Question

... 9.12 South Carolina Furniture, Inc., produces all types of office furniture. The "Executive Secretary" is a chair that has been designed using ergonomics to provide comfort during long work hours. The chair sells for $130. There are 480 minutes available dur- ing the day, and the average daily demand has been 50 chairs. There are eight tasks: Task Must Follow Task Listed Below Performance Time Task (min) A4 B 7 C 6 AB E F,G a) Draw a precedence diagram of this operation. b) What is the cycle time for this operation? c) What is the theoretical minimum number of workstations? d) Assign tasks to workstations. e) What is the idle time per cycle? f) How much total idle time is present each day? g) What is the overall efficiency of the assembly line? PX

Answer 1

a)

4 min 7 min 6 min 5 min H 6 min 6 min B 7 min 8 min

b) Cycle time = (Production time per day) / (Output per day)

Cycle time = 480/50 = 9.6 minutes

c) Theoretical minimum number of workstations = (Sum of total task times) / Cycle time

49 min's / 9.6 min's

5.104 = 5 (rounded)

d, e, f

Stations	Task	Task time (minutes)	No of following tasks	Remaining un assigned time	Feasible remaining tasks
1	A	4	7	5.6	None
2	B	7	6	2.6	None
3	C	6	5	3.6	None
4	D	5	4	4.6	None
5	E	6	3	3.6	None
6	G	7	1	2.6	None
7	F	8	1	1.6	None
8	H	6	0	3.6	None
Total IDLE time				27.8

g)

Efficiency of assembly line = (Sum of all task times) / (Actual no of workstations)x(Cycle time)

= (49) / (8)x(9.6)

= 0.638 OR 63.8 %