Future Developments in Surface Metrology

This chapter deals with the next generation GPS system. The current GPS system is developed from three distinct sources: (1) geometrical tolerancing, (2) co-ordinate metrology, and (3) surface texture and form measurement. One particular challenge with the current GPS system that affects surface texture is the fact that there are two workpiece co-ordinate systems. The workpiece co-ordinate system for surface texture is based on the direction of the surface lay. A surface texture profile is measured perpendicular to the surface lay. The rest of the current GPS system uses a workpiece co-ordinate system that is based on the geometry of the workpiece. The fundamental GPS principle, which can address this particular challenge, is the recognition that it is surfaces that interact with each other functionally, not profiles. Hence, the principal GPS definitions should be based on surfaces, with profile definitions as secondary simplified operators. Thus, the next generation GPS will be one system based on surfaces. The full specification of surface texture has many stages: from the size, shape and location of the measuring window (partition), the sampling procedure (extraction), the scale of the features of interest (filtration) to the definition of the surface texture characteristic (measurand). At each stage there are many choices to be made, depending on the design requirements of the surface to be specified. The challenge for the future is to standardize a set of tools for each stage that will enable optimization of the design requirements and especially the functional requirements of a surface.