An innovative manufacturing process

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An innovative manufacturing process for bamboo injection

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JournaloftheChineseInstituteofIndustrialEngineersVol.29,No.7,October2012,454465AninnovativemanufacturingprocessforbambooinjectionmoldingbyusingTRIZandTaguchimethodMu-TsaiChang*andChi-HaoYehDepartmentofIndustrialEngineeringandManagement,NationalTaipeiUniversityofTechnology,No.1,Sec.3,Chung-HsiaoEastRoad,Taipei,Taiwan,ROC(ReceivedFebruary2012;revisedJuly2012;acceptedAugust2012)Theappearanceof3C(computer,communication,consumerelectronic)electronicproductshasbeenconsideredas acritical attributetoattract consumers inthepast decade. Moreover, 3Celectronicenterpriseswithownbrandsaretryinghardtomeettherequirementssuchasuser-friendlyinterfaceandeco-environmental materials for increasingthe revenue andmarket share. Bamboohadbeenknown as a flexible and green raw-material worldwide for many years. However, there are no bamboo-made applications in any 3Celectronic products due to its manufacturing process to achievesatisfactory specifications. The innovative manufacturing process of bamboo injection molding on theappearanceof a 3C product suffered from a crucial quality issue,that is, bamboo deformation due tothedifferencebetweenshrinkageof plasticanditsinherent material characteristics. Theconcept issimilartoIMR(in-molddecorationbyroller)process. Theobjectiveofthisarticleistoproposeaninnovativeandrobustbambooinjectionmoldingprocessbyusingskillssuchasmeasurementsystemanalysis, the Taguchi method, process capability index, and TRIZ. In this study, the detailedexperimental process andsatisfactoryresult are demonstratedandgiven. The exploitedapproachconcerningbamboois avaluableoutcomeandreference for further advancedimplementations inelectricalindustryandothers.Keywords: bamboo injectionmolding;measurementsystemanalysis;Taguchi method;TRIZ;processcapabilityindex1. IntroductionConsumers are attracted by the functionalities,appearance,andpriceofa3C(computer,commu-nication, consumer electronic) electronic product.However, existingmanufacturingtechniques suchas electroplating andspray painting for anelec-tronic products appearance produce significantandnegativeimpactstoenvironment. 3Ccompa-nies with own brand need to provide moreeco-environment protection while using newfinish-machiningmethods [7]. Bamboohas manyadvantagessuchaseasytorecycle,easytodecom-pose,andgoodperformanceinphysicalattributes.It is a suitable material to produce home-livingproducts. AsusTek, oneof brandcompanies, hasbeen dedicated in developing innovativemanufacturing process and designed laptopsappearance by using bamboo as main material.Thisistheveryfirstbambooskinontolaptopandisfamousworldwide(Figure1).Inrecent years, in-moldinjectionhas beenapopular manufacturingprocess inlaptopappear-ance. AsusTekbegantoexplorein-moldinjectionmolding by using bamboo and give curved anddouble-sided arcs appearance. However, qualityissuessufferfrombreaking, blisters, wrinkles, anddeformationonbambooskin(Figure2).Themostcritical issue is the deformationdue todifferentshrinkageratiosforplasticandbamboo. Sincein-mold injection molding by using bamboo is the firstattempt all over the world, there is no existingempirical rule or data to solve the difficult problem.In this study, an innovative and robust manufactur-ing approach is exploited to solve the bamboodeformation occurring in in-mold injectionmolding.The approach is executed by traditional quality-relatedskills suchas Taguchis method, MSAbygauge repeatability and reproducibility (GRR),process capability index (PCI) by Cpk, t-test byone-samplet-test, andindependent samplest-test.In addition, TRIZ known as an innovative thinkingmethodology is utilized to solve problems neverbeenmet. Althoughthe traditional quality-assur-ancetechniques utilizedarenot newlydeveloped,however, the synergy of traditional skills and TRIZprovides a profitable quality level in such a difficultmanufacturingprocess.*Correspondingauthor.Email:Arthur_chang@asus.comISSN10170669print/ISSN21517606online2012ChineseInstituteofIndustrialEngineershttp://dx.doi.org/10.1080/10170669.2012.727477http://www.tandfonline.com2. An innovative and robust manufacturingapproachThemost critical issueis thedeformationduetodifferent shrinkage ratios between plastic andbamboo(thedesiredspecificationfordeformationis 03 mm, mean14.3 mm, standarddeviation1.04). This article proposes an innovative androbust manufacturing approach to solve thisunwanteddeformation. Theproblem-solvingpro-cess is suggested in four steps and is shown inFigure3. Thedetailedexperiment arrangement isexplainedinthefollowingsections.2.1 MSAexperimentTheMSAis processedat stageA inFigure3.The measure systemis composed by measuringinstrument, operator, and operational environ-ment. If the measurement variationis toolarge,themeasurementdatamaynotbeappropriateforfurther analysis [1]. MSAmethodology includesevaluation bias, evaluation stability, evaluationdiscrimination, GRR analysis, Kappa analysis,etc. The GRRanalysis using continuous data isexecutedtomeasure repeatability (the variabilitybetweentheoperatorsandequipment) andrepro-ducibility(thevariabilityamongtheoperators)[6].Four basic GRR are defined in terms of %contribution,%studyvariation,%tolerance,andthe number of distinct category. The field isemphaticallyinprecisionofmeasuringinstrument,which holds tolerance ratio [1]. Therefore, %tolerance is chosen to carry on MSA in thisstudy, that is, the formulae are as shown inEquation(1).%Tol PT 6x

