1. The Waiting Time Formula
1.1. Waiting Time Formula for Multiple, Parallel Resources
1.1.1. U=FR/CAP
1.1.1.1. (1/a)/(m/p)=p/(a*m)
1.2. summary
1.3. CV = Std Dev / avg
1.4. Utilization = process time / ( interarrival time * number of servers)
1.4.1. U= p/(a*m)
2. Measurements
2.1. four dimensions
2.1.1. Productivity / costs
2.1.1.1. efficiency
2.1.2. variety
2.1.2.1. heterogeneity customer preferences
2.1.3. quality
2.1.3.1. product quality
2.1.3.1.1. how good
2.1.3.2. process quality
2.1.3.2.1. as good as promised
2.1.4. time
2.1.4.1. Responsiveness to demand
2.1.4.2. tradeoff
2.1.4.2.1. responsiveness vs. labor productivy
2.1.4.3. efficient forntier
2.1.4.3.1. line where industry has current froniter
2.2. performence measurements
2.2.1. cumulative inflow
2.2.2. cumulative outflow
2.2.3. cumulative flow
2.2.3.1. flow time ( horizontal)
2.2.3.2. Inventory (vertical)
2.2.3.3. example
2.2.4. flow unit (customer)
2.2.5. flowrate / throughput (Cust/h)
2.2.5.1. flow unit / time
2.2.6. flow time
2.2.6.1. time from beginning to end
2.2.7. inventory
2.2.7.1. number of flow unit at a given moment
2.2.8. processing time / Activity time
2.2.8.1. Time / flow Unit
2.2.9. capacity
2.2.9.1. 1/processing time
2.2.9.1.1. unit/sec
2.2.9.2. m = number of parallel workers
2.2.9.2.1. capacity = m/procesing time
2.2.10. bottle neck
2.2.10.1. process with lowest capacity
2.2.11. process capacity
2.2.11.1. capacity of bottleneck
2.2.11.1.1. Min(all capacities)
2.2.12. flow rate
2.2.12.1. Min ( demand rate, process capacity)
2.2.12.1.1. insufficient demand
2.2.13. utilization
2.2.13.1. Flow rate / capacity
2.2.14. process flow diagramm
2.2.14.1. triangle
2.2.14.1.1. waiting
2.2.14.2. box
2.2.14.2.1. processing time
2.2.14.3. multiple flow units
2.2.14.3.1. implied utilization
2.2.14.3.2. add up
2.2.14.3.3. generic flow unit ("Minute work")
2.2.14.3.4. process with attrition loss
2.2.15. cycle time
2.2.15.1. CT
2.2.15.2. 1/flow rate
2.2.15.3. direct labor content
2.2.15.3.1. sum all processing times
2.2.15.4. direct idle time
2.2.15.4.1. sum (all CT - p)
2.2.16. avg labor utilization
2.2.16.1. labor content / (labor content + direct idle time)
2.2.16.1.1. = eff. process time / total time paying
2.2.17. cost of direct labor = total wages per unit of time / flow rate per unit of time
2.2.18. example
2.2.19. Little's Law
2.2.19.1. Inventory (I)[Units] = Flow Rate (R) [Units/h] * Flow Time (T) [h]
2.2.19.2. Weakness: Averages
2.2.19.3. inventory turns
2.2.19.3.1. 1/T = COGS / Inventory
2.2.19.3.2. per unit inventory cost = Annual Inventory / Inventory turns (per year)
2.2.19.4. buffer or suffer
2.2.19.4.1. make to stock approach
2.2.19.4.2. make to order approach
2.2.20. Five reasons for inventory
2.2.20.1. pipeline inventory
2.2.20.1.1. you wil need some minimum inventory because of the flow time >0
2.2.20.2. seasonal inventory
2.2.20.2.1. driven by seasonal variation in demand and constant capacity
2.2.20.3. cycle inventory
2.2.20.3.1. economies of scale in production (purchasing drinks)
2.2.20.4. safety inventory
2.2.20.4.1. buffer against demand (Mc Donalds hamburgers)
2.2.20.5. decoupling inventory / buffers
2.2.20.5.1. buffers between several internal steps
2.2.20.6. where there is inventory there are supply / demand missmatches
3. definition
3.1. process management
3.1.1. doing things repeatedly
3.1.2. != project management
3.2. quartile analysis
3.2.1. compare top 25% with bottom 25% processing times
3.3. Flow Time Efficiency (or %VAT)
3.3.1. (Total value add time of a unit) / (Totla time a unit is in the process)
4. productivty
4.1. Units Output Produced / Input Used
4.1.1. example: 4 Units per labor hours (looks like processing time)
4.1.2. output: pruductive time
4.1.3. input: total time
4.2. Multifactor productivity
