I am posting an original assembly- this was thrown together as an example of the issue I am having, but it is not as complex as the actual (confidentially limiting) assemblies. We model them to have space for weld gaps, etc, and I need a way to find an exact volume. Hopefully this will at least give some insight. This is something I have posted about before, and I have tried the tutorial on the oil pan volume, which is great except for that my assemblies need a lot of stitching between components that I have yet to be able to figure out, because they don't always intersect nicely.
How do I make this assembly watertight so I can use the oil pan method of finding the volume, subtracting out all internal components and matching exactly the contours of the outermost assembly components?