Dennis Bricker Dept of Mechanical & Industrial Engineering The University of Iowa. JIT --Intro 02/11/03 page 1 of 28

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1 Dennis Bricker Dept of Mechanical & Industrial Engineering The University of Iowa JIT --Intro 02/11/03 page 1 of 28

2 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 (e.g MRP) JIT --Intro 02/11/03 page 2 of 28

3 Pull system Production Control Send more widgets Send more widgets Information Flow Material Flow Production Step 2 Information Flow Material Flow Last Step of Production Here they come Here they come Production at Step 2 in controlled by step 3 JIT --Intro 02/11/03 page 3 of 28

4 Pull system Production Control Send more widgets Send more widgets First Step of Production Information Flow Material Flow Production Step 2 Information Flow Material Flow Here they come Here they come Production at Step 1 in controlled by step 2 JIT --Intro 02/11/03 page 4 of 28

5 a simple implementation of fixed-orderquantity/re-order point policy uses two bins for storage of an item. bottom bin contains items equal to the reorder point, together with an order form for the replenishment. JIT --Intro 02/11/03 page 5 of 28

6 when top bin becomes empty, worker removes it, sends the order form for the replenishment, and begins withdrawing from the bottom bin. when replenishment arrives, the bottom bin is refilled and the remainder placed in the top bin. This is a PULL system. JIT --Intro 02/11/03 page 6 of 28

7 Kanban System Kanban is the Japanese word for card. Paperless production control system Authority to pull, or produce comes from a downstream process. A physical (visual) control system Composed of cards (production card and withdrawal card) and containers rd) JIT --Intro 02/11/03 page 7 of 28

8 Kanban Cards the Kanban number (card ID) the part number the name & description of the part the place where the card is used the two work centers if a withdrawal card a single work center if a production card the number of units in the standard container JIT --Intro 02/11/03 page 8 of 28

9 Three Rules: A standard container must always be filled with the prescribed number of parts. A container must not be moved forward until authorized by receiving a withdrawal card. A container of parts must not be produced until authorized by a detached production card. JIT --Intro 02/11/03 page 9 of 28

10 JIT --Intro 02/11/03 page 10 of 28

11 Example: Kanban Flow Paths Inbound stockpoint I Work center B Withdrawal kanbans Production kanbans outbound stockpoint O Withdrawal kanbans Inbound stockpoint I Withdrawal kanbans Work center A Production kanbans outbound stockpoint O Withdrawal kanbans Inbound stockpoint I Final Assembly O outbound stockpoint supplier JIT --Intro 02/11/03 page 11 of 28

12 Sequence of Kanban Flows 1.Each container at an Inbound stockpoint has a withdrawal kanban attached. 2.When this container is selected for use in production at workcenter A, the worker detaches the withdrawal kanban and attaches it to an empty container. 3.This empty container is then sent to the Outbound stockpoint of B. 4.The withdrawal kanban is detached from the empty container and placed on a full container, leaving the empty container without a kanban. 5.The production kanban is removed from the full container and placed in a collection box. 6.The full replacement container (with only a withdrawal kanban) is sent to the Inbound stockpoint of A. 7.Regularly a worker at workcenter B collects the production kanbans from the collection box, and for each card, parts are produced and put into an empty container. 8.The filled container then has a production kanban attached to it and placed in the Outbound stockpoint of B. 9.Whenever worker at workcenter B selects a container of raw materials from its Inbound stockpoint, he attaches its withdrawal kanban to an empty container and sends to supplier. JIT --Intro 02/11/03 page 12 of 28

13 Waste in Operations Waste from overproduction Waste of waiting time Transportation waste Inventory waste Processing waste Waste of motion Waste from product defects JIT --Intro 02/11/03 page 13 of 28

14 Some Examples of Waste Watching a machine run Waiting for parts Counting parts Over-runs in production Moving parts over long distances Storing inventory Looking for tools Machine breakdown Rework JIT --Intro 02/11/03 page 14 of 28

15 Before JIT (material flow) Work Centers Final Assembly Stockrooms Supplier A Supplier B Initial Layout JIT --Intro 02/11/03 page 15 of 28

