Computer-integrated design, fabrication and inspection of a 3-D curved surface

This paper describes the computer-integrated design, fabrication and inspection of a 3-D curved surface as part of a wider study into the creation, machining and measurement of free-form surfaces. Using the CATIA solid modeller, a 3-D curve was first created using both a single arc and a spline followed by a surface patch. The surface generated by the two spline curves was faceted in appearance when machined, whereas that of the single arcs was smooth. An NC part program was generated interactively with dynamic, on-screen tool path display. However, because it was inconvenient to change the machining parameters, such as feedrate, within the NC program, a custom macro was written to make the NC program more readily modifiable. Machining tests carried out on aluminum and carbon steel test specimens yielded encouraging results. In the computer-assisted measurement of the surface on a CNC CMM, the VDA (Verband der Automobilindustrie Surface Data Communication Interface was adopted as the medium for data exchange between the CAD/CAM system and the CNC CMM. Instead of the SURF (surface) function, measurement was accomplished using a sequence of discrete measurement points, PSET.