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Shaun167

PLA on PVA

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After trying for over 3 months it is now obvious that the Ultimaker 3 is not capable of using PLA and PVA together and I would not reccommend this machine and any claims you may make that it can work.

This problem appears on the web from other users also, it is just not my printer.

This problem needs and must be sorted in order for Ultimaker to retain their good name.

Yours

VERY UNHAPPY

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Hi @Shaun167, welcome to the forums!

Sorry to hear you seem to have had some issues with combining PLA and PVA. PVA is not the easiest material to work with, but with the proper usage and treatment it is definitely doable. If you could explain your challenges and results with us I am sure we could give you some tips to get it to work.

It may not sound appealing at first, cause you probably have already tried a lot of things (maybe everything), but I think it may be worth the effort since at one point you decided you needed the Ultimaker 3, and also dual extrusion. Look beyond the frustration and getting it to work now so you can finally start using those features is only one small last step, right?

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Thank you for the tips, the settings are already in use. I am trying to print parts of a power station which consists of slabs, steelwork pipework handrail and open mesh flooring.

The PVA is required in a number of places on each print, direct to the plate and direct on the structure supporting other parts above.

Jack Broughton at GBIRE UK has a very large selection of photos of failed prints over the last 3 months, we even duplicated one of the problems at his office using his settings and printer.

Attached are photos from the last failure and parts which have printed ready for assembly.

Hope these help to make it clearer

Shaun

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Hi Shaun, I don't see any photo's included in your post. Perhaps you forgot a link, or to upload them?

In the latest Cura version (beta) we have improved some settings that should improve the adhesion between PLA and PVA, especially in the areas where PVA rests on the PLA.

There are settings evolving around support interface. Have you made any tests with these features?

Photo's are always helpful! :)

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What are the environmental conditions? I have found that PVA is very susceptible to changes. I have seen it change within 30 minutes as changes in humidity occur, like say, opening a door to the room to air out the area when it is raining outside or just a humid day.

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@shaun167 - pla doesn't stick well to pva.  So printing on a "slab" of pva probably just isn't going to work.  Well it will stick but if it's a large part - it might not stick well.  However pva sticks to itself nicely.  And pla sticks to itself nicely.  So you have to design things so that pva goes "all the way down" to the bed.  And that the pla also goes "all the way down" to the bed.  That's very easy to do with 95% of prints but there are millions of geometries where this is difficult or impossible.  But there are tricks.  Workarounds.  I'd like to see a photo of what you want the final print to look like.

Think of it this way: PVA should be thought of as something that pla rests upon but does not stick to.  So if you print a slab of pva and then try to print pla on top it won't work.  But if you add 3 or 4 "legs" that connect down the layer of pla below (or to the glass below) then that will stabilize things and your print should be successful.  This same concept is MUCH MORE IMPORTANT for PVA.  It just will not rest on top of PLA very well. That is the purpose of the "horizontal expansion" parameter in support settings.  Which is on by default. But with some part shapes that won't help.

Edited by Guest

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Think of it this way: PVA should be thought of as something that pla rests upon but does not stick to.  

 

That is the case with ABS, there is no bonding between the materials and it will just slide off. I think it is a stretch too far to say it doesn't stick at all but there are certainly things to take into consideration. Cura 2.6 Beta has some improved features to give users more control over their slicing and improve the connection between PLA and PVA. Gr5's tips may certainly improve the success rate of the print so I would say they are worth trying, if you do not get it under control 'the regular way'.

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I have printed with PVA rafts with no issues.

I have had to use anchors or legs to help other materials stay in place while using the PVA as a cradle or support to lay upon to let large/long bridging work well.

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@kmanstudios, I want to report your need to use a cradle or anchors. Could you share your Cura version with me where you felt this was necessary, and a link to the model where it was necessary?

Do you have any additional information on the environment you used it (like ambient temperature / humidity) and the state of your PVA?

(@Gr5, if you have an example for the above mentioned, that would be welcome too!)

We may all learn something :)

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@kmanstudios, I want to report your need to use a cradle or anchors. Could you share your Cura version with me where you felt this was necessary, and a link to the model where it was necessary?

It was an environmental issue. It does not happen often and I can tell because when I have opened the doors to air out the studio, I can detect a difference in the printed part as well (ie. not the support).

And, it was not something that I would have reported because it is such a rare, environmental issue.

