Issue with PVA

[plasmageek 0]

Hi,

 

We're printing with PVA and finding it really inconsistent. Some times it prints with relatively little issue and other days it doesn't print well at all and we end up with a rat's nest. I've also noticed that chunks of PVA are getting ripped out by the feeder. We actually had it print the best after I took the feeder apart and cleaned it (note our machine is only about 2 months old now). I loosened the tightness on the feeder after the last cleaning in case that was causing the issue, but after two prints (we're onto the third) it's back to printing awful. I've cleaned the head multiple times (sometimes it looks like the materials burns a bit) in addition to having cleaned the feeder.

 

We're at 7300 sea level in the desert, so I haven't been worried about humidity. I've been working mostly with PLA as the main material. I use the main settings in Cura and haven't messed with the temperature values. I'm wondering if anybody has any advice?

 

Thanks!

[Jakeddesign 14]

When I run PVA on our UM3, I clean the nozzle every day or two, depending on how many prints I am running.  To clean the nozzle I use the clear nozzle cleaning sticks sold by Ultimaker, which work really well.  I set the core temperature to 220, push the plastic rod into the nozzle until the filament turns clear (indicated the cleaner material is moving through) then set the core temperature to 140. once it hits 140 (i call this a coldish pull) , I pull the rod out, usually bringing burned PVA with it.  After a good cleaning, you should be able to see daylight through the nozzle when looking down.  

 

Also, I tend to use Matterhackers PVA for a few reasons: #1 is that UM PVA is always sold out, #2 is that it is less brittle, so when the nozzle inevitably hits a support, it doesnt snap like the UM brand does.

 

Last thing is that if I am done with the PVA for the day, I put it into my air tight super dry box full of desiccant.

[kmanstudios 1,120]

There are so many factors that can affect the humidity that can get into PVA. I too use matterhackers PVA primarily due to cost. I can get a full Kg of the stuff for the cost of a .75 Kg of Ultimaker PVA. But, I do not discount using UM PVA though. There are times I want that stiffness. But, when you print with PVA, do you hear it pop and crackle? If so, humidity got in there.

 

Usually, I would try to tighten the tension on the feeder rather than back off. But, if you are grinding, you should take the feeder off and make sure there is no crazy stuff staying inside. The little bits and junk of ground up material. It will get stuck in the feeder wheel and make things just get slippery in there. And, make sure you are doing hot and cold pulls since it is probably building up carbon deposits.

[plasmageek 0]

Thanks for the replies and tips! It's good to know the PVA tip needs to be cleaned more often. I'll just make that a standard practice at least every two prints. Our prints are pretty large and tend to take 20+ hours. It normally goes wrong pretty early, but it would be frustrating to have it happen towards the end. I have noticed that I have to do the cold pull multiple times, even when the hot pull comes out clean.

 

I haven't noticed the PVA pop and crackle, but I will keep an ear out. Dry boxes aren't expensive, so we could feasibly get one and rotate rolls.

I've cleaned the feeder twice now, because I noticed that chunks were missing from the PVA and was worried it was gunking up the feeder. It was pretty messy in there both times and there was a nice pool of PVA dust just below the feed as well. I loosened it some more after yesterday's cleaning. It seems to still be feeding fine, but without so many chunks missing. There are still some, but they're considerably smaller than previously. I'm still not sure why that's happening. Another group member thought it was because the nozzel wasn't heating properly and therefore getting stuck. I could see if the PVA got stuck at the nozzel side that the feeder would spin on the same bit of PVA and might take some chunks out, but we can't really stop to clean mid-print (can we?).

[kmanstudios 1,120]

1 hour ago, plasmageek said:

It normally goes wrong pretty early, but it would be frustrating to have it happen towards the end.

Check out this post, it may help.....

 

1 hour ago, plasmageek said:

Another group member thought it was because the nozzel wasn't heating properly and therefore getting stuck

This is a possibility....

 

1 hour ago, plasmageek said:

but we can't really stop to clean mid-print (can we?).

