Clogged BB Core

[SandervG 1,521]

Hi @adshale_de , what TomNagel is referring to I think is if the filament got entangled on its own, like it formed a knot. Preventing any further feeding. Can you confirm if there was any entanglement? (As an example, I pulled an image of the internet:

 

 

Regarding degradation of PVA; do you have any indication of what the temperature of moist is in the area of your Ultimaker? Is there an AC in the area? That it turns brittle is likely to be an indication that it absorbed too much moist. During a print of 3 days this should not happen normally within a 'normal' environment, but perhaps there is something in your printing space which negatively influenced PVA. PVA can do wonders, but unfortunately, it can be sensitive too. 

[adshale_de 0]

I can confirm that it didn't knot up, no. The filament was still loose, and hadn't become taught on the spool. I triple checked this, having had a similar issue where the PLA entangle on an earlier test print, and had stripped out on the feed motor to the AA motor. (This was due to a mistake on my part, rather than a systemic issue).

 

As for the moisture, its possible that air con could have affected it, but doesn't AC actually dry the environment, rather than make it more humid?

 

Humidity is looking like the most likely culprit, and coupled with the constant on-off nature of the model printed, these may have combined to cause the filament to block. Now I know what to look for, I will keep an eye out for any potential problems, and try to prevent them, before something like this happens again.

[kmanstudios 1,120]

2 hours ago, tomnagel said:

Glad you solved the clog. But still interesting to know the root cause. 

The BB core should not clog, also not after many days of printing. However, a minimum flow is needed. How much PVA was in the layers before it failed? If it has to heat up the nozzle tp print a tiny bit of PVA every layer, it could burn and clog. This is however very rare.

Another option (makes more sense) is that there was another reason that there was no flow, for instance entanglement of the filament. Your clog was then the consequence of this.

 

Did you use Cura for slicing? Cura takes care that the not-used nozzle is lowered in temperature.

I have been doing some very delicate prints that have been doing this very thing and it does require cleaning. Our humidity levels here have been very low, around 35% with the arctic blast we got last week and before. And once it starts building up, it keeps cooking it in. I did not think of that....thanks for mentioning it!

[pfordmedia 0]

I am having this same problem right now.  Not only does PVA absorb water like crazy, when it burns it off in the nozzle, any residual water when the nozzle cools down begins to dissolve the PVA into that glue-like substance inside the nozzle, thus creating the clog. I'm going to try 250C with a hot pull and see if I can pull all that burnt stuff out. Anybody got any other ideas?

[Brulti 177]

@pfordmedia Let it sit for a while. I mean, turn the temperature up to 250°C, then go do something else and come back later. If the clog is big, it will be slow to soften, and the heat needs to diffuse through the clogging. I had that problem with PVA and PLA, after some failed prints. I had to wait for 15-30 minutes, with the temperature of the printcore at about 230°C. Once the heat diffuses, the clog will start melting little by little and drip out of the tip of the printhead. Usually, when I see a nice big drop of melted material hanging from the tip of the printhead, I can then do a cleaning and remove any trace of burned material inside.

 

Also, you might want to get a drybox for your PVA to keep humidity at a constant low level, especially for long prints (ie more than 24h). You can find some through your reseller, I gues,s or make your own. There are several DIY instructions around, including a nice easy one by @ultiarjan. You can find it somewhere here, on youmagine, or on thingiverse by looking for 'drybox'.

[pfordmedia 0]

@Brulti I just tried this for about an hour and a half to no effect.  It seems like it's just so burnt inside there that it's literally like a rock and won't even melt. I'm out of options... I really don't wanna shell out more money for another printcore, but nothing seems to work.  Why is PVA such a PITA? short of putting it in a vice and drilling it out of the bowden tube with a tiny drill bit, I don't know what else to do...

 

[kmanstudios 1,120]

This is what I did to get out of this very same mess:

 

Started at high temp but pumped filament in and out of the BB core. I did not use PVA as it was not stiff enough.

Then I would start to do hot pulls. Push the filament down into the core for 2 seconds and then pull it out. Repeat a bit doing this. Then do a cold pull. Keep doing this and it will cut loose. If needed (And I have done this too) use something like an airbrush needed to kinda poke it a bit. Just make sure not to push through the nozzle eventually and put a flare into the tip, ruining the BB core nozzle.

 

It took me three and a half straight hours one time to get it cleared and working again.

