Workstation

The assembly design is based on the demand for the peak quarter of year 5 Cycle Time = 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 ABC = (B/420,000)D = ($ annual exp. Y5) x ( C ) YearProduction QuantityProduction RatioAnnual Expenses $140, $22, $22, $22, $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 ElementQTY Time 1 Time 2 Time 3 Time 4 Time 5 Time 6 Time 7 Time 8 Time 9 Time 10Avg. Time Std Dev

Work ElementQTY Time 1 Time 2 Time 3 Time 4 Time 5 Time 6 Time 7 Time 8 Time 9Time 10Avg. Time Std Dev 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 ElementStation Average Time Personal Allowance Delay Allowance Fatigue Allowance Standard Time Std Dev with Allowances 1WS %3%4% S1605%3%6% WS %3%4% WS %3%4% WS %3%4% S %3%4% S %3%4% WS %3%4% S5165%3%4% S %3%4% S %3%4% WS %3%4% WS %3%4% WS %3%4% S2205%3%4% S285%3%4% S %3%4% WS %3%4% WS %3%4% S %3%6%

Work ElementStation Average Time Personal Allowance Delay Allowance Fatigue Allowance Standard Time Std Dev with Allowances 20S %3%6% WS %3%4% WS %3%4% WS7655%3%4% S %3%6% S6205%3%4% S %3%6% WS %3%6% WS %3%6% WS %3%4% WS9305%3%4% S785%3%4% S %3%4% WS %3%6% WS %3%6% WS %3%4% WS %3%6% WS %3%6% WS %3%6% 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) = sec./unit The cycle time must be larger than the longest standard time, which was 72.8 seconds. Since 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)/( sec./unit) = Rounding up will give 6 production periods. Cycle Time for line balancing = ( sec./unit)(6) = 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 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 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 time85.98seconds Time allocated (cycle time * # stations) seconds/cycle Time needed (sum of task times) seconds/unit Idle time (allocated-needed)185.13seconds/cycle Efficiency (needed/allocated)87.33percent Balance Delay (1-efficiency)12.66percent Number of Workers17workers 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.