Automated manufacturing systems are typically built around a core part or material transfer system such as a dial indexer, track based linear motion system, or palletized conveyor. These platforms fundamentally impact both the system’s output capabilities, as well as the overall footprin. Your decision to use one vs. another will be driven by various factors, such as meeting specific performance criteria, adapting to facility space constraints or the overall experience and ease of use.
From the outside, a robot appears to be an independent entity that can do many great things all on its own. But, in truth, it's the internal technology and end-of-arm tooling that enable the robot to effectively perform many types of assembly.