Blown Film Processes and Troubleshooting

1 2009 Flexible Packaging SummitConsumer Packaging Solutions for Barrier Performance CourseBlown Film Processesand Troubleshootingand TroubleshootingThe Ultimate Quality Control ToolPresented by:Paul WallerPresidentPlastics Touchpoint Group, Film PropertiesPurchasingMaintenanceProductio nRaw MaterialPropertiesMWMWDD ensityProcessingConditionsOutputMelt TempFLHE quipmentMalfunctionsDie SizeDie GapAi RiDensityBranchingAdditivesFLHBURDDRAir RingIBCC ollapserCrystallinity & OrientationImpact StrengthOpticsTear StrengthShrinkageModulusTensile StrengthBarrier PropertiesSealabilitySurface TensionBubble in the Real WorldAir escaping from bubble from non-uniform closure of nip rollersCollapsing Framesnot concentrictoo tight on one sideAir currents on this side from open door or windowAir ring not adjusted correctlyUnstable bubble diameterReading the Signs1. Look at the finished roll2. Follow the web path pbackwards to identify causes of defects3.

2 Be changes take longer than othersWrinkle PatternsMD Wrinkles Fixed positionTD Wrinkles Repeating patterns Transient patterns Edge patternsMD WrinklesCompression in the Transverse DirectionBulge crossing rollerWrinkles oriented in MDMax. roller deflection < of roller widthTroughsCreaseCauses of CommonMD Wrinkle PatternsAsymmetrical MD WrinklesSymmetrical MD WrinklesRaw Material viscosity variation (port line affect) water absorption (causes expansion of web)Processing ConditionsMachine DirectionAsymmetrical MD WrinkleAsymmetrical MD WrinklesProcessing Conditions TD gauge variation insufficient web tension between idler rollersEquipment insufficient traction on idler rollers bent idler rollers idler roller bearing not rotating properlyFilm Tension BandsMay be caused by Too much film tension MD gauge bands ToomuchdragTo o much drag resistance from idler rollersLocking Rollers Causes ProblemsBGE Traversanip Wrinkles occur when air turning bar pressure is too high Tin Canning Solutions for Tin CanningMaterial Improve mixing inside die Increase modulus (density)

3 Of film Increase film gaugeProcess Reduce film tension Reduce film temperature Eliminate affect of aircurrentsEquipment Reduce drag resistance in collapsing frame Reduce drag resistance in bubble cage Match rotation speed of rollers to line speed Reduce width of spreader roller grooves Adjust position of spreader roller Reduce idler roller deflection Reduce drag resistance across idler rollersEliminate affect of air currentsOptimizing Collapsing AngleSide ViewNip RollersAngleWrinklesWrinkles form if Angle is too largeCollapsing FrameBubbleWrinklesCauses of CommonDiagonal Wrinkle PatternsAsymmetrical Edge WrinklesSymmetrical Edge WrinklesRaw Material viscosity variation (melt channelling)Processing Conditions Uneven web tension across Asymmetrical Edge WrinklesMachine DirectionAsymmetrical Center WrinklesEquipment insufficient traction on idler rollers bent idler rollers idler roller bearing not rotating properlythe web Uneven drag resistance in collapsing frameTension and Elastic ModulusWrinkles point toward region of lower tensionSlack film can cause wrinkles when entering nip rollersWrinklesmovetowardshigh Amount of force (stress) that plastic can withstand and still return to it original dimensions Winding tension must never exceed this valueToo TightToo LoosetensionSpiral Wrinkle PatternRoll PatternWeb PatternCalculating Film Tensionwith Air Loaded DancerTotal Pressure= pressure reading on gauge (Kg, psig)Pressure to raise dancer= pressure to make dancer float (Kg, psig)Gauge= film gauge (microns, mils)Width= width of film (mm, inches)