The only thing I have not had it work with on a consistent pattern is ABS. I have had success with a lot of things in certain situations, but never on bad humidity days.

Edit: OH! I have a print working right now that has had some slippage on the PVA with my first roll of Colorfabb PLA. But, it is humid here. Not sweating humid, but it is making the PVA crackle even with a low temp. It is also not Ultimaker PVA.

Edited by Guest

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Just in the interest of clarity:

This is the current print. Matterhackers PVA-Colorfabb Orange Translucent.

As I said, most of my print issues are noobish errors or environmental.

I also keep the front covered with taped up bubble wrap, but that will not stop the basic humidity issues.

PVANotStickingAlways.jpg

Edited by Guest

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Rats I thought I replied to this a few hours ago but it got lost. Okay so first of all - I think you need to increase "horizontal expansion" here because that should make the pva connect to itself in the very areas where it failed. It should connect all the way down to the glass.

Secondly that pva looks very white. Whiter than UM PVA. Could it be that it got wet? You can tell because it hisses and crackles as you print making a "snowy white" result. Kind of foamy or spongy because the water is boiling as it prints and adding air pockets.

UM PVA supposedly is better at not absorbing water than other brands (I don't know - I haven't tried any other brands yet).

It's best to keep the PVA super super dry. Keep it sealed up over night and with a fresh desiccant each time you open the bag. I have the kind of desicant that changes color when it's done and you can heat it and reuse it.

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Not sure if that was for me, but since I have the only photo:

1. Nope, not Ultimaker PVA as stated.....Matterhackers PVA

2. Yep, humidity issues as I stated and stress the environmental issues when people have certain issues as I can trace most of mine to that alone.

3. Actually cream colored, just the way the photo took in the lights under the Ultimaker bluish lighting.

4. Will try the horizontal expansion issue. But it is odd it is not consistent as it will stick on some other areas no problem.

5. Does not always have to connect all the way to the glass as it will build on itself over the PLA in areas that begin to require the support. At least, that has been my experience. Say a shelf that then juts out a bit with an overhang that does not get to the areas that buildplate to overhang is not possible. Also depends on towers, conical supports, etc. The image is a bit misleading in it is not nearly as vertical as it seems in this image. There is a taper moving in towards the center of the model with juts out from that taper that are about horizontal with the buildplate. This is the final, large print of my spaceship design that I posted about a proof of concept model.

Kinda hard to prevent the absorption of moisture during a long print. But, I do know I need to build a dry-box-feeder for that very reason. Honestly, too busy learning different materials, shortcomings and long prints. That and it is still working 98% of the time and the rest is just a bit of a bother. But will get around to it as soon as I get a few other things taken care of.

As I have said, I have gotten any of my PVA brands to work with a great deal of success. And, kinda saving that last roll of Ultimaker PVA.....that stuff is pricey.

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I don't know if humidity is causing your issues or not. I'm just not experienced enough. So maybe not. But I do know that PVA can sometimes stick to PLA but it's hit or miss and you are MUCH better off having pva go "all the way down" to the glass. So increase the hell out of "horizontal expansion" until it's all connected.

Regarding humidity - I have a gas oven but if you have an electric oven try that - I've heard great things about preheating nylon to dry it. I forget but I think it's only 1 hour. Don't know about pva as that has a much colder glass temp.

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I don't know if humidity is causing your issues or not.  I'm just not experienced enough.  So maybe not. But I do know that PVA can sometimes stick to PLA but it's hit or miss and you are MUCH better off having pva go "all the way down" to the glass.  So increase the hell out of "horizontal expansion" until it's all connected.

Regarding humidity - I have a gas oven but if you have an electric oven try that - I've heard great things about preheating nylon to dry it.  I forget but I think it's only 1 hour.  Don't know about pva as that has a much colder glass temp.

 

I am going to try the horizontal expansion next time I print with PVA. I usually do not have problems until humidity or temperature becomes a factor. And, I do try to save on the PVA because, well, it is pricey. That is why I recycle the heck out of the stuff into slurry. Believe it or not, I have more than three gallons of the stuff. And, I believe that it is a bit thicker than most people make when doing the 1:10 ratio of glue to water.

But, I am also experimenting a bit with settings to cut down on waste, while not sacrificing quality or functionality.

That piece died about 4/5 of the way through due to a piece coming loose (first time I have had that happen) in a place that was glass to part and was well cradled. It just did not stick in that area. It started to spin air webs and then drag to another part of the model and deposit a blob on the model elsewhere. It was the bumping of the head on the blob that alerted me to a problem.

