Case report
Analytic exercise: Designing a Manufacturing Process
Toshiba´s Notebook Computer Assembly Line
Whenever a new model is introduced at Toshiba, management attempts to improve the assembling process in terms of increasing productivity and decreasing costs. Attentiveness is directed towards reducing the amount of components and simplifying production and assembly.
Manufacturing engineering manager Toshihiro Nakamura introduced a prototype assembly sheet concerning the new notebook model. The following precedence graph examines the process sheet.
Task numbers: 1-17; task time in seconds (in brackets).
1 (75) 2 (61) 14 (11) 15 (310) 16 (60) 17 (60)
3 (24) 4 (36) 5 (22) 6 (39) 7 (32) 8 (44) 9 (29) 10 (26) 11 (52) 12 (7) 13 (5)
The assembly line consists out of 6 workstations. Labour time (in seconds) for each workstation is indicated in brackets. Workstation 1, task 1 (75). Workstation 2, tasks 2 and 3 (85). Workstation 3, tasks 4, 5 and 6 (97). Workstation 4, tasks 7, 8 and 9 (105). Workstation 5, tasks 10-15 (101). (Workstations 6, 7 and 8 are operating the software load). The final workstation 9 handles tasks 16 and 17 (120). The sum of task time therefore equals 583 seconds.
The assembly line is designed assuming that one notebook would be assembled every 2 minutes by six workers. Therefore, daily capacity of the assembly line would be 225 units (450 minutes operating time per day), assuming that on each one of the six workstations a computer is positioned at the beginning of the day.
Initial production for the new model is 150 units per day, increasing to 250 the following week and eventually up to 300 units, depending on process success.
The bottleneck in this assembly line is located between workstation 4 and 5. Workstation 4 completes its tasks (7, 8, and 9) within 105 seconds whereas workstation 5 finishes after 101 seconds. This results in a slack of 4