Question

Question 1- Assembly Line Balancing

A ball-bearing assembly firm wants to set up an assembly line that must have an output of 60 units per hour. The work elements, task times and their precedence relationships are shown in Table 1:

Table 1

Work Element	Time (sec.)	Immediate Predecessor(s)
A	40	NONE
B	30	A
C	50	A
D	40	B
E	6	B
F	25	C
G	15	C
H	20	D, E
I	18	F, G
J	30	H, I

Required:
a. Draw the precedence diagram showing the task precedence and their times.
b. Determine the cycle time associated with the rate of output required.
c. What is the theoretical number of work stations required to satisfy this output rate?
d. Allocate the tasks to work stations taking into consideration the precedence requirements and using the LOT rule to break ties between feasible tasks.
e. What is the efficiency of the line and the idle time percentage?

Question 2- Forecasting
a. Name and discuss three qualitative forecasting methods. Give examples of situations in which each qualitative forecasting method may be used.
b. Olivia Ltd. Sells cars to local companies and private owners. The company tracked the sales for the last 6 years. Table 2 shows the sales level for those 6 years.

Table 2

Year	Sales
1	80
2	90
3	95
4	95
5	101
6	110

i. Calculate the slope
ii. Calculate the intercept
iii. Formulate the linear equation for this problem
iv. Develop a forecast for the firm’s annual sales for the next two years.

Answer 1

a)

b)

Cycle time = available time for production/desired output = 60 minutes/60 units = 1 minute = 60 seconds

c)

theoretical minimum no of workstations = sum of task times/cycle time = 274/60 = 4.566666667 = 5 (Rounded to next whole number)

d)

Workstation	Feasible task	Assigned task	Task time	Idle time remaining
I	A	A	40	20
II	B,C	C	50	10
III	B,F,G	B	30	30
	D,E,F,G	F	25	5
IV	D,E,G	D	40	20
	E,G	G	15	5
V	E,I	I	18	42
	E	E	6	36
	H	H	20	16
VI	J	J	30	30

e) Efficiency = sum of task times/(no of workstations*cycle time) = (274/(6*60))*100 = 76.11111111%