【机械类毕业论文中英文对照文献翻译】塑料注塑模具设计中使用田口方法减少翘曲
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Journal of Materials Processing Technology 182 (2007) 418426The use of Taguchi method in the design of plastic injectionmould for reducing warpageS.H. Tang, Y.J. Tan, S.M. Sapuan, S. Sulaiman, N. Ismail, R. SaminDepartment of Mechanical and Manufacturing Engineering, Universiti Putra Malaysia, 43400 Serdang, Selangor, MalaysiaReceived 3 September 2004; received in revised form 27 July 2006; accepted 10 August 2006AbstractPlastic injection moulding is one of the most important polymer processing operations in the plastic industry today. However, lack of skill inmould making and injection moulding machine control will lead to defective plastic product. Warpage is one type of defect that usually appearsin products with thickness less than 1mm.This project is going to fabricate a mould that produced a thin plate with dimension 120mm50mm1mm. The thin plate will be used forwarpage testing. In mould fabrication, the mould base that purchase will be machined and assembled. After that, the mould is fixed on the injectionmoulding machine. The machine setting should be made to produce the product. Then, the product will be used for testing on the effective factorsin warpage problem by applying the experimental design of Taguchi method.From the results, it shows that the most effective factor on the warpage is melt temperature. The filling time only slightly influenced on thewarpage. The optimum parameters that can minimize the warpage defect are melt temperature (240C), filling time (0.5s), packing pressure (90%)and packing time (0.6s). 2006 Elsevier B.V. All rights reserved.Keywords: Plastic injection mould; Taguchi methods; Experimental design; Warpage1. IntroductionMould making is an important supporting industry becausetheir related products represent more than 70% among the com-ponents in consumer products. The high demand for shorterdesign and manufacturing lead times, good dimensionality andoverall quality, and rapid design changes has become the bottle-necks in mould industries 1. It is a complicated process, andrequired skilled and experienced mould maker.Generally, injection moulding is one of the most importantpolymer processing operations in the plastic industry today.Approximately one-third of all plastics are converted into partsusing injection moulding 2. This is one of the processes thatare greatly preferred in manufacturing industry because it canproduce complex-shape plastic parts with good dimensionalaccuracy and very short cycle times 3. Typical examples arecasings and housings of the products such as computer monitorand mobile telephone, which have a thin shell feature. TheseCorresponding author.E-mail address: .my (S.H. Tang).products tend to become lighter, thinner and smaller. Hence, theinternal components of products have to be packed into hous-ing, which has smaller volume. One way to increase the spaceof housing parts is to reduce the wall thickness. However, theinjection moulding operation becomes more difficult as the wallthickness of plastic parts becomes thinner 4. This is becausethe significant warpage defect will be appeared. To reduce thissignificant defect, testing procedure regarding to the effectivefactors is required.A thin plate with dimension 120mm50mm and 1mmthickness will be produced. It is use for testing on the effec-tive factors to minimize the warpage defect. Firstly, fabricatingthe plastic injection mould is needed. After that, the mould isgoingtobeassembledontheinjectionmouldingmachine.Whenthe thin plates have been produced, they will be used for test-ing on the effective factors in warpage problem by applying theexperimental design of Taguchi method.2. PreparationIn fabricating the mould, some preparations are needed.The capability of the machine that are available in faculty are0924-0136/$ see front matter 2006 Elsevier B.V. All rights reserved.doi:10.1016/j.jmatprotec.2006.08.025S.H. Tang et al. / Journal of Materials Processing Technology 182 (2007) 418426419investigated. The machines that required in fabricating themould are drilling machine, milling machine and grindingmachine.Theplasticinjectionmouldingmachineisalsoneededfor producing the product. The machine that has been usedis BOY 22D. Besides that, it is also required to search andpurchase the mould base, which can fit the injection mouldingmachine. Carbon steel AISI 1050 had been selected as materialfor the mould base. Since some components such as ejector pin,locating ring, sprue bush, water junctions and springs are notincluded in the mould base, these components are purchasedindependently. The plastic material that has been used isABS.3. Mould designTherearefourdesignconceptsthatcanbeusedinthisproject.The description of these design concepts is as follows:(a) Three-plate mouldHaving two parting lines with singlecavity.