Just in Time

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IEEM 517

Just-In-Time

LEARNING OBJECTIVES

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1. 2. 3.

Understand the philosophy of Just-In-Time (JIT) Learn the working procedure of JIT Know the differences between the two production-control systems, MRP (the push system) and JIT (the pull system)

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CONTENTS
• Motivation • JIT Philosophy • JIT Procedure – Toyota Kanban Systems • MRP vs. JIT • Summary

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PRODUCTION AND OPERATIONS MANAGEMENT
Product development long term Product portifolio Purchasing Supply network design Partner selection Supply contract design Manufacturing Facility location and layout Distribution Demand fulfillment

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Distribution network design

medium term

Derivative product development Adaptions Current product support

Aggregate planning

Demand forecasting Inventory management

short term

Materials ordering

Production control Operations scheduling

Distribution planning Transport planning

Fulfillment implementation

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INVENTORY MASKS PROBLEMS
excessive inventory

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low forecasting accuracy low product quality low productivity long leadtime … … Excessive inventory masks problems (water covers rocks) Reduced inventories reveal problems (rocks becomes visible)

EOQ AND EPL MODELS REVISITED
EOQ

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Y(Q*) = 2ADh + cD

EPL

 D Y(Q*) = 2ADh1 -  + cD  P

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CONTENTS
• Motivation • JIT Philosophy • JIT Procedure – Toyota Kanban Systems • MRP vs. JIT • Summary

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HISTORY OF JIT
Origin of JIT The idea and the practice of Just-in-time (JIT) were initiated in 1970’s at Toyota, the leading automobile manufacturer of Japan Characteristics of Manufacturing Environment in Japan • Limited working space • Closeness to suppliers and consumers • Small economy scale • Relatively uniform taste of consumers • Eastern culture (well organized, system-oriented, etc.) ⇒ Improving productivity and reducing inventory become necessary and possible

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GOALS OF JIT (ZERO INVENTORY)
• High product quality is essential ⇒ Goal is zero defects • High workstation reliability is necessary for high product quality ⇒ Goal is zero breakdowns • Frequent replenishments are desired ⇒ Goal is a lot size of one (zero excess lot size) • Reducing the setup cost is a necessary condition to achieve a lot size of one ⇒ Goal is zero setup cost • Handling time between workstations causes possible pauses ⇒ Goal is zero (additional) handling • Parts are provided from upstream whenever needed by downstream ⇒ Goal is zero leadtime • Parts are produced as needed and thus sudden changes in demand are not desired ⇒ Goal is zero surging

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OTHER ASPECTS OF JIT APPROACH
Less worker specialization Workers trained to use different machines. Plant is laid out so that a worker can operate two or three machines. May result in fewer workers Autonomation Autonomous defect control. Machines have automatic stop devices that can be pushed and thus allow a worker sees the situation. Entire line stops until problem is cleared up. Quality problems can be rapidly fixed Worker cooperation Workers help one another if there is a bottleneck. Workers suggestions are encouraged and rewarded Quality circles Workers become part of the quality control process Integrated production Close relationship with suppliers. Suppliers are encouraged to use JIT

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ENVIRONMENTS SUITED TO JIT
JIT is only one mechanism of production control. It should not be viewed as an all-purpose solution for all manufacturing systems. Characteristics of environments that are well suited to the JIT idea should include • Discrete parts produced in highly repetitive manner • Fairly smooth demand pattern throughout the time horizon • Small product line diversity • Setup time/costs can be greatly reduced • High worker flexibility • Closeness with suppliers • High level of quality management

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CONTENTS
• Motivation • JIT Philosophy • JIT Procedure – Toyota Kanban Systems • MRP vs. JIT • Summary

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DESCRIPTION OF KANBAN...
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