Parts P1-P7 are machined first on a milling machine and then polished at a separate machine. Using the information in the following table, the minimum total completion time required for carrying out both the operations for all 7 parts is ________ hours.

Part | Milling (hours) | Polishing

Question

Parts P1-P7 are machined first on a milling machine and then polished at a separate machine. Using the information in the following table, the minimum total completion time required for carrying out both the operations for all 7 parts is ________ hours.

Part | Milling (hours) | Polishing (hours)
P1 | 8 | 6
P2 | 3 | 2
P3 | 3 | 4
P4 | 4 | 6
P5 | 5 | 7
P6 | 6 | 4
P7 | 2 | 1

Accepted Answer

33. By Johnson's two-machine rule the optimal sequence is P3,P4,P5,P1,P6,P2,P7. Computing milling completion then polishing completion gives a total makespan of 33 hours, not 32.

Solution

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