(b) Two-plate mouldHaving one parting line with single cav-ity without gating system.(c) Two-platemouldHavingonepartinglinewithdoublecav-ities with gating system and with ejector pin at the cavities.(d) Two-plate mouldHaving one parting line with doublecavities with gating system and without ejector pin at thecavities.Since this project is limited in budget, the type of mouldbase that has been chosen is two plate mould instead of threeplate mould. Among the design concepts for two plate mould,the concept d has been chosen. This is because concept bis non-productive while concept c may damage the productduring ejection.Generally, two plate mould consist of eight plates and therearetheirstandarddimensions,respectively.Themouldbasethathas been chosen must base on the specification of the injectionmouldingmachinethatwillbeused.Inthisproject,thestandardmouldbasewith250mm250mmhasbeenusedanditsplatesdimension are shown in Table 1.AmongtheseplatesthatareshowninTable1,onlythecavityplateandcoreplateareneedtobedesigned.Theotherplatesareonlybaseonthespecificationoftheinjectionmouldingmachineand the components dimension.Table 1Mould plates dimensionsPlateDimensionwidthheightthickness (mm)Top clamping plate125025025Cavity plate120025040Core plate120025040Side plate23725070Ejector-retainer plate112025015Ejector plate112025020Bottom clamping plate125025025Fig. 1. Air vent design.There are relative between the product design and themould design. Since this project is determined the effectivefactor that can minimize the warpage defect for a thin shellfeature, the product that has been designed is a plate with120mm50mm1mm in dimension.For the mould base, the cavity that can produce the productis designed on the core plate. Since there is enough space at thecore plate, two cavities with gating system has been designed.This design is without ejector pin at the cavity part and onlyused sprue puller to eject the product. This will avoid productdamage.Air vent design is important because its function is to releasethe air inside the cavity when the mould is closed. Short shotwill happen if air is trapped inside the mould. Fig. 1 shows thedesign of air vent in this project.Cooling system is another consideration in design stage. Itis used to solidify the plastic product before eject out from themould. Figs. 2 and 3 show the design of cooling channel forcavity plate and core plate, respectively, in this project.The product design in this project is only a simple thin plate.Hence, the mould can be fabricated by using milling machine,drilling machine and grinding machine.Fig. 2. Configuration of cooling channel for cavity plate.420S.H. Tang et al. / Journal of Materials Processing Technology 182 (2007) 418426Fig. 3. Configuration of cooling channel for core plate.4. Mould fabricationTherearesomepartsinthemouldthatneedtobemachined.Itinvolvedhighpreciseandaccuracyprocess.Hence,itisrequiredskilled mould maker. Following is the machining process forevery part of the mould.4.1. Top clamping platePart 1: Ream through hole with 16mm diameter (drillingmachine)Operation descriptionsToolsStep 1Marking the pointHeight gaugeStep 2Clamping the plate on the machine tableStep 3Centering at the marking pointCenter drillStep 4Drilling through hole15.5 drillStep 5Reaming the hole16 reamerTool, high speed steel; spindle speed, 330rpm.Part 2: Tap M6 holes (drilling machine)Operation descriptionsToolsStep 1Marking the pointHeight gaugeStep 2Clamping the plate on the machine tableStep 3Centering at the marking pointCenter drillStep 4Drilling 2 holes with 12mm depth5 drillStep 5Tapping the holesM6 tapperTool, high speed steel; spindle speed, 1000rpm.Part 3: Enlarge hole to 40mm diameter with 14.8mm depth(milling machine)Operation descriptionsToolsStep 1Marking 35 and 40 circlesCompassStep 2Clamping the plate on the machine tableStep 3Milling the area at 35 circle with 14.8mm depth10 