Hemo-tech, Inc, a biomedical technology and research laboratory, produces a standard blood filtering device on an assembly-line basis. Six basic tasks are performed along the assembly line

The time to perform each task and the tasks that must immediately precede each task are in the table below. Twenty pumps per 450-minute day must be produced by the assembly line.

Task Preceding Task Time to perform (min.)
A -- 5.40
B A 3.20
C -- 1.50
D B, C 2.80
E D 17.10
F E 12.80

(a) Draw the network diagram of the precedence relationships.
(b) Identify the absolute minimum and maximum cycle times.
(c) What is the cycle time required to meet demand?
(d) What is the minimum number of workstations required to meet the schedule?
(e) Balance this line using the most following tasks heuristic.
(f) What is the efficiency of the line obtained in part (e)?
(g) Can the efficiency of this solution be improved? Explain.

(a) The appropriate diagram appears below.
(b) The absolute minimum cycle time is 17.10 minutes (the longest operation). The absolute maximum cycle time is 42.80 minutes (the sum of all task times).
(c) The required cycle time is 450/20 = 22.5 minutes.
(d) The theoretical minimum number of stations is 42.8/22.5 = 1.90 or 2.
(e) The balanced line appears below.
(f) The line's efficiency is only 63.4%.
(g) There is idle time at all stations; removing the smallest amount of idle time (5.4 minutes) from all stations reduces the cycle time from 22.5 minutes to 17.1 minutes. The efficiency of the line rises to 83.4%.

Station Task Time (minutes) Time left (minutes) Ready tasks (#followers)
A4.,C3 .
1 A 5.4 17.1 C3 .,B3 .
C 1.5 15.6 B3 .
B 3.2 12..4 D2.
D 2.8 9.6 E1.
2 E 17.1 5.4 F(0)
3 F 12..8 9.7
Summary Statistics
Cycle time 22.5 minutes
Time allocated (cycle time ∗ #) 67.5 minutes/cycle
Time needed (sum of task times) 42.8 minutes/unit
Idle time (allocated-needed) 24.7 minutes/cycle
Efficiency (needed/allocated) 63.40741%
Balance Delay (1-efficiency) 36.59259%
Min (theoretical) # of stations 2