Bad PVA or user error?

[jchojnacki 0]

Good afternoon everyone, I am a teacher new to 3D printing and I am having trouble with the support material. I have been able to pick most things up very quickly but the ability to print with support is killing me. I have had prints where the first layer of PVA lays down nice and progressively gets worse,  then other times the pva material will come out clumpy or not even extrude. I have tried messing with the speed and temp to no avail. I am printing on the ultimaker3 and using ultimaker material and attempting to print with a 0.4 head with both materials. I was starting to think it is just poor PVA material, but I have opened a brand new package and had the same results, so I'm thinking I am missing something on the settings?

I have attached the file and photo. Any help is greatly appreciated. If there was a previous post on this somewhere maybe a moderator could share or point tme in the right direction. Thanks in advance.

Mr. C

UM3_front bbs rims (1).gcode

[gr5 2,072]

There are 2 common problems with PVA.  If you are seeing black gunk and material isn't coming out you may have caramelized it.  On the UM3, in the menu system under I think "maintenance" maybe there are instructions for doing hot and cold pulls.  Follow those to clean out the nozzle.

 

More likely your problem is due to water absorption.  Even just 24 hours at typical (40-60%) humidity can wreck PVA.  Restore it by heating your heated bed to 55C.  Unspool enough for the prints you will do that day (cura tells you how many meters are needed.  Place that on the bed and the spool on top of that (the spools can warp even at 60C but if they are a few mm above the bed it will be fine).  Put a towel over all that.  Maybe 3 or 4 towels or a blanket or something.  Leave it like that for 24 hours (certainly at least 8 hours at 55C, less time needed at say 70C but that will probably cause the PVA to deform - I do this to nylon at about 70C - PLA doesn't need to be dried).

 

The meters of filament you unspooled will now be miraculously just like new.

[jchojnacki 0]

Thank you, I had a feeling it was more of a material issue. Do any of you use the dehumidifier storing stations?

[gr5 2,072]

You want to get the humidity incredibly low - around 15%.  I don't think most of those storing stations get that low.  Personally I use a combination of rechargable desiccant and the heated bed method I mention.

 

I bought a liter of desiccant and use about a 1/2 cup of it in a 2 gallon (mixing metric and imperial, lol) ziplock which is big enough to hold the container of desiccant and a spool of filament.  I also use a humidity sensor which is crucial as before I started using the sensor I realized I was only getting the humidity down to 30% which wasn't enough.  I dry the desiccant in the microwave.  30% humidity is much too high and gives me horrible results.

 

The desiccant is only used to maintain dryness.  To dry the filament I use the heated bed.

 

It's all a bit of a process but necessary for PVA and Nylon.

[jchojnacki 0]

Can you recommend a humidity sensor? I'm going to try the above suggestions. In regard to the actual printing of the PVA. the standard settings should be fine? There are no major adjustments that need to be made?

Thanks

[Framar 38]

I would recommend the use of a dry box. There is a good one from Polymaker I'm sure you can easily find from any 3D printing store.

[gr5 2,072]

I got something similar to this.  It seems to work fine.

 

https://www.ebay.com/itm/203963346074

 

[Andrew_W 8]

Your attached images look just like the issue we had with too much moisture in our PVA. I put it in an oven over the weekend at 55°C and then store it in a sealed bag with desiccant. No more problems now. Hope this helps.

[gr5 2,072]

Desiccant is great but use a LOT.  A fist sized amount.  And if it's not fresh out of the original packaging, you need to recharge it.  I used to recharge my desiccant by microwaving it - steam would come out and it would change back to the original color but using the humidity monitor I realized I was only getting the dessicant down to 30% humidity.  Now I strive for 10 to 20%.  Typically around 15%.  Not sure if that's enough but it's better than 30% as that was definitely not enough. 

 

Other people say 10% makes the nylon print like a dream but then the parts are stiff and brittle for a few weeks until the parts absorb a little water.

[dsp 18]

I use the filament drybox of Sunlu and keep the pva at a 45°C to 50°C and print right out of the drybox, it works like charm.

Also I put around 3 silica bags in with the spool. Before I could use the pva for like 2 to 3 prints max before it started to give issues like blocking in the nozzle and bad prints. my problems melted like snow for the Sunlu, just heat up the drybox 2 to 3 hours before the print and keep it warm for the duration of the print. 

[Michael_H 1]

My personal experience is that the zig-zag support structure simply does not work well with PVA. Does anybody get good result with this combination? If the nozzle moves across the structure without printing it destroys everything.
I use triangle structure for PVA.
In addition glue is required for PVA to stick to the glass plate.

 

Several people mentioned that PVA needs to be dry. Recently I also had a problem with bad PVA but it definitely was not because of moisture. In the instruction leaflet it is also written "keep out of direct sunlight". I think that UV light might permanently damage the material. In my case thicker PVA layers were no longer transparent as with fresh PVA but white.

[glx 21]

I also can’t make PVA print supports nicely. The supports look and behave awful but it prints relatively nice when I print something else with it. The two images are from two prints immediately after each other (first the supports then the PVA-benchy). 

 

[gr5 2,072]

6 hours ago, Michael_H said:

In my case thicker PVA layers were no longer transparent as with fresh PVA but white.

White is sometimes caused by bubbles (super tiny bubbles) which are usually caused by steam which is usually caused by moisture.  It's a lot harder to get PVA dry than you might think.  And in my experience after about 2 hours of printing the PVA is already getting bad again (nylon also).  Here is a succesful Nylon/PVA print from a few days ago.  I suppose it does look a little white but also kind of transparent.  Final picture is after dying the nylon black.

 

 

 

 

 

 

 

[dsp 18]

On 11/1/2022 at 4:17 PM, Michael_H said:

My personal experience is that the zig-zag support structure simply does not work well with PVA. Does anybody get good result with this combination? If the nozzle moves across the structure without printing it destroys everything.
I use triangle structure for PVA.
In addition glue is required for PVA to stick to the glass plate.

 

usually when I use the PLA as support with a roof of PVA then I use the zigzag for the PLA

in this way you can get good support which can be removed in seconds