Transcript Slide 1

• Workstation
• The assembly design is based on the
demand for the peak quarter of year 5
• Cycle Time = 14.326 sec./unit
• There will be three assembly lines that run
two eight hour shifts with 102 workers and
4 supervisors
• Capital equipment will cost $118,180 for all
three assembly lines.
Annual Expenses
A
B
C = (B/420,000)
D = ($ annual exp. Y5) x ( C )
Year
Production Quantity
Production Ratio
Annual Expenses
1
413277
0.984
$140,557.01
2
414958
0.988
$22,222.19
3
416639
0.992
$22,312.21
4
418319
0.996
$22,402.18
5
420000
1.000
$22,492.20
Introduction
• This analysis will contain a detailed layout in AutoCAD of
the assembly area, capital costs, and the annual
expenses that will be required for years 1-5 based on the
year 5 demand. The analysis will explain the techniques
used to define the work elements needed for assembly
and how standard times were developed for these
elements. The analysis will also cover the calculations
used and assumptions made in the design. Direct labor
and capital costs of the assembly line will also be shown
in the methods analysis. The design has been frozen
due to the time constraints of this analysis.
Work Elements
• An element consists of a group of small
operations that must be performed to
successfully assemble the product.
• Work elements for the assembly of the
Ultraquiet Foot Spa were determined by
disassembling the prototype and deciding
how to reassemble it.
• There is a prototype box with the flaps
labeled for elements 34, 37, and 38.
Standard element times were obtained by performing a time study.
This time study consisted of performing ten time trials on each
element. The averages of each of the ten trials were then computed.
Work
Element
Time
1
Time
2
Time
3
Time
4
Time
5
Time
6
Time
7
Time
8
Time
9
Time
10
Avg. Time
Std
Dev
1
45.15
48.26
43.34
45.4
50.01
42.25
44.76
46.08
48.12
45.21
45.86
2.35
2
60
60
60
60
60
60
60
60
60
60
60.00
2.00
3
41.94
44.51
39.48
45.34
44.11
39.72
41.21
42.35
44.09
43.13
42.59
2.01
4
37.16
33.2
35.32
33
34.19
36.11
31.23
34.2
32.65
31.44
33.85
1.94
5
13
10.33
11.18
11.4
10.8
11.17
12.4
11.8
11.75
12.15
11.60
0.79
6
28.86
24.65
27.84
29.07
23.28
27.83
25.2
27.45
24.97
26.18
26.53
1.96
7
18.87
20.6
18.35
18.83
17.25
17.03
18.93
19.93
20.01
18.24
18.80
1.16
8
54.64
57.54
53.89
55.91
54.01
51.1
53.23
59.13
57.36
51.29
54.81
2.67
QTY
9
2
16
16
16
16
16
16
16
16
16
16
16.00
1.00
10
2
65.12
56.15
61.78
54.89
62.15
58.48
59.44
57.7
63
58.3
59.70
3.23
11
2
19.05
20.28
18.31
19.4
18.32
20.57
19.07
20.63
19.15
20.68
19.55
0.93
12
54.26
49.71
52.78
47.79
56.49
48.79
50.49
55.3
56.01
57.86
52.95
3.56
13
38.41
37.2
31.3
36.6
34.5
36.6
30.4
31.3
34.6
33.2
34.41
2.80
14
14.2
13.78
11.5
10.8
8.5
9.6
8.78
9.25
9.17
10.2
10.58
2.02
15
20
20
20
20
20
20
20
20
20
20
20.00
1.25
16
8
8
8
8
8
8
8
8
8
8
8.00
1.00
17
26.45
25.11
23.2
24.8
22.76
25.32
23.4
22.87
25.17
23.87
24.30
1.24
18
22.1
21.7
19.28
21.6
19.56
21.2
19.36
18.77
21.2
20.1
20.49
1.20
19
33.25
29.71
30.15
31.2
29.95
28.76
30.41
28.9
27.6
27
29.69
1.79
20
37.16
32.84
37.57
35.53
38.55
37.45
40.63
36.49
37.79
39.36
37.34
2.13
Work
Element
Time
1
Time
2
Time
3
Time
4
Time
5
Time
6
Time
7
Time
8
Time
9
Time 10
Avg. Time
Std
Dev
21