4 Layers= 1 for sheeting2 for tubingStarred or Spoked RollsStarred or Spoked Roll Deformation MechanismPressure from outside layerscompresses inner layersRoll deforms into star or spoked pattern because layers buckle when compression is too highMaterial Reduce density difference between layers (co-ex) Change layer ratio to avoid curling (co-ex)Process Adjust melt temp. to bring frost lines ltth()Solutions for Starred or Spoked Rollscloser together (co-ex) Reduce film temperature Reduce film tension at winder Reduce lay-on pressure at winderEquipment Improve winding tension control (watch movement of dancers)Affect of Tapered Gauge mils 7,000 layersLeft side460mm / 18 diameter90mm / 3- diameter coreRight side430mm / 17 / mil gauge differencefrom left to right edge Camber will cause film to track off center in converting equipment. Roller Misalignment PatternsRoller Misalignment PatternsFlatnsion> gauge> Tension> web spanWrinkles reach downstream roller and point toward narrow sideWrinkles appear to walk uphillFlatFilmWrinklesWeb TenMisalignment AngleSlack Edge (no wrinkles)< Tension> line speed< tractionSlack edge (low tension) with no wrinklesBubble MisalignmentBubble touches cageBubble does not touch cageMoves with oscillating nip?

5 YesRealign collapsing frame and side stabilizersNoProblem caused below collapsing frameEvidence of Misaligned Collapsing Frame80%100%DistanValve%Bubble (cm)Setpoint (cm)Nip changed directionNip oscillation stopped20 in19 in18 cm0%20%40%60%11:2411:2811:3211:3611:4011 :4411:4811:5211:56ance from SensorValve PositionTimeNip changed direction18 in17 in16 in15 inTapered RollsSolutions for Tapered RollsProcess Reduce melt temperature variation (melt channeling) Eliminate air drafts across bubbleEquipment Align die Align air ring Align cage Align collapsing frame Align haul-off nipAffect of Transfer Pipes on Flow ProfilesHeater BandFlangeClamping RingExit fromScreen ChangerFlow ProfileDownstreamMelt ChannelingSide Opposite Extruder is HotterMelt Flow at Exit from ElbowMelt Flow at Entrance to ElbowElbowAffect of Melt ChannelingAir RingExtruderSide Sow Belly Hot side becomes thinner before Peak TD Gauge Variation Linear PlotCollapsing FrameProcessingUneven melt flow insideConditionsdie (melt channeling)

6 Hot air rising from extruder orother air currents inside thefactoryEquipmentDie lip not centeredAir ring or IBC stack notcenteredTilted die ,air ring or IBC stackLinear PlotPolar PlotRinged RollsSolutions for Ringed RollsMaterial Reduce film COF (add slip)Process Keep film tension between 1% and 25% of ultimate tensile strengthEquipment Repair worn haul-off nips (slippage) Realign die, idlers, cage, collapsing frame Replace dull slitting blades Clean dirty rollers Eliminate web tension pulsationsEdge VariationSawtooth slippage in nip tension variation at slittersOscillation from side to side misaligned die, cage, collapsing Variation at Die Lips1 MI LDPE in HDPE Die at 200 C (395 F) Melt Temperature6 Ports, 6 Port Overlap, 2 mm (80 mils) Die Gap, 200 kg/hr (485 lb/hr) around the die (degrees)Flow Rate (kg/hr) Rate (lb/hr)Flow2000 SimulationCapacitance Type Gauge ProfilerAutomaticCalibrationOptionCapaci tance SensorOAKLANDINSTRUMENT CORPORATIONNip RollersFourier AnalysisOAKLANDINSTRUMENT CORPORATIONLook for causes of cycles that do not fit on the curveBefore Air Ring milsRange+23% / -25%Std Air Ring milsRange+29% / -59%Std Dev21%Affect of Misaligned Air / / / / mils38 9 / 1 50 milsABDie Position Gauge ProfileAir RingBubbleTiltedFrost LineNote gap between air ring and / / / / / / / / / mm / Die Gap mm mm / BC ADDieAffect of Tilted Air / / / / mils38 9 / 1 53 milsABDie Position Gauge ProfileTiltedFrost LineBubbleAir RingNote gap between air ring and / / /

7 / / / / / / mm / Die Gap mm mm / BC ADDieKey Air Ring AdjustmentsVelocity CONTROLSV olume COOLSDual Lip IrisSingle LipAir Ring Control PointsSingle and Dual Lip Air RingsDual Lip IrisgpDual LipStabilizer RingsDual LipPerforated ChimneyDual Lip IrisSingle LipAir Ring Control PointsSingle and Dual Lip Air RingsIncrease or decrease Air Ring blower speed to change venturi air flow and frost line heightuap sgpDual LipStabilizer RingsDual LipPerforated ChimneyIncrease or decrease IBC cooling rate (if available) to change melt strength and frost line heightOpen / Closeholes(if available)MD Gauge VariationHelical InstabilityLeft sideLeft sideRight sideUltrasonic Sensor Mounting Position282930313233340 90 180 270 355 IdealEndsCyclicSource: Joseph, Inc.

