When Should I use Simulation?

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When should I use simulation?
Choosing the right process improvement tool for your project.

Learn how an experienced engineer decides when simulation is the right tool for his projects,
and when it isn't.

With the evolution of process improvement software, it can be difficult to decide the right tool for the job. Using something too powerful and complex can be a lengthy and unnecessary process, but underestimating the depth of analysis required and choosing something too simplistic early in a project can result in repeated work later.

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When Should I use Simulation?

  1. 1. When should I use simulation? Prof. Brian Harrington
  2. 2. Agenda • • • • • Common Manufacturing issues Intro to different types of simulation Using maths to analyze a Queuing System Using Excel/Monte Carlo simulation Using Discrete Event Simulation to look at system design • Six Sigma simulations • A case study. SIMUL8 Corporation | SIMUL8.com | info@SIMUL8.com
  3. 3. Manufacturing Dilemma • Any product development process involves extensive prototyping; • Yet, costly manufacturing production systems are typically not prototyped SIMUL8 Corporation | SIMUL8.com | info@SIMUL8.com
  4. 4. Simulation in Manufacturing • System Design • Operational Procedures • Performance Evaluation SIMUL8 Corporation | SIMUL8.com | info@SIMUL8.com
  5. 5. System Design • • • • • • • Plant Layout Effects of introducing new equipment Location and sizing of inventory buffers Location of inspection stations Optimal number of carriers, pallets Resource planning Protective capacity planning Biggest Bang for the Dollar! Contains Operational Procedures & Performance Metrics. SIMUL8 Corporation | SIMUL8.com | info@SIMUL8.com
  6. 6. Operational Procedures • Production Scheduling - Choice of scheduling and dispatching rules • Control strategies for material handling equipment • Shift patterns and planned downtime • Impact of product variety and mix • Inventory Analysis • Preventative maintenance on equipment availability Continuous Improvement SIMUL8 Corporation | SIMUL8.com | info@SIMUL8.com
  7. 7. Performance Evaluation • Throughput Analysis (capacity of the system, identification of bottlenecks); Jobs per Hour • Time-in-System Analysis • Assessment of Work-in-process (WIP) levels • Setting performance measure standards; OEE If you can measure it, you can manage it! SIMUL8 Corporation | SIMUL8.com | info@SIMUL8.com
  8. 8. Agenda • • • • • Common Manufacturing issues Intro to different types of simulation Using maths to analyze a Queuing System Using Excel/Monte Carlo simulation Using Discrete Event Simulation to look at system design • Six Sigma simulations • A case study. SIMUL8 Corporation | SIMUL8.com | info@SIMUL8.com
  9. 9. Why Simulation? • • • • • Competition drives the following: Leaner production environment Shorter product development cycles Narrower profit margins Flexible Manufacturing (1 Facility, 1 Process, Multiple Models) SIMUL8 Corporation | SIMUL8.com | info@SIMUL8.com
  10. 10. Types of Simulation • Mathematical Modeling – e.g. Queuing Theory • Monte Carlo Simulation – e.g. Excel based models • Discrete Event Simulation – e.g. SIMUL8 SIMUL8 Corporation | SIMUL8.com | info@SIMUL8.com
  11. 11. Simulation Overview System Model Deterministic Stochastic Queuing Theory Static Dynamic Static Differential equations Monte Carlo Continuous Discrete Dynamic Continuous Discrete DES SIMUL8 Corporation | SIMUL8.com | info@SIMUL8.com
  12. 12. Agenda • • • • • Common Manufacturing issues Intro to different types of simulation Using maths to analyze a Queuing System Using Excel/Monte Carlo simulation Using Discrete Event Simulation to look at system design • Six Sigma simulations • A case study. SIMUL8 Corporation | SIMUL8.com | info@SIMUL8.com
  13. 13. A Queuing System Input Source Service Process Queue Arrival Process Service Mechanism Jockeying Queue Balking Reneging SIMUL8 Corporation | SIMUL8.com | info@SIMUL8.com Served Customers Queue Structure
  14. 14. Queuing Concepts Relationships for M/M/C 1 Po = C-1 S n=0 (l/m) n! n + (l/m) c! c cm ( ) cm - l c Lq = (l/m) (l m) Po (c – 1)! (cm – l) 2 l = mean arrival rate m= mean service rate C = number of parallel servers These are messy to calculate by hand, but are very easy with appropriate software or a table. SIMUL8 Corporation | SIMUL8.com | info@SIMUL8.com
