Variant Computer Aided Process Planning System for Rotational Parts

74Joumal of Donghua University (Eng. Ed.) Vol. 22, No.2 (2005)Variant Computer Aided Process Planning System for Rotational PartsAHMED Hassan, YAO Zhen- qiang(姚振强)，CAI Jian-guo(蔡建国)School of Mechanical Engineering, Shanghai Jiaotong University, Shanghai 200030, Ching,The amount of material must be removed away to producebut the processes themselves consume a great deal of materialthe final product should minimizc, excess stock will increaseas machining chips, more of these chips are recycled asnot oaly the material cost, but also processing cost, fixturescrap, but there is a severe economic penatyt2]. To minimizecost, tooling cast, and increases machine cycle times.machining requirements, a suitable blank shape and size asNoticing in recent years that the world is running out ofclose as possible to those of the part required have to bemineral resources, and the price of engineering materialssclected, this selection depends upon the part featurewill continually rise in the future, the percentage of the costcharacteristics, material, and type of production. Severalof manufactured part that is due to the cost of materials iscompetitive primary manufacturing processes are availablealso rising. This paper proposed a variant CAPP system forwith a large overlap on their capabilities, manufacturingrotational parts based on the concept of group technology,costs, overheads and the material utilization factor can bethis system accepts part features characteristics codeused to optimize the selection of a suitable process required.number as an input and provides operation details formanufacturing route with the suitable primary processesLiterature Reviewrequired to produce the blank work piece as an output.Keywords : CAPP, Blank work piece , MachiningA number of systems for primary process selection had beendeveloped. Most of these are simple proprietary guide toaid a customer in making a selection from a company'sIntroductionline.In order to put the selection of primary processes intoProcess planning is a function that establishes thea manageable form, Niebels7 used an analytical techniquemachining processes, machines and tooling capable ofby classified the parameters characterize capabilities ofperforming these processes, and machining parameters toprimary processes to attributes, the relationship betweenbe used to convert a piece part from its initial form to aeach possible basic process and parameters was tabulated inproxletermined shape,出s per the engineering drawing. Approachesa matrices form, based on cost, acepted processcs wereused for computer aided process planning (CAPP) can beoptimized. But this system fails to account for thclassified as Variant, Generative or hybrid Semi generative. Ininterrelationship between material and process selection.the variant approach, a process plan for new componentTo overcome this problem the MAPS-1 program41] wascreated by retrieving a standard plan that has been stored ininteractively generates a twelve digit classification code tothe database, using group technology concepts likeexpress important characteristics of the part; each digitclassification and coding. In the generative approach, therepresents a particular characteristic after eliminatingnew process plan generated by synthesizing the componentincompatible processes， a program indicates how manydata with the information from a manufacturing databasecombinations remain and list of usual and unusual practiceand decision rules. Recent literature survey demonstratesprocess, this classification and coding system used is alreadythat, current research efforts continue to focus on variantsolved the above-mentioned point but the problem is thatas well as generative and hybrid systems.this system is not for general use. Charles Emerson[5]The predominant manufacturing processes are machiningdeveloped a ( ACAPS) system， used of GT concept toprocesses, in which cutting tool generates a necessary shapeinteractively assign a code number of 21-digit to a part; thisby removing the successive chips of material. Now a dayssystem includes a module totally built around the techniquemetal cutting machine-tools, which they can producethat developed by Niebef's. A code used performs fullpractically any shape, have been highly refined, and witheta |中国煤化工is long and dffclt tocomputer control they have greatly increased productivity,YHCNMHGthese problems ancReceived June 15, 2004Supported by Shanghai Comission of Science and Technology No. 911065Correspondence should be addressed to AHMED Hassan, email; mudi113@ hotmail. comJourmal of Donghua University (Eng. Ed.) Vol. 22, No.2 (2005)75proposed a variant CAPP system uses a new GT code