Basic Factory Dynamics - Dokuz Eylül University

Basic Factory Dynamics - Dokuz Eylül University

Basic Factory Dynamics Physics should be explained as simply as possible, but no simpler. Albert Einstein Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 1 HAL Case Large Panel Line: produces unpopulated printed circuit boards Line runs 24 hr/day (but 19.5 hrs of productive time) Recent Performance: throughput = 1,400 panels per day (71.8 panels/hr)

WIP = 47,600 panels CT = 34 days (663 hr at 19.5 hr/day) customer service = 75% on-time delivery Is HAL lean? What data do we need to decide? Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 2 HAL - Large Panel Line Processes Lamination (Cores): press copper and prepreg into core blanks Machining: trim cores to size Internal Circuitize: etch circuitry into copper of cores Optical Test and Repair (Internal): scan panels optically for defects Lamination (Composites): press cores into multiple layer boards External Circuitize: etch circuitry into copper on outside of composites Optical Test and Repair (External): scan composites optically for defects Drilling: holes to provide connections between layers

Copper Plate: deposits copper in holes to establish connections Procoat: apply plastic coating to protect boards Sizing: cut panels into boards End of Line Test: final electrical test Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 3 HAL Case - Science? External Benchmarking but other plants may not be comparable Internal Benchmarking capacity data: what is utilization? but this ignores WIP effects Need relationships between WIP, TH, CT, service!

Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 4 Definitions Workstations: a collection of one or more identical machines. Parts: a component, sub-assembly, or an assembly that moves through the workstations. End Items: parts sold directly to customers; relationship to constituent parts defined in bill of material. Consumables: bits, chemicals, gasses, etc., used in process but do not become part of the product that is sold. Routing: sequence of workstations needed to make a part. Order: request from customer. Job: transfer quantity on the line. Wallace J. Hopp, Mark L. Spearman, 1996, 2000

http://www.factory-physics.com 5 Definitions (cont.) Throughput (TH): for a line, throughput is the average quantity of good (non-defective) parts produced per unit time. Work in Process (WIP): inventory between the start and endpoints of a product routing. Raw Material Inventory (RMI): material stocked at beginning of routing. Crib and Finished Goods Inventory (FGI): crib inventory is material held in a stockpoint at the end of a routing; FGI is material held in inventory prior to shipping to the customer. Cycle Time (CT): time between release of the job at the beginning of the routing until it reaches an inventory point at the end of the routing.

Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 6 Factory Physics Definition: A manufacturing system is a goal-oriented network of processes through which parts flow. Structure: Plant is made up of routings (lines), which in turn are made up of processes. Focus: Factory Physics is concerned with the network and flows at the routing (line) level. Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com

7 Parameters Descriptors of a Line: 1) Bottleneck Rate (rb): Rate (parts/unit time or jobs/unit time) of the process center having the highest long-term utilization. 2) Raw Process Time (T0): Sum of the long-term average process times of each station in the line. 3) Congestion Coefficient (): A unitless measure of congestion. Zero variability case, = 0. Practical worst case, = 1. Worst possible case, = W0. Wallace J. Hopp, Mark L. Spearman, 1996, 2000 Note: we wont use quantitatively, but point it out to recognize that lines

with same rb and T0 can behave very differently. http://www.factory-physics.com 8 Parameters (cont.) Relationship: Critical WIP (W0): WIP level in which a line having no congestion would achieve maximum throughput (i.e., rb) with minimum cycle time (i.e., T0). W0 = rb T0 Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 9

The Penny Fab Characteristics: Four identical tools in series. Each takes 2 hours per piece (penny). No variability. CONWIP job releases. Parameters: rb = 0.5 pennies/hour T0

= 8 hours W0 = 0.5 8 = 4 pennies = 0 (no variability, best case conditions) Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 10

The Penny Fab Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 11 The Penny Fab (WIP=1) Time = 0 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 12 The Penny Fab (WIP=1)

Time = 2 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 13 The Penny Fab (WIP=1) Time = 4 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 14 The Penny Fab (WIP=1) Time = 6 hours

Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 15 The Penny Fab (WIP=1) Time = 8 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 16 The Penny Fab (WIP=1) Time = 10 hours

Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 17 The Penny Fab (WIP=1) Time = 12 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 18 The Penny Fab (WIP=1) Time = 14 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000

http://www.factory-physics.com 19 The Penny Fab (WIP=1) Time = 16 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 20 Penny Fab Performance WIP 1 2 3

