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Tài liệu Time management practice 3

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11/20/2016 Final Report Work and Time Study Team C members: Huỳnh Hoàng Duy - 12273 (Team Leader) Vũ Đức Nguyên – 12329 Hồ Thanh Tùng – 11258 Nguyễn Hồng Phước – 12519 Ngô Quốc Dũng - 11275 Team C WORK STATION 5 AND 6 Contents 1. Abstract................................................................................................................................................. 3 2. Introduction .......................................................................................................................................... 3 3. State of Art (Background) .................................................................................................................... 3 4. Method ................................................................................................................................................. 3 5. 4.1 Stopwatch time study (STS) ......................................................................................................... 3 4.2 Process Analysis ........................................................................................................................... 3 4.3 Performance rating ...................................................................................................................... 4 Time Measurement .............................................................................................................................. 4 5.1 Work station 5 – Soldering red wire section and green wire section to raw motors ................ 4 5.1.1 Summary of Work Station 5 ................................................................................................. 4 5.1.2 Operational sequences......................................................................................................... 6 5.1.3 The result .............................................................................................................................. 6 5.1.3.1 Evaluation of stopwatch time study ................................................................................ 6 5.1.3.2 The result analysis ............................................................................................................ 7 5.1.4 5.2 Discussion of Work Station 5 ............................................................................................... 7 Work station 6 – Soldering pre-assembled motors to mini circuit board. ................................. 8 5.2.1 Summary of Work station 6 ................................................................................................. 8 5.2.2 Operational sequences....................................................................................................... 10 5.2.3 The result ............................................................................................................................ 10 5.2.3.1 Evaluation of stopwatch time study .............................................................................. 10 5.2.3.2 The result analysis .......................................................................................................... 10 5.2.4 Discussion of Work Station 6 ............................................................................................. 11 5.2.4.1 Hypothesis ...................................................................................................................... 11 5.2.4.2 Implement ...................................................................................................................... 11 5.3 6. The Conclusion ........................................................................................................................... 12 Optimization ....................................................................................................................................... 12 6.1 The current process .................................................................................................................... 12 6.1.1 Description.......................................................................................................................... 12 6.1.2 Remark of the writers group .............................................................................................. 13 6.1.3 Time Analysis ...................................................................................................................... 14 6.2 The Solution of Team C .............................................................................................................. 