5 th International & 26 th All India Manufacturing Technology, Design and Research Conference (AIMTDR 2014) December 12 th –14 th , 2014, IIT Guwahati, Assam, India 98-1 Formulating Midsurface using Shape Transformations of Form Features Yogesh H Kulkarni 1 , Anil Sahasrabudhe 2 , Mukund Kale 3 1 * College of Engineering Pune, kulkarniyh12.mech@coep.ac.in 2 College of Engineering Pune 3 Siemens PLM Pune Abstract Shapes modelled using Computer Aided Design (CAD) applications are used in downstream applications like, manufacturing (Computer Aided Manufacturing, CAM), Analysis (Computer AidedEngineering, CAE) etc. Use of form features is prevalent in the CAD applications, but their leveraging in the downstream applications is not very common, especially in the CAE applications. The initial phase of design demands for quick analysis of the model. Here, CAD models are oftensimplified by removing the irrelevant features (de-featuring) and by idealizing solids to surfaces or curves(dimension reduction), so that the CAE analysis gets performed with lesser resources and time. MidsurfaceExtraction is one of the ways of dimension reduction where thin-walled portions of a solid areidealized to surfaces lying midway. This paper presents a novel representation scheme (called ABLE) for CAD entities and operators including formfeatures which is then leveraged to define the algorithm for extracting Midsurface. Keywords: CAD, Spatial Grammar, Form Features, Sheet Metal Features, CAE, Midsurface 1 Introduction CAD applications are widely popular in product design. They aid the design process by presenting easy-to-use ways of defining shapes, attributes, relationships etc. Shapes modelled in CAD can then be used in various downstream applications like drafting, analysis, manufacturing etc. Many commercial CAD applications provide Design-by- Features approach. Features not only carry shape information (geometry, topology) but also embed meta-information based on the application’s need. Features also reflect terminologies used in the application, thus making them intuitive to use. But this has given rise to various feature-schemes not only in different CAD applications but also in various environments present within the same CAD application. Shape that a feature represents could be similar but its featurenomenclature, usage, could be different in different environments-applications. Features like Box, Pad, Protrusion, Extrude, appear different in nomenclature, but they all could be representing the same shape-operation. This diversity of vocabulary creates problems in learning new CAD systems, interoperability between different CAD applications, and also in development of functionality for downstream applications. This is evident in relatively lesser usage of features in the downstream applications, especially, CAE. Instead of plethora of feature nomenclatures, a neutral-standardized internal representation would be very useful. Functionality developed on top of such representation will have advantage of applicability over variety of feature representations present in different CAD applications. This paper presents an idea of formalizing form features in terms of Spatial Grammar notations and demonstrates its use in developing algorithms on top of it, for downstream applications, like Midsurface for CAE. 2 Related Work Following subsections explore salient work done so far in the areas relevant to the topic, like, Spatial Grammars, Form Feature Representation and Midsurface Representation. 2.1 Spatial Grammars Spatial Grammars is a general term which encompasses shape definition Grammars, like Graph Grammars, Shape Grammars, Set Grammars, etc. Aim of Spatial Grammars is to bring formalism through terse but expressive definitions, validations and