Ultimaker PVA

[rachael7 73]

1 hour ago, MobyDisk said:

I want to know why we all have such different experiences.  Could someone post a 3MF file and we can all test print the exact same model with the same PLA and the same PVA, and post videos of the print?

My working theory is that it is not moisture which is giving people different experiences. I mean yes, moisture can and will cause major issues and different results, and that is certainly some of the cases; but I think there are other overlooked aspects that could be at play as well.

 

PVA, when exposed to relatively modest elevated temperatures (over 55C) for a long period of time (a day or so, I think), will crystalize. Once it does, it doesn't un-crystalize by drying, humidifying, or anything else that I'm aware of. Crystallized material will still print, but it will be extremely brittle (the issue I ran into continuously) and not feed well.  55C is a temperature that could easily be reached in a non-climate-controlled warehouse in the summertime, in some locations, and it is my theory that some rolls have been exposed in that way, prior to ever getting to the customer, making them too brittle to use.

 

I even had two rolls of the stuff where I observed a brittle spot a few cm long on each wrap of the spool.  I hypothesize that those spools were exposed to direct sunlight in the warehouse (or somewhere on the journey) and the part visible through the window in the box got heated just enough extra to embrittle only in that location.

 

Another factor that makes for such different experiences is the presence or absence of the Material Station. It has a tortuous filament path and brittle filament that might work okay feeding from a spool holder can and does snap in the long, winding path through the material station.

 

Of course, that's where things get really ugly. Broken filament fed from a spool holder is a nuisance, but there's a decent chance the machine will pause for a new roll and the print can be recovered. But when it breaks in the material station, little pieces can get jammed in inaccessible parts of the machine and it can be difficult or impossible to get them out. I've had to tear down the material station 3 times already, just to clear PVA fragments, and that requires first moving the giant heavy lump of a machine that is the S5 (a challenge for me) and then doing some very delicate service on the Material Station that Ultimaker would really rather us not do ourselves.  To their credit, they did help with what documentation they had, but they were pretty hesitant to let me do it and it is not fully documented.

 

I'm normally a pretty tolerant and patient person when it comes to working through problems, but when that PVA kept costing me entire days of billable time to tear down the machine, it got old REAL fast.  So on top of the real differences I outlined above, the frustration factor could also vary rather a lot depending on what setup your PVA is failing in and how much you depend on the machine.

 

At any rate, BVOH from BASF prints better than PVA, dissolves faster, is no more expensive, and to date (knock on wood) has not given me any difficulties at all, so it was quite easy to throw out my remaining kgs of UM PVA and make the switch.

 

Edited May 4, 2022 by rachael7

[Andrew_W 8]

On 5/2/2022 at 6:28 PM, TimonR said:

@Andrew_W: We recommend to dry the material at 50C, preferably also for longer times (overnight). Additional benefit is that this should relax stresses in the material, leading to reducing brittleness.

 

The trick is with PVA to dry the material without crystallizing it, PVA is a semicrystalline material, and will crystallize when heated over 55C for longer times. Crystalline PVA will become stiffer and brittle, so that's also undesired.

 

Moisture will lead to enhanced degradation during printing (e.g. the 'sugar crystals' you are referring to). Luckily, Ultimaker PVA doesn't absorb moisture as fast as other PVA filaments. In addition, there are no additives in Ultimaker PVA, which makes handling a bit more difficult but it is safer to print and easy to handle the water which was used for dissolving PVA (this is always a trade-off in soluble support filaments - it depends where the manufacturer focusses on).

 

Hope this background information helps a bit!

 

Thanks @TimonR I'll give these suggestions a go. 👍

 

Image below of the problem I had.

 

[TimonR 21]

@MobyDisk: that is true, especially in winter the moisture content in the air is relatively low, especially if you print in a room with heating.

To give you some insight: typical office environments have 50% RH at 20C in spring / autumn (summer can be a bit higher ~60%, and winter really depends on how cold it is outside).
Anyway, let's take 50% RH at 20C, if you heat up the same air with the same moisture content, your relative humidity will go down to only 10% RH. The point is that RH is kind of the 'active' moisture and this determines the moisture uptake of your filament (not the total gram water in air). So for getting wet filament and/or drying filament RH is the key parameter to focus on.



Increasing temperature helps in enhancing diffusion of moisture from within the filament to the air (basically speeding things up).

