Question

# Use Johnson's rule to determine the optimal sequencing for the five jobs to be processed on...

Use Johnson's rule to determine the optimal sequencing for the five jobs to be processed on two machines in a fixed order (Machine 1 before Machine 2). The processing times are given in the table below.

 Job Machine 1 Machine 2 L 10 2 M 5 4 N 7 5 O 3 6 P 1 7

** Please show excel steps so i can see if I did this right** thanks

1. What is the optimal sequence?

2. What is the total flow time for this sequence?

• What is the optimal sequence? - P , O , N , M L
• What is the total flow time for this sequence? - 26 hours

Pls. see the details below:

 Processing times Job Machine 1 Machine 2 L 10 2 M 5 4 N 7 5 O 3 6 P 1 7 look for the lowest time 1 =MIN(B3:C7) which is Job P Machine 1 Next step Look for next min out of L M N O 2 =MIN(B3:C6) which is Job L Machine 2 so we place it at the end as Machine 2 Next step Look for next min out of M N O 3 =MIN(B4:C6) which is Job O Machine 1 so place at the 2nd position Next step Look for next min out of M N 4 which is Job M Machine 2 so placed at 2nd last position Optimal sequence is P,O,N, M,L
 Optimal Sequence P O N M L
• Total flow time of the sequence is 26 hours as I have placed the optimal sequence in order in an excel and job L finally end at Machine 1 at 26 hours
 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Machine 1 P O N M L Machine 2 P O N M L

Excel

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