endmillStep 4Boring until 40 circle with 14.8mm depthBorebitTool, high speed steel; spindle speed, 820rpm; depth of cut, 2mm for roughingand 0.8mm for finishing.Fig. 4 shows the parts of the top clamping plate that need tobe machined. Note that the first step in Part 1, Part 2 and Part 3Fig. 4. Parts of the top clamping plate that need to machine.which are marking point and marking circle is done at the sametime before proceed to next step.4.2. Cavity platePart 1: Ream through hole with 16mm diameter (drillingmachine)Operation descriptionsToolsStep 1Marking the pointHeight gaugeStep 2Clamping the plate on the machine tableStep 3Centering at the marking pointCenter drillStep 4Drilling through hole15.5 drillStep 5Reaming the hole16 reamerTool, high speed steel; spindle speed, 330rpm.Part 2: Drill through holes with 8mm diameter (drillingmachine)Operation descriptionsToolsStep 1Marking the pointHeight gaugeStep 2Clamping the plate on the machine tableStep 3Centering at the marking pointCenter drillStep 4Drilling 2 holes until half width of the plate8 drillStep 5Turn the plate to opposite sideStep 6Clamping the plate on the machine tableStep 7Centering at the marking pointCenter drillStep 8Drilling 2 through holes8 drillTool, high speed steel; spindle speed, 640rpm.Part 3: Tap 1/4?holes (drilling machine)Operation descriptionsToolsStep 1Clamping the plate on the machine tableStep 2Drilling 2 holes with 15mm depth11 drillStep 3Tapping the holes1/4?tapperStep 4Turn the plate to opposite sideStep 5Clamping the plate on the machine tableStep 6Drilling another 2 holes with 15mm depth11 drillStep 7Tapping the holes1/4?tapperTool, high speed steel; spindle speed, 460rpm.S.H. Tang et al. / Journal of Materials Processing Technology 182 (2007) 418426421Fig. 5. Parts of the cavity plate that need to machine.Fig. 5 shows the parts of the cavity plate that need to bemachined. Note that the first step in Part 1 and Part 2 which ismarking point is done at the same time before proceed to nextstep.4.3. Core platePart 1: Drill through holes with 8mm diameter (drillingmachine)Operation descriptionsToolsStep 1Marking the pointHeight gaugeStep 2Clamping the plate on the machine tableStep 3Centering at the marking pointCenter drillStep 4Drilling 2 holes until half width of the plate8 drillStep 5Turn the plate to opposite sideStep 6Clamping the plate on the machine tableStep 7Centering at the marking pointCenter drillStep 8Drilling 2 through holes8 drillTool, high speed steel; spindle speed, 640rpm.Part 2: Tap 1/4?holes (drilling machine)Operation descriptionsToolsStep 1Clamping the plate on the machine tableStep 2Drilling 2 holes with 15mm depth11 drillStep 3Tapping the holes1/4?tapperStep 4Turn the plate to opposite sideStep 5Clamping the plate on the machine tableStep 6Drilling another 2 holes with 15mm depth11 drillStep 7Tapping the holes1/4?tapperTool, high speed steel; spindle speed, 460rpm.Part 3: Enlarge holes to 32mm diameter with 10mm depth(milling machine)Operation descriptionsToolsStep 1Marking four 28 and 32 circlesCompassStep 2Clamping the plate on the machine tableStep 3Milling the area at 28 circle with 10mm depth10 endmillStep 4Boring until 32 circle with 10mm depthBorebitTool, high speed steel; spindle speed, 820rpm; depth of cut, 3mm for roughingand 1mm for finishing.Part 4: Create the cavity of the product (milling machine)Operation descriptionsToolsStep 1Marking the area of cavityHeight gaugeStep 2Clamping the plate on the machine tableStep 3Milling two 120mm50mm1mm cavity3 endmillStep 4Milling taper at boundary of cavity8taper millStep 5Milling the runnerR3 ball nose millTool, high speed steel; spindle speed, 2700rpm; depth of cut, 0.5mm per cut.Part 5: Ream through hole with 6mm diameter (drillingmachine)Operation descriptionsToolsStep 1Marking the pointHeight gaugeStep 2Clamping the plate on the machine tableStep 3Centering at the marking pointCenter drillStep 4Drilling through hole5.8 drillStep 5Reaming the hole6 reamerTool, high speed steel; spindle speed, 880rpm.Fig. 6 shows the parts of the core plate that need to bemachined. Note that the first step in Part 1, Part 3, Part 4 andPart 5 which are marking point and marking circle is done atthe same time before proceed to next step. Grinding machine isused for produced air vent.Fig. 6. Parts of the core plate that need to machine.422S.H. Tang et al. / Journal of Materials