JIT

1. ISQA 459 Mellie Pullman JIT

2. Just-In-Time (JIT)Defined • JIT can be defined as an integrated set of activities designed to achieve high-volume production using minimal inventories (raw materials, work in process, and finished goods). • JIT also involves the elimination of waste in production effort. • JIT also involves the timing of production resources (e.g., parts arrive at the next workstation “just in time”).

3. The Japanese Approach to Productivity • Elimination of waste • Efforts concentrated on shop floor • Respect for people • Quality improvement focus

4. Waste in Operations (1) Waste from overproduction (2) Waste of waiting time (3) Transportation waste (4) Inventory waste (5) Processing waste (6) Waste of motion (7) Waste from product defects

5. Vendor Fab Sub Vendor Fab Final Assembly Customers Sub Fab Vendor Fab Vendor JIT Demand-Pull Logic

6. Final Assembly Minimizing Waste: Focused Factory Networks Coordination System Integration

7. A A B B C C Traditional Conveyance Sporadic and Infrequent Deliveries from Individual Suppliers

8. A ABC B C Mixed-Load Delivery Regular and Frequent Deliveries from Many Suppliers

9. Minimizing Waste: Group Technology • Using Departmental Specialization for plant layout can cause a lot of unnecessary material movement. Saw Saw Saw Grinder Grinder Heat Treat Lathe Lathe Lathe Press Press Press

10. Minimizing Waste: Group Technology • Revising by using Group Technology Cells can reduce movement and improve product flow. Grinder 1 2 Lathe Press Saw Lathe Heat Treat Grinder Press Lathe A B Saw Lathe

11. Minimizing Waste: Uniform Plant Loading Suppose we operate a production plant that produces a single product. The schedule of production for this product could be accomplished using either of the two plant loading schedules below. Not uniform Jan. Units Feb. Units Mar. Units Total 1,200 3,500 4,300 9,000 or Uniform Jan. Units Feb. Units Mar. Units Total 3,000 3,000 3,000 9,000 How does the uniform loading help save labor costs?

12. Mixed Batch Example • Company produces three products with a mixed model assembly line. • Operates 16 hours per day for 250 days/yr. • Determine the mixed model MPS for a daily batch. • Determine minimum batch MPS and the mix schedule for a day.

13. Calculations For every unit of #3 (minimum batch), we need twice as many #2 and 4 times As many #1 so for minimum batch: Produce during each day produce #1,1,1,1,2,2,3 - repeated 20 times

14. Mixed Batch Example • Company produces four products with a mixed model assembly line. • Operates 8hours per day for 250 days/yr. • Determine the mixed model MPS for a daily and hourly batch . • Determine mix schedule for a day.

15. Management philosophy • “Pull” system though the plant WHAT IT IS • Attacks waste • Exposes problems and bottlenecks • Achieves streamlined production WHAT IT DOES • Employee participation • Industrial engineering/basics • Continuing improvement • Total quality control • Small lot sizes WHAT IT REQUIRES • Stable environment WHAT IT ASSUMES Minimizing Waste: Just-In-Time Production

16. Machine downtime Scrap Vendor Change delinquencies Work in orders process queues Engineering design Design (banks) redundancies backlogs Decision Paperwork Inspection backlogs backlog backlogs Minimizing Waste: Inventory Hides Problems Example: By identifying defective items from a vendor early in the production process the downstream work is saved. Example: By identifying defective work by employees upstream, the downstream work is saved.

17. Minimizing Waste: Kanban Production Control Systems Withdrawal kanban Storage Part A Storage Part A Machine Center Assembly Line Production kanban Material Flow Card (signal) Flow

18. Determining the Number of Kanbans Needed • Setting up a kanban system requires determining the number of kanbans (or containers) needed. • Each container represents the minimum production lot size. • An accurate estimate of the lead time required to produce a container is key to determining how many kanbans are required.

19. The Number of Kanban Card Sets k = Number of kanban card sets (a set is a card) d = Average number of units demanded over some time period L = lead time to replenish an order (same units of time as demand) S = Safety stock expressed as a percentage of demand during lead time C = Container size

20. Example of Kanban Card Determination: Problem Data • A switch assembly is assembled in batches of 4 units from an “upstream” assembly area and delivered in a special container to a “downstream” control-panel assembly operation. • The control-panel assembly area requires 5 switch assemblies per hour. • The switch assembly area can produce a container of switch assemblies in 2 hours. • Safety stock has been set at 10% of needed inventory.

21. Example of Kanban Card Determination: Calculations Always round up!

22. JIT Requirements: Design Flow Process • Link operations • Balance workstation capacities • Re-layout for flow • Emphasize preventive maintenance • Reduce lot sizes • Reduce setup/changeover time

23. JIT Requirements: Improve Product Design • Standard product configuration • Standardize and reduce number of parts • Process design with product design • Quality expectations

24. Respect for People • Level payrolls • Cooperative employee unions • Subcontractor networks • Inverted pyramid management style • Small group involvement activities

25. JIT Requirements: Total Quality Control • Worker responsibility • Measure SQC • Enforce compliance • Fail-safe (Poke-yoke) methods • Automatic inspection

26. POKE-YOKEs address Mistakes DEFECTS MISTAKES • Damaged parts • Missing parts • Reversed parts • Wrong parts • Wrong size or shape • Wrong chemical properties • Wrong physical properties • Wrong item shipped • Wrong label • Wrong package • Damaged finished product • Omitting a part • Omitting a process • Performing a process incorrectly • Performing a process on the wrong part • Performing a process in improper environmental conditions • Performing the wrong process • Setting up equipment incorrectly • Setting up a work piece incorrectly • Adjusting equipment incorrectly • Tooling set up incorrectly • Tooling adjusted incorrectly • Installing wrong part • Installing part incorrectly

27. JIT Requirements: Work with Vendors • Reduce lead times • Frequent deliveries • Project usage requirements • Quality expectations

28. JIT Requirements: Reduce Inventory More • Look for other areas where inventory hides • Stores • Transit • Carousels • Conveyors

29. MRP and JIT • MRP is a planning system that does not do detailed shop floor scheduling • MRP requires fixed lead times which might actually vary with batch size • JIT excels at rapidly moving small batches of material through the system

30. MRP Small Bucket Approach • MRP “buckets” are reduced to daily or hourly • The most common planning period (time bucket) for MRP systems is weekly • Planned receipts are used internally to sequence production • Inventory is moved through the plant on a JIT basis • Completed products are moved to finished goods inventory which reduces required quantities for subsequent planned orders • Back flushing based on the BOM is used to deduct inventory that was used in production

31. MRP Balanced Flow • Used in repetitive operations • MRP plans are executed using JIT techniques based on “pull” principles • Flows are carefully balanced with small lot sizes

32. MRP vs. The Supermarket • Items used by many products are held in a common area often called a supermarket • Items are withdrawn as needed • Inventory is maintained using JIT systems and procedures • Common items are not planned by the MRP system