[PLA on PVA]

@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.

[PLA on PVA]

 

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.

[PLA on PVA]

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.

[PLA on PVA]

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

[PLA on PVA]

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