Processing Technology 182 (2007) 418426Fig. 7. Parts of the ejector plate that need to machine.4.4. Ejector platePart 1: Ream through hole with 6mm diameter, drill coun-terborewith11mmdiameterand6mmdepth(drillingmachine)Operation descriptionsToolsStep 1Marking the pointHeight gaugeStep 2Clamping the plate on the machine tableStep 3Centering at the marking pointCenter drillStep 4Drilling through hole5.8 drillStep 5Drilling counterbore with 6mm depth11 drillStep 6Reaming the through hole6 reamerTool, high speed steel; spindle speed, 880rpm/460rpm.Fig. 7 shows the parts of the ejector plate that need to bemachined.4.5. Bottom clamping platePart 1: Enlarge through holes to 55mm diameter (millingmachine)Operation descriptionsToolsStep 1Marking 50 and 55 circlesCompassStep 2Clamping the plate on the machine tableStep 3Milling through hole at the area 50 circle10 endmillStep 4Boring until 55 circleBorebitTool, high speed steel; spindle speed, 820rpm; depth of cut, 3mm per cut.Fig. 8 shows the parts of the bottom clamping plate that needto be machined.After finishing the machining process, all the mould platesare assembled together. Each mould plates had its datum planeat one corner of the plate, respectively. All the surfaces of theFig. 8. Parts of the bottom clamping plate that need to machine.plate at datum plane are perpendicular to each other. Duringassembled the mould, all the plates must be aligned refer to thedatum plane. In other words, all the datum plane of the platesmust be in the same corner.After the mould has been finished to assemble, the bolt andthehookareusedtohangupthemouldtotheinjectionmouldingmachine area. It is installed one by one. The mould is fixed intothe machine by the bolt tightly to prevent it from sliding downfrom the machine.5. Mould testing and modificationWhen the mould has been tried run, most of the product thatproduced has short shot defect. The plastic material could notreach the corner of the product. This might cause by insufficientventingandtheairtrappedintheclosedmould.Hence,themod-ificationhasbeenmadeonthemouldwhichisaddedtheventingtothemouldatthecornerofthecavity.Finally,thismodificationis produced the product without short shot defect successfully.6. Process of experiment designTo determine the best set of parameter among the effectivefactors by reducing the number of experiments, the Taguchimethod has been chosen. Hence, selection of the factors thatwill affect warpage, selection of the factor levels and selectionof orthogonal array (OA) based on Taguchi method is needed.The best set of parameter will be produced a minimum warpageproduct.6.1. Selection of the factorsAccording to the journal, there are several possible factorsthat can affect warpage defect at the thin plate which are fillingtime, mould temperature, gate dimensions, melt temperature,packing pressure and packing time 4. Since the design of themould is different from the journal, so the gate dimension factoris eliminated. The mould temperature factor is also eliminatedS.H. Tang et al. / Journal of Materials Processing Technology 182 (2007) 418426423Table 2The parameter for three levels of selected factorsFactorsLevel 1Level 2Level 3Melt temperature, A (C)240265290Filling time, B (s)Packing pressure, C (%)607590Packing time, D (s)Table 3L9 orthogonal arrayTrial no.Column no.ABCD111112122231333421235223162312731328321393321because the temperature is difficult to control due to the ambi-ent temperature. Finally, four factors have been selected. Thesefactors are melt temperature, filling time, packing pressure andpacking time.6.2. Selection of the factor levelsThere are three levels of each factors will be conducted usingTaguchimethod.Thisisbecauseiftheselectedfactorhassignif-icant effect on the product, we may be able to choose among thelow, middle and high values instead of just having only low andhigh values to be selected. Each level parameter of the selectedfactorthatsuggestedaccordingtothejournalisshowninTable2.6.3. Selection of orthogonal array (OA)Fromthenumberoffactorsandlevelsthathavebeenselectedpreviously, the L9 orthogonal array will be used. The L9 is cho-sen as an OA because it is suitable for four factors with threelevels. The L9 orthogonal array is shown in Table 3.7. Product testing procedureThe testing process is started by keying all the combina-tion parameters for the effective factors into injection