3 Class Asurface catiav5prozesse.de（3类Asurface catiav5prozesse.de）.pdfVIP

3 Class A-surface 3.1 Introduction The german term „Strak“ (in English: Class A-sur face) has its origins in the ship building where complicated free form sur faces were described with vertical, longitu- dinal and cross sec tions (frames). In the au tomotive sector this method was adapted for the generation of all non-pla nar free form surfaces in the exterior and interior work. Be fore CA-tools came into play design surfaces were based on so-called „sec- tions“ which reflect the main curves (char acter lines). For the last 20 years we have been generating surfaces with the help of CA-tools. In this context, the software „ICEM-Surf“ established itself to be the standard tool for sur fac ing, where dif fer ent anal y sis meth ods like high lights, isometric lines as well as curvature guarantee the surface quality in real time. Fig ure 3.1 Sections on a bonnet outer shape Class A-surfaces are the conversion of styling data into technically realizable sur faces. In this chapter we exclusively talk about sub jects con cerning the outer skin (ex te rior work), but the described processes as well as the methods can be applied to the in te- rior work or other design topics as well. 29 Copyright by Richard Haslauer 3 Class A-surface 3.1.1 The design process of Class A-surfaces The first step in a development process consists in finding the design of the new product. Starting from initial outlines a physical model is formed. In order to process this model in CAD we need CAS data or a metrological capture of the shape. The Class A-surface designers have to convert the digitised points or the CAS data into manuf