Chapter 14: JIT and Lean Operations History of TOYOTA Lean - - PDF document

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Chapter 14: JIT and Lean Operations

 History of TOYOTA  Lean Production  Elimination of Waste  Kanban

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 Toyota switched from automated looms to

military trucks just prior to WWII.

History of Toyota

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 Secondhand equipment and high unit costs forced

Toyota to reduce waste and improve quality whenever possible.

 TPS was not invented overnight

— it is the outcome of a long evolution.

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Lean Production 精實生產

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Just‐in‐time: A highly coordinated production system in which materials are moved through the system with precise timing, just as they are needed.

 JIT ← → MRP  JIT = lean production  Lean operations for service systems.

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The Toyota Approach

Muda: waste and inefficiency (浪費) Heijunka: workload leveling (平準化) Kaizen: continuous improvement (改善) Jidoka: automatic detection (自働化) Poka‐yoke: fool‐proofing to reduce errors Team concept: small teams for improvement (品管圈) Kanban (看板) Pull system: supplying material based on demand

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Goals and Building Blocks of JIT

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TOYOTA Production System

 Elimination of Muda

Inventory, Overproduction, Waiting time, Unnecessary transportation, Processing waste, Inefficient work methods, Product defects Muda: 庫存過多、生產量過多、待工待料、搬 運與包裝、產品設計過度、加工方法浪費或缺 乏效率、不良品

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Heijunka (level loading)

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根據實際需求安排生產計劃，使生產量與生產內容平準化

當月計劃生產 800A、 600B、 400C 每週生產 200A、 150B、 100C 每天生產 40A、 30B、 20C 實際現場排程 AAAABBBCC AAAABBBCC mixed model production

Single Minute Exchange of Dies 快速換模

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faster set up  smaller lot sizes  smaller inventory

internal setup external setup 事先調整定位、簡 易拆卸、預熱模具

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Jidoka (autonomation)

automatic detection of problems

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降低庫存迫使生產線必須面對並解決各種問題

Kaizen: Continuous Improvement Kanban

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看板是一種控制物料的方法，看板在物料生產過程中 提供相關資訊，包括時間、規格、數量、運送地點等

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Pull System with Kanban Control

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A B 前製程 後製程 A B 上游 1 市場 2 4

P看板

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P看板

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C看板

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C看板

運送看板(Conveyance)：各站完成加工的產品 必須得到下游的運送看板才能前進 生產看版(Production)：各站等待加工的產品 必須得到該站的生產看板才能進行加工

Single-Kanban Systems

 A unit cannot move to the next resource until it receives a

kanban card authorized by the downstream resource.

 The inventory at a resource is limited by the number of

kanban cards assigned to that resource.

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A B A B 1 Demand Upstream 5 4 Kanban 2 Kanban Input Output Input Output 3 Production Production

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Determining the Number of Kanbans Needed

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N = DT(1+X) C

N = Total number of kanbans D = Planned usage rate of using work center T = Average waiting time for replenishment of parts plus average production time for a container of parts X = Policy variable set by management – possible inefficiency in the system C = Capacity of a standard container

Conclusion

 Lean Production is suitable for assemble to stock, high

volume and low variety production.

 The goal is to achieve a balanced, smooth flow of production.  Key elements include quality at the source, elimination of

waste, continuous improvement, setup time reduction, workload leveling, kanban control.

 There is more to a successful operational turnaround than

the application of a set of tools. 是信仰，不是技術

 Mindsets of employees must be involved in the process.

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