How many rotation segments for a smooth finish?

Hi,

I'm modeling a tube for printing (it's going to have more details, but a tube is its base).
While setting things up i was wondering how many rotation segments i would need for a smooth finish?
It's going to have to fit snugly around a brass pipe and I don't want any of those lines visible.

My example shows 108, 72 and 36 rotation segments...off course i want to use a lower number rather than high.
What would be best? The model will be printed in Strong & Flexible Plastic and the size is 44 x 80 mm.

Happy to hear your thoughts!

Kat

Quoting Stonysmith.from here https://tinyurl.com/k9llsbo

... to get maximum smoothness out of the printer, the faces should be no wider than 1/2 of the "minimum detail" value. WSF has a minimum detail of 0.2mm.. so your faces should not be more than 0.1mm across.

Also note the measurement across the wall thickness. I had a part rejected because of thin walls. I designed a 'tube' with walls of 0.8mm thick, when Shapeways measured it across the flats it was only 0.78mm. It still got rejected.

Thank you for this, it makes sense to take the minimum detail factor into consideration.

It does amount to an incredible high number though...If i need need 10 segments for every mm of the circumference, in my case the number of rotation segments would be 1193. My software doesn't support more than 1000 ☺

The Stonysmith formula makes a lot of sense but looking at the surface of this material: sanded, grainy sort of quality...Wouldn't a 0,2 mm face be ok? Or even 0.3? Not that i don't appreciate your answer off course ☺

(Wall thickness will be ok i think, 3mm.)

To extend my earlier notes.. if you want maximum smoothness, the facets should be 1/2 of the "step size" of the printer. On a number of the Shapeways printers, the step size is even smaller than the Minimum Detail setting - I think a number of the printers actually have like 10 steps within the Minimum Detail measurement. Time to break out the facets. <grin>

Here's another viewpoint on the same topic:
http://stonysmith.com/wired/scaling.asp

You obviously must adhere to the limits imposed by your software, but your original question was "how to make it smooth".

Here's another consideration for you: How closely will the item be viewed? If it is only going to be viewed from a distance (in model trains we call this
the "Three Foot Rule"), then the item can be rather coarse. If someone is going touch it, or worse, to view it under a microscope... you'd better add "more" detail <grin>

Wow, 10 steps within minimum detail? That's impressive actually.

☺ It won't be viewed under a microscope (phew). Just as long as i don't get a faceted look, it's all good.

I'm going to take a risk and make the segments 0.3 mm.
I'm thinking it will seem smooth to the eye and touch. And the grainy surface will help a bit as well

Thank you for the insights and for helping me decide!