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This never used to happen...  

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Hoof Hearted
(@hoof-hearted)
Active Member
This never used to happen...

My mini is only a few months old and has had quite light usage. My prints are becoming more and more stringy when I use filament that used to be ok. I opened a new roll of filament today and the photo shows what happened. The model is ok once I clean off the strings, but I wish it wasn't happening. I have only ever printed with PLA and the default temperature settings. 

Posted : 04/08/2022 6:21 pm
Razor
(@razor)
Active Member
RE: This never used to happen...

If all settings are the same Im’m thinking something is up with the filament. Same brand of filament? How old? You have a second package of PLA you can try? Any popping noises when you print? Do you see what looks like small bursts of steam coming from the nozzle from time to time?

Posted : 04/08/2022 7:15 pm
Diem
 Diem
(@diem)
Famed Member

Your filament has absorbed atmospheric humidity and is now damp.

Look up threads here about drying it.

Cheerio,

Posted : 04/08/2022 10:51 pm
Hoof Hearted
(@hoof-hearted)
Active Member
Topic starter answered:
RE: This never used to happen...

Like I said in my original post, I opened I brand new roll of filament today. So dampness cannot be the problem in this case. All my filaments are stored in vacuum bags with sachets of silica gel. I haven't gone through them and tested every single roll, but everything I printed recently seems to be getting progressively more stringy. 

What I have noticed also is that whenever the printer stops printing, there is a small amount of filament oozing downwards from the nozzle for a few seconds. Is it possible that after printing there is some residual pressure which causes filament to creep through the nozzle after the extruder stops pushing. Or maybe there is a blockage in the nozzle which is constricting the free flow of the filament?

I just watched what happened at the end of a 16 hour print. During the 30 seconds after printing finished, the nozzle extruded a 15mm length of filament (See attached photo). So I'm thinking that this may be relevant to my issue.

Posted : 05/08/2022 7:41 am
Diem
 Diem
(@diem)
Famed Member

Yes, it's damp. The steam boiling off the filament is messing with your extruder pressure.

You don't know how new filament has been treated in storage by the retailor or in transit.  Newness does not equal dryness.

Cheerio,

Posted : 05/08/2022 2:53 pm
Razor and AndrewTerry liked
AndrewTerry
(@andrewterry)
Trusted Member
RE: This never used to happen...

Been bitten by this myself.

As Diem says, new does not equal dry. It's worth investing in a dryer (or building one, if you're the handy type).

Posted : 05/08/2022 6:38 pm
Razor liked
Hoof Hearted
(@hoof-hearted)
Active Member
Topic starter answered:
RE: This never used to happen...

I'm surprised to learn that my filament is damp after keeping it vacuum packed with silica gel. I'll put some in the kitchen oven and see what difference it makes. I believe 4 hours and 50C should be ok?

Posted : 05/08/2022 8:02 pm
Razor liked
jsw
 jsw
(@jsw)
Famed Member
RE: This never used to happen...
Posted by: @andrewterry

Been bitten by this myself.

As Diem says, new does not equal dry. It's worth investing in a dryer (or building one, if you're the handy type).

During the height of the pandemic, I converted one of my dryboxes into dual-duty as a makeshift filament dehydrator.

I really have not used it as such, as just after we got a new kitchen toy, the Ninja Cooker, which has a temperature-controlled and timed dehydrate mode.  It also fits a standard 3d print spool quite nicely.

Whenever I suspect a spool is getting damp (more common this summer than in the past) I'll let it dry overnight in the Ninja Cooker.

Posted : 05/08/2022 9:30 pm
Razor liked
Diem
 Diem
(@diem)
Famed Member

4 hours and 50C should be ok?

As long as it's an accurate electric oven this should improve results.

Cheerio,

Posted : 06/08/2022 12:40 am
Swiss_Cheese
(@swiss_cheese)
Noble Member
RE: This never used to happen...

@hoof-hearted

 

Good LucK, I live in the USA and our ovens on average (which don't adjust to celsius will way over cook (Dry) (glass transition) your filament, 35C for 5 hours is plenty, and 35C continuous as you print is superior to drying and then trying to keep the filament dry in a dry box. you have been told.

 

Good luck, do what you want.

 

Swiss_Cheese

The Filament Whisperer

Posted : 06/08/2022 1:11 am
Razor liked
Hoof Hearted
(@hoof-hearted)
Active Member
Topic starter answered:
RE:

I'd already put the filament in the oven and gone to bed before those two replies above were posted. My kitchen oven is a modern digital fan oven and gives a precise temperature. My filament had 8 hours at 50C and was fine afterwards. I've started the same model reprinting. I'll post back in a few hours when I can see what difference there is.

This post was modified 2 days ago by Hoof Hearted
Posted : 06/08/2022 7:43 am
Hoof Hearted
(@hoof-hearted)
Active Member
Topic starter answered:
RE: This never used to happen...

I've taken another photo at roughly the same stage of printing. Although there is a couple of strings, it's a huge improvement.  It was completely string free for the first 3 hours of printing. Maybe the interior of the roll isn't quite dry yet. The room where I am printing is currently 25C and 40% humidity. So I think that's reasonably ok for the filament to be out in.

I'm disappointed that the new roll of filament was so damp when it came out of the packet. I would have thought the manufacturer would take care to ensure that the product is dry at the point they vacuum pack it.

Humidity is a subject I am quite familiar with... I collect good quality acoustic guitars. They need to be kept between 45% and 55% humidity. In my guitar room I have a humidifier and dehumidifier to achieve this. My environment goes between 35% and 65% at different times of the year. In the past, two of my guitars were damaged by humidity before I realised what was going on.

I'm already planning my filament drier. I used to make my own wine. I have a 15W heat pad on which I used to put demijohns to get the fermention process going. That should be a good source of heat. I'm also into tinkering with Arduinos. So I'll have a go a making a PID temperature controller.

So all that's left is for me to thank the people who pointed me in the right direction. I never suspected damp filament, especially when I brand new roll exhibited the issue. Thanks for your help guys. It's much appreciated.

Posted : 06/08/2022 4:37 pm
karl-herbert
(@karl-herbert)
Illustrious Member
RE: This never used to happen...

I concur with @diem and @andrewterry. New does not always have to be dry. If in doubt, dry in a dehydrator or oven.

(selfmade dehydrator for about 25 euros...)

wbr,

Karl

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen.

Posted : 06/08/2022 6:09 pm
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