[gr5 2,172]

AS A LAST RESORT, you can disassemble the core and work on the nozzle by itself.  Either burn it all out at 300C (if brass starts glowing red hot then that's much too hot and let it cool as at that temperature it's extremely easy to squish the brass into a new shape).  It's very easy to destroy the heat break so watch this video first:

 

[tomnagel 126]

Disassembly of your print core is not advised and never necessary. 

With hot pulls and cold pulls it is *always* possible to get your print core going again. 

Cold pulling with polycarbonate works extra good if you have that.

please believe me: PVA printing is reliable on your UM3, if you stick to Cura profiles, UM material and keep ambient relative humidity below 50%. 

 

[Dim3nsioneer 557]

Better keep it below 35% r.h. and never let the clogged PVA carbonize so far you cannot melt filament anymore which you push from above at print core cleaning.

[pfordmedia 0]

@tomnagelI appreciate and hear what you're saying. But I'm afraid you don't know what I'm dealing with. I just did a PLA hot push into the PVA hotend at 270. Let the nozzle cool down to 35 and then tried to cold pull it.  It might as well have been welded to the hotend because it snapped off close to the nozzle, and nothing came with it.  I just dissassembled the core and the nozzle is filled with black, burnt plastic that has most assuredly carbonized (which is the hardest element on earth).  It's literally a rock inside the nozzle. 

I always use Cura profiles, the PVA is UM.  Once I get a decent way to store the PVA both while printing and storing hopefully it will eliminate this problem. My experience with PVA thus far has not been a good one, to say the least (although the prints I did when the roll was new were quite good).

 

And @Dim3nsioneer yes I think the extreme temps like everyone suggests is a terrible idea since all it seems to do is burn the material and harden it to the hotend. 

[ultiarjan 1,223]

25 minutes ago, tomnagel said:

PVA printing is reliable on your UM3, if you stick to Cura profiles, UM material and keep ambient relative humidity below 50%. 

 

While I agree taking apart a core should probably only be done as a last resort, I read between the line here it's the users own fault if a failure occurs when not using UM material. I think we've seen plenty of users with issues that did use UM materials, on the other hand, I myself have never had any serious issue with PVA, and I'm using cheap Makerpoint homebrand PVA. Seems to me environment plays a big part in the issue. I do store and print from a drybox.

 

 

[SandervG 1,521]

14 minutes ago, pfordmedia said:

cool down to 35 and then tried to cold pull it.

 

Was there not a reason why you should not let it cool too cold? I thought so but I seem to have forgotten exactly why.. 

Secondly, I am not saying this would have changed the outcome significantly, but I think CPE functions better as cleaning filament than PLA, does it not?

[pfordmedia 0]

@ultiarjan Seems like I read somewhere that UM PVA has less alcohol content which means it doesn't absorb as much moisture, but gets stickier and other PVA isn't as sticky, but absorbs more moisture.  I could be just trippin though.  Looks like if I want to be successful I'm going to have to take better control of my print environment.  That seems to be a common theme.

 

@SandervG

1 minute ago, SandervG said:

 

Was there not a reason why you should not let it cool too cold? I thought so but I seem to have forgotten exactly why.. 

Secondly, I am not saying this would have changed the outcome significantly, but I think CPE functions better as cleaning filament than PLA, does it not?

 

Oh definitely, but PLA was what I have on hand.  And I would have let it cool down more, but 35 was pretty close to ambient temp so that's why I pulled it then.

[gr5 2,172]

35C is not the right temperature for a cold pull.  For PLA the temp is around 95C.  Between 90C and 120C for sure.  I don't know what the temp would be for PVA and PC.  Probably just above the softening temp of PVA which is 30C hotter than for PLA so maybe around 120C?

 

It would help if you read about cold pulls in detail.  So the procedure is to heat the nozzle well above the melting point of the materials involved - so 180C is pretty good for PLA and PVA.  Then push in solidly to make a good bond.  Then cool to the magic temperature.  If you pull it out and it comes out with almost no force then you didn't cool enough.  If it takes more than about 10 pounds force then you cooled too far.  I usually go "too far" and then crank the heat up to say 130C while pulling upward the whole time until it suddenly gives.  I note that temperature where it happened and next time start a little lower than that.

 

For nylon I found 120C is about right.

[pfordmedia 0]

1 minute ago, gr5 said:

 I usually go "too far" and then crank the heat up to say 130C while pulling upward the whole time until it suddenly gives.  I note that temperature where it happened and next time start a little lower than that.

 

This is a great idea, I may give this a try. I was making a strong bond, but I think I cooled too much. Problem is, hotpull doesn't do anything either. Which makes me think the outside of the nozzle looks like the outside of it, with hard, black carbon cakes onto it.

