Beginning of production and selling of polymer products largely depends on mold manufacturing. The costs of mold manufacturing have significant share in the final price of a product. The best way to improve and rationalize polymer injection molds production process is by doing mold design automation and manufacturing process planning automation. This paper reviews development of a dedicated process planning system for manufacturing of the mold for injection molding, which integrates computer-aided design (CAD), computer-aided process planning (CAPP) and computer-aided manufacturing (CAM) technologies

D. Lukić

J. Tepić

M. Milošević

S. Borojević

V. Todić

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J. TEPI], V. TODI], D. LUKI], M. MILO[EVI], S. BOROJEVI]DEVELOPMENT OF THE COMPUTER-AIDEDPROCESS PLANNING (CAPP) SYSTEM FORPOLYMER INJECTION MOLDS MANUFACTURINGReceived – Prispjelo: 2010-08-11Accepted – Prihva}eno: 2011-02-25Preliminary Note – Prethodno priop}enjeINTRODUCTIONModern organization of manufacturing, featuringnovel design and manufacturing technologies, with em-phasis on flexible automation and extensive applicationof computers. Automation of manufacturing systems isprimarily focused on product design, process planning,production planning and control, as well as manufactur-ing. Design automation is successfully solved usingCAD/CAE systems, manufacturing is automated usingCAM and NC (numerical control) systems, productioncontrol is solved using MRP and ERP (enterprise re-source planning) systems, while the process planning issolved by CAPP systems 1. Due to a relatively lowlevel of CAPP systems, process planning activities rep-resent a significant problem in integration of manufac-turing. To corroborate this claim, Figure 1 shows appli-cation of CIM elements in small and medium-sizedenterprizes (SMEs).CertaintermsinFigure1are:concurrentengineering(CE), automated guided vehicle (AGV), flexible manu-facturing systems (FMS), group technology (GT), mul-timedia (MM), electronic data interchange (EDI), mate-rial requirements planning (MRP).Processplanningismostlybasedontheknow-howandexperienceofengineers.Intensiveuseofcomputershasal-lowedsignificantadvances,resultinginanumberofCAPPsystems. The basic goal of developmental activities inmanufacturing technologies is the integration of all seg-ments of manufacturing and a set up of computer inte-gratedmanufacturing(CIM).CAPPsystemshavekeyroleintheintegrationofdesignandmanufacturing,i.e.theyarea bridge between CAD and CAM systems 3, 4.METALURGIJA 50 (2011) 4, 273-277 273Beginning of production and selling of polymer products largely depends on mold manufacturing. The costs ofmold manufacturing have significant share in the final price of a product. The best way to improve and rationa-lize polymer injection molds production process is by doing mold design automation and manufacturing pro-cess planning automation. This paper reviews development of a dedicated process planning system formanufacturing of the mold for injection molding, which integrates computer-aided design (CAD), compu-ter-aided process planning (CAPP) and computer-aided manufacturing (CAM) technologies.Key words: process plans, CAPP, polymer injection molds, materialsRazvoj CAPP sustava za izradu kalupa za injekcijsko pre{anje polimera. Po~etak proizvodnje i plasmanapolimernih proizvoda u velikoj mjeri ovisi od vremena izrade odgovaraju}eg kalupa, ~iji tro{kovi ~ine veliki udio uukupnoj cjeni proizvoda. Osnovni pravac unapre|enja i racionalizacije procesa proizvodnje kalupa za injekcijskopre{anje polimera usmjeren je na automatizaciju projektiranja kalupa i tehnolo{kih procesa njihove izrade. U raduje prikazan razvoj specijaliziranog programskog sustava za automatizirano projektiranje tehnolo{kih procesa izra-de kalupa za injekcijsko pre{anje polimera, zasnovanog na integraciji CAD, CAPP i CAM aktivnosti.Klju~ne rije~i: tehnolo{ki procesi, CAPP/RPPP (Ra~unalno podr`an proces planiranja), kalupi za injekcijskopre{anje polimera, materijaliISSN 0543-5846METABK 50(4) 273-277 (2011)UDC – UDK 