Question

Consider a manufacturing cell in company ABC that repairs defective computers. Computers arrive to the cell and wait in a single queue to be processed on a first-come-first-serve basis by one repair operator who can only work on one computer at a time. Assume that the simulation begins at time 0 with a computer (Computer #1) already being processed (scheduled to be complete in 30 minutes) and another computer (computer #2) waiting in the queue (with a process time of 80 minutes). The time between the arrival of subsequent computers to the cell and their process time is as follows:

	Minutes until Next Arrival	Required Minutes of Processing Time
Computer #3	120	130
Computer #4	60	55
Computer #5	45	110
Computer #6	190	30
Computer #7	160	15
Computer #8	45	80
Computer #9	90	60
Computer #10	70	100

For example, computer #3 will arrive at time 120 and require 130 minutes of service. Computer #4 will arrive at time 180 (120+60) and require 55 minutes of service.

Construct a simulation table and perform a simulation for completing the processing of all ten computers. The objective of the simulation is to determine the following statistics:

1. Average time in the queue for a computer.
2. The average time a computer is in the cell (waiting and being processed).
3. The average number of computers in the system (waiting in the queue and in service), and,
4. The utilization of the cell operator.

Answer 1

1) Average time for a computer in queue =

time at which service of previous computer is completed - time at which current computer arrives

2) Average time a computer is in the cell = Average waiting time of computer in queue + processing time of it

3) Average number of computers in the system is 1

4) Utilization of cell operator = = 700 / 880 = 0.7954 or 79.54%

Computer number	Time at which computer arrives in queue	Time at which operator takes computer for repair	Average time of computer in queue	Average time of computer in cell
1	0	0	0	30
2	0	30	30	110
3	120	120	0	130
4	180	250	70	125
5	225	305	80	190
6	415	415	0	30
7	575	575	0	15
8	620	620	0	80
9	710	710	0	60
10	780	780	0	100