1. © J. Christopher Beck 20051 Lecture 28: Supply Chain Scheduling 2

2. © J. Christopher Beck 2005 2 Outline Discrete Manufacturing vs Continuous Manufacturing What Difference Does It Make? A Typical Framework for Supply Chain Optimization Medium Term Planning Short Term Scheduling Information System Issues

3. © J. Christopher Beck 2005 3 Supply Chain Scheduling

4. © J. Christopher Beck 2005 4 Discrete vs. Continuous Manufacturing Continuous (process) production Main inventory/products are finely divisible Steel, shampoo, paper Discrete production Main inventory/products are individually countable Cars, computers, consumer electronics Scheduling problems are different

5. © J. Christopher Beck 2005 5 Continuous: 1. Main Processing Raw materials are transformed to intermediate products Machines have high start-up/shutdown costs and High changeover costs Often fixed batch sizes Usually run 24/7

7. © J. Christopher Beck 2005 7 Continuous: 2. Finishing Products of main processes are “specialized” Cut, bent, extruded, painted, printed, … Often these are commodities Many clients Mix of make-to-stock, make-to-order Due dates, sequence dependent changeovers, and inventory management are important

8. © J. Christopher Beck 2005 8 Discrete: 1. Primary Conversion Like finishing in continuous Stamping, bending, cutting Process is generally pretty simple Output is often a part Car body part, computer case, … Schedule is often integrated with downstream processes

9. © J. Christopher Beck 2005 9 Discrete: 2. Main Production Many different operations of many tools 100 step process for semiconductors! Machines are very expensive Often organized like a job shop Each order has its own route, quantity, due date Sequence dependent changeovers

10. © J. Christopher Beck 2005 10 Discrete: 3. Assembly Put together parts Machines are cheap but material handling is important Assembly lines cars or consumer electronics Due dates, changeovers, sequencing, …

11. © J. Christopher Beck 2005 11 Table 8.1 SegmentProcessHorizonClock SpeedDifferentiation Continuous: Main PlanningLong-mediumLowVery low Continuous: Finishing Planning/ scheduling Medium-shortMedium/ High Medium/low Discrete: Conversion Planning/ scheduling Medium-shortMediumVery low Discrete: Main Planning/ scheduling Medium-shortMediumMedium/low Discrete: Assembly SchedulingShortHigh

12. © J. Christopher Beck 2005 12 Table 8.2 SegmentOptimization Problem Solution Technique Continuous: MainLot-sizing, cyclic scheduling MIP Continuous: Finishing Single machine, parallel machine Batch scheduling, inventory control, dispatch rules Discrete: ConversionSingle machine, parallel machine Batch scheduling, dispatch rules, CP Discrete: MainFlow shop, job shopIP, CP, shifting bottleneck, LS Discrete: AssemblyAssembly lineGrouping, spacing, sequencing techniques, CP, LS

13. © J. Christopher Beck 2005 13 Supply Chain Decomposition Medium- term planning Short- term sched- uling Stage 1Stage 2Stage 3Stage 4

14. © J. Christopher Beck 2005 14 Medium-term Aggregation Time abstraction 1 unit = 1 day or 1 week Product abstraction Work at product “family” level e.g., Tuborg beer, not 6-pack, 12, 24, keg, … Cost/job/capacity abstraction Average processing times Sequence dependencies ignored Factory treated as a single resource

15. © J. Christopher Beck 2005 15 Medium-term Planning Results Daily or weekly Demand for product families at each facility Inventory levels Transportation requirements No detailed scheduling has been done!

16. © J. Christopher Beck 2005 16 Medium-term Constrains Short-term Medium- term planning Short- term sched- uling Stage 1Stage 2Stage 3Stage 4

17. © J. Christopher Beck 2005 17 Medium-term Decouples Short-term Medium- term planning Short- term sched- uling Stage 1Stage 2Stage 3Stage 4

18. © J. Christopher Beck 2005 18 Short-term Scheduling Uses More Precise Data Time in minutes or seconds Horizon ≈ week, 2 weeks Jobs and resources are detailed Set-up time/cost are taken into account Products not just product families Demand for each product is represented

19. © J. Christopher Beck 2005 19 Problem Short term schedule solution may not exist! Why? May require feedback of information to the medium-term and a resolve Carlsberg takes 10-12 hours for a medium- term solve …

20. © J. Christopher Beck 2005 20 Feedback Mechanism Needed Medium- term planning Short- term sched- uling Stage 1Stage 2Stage 3Stage 4

21. © J. Christopher Beck 2005 21 Information Infrastructure Requirements Medium- term planning Short- term sched- uling Stage 1Stage 2Stage 3Stage 4