621.824:621.886.6:621.887=111J. Tepi}, V. Todi}, D. Luki}, M. Milo{evi}, Faculty of Technical Sci-ences, University of Novi Sad, Novi Sad, Serbia,S. Borojevi}, Faculty of Mechanical Engineering, University of BanjaLuka, Banja Luka, Bosnia and Herzegovina.Figure 1 Application of CIM elements in SMEs 2This paper shall review the development and applica-tion of a dedicated CAPP system for molds for injectionmoldings of polymers (in further text molds), which iscustom-made for a specific manufacturing environment.DEVELOPMENT OFA INTEGRATED CAPP SYSTEMProduction process of polymer products dependssignificantly on cost of quality, time to market and costto produce appropriate molds.Previously, the design and manufacturing of moldslargelybasedonindividualapproach,withunfavourabletechno-economic effects. It has been noted that the ma-jority of parts, i.e. mold parts, can be standardized,which allows the concept of group technology to be ap-plied on mold design and manufacturing. As a result,mold standardization and batch manufacturing were in-troduced, allowing shorter lead times and delivery, highquality, low manufacturing costs, etc 5, 6.The ever-intensive application of polymer productshas,inthelastdecade,inspiredCAxmanufacturerstode-velop systems which allow improvement of design andmanufacturing of polymer products and molds. A signifi-cant advancement has been made considering the devel-opment of CAD systems dedicated to mold design, aswell as the special CAE systems dedicated to simulationandanalysisofpolymerinjectionmoldings7.Theman-ufacturing process planning domain has become a bottle-neck in the overall system for manufacture of molds.In order to rationalize and advance the manufactureof mold, a model is proposed and the system for auto-mated process planning for mold manufacturing is de-veloped.Thebasicalgorithmicstructureoftheproposedsystem comprizes three distinctive modules accordingto Figure 2 8, 9:– Input data,– Mold design (CAD module) and– Process planning for mold parts manufacturing(CAPP/CAM module).The system relies on available commercial softwaresystems to complete particular stages: the systems for:product design and NC programming, development andmanagement of relational data bases, development ofknowledge base and system integration.The input into this system are polymer products andthe data on particular manufacturing conditions. Withinthe first step, the CAD module can be used for mold de-sign. To support mold design, the system allows selec-tion of standard mold parts, as well as the selection ofthe type of blank and material for particular mold parts.The second CAPP/CAM module is dedicated to auto-mation of process planning for manufacture of moldparts, including the generation of NC part programs.Withintheproposedsystem,processplanningcanbeperformed for:– Typical,i.e.standardmoldparts(thedottedlineinFigure 2 algorithm) for standard machining pro-cesses and operations and/or– Parts of a specific mold, which require particularmachining processes and operations such as en-graving, etc.Forthepurposeofthisreview,prismaticpartsofmoldbe considered, together with the adequate process plansfor their manufacture under particular machining condi-tions.In order to clearly define the processes which takeplace within this dedicated CAPP system according toalgorithmgoveninFigure2,thediagramsofbasicactiv-ities shall be explained in detail by IDEFO methodol-ogy. Figure 3 shows the diagram of basic activitieswithin the system: A1-Mold design, and A2-Processplanning for mold parts manufacturing.Organization and management of data is based on arelational data model, i.e. on a relational database. The274 METALURGIJA 50 (2011) 4, 273-277J. TEPI] et al.: DEVELOPMENT OF THE COMPUTER-AIDED PROCESS PLANNING (CAPP) SYSTEM FOR POLYMER...Figure 2 A diagram to determine reaction forces and mo-ments of the slideintegrated knowledge base (KB) within this system wasdeveloped by combining the data structure stored in thedatabase, and the VBA (Visual Basic for Applications)procedures, using production rules