8 Uneven pressure distribution in oscillating die air plenums Static pressure changes either in cyclic pattern or when rotation changesEvidence of Leaking IBC Air Plenums60%80%100%DistanonValve%Bubble (cm)Setpoint (cm)20 in18 in16 cm0%20%40%60%15:3415:4215:5115:5916:0716 :1616:2416:32nce from SensorValve in14 in12 in10 in cm ( inch) change in bubble diameter within 12 minute cycleTD Gauge VariationOval Bubble with Thin BandsCollapsing FrameTD Gauge VariationDouble Peak Gauge ProfileCommon Causes uneven melt flow inside die die too cold (10 to 20 C / 20 to 40 F) back pressure too high dirty screens plugged air ring or IBC stack too much drag resistance in collapsing framePolar PlotLinear PlotDirty IBC StackTD Gauge VariationOval Bubble with Thick BandsTD Gauge VariationDouble Peak Gauge ProfileCollapsing FramePolar PlotLinear PlotCommon Causes Uneven melt flow inside die die too cold (10 to 20 C / 20 to 40 F)

9 Back pressure too high dirty screens Plugged air ring or IBC stackTD Gauge VariationEqual Number of Thick and Thin BandsCollapsing FrameTD Gauge VariationEqual Number of Thick and Thin BandsCommon Causes Uneven melt flow inside die die too hot (10 to 20 C / 20 to 40 F) back pressure too low dirty screens melt temperature variation too large (worn screw ) too much output Plugged air ring or IBC stackPolar PlotLinear PlotBottom of Die is Too ColdJaggedFrostLineLoose Die Heater BandsCompare heater ititposition to:parting lineother heater bandsCold Spots in DieHeater clamps should not be lined up. No heat supplied in this Between Die and Air RingCommon Air Distribution ProblemsUneven air flow from plenumsUneven air hose lengthKinked, leaking or melted air hosesAir hoses with sharp 180 bendsAir Hoses Too Close to Hot SpotsSurgingWatch the Chorus LineExtruderAmpsExtruderPressureFrost LineHeight All 3 parameters move up and down together Look for speed of cycle compared to screw speedSolids Bed RatioSolids BedMeltSolids Bed WidthMelt Pool WidthChannel WidthIndicates Melting Capacity of the ScrewConventional ScrewMelt FilmSolids BedMeltPoolWidth ChannelWidth Bed SolidsRatio Bed Solids=Solids Bed WedgingMelt PoolIntense friction plugs Solids Bed Channel and burns resinBarrier screw (unmelted pellets andblack specs)Unmelted pellets enter Melt PoolMelt FilmSolids Bed plugs melt flowMeltPoolChannelMelt FilmSolids BedSolids BedSolids Bed ChannelConventional screw (unmelted pellets)

10 200250392482 Old Barrel TemperatureNew Barrel TemperatureMelting Related mm (2- ) 28:1 L/D Barrier screw , 60 RPM, 110 kg/hr (245 lb/hr), 1 MI LLDPES olid Bed Wedging1. Lower Feed Zone temperature slightlyCaused by melting TOO QUICKLY050100150024681012141618202224262 8 Position along the barrel ( screw diameters)Temperature ( C)32122212302 Temperature ( F)2. Raise Zone 2 to soften resin more quickly3. Reduce output rate ( screw RPM)Solids Bed Break-upMelt FilmSolids Bed BreakupMeltPoolBarrier screw (unmelted pellets andblack specs)Melt PoolUnmelted pellets enter Melt PoolIntense friction plugs Solids Bed Channel and burns resinConventional screw (unmelted pellets)Solids Bed ChannelChannelMelt FilmSolids BedSolids Bed200250392482 Old Barrel TemperatureNew Barrel TemperatureMelting Related mm (2- ) 28:1 L/D Barrier screw , 60 RPM, 110 kg/hr (245 lb/hr), 1 MI LLDPEU nstable Solid Bed Break-up1. Lower Feed Zone temperature slightlyCaused by melting TOO QUICKLY050100150024681012141618202224262 8 Position along the barrel ( screw diameters)Temperature ( C)32122212302 Temperature ( F)2.