JIT and Lean Operations

1. JIT andLean Operations

2. JIT/Lean Production • Just-in-time (JIT):A highly coordinated processing system in which goods move through the system, and services are performed, just as they are needed, • JIT  lean production • JIT  pull (demand) system • JIT operates with very little “fat”

3. Goal of JIT The ultimate goal of JIT is a balanced system. Achieves a smooth, rapid flow of materials through the system

4. Ultimate Goal A balanced rapid flow Supporting Goals Eliminate disruptions Eliminate waste Make the system flexible Building Blocks Product Design Process Design Personnel Elements Manufactur-ing Planning Summary JIT Goals and Building Blocks Figure 14.1

5. JIT Building Blocks • Product design • Process design • Personnel/organizationalelements • Manufacturing planning and control

6. Product Design • Standard parts • Modular design • Highly capable production systems • Concurrentengineering

7. Process Design • Small lot sizes • Setup time reduction • Manufacturing cells • Limited work in process • Quality improvement • Production flexibility • Little inventory storage

8. Reduces inventory Less rework Less storage space Problems are more apparent Increases product flexibility Easier to balance operations Benefits of Small Lot Sizes

9. Personnel/Organizational Elements • Workers as assets • Cross-trained workers • Continuous improvement • Cost accounting • Leadership/project management

10. Manufacturing Planning and Control • Level loading • Pull systems • Visual systems • Close vendor relationships • Reduced transaction processing • Preventive maintenance

11. Pull/Push Systems • Pull system: System for moving work where a workstation pulls output from the preceding station as needed. (e.g. Kanban) • Push system: System for moving work where output is pushed to the next station as it is completed

12. Buyer Supplier Supplier Supplier Supplier Supplier Supplier Supplier Traditional Supplier Network Figure 14.4a

13. Tiered Supplier Network Buyer Supplier Supplier Supplier Supplier Supplier Supplier Supplier Figure 14.4b First Tier Supplier Second Tier Supplier Third Tier Supplier

14. Comparison of JIT and Traditional Table 14.3

15. Transitioning to a JIT System • Get top management commitment • Decide which parts need most effort • Obtain support of workers • Start by trying to reduce setup times • Gradually convert operations • Convert suppliers to JIT • Prepare for obstacles

16. Obstacles to Conversion • Management may not be committed • Workers/management may not be cooperative • Suppliers may resist • Why?

17. JIT in Services The basic goal of the demand flow technology in the service organization is to provide optimum response to the customer with the highest quality service and lowest possible cost. • Eliminate disruptions • Make system flexible • Reduce setup and lead times • Eliminate waste • Minimize WIP • Simplify the process

18. Benefits of JIT Systems • Reduced inventory levels • High quality • Flexibility • Reduced lead times • Increased productivity

19. Benefits of JIT Systems (cont’d) • Increased equipment utilization • Reduced scrap and rework • Reduced space requirements • Pressure for good vendor relationships • Reduced need for indirect labor

20. CHAPTER 15 Scheduling

21. Scheduling • Scheduling: Establishing the timing of the use of equipment, facilities and human activities in an organization • Effective scheduling can yield • Cost savings • Increases in productivity

22. WorkCenter #1 Work Center #2 Output High-Volume Systems • Flow system: High-volume system with Standardized equipment and activities • Flow-shop scheduling: Scheduling for high-volume flow system

23. Build A A Done Build B B Done Build C C Done Build D Ship JAN FEB MAR APR MAY JUN On time! Scheduling Manufacturing Operations High-volume Intermediate-volume Low-volume Service operations

24. High-Volume Success Factors • Process and product design • Preventive maintenance • Rapid repair when breakdown occurs • Optimal product mixes • Minimization of quality problems • Reliability and timing of supplies

25. Intermediate-Volume Systems • Outputs are between standardized high-volume systems and made-to-order job shops • Run size, timing, and sequence of jobs • Economic run size:

26. Scheduling Low-Volume Systems • Loading - assignment of jobs to process centers • Sequencing - determining the order in which jobs will be processed • Job-shop scheduling • Scheduling for low-volume systems with many variations in requirements

27. Gantt Load Chart Figure 15.2 • Gantt chart - used as a visual aid for loading and scheduling

28. Loading • Infinite loading • Finite loading • Vertical loading • Horizontal loading • Forward scheduling • Backward scheduling • Schedule chart

29. Sequencing • Sequencing: Determine the order in which jobs at a work center will be processed. • Workstation: An area where one person works, usually with special equipment, on a specialized job.

30. Everything is#1 Priority Sequencing • Priority rules: Simple heuristics used to select the order in which jobs will be processed. • Job time: Time needed for setup and processing of a job.

31. Top Priority Priority Rules Table 15.2 • FCFS - first come, first served • SPT - shortest processing time • EDD - earliest due date • CR - critical ratio • S/O - slack per operation • Rush - emergency

32. Rule AverageFlow Time(days) AverageTardiness(days) AverageNumber ofJobs at theWork Center FCFS 20.00 9.00 2.93 SPT 18.00 6.67 2.63 EDD 18.33 6.33 2.68 CR 22.17 9.67 3.24 Example 2 Table 15.4

33. Two Work Center Sequencing • Johnson’s Rule: technique for minimizing completion time for a group of jobs to be processed on two machines or at two work centers. • Minimizes total idle time • Several conditions must be satisfied

34. Johnson’s Rule Conditions • Job time must be known and constant • Job times must be independent of sequence • Jobs must follow same two-step sequence • Job priorities cannot be used • All units must be completed at the first work center before moving to second

35. Johnson’s Rule Optimum Sequence • List the jobs and their times at each work center • Select the job with the shortest time • Eliminate the job from further consideration • Repeat steps 2 and 3 until all jobs have been scheduled

36. Scheduling Difficulties • Variability in • Setup times • Processing times • Interruptions • Changes in the set of jobs • No method for identifying optimal schedule • Scheduling is not an exact science • Ongoing task for a manager

37. Minimizing Scheduling Difficulties • Set realistic due dates • Focus on bottleneck operations • Consider lot splitting of large jobs

38. Scheduling Service Operations • Appointment systems • Controls customer arrivals for service • Reservation systems • Estimates demand for service • Scheduling the workforce • Manages capacity for service • Scheduling multiple resources • Coordinates use of more than one resource

39. Cyclical Scheduling • Hospitals, police/fire departments, restaurants, supermarkets • Rotating schedules • Set a scheduling horizon • Identify the work pattern • Develop a basic employee schedule • Assign employees to the schedule

40. Service Operation Problems • Cannot store or inventory services • Customer service requests are random • Scheduling service involves • Customers • Workforce • Equipment

41. Service Scheduling SSU1 Overview—United Airlines

42. Service Scheduling SSU2 United Airlines Flight Schedule

43. Schedule PS8 Painting Example (Washburn Guitar)