[gr5 2,172]

Also the instructions for cold pull tell you to put the head in the corner.  I hope you did that because if you pulled hard enough to break PLA that's about 100 to 200 pounds (50kg) of force which is enough to bend your thin rods.  hopefully you didn't bend your thin rods (the ones through the head).  The idea is that you put the head in the corner so with 10 to 20 pounds force you don't bend the thinner rods through the head.

 

I guess for us people who have been talking about cold pulls for 4 years we just assume you know what we are talking about.  There are many videos that show how to do this including Ultimaker has some videos.

 

The point of the cold pull magic temperature is you want the filament softened a bit so it can pull it out but hard enough that it all comes out in one piece.

 

[pfordmedia 0]

@gr5 Yes, head was in the corner when I pulled and rods are fine. I'll keep trying.

[pfordmedia 0]

Also, @gr5 and @SandervG what's the right temp? One says it needs to cool down more, the other says it should be higher for a cold pull. Cold pull to me has always meant close to room temp.  When you swap a printcore, it doesn't heat the core, but when you swap materials, it does so what gives? And before you ask, yes the firmware is up to date.  It seems to me that nobody knows what the hell is going on. Ive worked with numerous printers for almost 3 years now and never have I had a problem like this until PVA came into my world (probably my own fault for letting it absorb moisture though).

 

I don't know, maybe I'm just frustrated. I may leave it and come back to it in a few days.

[kmanstudios 1,120]

I do cold pulls at about 90°-100°C for PLA. For hotter temp materials about 120°C -130°C.

[tinkergnome 927]

I cannot help with the un-clogging, but one thing i noticed:

 

If you don't use the BB core / PVA regularly, it's important that any PVA residues are removed between the uses (or if you put the printcore in the shelf).

 

Usually i remove the PVA spool as soon as the print is finished and just feed some PLA through the BB core. I never had a problem again since then.

 

[tomnagel 126]

13 hours ago, ultiarjan said:

 

While I agree taking apart a core should probably only be done as a last resort, I read between the line here it's the users own fault if a failure occurs when not using UM material. I think we've seen plenty of users with issues that did use UM materials, on the other hand, I myself have never had any serious issue with PVA, and I'm using cheap Makerpoint homebrand PVA. Seems to me environment plays a big part in the issue. I do store and print from a drybox.

 

 

 

Please don't put words in my mouth. I mean my statement literally, and I don't mean to imply anything else. Users following my advice profit from thorough testing that takes place within Ultimaker. Users who make other choices have to find out stuff for themselves.

 

[tomnagel 126]

14 hours ago, pfordmedia said:

@tomnagelI appreciate and hear what you're saying. But I'm afraid you don't know what I'm dealing with. I just did a PLA hot push into the PVA hotend at 270. Let the nozzle cool down to 35 and then tried to cold pull it.  It might as well have been welded to the hotend because it snapped off close to the nozzle, and nothing came with it.  I just dissassembled the core and the nozzle is filled with black, burnt plastic that has most assuredly carbonized (which is the hardest element on earth).  It's literally a rock inside the nozzle. 

I always use Cura profiles, the PVA is UM.  Once I get a decent way to store the PVA both while printing and storing hopefully it will eliminate this problem. My experience with PVA thus far has not been a good one, to say the least (although the prints I did when the roll was new were quite good).

 

And @Dim3nsioneer yes I think the extreme temps like everyone suggests is a terrible idea since all it seems to do is burn the material and harden it to the hotend. 

Hi @pfordmedia

35 degrees for a cold pull is too low. The material is much too hard to pull out, and will snap like you described.

Please follow the instructions on this webpage.

 

[pfordmedia 0]

1 hour ago, tomnagel said:

Hi @pfordmedia

35 degrees for a cold pull is too low. The material is much too hard to pull out, and will snap like you described.

Please follow the instructions on this webpage.

 

 

Thanks for clarifying for me. I will try a cold pull at around 90 or so.

 

And @tinkergnome I actually did this yesterday with one of my non-clogged BB cores out of an abundance of caution and it seemed to work well! Thanks for the tip!

 

I'm going to be honest (and no I shouldn't have done it), but last night I just took a very small drill bit and drilled through the gunk in the nozzle, it all game out fine, but I have yet to test it.  If nothing else, it will make a cold pull much easier and clear the last little bits down in the tip of the nozzle.

[pfordmedia 0]

Also, I would like everyone to notice that no where in the cold pull article are temperatures mentioned for when the pull should occur, it just says "let it cool down". Perhaps Ultimaker could publish a table for this?