14 6.2.1 New Floor Plan and Description ........................................................................................ 14 6.2.2 Description.......................................................................................................................... 15 6.2.3 Improvement Proposal ...................................................................................................... 15 1 6.2.4 7. Time Analysis ...................................................................................................................... 16 6.3 Time Comparison........................................................................................................................ 16 6.4 The Conclusion ........................................................................................................................... 17 References .......................................................................................................................................... 17 The Table of Figure Figure 1.The alternative sequences of Work station 5 ................................................................................. 6 Figure 2. The pie chart of illustrating the percentage of time share of activities at Work station 5 ............ 7 Figure 3. The alternative sequences of Work station 6 .............................................................................. 10 Figure 4. The pie chart of illustrating the percentage of time share of activities at Work station 6 .......... 11 Figure 5. The current whole process is showing the flow of work piece.................................................... 12 Figure 6. The bar chart illustrates the time share of current process ........................................................ 14 Figure 7. The new process had been recommended.................................................................................. 15 Figure 8. The bar chart illustrates all the time measurements after improvement ................................... 16 2 1. Abstract To apply ‘The Work and time course” in studying the current Fischer lock production line, that design the new production line with the best efficiency This report shows stuck-points in the old production line. Based on those, recommendations will be finding as below structure:  Time measurement  Process optimization  Evaluation and Summary 2. Introduction Based on the time study, Team C examined the real workflow of the workstation 5 (soldering two wires to motor), workstation 6 (soldering motor to board) and observed all other workstations. In the stations 5 and 6, we recorded 20 times for the main manipulation, waiting time and others interruption. The results were written down to find out the standard time for utilization. During the project, we discussed to establish a new layout of the whole process that may be able to balance the duty cycle and reduce the waiting time as lowest as possible. Hence, we could build the time measurement pages and suitable optimization for the available infrastructure, standard time and qualified factory employees. 3. State of Art (Background) Line balancing is the process of assigning tasks to workstations, so that workstations have approximately equal time requirements. We use line balancing to - Minimize idle time - Balance bottlenecks. 4. Method 4.1 Stopwatch time study (STS) This a work measurement technique for recording the times and rates of working and analyze the data so as to obtain the time necessary for carrying out a job at a defined level of performance. It is only valid for the elements of a specified job carried out underspecified conditions. The objective of stopwatch time study is to determine reliable time standards for all work, both direct and indirect, including allowances and recovery times. 4.2 Process Analysis 3 Process analysis is a form of technical writing and expository writing "designed to convey to the reader how a change takes place through a series of stages. 4.3 Performance rating Based on Westinghouse system, the performance rating (L) of operator had been rated by trackers from team C. Performance factors had defines as following: - Skill: Based on the processing word of operators on-site - Effort: Based on the state of practical work - Condition: Rated Good with level C - Consistency: Rated “Good” with level C. 5. Time Measurement 5.1 Work station 5 – Soldering red wire section and green wire section to raw motors This step is to solder the motors with red wire section to pole (+) and green wire section to pole (-) on original motors. And then, these pre-assembled motors would be moved to the work station 6 – Soldering to circuit board. 