print and there is no breakage. I use the same model with other colors and not making any changes to the setting and there is no breakage. So this is a spool specific problem. Any idea on what is wrong with the filament?
I should add that this happens with this spool on any model I print and filament is stored in a dry box that maintains a 10-15% humidity at 65F-70F.
Probably a sufficiently good storage humidity but how did you dry your filament?
Storing filament at low humidity and room temperature doesn’t significantly dry the filament. It helps keep it from picking up more water but it takes heat to get the water out. Over months is can dry filament some but it’s a terrible way to dry filament.
I don’t know this is the problem with your filament but some filament tends to get brittle as moisture content rises. That’s all I’m going by but if I had to bet, I’d say you aren’t actually drying the filament and water is what is messing with you and causing filament to get brittle.
It has always been my understanding that filament only needs to be dried if it is stored in a humid environment for an extended period of time. Also I have not experiences typical moisture issues like bubbles, stringing, poor layer adhesion, or warping. The filament is fairly flexible and the only symptom is breaking upon extraction from the extruder during a color change. To me that is more of a problem with tensile strength rather than a brittle filament.
Most filament HAS been stored in a humid environment for an extended period of time; on the container ship crossing the ocean. Brand new filament can be moist and in need of being dried, especially hydroscopic materials like PETG. The main issue I run into with moisture though is the filament breaking off where it connects to the AMS lite, rarely any warping/bubbling. After it’s been properly dried it will no longer break. Dryboxes are good for keeping dried filament dry, but unless you’ve dried it yourself you can’t assume that it doesn’t have moisture in it already. You can even see this by weighing your filament before and after drying it to see how much moisture is lost
Got to be careful with this, though. Some assume a low weight difference after drying means the spool was dry to start with.
Unfortunately, if drying is ineffective there can also be a low weight loss even though the filament may still be very “wet”.
If you get a good weight loss you can have more confidence the dry was effective, but without knowing starting or ending water content, you still don’t know where you are with moisture content. That can be important with the really hygroscopic filaments. With the easier stuff like PLA though, you’re probably ok when you get a good weight loss.
I know that’s splitting hairs a bit but it can matter.
I disagree that moisture is the root cause, as poor tensile strength is not a typical symptom of moisture absorption. However, to eliminate moisture as a factor, I used a SUNLU dryer to dry the filament for six hours at 55°C. After the drying cycle, there was no measurable weight loss when checked with a digital scale. I then re-ran the print to verify the results.
As expected, the outcome remained the same. I would appreciate further assistance in diagnosing the issue before approaching Bambu to report a potential defective batch.
Based on other research I’ve done I may have additional causes.
Increased Brittleness:
Some users have noted that Silk PLA filaments exhibit increased brittleness, leading to breakage during retraction cycles.
No fix
Heat Creep:
There are instances where inadequate heat dissipation in the extruder leads to filament softening above the hotend, causing deformation and breakage during retraction. forum.bambulab.com
Need a suggested fix
Retraction Settings:
Excessive retraction distances and speeds can contribute to filament grinding and breakage, especially with Silk PLA. Adjusting retraction settings has been suggested as a potential solution. forum.lulzbot.com
I did not say it was the root cause. I said brittleness has been associated with high moisture content. Search here for brittleness and see what you find.
Since the problem is obviously not moisture, I hope you have good luck sorting it out.