4.2.1. Output /(Capital$ + Labor$ + Materials$ + Services$ + Energy$)
4.3. kpi
4.3.1. key performance indicator
4.3.2. kpi tree
4.3.2.1. PROFIT
4.3.2.1.1. minus
4.3.3. break even point
4.4. Labor Productivity
4.4.1. Revenue / Labor Costs
5. waste
5.1. 7 sources of waste
5.1.1. overproduction
5.1.1.1. match supply with demand
5.1.2. transportation
5.1.2.1. relocate processes, then introduce standard sequences for transportation
5.1.3. rework
5.1.3.1. repetion or correction
5.1.3.2. analyse and solve root causes of rework -> more quality in module
5.1.4. over processing
5.1.4.1. provide clear, customer-driven standards for every process
5.1.5. motion
5.1.5.1. arrange people and parts around stations with work content that has been standardized to minimize motion
5.1.6. inventory
5.1.6.1. improve production control system and commit to reduce unnecessary "comport stocks"
5.1.7. waiting
5.1.7.1. understand the drivers of waiting
5.1.8. intellect
5.1.8.1. intelligence of workers
6. overall equipment effectiveness (OEE)
6.1. Downtime Losses
6.1.1. Availability Rate
6.2. Speed Losses
6.2.1. Performance Rate
6.3. Quality Losses
6.3.1. Quality Rate
6.4. Overall people effectiveness
6.4.1. 100% total paid time
7. Takt Time
7.1. Time / #Units
7.1.1. sec/unit
7.2. determine
7.2.1. 1. Assign task so that total processing times < Takt time
7.2.2. 2. Make sure that all tasks are assigned
7.2.3. 3. Minimize the number of people needed (maximize labor utiilization)
8. Variety
8.1. Forms
8.1.1. Fit Based Variety
8.1.1.1. Horizontal Variety
8.1.1.2. distribution
8.1.1.3. examples
8.1.1.3.1. T-shirts, Shoes
8.1.1.3.2. Opening Hours
8.1.1.3.3. Departure Times for planes, trains
8.1.2. Perfomance Based Variety
8.1.2.1. Vertical
8.1.2.2. Customers differntiate on quality
8.1.2.3. distribution
8.1.2.4. examples
8.1.2.4.1. more features
8.1.2.4.2. better quality
8.1.3. Taste Based Variety
8.1.3.1. customers differ in their preferences or taste
8.1.3.2. distribution
8.1.3.3. examples
8.1.3.3.1. taste of food
8.1.3.3.2. art
8.1.3.3.3. colors
8.2. economic motives
8.2.1. performance based
8.2.1.1. Segment Market
8.2.2. Taste Based, Fit Based
8.2.2.1. Cater to heterogeneous customers
8.2.3. Variety seeking customers
8.2.3.1. example
8.2.3.1.1. food, lunch
8.2.4. avoid competition
8.2.4.1. varietion in a product can make it the lowest price, because none other is the same
9. Set Up
9.1. batch
9.1.1. number of units between setups
9.1.2. capacity given batch size= Batch Size / (Setup Time + Batch size*Time per Unit)
9.1.3. with large batches, processing time approaches 1/processing time, set up becomes more and more irrelevant
9.2. SMED
9.2.1. SIngle Minute Exchange of Die
9.2.1.1. 6 stage approach
9.2.2. every set up can be broken up into
9.2.2.1. internal
9.2.2.2. external
9.2.2.2.1. set up that can be done in parallel before machine is standing still
10. mixed Module Production
10.1. large badges leads to large inventories
10.2. Heijunka
10.3. calculate batch size
10.3.1. B/(S+B*p) = Demand or Capacity (Units/t)
10.3.1.1. B= Batch Size
10.3.1.2. S= Total Setup Time
10.3.1.3. p = Processing Time
11. Variability of Demand / pooling
11.1. statistics
11.1.1. mean
11.1.1.1. mü
11.1.2. standard deviation
11.1.2.1. sigma
11.1.2.1.1. s
11.1.3. Coefficient of Variation
11.1.3.1. CV=mü/s
11.1.3.1.1. doubling size leads to 2^(1/2) CV
11.1.4. positive correletion
11.1.4.1. when two things are positively correlated, it means two things: 1) a change in one of the two things directly leads to a change in the other thing. 2) both changes are similar in sign. take for example, temperature and ice melt. these two are positively correlated in that when temperature goes up, ice melt goes up. If temperature goes down, ice melt goes down.