[TimonR 21]

@rachael7

Thanks for sharing your experience here.

To be honest, for us the brittle PVA in the Material Station was also unacceptable, we actually had a crash team working from multiple angles on this for several months - we definitely did not ignore this. 

For the other readers, check here in case you're interested in what we've done: https://support.ultimaker.com/hc/en-us/articles/360015621060-PVA-material-breaking-in-the-Material-Station.

 

So indeed, the brittleness is improved directly at the production location, and we design a feeder wheel with finer knurls to not damage the PVA. Our coarse feeder wheels apparently create a starting point (craze) for brittleness.

 

We are still actively monitoring if we see issues coming up like this, and I can imagine transportation to specific sites with higher temperatures might indeed lead to brittle PVA. Did you report your experiences to our customer service? Can you also share (roughly) where you are located?

 

[TimonR 21]

2 hours ago, Andrew_W said:

 

Thanks @TimonR I'll give these suggestions a go. 👍

 

Image below of the problem I had.

 

@Andrew_W: Thanks for the picture. I guess this is UM PVA and UM/3rd party black PLA?
What is your main issue and could you share a 3mf file?

[rachael7 73]

6 hours ago, TimonR said:

…

We are still actively monitoring if we see issues coming up like this, and I can imagine transportation to specific sites with higher temperatures might indeed lead to brittle PVA. Did you report your experiences to our customer service? Can you also share (roughly) where you are located?

Oh yes, many conversations with Fbrc8, many posts in the community here. I was even given the fine knurl feeder kit, which I tried (and since reverted). I’m located in Massachusetts, USA, which is in the northeast part of the country, though I think my UM filament comes from a warehouse further south. 

[Andrew_W 8]

On 5/5/2022 at 6:00 PM, TimonR said:

@Andrew_W: Thanks for the picture. I guess this is UM PVA and UM/3rd party black PLA?
What is your main issue and could you share a 3mf file?

Yes, UM PVA & UM balck PLA. The issue is when the build fist starts and it is swapping between support and build material in a short period of time (see images). After 100 layers or so it's OK.

 

Maybe I should post in another are of the forum?

 

Thanks.

 

[Andrew_W 8]

This is the part I'm having trouble with the PVA support. Once the print gets above the supported layers its OK.

 

Video shows extrusion, Is this caused by moisture?

 

https://www.youtube.com/shorts/UWW4NCxaJrY

 

 

UMS5_MX3294_3D_Print.ufp

[TimonR 21]

Hi @Andrew_W,

Interesting, can you also share a 3MF file of the project? Then we can actually see what settings you're using. It looks you have a modified PVA profile (?) and possibly a lot of small retractions / oozing that might cause these issues (from what I can see based on the ufp file).

From your youtube movie, it seems to be a a bit of moisture in your PVA that is bubbling during printing.
 

[Andrew_W 8]

3mf file attached. The model is trimmed as above the supported area it comes out OK. I have another spool of PVA on order plus some Breakaway to try.

 

Thanks.

UMS5_MX3294_3D_Print.3mf

[TimonR 21]

Hi Andrew,
Thanks for sharing the 3mf file. It looks like you're using 'tree' support, did you also try 'normal' support and does it give you the same error? 

 

On Breakaway: Breakaway is great if you don't have support inside your printed part (and PLA can typically handle most overhangs quite well - so this might be possible). This might help you out for this model, and post-processing is much faster.

[PaulKuiper 11]

The use of tree support causes a lot of retractions. PVA is protected from to many retractions and after a certain amount of retractions per time period it will not retract anymore (the dark blue travel moves below, the light ones are retracted travel moves). The causes the PVA to ooze on the model while traveling over it. Try to use the default profile (normal support) to see if the problem goes away.
 

[Andrew_W 8]

5 hours ago, PaulKuiper said:

The use of tree support causes a lot of retractions. PVA is protected from to many retractions and after a certain amount of retractions per time period it will not retract anymore (the dark blue travel moves below, the light ones are retracted travel moves). The causes the PVA to ooze on the model while traveling over it. Try to use the default profile (normal support) to see if the problem goes away.

 

10 hours ago, TimonR said:

It looks like you're using 'tree' support, did you also try 'normal' support and does it give you the same error? 

 

Thanks for the reply's, I will try normal support and see how it goes.

[Andrew_W 8]

Changing from Tree to Normal support gave me a much better outcome, image below. 👍