Lean ProductionBeni Asllani University of Tennessee at ChattanoogaOperations Management - 5th EditionChapter 15Roberta Russell & Bernard W. Taylor, III

Lecture OutlineBasic Elements of Lean ProductionBenefits of Lean ProductionImplementing Lean ProductionLean Services

Lean ProductionDoing more with less inventory, fewer workers, less spaceJust-in-time (JIT)smoothing the flow of material to arrive just as it is neededJIT and Lean Production are used interchangeablyMudawaste, anything other than that which adds value to the product or service

Waste in Operations

Waste in Operations (cont.)

Waste in Operations (cont.)

Basic ElementsFlexible resourcesCellular layoutsPull production systemKanban production controlSmall lot productionQuick setupsUniform production levelsTotal productive maintenanceSupplier networks

Flexible ResourcesMultifunctional workersperform more than one jobgeneral-purpose machines perform several basic functionsCycle timetime required for the worker to complete one pass through the operations assignedTakt timepaces production to customer demand

Standard Operating Routine for a Worker

Cellular LayoutsManufacturing cellscomprised of dissimilar machines brought together to manufacture a family of partsCycle time is adjusted to match takt time by changing worker paths

Cells with Worker Routes

Worker Routes Lengthen as Volume Decreases

Pull SystemMaterial is pulled through the system when neededReversal of traditional push system where material is pushed according to a scheduleForces cooperationPrevent over and underproductionWhile push systems rely on a predetermined schedule, pull systems rely on customer requests

KanbansCard which indicates standard quantity of productionDerived from two-bin inventory systemMaintain discipline of pull productionAuthorize production and movement of goods

Sample Kanban

Origin of Kanban

Types of KanbanProduction kanbanauthorizes production of goodsWithdrawal kanbanauthorizes movement of goodsKanban squarea marked area designated to hold itemsSignal kanbana triangular kanban used to signal production at the previous workstationMaterial kanbanused to order material in advance of a processSupplier kanbanrotates between the factory and suppliers

Determining Number of Kanbanswhere

N = number of kanbans or containersd = average demand over some time periodL = lead time to replenish an orderS = safety stockC = container size

Determining Number of Kanbans: Exampled = 150 bottles per hourL = 30 minutes = 0.5 hoursS = 0.10(150 x 0.5) = 7.5C = 25 bottlesRound up to 4 (to allow some slack) or down to 3 (to force improvement)

Small LotsRequire less space and capital investmentMove processes closer togetherMake quality problems easier to detectMake processes more dependent on each other

Components of Lead TimeProcessing timeReduce number of items or improve efficiencyMove timeReduce distances, simplify movements, standardize routingsWaiting timeBetter scheduling, sufficient capacitySetup timeGenerally the biggest bottleneck

Quick SetupsInternal setupCan be performed only when a process is stoppedExternal setupCan be performed in advance

SMED PrinciplesSeparate internal setup from external setupConvert internal setup to external setupStreamline all aspects of setupPerform setup activities in parallel or eliminate them entirely

Common Techniques for Reducing Setup Time

Common Techniques for Reducing Setup Time (cont.)

Common Techniques for Reducing Setup Time (cont.)

Uniform Production LevelsResult from smoothing production requirementsKanban systems can handle +/- 10% demand changesSmooth demand across planning horizonMixed-model assembly steadies component production

Mixed-Model Sequencing

Quality at the SourceVisual controlmakes problems visible

Poka-yokesprevent defects from occurringKaizena system of continuous improvement; change for the good of allJidokaauthority to stop the production lineAndonscall lights that signal quality problemsUnder-capacity schedulingleaves time for planning, problem solving, and maintenance

Examples of Visual Control

Examples of Visual Control (cont.)

Examples of Visual Control (cont.)

Total Productive Maintenance (TPM)Breakdown maintenanceRepairs to make failed machine operationalPreventive maintenanceSystem of periodic inspection and maintenance to keep machines operatingTPM combines preventive maintenance and total quality concepts

TPM RequirementsDesign products that can be easily produced on existing machinesDesign machines for easier operation, changeover, maintenanceTrain and retrain workers to operate machinesPurchase machines that maximize productive potentialDesign preventive maintenance plan spanning life of machine

Unneeded equipment, tools, furniture; unneeded items on walls, bulletins; items blocking aisles or stacked in corners; unneeded inventory, supplies, parts; safety hazardsItems not in their correct places; correct places not obvious; aisles, workstations, & equipment locations not indicated; items not put away immediately after useFloors, walls, stairs, equipment, & surfaces not lines, clean; cleaning materials not easily accessible; labels, signs broken or unclean; other cleaning problemsNecessary information not visible; standards not known; checklists missing; quantities and limits not easily recognizable; items cant be located within 30 secondsNumber of workers without 5S training; number of daily 5S inspections not performed; number of personal items not stored; number of times job aids not available or up-to-dateKeep only what you need

A place for everything and everything in its place Cleaning, and looking for ways to keep clean and organized

Maintaining and monitoring the first three categoriesSticking to the rulesSeiri(sort)

Seiton(set in order)

Seisou(shine)

Seiketsu(standardize)

Shisuke(sustain)

Supplier NetworksLong-term supplier contractsSynchronized productionSupplier certificationMixed loads and frequent deliveriesPrecise delivery schedulesStandardized, sequenced deliveryLocating in close proximity to the customer

Benefits of Lean ProductionReduced inventoryImproved qualityLower costsReduced space requirementsShorter lead timeIncreased productivity

Benefits of Lean Production (cont.)Greater flexibilityBetter relations with suppliersSimplified scheduling and control activitiesIncreased capacityBetter use of human resourcesMore product variety

Implementing Lean ProductionUse lean production to finely tune an operating systemSomewhat different in USA than JapanLean production is still evolvingLean production isnt for everyone

Lean ServicesBasic elements of lean production apply equally to servicesMost prevalent applicationslean retailinglean bankinglean health care

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