Geometric-physical simulation of cutting processes with geometrically undefined cutting edges

For the analysis and optimization of cutting processes with geometrically undefined cutting edges, a simulation system is developed at the ISF. Under consideration of the tool topography, the process simulation allows the calculation of the removed workpiece material and the resulting surface topography of the workpiece. The modeling of the tools is based on the Constructive Solid Geometry modeling technique as well as on measured data. For the representation of the workpiece surface, height fields and dexel boards can be used.

The developed grinding process simulation considers two levels of detail. Using the macroscopic simulation approach, when representing the tool by geometric primitives, the removed material can be calculated for the complete grinding process. The resulting process forces can be approximated and the engagement conditions between tool and workpiece are analyzed concerning the load distribution along the tool topography. Due to the significant influences of the size, the distribution and the shape of the cutting grains at the tool surface on the resulting process forces and surface topography, the macroscopic simulation can only be used for a rough approximation of the load. In order to deal with these restrictions, the simulation system was extended by a mesoscopic level of detail modeling the individual grains. The process forces are then calculated as the superposition of the forces acting on each grain. This approach enables a better approximation of the process forces as well as the resulting surface topography. Based on the simulated tool-load, the wear of the grinding tools and the individual grains will be modelled in order to predict the process forces and the resulting surface topographies depending on the wear state.

For modeling the honing process, a kinematic-physical approach is used as well. Workpiece and tool surfaces are modeled as discrete 3D-surface models, which are gained by using optical measurement techniques. The process model represents the ideal process kinematics. The workpiece is mounted in a global coordinate system whereas the surface of the tool rotates on a stationary radius within the system. By moving the two surfaces relatively to each other and calculating their intersection, the new workpiece surface is created. Experimental results are used as input data for the modeling and to verify the process simulation. By modeling and simulating the honing process, the required number of experiments can be reduced and the determination of surface structures and properties becomes possible in advance.

The figure below shows the engagement situations of a grinding and a honing tool. The cutting grains on the surface of the grinding tool are based on statistical distribution whereas the topography of the honing tool is based on triangulated measurement data. In both cases, the resulting surface topographies can be simulated.

Fig.: Simulation of grinding and honing processes under consideration of the tool and workpiece topography

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