The Clumsy Noob Learns a bit more about PVA and the BB Core

[kmanstudios 1,120]

So, before I tell the tale of woe (3.5 hours cleaning the BB Core) let me first say that so far, in 6 months, I can trace 99% of my errors to either user error (self-inflicted) or Environmental (No real control in current living setup).

And, let me say that PVA can be a bit more of a problem than the average filament, but really, not by much. It is just quirky.

Also, let me say that thanks to tomnagel, geert_2, gr5, SandervG, fbrc8-erin and Team Ultimaker for their support, answers, clarifications/corrections to my attempts to share knowledge and general support to enhance the experience.

I would also like to add, to all the people newer than myself, failure teaches more than success as success does not really let you know when you are just lucky. Case in point:

I have been printing with the BB core as well as dual colors for more than 2,000 hours now. But in another thread, gr5 made some interesting observations about my PVA pic in another thread and offered some insight I had not considered. In another thread, tomnagel corrected me on my misunderestanding of the temps to be used. Mostly what I learned last night was I had been printing a lot with luck on the PVA/BB Core side of things.

But, part of it was getting temps and such straight as I had conflated a few of them and set straight by some of the above listed. I would also recommend bookmarking the following links as returning to the reference will prevent this type of mix-up....or, you just may be better than myself at such things.

Ultimaker Core-Atomic Pull:

Ultimaker Hot Pull/ Atomic Pull

Fbrc8 Resource for additional info:

Fbrc8's Temps and methods

Now, I listed all these resources because I did crank up the temps to the higher ones listed by Fbrc8. I do not know if this creates an issue with the BB core or not, but it was seriously clogged and I am hoping that someone at Team Ultimaker will put a fine point on this for all us Noobs or, even the not so Noobish.

The one thing that really got things moving was I read in the Fbrc8 posting that there can be applied a 'pumping/plunger' type motion with the PLA filament while cleaning. Also, make sure you have the printhead in the corner and not in the middle. You can pull rods loose or bend them; but the corner will give it a lot of support for serious action with the filament. And, I had to get REAL serious.This proved to be essential as I could see it force a release of some really black gunk that had built up over time for a variety of reasons. I cannot emphasize enough how much the pumping action helped.

I had also removed the BB core to do a few two color PLA prints and it must have really clogged during that time. How? It was not in use. Maybe just residual junk getting moist (even burned PVA can absorb moisture) and just making it dry even more firm when heating back up.

Best I can figure is that (A) I have bad climate control in this apartment and the humidity did build up. This probably made the filament waste still in the nozzle to glue itself even tighter to the metal. (B) My previous methods (Low temps and no pumping on the filament) did not thoroughly clean the nozzle and there was just a build up over time that kept re-glueing itself to the metal. It did not 'bond', but it sure made it hard to get out.

Many, many hot pulls with the pumping action. Many, many Atomic Pulls until I could not see any black or schmutz on the filament when pulled out, as well as getting the shape of the nozzle on the end as pictured in the above references. I could hear the PLA crackle as it began to cut loose the PVA. I do not ever remember PLA crackling, so this meant that I was hearing loosinging PVA cutting loose and mixing with the PLA. And lawdy, mercy me, I used about a full meter of PLA scraps to get it cleaned!

[kmanstudios 1,120]

Continued, because I am long winded...

Patience is required. These are hugely delicate mechanisms and not like buying a smartphone or tablet or even a high end PC. It does require proper intervention (We called it PMS in the Navy 35 years ago. Preventive Maintenance Service) to keep the parts running smoothly.

Also, because it is a delicate system on emerging technology, there will be failed parts on a new machine every now and then. But a bit of diligence, research and patience, you can rule out whether that is the case.

And finally, do not discount luck or mistake it for actual knowledge. I have been corrected many times and it is great to learn more and more. It is also why I say that there are no stupid questions. Ignorance is not stupidity, it is just not knowing. And, we all start out ignorant and will all make mistakes as we learn.

But, yeah, have patience with the cores. they are your friends and allies and just need a bit of loving, not frustration/anger because it does not behave right away or to unrealistic expectations.

Also, as any corrective information comes in, I will edit this original posting to keep it fresh. No need for anybody to read too many posts to get to proper information.