25.99
26.23
24.75
25.25
25.67
24.02
23.7
24.33
25.49
25.48
25.09
0.85
22
45.99
42.81
47.08
48.42
43.85
47.46
44.66
48.38
46.46
47.52
46.26
1.92
23
65
65
65
65
65
65
65
65
65
65
65.00
2.00
55.12
60.48
52.24
55.72
52.36
54.56
56.22
53.98
54.03
56.47
55.12
2.38
29.5
26.87
27.81
25.79
27.17
28.42
27
30.43
28.26
29.3
28.06
1.41
20
20
20
20
20
20
20
20
20
20
20.00
1.25
17.68
15.4
16.2
16.75
15.4
17
17.8
15.71
16.13
15.67
16.37
0.89
18.47
17.1
15.7
19.15
16.6
17.1
17.75
16.89
17.57
15.96
17.23
1.06
29
31.5
34.69
34.36
34.25
29.13
34.15
35.69
34.9
34.8
33.41
33.69
1.95
30
30
30
30
30
30
30
30
30
30
30
30.00
1.50
31
8
8
8
8
8
8
8
8
8
8
8.00
1.00
32
25.53
25.56
27.04
26.58
24.97
27.41
26.6
23.7
25.18
26.12
25.87
1.11
33
11.77
8.89
9.67
8.67
9.94
8.22
7.51
9.14
10.28
9.82
9.39
1.19
34
9.05
12.22
12.38
10.82
11.01
10.21
12.24
8.7
9.38
11.63
10.76
1.38
35
44.76
38.74
43.41
39.01
43.41
43.25
40.41
44.35
42.8
45.81
42.60
2.41
36
8.62
9
9.52
10.96
10.61
9.26
9.39
7.61
9.47
9.17
9.36
0.94
37
36.35
36.95
37.3
33.35
37.11
35.2
37.03
36.48
34.17
35.45
35.94
1.35
38
28.97
34.99
23.71
25.22
26.91
31.97
26.58
28.62
27.58
30.24
28.48
3.30
24
QTY
4
25
26
2
27
28
2
Indicates time has estimation
Total:
18.90
minutes
Each element is given a 5% personal allowance, a 3% delay allowance, and the
recommended International Labor Office (ILO) fatigue allowances. The fatigue
allowances differ with the level of difficulty of the task being performed or the type
of operation that is being performed.
Work
Element
Station
Average
Time
Personal
Allowance
Delay
Allowance
Fatigue
Allowance
Standard
Time
Std Dev with
Allowances
1
WS1
45.858
5%
3%
4%
51.36
2.64
2
S1
60
5%
3%
6%
68.40
2.28
3
WS3
42.588
5%
3%
4%
47.70
2.25
4
WS2
33.85
5%
3%
4%
37.91
2.17
5
WS2
11.598
5%
3%
4%
12.99
0.88
6
S4
26.533
5%
3%
4%
29.72
2.19
7
S4
18.804
5%
3%
4%
21.06
1.3
8
WS4
54.81
5%
3%
4%
61.39
2.99
9
S5
16
5%
3%
4%
17.92
1.12
10
S5
59.701
5%
3%
4%
66.87
3.62
11
S5
19.546
5%
3%
4%
21.89
1.04
12
WS6
52.948
5%
3%
4%
59.30
3.98
13
WS8
34.411
5%
3%
4%
38.54
3.13
14
WS2
10.578
5%
3%
4%
11.85
2.26
15
S2
20
5%
3%
4%
22.40
1.4
16
S2
8
5%
3%
4%
8.96
1.12
17
S2
24.295
5%
3%
4%
27.21
1.39
18
WS2
20.487
5%
3%
4%
22.95
1.35
19
WS3
29.693
5%
3%
4%
33.26
2.01
20
S3
37.337
5%
3%
6%
42.56
2.43
Work
Element
Station
Average
Time
Personal
Allowance
Delay
Allowance
Fatigue
Allowance
Standard
Time
Std Dev with
Allowances
20
S3
37.337
5%
3%
6%
42.56
2.43
21
WS1
25.091
5%
3%
4%
28.10
0.96
22
WS5
46.263
5%
3%
4%
51.81
2.15
23
WS7
65
5%
3%
4%
72.80
2.24
24
S6
55.118
5%
3%
6%
62.83
2.71
25
S6
20
5%
3%
4%
22.40
1.58
26
S8
16.374
5%
3%
6%
18.67
1.43
27
WS10
17.229
5%
3%
6%
19.64
1.02
28
WS10
28.055
5%
3%
6%
31.98
1.21
29
WS8
33.688
5%
3%
4%
37.73
2.19
30
WS9
30
5%
3%
4%
33.60
1.68
31
S7
8
5%
3%
4%
8.96
1.12
32
S7
25.869
5%
3%
4%
28.97
1.24
33
WS10
9.391
5%
3%
6%
10.71
1.36
34
WS11
10.764
5%
3%
6%
12.27
1.57
35
WS9
42.595
5%
3%
4%
47.71
2.7
36
WS10
9.361
5%
3%
6%
10.67
1.07
37
WS11
35.939
5%
3%
6%
40.97
1.54
38
WS11
28.479
5%
3%
6%
32.47
3.77
Total:
21.28
minutes
Assumptions
• The elements were timed in an environment that is not representative
of the true working environment. It is assumed that the data recorded
represents the true working environment.
