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【机械类毕业论文中英文对照文献翻译】钣金在级进模中的工步排样设计自动化【PDF英文7页word中文翻译6678字12页】【有出处】,机械类毕业论文中英文对照文献翻译,PDF英文7页,word中文翻译6678字12页,有出处,机械类,毕业论文,中英文,对照,文献,翻译,级进模,中的,工步排样,设计,自动化,PDF,英文,word,中文翻译
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journal of materials processing technology 1 9 5 ( 2 0 0 8 ) 94100journal homepage: /locate/jmatprotecAutomation of strip-layout design for sheet metalwork on progressive dieS. Kumara, R. SinghbaDepartment of Mechanical Engineering, Hindu College of Engineering, Sonepat, Haryana, IndiabDepartment of Mechanical Engineering, CRSCE, Murthal, Haryana, Indiaa r t i c l ei n f oArticle history:Received 13 November 2006Accepted 18 April 2007Keywords:AutomationStrip-layout designSheet metal workProgressive dieExpert systema b s t r a c tStrip-layout design is an important step in the planning stage of sheet metal work on pro-gressive die. It is an experience-driven activity and the quality of strip-layout is highlydependent on the knowledge and skill of die designers. This paper presents an expertsystem for automation of strip-layout design process. The proposed system is developedusing the production rule-based expert system approach of Artificial Intelligence (AI). Itcomprises six modules to impart expert advices to the user for identifying sheet metal oper-ations, sequencing of operations, selection of proper piloting scheme, number of stations,staging of operations on progressive die and selection of proper dimensions of stock strip.Finally, the system models the strip-layout automatically in the drawing editor of AutoCADusing the output data files of other modules. Usefulness of the system is demonstratedthrough an example of an industrial component. The system is flexible and has low cost ofimplementation. 2007 Elsevier B.V. All rights reserved.1.IntroductionStrip-layout design has an extreme importance during theplanning stage of progressive die design as the productivity,accuracy, cost and quality of a die mainly depends on thestrip-layout (Tor et al., 2005). Traditional strip-layout designis manual, highly experience-based activity and thereforetedious,timeconsuminganderror-prone(Lietal.,2002;Ridha,2003). Four decades earlier strip-layout problems were solvedmanually. The blanks cutting from cardboard were manip-ulated to obtain a good strip-layout. This trial and errorprocedure of obtaining suitable strip-layout with maximummaterial utilization is still being used in most of the smallscale and even in some medium scale sheet metal industriesworldwide. The quality of strip-layout achieved by using tra-ditional methods depends on the experience and knowledgeof designers. On the advent of computer aided design (CAD)Corresponding author. Tel.: +91 9416942082; fax: +91 1302212755.E-mail address: skbudhwar2003yahoo.co.in (S. Kumar).systems around 3 decades earlier, the process of strip-layoutdesign was somewhat made easier and the design lead-timewas reduced from days to hours. However, well-trained andexperienced die designers were still required to operate theseCAD systems. Most of the applications of CAD in strip-layoutdesign are aimed mainly at achieving better material utiliza-tion by rotating and placing the blanks as close as possiblein the strip. However, the strip-layout with maximum mate-rial saving may not be the best strip-layout, indeed the dieconstruction may become more complex, which could offsetthe savings due to material economy unless a large num-ber of parts are to be produced. The system developed bySchaffer (1971) in 1971 reported to calculate the stresses dueto bending moment on cantilevered die projections and if thesystem finds that the stress level is above the yield stressof die steel material, then the system distributes the cuttingoperations over several stages in order to keep the stresses0924-0136/$ see front matter 2007 Elsevier B.V. All rights reserved.doi:10.1016/j.jmatprotec.2007.04.119journal of materials processing technology 1 9 5 ( 2 0 0 8 ) 9410095Table 1 A sample of production rules incorporated in the proposed systemSerial numberIFTHEN10.001minimum accuracy required on part in mm0.2 andfeature required on part=hole or slot or internal contour cutRequired operation=piercing20.001minimum accuracy required on part in mm0.2 andfeature required on part=small cut or notch on externalboundary or contourRequired operation=notching30.001minimum accuracy required on part in mm0.2 andfeature required on part=complete cut on one side of partRequired operations=parting off/cut off4Required operations: notching, blanking/parting off, piercingPreferred sequence of operation: 1st, piercing;2nd, notching; 3rd, blanking/parting off5Number of holes exist on the part2, shape of holes=circular,diameter of holes1.0mm, hole pitch2.0 times of sheetthickness, distance of holes from the edge of part2.0 timessheet thickness, specified tolerance on holes0.05mm, andholes are located on opposite sides of the partSelect the two largest