Workstation

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• Workstation

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• 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.

3
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
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5
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.

6
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.

7
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 QTY 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
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
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Work Element QTY 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
24 4 55.12 60.48 52.24 55.72 52.36 54.56 56.22 53.98 54.03 56.47 55.12 2.38
25   29.5 26.87 27.81 25.79 27.17 28.42 27 30.43 28.26 29.3 28.06 1.41
26 2 20 20 20 20 20 20 20 20 20 20 20.00 1.25
27   17.68 15.4 16.2 16.75 15.4 17 17.8 15.71 16.13 15.67 16.37 0.89
28 2 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

  Indicates time has estimation Indicates time has estimation Indicates time has estimation Indicates time has estimation Total 18.90 minutes
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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
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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
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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.

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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 700A.M. until
  400P.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.

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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
  elements 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)

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• 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.

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• 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 seconds/cycle
Efficiency (needed/allocated) 87.33 percent
Balance Delay (1-efficiency) 12.66 percent
Number of Workers 17 workers
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.
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The precedence chart is a flow chart that
illustrates which elements have to be performed
before other elements can follow.
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