模具外文翻譯-開(kāi)發(fā)注塑塑料零件變形分析的測(cè)試方法【中文4190字】【PDF+中文WORD】,中文4190字,PDF+中文WORD,模具,外文,翻譯,開(kāi)發(fā),注塑,塑料零件,變形,分析,測(cè)試,方法,中文,4190,PDF,WORD Test MethodTest method development for deformation analysis of injection mouldedplastic partsJ.G.Kovcs*,B.SiklDepartment of Polymer Engineering,Budapest University of Technology and Economics,H-1111 Budapest,Muegyetem rkp.3,Hungarya r t i c l e i n f oArticle history:Received 9 March 2011Accepted 19 April 2011Keywords:WarpageCorner effectInjection mouldingDeformationInjection moulda b s t r a c tThe characterisation of warpage of injection moulded plastic parts is not standardised andis extremely problematic due to the complex nature of the warping process.This paperpresents a novel method for the analysis and measurement of the deformation of injectionmoulded plastic parts.A specific part with a special mould design was introduced for thecharacterisation of the effect of different technological parameters and different mouldelement design on warpage.The applicability of the system was demonstrated via itsexperimental use.The effects of mould temperature,mould temperature difference,holding pressure and the glass fibre content of the material were investigated usingdifferent gate types in the mould.Additionally,new software was developed to evaluatewarpage.Based on the results,it was concluded that the deformation of the corner alongthe edge length can be described by a curve.?2011 Elsevier Ltd.All rights reserved.1.IntroductionThe quality of injection moulded thermoplastic parts islargely determined by the process parameters and themould design used.One of the main problems with injec-tionmouldedplasticpartsiswarpagecausedbynon-uniformshrinkage.Thisdeformationisstronglyinfluenced by non-uniform cooling,differential shrinkageand orientation effects 1.Several researchers have investigated the formation andcharacteristics of warpage using various methods,partic-ularly multiple types of specimen geometries.Many studieshave investigated shrinkage using rectangular plate speci-mens 2,3,and the application of this geometry wasextended to warpage measurements 49.Tang et al.10,11 introduced a two-cavity,two-plateinjection mould producing acrylonitrile butadiene styrene(ABS)plates for warpage testing,with deformation of theparts being determined with a dial gauge.The authorsconcluded that warpage was mostly influenced by melttemperature,followed by packing time and packing pres-sure.Thermal analysis was performed to check the effect ofany thermal residual stress in the mould.Fahy 12 investigated the warpage of reinforced ther-moplastics on a circular disk and showed that differentorientation caused various deformations;namely,theyobserved cup-and saddle-shaped conformations.Kikuchiand Koyama 13,14 also analysed disk specimens andplates,and they introduced a warpage index as a means ofrecording the characteristics of injection moulded parts.Zheng et al.15 acknowledged that plate-like speci-mens were incapable of measuring warpage of injectionmoulded parts because of their simple geometry,andproposed that a more complex shape should be used.Theycontinued to perform measurements with the injectionmoulding simulation on a ribbed plate model,but theywere only able to visualise the effect of the rib and not theentire deformation 15.Jansen 8 studied the warpage of amorphous materialsnot only on plates but also on L-shaped specimens withdifferent corner radii and sharp corners.The warpage of flatplate products was assessed by positioning the plate on*Corresponding author.Tel.:36 14631440.E-mail addresses:kovacspt.bme.hu(J.G.Kovcs),siklopt.bme.hu(B.Sikl).Contents lists available at ScienceDirectPolymer Testingjournal homepage: front matter?2011 Elsevier Ltd.All rights reserved.doi:10.1016/j.polymertesting.2011.04.011Polymer Testing 30(2011)543547threesupportingpinsandmeasuringtheverticaldisplacement as a function of the length coordinate.Theexperiments showed that deformation linearly increasedwith the difference between the temperatures of the mouldhalves when using amorphous polymers.The results alsoshowed that at low holding pressure the plates curvedtowards the hot side,whereas at high holding pressure theplates curved towards the cold side.The corners with largerradiiweremoresensitivetomould temperaturedifferencesthan were specimens with smaller radii.The result wasexplained by the proportionality of the angle deflection tothe length of the radial section.Akay et al.9 also analysed the relationship betweenwarpage and the temperature difference of the two halvesof the mould.The deformation of both the flat plate andthe L-shaped specimens was measured and calculatedwith finite element software and a coordinate-measuringmachine.Then,it was analysed using uniform cooling andalso with temperature difference between the two mouldhalves.It was observed that a higher mould temperature onthe cavity side resulted in increase of the angle in thecorner of the part.Some investigations used box geometry