technique. Withinthe data base, there are distinguishable classes or partsof database which allow decision-making 8, 10:– Knowledge base for mold part selection,– Knowledge base for material selection,– Knowledge base for blank selection,– Knowledgebaseformanufacturingfeaturesdeter-mination,– Knowledge base for standard process planning(process sequences, standard processes, operationgroup, standard operations),– Knowledge base for machining resources selec-tion (machine tools, fixtures, modular cuttingtools, measuring devices), and– Knowledge base for selection of machining pa-rameters.In the following paragraphs we will briefly presentthe background for the development of a mold baseparts’ materials selection knowledge database.DEVELOPMENT KNOWLEDGE BASEFOR MOLD PARTS MATERIAL SELECTIONMolds are generally intended mass-production ofpolymerproducts.Thatiswhythemoldsqualityanddu-rability greatly depend on particular mold parts’ mate-rial selection. Mold base consists of a number of piecesof rectangular or circular plate shape, or plate parts.These parts form basic or support structure of molds.Fixed and movable mold parts represents the mostimportantpartsformolds,becausetheyformmoldcavi-ties, which are in direct contact with polymer melt. Thequalityofmoldmanufacturingisdirectlyreflectedtothequality of molding process and to the quality of pro-duced polymer parts.In order to make an optimal selection of steel formolds, it is necessary to consider the following require-ments 5:– The behavior during mold exploitation,– Sufficient resilience,– Consistency of dimensions during exploitation,– Allowed tensile strength and yield strength,– Resistance to the creation of surface cracks,– Resistance to chemical influence, etc.According to the type of steel that are most oftenused for molds, they can be divided into: steel for hard-ening, steel for improvement, steel for nitration, con-ventional high strength tool steels, stainless steel.With respect to the applied polymer material, moldmaterials (steel) can be divided into the followinggroups:– Steel for chemical non aggresive polymers,– Steel for chemical aggresive polymers,– Steel for glassy polymers and polymers with otheradmixtures.Certain type of polymers have agreesive impact onthe mold’s parts, for example: aminoplastics, PVC, andothers. During the polymer injection process, chemicalbyproducts such as amino acids are created. They affectthe surface of mold cavities by creating cracks and ther-efore they have significant influence on the mold partswear. When glassy polymers are used, mold materialsmust have high hardness and high wear resistance, dueto the effects of glassy particles on the surface of moldcavity sprue and runner channels.Table 1 presents a base for the development of aknowledge database for suitable type of steel for themold base parts selection.METALURGIJA 50 (2011) 4, 273-277 275J. TEPI] et al.: DEVELOPMENT OF THE COMPUTER-AIDED PROCESS PLANNING (CAPP) SYSTEM FOR POLYMER...Figure 3 Activity diagram for the dedicated CAPP systemSelected types of materials plays a significant role inmanufacturing process planing, as well as for the selec-tion of appropriate resources and parameters.APPLICATION OF THE DEVELOPEDSOFTWARE SOLUTION -A CASE STUDYThe developed CAPP system shall be verified on astudy case dealing with the manufacture of an fixedmold plate which is a constituent part of the mold of amulti socket body (Figure 4).Based on the input data, the selection of standardmold parts (Figure 5) was performed within the CADmodule at the previous stage, and used as a prerequisitefor the design of the mold assembly, the selection of theblank material for the fixed mold plate (Figure 6).Based on the developed production rules shown intable 1, the contents of the standard process plan, codedTTP11A, for the manufacturing of the fixed mold platefor the selected mold (Figure 7).Foreachmachiningprocessbygivenprogramsystemisabletoobtainthecontentofproces,i.e.specifiedopera-tion and appropirate machining tools, cutting tools, fix-tures, measuring devices and machining