Da Clumsy Noob discovers a way to hot pull PVA midprint

[kmanstudios 1,120]

PVA....Cannot live without it, cannot shoot the nozzle when it clogs....

 

Requirements:

1. Patience aplenty
2. Airbrush needle or something like that with a nice teeny tiny point.

 

Issues to overcome:

1. When printing and humidity strikes midprint, especially on long ones like I do on a constant basis
2. Humidity will clog the nozzle as PVA pops and crackles, creating a carbonized mess inside as well as outside the nozzle
3. If you pause the print to try this, it will not work because the nozzles cool down and you cannot adjust the temp more than +- 25¯C. By this time, the material is too cool to do anything with. *Are you hearing this firmware devs?

 

OK, now this is an issue that has plagued me ever since I started printing. AND continues to plague the industry as a whole. It is an unavoidable evil that must be dealt with. It does not matter whose PVA you are using.....it will happen.

 

The main warning sign is when the material is not printing like a solid wall, but starts to get very lacy. At this point, it cannot hold the material it is supporting and you may not discover this until the print is done and you just have a lot of time, material and expense down the drain.

 

SO! what to do, what to do.....

 

For some reason it occurred to me tonight that the solution (klugey as it may be) is to fake out a material change. Even if you have a brand new spool of PVA in there, if there is a clog, it will still not give full PVA service to the supports.

 

So, here are the steps ?

 

1. Go to the 'tune' menu and initiate a material change. This will heat the nozzle to the proper temp and hold it. It will also pause all printing ops and step you through all steps of replacing materials.

2. Once your material unloads, leave it at that stage. This will keep the temp up while not letting anything continue until you go to the next step.

3. Poke the heck out of it with the airbrush needle or something similar. Just be careful not to poke out the delicate nozzle tip.....

4. Take older leftover PVA, like those bits when it was changed out and leaves the parts that were in the bowden tube, and push it though.

5. Rinse and repeat until you get a clean thread of PVA going through.

6. Reload your PVA and start back up.

7. As it reloads, you will see a nice thread of material squishing out.

 

This is not as good as a hot and cold pull, but it can save a long print. It should also be mentioned that this is also available for the S5 as well.

 

The best solution would be something to allow a pause and temp control to the extremes that hot and cold pulls require to really get it out. *Ahem* firemware devs ?

 

Some may say that keeping the nozzle clean is the answer.....it is until you have a really long print, the humidity rises and starts to degrade the printing of PVA during that time. It can happen. It has happened to me as I do these massively long prints. Start with a clean nozzle and 5 days later, humidity strikes, and the lace pattern appears as the PVA starts to underextrude.

 

So, happy PVA supports all around fer everyone!!

 

WOOHOO!!!

Edited August 3, 2018 by kmanstudios
Added information in steps 1, 2 and the end of the procedure statement.

[Dim3nsioneer 557]

Nice procedure. Just keep in mind that during material change the position of the print head is not optimal for pushing or pulling (not in an corner). You might bend the print head axles if not careful enough.

Edited August 3, 2018 by Dim3nsioneer

[kmanstudios 1,120]

I have only had an issue with pressures during cold pulls. But the needle helps to alleviate any pressures on the axles. But it is a very important warning as some may not be aware. Thanks! :)

[kmanstudios 1,120]

Now that time has passed, this is the difference it made in the print quality of the PVA. Plenty of time before it got to crucial areas and PVA does have a nice tendency to recover on this type of thing.

[JohnInOttawa 104]

Great workaround!  I will check around to see what needle spec it would take to safely enter that nozzle.

 

The comment on the rod bending prompted me to start a separate thread on a print core cleaning stand. I'm wondering if your technique could be incorporated into the design considerations for that device.

 

Gotta love the sharing here!

John

[kmanstudios 1,120]

Ya know....now that you mention a printcore cleaning stand......(see your thread for further news ? )

[gr5 2,167]

I have used gauge 28 acupuncture needles but gauge 28 hypodermic needles are so much better because it is tubular with sharp edges that can scrape the gunk off the inside of the tip of the nozzle.  For several years I would ship a free one for all new people to my store but my supply has run dry (regulations made it difficult).  But a acupuncture needle works pretty well.

 

It just occurred to me that maybe I should cut the pointy tip off acupuncture needles!  To make them more flat.  Hmm.

[Nicolinux 288]

@kmanstudios Respect for your patience with PVA... For me almost every print with PVA fails and I avoid it now as much as possible. But if I have to print with it again, I will make sure to remember your tip!

[kmanstudios 1,120]

Cool...The strange stuff I print almost always requires PVA for the spindly nature of most of my prints and far out balancing that would break if using standard material supports.

 

i do hope it helps ?

 

 

[kmanstudios 1,120]

@gr5 made a suggestion to include additional info for clarity. This was added to steps 1, 2 and the end of procedure statement.

 

T'anks me hearty!!

[sharahamo 0]

Sorry i know this is old thread. does this basically mean I should do hot pull mid print? I dont get your point 

4. Take older leftover PVA, like those bits when it was changed out and leaves the parts that were in the bowden tube, and push it though.

[kmanstudios 1,120]

2 hours ago, sharahamo said:

I dont get your point 

Then perhaps you have not had the PVA clog in the middle of a long print?

[sharahamo 0]

I have this problem as currently being discussed here, and I am trying every possible method to prevent this problem. So far nothing works. I may need to resort to using the box

 

[kmanstudios 1,120]

Yeah, my PVA failures went WAAAAYYYYY down once I started to use a drybox. Polybox in my case.

