Download - dinamica fabril
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com1
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.com2
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
What data do we need to decide?
Is HAL lean?
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com3
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.com4
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.com5
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.com6
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.com7
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.com8
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, a = 0.• “Practical worst case,” a = 1.• “Worst possible case,” a = W0.
Note: we won’t use quantitatively,but point it out to recognize that lineswith same rb and T0 can behave verydifferently.
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com9
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.com10
The Penny Fab
Characteristics:• Four identical tools in series.• Each takes 2 hours per piece (penny).• No variability.• CONWIP job releases.
Parameters:
rb =
T0 =
W0 =
a =
0.5 pennies/hour
8 hours
0.5 8 = 4 pennies
0 (no variability, best case conditions)
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com11
The Penny FabThe Penny Fab
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com12
The Penny Fab (WIP=1)The Penny Fab (WIP=1)
Time = 0 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com13
The Penny Fab (WIP=1)The Penny Fab (WIP=1)
Time = 2 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com14
The Penny Fab (WIP=1)The Penny Fab (WIP=1)
Time = 4 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com15
The Penny Fab (WIP=1)The Penny Fab (WIP=1)
Time = 6 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com16
The Penny Fab (WIP=1)The Penny Fab (WIP=1)
Time = 8 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com17
The Penny Fab (WIP=1)The Penny Fab (WIP=1)
Time = 10 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com18
The Penny Fab (WIP=1)The Penny Fab (WIP=1)
Time = 12 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com19
The Penny Fab (WIP=1)The Penny Fab (WIP=1)
Time = 14 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com20
The Penny Fab (WIP=1)The Penny Fab (WIP=1)
Time = 16 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com21
Penny Fab Performance
WIP TH CT THCT 1 0.125 8 1 2 3 4 5 6
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com22
The Penny Fab (WIP=2)The Penny Fab (WIP=2)
Time = 0 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com23
The Penny Fab (WIP=2)The Penny Fab (WIP=2)
Time = 2 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com24
The Penny Fab (WIP=2)The Penny Fab (WIP=2)
Time = 4 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com25
The Penny Fab (WIP=2)The Penny Fab (WIP=2)
Time = 6 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com26
The Penny Fab (WIP=2)The Penny Fab (WIP=2)
Time = 8 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com27
The Penny Fab (WIP=2)The Penny Fab (WIP=2)
Time = 10 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com28
The Penny Fab (WIP=2)The Penny Fab (WIP=2)
Time = 12 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com29
The Penny Fab (WIP=2)The Penny Fab (WIP=2)
Time = 14 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com30
The Penny Fab (WIP=2)The Penny Fab (WIP=2)
Time = 16 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com31
The Penny Fab (WIP=2)The Penny Fab (WIP=2)
Time = 18 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com32
Penny Fab Performance
WIP TH CT THCT 1 0.125 8 1 2 0.250 8 2 3 4 5 6
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com33
The Penny Fab (WIP=4)The Penny Fab (WIP=4)
Time = 0 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com34
The Penny Fab (WIP=4)The Penny Fab (WIP=4)
Time = 2 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com35
The Penny Fab (WIP=4)The Penny Fab (WIP=4)
Time = 4 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com36
The Penny Fab (WIP=4)The Penny Fab (WIP=4)
Time = 6 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com37
The Penny Fab (WIP=4)The Penny Fab (WIP=4)
Time = 8 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com38
The Penny Fab (WIP=4)The Penny Fab (WIP=4)
Time = 10 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com39
The Penny Fab (WIP=4)The Penny Fab (WIP=4)
Time = 12 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com40
The Penny Fab (WIP=4)The Penny Fab (WIP=4)
Time = 14 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com41
Penny Fab Performance
WIP TH CT THCT 1 0.125 8 1 2 0.250 8 2 3 0.375 8 3 4 0.500 8 4 5 6
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com42
The Penny Fab (WIP=5)The Penny Fab (WIP=5)
Time = 0 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com43
The Penny Fab (WIP=5)The Penny Fab (WIP=5)
Time = 2 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com44
The Penny Fab (WIP=5)The Penny Fab (WIP=5)
Time = 4 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com45
The Penny Fab (WIP=5)The Penny Fab (WIP=5)
Time = 6 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com46
The Penny Fab (WIP=5)The Penny Fab (WIP=5)
Time = 8 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com47
The Penny Fab (WIP=5)The Penny Fab (WIP=5)
Time = 10 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com48
The Penny Fab (WIP=5)The Penny Fab (WIP=5)
Time = 12 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com49
Penny Fab Performance
WIP TH CT THCT 1 0.125 8 1 2 0.250 8 2 3 0.375 8 3 4 0.500 8 4 5 0.500 10 5 6 0.500 12 6
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com50
TH vs. WIP: Best Case
0
0.1
0.2
0.3
0.4
0.5
0.6
0 1 2 3 4 5 6 7 8 9 10 11 12
WIP
TH
rb
W0
1/T0
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com51
CT vs. WIP: Best Case
02468
101214161820222426
0 1 2 3 4 5 6 7 8 9 10 11 12
WIP
CT
T0
W0
1/rb
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com52
Best Case Performance
Best Case Law: The minimum cycle time (CTbest) for a given WIP level, w, is given by
The maximum throughput (THbest) for a given WIP level, w is given by,
otherwise.