See above...I figured a way to do it. A bit klugey, but it works and has saved a print or two for me.

[tomnagel 126]

Under normal circumstances, it is absolutely not necessary to clean your BB nozzle every few days. We've done 2000h tests on 20 printers, with varying cleaning intervals. Our advice is to clean the BB nozzle after 400h of printing (hot and cold pulls). But even the few printers that printed the full 2000h without cleaning still printed fine.

However, cleaning is very important after incidents like empty spool, or entangled filament or any other issue that keeps the BB nozzle hot without any material flow. The PVA then burns in the nozzle, and the nozzle will clog. (a print where there is a very small amount of PVA on each layer could also cause this)

 

Of course this was all tested with Ultimaker PVA. Your mileage with other brands may vary.

 

And @kmanstudios is right: keep your PVA dry.

 

[Jakeddesign 14]

4 hours ago, tomnagel said:

Under normal circumstances, it is absolutely not necessary to clean your BB nozzle every few days. We've done 2000h tests on 20 printers, with varying cleaning intervals. Our advice is to clean the BB nozzle after 400h of printing (hot and cold pulls). But even the few printers that printed the full 2000h without cleaning still printed fine.

However, cleaning is very important after incidents like empty spool, or entangled filament or any other issue that keeps the BB nozzle hot without any material flow. The PVA then burns in the nozzle, and the nozzle will clog. (a print where there is a very small amount of PVA on each layer could also cause this)

 

Of course this was all tested with Ultimaker PVA. Your mileage with other brands may vary.

 

And @kmanstudios is right: keep your PVA dry.

 

I suspect my issues are that my printer will run for several days, sit for a day, run some more...and so on.  Not running continuously could be the difference.  Additionally, I print a lot at .1mm layers, so maybe I am not moving enough support material though the nozzle. 

[plasmageek 0]

Jake, I think you and I are in the same position. Our PLA layer is only 0.1 mm in most places, with PVA under it for support. We've set all of our layers to print thin. This may be part of what is causing issues. I am trying to swap between our PVA's now, with one always in a bag with desiccant. and one on the printer, and changing between the prints. We'll see if it makes a difference.

Our next problem to fix is PLA warping....

[kmanstudios 1,120]

I routinely print at 0.1mm layers without issue, so I am thinking that is not the problem.

 

54 minutes ago, plasmageek said:

Our next problem to fix is PLA warping....

This should not be happening with proper bed adhesion. PLA is very warp resistant.

[tomnagel 126]

18 hours ago, Jakeddesign said:

I suspect my issues are that my printer will run for several days, sit for a day, run some more...and so on.  Not running continuously could be the difference.  Additionally, I print a lot at .1mm layers, so maybe I am not moving enough support material though the nozzle. 

I don't think so. The printers were operated normally, and there was a cooldown between printjobs. I don't think that a pause of a day between prints can cause issues other than PVA taking up moisture.

 

PVA should print reliably, this is tested very thouroughly for years now. If not, let's find out why not. There enough people here who can help, and your reseller should be able to help you as well.

Start with a clean BB nozzle, start with dry PVA filament, use Ultimaker filament, use Ultimaker Cura without changing printing parameters. If that does not work, please post pictures of what goes wrong.

 

 

 

Edited September 13, 2018 by tomnagel

[Jakeddesign 14]

It is possible that I am being overly cautious with my cleaning routine - by cleaning the nozzle every few days.  (When I do clean the nozzle, I only see specs of burned PVA, but nozzle is mostly clean)    But no way can I get 2000 hours without cleaning.

 

@kmanstudios what settings do you use for your Matterhackers PVA?  Maybe the default UM PVA temps are too hot.

[kmanstudios 1,120]

I use the default PVA temps. But, remember, PVA is very susceptible to environmental differences. What works here temp wise may not be so good for you.

 

I have my thermostat set at 68 f to keep the machines and computers cooled and the A/C dries out the air.