UM3 PVA Printing issues - any ideas for tweaking settings?

[sproutdesign 5]

Hi,

I'm printing with Ultimaker branded PVA and Faberdashery White PLA.

From experience the Faberdashery White PLA is a very reliable material to print on my UM2+s with.

I'm not sure the settings for the Ultimaker PVA are working at all well though - what can I try next?

Attached is a photo - you'll see the UM PVA is a birds nest mess creating loose debris, which is also getting dragged through PLA regions.

These are out of the box settings for a new UM3 extended on "Normal" quality with support "everywhere" with standard settings/cores for PLA and PVA. I think the default with PVA is also 30% support density and its printing triangles.

I think I'm having the following issues:

- The PVA is not adhering to the previous layer of PVA where towers are deteriorating

- The PVA is not adhering to the PLA where internal supports are being built on it

- The PVA is stringing over the PLA and getting included through walls where it shouldn't be

- Support towers with PVA strings sticking out are getting knocked and broken

Does anyone know what tweaks I could try to settings to get improvement in the PVA performance?

EG should I be printing hotter / colder than the default settings?

I'm hoping to find a way to print the PVA bits reliably as I have 100 of these to print(!) - any advice on PVA would be much appreciated

Alternatively, If I can't get the PVA supports to work, then I'd like to selectively delete the failed PVA support structures in Cura leaving only the ones that work, or assign some supports as PLA and some as PVA to avoid the problems - is there a way to do this?

Thanks!

Photo:

Edited November 6, 2016 by Guest

[ultiarjan 1,223]

I don't see in the picture where it wen't wrong......

In my experience the PVA sticks very well to the bed, but a lot less to PLA.

This can lead to problems on the wipe tower and on other areas where the PVA has to start on top of PLA. In the last case increasing "support horizontal expansion" in Cura can sometimes solve this, as it may result in PVA starting partly on PVA

[sproutdesign 5]

Hi,

Thanks for the reply.

I agree PVA sticks to the base!

I guess it is not clear enough from the photo so I've taken a screenshot of Cura at this layer of the build

It seems happy to build fully enclosed PVA supports (in the rectangle top right)

But you'll see from the Cura screenshot there are freestanding towers of PVA that it generated that in the photo are now the debris that is penetrating the PLA on the left hand side.

So for these PVA supports which are causing problems, ideally I'd like to:

- change the settings so they build correctly

(maybe "support horizontal expansion" as you suggest)

- or selectively delete the worst ones in Cura

- or selectively reassign them back to PLA in Cura

Any other ideas welcome

Thanks

[sproutdesign 5]

I'd also add Cura 2.3 generated more supports for the PVA than I'd previously had.

I have already printed this 54 times on my UM2+Extendeds single extrusion and it takes an hour or so to clean up each one. The Faberdashery White PLA gives an excellent finish - no bobbles or stringing, but I still have to hand finish where the supports join the housing.

It would be really nice to just dissolve the supports with UM3ext dual extrusion, but once I've dissolved the PVA that has been dragged through the walls it will have lots of holes and the part will not be presentable.

Cura seems to want to build thin towers of PVA (which my UM3ext can't seem to build, especially on top of PLA) up to meet the side of any holes in the print, where previously Cura would have just created local supports inside the hole.

I've never edited g-code but if I can't get rid of the PVA towers in Cura can I do it by editing the g-code somehow?

I'd rather have a robust g-code file for repeated printing that has the towers removed or re-asigned to PLA (with the central support still PVA) if I can't nail the settings or get PVA to stick to PLA - is there a way I can edit the gcode to do this?

[neotko 1,417]

Not sure if this can be of help since pla to pva adhesion can be tricky.

I would play with

Support horizontal expansion, thin pva over pla can fall.

I would increase PVA retraction from 2 to at least 4 (I would risk it and go to 6 but that's me)

I would increase PVA flow to 120%, to compensate from the drip from moving from a to b

I would use Avoid Printed Parts when traveling and increase Travel Avoid Distance as much as cura allows (it decreases the print area so depends on the model. This will help to avoid PVA falling on top of printed PLA, and this way you can avoid having holes after removing it on water.

This is IMO what I would play with. This options are hidden by default and you can unhide them on advanced clicking on the Gear icon or Cura/Preferences/Settings.

Also if you do this you most probably can remove the wipetower on 'Dual Extrusion' options.

All this is in Advanced mode ofc, and I would try them on a smaller scale model or part that has the same characteristics.

Edited November 6, 2016 by Guest

[sproutdesign 5]

Support horizontal expansion

I would increase PVA retraction from 2 to at least 4

I would increase PVA flow to 120%

Avoid Printed Parts when traveling

increase Travel Avoid Distance

remove the wipetower on 'Dual Extrusion' options.

 

Thanks Neotko!

I'll start again with these settings.

If anyone has thoughts on selectively editing supports to get rid of thin ones or selectively assign materials to them I'd be really interested.

[neotko 1,417]

Btw the huge problem by touching the PVA retraction is that it can 'burn' more. So after a long print I would really really do an Atomic Cleaning of the BB (because of this adjustment PVA stays more time on the Core and even when the design is quite fantastic, heat is heat and PVA burns and goes brown. So this setting please take it with much care, I love to tweak here and there but it might be an issue if isn't used with care.

Just for reference, this is how BB Core Atomic pull is done:

https://ultimaker.com/en/resources/23132-maintaining-the-bb-print-core

[ultiarjan 1,223]

Cura seems to want to build thin towers of PVA (which my UM3ext can't seem to build, especially on top of PLA) up to meet the side of any holes in the print, where previously Cura would have just created local supports inside the hole.

 

pretty sure this is the "horizontal expansion" which is a good thing if it's helping the PVA to build from the bed iso the PLA part. If the structure is to small you can play with increasing the horizontal expansion.

[DidierKlein 729]

Might also be that the white Faberdashery filament has a "special" composition which makes PVA less printable on top of it?

I had once printed two white objects that needed to be glued together, one in was in white ultimaker, and one in white faberdashery.

The faberdashery almost melted and bond extremely fast, while the pla print left much more time to bond...

You can maybe get rid of the towers if they are not needed by playing with the support angle value. If you look in normal view the overhangs will appear in red, when you change that value the red areas change