注塑指导外国人的资料moulding.doc

Black discolouration Fault category Alternative terms Charred streaks, burn marks, periodic discolouration, dark spotsDescription Brown to black, irregular and locally variable discolouration of the moulded partPossible causesRemedial actionsFault category Alternative terms Charred streaks, burn marks, periodic discolouration, dark spotsDescription Brown to black, irregular and locally variable discolouration of the moulded partPossible causesRemedial actions1.Entrapped, compressed air in the mould leading to scorchingOptimise mould venting, particularly where flow fronts meet and at the end of flow paths. Correct flow front profile by adjusting section thickness, gate location or using flow leaders. Check venting channels. Reduce mould locking force. Evacuate mouldBlackening Fault category Alternative terms Diesel effectDescription Concentrated blackening at weld lines, e.g. near ribs or bosses, or in corners at the end of flow pathsPossible causesRemedial actions1.Unsuitable design of changes in cross section and bends in the hot runner, or faulty sealing faces leading to dead spots where the material becomes charred. Dead spots occurring at sealing faces, changes in cross section and bends in the hot runnerCheck and/or redesign the relevant components and sealing surfaces. Eliminate dead spots. Check the pressure relief holes for the needle shut-off mechanism. Inspect sealing faces. Check radii of bends and conical transitions from large to small diameter runner2.Wear on the screw, the non-return valve or the cylinderCheck the screw, the non-return valve and the cylinder for wearCloudiness Fault category Alternative terms Grey streaksDescription Dark, cloudy areas on part surfacePossible causesRemedial actions1.Plasticating unit contaminatedClean plasticating unit. Reduce screw speed2.Wear on the plasticating unitReplace complete plasticating unit or individual components. Use a corrosion and abrasion resistant plasticating unitColour inconsistencies Fault category Description Colour inconsistenciesPossible causesRemedial actions1.Material not sufficiently homogenisedIncrease back pressure, reduce screw speed2.Injection and screw speed too highReduce injection and screw speed3.Gate too narrowEnlarge gate4.Residence time too longReduce residence time by using a smaller plasticating unitConsistent discolouration Fault category Alternative terms Colour deviationsDescription Consistent deviation from the basic colour, particularly with light coloursPossible causesRemedial actions1.Melt temperature too highCheck melt temperature and reduce it if necessary2.Residence time too long, because plasticating unit not working at full capacityUse a smaller plasticating unit3.Unsuitable masterbatchUse a suitable masterbatch4.Production interrupted without reducing temperatureSee notes on production stoppagesDeeper colour at weld lines Fault category Description Found at weld lines or near faster or slower-moving flow fronts fed from neighbouring melt streamsPossible causesRemedial actions1.Pigment separation or light refraction effect caused by unfavourable flow at weld linesVary flow front velocity2.Thermal overloading of the melt leading to discoloration at weld linesReduce thermal load on the melt3.Oxidation due to insufficient ventingImprove venting, possibly by relocating the weld Rings around the gate Fault category Description Matt rings aligned concentrically around the gatePossible causesRemedial actions1.Stagnation of melt flow in the mould, melt temperature too lowTry to maintain an even melt flow, raise melt temperature2.Stagnation of melt flow in the mould, mould temperature too lowTry to maintain an even melt flow, raise mould temperature3.Injection rate too lowTry to maintain an even melt flow, increase injection rateStress whitening Fault category Description Areas of lighter colour combined with a velvety matt part surfacePossible causesRemedial actions1.Overstretching of the polymer matrix. Excessive mechanical stress during ejection. Poorly positioned ejector pins and draft angles too smallReduce mechanical stress during ejection. Position ejector pins near corners, domes and ribs (i.e. at stress whitening lines)2.Excessive stress in serviceMatch stress in service to materials properties3.Cavity pressure too high. Inadequate mould rigidityReduce cavity pressure. Increase mould rigidityDeformation of part Fault category Description Part deformed during demouldingPossible causesRemedial actions1.Cavity pressure too highOptimise injection speed. Reduce holding pressure. Switch to holding pressure at an earlier stage2.Inadequate mould rigidityStrengthen mould3.Cooling time too short or mould temperature too high in placesOptimise cooling / mould temperature control4.Poor mould design. Undercuts too pronounced, draft angles too smallOptimise mould design. Reduce size of undercuts and optimise draft angles5.Mould not sufficiently polished. Ejector pins poorly positioned or surface area too smallPolish cavity surface in direction of demoulding, choose a suitable surface coating or depth of texture. Optimise position and size of ejector pins (it is particularly important to locate them near corners, under ribs and