MakerGear Forum

I would like to make the attached structure (cube having through-circular holes, diameters are from 2 mm to 0.3mm)
using M2 3D printer and simplify3D.
I think it is difficult to make 0.3 mm hole, but even in 2mm hole, the shape of circle was pretty bad.
On the other hands, infilled parts were very good. I think circular motion of the nozzle and stage seems to be a little fast.
This is why the melted filament could not adhere to the structure and make "boundary".
I found one post about the speed of printing of circular structure.
(http://www.forum.simplify3d.com/viewtopic.php?f=8&t=124)
Based on the post, we have "Detect and modify circular segments" in G code tab of FFF setting.
But, I could not find that in Simplify.
I would appreciate it If you would suggest any tips to make "good shape" circle hole

That thread is discussing G2/G3 arc handling, which newer versions of Marlin have experimental code for. It doesn't work very well, and support was removed in recent versions of S3D.

What failures are you seeing? From the sound of it, it seems the circle boundaries are failing to adhere and are getting drawn across the circle. You can try a number of things for better adhesion:

Try increasing your width/thickness ratio. The default extrusion width is set at 0.35, which is too narrow. Try 0.40 or 0.45.
Try using Inside-Outside as the outline direction if you are not already. That may help by giving the innermost circle outline ("outside" boundary) something to grab a hold of. You need to use two or more outlines for this to have any effect.
Try printing exterior outlines slower, there is a ratio setting for that.

Finally, if you are investigating precision of holes for use in mechanical assemblies, you maybe interested in this discussion of holes precision: http://hydraraptor.blogspot.com/2011/02/polyholes.html

3D printing has inherent factors that affect hole dimensions. You can get around some of those by using "holes" that are straight sided polygons (which they all are, in any case, but specifically, low-resolution polygons).