Editing STL files in sketchup

I recently purchased some stl files for CNC and 3D printing and I want to modify them.
For example:
• Separate the base from a chess piece and convert the resulting two parts into a solid object.
• Create a cavity in the mesh.
I understand It can be done in blender but I gave that up years ago.
I tried a boolean subtraction but Sketchup crashed. The mesh has 184,000 faces and I can’t get the mesh to show.
Is it possible to edit stl files in Sketchup?

Certainly it’s possible to edit them in SketchUp. First thing I would suggest is to set the import units (in Options) to Meters so the thing comes in large enough to avoid the tiny face issue. I would also suggest choosing to merge coplanar faces.
Screenshot - 5_29_2022 , 9_17_51 PM

After you have the model imported, edit it like any other component. You might find it helpful to turn on Hidden Geometry so you can see the mesh.

Keep in mind that by definition the mesh will be triangulated which can result in a lot of geometry. Here’s a comparison of importing the same file with and without Merge Coplanar Faces selected. About four times the number of entities in the one on the right compared to the one on the left.

Thank you DaveR that sounds promising I’ll try that tomorrow. Also thanks for the fast reply, it got here as I was editing a typo.

Where do I find merge coplanar faces?

In the Import Options.

Sorry, didn’t see the STL attachment

That would be in the import dialog, under options.

Something else to know, we have recently fixed some things that could help importing and working on complex models. I think you have a subscription, and you could be using SketchUp 2022 if you wanted. You can try 2022 without removing 2021, and see if you get on well with it.

yes I have 2022 but I haven’t used sketch for a while and still rusty.
Many thanks

I didn’t get a dialog when I imported it. Can I get to the import option after importing?

It isn’t a new dialog that will appear, it’s a button in the initial import dialog. Like this:

It’s labelled ‘Configure’:

Thankyou I was looking for an options button.

Checked the merge faces, set it to meters as Dave suggested. and got this.

Is it OK to edit?

You can use extensions like Clean Up or Fix it 100 to reduce some of those edges, but you also just use Soften/Smooth to make them into hidden geometry.


OK and many thanks… This forum and your immediate help is awesome and very much appreciated. Thank you

I haveused cleanup3 but still have a problem I don’t know how to fix. Hope someone can help me fix the surface borders.

Surface borders normally indicate holes in the surface. Set the face style first to Monochrome and then to X-ray. That will help you see the holes.

Keep in mind that in some cases it may be easier to redraw the model or part of it than to repair bad geometry.

There were 3 loops inside the object with no face. I easily closed two loops by drawing a line between two vertex points of the loops resulting in one surface border that needs fixing. I can select the loop that needs fixing but after hour of trying to close the loop I am wondering if there is another way to do it without drawing a line. Is the line tool my only option?

The Line tool is usually the best option. sometimes tracing along an existing edge makes sense. Sometimes you have to triangulate but drawing in the diagonal. Again. sometimes it also makes the most sense to redraw from scratch.

Thank you for confirming that the line tool is my only option. If you know anything about chess you will know that a Staunton knight is very complex. I did consider doing it myself but I am far too slow. The model I worked on yesterday was very cheap with a lot of faulty mesh. This model cost $40 and it is a beautiful design. Its native creator is Maya and I’m sure it was a solid object when it was made. I downloaded several file types that I could open in SU and saves STL for CNCand 3D printing. I have asked the vendor to give me a stl file. In the meantime I’ll continue the fix in SU. Thank again for your help.