Hello,
I recently started to experiment with bambu’s PACF and PA support filaments on my X1 Carbon with AMS. However, I noticed that there is no retraction when the printer switches from the support filament to PACF. When it is done with the support filament for a layer, the hotend moves to the front-left corner of plate, stays there for a few seconds, then moves over to the chute and starts purging. During the process, the support material just freely leaks out of the nozzle, gets dragged over the print, and makes a mess. My print setting is mostly default, other than enabling support, setting the “Support/raft interface” to Sup.PA, and slow down most of speed parameters below 80 mm/s. The filament settings are all left at bambu default.
At the time of this post, I am using the latest bamblu studio (1.6.2.4) and firmware (01.05.02.00)
My print settings are as following:
Someone in the forum suggested override the filament setting to enable retraction on layer change. I tried it and it did not seem to change anything.
Does anyone have the same issue and any suggestions? Thanks.
Your problem is that your filament has absorbed moisture. Nylon is particularly good at this. The moisture in the filament turns to a gas (steam) in the hot-end, and gasses expand when they heat, which slowly drives filament out of the nozzle even though the extruder isn’t pushing.
No amount of retraction will fix this (and you will find it over-extrudes on the de-traction). You need a filament drier.
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Thanks for the reply. I am fully aware of the moisture problem. The image attached in the post was taken during my first test print. I was excited to try it out and I knew there was going to be print quality issues like poor surface quality and oozing. But the problem I am writing about is not about oozing. It is about support filament leaking when the hotend travels to the chute for purging.
I have since then dried out both the PACF and PA support filament (12hours at 90C). The problem did not change with the dried filament. And the problem has nothing to do with moisture in the filament. Because you can see the green filament is all over the place, especially a long string running from the front all the way to the chute. There is clearly lack of filament retraction/control before the hotend reaches the purge step.
Latest image attached here. As I am running a different print with both filaments dried right before the print, same issue persists.
They’re not dry enough. This second picture you posted is exactly what I’d expect. It’s not retraction. Even with zero retraction the nozzle isn’t going to ooze like that. The only thing that can make filament ooze out of the nozzle like you describe and show in these pictures, when the extruder isn’t pushing it, is moisture in the filament.
Just because you put your filament in a dryer doesn’t mean it dried out. The results you’re posting say (to me) “it’s not dried out”. If I was having this kind of problem, I’d extend my drying time.
Red Matterhacker Nylon Pro after 24 hours of drying at 65ºC.
Red Matterhacker Nylon Pro (and blue, too) after 48 hours of drying at 65ºC
It was unprintable as used directly from the packaging.
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I am not sure about that. My filaments are dried daily, 12 hours at 90C, and kept in sealed container with desiccant and humidity meters. And in the second photo, there is no oozing on the printed parts, only the leak trail left behind from the left front corner to the chute. The printed parts has good surface condition. However, this leak problem is a potential risk if the print is long and at some point there is a chance the leaked material got dragged to the print area. It seems like you are not using a different filament for support. I do not have this leak problem either if I use the same material for support.
I do not have this leak problem either if I use the same material for support.
So what that says to me is, your primary filament is probably dry enough but the support filament is not.
As I’ve said, the extruder isn’t pushing the filament and it doesn’t just dribble out like that on its own. Something is driving the filament out of the nozzle and steam is really the only culprit for that.
You’ve got nothing to lose by drying it further. Give that a shot… dry it for 24 or 36 hours instead of just 12. If that fixes the problem, you can start to “back down” to shorter drying periods until the problem comes back.
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Thanks for the advice. I will try extend the dry cycles to 24 hours and see if it solves the problem. It was just surprising to me that daily drying routine is not enough to keep these filaments dry enough.
What I’ve noticed with my dryers is that the RH drops pretty proportionally with the rising temperature. The humidistat in the dryer is reading the ambient air humidity inside the dryer, which is not the same thing as the humidity of the filament. My new process is “wait for RH to bottom out, then wait another 24 hours”. And this seems to be working pretty good with the Nylon I’m using.
I have observed that after a few days in my AMS, even though the AMS says it’s good on humidity, the filament gets a bit soggy again. I go from essentially zero oozing to strands an inch or so long. But before drying at all, those oozes were long enough to drape across the build plate. But another 6 hours back in the dryer seems to address that.
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