41 Development of CAD models from sketches: a case study for automotive applications R Vignesh, R Suganthan, and K Prakasan* Department of Production Engineering, PSG College of Technolog y , Peelamedu, Coimbatore, India The manuscript was received on 6 April 2006 and was accepted after revision for publication on 2 August 2006. DOI: 10.1243/095 44070JAUT O331 Abstract: Today products are designed not only for their functional requirements but also for aes the tic s. In the automo tiv e ind ust ries, sty lin g has bec ome a major part of the des ign pro ces s wit h cla ss- A surf ace s. Cla ss-A sur fac es ar e fre efo rm sur fac es wit h a con tin uou s curvature. The process of engineering any component or system begins by generating a concept that actually describes the product in terms of its form, function, and fit. Concept sketches help the designers to arrive quickly and easily at a stage where a satisfactory design can be specified for detailed design. These concept sketches can be used for development of the digital concept design and analysis of the curves and surfaces. Software such as Alias exists and thus can be used with suitable hardware for sketching the concept of the car body on a computer screen. In this paper a systematic procedure is discussed for generating class-A surfaces from the images of concept ske tch es whi ch ar e man ual ly pr epa red on pap er. The se ima ges are imported into the sketch tracer module of CATIA V5. A designer can use the image as the reference and produce a digital sketch by tracing the image using CATIA V5 software without adding any special hardware. Later, interrogation of these surfaces for improved aesthetics can be attempted. This method will be useful for the users of CATIA V5 to improve their design practices and skills. Keywords: concept sketches, clay modelling, class-A surface, reflection lines, isophotes 1 INTRODUCTION reason for the evolution of class-A surfaces and their importance. Class-A surfaces are those aesthetic free- Product styling is carried ou t to cr eate visual form surfaces that are visible to us and that have an attractiveness in products. Styling is widely accepted optimal aesthetic shape and high surface quality. as an impo rt an t wa y to ad d valu e to a prod uc t Re sty ling of exi sti ng pro duc ts is fre que ntl y per - without changing its technical performance. formed in the automotive industries, since engineers As new product quality rankings converge, styling usually prefer the evolution of a product to a com- is emerging as a key diff eren tiator for cons umers . plete redesign. Customer feedback, client assistance The role of sty ling is to cr eate fre sh and excit ing suggestions, and market directives usually influence design concepts that are not just contemporary but the decision on redesign or restyling of a product. trend set ting as wel l. St yli ng enhances the visual However, quite often product modifications are less appeal of the vehicles and at the same time develops expensive than the development of a new product. innovative designs and components for customers. A traditional car development process involves the Today, not only are products designed considering development of many handmade rendering sketches the funct ional ity but also speci al consi derat ions are in order to off er a vision of the model’s look. From given to their aesthetics which can produce a desire these sketches, a few are selected and, by pasting the in a person’s mind to own that product. This is the four views of a constrained dra wing on the wall, which are made on a 1 : 10 sca le, the scale d-down cl ay model is developed. One sc al ed-down cl ay * Corresponding author: Department of Production Engineering, model is finalized and the model is scanned using PSG College of Technology, Peelamedu, Coimbatore, Tamil Nadu, 641 004, India. email: prakasan_psg@redi ff mail.com thre e-dimensio nal scann ers. Then a 1 : 1 clay model JAUTO331 © IMechE 2007 Proc. IMechE Vol. 221 Part D: J. Automobile Engineering
