Printing a solid that is literally solid

Question from a raw recruit (me!) - I will be using a 3D print service to produce my finished model and I like to get it right to save wasting money.

I’m part way through creating a 3D model of a bracket. I’ve used lines, rectangles and circles together with move and push/pull to create a shape. The solid tools tell me that it’s solid - which I believe just means that all the lines that should connect, do connect (as SketchUp is a surface modeller).

When it’s printed I want the model to be solid, not hollow inside (as I need to tap a thread into one of
the holes I’ve created), and I’ve seen a comment that states it would need to be printed at 100% infill.

My question is, do I need to do anything in SketchUp to produce that infill or is it a 3D printer instruction?

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The SKP exported ‘solid’ will 3d-print ‘filled-in’.
[It’ll need to be exported into another file format to suit most 3d-printers]
The inside of the form is taken as being all ‘material’ [like a ‘rock’], unless you specifically adjust the SKP to have additional geometry forming a twin-walled ‘shell’, with a truly ‘hollow’ interior [like a ‘nutshell’].
Therefore, with the 100% 3d-printer setting it should be made from the same material all of the way through.
If you selected other settings for your 3d-printer [depends on the machine/process] it might then add a ‘foamed’ interior, to reduce the amount of material it uses.


As you’ve noted, SketchUp creates surfaces. As long as the surfaces join properly and are oriented correctly, 3D printing software will interpret the model as a solid. As a simple example, if you create a rectangle and pull one of the faces to make a brick shape, it will print as a solid 3D object. However, when adding, removing, and intersecting surfaces, you may inadvertently end up with some surfaces that are not joined correctly or whose orientation is reversed (the solid is defined by bounding polygons that point “away” from the solid material).

Once you’ve got your model ready, you can export it as a STL or DAE file that most printing services can readily use. I’ve had good luck with using DAE files for both nominal solid models as well as colored and textured models.

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Thanks for the help. While I’m still a beginner I’ve learned a lot in the last few days and I’ve cleared out a fair bit of internal geometry which was creating ‘pockets’ in the model. I found that using the k key was useful to spot problem areas. When I send it for printing I’ll make sure to include the information that I need it to be solid.

While creating my model I thought I’d been very careful picking up on the inference points throughout, but I still had trouble creating a solid. After installing the Solid Inspector I was able to narrow down the areas that needed work but found that I had to zoom in VERY closely to make sure I created a watertight finish. Thanks for the advice.

Note that 100% infill can be very costly. I think most time people choose a much lower infill like 20% to save on cost of the plastic. If cost is not an issue, then go for it. but there are methods to save cost if you’re interested.
-If the printer is capable, only make one section 100% infill (where you need to tap a thread) and the rest less.
-I’ve heard of people using 0% infill (so it’s hollow), drilling a hole and filling the inside with glue, letting it dry and then achieving a very similar result of a solid object
-While I’m not sure if this idea will be cheaper, but using resin instead of PLA as a material. It’ll have to be molded, but it’ll be guaranteed 100% solid and resin is quite strong if you plan on tapping a thread, but much heavier than PLA.