Edit/Added as Per tomnagel:

I'd like to make a few additions:

* I don't think that it is necessary to clean out a well maintained BB core before storing it. I say "well maintained", because maybe in your case, the thing was already almost clogged when you put it away. I think even in the case the PVA in the core gets moist, the printer will push that out during the next time it primes. Absorbing moisture only makes the filament soft, which is an entirely different thing than (thermal) degradation. Of course I'm not saying that cleaning it before storage is a bad thing, but I think it is not worth the trouble.

* We have done a large test with 22 printers for more than 2000h. All with different preventive maintenance intervals. Our conclusion (yet to be published, so consider this a preview): the advised cleaning interval is 400h. Reason: during normal use, there is some build-up of degraded PVA on the inner sides of the nozzle. Even the printers which we gave *no* preventive maintenance stayed open, but the build-up will increase the chances of clogging when you have an incident, and probably the flow resistance increases as well, though this was not measured. This research concluded 400h was the optimal interval.

* Just by trying, we found that for some reason, clear PolyCarbonate (PC) works very well for cleaning the BB core. In many cases, the brown build-up is extruded when PC is pushed through the nozzle, while PLA is just extruded and leaves the brown stuff behind. Hot pulls at 270degC, cold pull at 135degC.

* Last but not least a remark about hot pulls: timing is of the essence. To be able to "fish out" the clog or dirt, you need to press the filament in the print core not too long and not too short. Too long will melt too much of your stick, and all the molten stuff stays inside including the dirt. Too short, and your stick has not become soft and sticky enough. You will learn by doing, but 1-2secs covers it I think.

Edit: Added Per fbrc8-erin

Clear nylon works really nicely--

Edited June 8, 2017 by Guest

[fbrc8-erin 272]

I had also removed the BB core to do a few two color PLA prints and it must have really clogged during that time. How? It was not in use. Maybe just residual junk getting moist (even burned PVA can absorb moisture) and just making it dry even more firm when heating back up.

If you're not going to do anything with the BB Core for a while, I do recommend pushing PLA through it or doing an Atomic Method to clear it before you set it aside. PVA left in the nozzle tip will degrade over time, which is why when the Cores are tested before leaving the factory, they're tested with PLA.

[kmanstudios 1,120]

I had also removed the BB core to do a few two color PLA prints and it must have really clogged during that time. How? It was not in use. Maybe just residual junk getting moist (even burned PVA can absorb moisture) and just making it dry even more firm when heating back up.

If you're not going to do anything with the BB Core for a while, I do recommend pushing PLA through it or doing an Atomic Method to clear it before you set it aside. PVA left in the nozzle tip will degrade over time, which is why when the Cores are tested before leaving the factory, they're tested with PLA.

That is a great addition of information. But as I refine my process, I am going to be doing a bit more preventive cleaning, and as you suggested, I will also clean cores before storing, even for a short time. I had only been printing for two days with the dual PLA in AA Cores. I guess that was enough time to FUBAR the core into not working at all upon restarting. And, with gr5's input on a previous pic, I can now see that it was clogging up while in use.

But, yeah, the not cleaning before storing did make it fail. Working great now thanks to all the input from youse guys

[tomnagel 126]

@kmanstudios Thank you for sharing your experiences, and summing it all up.

I'd like to make a few additions:

* I don't think that it is necessary to clean out a well maintained BB core before storing it. I say "well maintained", because maybe in your case, the thing was already almost clogged when you put it away. I think even in the case the PVA in the core gets moist, the printer will push that out during the next time it primes. Absorbing moisture only makes the filament soft, which is an entirely different thing than (thermal) degradation. Of course I'm not saying that cleaning it before storage is a bad thing, but I think it is not worth the trouble.

* We have done a large test with 22 printers for more than 2000h. All with different preventive maintenance intervals. Our conclusion (yet to be published, so consider this a preview): the advised cleaning interval is 400h. Reason: during normal use, there is some build-up of degraded PVA on the inner sides of the nozzle. Even the printers which we gave *no* preventive maintenance stayed open, but the build-up will increase the chances of clogging when you have an incident, and probably the flow resistance increases as well, though this was not measured. This research concluded 400h was the optimal interval.

