Solid group from 2 solid groups

I am unable to form a solid group from 2 solid groups using any of the solid tools. The picture shows the combination of 2 identical poles formed from a varying diameter tube and 2 spheres with different diameters. I have tried scaling the tubes prior to applying the outer shell tool, for example, with no success. I have also attached the skp file. Any thoughts?

scrap.skp (80.8 KB)

neither of your groups are solids…

turn on hidden geometry and you can see the additional geometry the is prevent ‘solidness’ near the axis of the sphere’s…

once you have 2 solids they will respond to the so;id tools…


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You two forms are indeed ‘solid’.
They should ‘Union’ OK…
They are also sufficiently large to [normally] avoid the ‘tiny geometry’ issues, where intersections in SketchUp fail if edges are shorter that about 1/1000"

However, their relative juxtaposition does result in a tiny facet edge which then fails to form.
Although it’s just a little over 1/1000" there’s another [less known] rule about the area of the possible facet so it still fails…
This results in a non-solid…
As reported in thomhom’s SoldInspector:

Although his alternative SolidInspector² reports, but fails to fix this issue.
However, if you zoom in and draw over one edge of the tiny ‘hole’, then it is then made into a solid…
My ‘SolidSolver’ Extension will fix this automatically for you too [it’s not foolproof but can fix some errors automatically]…

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Thank you for your response. It is interesting that the failure occurs near a facet edge, which suggests that increasing the number of facets in curved objects will actually reduce the likelihood that a solid object will result when applying solid tools. Frightening.

Thank you again!

There’s always the “temporary scaling-up of a component instance” trick to avoid this tiny-geometry firewall - see @DaveR posts about this…
SketchUp cannot create edges <1/1000" [or some facets with very tiny areas], so scale things up x1000.
For example: if you have made these two parts into a component and then copied and scaled an instance of it up x1000, then edited that instance to do the Union, then all is well and its contents are now reported as a solid.
Next delete that scaled instance.
Revert to the true-sized version…
Now its contents are still a solid - even with the tiny geometry.
SketchUp cannot create tiny geometry, but tiny geometry can exist !

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Thank you for the recommendation. A factor of 1000 works!

It seems to me that absolutes like < 1/1000" are inadequate for the range of applications. If Sketchup is only for architecture, then fuzz values like <1/1000" may be consistent with the typical size of the component. For other kinds of drawing then the fuzz value should be related to the component size, as long as machine precision permits. on 64-bit machines, then there may be little reasonable limitation to smaller fuzz values.

Another trick is to work in meters [without a units suffix], but think they are mm.
Then the small geometry issue is almost always avoided.
With 3d printing you can usually specify the size of the object etc.
Or when ready to print scale everything down [Tapemeasure tool - pick two points 1m apart and type in 1mm - the easiest way], then change from m to mm in Model Units…

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Thanks again for the tip, TIG!