11.1.5. random arrival times
11.1.5.1. a= average inter arrival time
11.1.5.2. CV = Coefficent of Variation
11.1.5.3. CVa = St-Dev ( inter arrival times)/(Avg(inter arrival times)
11.1.5.4. Poisson ditribution
11.1.5.4.1. CVa = 1
11.1.5.4.2. Constant hazard times (no memory)
11.1.5.4.3. Exponential inter arrivals
11.1.5.4.4. Exponential inter-arrivals
11.2. pooling
11.3. fragment
11.4. Delayed Differntiation
11.4.1. Modular Production
11.5. overwhelming of choice
11.6. priority rules
11.6.1. FCFS
11.6.1.1. = FIFO
11.6.1.2. easy to implement
11.6.1.3. fairness
11.6.1.4. lowest variance of waiting time
11.7. sequence based on importance
11.7.1. shortest Processing Time Rule (SPT)
11.7.1.1. minimize average wiating time
11.7.1.2. Hard to hav true processing time
11.8. appointments
11.8.1. problem
11.8.1.1. no shows
11.8.1.2. solves wrong problem: shifts queue
11.9. waiting Problems, loss problems
11.9.1. Customers leaving while waiting.
11.9.2. due to limited buffers
11.9.3. impatient customers
11.9.4. Loss analyzation
11.9.4.1. Percentage of Lost Customers
11.9.4.1.1. r=p/a (p=processing time, a=interarrival time)
11.10. Implied Utilization with Loss
11.10.1. 1. Calculate Demand D
11.10.1.1. begin from the end of process
11.10.2. 2. IU = effective Demand at step / Capacity
12. Flexibilty
12.1. No Flexibility / Full Flexibility / Partial Flexibility
12.1.1. Partial Flexibility get almost all benefits of Full felxibilty with lower costs
13. Process Mapping
13.1. Yves Pigneur
13.1.1. Customer Actions
13.1.2. Onstage Actions
13.1.3. Backstage Actions
13.2. Value Stream Mapping
13.3. improvements
14. Quality
14.1. yield
14.1.1. percentage according to specification
14.1.2. 1 - defect probabilty
14.2. Swiss Cheese Model
14.2.1. Redundency
14.2.2. ALL things have to go wrong
14.3. Defects
14.3.1. Scrap
14.3.2. Rework
14.3.3. Cost of Defects
14.3.3.1. CATCH defects BEFORE bottleneck
14.3.3.1.1. costs before bottleneck: costs of goods used
14.3.3.1.2. costs after bottleneck: opportunity costs, full price charged!
14.3.4. Buffer or Suffer
14.3.4.1. Starved vs. Blocked
14.3.4.1.1. Starve = nothing recieved from up stream
14.3.4.1.2. Blocked = no place to put downstream
14.3.4.2. Buffers can reduce variability in Quality (prevent starving or blocking)
14.3.4.3. Toyota: Inventory prevents quality problems from being reocognized
14.3.4.3.1. expose rocks!
15. Implementations
15.1. Six Sigma
15.1.1. ppm
15.1.1.1. Parts Per Million
15.1.1.1.1. Defects Per Million Parts
15.1.2. Variation
15.1.2.1. assignable cause
15.1.2.1.1. Statistical Process Control
15.1.2.2. common cause
15.1.3. Process Capability / Capability Score
15.1.3.1. Cp = (USL - LSL)/6*std
15.1.3.1.1. USL = Upper Specification Limit
15.1.3.1.2. LSL = Lower Specification Limit
15.1.3.2. NORMDIST in excel
15.1.4. Manage Quality
15.2. The Three Enemies of Operatons
15.3. Toyota Production System
15.3.1. Inventory leads to longer "Inventory turnaround time" / feedback loops
15.3.2. Jidoka
15.3.2.1. Detect / Alert / Stop
15.3.2.2. Andon Cord
15.3.3. Manage Quality
15.3.4. Kaizen
15.3.4.1. Root Cause Analysis
15.3.4.1.1. Ishikawa Diagram
15.3.4.1.2. 5 Whys
15.3.4.1.3. Pareto Chart
15.3.4.2. interplay of reality and models, iterative problem solving
15.4. pull system / kanban
15.4.1. "buffers are as unlean as it can get"
16. authors
16.1. original mindmap
16.1.1. @davidbaer