Lean Six Sigma Lean Six Sigma

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  • 1. Lean Six SigmaBy R.R Sawhney Ph D Ph.D. Department of Industrial and Information Engineering University of Tennessee, Knoxville406 East Stadium Hall Knoxville, TN 37996 865 974 7653sawhney@utk.edu

2. CPI-Center for Productivity &InnovationsDr. Rupy Sawhney Dr. Xueping Li ChrisRobert Sirisha Yanzhen Sashi K. Joesph Gagan PaulBarbara Wright Keyser NukalaLiNaidu Stainback Rajpal CastoOwens Laigang YuerongWang Dengfeng JosephArun Naveed Ashutosh SongChen Jiao Yang Amalesh Balasundaram Ahmed Hengle ZeidKarthik El- El-AkkadSubburaman 3. Comparison of Lean and Six Sigma d What is Lean? What is Six Sigma? 4. THEN WHAT IS LEAN SIX SIGMA? 5. A LEAN SIX SIGMA PROBLEM 6. Effect of Variation on Flow 7. Simulation #1Push SystemFive workstations in a cell. The first workstation will never be starved. Every station on a line has the same level of variation. The average process time is the same for every machine center (10 time units). However, the individual process times are taken randomly from a normal distribution. Each machine on Line One has a coefficient of variation of 5% and each machine on Line Two has a coefficient of variation of 50%. All other parameters besides variation are identical for both lines. lines Parts are pushed through the system meaning that when a machine is finished with a part it will immediately travel to the queue for the succeeding machine. 8. Effect of Variability -Push SystemLead Times for Push SystemProcessStandard Variability1 2 34 5 6 7 8 910 Average Deviation5% 88.988.194.3104.795.1 101.995.187.888.7 97.0 94.1 5.91 10% 165.6 155.3 99.4120.3 122.6 138.9114.6 102.8 140.4208.4136.8 33.05 20% 186.7 168.3 149.4 184.6 236.2 235.0204.4 226.5 174.5237.4200.3 32.11 30% 242.4 254.1 394.3 257.9 308.6 358.6213.6 373.8 299.5235.6293.8 63.48 40% 359.8 521.8 382.7 360.4 212.3 419.2335.6 671.8 452.0422.3413.8 121.67 50% 464.9 431.2 366.2 381.9 568.8 525.4490.5 242.8 277.2486.9423.6 105.86AVERAGE LEAD TIMES PER COEFFICIENT OF VARIATION Co-efficient of variation 50%40%30%o 20% Series1 10%5%0 100 200 300400 500Flow Times (seconds) *Note: These values represent the average results of simulations replicated ten times for a given level of variation 9. Effect of Variability -Push System Average Throughput for Push SystemProcessStandard Variability1 234 567 8 910AverageDev5% 358.8 359359.1358.6358.4 359358.9 358.9 358.9 358.4358.8 0.25 10% 357.9 357.9357.8357.4357.6 358357.1 357.9 357.5 355.9357.5 0.63 20% 356.8 354.9354.7353.7353.2355.8 354.7 354.5 356.1 354.7354.9 1.08 30% 352.6 354.7352.6 352 353.7354.1 353.2 351.5 353.3 351.6352.9 1.07 40% 350.8 351348.7347.6345.2350.8 352.1 349.2 347.5 349.9349.3 2.08 50% 347.4 345.3349354.2344.4 348348.3 346.8 348345 346.7 1.65AVERAGE THROUGHPUT PER COEFFICIENT OF VARIATION50.0%oefficient of Variation40.0% 30.0% 20.0%Series1 10.0% C5.0% 340 345350 355 360Average Throughput(pieces/hours) *Note: These values represent the average results of simulations replicated ten times for a given level of variation 10. Effect of Variability -Push System Average Overall WIPProcess Standard Variability12 345 67 8 910 Average Deviation5% 8.9 8.89.410.59.410.2 9.58.88.9 9.79.4 0.59 10% 16.515.5 9.912.012.2 13.911.410.2 14.020.8 13.63.31 20% 18.5 18 5 16.716 714.814 