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Print top of spheres and other curved surfaces correctly?

Posted: Sat Dec 13, 2014 5:49 pm
by kodachrome
Im having a problem with any curved surface, when it gets to the top (or sometimes bottom if shape like eye socket in skull prints) its seemingly just not bothering to fill in the shape with enough layers, leaving huge stringy/squiggly gaps. Rest of shape prints nicely!?

See attached image:
It gets far worse when I put infill to zero (golf ball print on left, infill zero and tried various top and bottom layer amounts, no diff at all) but is visible with default Rostock PLA settings too (golf ball on the right).

Whats causing this?

Re: Print top of spheres and other curved surfaces correctly

Posted: Sat Dec 13, 2014 6:11 pm
by Mac The Knife
What size nozzle? What is your layer height? Layer width?

Re: Print top of spheres and other curved surfaces correctly

Posted: Sat Dec 13, 2014 6:12 pm
by bot
I've found Slic3r is terrible at this, and Cura excels at this.

Re: Print top of spheres and other curved surfaces correctly

Posted: Sat Dec 13, 2014 6:20 pm
by Earthbound
Those top layers need something to sit on. Add infill. Or print very slowly with maximum cooling.

Re: Print top of spheres and other curved surfaces correctly

Posted: Sun Dec 14, 2014 3:12 pm
by kodachrome
Mac The Knife wrote:What size nozzle? What is your layer height? Layer width?
0.5mm nozzle, standard PLA settings for Rostock Max (as supplied)... 0.35mm and 0.2mm off the top of my head.
bot wrote:I've found Slic3r is terrible at this, and Cura excels at this.
Hmm, surely if its consistantly this bad people wouldnt use it at all?! Does Cura still not handle temps itself and require GCode messing about on the Rostock?
Earthbound wrote:Those top layers need something to sit on. Add infill. Or print very slowly with maximum cooling.
The second (on the right) ball has infill and it still does it to a lesser degree. And adding infill is an extremely costly method of only partially solving a problem on the last 1% of a curved model.

Re: Print top of spheres and other curved surfaces correctly

Posted: Sun Dec 14, 2014 4:13 pm
by Mac The Knife
And you are using a layer fan?

Re: Print top of spheres and other curved surfaces correctly

Posted: Sun Dec 14, 2014 7:03 pm
by bot
Cura works fine with the rostock. What Cura does for areas like the one shown in the first post, is to build up infill to support the curved top section. Even if infill is set to 0, it will add infill support on the edge of the curve. It looks weird while it's printing, but the end result is fantastic.

Re: Print top of spheres and other curved surfaces correctly

Posted: Mon Dec 15, 2014 4:27 pm
by kodachrome
Mac The Knife wrote:And you are using a layer fan?
Yep.
bot wrote:Cura works fine with the rostock. What Cura does for areas like the one shown in the first post, is to build up infill to support the curved top section. Even if infill is set to 0, it will add infill support on the edge of the curve. It looks weird while it's printing, but the end result is fantastic.
Excellent, Ill give it a shot and update.