Splinter can target and exile cards that aren’t always artifacts, but are artifacts when Splinter is cast and resolves (such as an animated Stalking Stones). Splinter’s exile effect only looks for cards by name, not type.

The copies must be found if they are in publicly viewable zones. Finding copies while searching private zones is optional.

Does not exile other cards of the same name that are on the battlefield. Just from the graveyard, hand, and library.