Regrouping by itself should not change the geometry so if the object isn’t solid the first time you make the group or component, exploding it and remaking it shouldn’t change anything.
I would suggest refining the modeling process to avoid creating geometry that results in nnon-solids. It’s not that difficult. It’ll save you time and make the whole modeling process easier. Every component in every model I make is solid and I rarely ever have to repair the components to make them solids. I watch for and take care of the bad geometry immediately if it occurs. That’s not really anything special. You can do it too.
Confession: I did not make this model, it is an stl I downloaded (along with others). Usually the SU import procedure messes up the stl, even when i am modelling at 1000x scale. In this case I want to make some changes using solidtools, and I could not get the object to play ball. I must have fixed 50 errors on this file before SI2 reported that everything was OK, and I got stuck. I know that ungrouping/grouping should not change anything, but in the past it has worked for me.
In the case of these stl files, my printer slicer and Meshmixer do not report any issues with the model. But if I want to do some work on the file in SU, the import process nearly always creates errors. Since the file is in mm and I import into meters, I tend to avoid issues with small triangles, but there will still be some. Other sorts of errors include faces on top of each other and “foldings” of the mesh which create impossible intersections. Maybe the built-in stl importer has some bugs?
I have printed items that were designed by others. The slicer did not show any errors, and the items printed OK. I opened the .stl and found many holes in the mesh that could not be repaired without much effort. I also will not use files from others.
Sometimes using stl files from others is unavoidable, due to lack of skill or lack of time. I have checked stl files with MeshMixer, which showed no errors, but were full of holes when imported into SU, even at 1000x scale to avoid the tiny triangle problem. I suspect the stl importer is buggy. Now I know that using Solid Inspector and Solid Inspector 2 will help, I can work OK.
You might find it helpful to break the project down into smaller solid objects. When placed together in the model, the slicer should treat them as a single object. Using one of my models as an example, I have seven different solid components in the selection. (The bar is a separate solid component but I left it out of the selection.)
