Printing TPU with PVA support

[printingWhiz 0]

Hi,

I am currently experimentally trying to find optimal settings to print TPU with PVA for the model shown below. What my main problem is that whenever I remove the PVA from the structure after it is done printing, the TPU has very poor quality (i.e rough and uneven surface). I tried increasing the distance between the support and the main material with marginal improvement. I would be glad for any advice on how to fix this issue.

 

Thanks

Edited August 1, 2019 by printingWhiz

[johnse 31]

You might have better luck using either PVA (dissolves in water) or Breakaway.

 

Then again, the angles look like you may only need support to keep things from sagging at the hinges. You may be able to design minimal supports into your model and thus minimize the contact areas.

[printingWhiz 0]

Oh sorry I mistakenly wrote PLA instead of PVA. I am trying to reduce inter-material adhesiveness between PVA and TPU to improve the quality of the TPU material.

[johnse 31]

I haven’t tried printing TPU with support. I modified my other printer to print ashore 60A TPE, but it’s a single extruder. I’ve been using PVA and Breakaway with PLA and Tough PLA.

 

Are you letting the PVA fully dissolve? Or are you being impatient (like me) and trying to remove it early?

 

I see four kinds of interfaces: the underside of the angled pieces, the tops of the lower angled pieces, the bottom of the top, and the top of the base. Is the support material providing interface floors an ceilings? Or is the TPU bridging across sparse support? Which of these are giving you problems?

 

Perhaps some pictures of the finished part may help?

 

You may be able to minimize the affected areas by designing your own support. For example, you could eliminate top-surface contact by building columns from the base plate on either side of the lower angled parts and then bridging to provide the support for the upper ones. Similar for the top part. Also, where you have room, you can use slopes to connect the support columns where you have enough vertical space.

 

you may also only need to support the angles for a few mm on either side of each hinge.

 

[printingWhiz 0]

This is a pic of the affected part. And yes I am also impatient and try to remove the parts quickly rather than let it dissolve. I will try to build my own support I guess but thank you for the help!

 

[johnse 31]

That looks to me like the support is not creating an interface layer. Try the setting: Enable Support Interface. A description I found on Reddit:

"Generate a dense interface between the model and the support. This will create a skin at the top of the support on which the model is printed and at the bottom of the support, where it rests on the model."

This will greatly improve the quality of the part's surface.

 

[printingWhiz 0]

Hmm that particular setting was already activated by default. Should I try to play around with support interface acceleration for example? It is defined as the acceleration with which the roofs and floors of support are printed. Printing them at lower acceleration can improve overhang quality.

[camfux 0]

Hello there,

 

Have you been able to solve the problem? I am trying to print TPU 95A with PVA as a support material, too. But I can't obtain any print since the PVA is always stringing and/or clotting and my UM3 is unable to create the support structures with this kind of material.

Here is a couple of pictures of the kind of failure I always get and a screen of what I should get according to CURA.

 

Do you know how to prevent this issue?

If you are able to print with this combination of materials, can you please share the settings you use to do so?

 

[StevenD90s 3]

Hello,

 

Did you try lowering the temp of the PVA so it is less stringy? or increase retraction speed? so the filament does not build up on the nozzle?

 

The truth is the Bowden setup isn't really made for multi-material with TPU.  I get sub par results at best.  Also make sure the TPU and  PVA is dry as humidity will affect the results