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

Chapter 14: JIT and Lean Operations  History of TOYOTA  Lean Production  Elimination of Waste  Kanban History of Toyota  Toyota switched from automated looms to military trucks just prior to WWII.  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. 2 2 1

Lean Production 精實生產 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. 3 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 4 2

Goals and Building Blocks of JIT 5 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 6 3

Heijunka (level loading) 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 7 Single Minute Exchange of Dies 快速換模 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 8 4

Jidoka (autonomation) automatic detection of problems Kaizen : Continuous Improvement 降低庫存迫使生產線必須面對並解決各種問題 9 Kanban 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 10 5

Pull System with Kanban Control 上游 6 2 4 1 P 看板 P 看板 C 看板 C 看板 市場 5 2 B B A A 7 3 前製程 後製程 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 11 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. Production Production Upstream 5 3 1 Kanban Kanban Demand B B A A 2 4 Input Output Input Output 12 6

Determining the Number of Kanbans Needed DT(1+X) N = 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 13 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. 14 7