The assembly process consists of sequences of complex tasks. Implementing automation to an assembly line is still quite challenging since human still plays a significant role in the assembly process. On the other hand, robots are able to achieve much higher performance than humans, especially when performing low-level cognitive tasks. Therefore, the robots’ advantages can be combined with human abilities to improve the assembly process. Humans will frequently see robot integration in the assembly process in the future. This paper presents a human-machine collaboration (HMC) design for a car-toys assembly line and investigates the assembly line performances. Three scenarios are presented and analyzed in this work, e.g., the manual assembly line, integrating one collaborative robot, and integrating two collaborative robots. The performance analysis such as flow time, throughput, and utilization are done using Tecnomatix Plant Simulation. The scenario which has the best performance has been identified as a recommendation for future improvement of the existing system