 

But, clearing the nozzle in midprint is still required once in a long while if I do not do good maintenance.

[sharahamo 0]

@kmanstudios i am printing now and the PVA is not extruded. The material seems okay, not too soft. My  concern is I am printing PVA at certain parts only i.e. roof and floor of support and small holes,  so the gap between the use of PVA and PLA can be big. DO you think it might causes the blockage? 

 

Is it better if I use all PVA as support rather than using PVA as roof/floor support only? 

 

Eg here https://www.simplify3d.com/support/materials-guide/pva/  it says that the cons of using PVA is 

• Greater chances of clogging if the nozzle is left hot when not extruding

Edited February 25, 2019 by sharahamo

[kmanstudios 1,120]

3 minutes ago, sharahamo said:

DO you think it might causes the blockage? 

No, I am thinking that this is because you need to really do hot and cold pulls before you -print to make sure the core does not have blockage. But, if you are midprint, use the method detailed to get the PVA to print.

 

5 minutes ago, sharahamo said:

Is it better if I use all PVA as support rather than using PVA as roof/floor support only? 

This would be a case by case basis. In my stuff, mostly organic, it is not feasible. I tried it once and it just failed miserably. This would be something you would be able to evaluate.

 

6 minutes ago, sharahamo said:

Greater chances of clogging if the nozzle is left hot when not extruding

This is true, but the core should cool between usages of the materials. What would cause an issue is if it clogs, does not extrude when hot and cooks the PVA even more.

[sharahamo 0]

1 minute ago, kmanstudios said:

No, I am thinking that this is because you need to really do hot and cold pulls before you -print to make sure the core does not have blockage. But, if you are midprint, use the method detailed to get the PVA to print.

 

I have done this and it does not work. I do this every time the print fails because the nozzle will be clogged. The brim (PVA) looks really nice but then it goes down the drain.

3 minutes ago, kmanstudios said:

This is true, but the core should cool between usages of the materials. What would cause an issue is if it clogs, does not extrude when hot and cooks the PVA even more.

The thing is I have PVA being used for small holes in between the floor and the roof, so probably they don't have time cool down properly because it's being constantly used but in a very very small amount. 

 

I feel so hopeless and wasted a lot of materials. 

[sharahamo 0]

@kmanstudios I was wondering if you could help e suggesting the best setting of cura for this model attached. I have been having real problem even when I kept the material dry, mostly because of the material PVA grinding, mostly because PVA is being used every now and then in very little amount, in between roof and floor. 

 

 

MainBody_v1.0.stl

[kmanstudios 1,120]

I know you got the PVA, but what is the other material? Layer setting? Etc..... UM Machine?

 

edit: A project file and version of Cura you are using would be helpful.

Edited February 27, 2019 by kmanstudios

[kmanstudios 1,120]

One thing to keep in mind is that you may need to do some simpler tests to iron out your PVA issues. PVA is a pain to print with. My environment is very dry compared to some places. And, depending on your ability to create a printing environment with humidity control, it may be a great challenge. I know some people here that are far more experienced than myself that just cannot get the results I get due to their local climate. I am just not in a high humidity environment. And, I still have to clean my system periodically because, well, sometimes, humidity can change.

 

I can see the printing change in a matter of hours when there is an upward change in humidity due to weather conditions such as storms moving through, etc.

[sharahamo 0]

@kmanstudios My apologies, forgot to mention the details. I'm using Ultimaker 3. Material 1 is Ultimaker PLA and Material 2 is Ultimaker PVA. I am printing at

Layer height 0.2mm

Wall and bottom/top thickness 1.2mm.

Infill density 20%

 

I have a humidity indicator in my room and it's quite low actually, around 33%. The material isn't very soft and pliable, almost like the PLA, making me think that the humidity may not always be the case. I am using the laest Ultimaker Cura version 2.6 Attached is the project file

UM3_MainBody_v1.0.3mf

 

When the PVA is extruding well, I also have problem where the material is not sticking to PLA. I am trying to figure out the best configuration of PVA, i.e. the flow, temp, speed, layer height

Edited February 27, 2019 by sharahamo

[geert_2 557]

If you suspect "not enough flow" is one of the causes, maybe you could try a (bigger) priming tower, or print a dummy block in PVA next to the real print, to keep more flow going through that print head? So it is always well purged? Try the idea on a small piece first, before doing a large job.

 

[kmanstudios 1,120]

5 hours ago, sharahamo said:

I have a humidity indicator in my room and it's quite low actually, around 33%

That is dryer than my environment.

 

5 hours ago, sharahamo said:

I am using the laest Ultimaker Cura version 2.6 Attached is the project file

Typo? 3.6?

 

ok.....I want to take a look since I do not have these issues and I did look at the file and it should be a fairly easy print. Have you tried changing out the BB core?

[kmanstudios 1,120]

OK, this is what I would expect to print properly.

 

Keep in mind that I use Matterhackers PVA for the most part. I keep the UM PVA for the really needed prints. So, this will show a mismatch on the PVA, but you can override that on the printer.

 

I rotated the body upwards so it does not lay down flat. This is my personal preference. Not a 'more correct' way of printing the object.

UM3E_MainBody_v1.0.3mf

[sharahamo 0]

I found out the solution to my problem... Is by using a new set of PVA. The one that I used before has been opened for 8 months, and no matter how much I dry it out it won't work. When I use a new one, voila! I should make it a habit to by 255g instead of 750g PVA. I am throwing away £80 worth of old PVA now...