tousing their serial numbers in database No. 1, these plansprovide more effective method to retrieved process plans.retrieved and print out to user by entering the item numberof the required part.Variant CAPP systemFor new parts, a GT code must be created by usingproposed coding system, then searching for correspondingDifferent process plans stored in two databases asfamily will starts in database No.2, if exact match code isshown in flow chart Fig. 1. Plans for (old) parts stored byfound, typical master plan will be retrieved and print out,if not， the identified master plan will be modified( Suar >according to entered code and print out, then this modified[Anput the part Numberplan will be numbered and stored in the database No.1 forfuturc use. Graphical ilustration of retrieved plan is also| DatabaseEisig Pa心available for users.Ye1 Coding systemr Input the GTPrint Plan]codeSeveral commercial coding schemes bave been usedincluding the Opitz scheme，the KK-3 scheme, MICLASSscheme, etc. One inherent problem with these GT codingNOComesponding masterplan is found -schemes is the lack of infomation relevant to the component'sdesign and manufacturing information requirements.master planFurthermore, process plan generating mechanisms areDatabasesomewhat inflexible. Thus, a new five-digit GT codingPrint modifedPrint the masterlan_scheme uses some elements of Vuoso Praha scheme isproposed as shown in Table 1.Fig.1 Flow chart of CAPP systemTable 1 Proposed coding systemClass of work pieceExternal ShapeInternal hole in axisGroup of work pieceMaterialDL/DRound straight0 None0 Smooth0 Cast iron0-401-6 1 Round step to one endBlind holeThread in axisCarbon SteelRound step to two ends 2 Multi-blind holes2 Hole not in axis 2 Alloy SteelRound change to center 3Step blind holeSlot or groove3 Stainless Steel40- 801-4 4 Taper & ConicalThrough holeComb. 1+24 Aluminum>4Square & Hexagonal5 Through hole step tooneenxd 5 Comb. 1+35 Copper80 - 200< 3 6 Pentagonal & Octagonal6 Thraugh hoale stcP ttwoends 6 Comb. 2+3Zinc80二>37 Sphere7 Through hole step to center 7 Comb. 1+2+3 7 Magnesium200-Profile, Concave&Convex 8 Tapered hole8 Gear & Spline8 TitaniumVarious>30 9 Others9 OthersNickel2 Cell formationsparts) and sorted to manipulate machine-part matrix.A data of rotational parts with different diameters andRank-order clustering algorithm (ROC) was used to re-features : re collected, their production routes are examinedarrange this matrix to form cells as in Table 2. Three part(turning and grinding are common process for ollectedfamilies were arranged (family 1, family 2 and farmily 3).Table 2 Cell Formations10 13 17HorizontalMilingDrilling中国煤化工-VerticalMYHCNMHGTapping3 Selection of blank work piece processproduce rotational blanks and their relation to each digit ofCapabilities of different primary processes that canthe proposed coding system were studied to support our76Joumal of Donghua University (Eng. Ed.) Vo1.22, No.2 (2005)selection of suitable primary processes in planning stage.in codes. Plan retrieved, includes also a suitable set ofProcesses studied in this research that can produce aprimary processes for the blank work piece required Thenrotational part are sand casting, investment casting, diethese processes optimized by user according to the numbercasting，impact extrusion， cold heading， closed dieof parts to be produced.forging, pressing and sintering (P/M)，and hot extrusion.4 ExampleConclusionA user failed to find the corresponding plan by inputthe part item number in database No. 1, then desribed aMachining converts the raw materials into final produrcts,required part by entered a GT code 12042 as shown in Fig. 2.in which, the dimension of work piece change step by stepThis part is belongs to part family 1, a master plan of thisby removing away an excess material from blank， thesefamily is a plan of part code 12542, corresponding plan ofblanks can be found in different sizes from vendors in arequired part, this master plan after modification as shownform of shafts or bars. But, the selection of the optimumin Fig. 3, this modification done acording to the differencessize of blank can be determined more economically inprocess planning stage according to the capabilities 0available primary processes and number of items required.References[ 1] Bhaskara S V. lnternational Journa! of ProductionResearch, 1999, 37 (5), 1063 - 1074[2] George E. Engineering Design-A materials and processingapproach，2nd edition, New York, Mc Graw Hil, 1991Fig.2 Entering a GT code[3] Nicbel w. Journal of Industral Engineering， 1966. 8,598 - 603[4] Wilson, R D. Transactions of the ASME, 1982, 104, 126 -[ 5] Emerson C. Computers and Industrial Engineering, 1982, 6(2): 159- 168CE力Fig.3 Process Plan :中国煤化工MYHCNMHG