8 18.3 18 323.5 23 5 23.523 520.520 522.622 6 17.4 17 423.5 23 5 19.919 93.213 21 30% 23.825.1 39.5 25.530.8 35.721.337.2 29.923.5 29.26.41 40% 35.651.5 37.8 35.620.5 42.433.167.7 44.841.9 41.1 12.44 50% 45.442.1 35.8 37.256.1 52.548.223.6 26.847.7 41.5 10.63AVERAGE OVERALL WIP PER COEFFICIENT OF VARIATION 50% oefficient of variation 40% v 30%20%Series110%C 5% 0.05.0 10.0 15.0 20.0 25.030.0 35.0 40.045.0Flow Times (seconds)*Note: These values represent the average results of simulations replicated ten times for a given level of variation 11. Simulation #2Pull System-Kanban Pull System KanbanFive workstations in a cell.cellThe first workstation will never be starved.Every station on a line has the same level of variation.The average process time is the same for every machine center (10 time units). However, the individual process times are taken randomly from a normal distribution.Each machine on Line One has a coefficient of variation of 5% and each machine on Line Two has a coefficient of variation of 50%.All other parameters besides variation are identical for both lines.th t b idi ti id ti l f b th li 12. Pull System- Kanban Pull System A WIP level of one unit is allowed between each station.WS1WS2 WS3The logic used to model this system is that a machine will work only when there is zero or one WIP between itself and the succeeding station. station If the queue between stations is equal to 2 the machine will not work. 13. Effect of Variability -Kanban Pull SystemLead Times For Kanban PullSystem Process StandardVariability1234 5678 9 10Average Deviation5% 71.2 68.9 70.8 66.871.8 67.9 68.3 66.471.4 71.969.52.1210% 70.7 68.7 71.1 70.573.2 71.1 69.6 72.772.0 72.471.21.4120% 72.3 71.2 73.6 73.673.3 73.7 72.6 73.573.6 73.573.10.8030% 75.6 75.5 76.8 77.974.5 78.0 77.0 76.175.1 74.776.11.2440% 81.1 80.7 81.4 78.877.8 79.1 79.6 78.778.7 78.979.51.1950% 81.3 82.3 82.3 83.779.2 82.4 84.8 81.183.8 82.382.31.57AVERAGE FLOW TIMES PER COEFFICIENT OF VARIATION50%C o -e ffi c i e n t o f v a r i a ti o n40% 30% 20% Series1 10% 5% 0 100200300400 500*Note: These values represent the average results of simulations replicated ten times for a givenFlow Times (seconds) level of variation 14. Effect of Variability -Kanban Pull System Throughput For Kanban Pull SystemProcess StdVariatio D n1 2 345 67 8 910 Average ev5% 356.2 356.9356.8357356.6 357 357356.5357.1356.8356.80.28 10% 351.8 352.6352.2353.4352.8 352.8 352.6353.1353.1353.4352.80.52 20% 338.5 340.4339.7341.3339.4 340.7 339338.9340.4339.6339.80.89 30% 322.2 321.7321.8323.2324.6 320.9 324.2320.2325.6322.3322.71.7 40% 305.1 300.5304.3304.6309.2 304.4 305304307.4306.5305.12.3 50% 285.3 283.8289288.4295.5 288.5 285.5288.6283.8289.1287.73.45 AVERAGE FLOW TIMES PER COEFFICIENT OF VARIATION50%Coefficient of v ariation40% 30% 20%Series1 10% 5% 0510 15 20 2530 3540 45 Flow Times (seconds)*Note: These values represent the average results of simulations replicated ten times for a given level of variation 15. Effect of Variability -Kanban PullSystem Average Overall WIP for Kanbang Process StandardVariability 1 23 4567 8 9 10 Average Deviation 5% 7.0 6.87.0 6.6 7.1 6.7 6.86.67.17.16.9 0.2110% 6.9 6.77.0 6.9 7.2 7.0 6.87.17.17.17.0 0.1420% 6.8 6.76.9 7.0 6.9 7.0 6.86.97.06.96.9 0.0830% 6.8 6.86.9 7.0 6.7 7.0 6.96.86.86.76.8 0.1140% 6.9 6.76.9 6.7 6.7 