Question

Question 2: The times required to complete each 2. The times required to complete each of eight jobs in a two-machine flow shop are shown table that follows. Each job must follow the same sequence, beginning with machine A and moving to machine B. Job TIME (hours) Machine A Machine B OOOO a. Determine a sequence that will minimize makespan time. b. Find machine B's idle time. c. For the sequence determined in part a, how much would machine B's idle time be reduced by splitting the last two jobs in half?

Answer 1

Answer a:

Step 1 Find out the sequence of jobs that is less than the overall time by the following:

the shortest processing time is 2 hours in Job e at Machine A. So, Job e is scheduled first. Similarly, the least time taken Job is JOb b at machine A which is scheduled second. The next is Job f by 4 hours at machine b, is place in the last. Even every job is being analyzed similarly according to the performance and schedule of activities being created in what time taken by them in each machine. The schedule for jobs which reduces the time is :

e-b-g-h-d-c-a-f

Job Machine A Machine B Schedule

a 16 5 7

b 3 13 2

c 9 6   6

d 8 7 5

e 2 14 1

f 12   4 8

g 18 14 3

h 20 11   4

Answer b:

Machine A

e(2)

b(3)

g(18)

h(20)

d(8)

c(9)

a(16)

f(12)

Machine B

2

e(14)

b( 13)

g( 14)

h( 11)

d(7)

c( 6)

9

a( 5)

7

f( 4)

As the time taken by each job in each machine as the table shows is done to calculate the idle time in machine B. The bold portion in the table shows the idle time is as follows-

Machine B idle time is 2+9+7= 18 hours

Answer c: After finding out the sequence in part (a) i.e. e --b -g--h--d-c-a-f the idle time of machine B is 18 hours so after reducing by splitting the last two jobs in half-

New idle time is 16 hours saving 2 hours.