JIT AND Lean Operations 14-1

Transcription

1 Chapter 15 JIT AND Lean Operations 14-1

2 Product Structure Tree = Shop floor layouts A B(4) C(2) D(2) E(1) D(3) F(2) MRP vs. JIT 14-2

3 JIT/Lean Production Just-in-time: Repetitive production system in which processing and movement of materials and goods occur just as they are needed, d usually in small batches JIT is a characteristic of lean production systems JIT operates with very little fat 14-3

4 JIT Goals A balanced system -- a smooth, rapid flow of materials Minimize inventory Reduce setup and lead times Eliminate disruptions Make system flexible Eliminate waste 14-4

5 14-5

6 Sources of Waste Waste of overproduction Waste of waiting time Transportation waste Inventorywaste Processing waste Waste of motion Waste from product defects 14-6

7 1. Product design JIT Building Blocks 2. Process design 3. Personnel/organizational elements 4. Manufacturing planning and control 14-7

8 Standard parts Modular design Quality 1. Product Design 14-8

9 2. Process Design Setup time reduction (will result in..) Small lot sizes Low work in process/inventory storage Increased production flexibility Easier to balance operation through frequent setups (Figure 15-1) 1) Manufacturing cells Preventive maintenance to reduce breakdown 14-9

10 Figure 14-2 A= units of product A B = units of product B C = units of product C Large-lot approach AAAAAAAAAA BBBBBBBBBBB CCCCCCCCCC AAAAAA JIT approach AAA BBBBBB CC AAA BBBBBB CC AAA BBBBBB CC 14-10

11 3. Personnel/Organizational Elements Workers as assets for continuous improvement Cross-trained workers to add system flexibility and clear bottleneck Cost accounting 14-11

12 4. Manufacturing Planning and Control (1 of 3) Level capacity loading Establish stable production mix (A-B-C or B-A-C) at final assembly to provide balance into the system A Final Assembly B 14-12

13 4. Manufacturing Planning and Control (2 of 3) Pull systems/visual systems Push system: System for moving work where output t is pushed to the next station ti as it is completed (e.g. MRP) Pull system: System for moving work where a workstation pulls output from the preceding station as needed using a visual sign such as Kanban (e.g., JIT) 14-13

14 Kanban Production Control System Kanban is the Japanese word for card or visual sign. Authority to pull, or produce comes from a next operation or process

15 Pull systems/visual systems Machine center Assembly Storage Kanban Empty container Filled container 14-15

16 Pull systems/visual systems Machine center Assembly Storage A visible signal (Kanban) is used to notify the supplier of the need f more material at the next operation, and this results in pull system 14-16

17 Pull systems/visual systems Machine center Assembly Storage Supply batches are usually very small, and it requires tight schedules and frequent setups. Any inventory shortage, quality problem or process failure has immediate impacts

18 Ideal Number of Kanban Cards Amount of = inventory Daily (hourly) demand rate X Replenishment leadtime or cycle time in days (hours) NC = D T DT N = ( 1 + C X) X = efficiency factor, N = number of Kanban, C = container size 14-18

19 Example: Number of Containers (Kanban Cards) Determine the number of containers for a workstation that uses 100 parts per hour if the cycle time is 90 minutes and a standard d container holds 84 parts. Use an efficiency i factor of 0.1. D = 100/hour T = 90 minutes (1.5 hours) C = 84 parts X = 0.1 N = (100)(1.5) 84 ( ) =

20 4. Manufacturing Planning and Control (3 of 3) Close vendor relationships Reduced transaction processing 14-20

21 Traditional Supplier Network Buyer Suppler Suppler Suppler Suppler Suppler Suppler Suppler 14-21

22 Tiered Supplier Network Buyer First Tier Supplier Suppler Second Tier Supplier Suppler Suppler Third Tier Supplier Suppler Suppler Suppler Suppler 14-22

23 Summary JIT Goals and Building Blocks Ultimate Goal A balanced rapid flow Supporting Reduce setup Goals and lead times Eliminate disruptions Eliminate waste Make the system flexible Minimize inventories Product Design Process Design Personnel Elements Manufacturing Planning Building Blocks 14-23

24 Benefits of JIT Systems Reduced levels of inventories Reduced space requirements Increased product quality Reduced lead times Greater flexibility in product mix Smoother production flow Increased productivity levels Worker participation i i in problem solving Pressure for good vendor relationships Reduced need for indirect labor 14-24

25 Converting to a JIT System Get top management commitment Obtain support of workers Start by trying to reduce setup times Gradually convert operations Convert suppliers to JIT Prepare for obstacles 14-25

26 Obstacles to Conversion Management may not be committed Workers/management may not be cooperative Suppliers may resist 14-26

27 Chapter 15 JIT and Lean Operations Discussion questions 2, 3, 7, 8, 9, 11 Solved problem 1 Assigned problems