So, I am doing two color PLA prints to try something and then back to the week long render again.

Until it died though, it really printed nice. Figured a way to rescue/repurpose the model though :)

Edited by Guest
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Hi Shaun, I don't see any photo's included in your post. Perhaps you forgot a link, or to upload them?

In the latest Cura version (beta) we have improved some settings that should improve the adhesion between PLA and PVA, especially in the areas where PVA rests on the PLA.

There are settings evolving around support interface. Have you made any tests with these features?

Photo's are always helpful! :)

 

Can you send me your direct email address to me in a DM and I will send you as many photos and files as you need to show this problem.

All work has now come to a stop as yet another print has failed, this time the pva has not adhered to the plate which is the major area or small areas of the pla.

This is a very large project with one of the biggest power stations in the UK.

Regards

Shaun.

Edited by SandervG
removed personal information

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I don't know if humidity is causing your issues or not.  I'm just not experienced enough.  So maybe not. But I do know that PVA can sometimes stick to PLA but it's hit or miss and you are MUCH better off having pva go "all the way down" to the glass.  So increase the hell out of "horizontal expansion" until it's all connected.

Regarding humidity - I have a gas oven but if you have an electric oven try that - I've heard great things about preheating nylon to dry it.  I forget but I think it's only 1 hour.  Don't know about pva as that has a much colder glass temp.

 

I am going to try the horizontal expansion next time I print with PVA. I usually do not have problems until humidity or temperature becomes a factor. And, I do try to save on the PVA because, well, it is pricey. That is why I recycle the heck out of the stuff into slurry. Believe it or not, I have more than three gallons of the stuff. And, I believe that it is a bit thicker than most people make when doing the 1:10 ratio of glue to water.

But, I am also experimenting a bit with settings to cut down on waste, while not sacrificing quality or functionality.

That piece died about 4/5 of the way through due to a piece coming loose (first time I have had that happen) in a place that was glass to part and was well cradled. It just did not stick in that area. It started to spin air webs and then drag to another part of the model and deposit a blob on the model elsewhere. It was the bumping of the head on the blob that alerted me to a problem.

So, I am doing two color PLA prints to try something and then back to the week long render again.

Until it died though, it really printed nice. Figured a way to rescue/repurpose the model though :)

 

Just started a print today and already failed.

90% of the PVA was direct onto the plate the rest was on the PLA and lost adhesion and started to mis-shape and pull from the plate.

Cheers.

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@shaun167 - pla doesn't stick well to pva.  So printing on a "slab" of pva probably just isn't going to work.  Well it will stick but if it's a large part - it might not stick well.  However pva sticks to itself nicely.  And pla sticks to itself nicely.  So you have to design things so that pva goes "all the way down" to the bed.  And that the pla also goes "all the way down" to the bed.  That's very easy to do with 95% of prints but there are millions of geometries where this is difficult or impossible.  But there are tricks.  Workarounds.  I'd like to see a photo of what you want the final print to look like.

Think of it this way: PVA should be thought of as something that pla rests upon but does not stick to.  So if you print a slab of pva and then try to print pla on top it won't work.  But if you add 3 or 4 "legs" that connect down the layer of pla below (or to the glass below) then that will stabilize things and your print should be successful.  This same concept is MUCH MORE IMPORTANT for PVA.  It just will not rest on top of PLA very well. That is the purpose of the "horizontal expansion" parameter in support settings.  Which is on by default. But with some part shapes that won't help.

 

Just lost a print with 90% of the pva direct onto the plate.

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@shaun167 - If a material won't stick to the glass, try cleaning it very well with water soap and then window glass cleaner. do this in a sink. Then re apply some glue stick and spread it around with a wet tissue. Put it back on the printer and heat it up and wait for the water to dry (by the time it hits 60C it should be done drying or seconds from completely dry).

More importantly also you need to squish that pva into the glass when printing the bottom layer. I personally turn off auto leveling but if you use it then watch the first layer go down. If it's not getting squished flat like a pancake then turn the screws WHILE IT'S PRINTING. Turn each of the 3 screws the same amount CCW. About 1/4 to 1/2 turn should be enough usually. I have a whole video about this so you can see me doing it in action. It's a long video but it's full of useful facts for getting parts (including pva) to stick to the glass very well:

 

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