Just In Time Injection Molding Just-in-Time sounds simple: make only what you need, when you need it. But in practice, JIT in molding requires significant preparation and discipline. Here’s how to use JIT in injection molding.

Key Takeaways

| Aspect | Key Information |

Understanding JIT in Molding

JIT Principles PrincipleApplicationEliminate wasteNo excess inventoryFlow productionSingle-piece flowPull systemProduce to demandPerfect qualityZero defectsContinuous improvementAlways getting better

JIT Benefits BenefitImpactInventory reduction50-80% lower WIPFloor space30-50% reductionQuality improvementFaster feedbackCash flowLower tied-up capitalResponsivenessFaster to changes

JIT Requirements

Prerequisites RequirementWhy It MattersImplementationStable demandPull requires predictabilityForecasting, levelingReliable equipmentNo machines = no JITTPM, preventive maintenanceShort changeoversFrequent small lotsSMED implementationSupplier reliabilityMaterial on demandStrong supplier relationshipsQuality at sourceNo defects pass downstreamPoka-yoke, SPC

Molding-Specific Requirements RequirementChallengeSolutionMachine availabilityShared resourcesDedicated cellsChangeoversTime to switchQuick changeoverTool availabilityMultiple toolsTool managementMaterial supplyBulk deliveryKanban, JIT delivery

Pull Systems

Kanban in Molding Kanban TypeUseInformationProduction kanbanSchedule productionPart number, quantityWithdrawal kanbanMove partsFrom where, to whereSupplier kanbanOrder materialMaterial, quantity

Kanban Calculation ParameterFormulaExampleDaily demandParts/day1,000 partsContainer sizeParts/container100 partsLead timeDays to produce2 daysSafety stockDays of buffer0.5 daysKanban count(Daily × Lead + Safety) / Container(1,000 × 2.5) / 100 = 25

Container Systems ElementSpecificationContainer size1-2 hours of demandNumber of containersBased on kanban calculationWithdrawal frequency1-4 times per shiftReplenishment timeBased on distance

Implementation Roadmap

Phase 1: Foundation (Months 1-3) ActivityOutputCurrent state analysisValue stream mapIdentify wasteTop 10 opportunitiesEstablish stabilityTPM, quality focusSupplier dialogueJIT readiness assessment

Phase 2: Quick Wins (Months 3-6) ActivityTargetReduce changeover50% reductionContainer system1-2 part familiesVisual managementAndon, boardsMaterial deliveryDaily instead of weekly

Phase 3: Pull System (Months 6-12) ActivityTargetKanban implementedKey part familiesLevel productionHeijunka boxSupplier kanbanKey materialsSupermarket pullWhere appropriate

Phase 4: Continuous Flow (Months 12-24) ActivityTargetCell designU-shaped cellsOne-piece flowWhere possibleTakt timeMatched to demandFull JITStandard work

JIT Metrics

Key Performance Indicators MetricCalculationTargetInventory turnsCOGS / Average inventory>10/yearWIP daysWIP / Daily COGS<5 daysLead timeOrder to shipment<1 weekChangeover timeTotal / Number<30 minutesSchedule adherenceOn-time schedule>95%

Measurement Frequency MetricFrequencyInventory turnsMonthlyWIP levelsDailyLead timePer orderChangeover timePer changeoverSchedule adherenceDaily

JIT Challenges in Molding

Common Challenges ChallengeRoot CauseSolutionMachine sharingMultiple productsDedicated capacityLong changeoversComplex toolsSMEDTool availabilityMultiple programsTool management systemMaterial availabilityBulk deliveryJIT delivery agreementsQuality issuesProcess instabilityQuality at source

Problem-Solving Approaches ProblemMethodActionMissed deliveryRoot cause analysisFix the problemQuality issuePoka-yokePrevent recurrenceChangeover delayTime studyReduce elementsStockoutPull systemIncrease visibility

JIT and Suppliers

Supplier Integration LevelRelationshipInformation SharingTransactionalArms-lengthOrdersCooperativePartnershipForecasts, plansCollaborativeStrategicFull integrationJIT/VMIPartnershipReal-time data

Supplier Performance MetricTargetMonitoringOn-time delivery>98%Daily trackingQuality<0.5% PPMPer lotLead time variability<5%Weekly reviewFlexibility24-hour responseEmergency requests

JIT Implementation Checklist

Preparation Value stream mapped Waste identified Stability achieved Supplier readiness assessed Investment approved

Quick Wins Changeovers reduced Containers implemented Visual management active Material delivery improved Operators trained

Pull System Kanban calculated Kanban implemented Supermarket established Level production started Daily management active

Continuous Flow Cells designed Flow established Takt time matched Full JIT operational Continuous improvement active

The Bottom Line JIT isn’t about doing without—it’s about eliminating waste. Lower inventory. Faster response. Better quality. Happier customers. But JIT requires preparation. You need stable processes, reliable equipment, and capable suppliers. Without those, JIT just means running out of parts faster. Build the foundation. use incrementally. Stay disciplined. That’s how JIT provides value.