if
,/
,CT 00
best
Ww
rw
T
b
otherwise.
if
,
,/TH 00
best
Ww
r
Tw
b
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com53
Best Case Performance (cont.)
Example: For Penny Fab, rb = 0.5 and T0 = 8, so W0 = 0.5 8 = 4,
which are exactly the curves we plotted.
otherwise.
4 if
,2
,8CTbest
w
w
otherwise.
4 if
,5.0
,8/THbest
ww
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com54
A Manufacturing Law
Little's Law: The fundamental relation between WIP, CT, and TH over the long-term is:
Insights:• Fundamental relationship• Simple units transformation• Definition of cycle time (CT = WIP/TH)
CTTHWIP
hrhr
partsparts
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com55
Penny Fab Two
10 hr
2 hr
5 hr 3 hr
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com56
Penny Fab Two
StationNumber
Number ofMachines
ProcessTime
StationRate
1 1 2 hr j/hr
2 2 5 hr j/hr
3 6 10 hr j/hr
4 2 3 hr j/hr
rb = ____________ T0 = ____________ W0 = ____________
0.5
0.4
0.6
0.67
0.4 p/hr 20 hr 8 pennies
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com57
Penny Fab Two Simulation (Time=0)
10 hr
2 hr
5 hr 3 hr
2
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com58
Penny Fab Two Simulation (Time=2)
10 hr
2 hr
5 hr 3 hr
4
7
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com59
Penny Fab Two Simulation (Time=4)
10 hr
2 hr
5 hr 3 hr
6
7
9
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com60
Penny Fab Two Simulation (Time=6)
10 hr
2 hr
5 hr 3 hr
8
7
9
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com61
Penny Fab Two Simulation (Time=7)
10 hr
2 hr
5 hr 3 hr
8
12
9
17
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com62
Penny Fab Two Simulation (Time=8)
10 hr
2 hr
5 hr 3 hr
10
12
9
17
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com63
Penny Fab Two Simulation (Time=9)
10 hr
2 hr
5 hr 3 hr
10
12
14
17
19
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com64
Penny Fab Two Simulation (Time=10)
10 hr
2 hr
5 hr 3 hr
12
12
14
17
19
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com65
Penny Fab Two Simulation (Time=12)
10 hr
2 hr
5 hr 3 hr
14
17
14
17
19
22
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com66
Penny Fab Two Simulation (Time=14)
10 hr
2 hr
5 hr 3 hr
16
17
19
17
19
22
24
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com67
Penny Fab Two Simulation (Time=16)
10 hr
2 hr
5 hr 3 hr
17
19
17
19
22
24
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com68
Penny Fab Two Simulation (Time=17)
10 hr
2 hr
5 hr 3 hr
22
19
27
19
22
24
20
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com69
Penny Fab Two Simulation (Time=19)
10 hr
2 hr
5 hr 3 hr
22
24
27
29
22
24
20
22
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com70
Penny Fab Two Simulation (Time=20)
10 hr
2 hr
5 hr 3 hr
22
24
27
29
22
24 22
22
Note: job will arrive atbottleneck just in timeto prevent starvation.
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com71
Penny Fab Two Simulation (Time=22)
10 hr
2 hr
5 hr 3 hr
27
24
27
29
32
24
2524
Note: job will arrive atbottleneck just in timeto prevent starvation.
