Printing internal/external first automatically

Hi Im using Slic3r and prusa i3 printer.
When printing human body I usually went in to trouble at boobs, shoulders, chin, head, etc.
Even if I use extra perimeters (it make some improvement) it is not ideal and I think that problem is in setting external and internal perimeters first.
If it will be automatic, it might be better, but I do not know where to set it or how to set it in slic3r.
I tried to paint it from side view (in attachment):

If I use external perimeters first, it helps when the mesh is going inside (shoulders, head), than it is almost all fine (green color), but once mesh starts going outside (boobs, chin) and it prints external perimeters first, it prints first 2 perimeters in to the air (see attachment - red color) and destroy final product.

If I set internal first, than when going inside it will print in to inside first 2 perimeters and when going outside it is good. At the end there are holes in mesh. Especially on shoulders etc.
Is there any ideal way of settings how to slice objects like that.
Many thanks for your help.

I forget to mention when i print without support.

Can you post pictures?

---

[3DKarma.com] - suppliers of quality, affordable 3D printer kits and filament for the UK market.

This is printed with:
- no support
- 2 perimeters
- internal perimeters first
- used extra perimeters where needed

Botom side of the breasts are all good, but top side are with holes because even with extra perimeters it is printing extra perimeters in to the air and it does not help ...

Looks like you're bridging there without any infill beneath. What are your infill settings? If you increased infill, the bridge span would be lower and the top surface would print better. You might also be under-extruding slightly.

Also, if this is PLA, a fan directed at the print would help with the sagging.

---

[3DKarma.com] - suppliers of quality, affordable 3D printer kits and filament for the UK market.

Using ABS, no infil, because with infil it will be printing ages.... and it will be heavy.
But as I said. If there will be possibility like "auto internal/external first" it will help. Because bottom of the breasts (perimeter is increasing) will be printing internal first. And top of breasts and shoulders (perimeter decreasing) will be printing outside first...
But I did not foud it there. So Im asking if it is in slic3r somewhere hidden, or if i should post requirement for new function....
I saw print like that without infil and just 1 perimeter and no holes in that (It was printed with makerboot and no idea how it was sliced) so prusa i3 must print it as well and it is just about settings of slic3r...
Thanks
Jan

I don't believe there is such a function in Slic3r, so requesting it would be your best bet. However, in the short term, you could generate both versions in Slic3r - one with internal first, the second with external first. Load the first up and look for the Z-height change instruction at the transition point in your model from overhang (you can load the gcode into a view such as gcode.ws to visualise this). Delete everything after that instruction in the first file, and copy everything after that instruction from the second file, to the first.

---

[3DKarma.com] - suppliers of quality, affordable 3D printer kits and filament for the UK market.

It is good idea... never tried that... I will give it try and if succesful than I will post new request...
Thanks 3dkarma!

You could also look at the setting "Only infill where needed" which will do as said and give infill only when there is something that needs supporting so it won't affect your print time so much.

Dave

I think you do need SOME infill, 20% may do it, perhaps even 15.
How do they print with Cura or Skeinforg ?