Page 274 - DMGT206_PRODUCTION_AND_OPERATIONS_MANAGEMENT

Unit 13: Production Planning and Control

Many other heuristics may be used instead of the Longest Operation Time (LOT) approach. Notes
Several computerized heuristics are available, and since different heuristics can lead to different
layouts, it may be worthwhile to want to try more than one approach. Mathematical and
computer-based Heuristic models can identify and evaluate alternative layouts far more rapidly
than manual or intuitive methods. Though these models use observation and experimentation
as they do theory, they have their limitations.
Practical Example 2

You’ve just been assigned the job a setting up an electric fan assembly line with the following
tasks:

2 1 1
1 .4
A B G
H

C D E F

3 .2 5 1 .2 .5 1

Task Time (Mins) Description Predecessors
A 2 Assemble frame None
B 1 Mount switch A
C 3.25 Assemble motor housing None
D 1.2 Mount motor housing in frame A, C
E 0.5 Attach blade D
F 1 Assemble and attach safety grill E
G 1 Attach cord B
H 1.4 Test F, G

Production time per day 420 mins
Max Production = = = 129 units
Bottleneck time 3.25 mins / unit
Production time per period
Required Cycle Time, C =
Required output per period

420 mins / day
C = = 4.2 mins / unit
100 units / day

Theoretical Min. Number of Workstations, N
t

Sum of task times (T)
N =
t
Cycle time (C)
11.35 mins / unit
N = = 2.702, or 3
t
4.2 mins / unit

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