3D printing circles


#1

Ok, so i am having issues printimg circles. I always have, i juat never cared before, but now that i jave to make a part that i need to put a rod through, i need my circles to be, well, circular haha.

I use a factor of 12 for my sides of circles, and my printer prints them funny. I cant tell if it a printer issue or a modeling issue.

I do not have a file yet, but if i create just a tube and print, it looks funny. Some are bettwr than others. IE, a 0.68 inch diameter tube looks nice but a 0.25 hole looks crapy haha

Thanks


#2

If you are printing a circle with 12 sides, you are basically printing a 12-sided polygon. If you need something that is perfectly smooth, you may want to use 1 96-sided circle.

If I am in a situation where I need a smooth connection between a printed circle and something else (dowel, rod, screw, etc…) I tend to print a small, few-sided hole, and then drill the hole out afterward. Then i have a perfectly circular hole that is exactly the size I need.


#3

@TheOnlyAaron is right on the money. Think a moment about long established foundry practices: if a surface needs to be precisely smooth, flat, or sized, it is machined after the casting cools and “cures”. The materials used by most 3D printers shrink, settle, and warp as they cool. For precision holes you need to bore them out afterward.


#4

Adding the initial, smaller, low-quality hole will build up material to drill out… if you just drill a hole into a standard 3D print with fill, you will be drilling through a top and bottom shell, then infill and that may not be strong enough…


#5

For sure:) Im not printing a 12 sided circle, i print sides with factors of 12, so 24, 36, 48, etc haha.

Ok, yes, when in machine shop, thats what we did as well. We always bor3d the hole after.

I was just trying to make better circles because the ones i jave printed, especially from thingverse, the holes go eliptical on me… could be filament?

Thanks


#6

Elliptical holes from circular patterns might be due to non-uniform shrinkage after printing (possibly due to an asymmetric model, with more mass on one side of a hole than the other), or non-uniform X-Y-Z axis movement of the printer mechanisms.


#7

Hmm, ok. Maybe what i should do is make a test of a 48 sided circle or more since i dont want the print head to jerk around so much with super small lines, and see how it prints. Im thinking most of my issues are from premade parts on thingverse or with small holes about 0.25 inches or so.

Oh, and before i forget, what is best way to export stl? I just use the extension named “export stl” but im not sure if that produces the best stl files…

Thanks


#8

If you are on SU 2017, that is the best way to generate an STL (STL export is native in 2018).


#9

Ok, just want to make sure its producing enough triangles for smoothness:)


#10

Smoothness will all be based on the geometry you create in SketchUp. The exporter breaks the faces in the model into triangles, but does not do any additional “smoothing” upon output.


#11

Hmm, i was under the assumption that more triangles equals smoother polygons. Hmm, someone ill-informed me haha


#12

It does, I was just telling you that the process of exporting a STL does not create a smoother model. It will simply break the existing geometry into coincident triangles. You will have the same level of smoothness that you see in SketchUp.


#13

Ok, i see what you are saying. Let me explain my self better haha. Sorry, i was cooming meals for 40 boys when i replied.

Ok, is there a way to increase the amount of triangles using that extension? Bare in mind that the last time i opened that extension was about 3 weeks ago. Christmas is insane at my job haha

Thank you


#14

pedantically, it will simply ‘un-smooth’ the already existing triangles…

john


#15

Nope… all Export SYL does is… well… export STLs… to generate smoother geometry you just need to create more faces while modeling…


#16

That sounds good. Each modeling program i use is different:)

Well, when im off, im gonna trst out what was mentioned with circles.

Thanka


#17

Another modeling tip for producing 3D printed objects: do not use SketchUp’s visual smoothing and softening features. These features are great for producing renderings of smooth-looking surfaces (which is of course their purpose), but they seriously mis-represent what you get from a 3D printer. The printer will create the flat facets in the SketchUp model, not the sandpapered smooth look.

To see the difference, create a 24-sided circle and a 24-sided polygon. Push-pull them both into cylindrical objects. The extruded circle will look pretty cylindrical (because the edges formed when extruding a circle or arc or curve are automatically smoothed and softened); the extruded polygon will look like a many-sided prism, which is how it will print.

You can unsmooth and unsoften the edges in a circular extrusion by showing Hidden objects (in the View menu), selecting the dashed edges, and using the Entity Info window to un-tick Soften and Smooth - or at least Smooth. By the way, “smooth” in SketchUp means to blend the shading across edges, which is the main technique used to produce smooth-looking renderings (thus the feature’s name “smooth”). The term “soft” in SketchUp means to hide the edge, so that no visible line is drawn. You can leave the edges of an extrusion softened (i.e., hidden); it’s more important to disable “smooth” if you want to view the real faceting in the model.