5.1.1 Summary of Work Station 5 Workstation 5 – Soldering red wire, green wire to original motors List of activities Type of activity Solder one head of red wire section to pole (+) and green Main Activity section to pole (-) Time consumption of activity 459.2 Clean head of solder Ancillary Activity 6.8 Move all soldered motors into storage box Ancillary Activity 248 Set up 100 motors onto holding tray Ancillary Activity 415.7 Repair the error one Additional Activity 17.9 Covering the local ventilation by carton sheet Waiting time (relaxing time) Interruption due to dysfunction Interruption due to personal allowances 13.5 66.7 Time share of activity 37.40% 0.55% 20.20% 33.86% 1.46% 1.10% 5.43% Total share of processing time 466 37.95% Total share of time spent for getting/searching parts 663.7 54.06% Total share of time spent for personal allowances 66.7 5.43% Total share of time spent for additional activities 17.9 1.46% Interruption due to dysfunction 13.5 1.10% 4 Solder C1 Ref. Zy quant. mz 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 /n L i ti t= L ## ti Zeitart /n 1950 L ti 95 110 90 90 100 110 90 95 105 90 85 100 85 105 100 95 110 105 95 95 20 23.7 15.9 25.2 25.8 22.3 17.4 25.2 22.7 20 26.3 31 21.4 30 20.7 21.6 22.9 19.4 20.2 23 24.5 459.2 97.50 22.39 tMH Soldering red wire section to pole (+) and green wire section to pole (-) Release the prepared motor 22.96 20 F Release last piece Set up 100 new motors onto holding tray Release last motor 1.3 1.5 1.7 1.1 L ti F 248 L ti F 415.7 tMN Move all soldered motors into housing box 1.2 tMN L ti F tMN Cleaning the solder at C1 Covering the local ventilation by carton sheet End of covering 17.9 L ti F tMS Release the fixed one L ti F tMZ Repair the error one 13.5 212.1 Wait L End of waiting time ti 66.7 F 1228 Ti: Actual individual element times. TMH: Time of Main activity F: The progress time. L: The performance rate tMP: Time of Interrupted activity due to personal reason tMP Nr. TMN: Time of Ancillary activity tMZ: Time of Additional activity tMS Time of Interruption due to dysfunction 5 5.1.2 Operational sequences Figure 1.The alternative sequences of Work station 5 Alternative sequences had been determined during the measurement. The assigned operator have often expressed as below: - Preparation of 100 motors by setting up onto holding tray to easily position the Anode and Cathode, that aimed to prevent the event of soldering wrongly the wire colors with the kind of pole on raw motors. The holding tray is available 100 slots to put 100 motors on one time - The assigned operator continue to solder in orderly with that red wire section to pole (+), green wire section to pole (-) - Cleaning the head of solder if necessary - Stored the pre-assembled motors to transport box by 20 pc per time. 5.1.3 The result 5.1.3.1 Evaluation of stopwatch time study Nr. Workstation 5 Name Soldering Red wire section to pole (+), Green wire section to pole (-) Process description - Start measurement point Touching red wire section End measurement point Releasing the solder from green wire section at pole (-) on motor Time per piece 22.39 s Amount of measurements done 20 Relative confidence 7.1% Min real value 20.80 Max real value 23.98 Activity done at workstation 5 Measured by team C1 Taking one red wire section, and then positioning to solder one head to pole (+) Next is that one head of green wire section had soldered to pole (-). 6 Comments The amount of measurements needed 42 5.1.3.2 The result analysis Input Specified confidence level Standard deviation of measurements Mean value of measurements Number of measurements Result Absolute confidence interval Relative confidence interval Amount of measurements needed 95% 3.753469 22.83 20 1.645 7.2054 42 The result of workstation 5 is illustrating that as following: - The needed time for this step is about 22.83s - The amount of measurements needed up to 42 for much more confidence because of been over 5%. 5.1.4 Discussion of Work Station 5 The total time spent for WT 5 mainly come from soldering (38%) and setting up (54%) manipulation. There are some improvements for this station raised as below: - The holding tray have been recommended to narrow down the amount of motors position from 100 to 70. Due to the fact that the female employees have hardly operated on the whole tray. Therefore, the assigned operators have often separated two parts as setting up on this pattern and soldering each one. In this case, the female employee on duty had divided 100 motors to 62 pc and 38 pc for each process. - The worker at WT 6 could support the setting activity for WT 5 to mitigate the work time of WT5. - The stuff and tools such as lead wire, wire tray should be fixed to easily reach and prevent risks. 