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.