Solid Joins in SketchUp

[jimhami42]

I thought I would pass along a time-saving tip if you’re going to 3D print your model. There has been a lot of discussion about properly intersecting surfaces and then cleaning up the results. And if you miss one little polygon, the whole thing could get rejected by the print software or leave missing gaps in your model.

I’ve had good luck grouping simple shapes and then just positioning them where I want them. I then export the model as a DAE file and the print software will see them each as solid items and do the joins for me.

As an illustration, I took a 1.25" diameter circle, created several internal offset circles, and then used the Push/Pull tool to add 0.150" thickness and some 0.050 x 0.050 grooves/ribs. When I was done, I grouped the result together, Then I used the Text tool and created the letter “B” (which is already in a group). Next I created a 0.050 x 0.050 square and used the Push/Pull tool to create a rectangular solid. I grouped this as a component and then added three copies. The last step was to create a small doughnut with a 0.100 hole and group that as well.

Leaving these in groups and then arranging them as desired:

I exported the model as a DAE file and imported it into MeshLab to see how it looked (note the faceted curves on the letter):

I uploaded the model to a 3D printing website and their software produced this rendering:

Without needing to do any tedious intersections, etc., it took less time to create the model and upload it than it did to document it as an example.

Some observations: Depending on how you place your geometry, common edges whose node points don’t align may cause a problem. This violates the (nearly) universal requirement for a manifold volume*. Also, this only works for additive shapes; I haven’t yet found an easy work-around for holes.

Also worth noting, as many of you are already aware, smooth-looking in SketchUp doesn’t always mean smooth printing. The detail shown below is an example of using many many points to create a smooth print result:

While I used simple steps to illustrate the process, I previously made a similar pendant, but I created the letter “B” with many more points than the default Text tool:

(shown in 24K gold-plated steel)

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*Manifold Volume (also known as “watertight”) - The illustration below gives a good explanation of what to avoid (clipped from a tutorial at scultpteo.com):

[mmorao]

Hi Jim, IIUC you mean that we can group elements together so that they will “float together in place” without an Intersect operation, and they’ll print out well. To me this is excellent as I work with complex shapes and even with big objects intersections may create micro-geometries that are difficult for SU.

It is also interesting to notice that you smoothed objects by creating homogenous fine resolution volumes like your 12500 entities doughnut (that’s how they make you fat!) but then your pretty smooth shape was nullified by the granularity of the addictive printing process. So depending on the material, there has to be a limit after which further smoothness isn’t necessary as it won’t have any effect on the printed object.

[jimhami42]

I’m not sure about other printers and print-shops, but the Shapeways site seems to have no problem with independently “floating” objects as long as each of them is watertight. It makes things a whole lot easier!

And, yes, the donut was way, way overkill, but the site had no problem with it (IMHO, it’s better to have too many polygons than too few).

[mmorao]

And who am I to disagree with you! Triangles! Triangles Abounding! That processor has to do something for a change But that “floating interception” idea does save you from a lot of heartburn! Thanks Jim!