PVA tips?

[erichmc 12]

Hey guys,

I am printing a pretty simple structure with an overhanging feature. I am using white PLA. I seem to be struggling with the PVA as a support material. It tends to clump up on the nozzle and then burn.

My bed temp is 65-70C and my nozzle temp is 210C. Should I slow down the print? Use a build tower?

Any tips on successful PVA printing would be appreciated.

Thanks.

[SandervG 1,521]

Hi @Erichmc, thank you for your post and welcome to the community!

Do you have some photo's of what the problem is that you are having?

Usually that helps to identify the problem faster than based on a description.

Looking forward hearing from you!

[erichmc 12]

Hi @Erichmc, thank you for your post and welcome to the community!

Do you have some photo's of what the problem is that you are having?

Usually that helps to identify the problem faster than based on a description.

Looking forward hearing from  you!

 

Hey thanks for the response. Unfortunately I did not take any photos of the issue and I haven't printed with the PVA material since. To be a little more descriptive.... as the print head moves it seems that the material itself is curing faster than it is able to adhere to the build plate, resulting in the PVA not adhering and instead 'charring'/burning and clumping up on the nozzle.

[tomnagel 126]

Try the default profiles in Cura. They work really well with PLA/PVA. A lot of time was invested in creating optimal printing profiles. In most cases, you should get good results.

Cura 2.3 uses prime towers. In almost all printing profiles, the prime towers are no longer needed in Cura 2.4, because of some temperature tricks at the beginning and end of every layer. This suppresses oozing so well the prime towers are no longer needed in most cases.

Wait a few days with downloading Cura 2.4. It is currently in beta, and the beta 2 version contains a bug which harms the PLA/PVA interface.

[dotyman 0]

Hi Tom,

I'm curious about the bug in Cura 2.4 beta 2 that "...harms the PLA/PVA interface."

I am using Cura 2.4 beta, and I am getting a bit of pitting and unevenness in the PLA/PVA interface surface when I print a model using a raft or other full support for the model. The flat surfaces on the bottom of my models always has defects where it has been printed on top of PVA, whereas the top is printed pretty much perfectly.

I would like to eliminate this issue, if possible.

Thanks for any help. Let me know if I should start another thread to discuss it (sorry for highjacking your thread, Erichmc).

dotyman

[gr5 2,265]

@ericmc - anytime the filament is curling and not sticking to the buildplate on the bottom layer it's 99.9% of the time because the nozzle is too far away from the build plate. You can INSTANTLY confirm by pushing up on the build plate while it's printing. You can also quickly fix while printing by turning the leveling screws. The back right corner is often 1 or 2mm lower than the 3 leveling points so if your prime tower isn't sticking and your print doesn't reach the front left corner you can just lower bed at the front left which raises the bed at the rear right (it teeter totter hinges over a line connecting the other 2 bed leveling screws).

But if you aren't currently printing you can redo the Z calibration which is pretty easy and quick. I always level by eye both nozzles such that they are both barely touching the bed (fuc% the stupid paper). And check your glass with a straight edge like a ruler. I strongly suspect your rear 2 corners are very low. If so, remove the glass and bend up the aluminum A LOT until it's sticking up a few mm and then put the glass back on and hopefully the 2 things cancel (it takes about 1 pound constant force to keep my glass level in the back 2 corners).

[tomnagel 126]

The flat surfaces on the bottom of my models always has defects where it has been printed on top of PVA, whereas the top is printed pretty much perfectly.

 

The bug is that Cura 2.4 beta leaves exactly 1 layer of air between PVA and PLA (where PLA needs to be printed on top of PVA). You can see this in the layerview when you look very well. This is such a shame, because the bottom of your PLA will not look optimal.

Cura 2.3 did not have this bug, but the advanced temperature behaviour of 2.4 is very attractive because in most cases you don't need the prime tower anymore. This saves time and material.

So keep a look on the soon to be released 2.4 version of Cura!

[XYZDesignPro 70]

I am also struggling with how the roof / support interface works in 2.4

Beta2. In my opinion, the support interface / roof works much better in

2.3.1 in terms of how well it supports the the structure above if the

angle of the part being supported is very shallow. The details of the

final print at very shallow angles (10 degrees to 20 degrees) reveal that the layers

are not well supported. Especially if the part being supported is oval

or round. It's almost as if the part isn't really being printed on the

support interface / roof below it at all. (Air Gap?) Since the Z distance is set

to 0, (and cannot be made a negative number) nothing can be done to

improve the intimacy between the support interface / roof and the part

being printed above it. 2.3.1 seems to do a much better job in assuring

the the part is really being printed directly on the roof below. On the

other hand, if the part being supported is flat, then the PVA support is pretty good, and much easier to immediately remove dry, without

soaking in water at all. It's almost as though that was the design

intent when the software was re-written in 2.4.

Hope this was the proper place to post this . . .

[tomnagel 126]

try again with Cura 2.4 final, to be released today

[XYZDesignPro 70]

Final release of Cura 2.4 has solved the problem. Good job Cura development team

Here are a couple of items to add to the wish list:

I wish they would have left "Back" as a simple choice selection of the Z scar in 2.4. Much simpler than having to calculate exactly where the back of the model is. Especially when there are multiple models horizontally across the build plate. In 2.3.1 all of the models get the z scar in the same place at the back of the model, whereas in 2.4 the z scar is slightly canted to the left or the right of the back of each model depending on their relative location from the center of the build plate.

Also, I'd like to see the ability to select a different pattern for the

Top and Bottom, much as we can specify individual Top and Bottom Thickness.

 

try again with Cura 2.4 final, to be released today