Just In Time (JIT) - Lecture notes 27-31 PDF

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Summary

Just-in-Time; Waste; Kanban; small-lot production; cellular layout; uniform production; kanban square; signal kanban; supplier kanban; flexible sources; Jidoka; Poka-yoke; Kaizen; total productive maintenance; diversification; scheduling; quality assurance; proximity ...

Description

Just In Time (JIT) What is JIT?  Producing only what is needed, when it is needed  A philosophy  An integrated management system  JIT’s objective: Improve profits and R.O.I  JIT’S mandate: Eliminate all waste. 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 Potential Benefits of JIT 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

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 is a System of Inter-Related Parts  Each of the elements support and facilitate many of the other elements!  If you implement only part of the system, you may get only part (or less) of the system’s potential benefits. How Basic Elements of JIT Contribute to the “System”  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

Types of Kanbans

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Kanban Square Marked area designed to hold items Signal Kanban Triangular Kanban used to signal production at the previous workstation. Material Kanban Used to order material in advance of a process Supplier Kanbans Rotate between the factory and suppliers

Small-Lot (size) Production  Requires less space & capital investment  Moves processes closer together  Makes quality problems easier to detect  Makes processes more dependent on each other Inventory Hides Problems  Bad design  Poor quality  Lengthy setups  Machine breakdown  Inefficient layout  Unreliable supplier Set-up Time (cost) Reduction: (SMED Principles) 1. Separate internal setup from external setup 2. Convert internal setup to external setup 3. Streamline all aspects of setup 4. Perform setup activities in parallel or eliminate them entirely Reducing Setup Time (cost)  Preset desired settings  Use quick fasteners  Use locator pins  Prevent misalignments  Eliminate tools & materials  Make movements easier

Flexible Sources

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Multifunctional workers Capable of multiple production tasks Capable of TPM, SQC, etc General purpose machines Preserve “flexibility” Less capital intensive

Cellular Layouts  Group dissimilar machines in manufacturing cell to produce family of parts  Work flows in one direction through cell  Cycle time adjusted by changing worker paths Uniform Production  Is obtained from smoothing production requirements  Kanban (pull) systems can handle +/- 10% demand changes  Smooths demand across planning horizon  Mixed-model assembly steadies component production Quality At The Source  Jidoka is authority to stop production line  Andon lights signal quality problems  Undercapacity scheduling allows for planning, problem solving & maintenance  Visual signals for production control makes problems apparent to everyone  Poka-yoke (mistake-proofing, not idiot proofing) prevents defects Kaizen    -

Continuous improvement Requires total employee involvement Essence of JIT is willingness of workers to: Spot quality problems Halt production when necessary Generate ideas for improvement Analyze problems Perform different functions

Total Productive Maintenance  Breakdown maintenance - Repairs to make failed machine operational  Preventative maintenance - System of periodic inspection & maintenance to keep machines operating  TPM combines preventative maintenance & total quality concepts TPM Requires Management To  Design products that can be easily produced on existing machines

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Design machines for easier operations, changeover, maintenance Train & refrain workers to operate machines Purchase machines that maximize productive potential Design preventive maintenance plans which span the life of equipment

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 Supplier Networks: Trends in Supplier Policies 1. Locate near to the customer 2. Use small, side loaded trucks and ship mixed loads 3. Consider establishing small warehouses near to the customer or consolidating warehouses with other suppliers. 4. Use standardized containers and make deliveries according to a precise delivery schedule 5. Become a certified supplier and accept payment at regular intervals rather than upon delivery 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 Implementation  Use JIT to finely tune an operating system  Somewhat different in USA than Japan  JIT is still evolving

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JIT isn’t for everyone

JIT in Services  Competition on speed & quality  Multifunctional department store workers  Work cells at fast-food restaurants  Just-in-time publishing for textbooks  Construction firms receiving material just as needed...