2% 1% Total share of processing time 5% 38% Total share of time spent for getting/searching parts Total share of time spent for personal allowances 54% Total share of time spent for additional activities Other Figure 2. The pie chart of illustrating the percentage of time share of activities at Work station 5 7 5.2 Work station 6 – Soldering pre-assembled motors to mini circuit board. This step is to solder pre-assembled motors from WT5 to circuit boards. And then, these soldered motors would be moved to the next work station: 3 and 8 – Putting motors into the shafts. 5.2.1 Summary of Work station 6 Workstation 6 – Soldering pre-assembled motors to mini circuit board Activity Time share of activity Time share (%) of activity Get boards 14.63 3.20% Solder motor to board 286.32 62.66% Cleaning solder equipment 11.66 2.55% Go to toilet 99 21.67% Taking rest of operator due to hot condition 45.33 9.92% Total share of processing time 312.61 68.41% Total share of waiting time 0 0 Total share of time spent for getting/searching parts 14.63 3.20% Total share of time spent for personal allowances 144.33 31.59% Total share of time spent for additional activities 0 0 Total share of time spent for recovery Other Activities Get board Solder motor to board Cleaning solder equipment Available for task Yes Executing a Direct task Planned task fulfillment Yes Yes No Due to Due to cycle dysfunction - Type of activity Ancillary activity Yes Yes Yes Yes - - Main activity Yes Yes Yes No - - Ancillary activity Go to toilet Yes No No - - No Taking rest of operator due to hot condition Yes No No - - No Interruption due to personal reasons Interruption due to personal reasons 8 Zy Ref. quant. mz 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 L ti 1999 Solder motor to board 1 Release motor board t= L 100 ti Tim e Solder C2 & L ti 94 83 13.48 11.83 93 13.36 108 112 93 97 100 110 84 112 100 95 114 91 93 108 112 93 15.42 16.10 13.34 13.92 14.25 15.76 12.00 16.05 14.33 13.61 16.39 13.00 13.36 15.42 16.10 13.34 107 20 15.26 286.32 F 20 99.97 14.31 14.32 tMH Nr. 100 2 Release boards L 100 ti 14.63 100 1 14.63 14.63 14.63 F tMN Get board 1 402.39 Cleaning solder 3 equipment L ti 97.17 3.00 100.6 113.87 98.8 1 92.54 4 2.56 2.95 3.15 11.66 2.93 tMN 2.92 F 4 100 4 Go to toilet 100 L 100 1 ti 99.0 99.0 99.00 99.0 F tMP 1 445.32 L 188.89 50.3 7 ti 24.0 90.0 148.44 206.06 22.0 3 136 F 67.29 3 Ti : actual individual element times. tMH : time main activity F: the progress time. L: the performance rate tMP : time interrupted activity due to personal reason tMP Taking rest of operator due to hot 5 condition tMN : time ancillary activity t : normal time 9 5.2.2 Operational sequences Figure 3. The alternative sequences of Work station 6 5.2.3 The result 5.2.3.1 Evaluation of stopwatch time study No. 2 Name Soldering prepared motors to circuit board Process description First of all, about 25 circuit boards were put on worktable. Next to pick one board, then picking one prepared motor. - Soldering the head left of red wire section to pole (+) at board, then rounding motor 90 degrees. - Continuing to solder the head left of green wire section to pole (-) at board. Start measurement point Picking circuit board End measurement point Releasing the solder from green wire section at pole (-) on board Time per piece 14.32 Amount of measurements done 20 Relative confidence 4.3% Min real value 13.70 Max real value 14.94 Activity done at workstation 5 Measured by team C2 Comments Work Station 6 5.2.3.2 The result analysis The result of workstation 6 is illustrating that as following: Input Specified confidence level 95% Standard deviation of measurements 1.404 Mean value of measurements 14.32 Number of measurements 20 Result Absolute confidence interval 0.615 Relative confidence interval 4.298% Range of real mean value 13.70≤t≤14.94 10 Because the relative confidence interval is less than 5% (4.298%) so it does not need to increase the quantity of replication. 