Experimental characterization of micromilled surfaces by large range AFM

Surface generation by ball nose micromilling can be simulated based on technological parameters (ball nose radius, axial and radial depth of cut, feed rate, cutting speed). However, surface 3D topography of such surfaces often widely differs from the simulated one due to the distinctive behaviour of workpiece material, particularly when sub-micrometer chip thicknesses are considered and when machining hard materials. Quantification of surface topography is of fundamental importance for the evaluation of the generated surface; high resolution and wide measuring range being highly desirable for the evaluation of the distinctive behaviour of the ball end mill. The combination of the two demands is to date not matched by any measuring instrument. The paper describes an experimental investigation of surface topography of such micromachined surfaces. Accurate characterization of fine surface details was achieved by the use of an atomic force microscope mounted on a CMM, which takes advantage of the small radius of curvature of its tip. Its limitation on the scanning range is overcome by taking multiple scans and stitching procedures. Other measuring techniques such as, stylus profilometry, optical profilometry and scanning electron microscopy are used for comparison.