  15. 15. Queuing Concepts A Comparison of Single Server Models 2 M/G/1 L = q M/D/1 L q = M/M/1 L = q l s 2 2 + (l/m) 2(1 - l/m) (l/m) 2 2(1 - l/m) 2 (l/m) (1 - l/m) SIMUL8 Corporation | SIMUL8.com | info@SIMUL8.com Note that M/D/1 is ½ of M/M/1
  16. 16. Limitations on Queuing Models • What if: – we don’t have one of these basic models? – we have a complex system that has segments of these basic models and has other segments that do not conform to these basic models? • Then – simulate! SIMUL8 Corporation | SIMUL8.com | info@SIMUL8.com
  17. 17. Excel Based Simulations • Uses Data Table functions • Each Row might be one iteration of a simulation • Each Col is a random variable generated in the simulation • RAND(), VLOOKUP(), COUNTIF(), NORMINV() • Calculation & Iteration • >>> Using VBA to bring in Probability functions SIMUL8 Corporation | SIMUL8.com | info@SIMUL8.com
  18. 18. Monte Carlo Simulation • Named after the gaming tables of Monte Carlo • Also referred to as a Static Simulation Model in that it is a representation of a system at a particular point in time • In contrast, a Dynamic Simulation is a representation of a system as it evolves over time • Might be accomplished using Excel and the Random() SIMUL8 Corporation | SIMUL8.com | info@SIMUL8.com
  19. 19. Monte Carlo Simulation A Simple Example Day RN Deman d Units Sold Units Units Sale Unsold Short s Rev Return s Rev Unit Good Profit Cost Will $ 1 10 16 16 2 0 4.80 0.16 2.70 0.00 2.26 2 22 16 16 2 0 4.80 0.16 2.70 0.00 2.26 3 24 17 17 1 0 5.10 0.08 2.70 0.00 2.48 4 42 17 17 1 0 5.10 0.08 2.70 0.00 2.48 5 37 17 17 1 0 5.10 0.08 2.70 0.00 2.48 6 77 18 18 0 0 5.40 0.00 2.70 0.00 2.70 7 99 20 18 0 2 5.40 0.00 2.70 0.14 2.56 8 96 20 18 0 2 5.40 0.00 2.70 0.14 2.56 9 89 19 18 0 1 5.40 0.00 2.70 0.07 2.63 10 85 19 18 0 1 5.40 0.00 2.70 0.07 2.63 Avg 2.50 Where do this numbers come from? SIMUL8 Corporation | SIMUL8.com | info@SIMUL8.com
  20. 20. Limitations & Disadvantages • Stochastic, but static! Usually the time evolution of a manufacturing system is significant! • Excel based models, soon start to use VBA, and become very complicated • Might require 1000’s of iterations; Data Tables become slow • Difficult to communicate results to management. SIMUL8 Corporation | SIMUL8.com | info@SIMUL8.com
  21. 21. Agenda • • • • • Common Manufacturing issues Intro to different types of simulation Using maths to analyze a Queuing System Using Excel/Monte Carlo simulation Using Discrete Event Simulation to look at system design • Six Sigma simulations • A case study. SIMUL8 Corporation | SIMUL8.com | info@SIMUL8.com
  22. 22. Benefits of using DES Simulation • Mathematical & Excel based models only go so far • Less difficult than mathematical methods • Adds lot of “realism” to the model. Easy to communicate to end users and decision makers • Time compression • Easy to “scale” the system and study the effects • User involvement results in a sense of “ownership” and facilitates implementation SIMUL8 Corporation | SIMUL8.com | info@SIMUL8.com
  23. 23. SIMUL8 Common Building Blocks The 8 Common Building Blocks: Start Point, Queue, Activity, Conveyor, Resource, and End Point. Then the Logical aspect Labels & Conditional Statements. SIMUL8 Corporation | SIMUL8.com | info@SIMUL8.com
  24. 24. 8 is all you Need 1. Work Item Types: Can represent parts, carriers, signals, phone calls, just about anything that requires a “Label Profile”. 2. Activities: Work Centers, machines, tasks, process steps, anything that requires a “Cycle Time”. 3. Storage Areas: Buffers, de-couplers, banks, magazines, anything that requires a finite space to occupy over time. 4. Conveyors: Moving parts from pt A to pt B; Number of parts & Speed of conveyor. SIMUL8 Corporation | SIMUL8.com | info@SIMUL8.com
  25. 25. …8 is all you Need… 5. Resources: Manpower, crews, forklifts, tugs; anything that require a certain resource to be present. 6. End Pt: Keep track of statistics and free memory! 7. Labels: The attributes of a Work Item. 8. Visual Logic: The ability to create conditional statements; variables, loops, commands & functions. SIMUL8 Corporation | SIMUL8.com | info@SIMUL8.com
  26. 26. Less is More using 6-Sigma DMAIC or DMADV steps: • Define, Measure, Analyze, Improve, Control • Define, Measure, Analyze, Design, Verify DES Steps: • Objective, Assumptions, Data Collection, Build Model, Verify, Validate, Experimentation, Results Very similar steps! SIMUL8 Corporation | SIMUL8.com | info@SIMUL8.com

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