mouldingmachine as shown in Table 4. There are nine experiments beendone and each experiment has different combination.After that, the flashing on the product is removed and theproduct is cut out from the runner. The thickness of the productthat free with flashing and the runner is measured at 10 differentplaces by using micrometer. The readings and their average arerecorded. To measure the warpage of the plate, the dial gaugeandthegraniteblockhavebeenused.Theproceduresofwarpagemeasurement are shown below:Table 4The combination parameters for the effective factorsTrial no.Melt temperature,A (C)Fillingtime, B (s)Packingpressure, C (%)Packingtime, D (s)12400.1600.622400.3750.832400.5901.042650.1751.052650.3900.662650.5600.872900.1900.882900.3601.092900.5750.6Fig. 9. Definition for symbols h, taand z.(a) The plate is placed on the flat surface at the granite block.(b) The dial gauge is moved down until its stylus is touched bythe flat surface of the granite block and the dial gauge is setto zero.(c) Theplateismovedaroundbelowthestylusofthedialgauge.(d) Themaximumheightoftheplateiscalculatedfromthescalein dial gauge and the reading is recorded.(e) The procedures are repeated for other plate.After getting all the readings, the deflection, z, which is thewarpage of the plate, is calculated from formula: hta=z. Thedefinition for symbols h, taand z are illustrated in Fig. 9.Next, the deflection of the plates that obtained in experimentis used to calculate the signal-to-noise (S/N) ratio. From theS/N ratio, the best set of combination parameter can be deter-mined. The collected data can also be analyzed using Analysisof Variance (ANOVA) method. From this method, the percent-age contribution has been calculated to determine which of thefactor will affect the warpage significantly.8. Results and discussionThe machining processes that have been done are such asdrilling, milling and tapping. The sequence for machining pro-cessesisimportanttogetagoodqualityofworkandalsosavingthe machining time.In machining process, there are some steps that should behighlight and pay attention. For drilling process, especially forcoolingchannel,thedrillingmachinethathasbeenusedisradialdrilling machine instead of vertical drill press. This is becausethe spindle speed for radial drilling machine is controlled bygear while the vertical drill press is used belt. Thus, the radialdrillingmachinecanproducehigherdrillingtorqueascomparedto the vertical drill press.During drilling the cooling channel, it spends much timebecause the hole that drilled is quite big and depth. It required424S.H. Tang et al. / Journal of Materials Processing Technology 182 (2007) 418426machining carefully because the drill can be broken easily oncethe chips are stacked inside the drilled hole. Hence, the chipsmust be removed from time to time. An alternative is to drillthe hole in two steps. First, drill a smaller diameter hole at thecenter.Afterthat,drilltherequireddiameterholeattheprevioushole.Thiswillreducedthedrillingtorqueandhencereducedtherisk for tool break.Before drilling the hole, the centering operation is impor-tant and cannot be neglected. This operation will guide the tooldrilled at right position and also prevent the tool from bending.During drilling operation, the force that applied in pressing thedrill cannot be too much. This will bend the tool and lead tothe drilled holes become not straight. Besides that, coolant isrequired during the drilling process. This will reduce the tem-perature of the tool which is caused by friction.There are some tapping operation at cooling channel and thetop clamping plate. Before tapping the holes, the tap needs toimmerse in the lubricant. This will reduce the friction duringtapping operation. Tapping each hole completely required threedifferenttypesoftapsbutsameindiameter.Thefirsttapthatusedismoretaperattheend.Itisusedtomakethethreadbyapplyingminimum torque. If feeling very tight during tapping the holes,the chips should be removed. Continue to tap by applying moretorquemightbreakthetap.Thesecondtapistodeepenthethreadwhile the last tap is for finishing. During tapping, the first tap isimportant and must be straight because the thread that createswill gives the next two taps as guidance.After the product has been produced, it will be firstly mea-sured for its thickness and maximum height by using dial