4 5 6 Wallace J. Hopp, Mark L. Spearman, 1996, 2000 TH 0.125 CT 8 http://www.factory-physics.com THCT 1 21 The Penny Fab (WIP=2) Time = 0 hours

Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 22 The Penny Fab (WIP=2) Time = 2 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 23 The Penny Fab (WIP=2) Time = 4 hours

Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 24 The Penny Fab (WIP=2) Time = 6 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 25 The Penny Fab (WIP=2) Time = 8 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000

http://www.factory-physics.com 26 The Penny Fab (WIP=2) Time = 10 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 27 The Penny Fab (WIP=2) Time = 12 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000

http://www.factory-physics.com 28 The Penny Fab (WIP=2) Time = 14 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 29 The Penny Fab (WIP=2) Time = 16 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com

30 The Penny Fab (WIP=2) Time = 18 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 31 Penny Fab Performance WIP 1 2 3 4 5

6 Wallace J. Hopp, Mark L. Spearman, 1996, 2000 TH 0.125 0.250 CT 8 8 http://www.factory-physics.com THCT 1 2 32 The Penny Fab (WIP=4)

Time = 0 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 33 The Penny Fab (WIP=4) Time = 2 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 34 The Penny Fab (WIP=4) Time = 4 hours

Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 35 The Penny Fab (WIP=4) Time = 6 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 36 The Penny Fab (WIP=4) Time = 8 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000

http://www.factory-physics.com 37 The Penny Fab (WIP=4) Time = 10 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 38 The Penny Fab (WIP=4) Time = 12 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000

http://www.factory-physics.com 39 The Penny Fab (WIP=4) Time = 14 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 40 Penny Fab Performance WIP 1 2 3 4

5 6 Wallace J. Hopp, Mark L. Spearman, 1996, 2000 TH 0.125 0.250 0.375 0.500 CT 8 8 8 8 http://www.factory-physics.com THCT 1 2

3 4 41 The Penny Fab (WIP=5) Time = 0 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 42 The Penny Fab (WIP=5) Time = 2 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000

http://www.factory-physics.com 43 The Penny Fab (WIP=5) Time = 4 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 44 The Penny Fab (WIP=5) Time = 6 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com

45 The Penny Fab (WIP=5) Time = 8 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 46 The Penny Fab (WIP=5) Time = 10 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com

47 The Penny Fab (WIP=5) Time = 12 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 48 Penny Fab Performance WIP 1 2 3 4 5 6

Wallace J. Hopp, Mark L. Spearman, 1996, 2000 TH 0.125 0.250 0.375 0.500 0.500 0.500 CT 8 8 8 8 10 12 http://www.factory-physics.com THCT

1 2 3 4 5 6 49 TH vs. WIP: Best Case 0.6 rb 0.5 TH 0.4 0.3 1/T0

0.2 0.1 0 0 Wallace J. Hopp, Mark L. Spearman, 1996, 2000 1 2 3 4 W0 5 6

7 8 9 10 11 12 WIP http://www.factory-physics.com 50 CT CT vs. WIP: Best Case T0 26 24

22 20 18 16 14 12 10 8 6 4 2 0 1/rb 0 1 2 3 4 5 6 7 8 9 10 11 12 W0 WIP Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com

51 Best Case Performance Best Case Law: The minimum cycle time (CTbest) for a given WIP level, w, is given by CTbest if w W0 T0 , w / rb , otherwise. The maximum throughput (THbest) for a given WIP level, w is given by, w / T0 , if w W0 TH best otherwise. rb ,

Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 52 Best Case Performance (cont.) Example: For Penny Fab, rb = 0.5 and T0 = 8, so W0 = 0.5 8 = 4, CTbest if w 4 8, 2w, otherwise. TH best w / 8, if w 4 0.5, otherwise.

which are exactly the curves we plotted. Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 53 A Manufacturing Law Little's Law: The fundamental relation between WIP, CT, and TH over the long-term is: WIP TH CT parts parts hr hr Insights: Fundamental relationship

Simple units transformation Definition of cycle time (CT = WIP/TH) Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 54 Penny Fab Two 2 hr 5 hr 3 hr 10 hr Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com

