Gate Vestige Control I’ve spent more time than I want to admit chasing gate vestige on Class A surfaces. The customer’s words still ring in my ears: “I can see the gate mark. Fix it.” Here’s how to control gate vestige on high-visibility parts.

Key Takeaways

| Aspect | Key Information |

Understanding Gate Vestige

What Is Gate Vestige? Gate vestige is the remnant of the gate after the gate is removed or the part is ejected. It includes the physical gate location, any witness mark, and the transition between the filled and non-filled areas.

Vestige Types TypeDescriptionSeverityGate buttonRaised gate materialSevereGate nickSmall raised areaModerateGate witnessSlight witness markMinorFlow lineFlow front witnessMinorGate blushSurface discolorationVaries

Gate Location Impact LocationVisibilityControl DifficultyHidden surfaceNot visibleEasyEdge (not visible)Minimally visibleModerateClass B surfaceModerately visibleDifficultClass A surfaceHighly visibleVery difficultCosmetic focal pointCritical visibilityExtremely difficult

Gate Design Strategies

Gate Type Comparison Gate TypeVestige SizeUseNotesEdge gateSmall-ModerateGeneral purposeGood balancePin gateSmallAestheticsMinimal witnessTunnel gate smallHidden areasGood for concealedSub gateModerateStrong partsLarger vestigeValve gateMinimalAestheticsBest appearanceHot tipSmall-ModerateGeneralNo runner, vestige varies

Gate Size Guidelines Gate SizeVestigeApplication0.020-0.030” pinMinimalSmall parts, aesthetics0.030-0.050” pinSmallGeneral precision0.050-0.080” pinModerateStandard production>0.080”LargeFlow critical, not visible

Gate Location Principles PrincipleRecommendationHidden locationPrioritize hidden areasFlow lengthMinimize flow from gatePressure centerGate at pressure centerWeld avoidanceDon’t gate at weld linesParting lineGate on parting line if possible

Process Optimization

Gate Freeze Control ParameterEffectAdjustmentMold temperatureHigher = slower freezeIncrease to extend freezeMelt temperatureHigher = slower freezeIncrease cautiouslyPack pressureCompensates shrinkageOptimize levelPack timeExtends packingExtend until stableGate coolingFaster = smaller vestigeCool aggressively

Vestige Reduction Settings AdjustmentImpactRiskIncrease pack pressureReduces vestigeFlash riskExtend pack timeReduces vestigeLonger cycleIncrease mold tempReduces vestigeLonger cycleOptimize gate sizeReduces vestigeTool modificationGate valve timingControls vestigeEquipment needed

Process Window for Vestige ZonePressureTimeVestige ResultUnder-packedLowShortLarge vestigeOptimalMediumAdequateMinimal vestigeOver-packedHighLongFlash risk

Secondary Operations

Manual Finishing MethodUseQualityHand trimmingGate removalVariableFiling/sandingVestige reductionGood if skilledSanding/polishingFinal finishExcellentBuffingHigh lusterExcellent

Mechanical Finishing MethodThroughputQualityNotesTumblingHighGood-FairMedia dependentVibratory finishingMediumGoodGentle actionBelt sandingMediumVery goodControlledCNC finishingLowExcellentPrecision

Chemical/Mechanical MethodUseEffectivenessSolvent polishingABS, PCGood for hazeVapor polishingClear partsExcellentScratch removalSurface marksGoodSanding sequenceControlledVery good

Visual Standards

Vestige Acceptance Criteria ClassAppearanceMax VestigeMeasurementClass ANo visible markBarely perceptible<0.002”Class BSlight mark acceptableVisible close-up<0.005”Class CMark acceptableVisible<0.010”HiddenAny acceptableNo restrictionNone

Visual Inspection Standard DistanceClass AClass BClass C12 inchesImperceptibleImperceptibleNoticeable3 feetImperceptibleNoticeableNoticeable6 feetNoticeableObviousObvious

Comparison Standards Standard TypeUseMaintenanceMaster partVisual comparisonReplace when wornGate standardVestige sizeCalibrate againstPhotographicReferenceUpdate regularlyWritten specReferenceReview annually

Troubleshooting Vestige Issues

Problem: Excessive Vestige Possible CauseDiagnosisSolutionGate too largeMeasure gateReduce gate sizeInsufficient packIncrease pressureOptimize packEarly gate freezeCheck freeze timeIncrease temp, timeMaterial too softCheck gradeHigher gradeGate designReview designRedesign gate

Problem: Irregular Vestige Possible CauseDiagnosisSolutionPressure variationMonitor pressureStabilize processTemperature variationCheck tempsImprove controlShot-to-shot variationCheck cushionAdjust cushionMaterial variationCheck lotsAdjust for variation

Problem: Vestige on Wrong Side Possible CauseDiagnosisSolutionGate locationReview designRelocate gateFlow patternObserve fillChange gatePart orientationCheck orientationRotate part

Documentation and Control

Vestige Control Plan ElementSpecificationGate type____________Gate size____________Gate location____________Target vestige____________Measurement method____________Acceptance criteria____________Control method____________Reaction plan____________

Process Parameters ParameterTargetRangeMonitoringMold temp180°F175-185°FContinuousMelt temp440°F435-445°FEvery shiftPack pressure800 psi750-850 psiEvery shotPack time2.5 sec2.0-3.0 secEvery shotGate vestige<0.003”<0.005”Hourly

Inspection Record DateTimeCavityVestigePass/FailAction______10.002”Pass_________20.004”MarginalAdjust pack______30.003”Pass___

Design Guidelines Checklist

Gate Design Gate type selected for vestige Gate size appropriate Gate location minimizes vestige Gate on hidden surface if possible Flow path optimized Weld lines avoided

Process Design Pack pressure optimized Pack time sufficient Mold temperature adequate Process window documented Control plan includes vestige

Quality Visual standard established Measurement method selected Sampling frequency defined Acceptance criteria clear Reaction plan documented

The Bottom Line Gate vestige on visible surfaces is solvable—but it requires attention from design through production. The gate design, the process parameters, and the quality control all matter. Don’t wait until production to discover a vestige problem. Design for it. improve the process. Control it in production. That’s how you deliver parts with gate marks that customers can’t see.