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com72
Penny Fab Two Simulation (Time=24)
10 hr
2 hr
5 hr 3 hr
27
29
27
29
32
34
25
27
And so on….Bottleneck will just stay busy; all others will starve periodically
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com73
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 rb 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.com74
Worst Case Penny FabWorst Case Penny Fab
Time = 0 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com75
Worst Case Penny FabWorst Case Penny Fab
Time = 8 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com76
Worst Case Penny FabWorst Case Penny Fab
Time = 16 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com77
Worst Case Penny FabWorst Case Penny Fab
Time = 24 hours
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com78
Worst Case Penny FabWorst 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.com79
TH vs. WIP: Worst Case
0
0.1
0.2
0.3
0.4
0.5
0.6
0 1 2 3 4 5 6 7 8 9 10 11 12
WIP
TH
rb
W0
1/T0
Best Case
Worst Case
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com80
CT vs. WIP: Worst Case
048
121620242832
0 1 2 3 4 5 6 7 8 9 10 11 12
WIP
CT
T0
W0
Best Case
Worst Case
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com81
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.com82
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.com83
PWC Example – 3 jobs, 4 stations
State Vector State Vector1 (3,0,0,0) 11 (1,0,2,0) 2 (0,3,0,0) 12 (0,1,2,0) 3 (0,0,3,0) 13 (0,0,2,1) 4 (0,0,0,3) 14 (1,0,0,2) 5 (2,1,0,0) 15 (0,1,0,2) 6 (2,0,1,0) 16 (0,0,1,2) 7 (2,0,0,1) 17 (1,1,1,0) 8 (1,2,0,0) 18 (1,1,0,1) 9 (0,2,1,0) 19 (1,0,1,1) 10 (0,2,0,1) 20 (0,1,1,1)
clumped up states
spread out states
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.com84
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
From Little’s Law
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com85
Practical Worst Case Performance
Practical Worst Case Definition: The practical worst case (PWC) cycle time for a given WIP level, w, is given by,
The PWC throughput for a given WIP level, w, is given by,
where W0 is the critical WIP.
br
wT
1CT 0PWC
,1
TH0
PWC brwW
w
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com86
TH vs. WIP: Practical Worst Case
0
0.1
0.2
0.3
0.4
0.5
0.6
0 1 2 3 4 5 6 7 8 9 10 11 12
WIP
TH
rb
W0
1/T0
Best Case
Worst Case
PWCGood (lean)
Bad (fat)
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com87
CT vs. WIP: Practical Worst Case
048
121620242832
0 1 2 3 4 5 6 7 8 9 10 11 12
WIP
CT
T0
W0
Best Case
Worst Case PWC
Bad (fat)
Good(lean)
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com88
0
0.1
0.2
0.3
0.4
0.5
0 2 4 6 8 10 12 14 16 18 20 22 24 26
WIP
TH
Penny Fab Two Performance
Worst Case
Penny Fab 2
Best Case
Practical Worst Case
1/T0
rb
W0
Note: processtimes in PF2have var equalto PWC.
But… unlike PWC, it hasunbalancedline and multimachine stations.
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com89
Penny Fab Two Performance (cont.)
0
10
20
30
40
50
60
70
80
0 2 4 6 8 10 12 14 16 18 20 22 24 26
WIP
CT
Worst Case
Penny Fab 2
Best Case
Practical Worst C
ase
T0
1/rb
W0
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com90
Back to the HAL Case - Capacity Data
Process Rate (p/hr) Time (hr) Lamination 191.5 1.2 Machining 186.2 5.9 Internal Circuitize 150.5 6.9 Optical Test/Repair - Int 157.8 5.6 Lamination – Composites 191.5 1.2 External Circuitize 150.5 6.9 Optical Test/Repair - Ext 157.8 5.6 Drilling 185.9 10.0 Copper Plate 136.4 1.5 Procoat 146.2 2.2 Sizing 126.5 2.4 EOL Test 169.5 1.8 rb, T0 126.5 33.1
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com91
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.com92
HAL Case - Analysis
WIP Required for PWC to Achieve TH = 0.63rb?
354,2)1187,4(64.0
36.0)1(
64.0
36.0
36.01
0
0
Ww
rrWw
wTH bb
Much lower thanactual WIP!
Conclusion: actual system is much worse than PWC!
4.1055.1261187,4400,37
400,37
10
brWw
wTH
Much higherthan actual TH!
TH Resulting from PWC with WIP = 47,600?
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com93
HAL Internal Benchmarking Outcome
“Lean" Region
“Fat" Region
0.0
20.0
40.0
60.0
80.0
100.0
120.0
0 10,000 20,000 30,000 40,000 50,000
WIP
Th
rou
ghp
ut
(pan
els/
hou
r)
BestWorstPWC
CurrentTH = 45.8WIP = 37,000
© Wallace J. Hopp, Mark L. Spearman, 1996, 2000 http://www.factory-physics.com94
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.com95
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.com96
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