55 Penny Fab Two Station Number 1 Number of Machines 1 Process Time 2 hr Station Rate 0.5 j/hr 2

2 5 hr 3 6 10 hr 0.4 j/hr 0.6 j/hr 4 2 3 hr 0.67 j/hr

0.4 p/hr 20 hr 8 pennies rb = ____________ T0 = ____________ W0 = ____________ Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 56 Penny Fab Two Simulation (Time=0) 2 2 hr 5 hr 3 hr

10 hr Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 57 Penny Fab Two Simulation (Time=2) 7 4 2 hr 5 hr 3 hr 10 hr Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com

58 Penny Fab Two Simulation (Time=4) 7 6 9 2 hr 5 hr 3 hr 10 hr Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 59 Penny Fab Two Simulation (Time=6)

7 8 9 2 hr 5 hr 3 hr 10 hr Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 60 Penny Fab Two Simulation (Time=7) 17 12 8

9 2 hr 5 hr 3 hr 10 hr Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 61 Penny Fab Two Simulation (Time=8) 17 12 10 9 2 hr 5 hr

3 hr 10 hr Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 62 Penny Fab Two Simulation (Time=9) 17 19 12 10 14 2 hr 5 hr 3 hr 10 hr

Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 63 Penny Fab Two Simulation (Time=10) 17 19 12 12 14 2 hr 5 hr 3 hr 10 hr Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com

64 Penny Fab Two Simulation (Time=12) 17 19 17 22 14 14 2 hr 5 hr 3 hr 10 hr Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com

65 Penny Fab Two Simulation (Time=14) 17 19 17 22 19 24 16 2 hr 5 hr 3 hr 10 hr

Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 66 Penny Fab Two Simulation (Time=16) 17 19 17 22 19 24 2 hr 5 hr 3 hr

10 hr Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 67 Penny Fab Two Simulation (Time=17) 27 19 22 22 19 24 20

2 hr 5 hr 3 hr 10 hr Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 68 Penny Fab Two Simulation (Time=19) 27 29 22 22 20

24 24 22 2 hr 5 hr 3 hr 10 hr Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 69 Penny Fab Two Simulation (Time=20) 27

Note: job will arrive at bottleneck just in time to prevent starvation. 29 22 22 24 24 22 22 2 hr 5 hr 3 hr

10 hr Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 70 Penny Fab Two Simulation (Time=22) 27 29 27 32 24 24 25 24

2 hr 5 hr Note: job will arrive at bottleneck just in time to prevent starvation. Wallace J. Hopp, Mark L. Spearman, 1996, 2000 3 hr 10 hr http://www.factory-physics.com 71 Penny Fab Two Simulation (Time=24) 27 29 27 32

25 29 34 27 2 hr 5 hr 3 hr 10 hr Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com And so on. Bottleneck will just stay busy; all others

will starve periodically 72 Worst Case Observation: The Best Case yields the minimum cycle time and maximum throughput for each WIP level. Question: What conditions would cause the maximum cycle time and minimum throughput? Experiment: set average process times same as Best Case (so r b and T0 unchanged) follow a marked job through system imagine marked job experiences maximum queueing Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 73

Worst Case Penny Fab Time = 0 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 74 Worst Case Penny Fab Time = 8 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 75

Worst Case Penny Fab Time = 16 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 76 Worst Case Penny Fab Time = 24 hours Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 77 Worst Case Penny Fab

Time = 32 hours Note: CT = 32 hours = 4 8 = wT0 TH = 4/32 = 1/8 = 1/T0 Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 78 TH vs. WIP: Worst Case 0.6 rb Best Case

0.5 TH 0.4 0.3 0.2 1/T0 Worst Case 0.1 0 0 1 2 3

4 5 6 7 8 9 10 11 12 W0 WIP Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 79 CT

CT vs. WIP: Worst Case T0 Worst Case 32 28 24 20 16 12 8 4 0 Best Case 0 1 2 3 4 5 6 7 8 9 10 11 12

W0 WIP Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 80 Worst Case Performance Worst Case Law: The worst case cycle time for a given WIP level, w, is given by, CTworst = w T0 The worst case throughput for a given WIP level, w, is given by, THworst = 1 / T0 Randomness? None - perfectly predictable, but bad! Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com

81 Practical Worst Case Observation: There is a BIG GAP between the Best Case and Worst Case performance. Question: Can we find an intermediate case that: divides good and bad lines, and is computable? Experiment: consider a line with a given rb and T0 and: single machine stations balanced lines variability such that all WIP configurations (states) are equally likely Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 82