2Measurement SystemqUSL LSL, 1where%Tol isthepercentageoftolerance, Ptheprecision, T the tolerance, USL the upper specifica-tionlimit, andLSLthelower specificationlimit.The operational requirements are at least twooperatorsandsixanalysestocarryout twotimesmeasurement [1]. The criteria for determining if theprocessiscapableare: GRR510%isacceptable(PASS), 10% GRR530%is a conditionalacceptance, and GRR30%is not acceptable(NG) based on practical experience for 3Celectronicproducts.As mentionedearlier, thedeformationis veri-fiedbyGRRprocess.TheMSAexperimentneedstwolaboratoryoperatorsand10injectedbambooproducts. Each operator measures his (her) injectedbamboo products for three cycle times. If the GRRresult is NG, the quality assurance department willask component suppliers to provide correctiveactionreport(CAR)forfacilitatingthemeasuringimprovement. The measurement systemis evalu-atedagainandrepeatedlycarriedout until GRRresult is acceptable (PASS) or a conditionalacceptance.2.2 TRIZexperimentThe TRIZ method is applied at stage B shown inFigure 3. TRIZwas inventedanddeveloped byRussian Genrich Altshuller. Genrich Altshuller hadfound a variety of different engineering systems andtechnologies sharing common evolution, whichhaveguidedpeopletoavoidmanyfruitless trailsanderrorsin1950s.TRIZhadbeenprovedtobeawell-structuredand innovative way of problem solving in technicaland non-technical areas [9]. Many well-knownimprovement methods like the Six Sigma, QFD,the Taguchi method, and DFM/Ahave recom-mended TRIZ as a valuable complement forinnovation,nomatterintechnology,management,business strategy, and creativity [8]. Therefore,TRIZis a feasible innovative theory in solvingmany contradictions in engineering and technol-ogy. Manypractical TRIZ-basedusages inengi-neeringareacanbereviewed[11]. TRIZincludesFigure 2. Abnormalities at bamboos appearance byusing in-mold injection molding process: (a) breaking, (b)blisters,(c)wrinkles,and(d)deformation.Figure1. AsusU6VBamboonotebook.JournaloftheChineseInstituteofIndustrialEngineers 455contradiction analysis, idle resources utilization,increasing the ideality of final result, prediction fortheevolutionof bothproblems andsolutions, 39engineeringparameters, 40TRIZinnovativeprin-ciples, and contradiction matrix [8]. In addition, 40TRIZ innovative principles have been confirmed tobeshortcutstoideal final result evenwithout theanalysisof contradictionsandresource. Theycanbeusedasindependenttoolstoobtaininnovativeorcreativeideasforresolvingconflicts.FortyTRIZinnovative principles were devel-oped by Altshuller in the early 1970s. In mostsituations, one principle will give a concept forinitial solution, but several iterations may beneeded to achieve a feasible solution. The 40TRIZinnovative principles are listedinTable 1.One can find the detailed description of eachinnovative principle easily on website or in aTRIZ-relatedbook.A technical contradiction (trade-off) means thatwhenonefeaturegetsbetter, anotherfeaturewillgetworsesimultaneously.Altshullerhadproposed39engineeringparameterstoincludeall engineer-ing features (Table 2). He also developed andproposedthecorresponding39 39contradictionmatrixtabletoindicatethesuggestedmoreeffec-tive TRIZinnovative principles for solving eachpairofconflictingengineeringparameters.Thatis,cuesforfindinginnovativeprinciplesforeachpairof trade-offs are summarizedinthe 39 39con-tradictionmatrixtable.Mannet al. [5] have adjusted39 engineeringparametersto48onestomeettherequirementofrecent and advanced technology. They created48 48 contradiction matrix referred by theirexperienceandAltshullersmatrix. However, Yeh[12] hadintegratedtheoriginal 39 39contradic-tion matrix by Altshuller and 48 48 contradictionmatrix by Mann et al. into a new 39 39contradictionmatrix. The new39 39contra-diction matrix contains more suggested innovativeprinciples, but still 39parameters remain. Inthisstudy, new 39 39 contradiction matrix isimplementedtofindmorecuesforsolving difficultproblems.For instance, breaking-resistance of a smartphone is a critical specification in dropping test formanufacturers. To strengthen a mobile phone fromFigure3. Theflowchartofexperimentalprocedure.Table 1. 40 TRIZinnovativeprinciples.1 Segmentation 15 Dynamicparts 28 Mechanicalinteractionsubstitution2 Separation 16 Partialorexcessiveactions 29 Pneumaticsandhydraulics3 Localquality 17 Dimensionalitychange 30 Flexibleshellsandthinfilms4 Symmetrychange 18 Mechanicalvibration 31 Porousmaterials5 Merge 19 Periodicaction 32 Opticalpropertychanges6 Multi-functionality 20 Continuityofusefulaction 33 Hom