* Just by trying, we found that for some reason, clear PolyCarbonate (PC) works very well for cleaning the BB core. In many cases, the brown build-up is extruded when PC is pushed through the nozzle, while PLA is just extruded and leaves the brown stuff behind. Hot pulls at 270degC, cold pull at 135degC.

* Last but not least a remark about hot pulls: timing is of the essence. To be able to "fish out" the clog or dirt, you need to press the filament in the print core not too long and not too short. Too long will melt too much of your stick, and all the molten stuff stays inside including the dirt. Too short, and your stick has not become soft and sticky enough. You will learn by doing, but 1-2secs covers it I think.

[kmanstudios 1,120]

Thank you tomnagel for the added information. I had no idea you could use PC on the BB core for cleaning and that much heat. I was worried about going up to 250°C from the recommended of 230°C on the Ultimaker site. But, I had to so I could get the charred bits out. Thank you for confirming I did make more damage.

I ran out of clear PC (bought 3 rolls and one was actually black...spool says transparent, box says so, it was just a goof and not complaining) and I would think Black would be difficult to see the char and such.

Do you have another recommendation for cleaning the BB core at high temps? I do have some clear nylon, ABS, etc.

And, I do think that the lower temps I had been using, for whatever reason me addled brain was thinking, did leave a lot of stuff behind as I would bet it had about 1,000 hours since the last cleaning.

And lastly, I did follow directions (And not the 'Tim the Toolman approach which is the norm'...just skim and tear into it.....) on the timing for the hot pulls. I did the old '1 Mississippi', 2 Mississippi' before pulling it out.

Edited June 7, 2017 by Guest

[fbrc8-erin 272]

Clear nylon works really nicely--I'd pick that over ABS. It doesn't burn the way ABS does.

[kmanstudios 1,120]

Clear nylon works really nicely--I'd pick that over ABS. It doesn't burn the way ABS does.

 

Roger that!!

[geert_2 557]

On my two UM2 (non-plus) I do atomic pulls more gently and with less risk of damage, as follows:

- Put print head in a front corner.

- Remove old filament, remove bowden tube, insert a piece of filament used as cleaner, heat nozzle to appropriate temp,

- Gently push filament manually through nozzle, until it's a nice stream.

- Dial nozzle temp to zero.

- Gently push a bit more, but not too much.

- Then do a small manual retraction of a few millimeters: this takes the pressure off the half molten filament, at the border between nozzle and teflon coupler, and makes it easier to pull out the filament later. Especially if the coupler is getting worn out. Otherwise a thick blob or lip would form, which makes pulling it out very hard.

- Cool the nozzle with compressed air (if you have an oil-free compressor!!!), or just let it cool down, or use your lungs as compressor.

- Let it cool to room temp. This deeper cooling makes the filament shrink more, and helps pulling dirt loose from the nozzle walls.

- Wait a bit longer, so the inner core of the filament too has time to cool down to room temp.

- When at room temp, gently wiggle and rotate the filament. Very often, with a snapping sound it will start rotating. Always do this wiggling and rotating gently, without brutal force.

- Then heat up the nozzle again, to about 80°C for PLA (other materials require other temps, try what works). Keep gently wiggling and rotating the filament while warming up.

- And now you can pull it out, almost without any force.

In this way, it pulls out as much dirt as with the traditional atomic pulls (=pulling with brute force), but there is no risk of bending any rods, or of displacing the nozzle or telfon couper. So it works much more gently, with for me equal results.

The main differences with the traditional atomic pull are: first the "small manual retraction" when cooling the filament, then deeper cooling untill room temp, and then the wiggling and rotating before and while heating the nozzle up again, and pulling much more gently. It is the rotating and wiggling action that does most of the cleaning here, not the pulling.

This works very well with PLA and Ultimaker nylon, but less with flexible filaments like NGEN and ABS, which tend to break at the edge of the hot-cold transition. So I use PLA or nylon to clear out NGEN residu.

I do not know if this method would also work for the UM3? Maybe one of the UM3 developers could shine a light on wether such rotating action while doing an atomic pull is recommended or allowed? I don't know how fragile or robust the new cores are, and how well they would absorb these forces?

[tomnagel 126]

@geert_2, I think you can use this method on an UM3 as well. However, I see no benefits.

If you position your print head in a corner according to instructions, it's virtually impossible to break or bend anything.