• It is assumed that ten time trials will be sufficient to get an accurate
standard time.
• Some elements were simulated due to lack of equipment.
• All motors came with wires and bridge rectifiers already connected
• The design process for the Manufacturing Processes (MP) team has
not been completed. Elements 2 and 26 require machinery from the
MP design and have estimated times.
• Elements 9, 15, 16, 17 and 31 all involve gluing plastics. It is assumed
that the glue will harden on contact.
• Element 23 had to be estimated because the mechanical engineering
collaboration had not finished design changes to the Ultraquiet Foot
Spa.
• Elements 12, 21, and 24 have estimation because of the time saved by
using the screw presenter is unknown.
• A 4% basic fatigue allowance is given to all elements and 2% is added
for more difficult tasks and standing tasks.
Calculations for Line Balancing
•
•
•
•
•
•
•
•
•
•
•
•
•
The cycle time is the amount of time to produce each unit in order to meet production
requirements. The cycle time is used in line balancing to set the flow of production at each
assembly station. The cycle time calculated in this report is for the 3rd quarter of the 5th
year. The cycle time calculation is given in the equation below.
(Number of production seconds each quarter)
Cycle Time = -------------------------------------------------------------------------------(Production volume in year 5 quarter with highest production)
The assembly line will run from 7:00A.M. until 4:00P.M. with a 30 minute lunch break and
two 15 minute breaks. Assuming 50 working weeks per year, five working days per week,
and one eight-hour shift per day, the number of seconds per quarter is as follows:
Number of seconds = (3600 sec./hr.)(8 hr./day)(5 days/wk.)(50 wk./yr)(.25 yr/quarter)
Number of seconds = 1,800,000 sec/quarter
Assuming one production line and one shift, the cycle time is as follows:
Cycle Time = (1,800,000 sec./quarter)/( 125,643 units/quarter) = 14.326 sec./unit
The cycle time must be larger than the longest standard time, which was 72.8 seconds.
Since 14.326 sec./unit is the cycle time for one line and one shift, an increase by a factor of
6 is needed to meet the production requirements.
Number of Production periods = (72.8 seconds)/(14.326 sec./unit) = 5.0816
Rounding up 5.0816 will give 6 production periods.
Cycle Time for line balancing = (14.326 sec./unit)(6) = 85.98 sec./unit
Having three assembly lines for two shifts was the design chosen to make the Cycle Time
for line balancing cover our longest task of 72.8 seconds.
Defining Workstations
“Decision Science” software was used to assign
elements to different workstations to equalize work content
across those workstations. The program computes a
balanced line based on the cycle time of 85.98 sec./unit and
the order in which elements must be completed. This
software allows for flexibility, because changes to the design
could be made quickly and easily. The software has several
options for line balancing. The positional weight method is
well known for its accuracy in line balancing, and it was the
method of choice. A positional weight was assigned to each
element by adding the succeeding element’s standard times.
Then, the elements are sorted in descending order based on
positional weight. The elements are assigned to
workstations in an effort to minimize idle time at each
workstation. Idle time calculation is as follows:
• Idle time = (85.98sec./unit) – (cumulative workstation
time)
• Once the line has been balanced workers can be assigned
to the workstations. The workers were assigned based on
one worker per 85.98 seconds of tasks. There will be 17
workers per assembly line. Refer to handouts for number of
workers per workstation.
• The goal of assembly line balancing is to have the efficiency
of the line to be as high as possible. The design chosen is
based more on the flow of material than high assembly line
efficiency. Several elements could be done without directly
being on the assembly line. These elements were denoted
sub-assemblies and were not included in the assembly line
balancing. An alternative to this would be to balance the line
with all elements included. With all elements included in the
balancing, the efficiency was 92.79%, and the assembly line
will have fifteen workers. This data can also be found on
page 1 of the Handout.
Since the material handling requirements are very high, the benefits of
having a flow based assembly line will outweigh the lost efficiency and the
two extra workers per line. The efficiency and other relative statistics for
the recommended assembly line design can be found in the table below.
Cycle time
85.98
seconds
Time allocated (cycle time * # stations)
1461.66
seconds/cycle
Time needed (sum of task times)
1276.53
seconds/unit
Idle time (allocated-needed)
185.13
Efficiency (needed/allocated)
87.33
percent
Balance Delay (1-efficiency)
12.66
percent
17
workers
Number of Workers
seconds/cycle
The assembly line will have great flow while having an efficiency of
87.33%. This is below our goal of 90%, but the line will have quality
inspections at workstations 4, and 9. The quality inspections will be done by
the workers on those workstations and this will make up for the lost
efficiency and reduce the rework. Workstations 10 and 11 have no parts
being assembled and do not require quality inspections.
The precedence chart is a flow chart that illustrates which elements have to be
performed before other elements can follow.