Using the data provided in the example (Example 2.7) create a multiple activity chart for the case in which the operator is assigned two machines as opposed to three. What is the length of the repeating cycle?

For the situation illustrated in Figure 2.18, it takes 0.5 minute to travel between machines 1 minute to load a machine, 1 minute to unload a machine, 6 minutes of automatic machine time, and 0.5 minute to inspect and pack a finished part. As shown, the analysis begins with each machine empty and the operator standing in front of Machine 1 (M-1). The operator loads M-1, walks to M-2, loads M-2, walks to M-3, loads M-3, walks to M-1, unloads M-1, loads M-1, inspects and packs the part removed from M-1, travels to M-2, and so forth. As shown in Figure 2.18, it takes 12 minutes for the operator and three machines to achieve a steady-state condition; thereafter, a repeating cycle of 9 minutes in duration occurs. (In other words, if nothing interrupts the activities of the operator and the three machines, the 9-minute cycle will repeat indefinitely.) Under conditions similar to those depicted by Figure 2.18, a deterministic model can be developed to determine the optimum number of machines to assign to an individual operator. To facilitate the development of the model, let a concurrent activity time (e.g., loading and unloading a machine) b independent operator activity time (e.g., walking, inspecting, packing) t independent machine activity time (e.g., automatic machining time) n ideal number of identical machines to assign an operator m number of identical machines assigned an operator Tc repeating cycle time

Io idle operator time during a repeating cycle Im idle time for each machine during a repeating cycle