for warpageanalysis 16,17.Kabanemi et al.17 analysed warpage onbox-like parts.Different cases were presented to show theinfluence of the geometrical complexity of the shape on thedeformations and residual stresses.It was concluded thatthe asymmetrical thermal profile was responsible for thebending moment that caused warpage.Mlekusch 18 analysed the warpage on a specificallydesigned part with various types of corners.The effect ofshort-fibre-reinforcement was studied and attributed tothe anisotropy of the material.A multi-layer model wasused to calculate the cooling of a cylindrical segment.Themodel predictions were compared with experimentalmeasurementsshowingthattheadditionalwarpageobserved for short-fibre-reinforced materials could beattributed to the anisotropy of the material.Ammar et al.19 used a specimen with four cornerswith different radii.They concluded that two phenomenacaused warpage:the first was asymmetrical cooling andthe second was the spring forward effect.The springforward effect was generated in fibre-reinforced materialsdue to the higher thermal expansion coefficient in thethickness direction.The deformation around the cornerand the deformation of the initially flat surfaces weredistinguished.Using polypropylene(PP)in their experi-ments,equal mould temperatures in both mould halvesinduced a significant angle deformation of 3?and 5?.A difference of 40?C between the two mould halves causedan angle variation of about 1.5?.The aim of this research was to create not only a spec-imen but also a complex method for warpage character-isation.The main goal was to design and create a specificsample and mould,which allows deformation measure-ments to be obtained in different manners.2.Methodology and measuring equipmentTo characterise the warpage at the corners of injectionmoulded parts,a special part was designed.The main goalwas to measure the effect of varying technological param-eters,mould design or material properties on warpage.To produce the so called V-top specimens,a specialmould was designed with changeable and variable inserts(Fig.1.).The constructed insert mould slides into a quick-change frame and has two cavities with a variable runnerFig.1.The moving and stationary sides of the mould with the 3 1 gate inserts.Fig.2.Gate designs:a)standard gate at the front of the edge,b)standardgate at the middle of the edge and c)film gate along the whole edge.J.G.Kovcs,B.Sikl/Polymer Testing 30(2011)543547544system.The stationary side of the mould contains only thechangeable cavity inserts;changing these inserts allowsthe parts wall thickness to be varied.In this way,the wallthickness can be chosen as either 1 mm or 2 mm.Top locksguarantee the perfect closing of the two mould halvesassuring a uniform part thickness.The orientation of the material and the positioning ofthe injection location have significant effects on thedeformation.Therefore,three different gate types can beused by changing the gate inserts in the mould(Fig.2.):a standard gate at the front of the edge,a standard gate atthe middle of the edge or a film gate along the whole edge.The sides of the V-top specimen close an angle of 90?,and the deformation caused by the technological or otherparameters can be quantified by changing this angle.Inaddition to unidirectional cavity filling,bidirectional fillingcan be achieved with the application of rotatable inserts(Fig.3.).This feature allows investigation of the influence ofthe weld lines 20,21 at the corners.Warpage is highly influenced by cooling and is verysignificant at corners.The coreof the mould has todissipateheat faster than the cavity;otherwise the internal area ofthe parts corner solidifies slower and causes a sharpeningof the corner itself.To meet the high requirements ofwarpage tests,an efficient cooling system is required(Fig.4.).For the highest control precision,temperaturesensors were installed into both the core and the cavity ofthe mould.Not only the temperature but also the pressurecontrol is important.For this reason,two pressure sensorswere mounted;one at a distance of 5 mm from the gate(PGS;post-gate-sensor)and one at a distance of 5 mmbefore the end of the flow path(EOC;end-of-cavity sensor).With the help of these sensors,the switchover point can becontrolled precisely,which is of fundamental importancefor a stable and consistent cycle.To evaluate the warpage of the V-top specimen,specialimage analysis software was developed.The softwareanalysed scanned images of the side of the specimens andcalculated the closing angle along the edge length from thecorner point(Fig.5.)in 5%steps.3.ExperimentalIn this study,experiments were carried out to prove theefficiency of the novel measuring technique.Neat poly-propylene and polypropylene reinforced with glass fibre ofdifferent weight contents(10,20,30 wt%)were examinedto comprehensively evaluate the new method in a widerange of deformed parts.The matrix(Borealis,HD120MO)and the glass fibreswere mixed on a Brabender