holes for piloting6There are suitable holes available in the componentPierce these holes at first station and use themfor piloting7The minimum distance between the edge of the internal featureand edge of die block2.0 times of sheet thickness (but not lessthan 3.0mm) OR there is any possibility of future engineeringchanges in the design of partLeft idle station8Required operations on part=notching (2), piercing (any numberof holes) and parting off; distance of hole(s) from edge of partand hole pitch2.0 times of sheet thicknessNumber of stations=5. Preferred staging: 1ststation, piercing; 2nd station, notching andpiloting; 3rd station, notching and piloting; 4thstation, parting off9Sheet thickness1.4mm; 25blank contour width75mm;sharp edge (along width of sheet) exists in the edgeperpendicular to the moving direction of the sheetSelect sheet width in mm=(blank contourwidth+3.2)10Sheet thickness0.8mm; blank contour length25mm; sharpedge (along length of sheet) exists in the edge parallel to themoving direction of the sheet (along width of sheet)Select feed distance in mm=(blank contourlength+2.0)within the reasonable limit. One of the limitations of the sys-tem is that it does not give any importance to the complexityof die and punches during staging of operations. Adachi etal. (1983) developed an integrated CAD system for design ofprogressive die. The system outputs also include generationof strip-layout for progressive die. But the user has to specifythe sequence of operations himself to obtain the strip-layout.Nee (1984a,b, 1985) developed some experimental packagesfor analysis on press capacity, the use of coiled or strip stockand cost factors in order to solve for near-optimum layout andnesting problems for both sheet metal and metal stampingblanks. All of his work focused on the general strip-layoutdesign process and the expert rules involved do not tackleother stamping operations such as piercing, bending, form-ing, etc. The system developed by Duffy and Sun (1991) usedknowledge-based system approach to generate strip-layoutfor progressive stamping dies. The system was implementedin IDL, which is a knowledge-based system language. The sys-tem has the capability to generate strip-layout; however, it hasnot been implemented and its capabilities in real life have notbeen tested. The Computer Aided Die Design System (CADDS)developed by Prasad and Somasundaram (1992) also has onemodule for the strip-layout for progressive die. In this module,the die type is selected, depending on the input parame-ters. If the selected die is progressive, strip development issubsequently carried out according to the rules incorporatedin the strip-layout module. But the major limitation of thesystem is that it supports mainly blanking and piercing opera-tions. Singh and Sekhon (2001) developed a low cost modellerfor two-dimensional metal stamping layouts. The software isbased on AutoCAD and AutoLISP. The system is capable ofmodeling circular, polygonal and components having curvedsegments. Alternative strip-layouts are also generated andtested for optimality. The main limitation of the system isthat it deals with single operation stamping dies. Kim etal. (2002) developed a system using AutoLISP language. Thesystem decides the sequencing process of electric productswith intricate piercing and bending operations by consider-ing several factors on bending and adopting fuzzy set theory.It constructs fuzzy matrix for calculating fuzzy relationshipvalue and determines the optimum bend by combining sev-eralruleswithfuzzyreasoning.Thestrip-layoutmoduleofthesystem is able to carry out bending and piercing operations of3D electric product. The main limitation of this system is thatit deals with only bending and piercing operations on progres-sive die. Venkata Rao (2004) presented a strip-layout selectionprocedure pertaining to metal die stamping work. The pro-cedure is based on analytic hierarchy process (AHP). But, thedeveloped procedure is applicable only for simple blankingand piercing dies. Chu et al. (2004) proposed a mathematicaltechnique capable of generating a stamping sequence auto-maticallyinthedesignofprogressivestampingdies.Agraphisused to represent a stamping part and define the relationshipsbetween its stamping features. The graph is partitioned intosets of mutually independent vertices using a clustering algo-rithm. Finally, the clustered sets are ordered to give the finalsequence of workstations. Completion and development of asoftware prototype of the system is still in progress and has96journal of materials processing technology 1 9 5 ( 2 0 0 8 ) 94100Fig. 1 Execution of the proposed system.to be tested against real industrial sheet metal parts havingdifferent shapes.The foregoing literature review reveals that only a fewresearch and development works have been carried out inthe area of automation of strip-layout design for sheet metalwork on progressive dies. Most of the works are concentratedon process planning for sheet metal