IENG 451

JIT

Production Physics

• Little’s LawThroughput = 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• Never ship defective items• Customer withdraws only what is needed • Produce only quantity withdrawn by the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

Process Flow Tools

• Process Mapping • SIPOC – Supplier, Inputs, Process, Outputs, Customers

• Spaghetti diagrams• Swim Lane flow charts• Value Stream Mapping

SIPOC Charts

Value Stream Mapping

• VSM helps grasp current condition and identify improvement opportunities

• Improvement events create localized improvements; VSM provides a vision and plans that connect all improvement activities

• VSM allows you to see waste and plan to eliminate it

What is VSM

• Planning tool to optimize results of reducing waste

Five Principles for VSM

• Specify value from end customer standpoint• Identify value stream for each product family• Make the product flow• Customer pulls the system • Manage towards

perfection

Value to Customer ?

• How does current product / process disappoint customers value expectation:– Price ?– Quality ?– Delivery ?

What Flows

• Manufacturing; materials are the items that flow

• Design & development; designs flow• Service; customer needs are the items• Administration; internal customer needs are

the items

Current State (Manuf.)

Future State – (Manuf.)

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