PWC Example 3 jobs, 4 stations clumped up states State 1 2 3 4 5 6 7 8 9 10 Vector (3,0,0,0) (0,3,0,0) (0,0,3,0)

(0,0,0,3) (2,1,0,0) (2,0,1,0) (2,0,0,1) (1,2,0,0) (0,2,1,0) (0,2,0,1) State 11 12 13 14 15 16 17 18 19 20 Vector (1,0,2,0)

(0,1,2,0) (0,0,2,1) (1,0,0,2) (0,1,0,2) (0,0,1,2) (1,1,1,0) (1,1,0,1) (1,0,1,1) (0,1,1,1) Note: average WIP at any station is 15/20 = 0.75, so jobs are spread evenly between stations. Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com spread out states 83 Practical Worst Case

Let w = jobs in system, N = no. stations in line, and t = process time at all stations: CT(single) = (1 + (w-1)/N) t CT(line) = N [1 + (w-1)/N] t = Nt + (w-1)t = T0 + (w-1)/rb TH = WIP/CT = [w/(w+W0-1)]rb Wallace J. Hopp, Mark L. Spearman, 1996, 2000 From Littles Law

http://www.factory-physics.com 84 Practical Worst Case Performance Practical Worst Case Definition: The practical worst case (PWC) cycle time for a given WIP level, w, is given by, CTPWC T0 w 1 rb The PWC throughput for a given WIP level, w, is given by, TH PWC w rb , W0 w 1 where W0 is the critical WIP.

Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 85 TH vs. WIP: Practical Worst Case 0.6 rb Best Case 0.5 TH 0.4 0.3 0.2

1/T0 PWC Good (lean) Worst Case Bad (fat) 0.1 0 0 1 2 3

4 5 6 7 8 9 10 11 12 W0 WIP Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 86 CT

CT vs. WIP: Practical Worst Case T0 Worst Case 32 28 24 20 16 12 8 4 0 PWC Bad (fat) Good (lean)

Best Case 0 1 2 3 4 5 6 7 8 9 10 11 12 W0 WIP Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 87 Penny Fab Two Performance 0.5 Note: process times in PF2 have var equal to PWC. Best Case

rb 0.4 F Penny ab 2 0.3 TH Ca W or s t l a c i t c Pra

0.2 But unlike PWC, it has unbalanced line and multi machine stations. se 0.1 1/T0 Worst Case 0 0

2 4 6 8 10 W0 Wallace J. Hopp, Mark L. Spearman, 1996, 2000 12 14 16 18

20 22 24 26 WIP http://www.factory-physics.com 88 Penny Fab Two Performance (cont.) 80 70 Worst Case 60

Wo l a c t ic a r P 50 CT 40 ase C t rs Fab y

n Pen 2 1/rb 30 T0 20 Best Case 10 0 0 2 Wallace J. Hopp, Mark L. Spearman, 1996, 2000 4

6 8 W0 10 12 14 16 WIP http://www.factory-physics.com 18 20

22 24 26 89 Back to the HAL Case - Capacity Data Process Lamination Machining Internal Circuitize Optical Test/Repair - Int Lamination Composites External Circuitize Optical Test/Repair - Ext Drilling Copper Plate Procoat Sizing

EOL Test rb, T0 Wallace J. Hopp, Mark L. Spearman, 1996, 2000 Rate (p/hr) 191.5 186.2 150.5 157.8 191.5 150.5 157.8 185.9 136.4 146.2 126.5 169.5 126.5 http://www.factory-physics.com

Time (hr) 1.2 5.9 6.9 5.6 1.2 6.9 5.6 10.0 1.5 2.2 2.4 1.8 33.1 90 HAL Case - Situation Critical WIP: W0 = rbT0 = 126.5 33.9 = 4,187 Actual Values:

CT = 34 days = 816 hours (at 24 hr/day) WIP = 37,000 panels TH = 45.8 panels/hour Conclusions: Throughput is 36% of capacity WIP is 15 times critical WIP CT is 24.6 times raw process time Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 91 HAL Case - Analysis TH Resulting from PWC with WIP = 47,600? w 37,400 TH

rb 126.5 105.4 w W0 1 37,400 4,187 1 Much higher than actual TH! WIP Required for PWC to Achieve TH = 0.63rb? w TH rb 0.36rb w W0 1 0.36 0.36 w (W0 1) (4,187 1) 2,354

