Question

A shop operates 400 minutes every day. The shop manager wants an output of 300 units per day for the assembly line. Twelve tasks, with time and precedence requirements as shown in the following table.

Task	Length (min)	Immediate Predecessor
A	0.1	- -
B	0.2	A
C	0.5	B
D	0.6	C
E	0.1	- -
F	0.2	D,E
G	0.4	F
H	0.1	G
I	0.2	H
J	0.6	I
K	0.3	J
L	0.2	K

Compute the efficiency (in terms of %) after balancing the assembly line.

*Round your answers to 3 decimal places in your calculation if necessary.

Answer 1

The precedence diagram of activities as follows :

A	E
B
C
D
F
G
H
I
J
K
L

Since 300 units of output is required in 400 minutes,

Cycle time required = 400/ 300 minute per unit = 1.33 minutes per unit

Total duration of all tasks = sum of all tasks = 3.5 minutes

Theoretical minimum number of workstations = 3.5/ 1.33 = 2.63 ( 3 rounded to next whole number )

Assignment of tasks to workstations ( so that total duration of tasks against any workstation does not exceed cycle time of 3.5 minutes)

Workstation	Tasks	Duration ( Minutes)
1	A, B , C, E	0.1 + 0.2 + 0.5 + 0.1 = 0.9
2	D,F,G,H	0.6 + 0.2 +0.4 +0.1 = 1.3
3	I,J,K,L	0.2 + 0.6 + 0.3 +0.2 = 1.3

Efficiency of the balanced line

= Sum of all tasks / ( Cycle time x Actual number of workstatios) x 100

= 3.5/ ( 3 x 1.33) x 100

= 3.5/3.99 x 100

=87.72%