moulding problems

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1、MOULDINGPROBLEMS-Mould,MachineandMaterialrelatedMOULDINGPROBLEMSMOULDrelatedMACHINErelatedIN-CONSISTENTCRITICALDIMENSIONS·Unequalshrinkageduetovariationinmouldsurfacetemperature.Coolingcircuitdesignrelated.·Coreandcavitydimensionrelated.Correctshrinkageisnotconsidered

2、forcore/cavitydimension.Hold-onpressureandhold-ontimeinfluencestheshrinkage.Highpressureandtimereducestheshrinkage.Lowerpressureandtimeincreasestheshrinkageofthepart.shrinkageinthedirectionoforientationismore.dimensionscouldbecontrolledbycontrollingcoolingrateindiffer

3、entareasofthemouldwhenwallthicknessisnotconstant.CoolingratecouldbeincreasedbyusingBa-Cuinsertinthemould.SINKMARKSPartdesignrelated-nonuniformityofwallthickness.·Injectionspeedprofileandholdonpressureprofilecanminimisetosomeextent.·GasinjectionMouldingtechniquecanbeco

4、nsidered.WARP·Usetechniquetoimprovepartstiffnesswithpartdesign.·Randomdistributionofmouldsurfacetemperature.Coolingcircuitdesignrelated. WEAKWELDLINES弱熔接线Partdesignrelated.Injectionspeedcaninfluence.DEGRADATION降解Checkdimensionsofrunnersystemforexcessiveshearing.Excess

5、iveResidencetimeduetouseofoversizedinjectionunit.LoweringbarreltemperatureandinjectionspeedcanhavesomeinfluenceEJECTIONDIFFICULTYEJECTION难点Partdesignrelated-Unbalancedmeltflow.Useflowleadertoreduceunbalanceinflow. POORIMPACTstrengthRadiusatprojectionsandsharpcornersas

6、itactlikenotchfromwherecrackpropagates. IN-CONSISTENTWEIGHT. %ageutilisationofshotcapacityiscloserto90%resultingininconsistentmeltquality-ifmeteringstrokeismorethan3timesscrewdiameter.Borderlinecaseforshotweight.IN-CONSISTENTFILLINGIncreasegatesizetoreducepressuredrop

7、acrossthegate.Availablemaximuminjectionrateisnotadequateforflowratioofpartbeingmoulded.Borderlinecaseforinjectionrate.STRESSCRACKINGMeltflowisunbalanced.Partdesignrelated.Overpackedpart.Setcorrectpressureprofileduringpressurephase. MATERIALRELATEDPROBLEMSSINKMARKSFill

8、edpolymercanreducesinkmark.POORMECHANICALConsiderhighmolecularweightpolymers.STRENGTH机械强度差Considerfilledpolymers.Preheatpoly