5.2.4 Discussion of Work Station 6 5.2.4.1 Hypothesis As the percentage of time share of activity, time spent for personal allowances accounted for 31.59%, meaning that it’s significant and affected the efficiency of work station 6 because operators took rest without permission of supervisor and arbitrarily stopped working due to hot condition although the room atmosphere is not too hot with the support of fans and air conditioner. The arm of hypothesis is how to reduce the time of interrupted activity and it was showed as below. The first interruption due to personal reason is the time of going to toilet. The hypothesis for this activity is that if the worker plan to go to the toilet as group, particularly the workers those who perform as 2 stations next together, the interrupted times could be reduced and change to recovery time. The second interruption due to personal reason is the time for taking rest due to hot condition although air conditioner is already installed, the company could limit it in 2 ways. Once, installing new fans and air conditioner to decrease the room temperature. Other, managing the workers more strictly by policies of company and supervising Total share of processing time 31% Total share of waiting time Total share of time spent for getting/searching parts 66% 3% 0% Total share of time spent for personal allowances Figure 4. The pie chart of illustrating the percentage of time share of activities at Work station 6 5.2.4.2 Implement Base on the overall observation in the company. Team C had recognized the loose management of the supervisor and almost activities lack the control. The recovery time also is unscheduled which is related to the spontaneous activity of workers so that making the schedule for recovery time and controlling strictly the personal activities is the top priority of the project if company want to improve the efficiency. Worker could go the toilet but they need to inform the supervisor, co-workers and follow the recovery 11 schedule. They cannot go without the permission. For example, they could go to the toilet at beginning and the ending of shift, in process, they need to inform the supervisor As the company aspect, investing to facility to improve the efficiency could be meaningful if the factor (time for interrupted activity) affects dramatically to production and slowdowns the speed of production, but if the efficiency is not much improved, the company has to consider this solution. Therefore, in case of room condition, company should not change or improve the facility to reduce the time of action interrupted due to hot atmosphere. Because it will cost the company’s budget and also time greatly instead of they can improve the management skills of supervisor and control workers more tightly to edge the complain of workers 5.3 The Conclusion The efficiency rate has chance to improve up to 90% for work station 5 and 6 in theory. The new approaches once applying in practical production line that would mitigate the current waiting time and increase the processing work time. 6. Optimization 6.1 The current process Figure 5. The current whole process is showing the flow of work piece. 6.1.1 Description The current process have started at WT 5. Dedicated worker have picked up a motor and soldered a red wire and a green wire section to the motor. 12 Then, WT 6 would be received the motor and soldered it to the board and sent all to WT 3. At WT 3, the motors would be put on a shaft. Beside, worker at WT 4 inserted nine buttons into housing. The workers at WT 3 and WT 4 have sent their shafts and housings to worker 2 to assembly. Then, WT 10 must test them and mark by laser machine. Worker 7 does the same job with worker 4 while worker 8 puts motor on shaft with help of equipment. Then, they have sent their work pieces to WT 9 to assembly before worker 10 tests them and mark by laser machine. WT 1 is a preassembly step The process finishes and all products will be taken out. The lead time is about 80 seconds. 6.1.2 Remark of the writers group The cycle time is the main time of WT 2, nearly 80s. This value is much more than main times of other WTs, it has makes a lot of waiting time in the process. Workstations located at illogical position. For example, work pieces from WT 6 must move to WT 3, which is not next to WT 6. Worker 4 also has to send her work pieces to worker 2. Worker 9 and worker 2 have the same mission, but worker 9 uses machine equipment, it takes her nearly 46 seconds to finish while manual skills of worker 2 take her 80 seconds. In addition, materials are storage beside workstation 6 instead of worker 5 while workstation 5 is the first step of this process. Images 1. The current process 13 6.1.3 Time Analysis 90 Manual Screwdriver 80 79.84 70 Same function, same quantity of tasks but differenct time use 60 Screwdriver m/c 50 40 30 20 10 0 5 6 1 3 8 2 9 4 7 10 Figure 6. The bar chart illustrates the time share of current process The lead time is 79.84s The waiting time is based on every steps and analyzed generally, as below: ∑ 