3. Metal Box Production

Metal window boxes are manufactured in 5 basic colors in a small plant in Bangkok. The manufacturing process consists of 3 operations: stamping, painting, and assembly.

Each window box is made up of three pieces: a base (one part A) and two sides (two part B's). The parts are fabricated by a single stamping machine which requires a setup time of 100 minutes whenever switching between the two part types. Once the machine is setup, the processing time for each part A is 1 minute, while the processing time for each part B is 30 seconds. Currently, the stamping machine rotates its production between one batch of 300 for part A and one batch of 600 for part B. Completed parts are moved from the stamping machine onto the painting station.

At the painting station, parts are painted by a robot in 1 of the 5 colors. The robot takes 30 seconds to paint one part A and 15 seconds to paint one part B. The robot can instantly switch between painting the two different parts to be painted in the same color; but when a switch in color is needed, it would require 20 minutes for setup. Once a piece is painted, it must wait 120 minutes to dry before moving to assembly. The painting robot is currently programmed to change color every time it finishes one batch of component sets (i.e., 300 of part A and 600 of part B).

At assembly, parts of the same color are assembled manually to form the finished product. One base (part A) and two sides (two part B's) are required for each unit of the final product. Each product requires 2 minutes to assemble.

The factory is running on a 24 hours a day, 7 days a week basis, and the transportation batch between two steps is set equal to the production batch.

(a) Identify the bottleneck for the current process and calculate the maximum daily flow rate in terms of the # of units of finished products produced per day. What is the minimum flow time for a batch of 300 units of finished products (i.e., from the time the stamping operation starts for a batch to the time the complete batch of 300 window boxes is assembled)? What is the capacity on a per hour basis?

(b) What impact would doubling the batch sizes at the stamping operation have on total daily capacity? (suppose that the required number of set-ups for different steps remain unchanged). Explain qualitatively what other, possibly negative, effects this would have.

(c) Management is considering investing in a setup reduction program for the stamping machine. Suppose the setup time could be reduced to 20 minutes. What will this improvement affect the capacity? given that the batch sizes remains the same (i.e., 300 for part A and 600 for part B)?