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Strip-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 sixmodules to impart expert advices to the user for identifying sheetmetal 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. 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). 33292
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Traditional strip-layout designis manual, highly experience-based activity and thereforetedious, time consuming and error-prone (Li et al., 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)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 stresses 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-optimumlayout 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 systemlanguage. The sys-temhas the capability to generate strip-layout; however, it hasnot been implemented and its capabilities in real life have notbeen tested.