Question

The following data is given for an assembly line:

Task	Time(Minutes)	Precedents
A	5	None
B	3	A
C	4	B
D	3	B
E	6	C
F	1	C
G	4	D,E,F
H	2	G

The pace is 8. Balance the assembly line.

What is the efficiency of the assembly line?

Suppose market conditions required a reduction of pace by 30 percent. What would you recommend?

Answer 1

Given:

Pace or Cycle Rate = 8 mins

Theoretical or Minimum number of workstations= sum of total task times / cycle time

                             = (5+3+4+3+6+1+4+2) / 8 = 28 / 8 = 3.5 workstations = 4 workstations

Task Table

Task	Task time	Precedence
A	5	NA
B	3	A
C	4	B
D	3	B
E	6	C
F	1	C
G	4	D,E,F
H	2	G

                                                                                                                                       

The total station time is nothing but the cycle time. So, total station time of each station is 8 min

In order of longest operation time and Task precedence, task order: A->B->C->D->E->F->G->H

Workstation 1:

                             First task = A

                             Time left= 8 – 5 = 3 min

                             Second task = B

                             Time left= 3 – 3 = 0 min

So, workstation 1: A->B

Workstation 2:

                             First task = C

                             Time left= 8 – 4 = 4 min

                             Second task = D

                             Time left= 4 – 3 = 1 min

So, workstation 2: C->D

Workstation 3:

                             First task = E

                             Time left= 8 – 6 = 2 min

                             Second task = F

                             Time left= 2 – 1 = 1 min

So, workstation 3: E->F

Workstation 4:

                             First task = G

                             Time left= 8 – 4 = 4 min

                             Second task = H

                             Time left= 4 – 2 = 2 min

So, workstation 4: G->H

Work Station	Tasks	Workstation Time	Idle Time
1	A->B	8 min	0 min
2	C->D	7 min	1 min
3	E->F	7 min	1 min
4	G->H	6 min	2 min

Efficiency =(sum of total task time/(cycle time * no of workstations)) * 100

               = (28/(8*4))*100 = 87.5%

Case II:

Pace is reduced by 30%

New Pace or Cycle Time = 8 – (0.3*8) = 8 – 2.4 = 5.6 mins

This is not possible as the New Cycle Rate will not be able to accommodate activity E, whose task time is greater than the new cycle rate.