Question

Line balancing:

With considering the following tasks:

task number	avg. performance time	number of successors
1	5	7
2	3	6
3	6	4
4	8	5
5	10	3
6	7	3
7	1	2
8	5	0
9	3	0

  

a. Estimate the cycle time to reach minimum idle time and end up having 4 workstations.  

b. Imagine the considered cycle time is 17. Which of the following methods gives us the best solution? Why? (you need to compare the solutions numerically).

o Largest‐candidate rule   

o Kilbridge and Webster’s method   

o Line of Balance (LOB)  

o Ranked positional weight  

Answer 1

We have ,Number of workstations N=Sum of task times/Cycle time

therefore ,Cycletime =Sum of task times/N

From the given data, Sum of task times =48

Cycle time =48/4 =12

b. Given cycle time =17

a. Longest candidate rule

b.Kilbridge and Webster's method

Ranked positional weight

All the above three methods have same number of workstations =4

Efficiency =Sum of task times/(number of work stations * cycle time) =70.58 %

Line of Balance :

Tc =17

Tr =repositioning time for movement of the product from one station to next.

Assume Tr =0.7

Ts=Tc-Tr=17-0.7 =16.3

Line efficiency =Sum of task times/(number of work stations *Ts) =48/4*16.3=73.61 %

So,the line of Balance method gives higher efficiency than the rest of the methods and hence is the best method.