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Planning and Scheduling in Manufacturing and Services

Planning and Scheduling in Manufacturing and Services. What is Scheduling About?. Applied operations research Models Algorithms Solution using computers Implement algorithms Draw on common databases Integration with other systems. Application Areas. Procurement and production

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Planning and Scheduling in Manufacturing and Services

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  1. Planning and Schedulingin Manufacturing and Services

  2. What is Scheduling About? • Applied operations research • Models • Algorithms • Solution using computers • Implement algorithms • Draw on common databases • Integration with other systems

  3. Application Areas • Procurement and production • Transportation and distribution • Information processing and communications

  4. Manufacturing Scheduling • Short product life-cycles • Quick-response manufacturing • Manufacture-to-order • More complex operations must be scheduled in shorter amount of time with less room for errors!

  5. Scope of Course • Levels of planning and scheduling • Long-range planning (several years), • middle-range planning (1-2 years), • short-range planning (few months), • scheduling (few weeks), and • reactive scheduling (now) • These functions are now often integrated

  6. Scheduling Systems • Enterprise Resource Planning (ERP) • Common for larger businesses • Materials Requirement Planning (MRP) • Very common for manufacturing companies • Advanced Planning and Scheduling (APS) • Most recent trend • Considered advanced feature of ERP

  7. Scheduling Problem • Allocate scarce resources to tasks • Combinatorial optimization problem Maximize profit Subject to constraints • Mathematical techniques and heuristics

  8. Our Approach Scheduling Problem Problem Formulation Model Solve with Computer Algorithms Conclusions

  9. Scheduling Models • Project scheduling • Job shop scheduling • Flexible assembly systems • Lot sizing and scheduling • Interval scheduling, reservation, timetabling • Workforce scheduling

  10. General Solution Techniques • Mathematical programming • Linear, non-linear, and integer programming • Enumerative methods • Branch-and-bound • Beam search • Local search • Simulated annealing/genetic algorithms/tabu search/neural networks.

  11. Scheduling System Design Order master file Shop floor data collection • Databases • Schedule generation • User interfaces Database Management Automatic Schedule Generator Performance Evaluation Schedule Editor Graphical Interface User

  12. LEKIN • Generic job shop scheduling system • User friendly windows environment • C++ object oriented design • Can add own routines

  13. Advanced Topics • Uncertainty, robustness, and reactive scheduling • Multiple objectives • Internet scheduling

  14. Topic 1 Setting up the Scheduling Problem

  15. Modeling • Three components to any model: • Decision variables • This is what we can change to affect the system, that is, the variables we can decide upon • Objective function • E.g, cost to be minimized, quality measure to be maximized • Constraints • Which values the decision variables can be set to

  16. Decision “Variables” • Three basic types of solutions: • A sequence: a permutation of the jobs • A schedule: allocation of the jobs in a more complicated setting of the environment • A scheduling policy: determines the next job given the current state of the system

  17. Model Characteristics • Multiple factors: • Number of machine and resources, • configuration and layout, • level of automation, etc. • Our terminology: Resource = machine (m) Entity requiring the resource = job (n)

  18. Notation • Static data: • Processing time (pij) • Release date (rj) • Due date (dj) • Weight (wj) • Dynamic data: • Completion time (Cij)

  19. Machine Configuration • Standard machine configurations: • Single machine models • Parallel machine models • Flow shop models • Job shop models • Real world always more complicated.

  20. Constraints • Precedence constraints • Routing constraints • Material-handling constraints • Storage/waiting constraints • Machine eligibility • Tooling/resource constraints • Personnel scheduling constraints

  21. Other Characteristics • Sequence dependent setup • Preemptions • preemptive resume • preemptive repeat • Make-to-stock versus make-to-order

  22. Objectives and Performance Measures • Throughput (TP) and makespan (Cmax) • Due date related objectives • Work-in-process (WIP), lead time (response time), finished inventory • Others

  23. Throughput and Makespan • Throughput • Defined by bottleneck machines • Makespan • Minimizing makespan tends to maximize throughput and balance load

  24. Due Date Related Objectives • Lateness • Minimize maximum lateness (Lmax) • Tardiness • Minimize the weighted tardiness

  25. Due Date Penalties Tardiness Lateness Late or Not In practice

  26. WIP and Lead Time • Work-in-Process (WIP) inventory cost • Minimizing WIP also minimizes average lead time (throughput time) • Minimizing lead time tends to minimize the average number of jobs in system • Equivalently, we can minimize sum of the completion times:

  27. Other Costs • Setup cost • Personnel cost • Robustness • Finished goods inventory cost

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