blanking and piercingoperations. Some commercial computer aided systems areavailable to assist die designers but these are limited only tosimple calculations, strip nesting, retrieval of catalogue dataand compiled database of standard die components, none ofthem directly addressed the problem of strip-layout design.The dependence on experience coupled with the mobility ofdie designers in stamping industries has caused much incon-venience to the sheet metal industries all over the world.Therefore, it has become essential to capture knowledge andexperience of die designers into an expert system so that itcanberetainedandutilizedsuitablyforfutureapplicationanddevelopment purposes. Although some expert systems havebeen developed for die design area, but most of the researchworks are concentrated on nesting and process planning ofsheetmetalforminganddrawing.Nospecificsystemhasbeendeveloped for solving strip-layout design problem of progres-sive dies. To improve productivity and to build a computerintegrated manufacturing environment, automatic modelingof strip-layout design is essential. The objective of the devel-opment work presented in this paper is to concentrate on theautomationofstrip-layoutdesignusingproductionrule-basedexpert system approach of Artificial Intelligence (AI). The sys-tem is implemented on PC having AutoDesk AutoCAD 2004software and designed to be loaded in the prompt area ofAutoCAD.2.Recommendations for strip-layoutdesignStrip-layout design for progressive die is to arrange layout ofthe operations and subsequently determine the number ofstations required. For design of strip-layout, the die designerdetermines the sheet metal operations required for manu-facturing the parts, sequencing of operations, selection ofpiloting method, number of stations required and the oper-ations stamped at each station of progressive die. Strip-layoutis determined by the shape of a part and its technical require-ments. It is generally governed by the geometrical featuresjournal of materials processing technology 1 9 5 ( 2 0 0 8 ) 9410097Fig. 2 Example component (brass, sheetthickness=0.6mm).of the part, tolerance on dimensions of the part, direction ofsharp edge of stock strip and other technical requirements.One important, but very difficult task in strip-layout design isthe determination of a proper sequence of stamping opera-tions so that the part can be stamped correctly and efficiently.The sequence of operations on a strip and the details of eachoperation must be carefully developed to ensure that thedesign will produce good sheet metal parts without produc-tion or maintenance problems. Normally there is no uniquebest solution for the strip-layout design but certain commonrules can be used to guide the design of strip-layout. Some ofthe important rules generally used for strip-layout design areas follows:(1) Theinitialoperationssuchassidecutsorcropping,whichdonotdirectlyaffecttheshapeofthefinalproductshouldbe made in the first stage.(2) If there are suitable holes available in the sheet metalpart, these holes should be used for piloting; otherwiseexternal pilot holes should be introduced according tothe progression. Piercing of these pilot holes is done inthe first stage or just after cropping stage. The loca-tion of pilot holes should always be the far oppositesides of the strip, with the greatest possible gap inbetween. This is to secure the best fixation and position-ing of the strip, once the pilots engage in their respectiveopenings.(3) Distances between the holes punched on one stationmust be larger than a certain value to ensure the diestrength. Pierced holes may be distributed over severalstages, if they are closely located and functionally notrelated.(4) Holes with high position accuracy requirement should bepunched in one station.(5) Narrow slots and projections should not be allowed in adie as fracture may occur.(6) If the external profile of the blank is complex, then theprofile may be split into simple sections by projecting allthe vertices of the blank vertically up to the edge of thestrip.(7) Idle stations may be used to avoid crowding of punchesand die blocks together. An added advantage is thatFig. 3 Strip-layout generated by the proposed system forexample component.future engineering changes can be incorporated at lowcost.(8) Bending should preferably be done in the last station orprior to the parting stage, and the rest of the strip shouldbe arranged around such a requirement.(9) Finally, the parting off or blanking operation(s) and inter-nal holes used as semi-piloting holes (if any) should bestaged.(10) Sufficient bridge width should be used in order to providemaximum strength for the bridges.