PVA support material outside of 3D print

[Japakli 0]

Hi!

As I was looking through the Forum I could not find aa answer to the following question. If there is: I am sorry, I am new here :)

I have recently started to print with the option of dual extrusion. When I use the natural PVA as a support material Cura is always placing a wall outside of the actual model, even though there are no overhangs. Is there any reason for this or a simple solution to avoid this wall? It seems like it is just a waste of the PVA material and it is prolonging the actual 3D print quite significantly. 

Many thanks in advance!

 

[gr5 2,094]

This is probably because of "support horizontal expansion" and is occasionally a waste but usually a good thing because...

 

PLA sticks nicely on top of PVA but not the other other way around - PVA does not stick so well on top of PLA.  But it sticks great to the glass and to itself.  So if you were printing say a cube with a large horizontal hole through it and you wanted support inside the tube.  It's best to connect the PVA inside the tube down to the glass bed.  "support horizontal expansion" takes care of that situation and many more (but not all situations).

 

I'd have to see the rest of your model to know if what you circled is very helpful or just a waste of PVA.

[Japakli 0]

Hi gr5,

Thank you for your quick reply!

I understand why it would need to stick on the glass plate in this case, but for me it would only make sense to have it inside the object really. I have attached some more pictures of my 3D model, I hope they are helpful!

Thank you again ?

 

 

 

 

Edited October 11, 2018 by Japakli

[P3D 46]

I think you have a special case here, where the auto-generation indeed produces "useless" supports.

But one thing: do you really have to print the model in that specific orientation? To me, it seems that rotating it, so the flat face on the opposite side of the opening lies on the print plate, would be much more efficient, as you wouldn't need any PVA at all...

Edited October 11, 2018 by P3D

[Japakli 0]

Hi P3D,

Yes, you are right, rotation would save me the struggle with the PVA. But I am printing in this orientation for a specific reason.
I am using clear PC filament and want the two hexagonal faces to be as clear as possible. When I print it upright the faces become very milky white, in this orientation they become quite clear ?

 

[peggyb 169]

this happens when the horizontal expansion from both sides is bigger then the wall thickness. When the wall is thicker this doesn't happen. What you could do is set the support horizontal expansion to zero.

 

Edited October 11, 2018 by peggyb