Plasticordertwin-screw extruder,and a Brabender pelletizer was usedto produce pellets from the extrudate.From these mate-rials,V-top specimens were injection moulded on anArburg Allrounder 320?C 600250 injection mouldingmachine.The specimens were moulded with a thickness of2 mm using all 3 gate types.The effects of glass fibrecontent,temperature of the moving side of the mould(30,50,70?C)and holding pressure(100,300,500 bar)wereanalysed.All other technological parameters were keptFig.3.V-top specimen with rotatable inserts.Fig.4.The cooling system of the mould.Fig.5.Theoretical image for the closing angle calculation.Fig.6.The influence of injection location on the closing angle as a functionof the relative position along the edge(mould temperature:70?C,fibrecontent:20%,holding pressure:300 bar).J.G.Kovcs,B.Sikl/Polymer Testing 30(2011)543547545constant.The melt temperature was 230?C,the tempera-ture of the stationary side of the mould was 50?C,theholding time was 5 s,the injection rate was 50 cm3/s andthe cooling time was 15 s.The switchover took place whenthe end-of-cavity pressure sensor reached 25 bar.4.Results and discussionThe difference between the cavities was controlled withweightmeasurements,showingthatthecorrelationbetween the weights of the samples from the differentcavities was 0.994.Therefore,it was concluded that spec-imen weight is independent of the cavity,and deformationwas analysed on the outer edge of the specimens producedin the upper cavity.A typical result of the experiments is shown in Fig.6,with the closing angle as a function of the relative edgelength.It can be seen that the measurement is accurate andthestandarddeviationisrelativelysmallateachmeasurement point.The influence of gate type was ana-lysed,and it was shown that the melt entrance point andtype cannot be neglected because they influenced theresults through the orientation of the material(Fig.6).Below,some results will be presented to demonstratethe wide applicability of the method.The experimentalresults showed that the holding pressure had a consider-able effect on the deformation of neat PP(Fig.7.).Close tothe corner the holdingpressurehad a minoreffect,whereasfurther away from the corner the angle increased withincrease in holding pressure.Fibre content decreased warpage independently ofholding pressure(Fig.8.).However,the temperaturedifference between the two mould halves had the biggesteffect on warpage.When higher mould temperatures onthe movable mould side were used,the closing anglebetween the faces of the specimen was decreased asa result of a larger deformation.Analysing the deformationas a function of relative position along the edge,it wasobserved that the closing angle decreased monotonically,with the slope of the angle depending on the temperatureof the moving mould side(Fig.9.).5.ConclusionsIn this paper,a new measurement method was intro-duced for the deformation analysis of injection mouldedplastic parts.The newly introduced V-top specimen allowsinvestigation of the effects of different technologicalparameters and material properties on its deformation.Moreover a novel transformable injection mould wasdesigned and built for the V-top specimens production.The new method was tested and analysed with experi-mental research,in which the effects of gate type andlocation,glassfibrecontentofthematerial,mouldtemperature difference and holding pressure were inves-tigated.Based on the experimental data,it was concludedthat warpage strongly depended on the fibre content andon mould temperatures,but that it was nearly independentof the holding pressure when using PP with glass fibre.These experiments strongly support the new warpageanalysis technique in having a significant advantage overpreviously used warpage measuring methods.AcknowledgementsThis paper was supported by the Jnos Blyai ResearchScholarship of the Hungarian Academy of Sciences.Theauthors would like to thank Arburg Hungaria Ltd.for theinjection moulding machine and Dr.Tung Pham from Bor-ealis Polyolefine GmbH for the material.This work is connected to the scientific program ofthe Development of quality-oriented and harmonizedRDIstrategyandfunctionalmodelatBMEproject.ThisprojectissupportedbytheNewHungaryDevelopmentPlan(Project ID:TMOP-4.2.1/B-09/1/KMR-2010-0002).Fig.7.Corner angle as a function of holding pressure at 5%and 85%positionusing neat PP.Fig.8.The influence of the holding pressure on the closing angle asa function of the fibre content(mould temperature:50?C,relative positionalong the edge:50%).Fig.9.The influence of the moving mould sides temperature on the closingangle as a function of the relative position along the edge(holding pressure:100 bar).J.G.Kovcs,B.Sikl/Polymer Testing 30(2011)543547546References1 J.M.Fischer,Handbook of Moulded Part Shrinkage and Warpage,first ed.Plastics Design Library/William Andrew Inc,Norwich,2003.2 M.Altan,Reducing shrinkage in injection mouldings via the Taguchi,ANOVA 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