Keyway Design for 3d print

Utilizing the free version of sketchup and trying to design these keyways/slots into the back of an emblem for 3d printing.

As you may be able to tell, a round peg goes into the circle and then slides under the slot to secure itself to the surface (of a car). Putting the circle and keyway into the back of the emblem is ‘simple’, I’m having problem with the overhang… any pointers would be appreciated!


Is the overhang even necessary? If you modeled the keyway correctly, then it should attach securely even if the surface is planar. Right?

If it is necessary, then I’d recommend push pulling the face to the correct depth. No need to overcomplicate things. Right?

Yes, even though the design is planar and will lie on a flat surface, that surface is vertical and on the exterior of the car.

I managed to design the keyways in a fashion that will work (not pretty in CAD), but now I’m facing a new issue… When i put these to print, the keyways print solid while the main backing doesnt print at all. I’m guessing because its a single wall, but I cant figure out how to fill it!

Side Emblem.skp (1.7 MB)

There are all sorts of problems with your model that would prevent it from printing correctly. Reversed faces, missing faces,edges shared by more than two faces, internal faces and edges… Compare this file with yours.


After fixing it.

Side Emblem.skp (298.9 KB)

Also notice after fixing it and purging unused stuff, the file size is reduced by more than 80%.

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Huge thanks, and with lightning speed! Forgive me, this is my first self designed project thats going to print, what do you mean by internal faces and reverse faces? I’m assuming that’s what the model was showing me for the back side (all blue)?

Thanks again!

Faces in SketchUp have fronts and backs. The default back face color is blue. As far as 3D printing goes, the face orientation tells the printing software which side gets the material and which side is air so correct face orientation is critical.

Internal faces are inside the 3D geometry. They don’t serve any useful purpose and also create problems for 3D printing.

Keep face orientation correct and keep your models clean. It makes your work much easier.

One easy to understand definition of solid as far as SketchUp is concerned is that every edge must be shared with exactly two faces. No more, no less.

In your model where there were missing faces on the bottom of the horse, there are edges bounding only one face, not two. In the join between the N and I in Serenity, the vertical edge is shared by 4 faces. If you look closely at my version, you can see that I provide a little separation between them.

Dave, what’s your easiest fix for missing faces? I’ve seen with importing STL that on small models there may be hundreds of faces not filled in. Redrawing one edge fixes most cases, but that would take a long to do. Is there a quicker way?

Well, in this case there weren’t many holes to fix, thankfully. I just traced edges with the Line tool to heal the missing faces.

I would head the problem off during importing by setting the import units to Meters. There are some extensions that will make faces but they can often create more work than they save.

That makes sense! Thanks again DaveR!

IRT using the line tool to heal the missing faces, you may have noticed I had to do this on the inside of the key holes… it was quite tedious, and not very pretty in the end… but it created a solid face. The internal/external faces thing made a lot of sense!

Yes. There were some problems in there still.

I think you could approach the keyway slots a little differently and save yourself a bunch of work. One thing you should do and didn’t do when drawing the keyway is drag out your circles on axis.

That helped, thanks. Still some holes though.

I’m playing with CleanUp3 too, to try and make the model less complex, and so fewer holes to fill.

I try to avoid importing STL files if I can. Since they are, by definition, triangulated, you’re already starting at a disadvantage when you import it into SketchUp. If I do have to import an STL, I give it a look over and judge how much work I’ll have to do to repair it. CleanUp3 can help but even then, I might still redraw it from scratch to save time and to make sure everything is right.

I’ve been attempting to print this, and the base is always failing. I think because it’s made up of thousands of triangles. This after-CleanUp3 version has a handful of triangles to do the same base.

I’d delete and redraw the base from scratch.

I did try that. The difficulty was the bottom of the hooves, I think they need to match exactly. I did some intersecting to try and get that, but I was working at a smaller scale at the time, and ended up with lots of gaps. Might try with the monster version I have now.

Three words: The Dave Method.

Here’s how the STL version looks.

Funny how you’re quoting someone who quoted you! In my case I can work at a huge size, the print app scales the model to fit. I don’t think I need things in components to then scale down, they can stay massive.