S. Rausch

Simulation of grinding processes using finite element analysis and geometric simulation of individual grains

The wear-resistance of sheet metal forming tools can be increased by thermally sprayed coatings. However, without further treatment, the high roughness of the coatings leads to poor qualities of the deep drawn sheet surfaces. In order to increase the surface quality of deep drawing tools, grinding on machining centers is a suitable solution. Due to the varying engagement situations of the grinding tools on free-formed surfaces, the process forces vary as well, resulting in inaccuracies of the ground surface shape. The grinding process can be optimized by means of a simulative prediction of the occurring forces. In this paper, a geometric-kinematic simulation coupled with a finite element analysis is presented. Considering the influence of individual grains, an additional approximation to the resulting topography of the ground surface is possible. By using constructive solid geometry and dexel modeling techniques, multiple grains can be simulated with the geometric-kinematic approach simultaneously. The process forces are predicted with the finite element method based on an elasto-plastic material model. Single grain engagement experiments were conducted to validate the simulation results.

Five-axis grinding of wear-resistant, thermally sprayed coatings on free-formed surfaces

AbstractThe abrasive wear resistance of tribologically stressed free-formed surfaces can be increased with thermally sprayed tungsten carbide coatings. In order to improve the surface topographies and shape accuracies, the workpieces must be finished prior to industrial application. A suitable machining process is NC grinding on five-axis machining centres using abrasive mounted points. However, the high hardness of the applied coatings and the small diameter of the utilized tools pose a great challenge for the process design. In this paper both, the results of fundamental investigations on the grinding of tungsten carbide coatings as well as a process optimization for the finishing of a coated forming tool are presented. This includes the heat transfer into the coating and the tool wear during the grinding process as well as the wear behaviour of the coating in dependence of the generated surface topography. In order to achieve a smooth surface, elastic-bonded diamond tools were used during polishing in a multi-stage machining process.

Prozesskraftsimulation beim NC-Formschleifen

Kurzfassung NC-Formschleifen ist ein Fertigungsverfahren mit geometrisch unbestimmter Schneide zur Herstellung von frei geformten Werkstückoberflächen. Gekennzeichnet wird der Prozess durch den Einsatz keramisch gebundener CBN-Schleifscheiben und einer Variation der Tiefenzustellung während der Vorschubbewegung des Werkstücks. Im Folgenden wird eine Simulation vorgestellt, welche die Prozesskräfte beim NC-Formschleifen für verschiedene Schleifscheibenformen berechnet und eine sichere Prozessführung ermöglicht.