Question

We have seven jobs each of which has to go through two machines M₁ and M₂ in the order  M₁ - M_{2 .} Processing times (in hours) are given as :

Jobs	A	B	C	D	E	F	G
Machine M1	3	12	15	6	10	11	9
Machine M2	8	10	10	6	12	1	3

Determine a sequence of these jobs that Will minimize the total elapsed time 'T', and idle time for each machine .

Answer 1

The order is M₁ M_2. hence required sequence is 

A

D

E

C

B

G

F

Or

A

E

B

C

D

G

F

 

Job seq.	Machine M1		Machine M2
	Time in	Time out	Time in	Time out
A	0	3	3	11
D	3	9	11	17
E	9	19	19	31
C	19	34	34	44
B	34	46	46	56
G	46	55	56	59
F	55	66	66	67

Total elapsed time T = 67 hrs. 
Idle time for Machine M₁ = 1 hr. 
Idle time for Machine M₂ = 17 hrs.