Problem 1 - Twelve tasks, with times and precedence requirements as shown in the following table, are to be assigned to workstations that have a fixed machine cycle time of 1.5 minutes. Two heuristic rules will be tried: (1) greatest positional weight, and (2) greatest number of following tasks.
In each case, the tiebreaker will be shortest task time.
|
Task
|
Length
(minutes)
|
Immediate
Predecessor
|
|
a
|
0.1
|
-
|
|
b
|
0.2
|
a
|
|
c
|
0.9
|
b
|
|
d
|
0.6
|
c
|
|
e
|
0.1
|
-
|
|
f
|
0.2
|
d, e
|
|
g
|
0.4
|
f
|
|
h
|
0.1
|
g
|
|
i
|
0.2
|
h
|
|
j
|
0.7
|
i
|
|
k
|
0.3
|
j
|
|
l
|
0.2
|
k
|
b. Assign tasks to stations under each of the two rules.
(1) greatest positional weight (shortest task time as tiebreaker)
(2) greatest number of following tasks (shortest task time as tiebreaker)
c. Compute the percentage of idle time for each rule.
Problem 2 - A job was timed for 60 cycles and had an average of 1.5 minutes per piece. The performance rating was 98 percent, and workday allowances are 10 percent. Determine each of the following:
a. Observed time. (Round your answer to 1 decimal place.)
b. Normal time. (Round your answer to 2 decimal places.)
c. Standard time. (Round your answer to 2 decimal places.)
Problem 3 - A time study was conducted on a job that contains four elements. The observed times and performance ratings for six cycles are shown in the following table.
|
|
OBSERVATIONS (minutes per cycle)
|
|
Element
|
Performance
Rating
|
1
|
2
|
3
|
4
|
5
|
6
|
|
1
|
90%
|
0.44
|
0.50
|
0.43
|
0.45
|
0.42
|
0.46
|
|
2
|
85
|
1.50
|
1.58
|
1.47
|
1.51
|
1.49
|
1.52
|
|
3
|
110
|
0.84
|
0.89
|
0.77
|
0.83
|
0.89
|
0.80
|
|
4
|
100
|
1.10
|
1.14
|
1.08
|
1.16
|
1.16
|
1.26
|
a. Determine the average cycle time for each element.
b. Find the normal time for each element.
c. Assuming an allowance factor of 11 percent of job time, compute the standard time for this job.