0.64 0.64 Much lower than actual WIP! Conclusion: actual system is much worse than PWC! Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 92 Throughput (panels/hour) HAL Internal Benchmarking Outcome 120.0 Lean" Region 100.0

Current TH = 45.8 WIP = 37,000 80.0 60.0 Fat" Region 40.0 Best Worst PWC 20.0 0.0 0 10,000 20,000 30,000 40,000 50,000 WIP

Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 93 Labor Constrained Systems Motivation: performance of some systems are limited by labor or a combination of labor and equipment. Full Flexibility with Workers Tied to Jobs: WIP limited by number of workers (n) capacity of line is n/T0 Best case achieves capacity and has workers in zones ample capacity case also achieves full capacity with pick and run policy

Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 94 Labor Constrained Systems (cont.) Full Flexibility with Workers Not Tied to Jobs: TH depends on WIP levels THCW(n) TH(w) THCW(w) need policy to direct workers to jobs (focus on downstream is effective) Agile Workforce Systems bucket brigades

kanban with shared tasks worksharing with overlapping zones many others Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 95 Factory Dynamics Takeaways Performance Measures: throughput WIP cycle time service

Range of Cases: best case practical worst case worst case Diagnostics: simple assessment based on rb, T0, actual WIP,actual TH evaluate relative to practical worst case Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com 96

Recently Viewed Presentations

  • STEM CHANGE VERBS! - senorrudis.com

    STEM CHANGE VERBS! - senorrudis.com

    The 4 ways to stem change E-IE O-UE U-UE E-I But señor, how do we know which verbs stem change? Here is a list of the common stem-change verbs: Pensar Empezar Recomendar Comenzar Sentar Querer Almorzar Poder Acostar Jugar Perder...
  • Medication Administration in the Community Administrative Rule 116

    Medication Administration in the Community Administrative Rule 116

    Communication is very important and must go both ways. It is best if the Nurse-Trainer remains, as much as possible in the teaching ,expert and supervisory role. The likelihood of staff communicating with you if you have termination responsibility is...
  • Cotton, Slavery, and the Old South

    Cotton, Slavery, and the Old South

    Field workers used music to pass the time and later to communicate with one another. Religion. Expected to worship under the supervision of white ministers. Still slaves incorporated African traditions into Christianity. Often more emotional. The idea of a "promised...
  • Jean D'Ormesson

    Jean D'Ormesson

    » Dans le Figaro Magazine, 2 janvier 2015. En 2010, Jean d'Ormesson arrive en gare de Loches (France), à bord de l'authentique Orient-Express. «Si c'est un grand plaisir d'être reconnu par ses amis, c'est peut-être encore plus flatteur d'être reconnu...
  • Sexual tourism Muhamet Lama, Universiteti Biznesi- Gjakove, Republic

    Sexual tourism Muhamet Lama, Universiteti Biznesi- Gjakove, Republic

    Under Article 139 of the Criminal Code of Kosovo, the expression "trafficking in persons" meaning: "the recruitment, transportation, transfer, harboring or receipt of persons by means of threat or use of force or other forms of coercion, abduction, forgery, fraud...
  • The Direction of Automation for NATS Lisa Aldridge

    The Direction of Automation for NATS Lisa Aldridge

    NATS Safety Strategy. Lessons From iFACTS. Engage users early and throughout the design process. Train controllers how to apply the tools, not just how to use the tools. Validation in limited operational service, Monitor in service for adaptations to the...
  • Chapter 21: Great Depression Section 1: Cause of the great ...

    Chapter 21: Great Depression Section 1: Cause of the great ...

    Stock Market Crashes. Because stocks were being bought with credit, prices were inflated, many investors looked to make quick money and sell (Stock Speculation) Stocks began to slide in Sept of 1929, by Oct investors began to lose confidence they...
  • Instructor Materials Chapter X: Chapter Title

    Instructor Materials Chapter X: Chapter Title

    LCP is the PPP protocol used to establish, configure, test, and terminate the data link connection. LCP can optionally authenticate a peer using PAP or CHAP. A family of NCPs are used by the PPP protocol to simultaneously support multiple...