parameters. Fortypical machining proces that performed on NC machin-ing systems enables generation a control program, usingparametric programming by Pro/E 8, 9.CONCLUSIONSApplication of general-purpose CAD/CAM/CAEsoftware systems, the systems for database develop-ments, and systems for development of software appli-cations, allows development of software solutions forautomation of design and manufacture.The dedicated software solution developed in thiswork, i.e. the integrated CAPP system, allows automa-tionofasignificantnumberofactivitiesintheprocessof276 METALURGIJA 50 (2011) 4, 273-277J. TEPI] et al.: DEVELOPMENT OF THE COMPUTER-AIDED PROCESS PLANNING (CAPP) SYSTEM FOR POLYMER...Table 1 The distribution of certain types of steel for ma-king mold platesPoly-merma-terialType of steeland deliveryconditionMaterial (steel) codenonaggresiveLow alloy Cr-Mosteel for impro-vement(termallyunthreated)1.7218 ^.4730 25CrMo41.7220 ^.4731 34CrMo41.7225 ^.4732 42CrMo4Low alloy toolsteel (improved)1.2311 40CrMnMo71.2312 ^.4742 40CrMnMoS861.2738 40CrMnNiMo7aggresive High alloyCr-Mo steel(termallyunthreated)1.4110 ^.4770 X55CrMo4High alloy Crstainless steel(normalized)1.2083 ^.4175 X43Cr13Figure 4 A 3D model of the multi socket body and the ap-propriate fixed mold plateFigure 5 Selection standard mold platesFigure 6 Selection of fixed mold plate materialFigure 7 Generated process plan for the manufacturingof the fixed mold platemold design and manufacturing process planning,which contributes to rationalization of activities pro-ceeding the manufacturing process.In the future period, one should expect a significant ad-vancement in the development of a universal platform forCAPP systems and their further integration with variousCIM-related activities, as well as other activities related toproduct lifecycle. This integration means easier sharing ofproduct model data, which is already supported by a num-ber of specifications for product data exchange, amongwhich ISO 10303 (STEP) and ISO 14649 (STEP NC) ismost prominent. Internet technologies are also increas-ingly used as support for integration processes. Globallyavailabledatabasesareusedtosupportconcurrentandcol-laborative engineering, as well as in the development ofdigital factories and E-manufacturing.REFERENCES1 A. H. ElMaraghy, Evolution and Feature Perspectives ofCAPP, CIRP Annals-Manufacturing Technology, 42(1993) 2, 739-751.2 H. B. Marri, A. Gunasekaran, K. Bulent. Implementation ofcomputer-integrated manufacturing in small and mediumenterprises, Industrial and Commercial Training, 35 (2003)4, 151-157.3 C. A. Luttervelt, Research Challenges in CAPP, Internatio-nal Journal of Production Engineering and Computers, 4(2002) 5, 5-18.4 W. D. Li, S. K. Ong, A. Y. Nee, Integrated and Collaborati-ve Product Development Environment, World Scientific,2006.5 M. Na|, Termoplasti~ne mase, prerada postupkom injek-cionog pre{anja, Publicitas, Zagreb, 1974.6 B. Bujani}, I. ^ati}, Grupna tehnologija kod injekcijskogpre{anja, Polimeri, 28 (2007) 1, 40-45.7 J. Hodoli~, I. Matin, M. Stevi}, \. Vukeli}, Development ofIntegrated CAD/CAE System of Mold Design for PlasticsInjectionMolding,MaterialePlastice,46(2009)3,236-242.8 D. Luki}, Razvoj sistema za automatizovano projektovanjetehnolo{kih procesa izrade alata za brizganje plastike, Ma-gistarska teza, Fakultet tehni~kih nauka, Novi Sad, 2007.9 V. Todi}, D. Luki}, M. Stevi}, M. Milo{evi}, IntegratedCAPP System for Plastic Injection Mold Manufacturing,Materiale Plastice, 45 (2008) 4, 381-389.10 M. Kostelac, J. Tepi}, N. ]ular, Justification of the applica-tion of tightening elements in the shaft-hub joint, Metal-lurgy, 50 (2011) 1, 57-61.Note: The responsible translator for English language is J. Bajkin, Fac-ulty of Technical Science, Novi Sad, SerbiaMETALURGIJA 50 (2011) 4, 273-277 277J. TEPI] et al.: DEVELOPMENT OF THE COMPUTER-AIDED PROCESS PLANNING (CAPP) SYSTEM FOR POLYMER...

Development of the computer-aided process planning (CAPP) system for polymer injection molds manufacturing

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