Clogging BB printcore (PVA)

[toilet-ovule-add 0]

Regulary my BB printcore gets clogged. Even when printing for hours fine it can get clogged during the middle of the night making the feeder grind the filament till it snaps of.

 

When i do a hot and cold pull the filament comes out clean when retracting the PLA or cleaning filament. (Used both).

But when making a hot pull quite some blackened filament comes out the nozzle. Also while printing, sometimes there are some black spots of filament in the PVA support structure. 

 

I filmed the extruded blackened filament while making the hot pull.
 

http://www.youtube.com/watch?v=Jvl-ChWhDME

 

Any ideas what is causing this and how to prevent or to resolve this?

 

[kmanstudios 1,120]

When I clean my BB cores I do the following:

 

1. Several hot pulls

2. Followed by some 'plunger' actions of pushing and pulling the filament (cleaning or otherwise)

3. Then I will do a cold pull.

4. Rinse and repeat as needed.

 

I find that the PVA in the BB core can really get hardened to the walls and take a bit of work to get them off if not cleaned regularly. I am bad about this as I just have a constant rollover of prints to get on and off.

 

The problem starts (usually) with the humidity levels in the printing area. It has abated quite a bit since using a drybox to keep the spool as dry as possible. But, after it leaves that and gets out of the feeder, humidity can get to it. Especially at night when temps drop and condensation is happening.

 

And, I will not stop the rinse and repeat cycle until I get a clear stream of filament without pops and crackles. You may not see the material in the filament, but if it pops and crackles, it is picking up micro amounts of leftover material. And, just as your pic shows, have had the same results, but much larger amounts of discolored material come out. It is satisfying to see it finally break loose,

[toilet-ovule-add 0]

Thanks, 

 

Although the humidity is low, PVA seems to be quite hygroscopic so in the long term it will absorb moist.

After usage i do store the filament back in a zip-lock bag with silica bags.
Is the absorbed moist causing the burned/discolored material ? The PLA seems not to have this issue, only PVA over and over again.

A dry box is not an option for me due to the lack of space available behind the printer. The printer is stored in an Ikea PAX closet. When closed it keeps the temperature stable. But there is not enough space behind the printer due to the depth of the closet. It would be great if a cover came available this would fit over the spool holders to keep the filament dry.

[kmanstudios 1,120]

4 minutes ago, toilet-ovule-add said:

Thanks, 

 

Although the humidity is low, PVA seems to be quite hygroscopic so in the long term it will absorb moist.

After usage i do store the filament back in a zip-lock bag with silica bags.
Is the absorbed moist causing the burned/discolored material ? The PLA seems not to have this issue, only PVA over and over again.

A dry box is not an option for me due to the lack of space available behind the printer. The printer is stored in an Ikea PAX closet. When closed it keeps the temperature stable. But there is not enough space behind the printer due to the depth of the closet. It would be great if a cover came available this would fit over the spool holders to keep the filament dry.

Yeah, it is the PVA being so hrygroscopic. Sponge worthy even.

 

But, if you have the printer stored in a closet, maybe you get large bags of rechargeable desiccant to put in there? Nothing will ever be purely able to prevent the absorption of moisture unless it is a completely enclosed system.