bosses)Ejector marks Fault category Description Ejector marks clearly visible on partPossible causesRemedial actions1.Cavity pressure too highOptimise injection speed. Reduce holding pressure. Switch to holding pressure at an earlier stage2.Inadequate mould rigidityStrengthen mould3.Cooling time too short or mould temperature too high in placesOptimise cooling / mould temperature control4.Cooling time too short or mould temperature too high in placesOptimise cooling / mould temperature control5.Poor mould design. Undercuts too pronounced, draft angles too smallOptimise mould design. Reduce size of undercuts and optimise draft angles6.Mould not sufficiently polished. Ejector pins poorly positioned or surface area too smallPolish cavity surface in direction of demoulding, choose a suitable surface coating or depth of texture. Optimise position and size of ejector pins (it is particularly important to locate them near corners, under ribs and bosses)Mould opening noise Fault category Description Mould makes a lot of noise when openedPossible causesRemedial actions1.Draft angles too smallCheck mould polishing effectiveness and draft angles and re-machine if necessary. Use a suitable mould release agent2.Mould centring device defective or wornImprove mould centring3.Cavity pressure too highReduce cavity pressure. Switch from injection to holding pressure earlier. Reduce holding pressure4.Inadequate mould rigidityStrengthen mouldMould will not open Fault category Description Even when the maximum permissible mould opening force is applied, the mould halves cannot be separatedPossible causesRemedial actions1.Cavity pressure too highReduce cavity pressure. Switch from injection to holding pressure sooner. Reduce holding pressure. Increase melt temperature within acceptable limits2.Inadequate mould rigidityStrengthen mould3.Slide control not workingCheck position of slidesNotes Open mould: Use cold water to bring temp of mould down to room temp, install additional hydraulic rams betw platens to assist in opening mould. If necessary, raise temp of mould to above the glass transition temp of the resin, pull the mould halves apartPart remains in mould cavity Fault category Description Part jams, cores or ejectors deform or puncture partPossible causesRemedial actions1.Mould overloadedReduce injection speed and holding pressure, and switch to holding pressure at an earlier stage2.Undercuts too pronounced, draft angles too smallReduce size of undercuts and improve draft angles3.Mould not sufficiently polished at ribs and bossesPolish cavity surface in direction of demoulding4.Vacuum between mould surface and partOptimise mould venting5.Premature demould: part sticks or is still too softIncrease cooling time, reduce mould temperature6.Ejector pins poorly positioned or too few in numberUse more ejector pins or optimise their positionPart ruptures during demould Fault category Description Part damaged during demouldingPossible causesRemedial actions1.Cavity pressure too highOptimise injection speed. Reduce holding pressure. Switch to holding pressure at an earlier stage2.Inadequate mould rigidityStrengthen mould3.Cooling time too short or mould temperature too high in placesOptimise cooling / mould temperature control4.Poor mould design. Undercuts too pronounced, draft angles too smallOptimise mould design. Reduce size of undercuts and optimise draft angles5.Mould not sufficiently polished. Ejector pins poorly positioned or surface area too smallPolish cavity surface in direction of demoulding, choose a suitable surface coating or depth of texture. Optimise position and size of ejector pins (it is particularly important to locate them near corners, under ribs and bosses)6.Material not adequately dried, residence time too longCheck drying of material, residence time and melt temperatureSticking sprue Fault category Description Sprue is constricted and/or left in the sprue bush or in the cold runnerPossible causesRemedial actions1.Processing parameters not ideal (e.g. timing of changeover from injection to holding pressure, level of holding pressure)Optimise processing parameters. Reduce cavity pressure by reducing holding pressure and switching to it earlier. Check, and if necessary, extend cooling time2.Nozzle radius or aperture too largeReduce nozzle radius or aperture3.Draft angles too small or polishing inadequateCheck components like injection nozzle, cold runner and gate for undercuts and polishing effectiveness, and re-machine in demoulding direction if necessary. Optimise draft angles and polish if necessaryDamaged grain on the moulded article Fault category Description Rough, torn surface with grooves in the direction of demoulding, mostly at the same placePossible causesRemedial actions1.Draft angles too smallIncrease draft angles2.Mould surface damagedRe-machine mould surface3.Cavity pressure too highReduce cavity pressure. Switch from injection to holding pressure earlier. Reduce holding pressure. Optimise injection rate. Increase melt temperature within acceptable limits4.Inadequate mould rigidityStrengthen mouldNotes Grooves are often only detectable with optical aidsDull spots Fault category Alternative terms Matt patchesDescription Uniform, clearly