I tried unions for a train with rivets (Ball-shaped parts), detailed modeling, and a funnel, modeled after a Lionel train. The excessive amount of parts means that whenever I attempt to union even a small amount of rivets (3 is the maximum I can do without breaking studio), The game freezes and I have to close it. Because the rivet balls are just overlapped into the cylinder used for the front of the train, I can't use joins like weld or studs and inlets on them. I can't anchor them, either. Please help!
This can be done through scripts too, you can check out this page for more info.
Group the parts you want welded, then insert a qPerfection Weld script from the Toolbox. Make sure model is anchored if you use qPerfection. You could also just use weld constraints. Those worked for me when I make Ferrari F40 rims with rivets.