6.7 6.76.66.76.76.7 0.0850% 6.4 6.56.6 6.7 6.5 6.6 6.76.56.66.66.6 0.10AVERAGE FLOW TIMES PER COEFFICIENT OF VARIATION 50%ariation 40%Coefficient of va 30%20% Series110%5%0.0 005.0 50 10.010 015.015 020.020 0 25.0 25 0 30.030 0 35.0 35 0 40.040 0 45.0 45 0 Flow Times (seconds) *Note: These values represent the average results of simulations replicated ten times for a given level of variation 16. Simulation #3 Pull System CONWIPSystem-The same assumptions apply for the conwip system as did the pull system except for the following: A WIP level of seven units are allowed within the cell. cell The logic used to model CONWIP is that no part was allowed to enter the system until a part exited the system. This established the CONstant WIP. Within the system, the cell operates in the same y p manner as a push system 17. Effect Of Variability- CONWIP SystemLead Time for CONWIP ProcessStandardVariability12 34 5 67 8910Average Deviation 5% 70.370.3 70.570.470.3 70.4 70.470.4 70.370.3 70.4 0.0710% 71.471.3 71.371.471.2 71.2 71.371.3 71.371.3 71.3 0.0620% 74.274 274.474 4 74.4 74 474.7 74 774.1 74 1 74.374 3 74.6 74 674.1 74 1 74.674 674.974 9 74.4 74 4 0.250 2530% 78.278.3 78.778.078.0 78.0 78.578.1 78.678.7 78.3 0.2940% 82.782.3 83.082.683.0 82.3 82.882.9 83.282.3 82.7 0.3350% 87.886.7 86.887.187.9 87.1 86.987.9 87.087.4 87.3 0.47 AVERAGE LEAD TIMES PER COEFFICIENT OF VARIATION50%oefficient of variation40% 30% 20%Series1 10% C5%0.0 100.0200.0300.0400.0 500.0 Flow Times (seconds) *Note: These values represent the average results of simulations replicated ten times for a given level of variation 18. Effect Of Variability- CONWIP SystemThroughput For CONWIP Pull SystemProcess1 2 34 5 67 89 10 Average Standard 5%358.4 358.5357.5357.7 358.4 358.1 358 357.8358.4 358.5358.10.3610%353 353.6353.4353.1 354.1 353.8 353.3 353.3353.6 353.6353.50.3120%339.5 339 5 338.8 338 8338.6338 6337.6 337 6 340.3 340 3 338.9 338 9 338 340.1 340 1337.8337 8 336.6336 6338.6 338 61.151 1530%322.2 321.7320.5323.1 323.3 323.2 321 322.5320.8 320.1321.81.1940%305 305.7303.6305.4 303.9 306.3 304.2 304.3303 306.5304.81.1950%287 290.7290.4289.6 287 289.1 290 286.5289.8 288.1288.81.57AVERAGE THROUGHPUT PER COEFFECIENT OF VARIATION0.50.4 0.3 0.2Ser i es1 0.10.05 0 50 100150200250300350 400A v e r a ge T hr oughput ( pi e c e s / hour ) 19. Effect Of Variability- CONWIP System Overall Average WIP for CONWIP Process StandardVariability1 2 3 456789 10 Average Deviation 5%7.0 7.0 7.07.0 7.07.0 7.0 7.07.0 7.07.00.0010%7.0 7.0 7.07.0 7.07.0 7.0 7.07.0 7.07.00.0020%7.0 7.0 7.07.0 7.07.0 7.0 7.07.0 7.07.00.0030%7.0 7.0 7.07.0 7.07.0 7.0 7.07.0 7.07.00.0040%7.0 7.0 7.07.0 7.07.0 7.0 7.07.0 7.07.00.0050%7.0 7.0 7.07.0 7.0 7.0 7.0 7.0 7.0 7.07.00.00AVERAGE WIP PER COEFFICIENT OF VARIATION 50% Co-efficient of variation 40%30% f 20% Series110%5%0.05.0 10.0 15.020.0 25.0 30.0 35.0 40.0 45.0*Note: These values represent the average results of simulations replicated ten times for a givenFlow Times (seconds)level of variation 20. SummaryHigher levels of variation effect flow time, WIP, and throughput (capacity)Variation early in the push production system is more detrimental than variation late in the routing gVariation late in the kanban pull production system is more detrimental than variation early in the routingPull systems establish a