defined velvety areas on surfacePossible causesRemedial actions1.Flow fronts with different velocities (with several gating points)Even out differences in flow front velocities by improving the balance of the gating system (where several feed points are involved)2.Tearing of already solidified outer skin at sharp bends and abrupt changes in wall thicknessRound off or polish transition zones and abrupt changes in wall thickness in the runner and mould; balance flow front velocitiesNotes See also: FlakingFrosting Fault category Description Rough, matt part surfacesPossible causesRemedial actions1.Injection speed too lowRaise injection speed2.Mould temperature too lowRaise the temperature of the mould. Fit thermal insulation round mould. Use a more efficient temperature control unitNotes Only occurs with glass reinforced thermoplastics, and is more noticeable with amorphous than with partially crystalline thermoplasticsLocalised, glossy, finger-shaped depressions Fault category Alternative terms Tacky spotsDescription Glossy depressions, often near the sprue, at cores or in the vicinity of hot runner unitsPossible causesRemedial actions1.Premature demouldExtend cycle time2.Holding pressure too low and holding pressure time too shortIncrease holding pressure, increase holding pressure time, check melt cushion, check, and if necessary increase nozzle aperture and gate cross section3.Switch from injection to holding pressure made too soonSwitch to holding pressure at a later stage4.Mould temperature too high in placesReduce mould temperature locally by means of additional cooling channels or separate temperature controlNotes See also: Matt surface defectsMatt surface defects near hot runner units Fault category Description Rough, torn and therefore matt-effect surface near hot runner units or hot coresPossible causesRemedial actions1.Premature demouldIncrease cooling time2.Mould temperature at hot runner too highImprove thermal isolation of hot runners, reduce mould temperature3.Core temperature too highMake sure core is adequately cooledPoor gloss Fault category Description Part does not meet gloss requirements (either over the whole surface or in a certain area)Possible causesRemedial actions1.Mould worn or not properly polishedPolish mould thoroughly2.Injection speed too low, possibly due to poor ventingIncrease injection speed, if necessary by improved venting3.Fluctuations in mould temperature caused by inadequate coolingCheck consistency of mould temperature4.Material not properly driedCheck drying process5.Holding pressure ineffectiveImprove effectiveness of holding pressure by increasing holding pressure, extending holding pressure time and if necessary increasing gate size Poor matt effect on textured surfaces Fault category Description Part surface does not meet mattness requirementsPossible causesRemedial actions1.Injection speed and mould temperature too lowIncrease injection speed and mould temperature2.Holding pressure ineffectiveSwitch to holding pressure at a later stage and increase its level3.Surface texture of mould cavity poor or wornRe-machine mould surface Poor matt effect on textured surfaces Fault category Description Part surface does not meet mattness requirements Possible causes Remedial actions 1. Injection speed and mould temperature too low Increase injection speed and mould temperature 2. Holding pressure ineffective Switch to holding pressure at a later stage and increase its level 3. Surface texture of mould cavity poor or worn Re-machine mould surfaceVariations in gloss on the surface of the moulded article Fault category Description Variations in gloss over all or part of the surface of the articlePossible causesRemedial actions1.Injection speed too lowRaise injection speed2.Cavity surface worn or corrodedRe-machine mould surface3.Fluctuations in mould temperature. Problems in the temperature control circuit, e.g. leakage, blocked cooling channel, temperature control unit defectiveService the temperature control system and eliminate any leaks. Improve temperature control by adding more heating-cooling channels, increasing the throughput of the temperature control medium or changing the medium (e.g. use water instead of oil)White spots Fault category Description Rough, whitish, flake-like surface blemishes or whitish, round or oval mildewy areasPossible causesRemedial actions1.Excessive moisture in materialCheck dryer or monitor drying process2.Melt temperature too high, residence time in cylinder and hot runner too long (only with glass reinforced PA)Check melt temperature, residence time and screw speed (only with glass reiDefective integral hinges Fault category Description Integral hinges tear or fracture under loadPossible causesRemedial actions1.Incorrect resin used, e.g. amorphous thermoplasticUse a suitable (partially crystalline) thermoplastic2.Poor design (weld line too near integral hinge)Modify position of weld lines and consult design guidelines for integral hingesInadequate weld line strength Fault category Description Failure of part near weld linePossible causesRemedial actions1.Insufficient mould ventingImprove mould venting2.Inadequate flow properties of the resin. Injection speed too