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IENG 451. JIT. Production Physics. Little’s Law Throughput = WIP/Cycle time For fixed capacity, cycle time and WIP or proportional – thus you can increase throughput either by increasing WIP or by decreasing cycle time . Production Physics.
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IENG 451 JIT
Production Physics • Little’s Law Throughput = WIP/Cycle time • For fixed capacity, cycle time and WIP or proportional – thus you can increase throughput either by increasing WIP or by decreasing cycle time
Production Physics • Law of variability – increasing variability inevitably degrades the performance of the system • Law of variability buffering – variability in a production system will be buffered by some combination of inventory, capacity, or time
JIT Principles • Don’t produce something unless a customer has ordered it • Level demand so that work may proceed smoothly throughout the plant • Link all processes to customer demands through visual tools (kanbans) • Maximize the flexibility of people and machinery
Pull Systems • Nobody upstream produces a good or a service until somebody downstream asks for it
Pull Systems • Nobody upstream produces a good or a service until somebody downstream asks for it
Pull Systems • Nobody upstream produces a good or a service until somebody downstream asks for it
Kanban Rules • Never ship defective items • Customer withdraws only what is needed • Produce only quantity withdrawn by the customer • Level production • Use kanban to fine-tune production • Stabilize and strengthen the process
Production orders • Batch of 10 vs Batch of 100 • Adjust more quickly to demand • Better sense of takt time • Fewer peaks and valleys • Better control of abnormality production
Pull Systems • Type A • Frequent orders with short lead times, most common, replenishing gaps created in the finished goods storage • Type B • Infrequent orders or long lead times, pacemaker is usually midstream • Type C • Combination of type A and type B running in parallel
Value Stream Mapping • VSM helps grasp current condition and identify improvement opportunities
VSM Steps • Determine the individual product or service you will map • Draw the process flow
VSM Steps • Add material flow
VSM Steps • Add Information flow
VSM Steps • Collect process data and connect it to boxes on chart • Add process and lead times