Question

As part of a major plant renovation project, the industrial engineering department has been asked to balance a revised assembly operation to achieve an output of 240 units per eight-hour day. Task times and precedence relationships are as you know you can follow:

Task	Duration (minutes)	Immediate Predecessor
A	0.3	-
B	0.6	A
C	0.3	B
D	0.5	-
E	1.2	D
F	0.8	C
G	1.2	E, F

Do each of the following:

Draw the precedence diagram.

Determine the minimum cycle time, the maximum cycle time, and the calculated cycle time.

Determine the minimum number of stations needed.

Assign tasks to workstations on the basis of most following tasks. Use shortest processing time as a tiebreaker. If ties still exist, assume indifference in choice.

Compute the percentage of idle time for the assignment in part d.

Answer 1

b) Minimum cycle time = Maximum task time= 1.2 mins

Maximum cycle time =Total duration = 4.9 mins

Calculated cycle time = OT/output = 8*60/240 = 2 mins

1. Minimum no of stations required= Total duration/cycle time = 4.9/2 = 2.45 = 3 stations

So, task precedence on basis of most following task and shortest processing time as tiebreaker is:

A-B-C-D-F-E-G

Total time at workstation= cycle time = 2 kins

Workstation 1: Task 1: A

Time left = 2-0.3 = 1.7

Task 2: B

Time left= 1.7-0.6 = 1.1

Task 3:C

Time left: 1.1-0.3= 0.8

Task 4:D

Time left=0.8-0.5=0.3

Workstation 2:

Task 1: F

Time left=2-0.8=1.2

Task 2: E

Time left= 1.2-1.2=0

Workstation 3:

Task 1: G

Time left=2-1.2=0.8