Question

There are seven tasks in an assembly line, from which a product with a relative stable demand is produced. The time needed for each task (in minutes) and the relationships among tasks are in the graph below (note that activity C is linked to activity D). The assembly line operates 8 hours a day. The daily customer demand for the product is 120 units. Please design/balance this assembly line, so that supply and demand would be matched the most efficiently way possible.

• A (5) ----> B (3) ----> D (5) ----> E (1) -----> F (2) ------> G(4)
• C (2)------------------>

1. What is the desired cycle time (in minutes) of the balanced assembly line? (Keep two decimals if not exact, do not round. For example, 3.24923... will be kept as 3.24)   
2. Assumed the desired cycle time is 7 minutes, please used the assumed CT value to calculate the minimum number of workstations needed (round up to an integer number) for line-balancing, in order to achieve the best process efficiency.  
3. Assumed the desired cycle time is 7 minutes, please used the assumed CT value to balance the assembly line using the greatest positional weight rule. Which tasks would be assigned to the last workstation? (Letter only, NO space or comma between letters, e.g., ABDE)

Answer 1

Desired cycle time = available time/desired output = (8*60)/120 = 4 minutes

using the assumed minimum number of workstations needed = sum of task times/assumed cycle time = (5+3+2+5+1+2+4)/7 = 3.142857143 = 4(Rounded to integer)

Activity	Positional weight
A	20
B	15
C	14
D	12
E	7
F	6
G	4

Balanced assembly line

Workstation	Eligible task	Assigned task	Task time	Idle time remaining
I	A,C	A	5	2
	B,C	C	2	0
II	B	B	3	4
III	D	D	5	2
	E	E	1	1
IV	F	F	2	5
	G	G	4	1