16 After JIT (material flow) Final Assembly Supplier A Supplier B JIT Layout JIT --Intro 02/11/03 page 16 of 28

17 Benefits of JIT Systems 1. Reduced inventory 2. Improved quality 3. Lower costs 4. Reduced space requirements 5. Shorter lead time 6. Increased productivity 7. Greater flexibility 8. Better relations with suppliers 9. Simplified scheduling and control activities 10. Increased capacity 11. Better use of human resources 12. More product variety JIT --Intro 02/11/03 page 17 of 28

18 JIT Reduced Waste at Hewlett-Packard Setup Lead Scra Finished Goods Inventory Spac Raw Material Inventory Work-in-Process Inventory 20% Waste Reduction (%) 30% 30% 40% 50% 50% 82% JIT --Intro 02/11/03 page 18 of 28

19 Basic Elements of JIT Pull (Kanban) production control system Small-lot production Quick setups Flexible resources Cellular layouts Uniform production Quality at the source Total productive maintenance Supplier networks JIT --Intro 02/11/03 page 19 of 28

20 Basic Elements of JIT Pull (Kanban) production control system Produce only what is needed - only when it is needed Small-lot production Faster through-put, greater flexibility Quick setups Facilitates economical small-lot-size production Flexible resources Facilitates cellular layouts, TPM, and Kaizen Cellular layouts Retain relevant flexibility of job shop, obtain efficiency of production line Uniform production Create and maintain a stable production system Quality at the source Facilitates removal of buffers and contributes to stability of the system Total productive maintenance Contributes to stability of the system Supplier networks Facilitates frequent, small quantity delivery of materials JIT --Intro 02/11/03 page 20 of 28

21 Inventory Hides Problems Bad Design Lengthy Setups Inefficient Layout Machine Breakdown Poor Quality Unreliable Supplier JIT --Intro 02/11/03 page 21 of 28

22 To Expose Problems: Reduce Inventory Levels Lengthy Setups Inefficient Layout Bad Design Machine Breakdown Poor Quality Unreliable Supplier JIT --Intro 02/11/03 page 22 of 28

23 Remove Sources of Problems and Repeat the Process Poor Quality Lengthy Setups Bad Design Inefficient Layout Machine Breakdown Unreliable Supplier JIT --Intro 02/11/03 page 23 of 28

24 Characteristics of JIT Vendor Partnerships Few, nearby suppliers Long-term contract agreements Steady supply rate Frequent deliveries in small lots Buyer helps suppliers meet quality Suppliers use process control charts Buyer schedules inbound freight JIT --Intro 02/11/03 page 24 of 28

25 Supplier Networks: Goals of Just-in-Time Purchasing elimination of unnecessary activities elimination of in-plant inventory elimination of in-transit inventory quality and reliability improvement JIT --Intro 02/11/03 page 25 of 28

26 Supplier Networks: Trends In Supplier Policies Locate near to the customer Use small, side loaded trucks and ship mixed loads Consider establishing small warehouses near to the customer or consolidating warehouses with other suppliers Use standardized containers and make deliveries according to a precise delivery schedule Become a certified supplier and accept payment at regular intervals rather than upon delivery JIT --Intro 02/11/03 page 26 of 28

27 Potential Supplier Concerns with Just-in-Time Purchasing Desire for diversification. Supplier is concerned about all business stemming from single customer. Poor customer scheduling. Supplier is concerned that customer will not be able to develop smooth, consistent schedule. Engineering changes. Supplier is concerned that customer will promulgate frequent engineering changes with inadequate lead time. Quality assurance. Supplier may consider production with zero defects unrealistic. Small lot sizes. Many suppliers are unaccustomed to working with small lot sizes. Proximity. Delivery of small lot sizes over long distances may not be economical. JIT --Intro 02/11/03 page 27 of 28

28 Respect for People Level payrolls Cooperative employee unions Subcontractor networks Bottom-round management style Quality circles JIT --Intro 02/11/03 page 28 of 28

Chapter 11. In-Time and Lean Production

Chapter 11. In-Time and Lean Production Chapter 11 Just-In In-Time and Lean Production What is JIT? Producing only what is needed, when it is needed A philosophy An integrated management system JIT s mandate: Eliminate all waste Basic Elements