(11) Finally, design the strip in such a way that it enables thecomponent and scrapes to be ejected without interfer-ence.Pilotingisanimportantfactorinstrip-layoutdesignforpro-gressive die. The strip must be positioned accurately in eachstation so that the operations can be performed at the properlocations. The task of selection of piloting scheme shouldbe viewed as interdependent task in the strip-layout designprocess. A strip-layout design system should support directpiloting, semi-direct piloting and indirect piloting scheme. Aholeisconsideredtobesuitableforuseasapilotholeifitiscir-cular in shape, specified size tolerance is not high, big enoughfor use as a pilot hole, does not lie on the folded portion of theworkpiece, not too close to the edge of the workpiece, and nottoo close to another hole on the workpiece. From the list ofsuitable pilot holes, the best piloting holes should be selectedbased on the following priority:(1) If only one hole is available, it must be considered in thefirst instance.(2) If there are a number of holes, then the location of theseholes should be examined.98journal of materials processing technology 1 9 5 ( 2 0 0 8 ) 94100Table 2 Typical prompts, user responses and expert advices generated during execution of the proposed expert systemfor example component (Fig. 2)PromptExample data entryAdvice to the userPlease enter sheet materialBrassModel the blank using AutoCAD commandsPlease enter sheet thickness in mm0.6Please enter the command OPRPLANOPRPLANWelcome to the module OPRPLAN, developed foridentification of operationsEnter type of feedAutomaticIs camber present in the strip?NoPlease enter the geometrical features of the part in formof questionnaire (Yes/No)Is small cut(s) or notch(es) existing on externalboundary or contour?YesIs hole(s) or slot(s) or internal contour cut exist-ing?YesIs sheet edge(s) rough?NoDoes bend along a straight axis exists?NoIs curved bend or forming existing?NoIs complete cut required at any side of blank?YesFollowing operations are requirednotching, piercingand parting off. Please enter the command OPRSEQOPRSEQWelcome to the module OPRSEQ developed foridentifying the proper sequence of operations. Theproper sequence of operations is as follows: 1st,piercing; 2nd, notching; 3rd, parting off. Please enter thecommand PLTSELPLTSELWelcome to the module PLTSEL, developed for selectionof piloting schemeIs any folded portion on the part?NoEnter specified tolerance (in mm) on hole(s)0.05Are holes located on opposite sides of the part?YesSelect the two largest holes located on opposite sides ofpart for piloting (direct piloting). Please enter thecommand OPRSTAGEOPRSTAGEWelcome to the module OPRSTAGE developed fordeciding number of stations and staging of operationson progressive die. Please enter the commandOPRSTAGE1OPRSTAGE1Is the center-to-center distance between holeshas tolerance range within 0.05mm?YesPierce these holes at the same stationAre there any complex or weak sections in theexternal profile of the part?NoIs the minimum distance between the edge of theinternalfeatureandedgeofdieblock2.0timesof sheet thickness (but not less than 3.0mm)?R There is any possibility of future engineeringchanges in the part?NoPlease enter command OPRSTAGE2OPRSTAGE2Enter number of notches in the part2Enter number of holes in the part2Number of stations required=5. Preferred staging ofoperations: 1st station: piercing; 2nd station: punching,notching and piloting; 3rd station: notching andpiloting; 4th station: notching and piloting; 5th station:parting off. Please enter command SWLSELSWLSELWelcome to the module SWLSEL developed fordetermining strip width and feed distanceEnter blank contour width in mm62.0Enter the sharp edge direction of the sheet (alongwidth of sheet)ptmdsaSelect strip width in mm=65.2Enter blank contour length in mm12.7Enterthesharpedgedirectionofthemovingsheet(along the length of sheet)partmdsbSelect feed distance (or pitch) in mm=14.7. Please entercommand STRPLYTSTRPLYTWelcome to the module STRPLYT, developed forautomatic modeling of strip-layoutSelect a start point(220,100)The strip-layout modelled by the system is shown inthe drawing editor of AutoCADaptmds, perpendicular to the moving direction of strip.bpartmds, parallel to the moving direction of strip.journal of materials processing technology 1 9 5 ( 2 0 0 8 ) 9410099(a) If holes are located in the same direction as feed ofthe strip, then select one hole, which is nearest to thecentroid of the part.(b) If holes are located in the perpendicular direction asthat of feed, then select the two largest holes (whichare equal in diameter) and that are located at a dis-tance at least two times of sheet thickness.