CHAPTER 9

JUST IN TIME OPERATIONS MANAGEMENT

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JUST IN TIME DEFINED

Just-in-Time Manufacturing is an organization-wide quest to produce output within the minimum possible lead time and at the lowest possible cost by continuously identifying and eliminating all forms of waste and variance.

Waste is anything other than the minimum amount of equipment, materials, parts and human input that are absolutely necessary to achieve the desired rate of production.

– 7 가지의 Waste 의 형태– Waste as a Symptom of Problem : 예 ) Inventory as Waste : 비용발생 , 문제파악 불가능

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BENEFIT OF JIT MANUFACTURING

Inventory Reduction Quality Control Improvement Lead Time Reduction : setup & move Flexible work force Vendor Control/Performance Improvement : Power, delivery &

quality Continuous Improvement Total Productive Maintenance : Corrective → preventive

→productive → TPM Strategic Gain(SCA 수단 )

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HITORICAL ROOTS OF JIT MANUFACTURING

일본의 환경과 대응 ( Toyota 의 Taiichi Ohno)– Oil crisis→ 재고감소 ,– lacked capital resources→ 인적자원역할중요– rigorous competition → 비용과 생산성 경쟁

Ford’s Mass production system in JIT : techniques– Waste 제거 ( 엄격한 세부명세와 표준 설정 ), continuous i

mprovement, setup reduction-delay 방지 , improved housekeeping, level product scheduling, respect for people

Supermarkets and JIT Manufacturing : idea 와 vision– What is needed, at the time needed, in the amount needed

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THE GOAL & THE OBJECTIVES OF JIT MANUFACTURING

Goal : provide the right amount of product at the right time with the right quality level at the right place

objective– Produce only what the customers want.– Produce only as quickly as they want to use them.– Produce product with perfect quality.– Produce in the minimum possible lead times.– Produce goods with features that customers want

and no others.– Produce with no waste of labor, material or equipment; designate a

purpose for every movement to leave zero idle inventory.– Produce to enhance worker skill development.

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CRITICAL TRAITS OF JIT

The process supporting JIT must:– be able to produce small order sizes(1 단위 )– be able to respond to demand with short

lead times(customer demand vs. forcast)– place execution of operating plans in the hands

of workers, i.e., decentralize decision making– create an atmosphere that is intolerant of waste an

d ineffectiveness

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THE JIT TOOL

Kanban (pull scheduling) Level, mixed-model scheduling Setup reduction Poka-yoke (fool proofing) Quality at the Source Flexible, cross-trained workers Group technology Focused Factories Statistical process control Standardization/Simplification Supplier partnerships Kaizen

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PUSH SYSTEM & PULL SYSTEM

Push System– 부품을 구입하고 , 대량으로 생산– 수량 할인의 혜택– 구매와 생산의 규모의 경제– 과도하게 많은 재고를 보유 → 재고 통제 시스템에 의존

Pull System– 부품의 생산은 주문과 동시에 이루어짐– Component 는 구입하고 , 부품은 생산 → Pulled to the

next workstation based on need

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KANBANS IN OPERATION

Work Center AStatus: Idle

Work Center AStatus: Idle

Movement of Filled Bin

Work Center AStatus: Busy

Empty Bin

(c) Production KanbanMovement of

Empty Bin

(b) Withdrawal Kanban

(a)

Movement of Empty Bin

Work Center BStatus: Busy

Work Center BStatus: Busy

Work Center BStatus: Busy

Production Kanban

Withdrawal Kanban

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LEVEL, MIXED-MODEL SCHEDULING

Master production schedule(MPS)– A periodic(usually monthly) statement of the number of units of

each specific end product that an OM process will build and when it will build each product

Load Leveling– balance the rate of production with the rate of production with

the rate of at which the market wants products

Mixed-Model Scheduling– A method for setting a production sequence for end product

Benefit– Smoother response to market demand, simpler coordination of

supply, Flatter learning curve, less inventory

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SETUP REDUCTION

Setup cost– Process preparation time, Process teardown time,Learning time

Setup cost-Inventory trade-off objective

– Evolve toward lot sizes of 1 unit– Run every part every day– Make the first piece right every time– Keep setup times to 10 minutes

Procedures– Process flow analysis of setup times, Housekeeping, Practiced

teamwork

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POKA-YOKE/QUALITY AT THE SOURCE/FLEXIBL WORKERS

Poka-yoke– Design parts and processes in ways that make desired results inevita

ble– Method : color code, set up counter, place template

Quality at the Source– Target efforts to improve quality at the activities that produce it– Jidoka ( autonomation )– Stop-and-Fix/Line-Stop systems– Andons/Trouble lights

Flexible/cross-trained workers– Pay for skill

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GROUP TECHNOLOGY

유사한 특성을 지닌 제품이나 부품을 하나의 군 (family) 으로 묶고 , 이를 생산하는 기계의 군을 별도로 운영하는 것

제품이나 부품의 군은 크기 , 모양, 필요 작업 , 경로성의 유사점 , 수요 등의 요인에 기초하여 분류

부품을 군으로 분류한 다음에는 Cell 이라고 불리는 분리된 공간에, 이들 부품의 기본적인 공정에 필요한 기계 장치들을 설치

Functinal layout VS. GT– Shrink Physical distance– Eliminate the need for autom

ated material-handling equipment

– Produce orders with fewer setup

– Aviod relearning– Improve quality(visual inspe

ction)

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FOCUSED FACTORIES/SPC/SIMPLIFICATION

Focused Factories– 회사의 모든 제품을 한 곳에서 생산하던 대규모 공장을

다수의 소규모 공장으로 분할– 단일 System 이 다양한 목표를 달성하려고 노력하는

것보다는 특정한 목표 시장의 요구를 충족시키는 것 Statistical Process Control

– Process 의 성과를 관리하고 , Process 의 통제 상황을 평가 Standardization/simplification

– 단순화 : 불필요한 프로세스 단계 제거– 표준화 : 프로세스과업에 대한 표준화 시행

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SUPPLIER PARTNERSHIPS

Suppliers as sources of expertise– Problem solving at the buyer’s site, product design advice,

product design completion, problem solving at the supplier’s site

Suppliers as practitioners of quality at the source principles-supplier certification

Suppliers as timely communicators Suppliers as participants in cost reduction programs

– Long-term contracts, Narrow supplier bases, stable production plans

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LIMITATION OF JIT

No one business strategy is appropriate for all competitive situations.

Just-in-Time will have limited success if:– applied in a non-learning organization– management distrusts workers and vice versa– worker pay is based on individual incentives– demand does not permit:

load leveling product standardization

– product demand requires low volume production– does not have strong supplier relationships

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LEAN PRODUCTION & JIT

LEAN PRODUCTION is defined as an organization-wide OM system orientation to design and develop higher value products while consuming fewer resources for both direct and overhead.

It differs from JIT in that it:– emphasizes product mix flexibility as the key to

producing higher valued/niche products– extends supplier involvement to the design stage– focuses heavily on overhead reduction programs