gaugeonthegraniteblock.Then,theaveragethickness,deflectionandaveragedeflectionwillbecalculated.Theexperimentsthathavebeen done are based on Table 3.In determination of S/N ratio, the smaller the better qualitycharacteristic has been selected.For smaller the better,S/N= 10 log(MSD)whereMSD =1nn?i=1y2iwhere MSD is the mean square deviation, y the observation ordata and n is the number of tests in a trial.Table 6The response table of S/N ratioMelttemperature (A)Fillingtime (B)Packingpressure (C)Packingtime (D)Level 121.55719.00017.26021.017Level 217.73317.50718.66717.033Level 316.31319.09719.67717.553Difference5.2441.5902.4173.984The results that calculated for average deflection and S/Nratio are summarized in Table 5.From the data in Table 5, the average S/N ratio for responsetable can be determined. The example of calculations is shownbelow and the result can be summarized as shown in Table 6.For factor packing pressure,Level1 =23.23 + 15.52 + 13.033= 17.260Level2 =19.16 + 17.35 + 19.493= 18.667Level3 =22.28 + 20.33 + 16.423= 19.677Difference= highestvalue lowestvalue= 19.677 17.260= 2.417Based on the data from Table 6, the S/N response diagramcan be constructed as shown in Figs. 1013.Fig. 10. S/N response for melt temperature.Table 5Summarize of the experimental resultTrial no.Control factorAverage deflection, za(mm)S/NMelt temperature (C)Filling time (s)Packing pressure (%)Packing time (s)12400.1600.60.067923.2322400.3750.80.106619.1632400.5901.00.073522.2842650.1751.00.130117.3552650.3900.60.094120.3362650.5600.80.161315.5272900.1900.80.148616.4282900.3601.00.213313.0392900.5750.60.104919.49S.H. Tang et al. / Journal of Materials Processing Technology 182 (2007) 418426425Fig. 11. S/N response for filling time.Fig. 12. S/N response for packing pressure.Fig. 13. S/N response for packing time.FromtheS/NratioresponseinTable6,thebestsetofcombi-nation parameter can be determined by selecting the level withthe highest value of each factor. Thus, the result that obtained isA1, B3, C3and D1. This result can also be observed from S/Nresponse diagram in Figs. 1013. Besides that, the differencebetween levels in Table 6 also shows which factor is more sig-nificant. The most significant factor that affecting warpage aremelttemperatureandpackingtimefollowedbypackingpressureand filling time. The comparative between experimental resultswith simulation result are shown in Table 7.From the table, the results that get by experiment are notsame with the simulation result except packing time. This isbecausetheproductdesignandthemouldconfigurationarequitedifferentduetothecostandthemachinecapability.Besidesthat,the contact type apparatus for warpage measurement also couldTable 7Comparative between experimental result and simulation resultExperimental resultSimulation resultMelt temperature, A (C)240290Filling time, B (s)0.50.3Packing pressure, C (%)9060Packing time, D (s)0.60.6Table 8ANOVA tableSourcefSVFP (%)Melt temperature, A28.1541034.07710347.30Filling time, B21.1231030.5621036.51Packing pressure, C22.9751031.48810317.26Packing time, D24.9871032.49410328.93Pooled error000Total817.240103100affect the result. This is because the stylus at dial gauge mightdistort the product to some degree. The parameter for packingtime is same with simulation result because packing phase isonlyusedforcompensatetheshrinkage.Theproductisnotmuchdifferent in dimension once the same material has been used.The data in Table 5 also analyzed using ANOVA. The rel-ative percentage contribution among the factors is determinedbycomparingtheirrelativevariance.TheANOVAwillcomputethequantitiessuchasdegreesoffreedom,sumsofsquares,vari-ance, F-ratio, pure sum of square and percentage contribution.The example calculations of these quantities are shown belowand the results can be summarized in Table 8.8.1. Degree of freedom (f)Total degree of freedom,fT= N 1= 9 1 = 8where N is the total number of result.For factor A,fA= kA 1= 3 1 = 2where kAis the number of level for factor A.For error,fe= fT fA fB fC fD= 8 2 2 2 2 = 0.8.2. Sum of squares (S)Total sum of squares,ST=(z2a1+z2a2+z2a8+z2a9)(za1+za2+za8+ za9)2N= (0.06792+0.10492) (0.0679 + + 0.1049)29= 0.1518 0.1345= 17.240 103426S.H. Tang et al. / Journal of Materials Processing Technology 182 (2007) 418426For factor A,SA=?A1?2kA+?A2?2kA+?A3?2kA(za1+ za2+ + za8+ za9)2N=(0.0679 + 0.1066 + 0.0735)23+(0.1301 + 0.094
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