(3) Select the two largest holes (the diameters of which arewithin a pre-set percentage of each other), which satisfythe earlier conditions.Keeping in view of the above basic guidelines and recom-mendations, an expert system for automation of strip-layoutdesignforsheetmetalworkonprogressivediehasbeendevel-oped. A brief description of the proposed system is given asunder.3.Development and execution of theproposed systemKnowledge is acquired for each module of the proposedsystem from various sources (Kumar et al., 2006) includ-ing experienced die designers, shop floor engineers, diedesign handbooks, research journals, catalogues and indus-trial brochures. The design information gathered from varioussources has been converted into usable knowledge by fram-ing suitable production rules of the IF-THEN variety. For theproposed system, it was convenient to divide the whole set ofproductionrulescomprisingtheknowledgebaseintosixmod-ules, namely OPRPLAN, OPRSEQ, PLTSEL, OPRSTAGE, SWLSELand STRPLYT. The production rules framed for each modulewere crosschecked from other team of die design experts bypresenting them IF-condition of the production rule of IF-THEN variety. A sample of production rules so framed andverified;andthenincorporatedinthemodulesoftheproposedsystem is given in Table 1. The sequencing of production rulesof the proposed system is unstructured as this arrangementallowsinsertionofnewproductionrulesevenbyrelativelylesstrained knowledge engineer. The rules are coded in AutoLISPlanguage as it can be interfaced with AutoCAD for model-ing of strip-layout. The production rules and the knowledgebase of the system are linked together by an inference mech-anism, which makes use of forward chaining. The knowledgebaseoftheproposedsystemcomprisesmorethan300produc-tion rules of IF-THEN variety. However, the system is flexibleenough as its knowledge base can be updated and modified, ifnecessary, on the advancement in technology and availabilityof new facilities on shop floor.The execution of the system is shown through a flow chartin Fig. 1. The system invites the user to model the blankusing AutoCAD commands. Next the user has to enter partdata information such as sheet thickness, sheet material, etc.through prompt area of AutoCAD. The system automaticallystores these part data in a part data file labeled as COMP.DAT.ThefirstmoduleOPRPLANoftheproposedsystemdeterminesthe type of sheet metal operations required to manufacturethe part. The module invites the user to supply relevant inputdata namely dimensional tolerance and geometrical featuresof the part. The outputs of this module are in the form of rec-ommendationsforthetypeofsheetmetaloperationsrequiredtomanufacturethepart.ThenextmoduleOPRSEQdeterminesthe sequencing of recommended sheet metal operations. Ittakes its input directly from the output data file OPRPLAN.DATgenerated during the execution of module OPRPLAN. Themodule PLTSEL is developed for selection of proper pilotingscheme for positioning the strip accurately in each station ofprogressive die. The next module OPRSTAGE is developed forimparting expert advices for the number of stations requiredand preferred staging of operations on progressive die. Thismodule takes its inputs from the output data file OPRSEQ.DATgenerated during the execution of module OPRSEQ, and alsoinvites the user to enter job specific data as per the part fea-tures.ThemoduleSWLSELdeterminesthepropersizeofsheetmetal strip. The modeling module STRPLYT erases any previ-ous drawing existing in the drawing editor of AutoCAD andselects an appropriate screen setting for modeling the strip-layout. Next, it asks the user to select start point on the screenof AutoCAD. As soon as the user selects a start point using thecursor or entering in the prompt area of AutoCAD, the moduleSTRPLYT models the strip-layout automatically in the drawingeditor of AutoCAD.4.Validation of the proposed systemThe proposed system was tested for different types of sheetmetal parts for the problem of strip-layout design. Typicalprompts, user responses and the recommendations obtainedby the user during execution of the proposed system for oneexample component (Fig. 2) are given through Table 2. Thestrip-layout generated by the system is shown in Fig. 3. Theoutputs received from the system modules in form of iden-tification of operations, sequencing of operations, selectionof piloting scheme, number of stations required, staging ofoperations and size of stock strip are found similar and veryreasonable to those actually practiced by experienced diedesigners and process planners in stamping industry namelyIndo Asian Fuse Gear Limited, Murthal, Haryana, India, for theexample component. The drawing of strip-layout generatedby the developed system is also in close agreement with theexperienced die designers.5.ConclusionResearch effort has been applied for automation of strip-layout design for sheet metal work on progressive die.Production rule-based expert system approach has been uti-lized for development of the proposed intelligent system.Production rules are coded in AutoLISP language to constructknowledge base of the system since it can be interfaced withAutoCAD for modeling of strip-layout. The system is capableto impart expert advices on the type of sheet metal operationsrequired for manufacturing the part, sequencing of the opera-tions, selection of proper piloting scheme, number of stationsrequired and preferred staging of operations on progressivedie; and selection of suitable size of stock strip. Finally, basedonthe
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