Please solve the following problem related to Chapter 6
1. 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 follows:
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:
a. Draw the precedence diagram.
b. Determine the minimum cycle time, the maximum cycle time, and
the calculated cycle time.
c. Determine the minimum number of stations needed.
d. 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.
e. Compute the percentage of idle time for the assignment in part d.
[Hint: Please read page 262-264 in the textbook. Please read Example
1 on page 264-266, and Example 2 on page 267-269.]
Please type your answer and the steps of computation in a Word or
Excel file.
(a)
(b)
CT_{min} = the longest task time = 1.2
minutes
CT_{max} = sum of all the task times = 4.9
minutes
Calculated cycle time = 8 x 60 / 240 = 2 minutes
(c)
Minimum number of stations = CT_{max} / Calculated cycle time = 4.9/2 = 2.45 i.e. 3 stations
(d)
Sattions | Task | Duration (minutes) |
Time left (minutes) |
Ready tasks (# followers) |
A(4),D(2) | ||||
1 | A | 0.3 | 1.7 | D(2),B(3) |
B | 0.6 | 1.1 | D(2),C(2) | |
C | 0.3 | 0.8 | D(2),E(1) | |
D | 0.5 | 0.3 | E(1),F(1) | |
2 | F | 0.8 | 1.2 | E(1) |
E | 1.2 | 0 | G(0) | |
3 | G | 1.2 | 0.8 |
(e)
% idle time = 1 - (Flow time / (# stations x cycle time)) = 1 - (4.9/(3*2)) = 18.33%
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