𝐴𝑙𝑙 𝑙𝑖𝑛𝑒 𝑡𝑖𝑚𝑒 ∑ 𝑊𝑜𝑟𝑘 𝑡𝑖𝑚𝑒 = ∑ 𝑀𝑎𝑖𝑛 𝑙𝑖𝑛𝑒 𝑡𝑖𝑚𝑒 ∑ 𝑊𝑜𝑟𝑘 𝑡𝑖𝑚𝑒 35.06+51.2+55.04+32.32+46.89+34.42+42.35+43.67+49.27 789.4 = 390.22 789.4 = 35.06+51.2+55.04+32.32+46.89+34.42+42.35+43.67+49.27 552.58 = = 49.43% 390.22 552.58 = 70.62% 6.2 The Solution of Team C The writers group is of opinion that the key priorities for improvement of current process as following: - Using every current resources - “Simple is the best” - Applying outstanding approaches of time study subject. The approaches have been utilized such as Process analysis to rearrange the current layout; Stopwatch time study to evaluate all kinds of time consumed in the production line as a whole; … 6.2.1 New Floor Plan and Description 14 Figure 7. The new process had been recommended. 6.2.2 Description Starting point: Work station 5 (WT) Work station 5: The assigned operator on duty would take input material from storage shelf and do its function. Work station 6: Taking work piece from WT5, doing its tasks and supporting WT5 such as setting up motor onto holding tray by Anode, Cathode to save time. Work station 1: Doing its tasks, delivering the work piece from WT6 to WT3, 8. Work station 2, 3, 4 – 7, 8, 9: Assembly stage and put on the roller. (Note: Therein, the WTs are same function that WT 3 - 8, WT 2 - 9, WT 4 – 7) Work station 10: Getting the work pieces on the roller, checking buttons, returning error one to WT 2, 9; doing its task such as testing, operating laser marking machine. End point: Finished goods from WT 10 would be stored at dedicated temporarily box. All input materials have been temporarily stored on shelf, they come from Storage. 6.2.3 Improvement Proposal Swapped position between WT 5 and WT 6 because the starting point is at WT 5 and in order to easily get raw motors from temporarily house shelf on the above right corner. Invested new screwdriver machine to automatic operate at WT 2 to increase the performance efficiency. Standardized the time for WT3 and WT 8 to encourage their two assigned operators perform efficiently. 15 Reposition of WT 1 to center of the work area, and then allocate this employee getting one more function as delivery person to facilitate the flow material such as: - Bring output of WT 6 to WT 3, 8 - Support to return the error work pieces from WT 10 to WT 2, 9. Reposition of WT 10 next to WT 1 to get the output of WT 2, 9 for testing and operating the laser marking machine. Besides that, this employee would be assigned to take responsibility for “checking buttons”, instead of the station of 2 and 9 - Putting soldered motors into shaft must do it. Fixed all material boxes on the production line such as: Lead wire tape, electrical wire tray, circuit board tray at WT 5, 6 and so on. The reason is to easily find out work pieces and to prevent the event of falling, missing. 6.2.4 Time Analysis Using new screwdriver m/c 45 40.2 40 35 30 Checking buttons task from WT 2, 9 25 20 15 10 Support for 02 assembly lines 5 0 5 6 1 3 8 2 9 4 7 10 Figure 8. The bar chart illustrates all the time measurements after improvement The lead time is 40.2s The waiting time is based on every steps and analyzed generally, as below: ∑ 𝐴𝑙𝑙 𝑙𝑖𝑛𝑒 𝑡𝑖𝑚𝑒 ∑ 𝑊𝑜𝑟𝑘 𝑡𝑖𝑚𝑒 = ∑ 𝑀𝑎𝑖𝑛 𝑙𝑖𝑛𝑒 𝑡𝑖𝑚𝑒 ∑ 𝑊𝑜𝑟𝑘 𝑡𝑖𝑚𝑒 11.6+5.4+3.6+2.7+4+9.6 402 = 36.9 402 = 11.6+5.4+3.6+2.7+4+9.6 281.4 = = 9.1% 36.9 281.4 = 13.1% 6.3 Time Comparison 16 Unit Current process Offered process Lead time (s) 79.84 40.02 Waiting time (All process) (%) 49.43 9.1 Waiting time (Main process) (%) 70.62 13.1 The current process has low efficiency and logically arranging, that make a plenty of waiting times. The manual activities would take a long time and high risks of wrong. The lead time is downing about 39.82s The efficiency of time spent has increase up to 57.52% (main process), 40.33% (all process). 6.4 The Conclusion The new production process that may pose some advantages: - Mitigated approximately 50% of time per pieces from 79.84s reduced down to 40.2s. It means that the efficiency of working time raised to 100%. - Almost current resources have been used up such as equipment, labor, workplace, and facilities. - Not too much invested, just something as one screwdriver machine, separating the table and so on. - Easily training and adapted by factory employees. 7. References 1. Dr.-Ing. Marlene Helfert, 2016. Work and Time Study documents. Vietnamese German University. 2. GPEM 2016 Class, 2016. The result of Time Study. Vietnamese German University. 3. Dr. Allison W. Pearson, 2011. Principles of Management & Production. Mississippi State University. 4. Lecture 9. . [Nov. 19, 2016]. 17
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