Huseyin Erdim

High accuracy NC milling simulation using composite adaptively sampled distance fields

We describe a new approach to shape representation called a composite adaptively sampled distance field (composite ADF) and describe its application to NC milling simulation. In a composite ADF each shape is represented by an analytic or procedural signed Euclidean distance field and the milled workpiece is given as the Boolean difference between distance fields representing the original workpiece volume and distance fields representing the volumes of the milling tool swept along the prescribed milling path. The computation of distance field of the swept volume of a milling tool is handled by an inverted trajectory approach where the problem is solved in tool coordinate frame instead of a world coordinate frame. An octree bounding volume hierarchy is used to sample the distance functions and provides spatial localization of geometric operations thereby dramatically increasing the speed of the system. The new method enables very fast simulation, especially of free-form surfaces, with accuracy better than 1 micron, and low memory requirements. We describe an implementation of 3 and 5-axis milling simulation.

Modeling Cutting Forces for Five Axis Milling of Sculptured Surfaces

5-axis ball-end milling processes are used in various industries such as aerospace, automotive, die-mold and biomedical industries. 5-axis machining provides reduced cycle times and more accurate machining via reduction in machining setups, use of shorter tools due to improved tool accessibility. However, desired machining productivity and precision can be obtained by physical modeling of machining processes via appropriate selection of process parameters. In response to this gap in the industry this paper presents a cutting force model for 5-axis ball-end milling cutting force prediction. Cutter-workpiece engagement is extracted via developed solid modeler based engagement model. Simultaneous 5-axis milling tests are conducted on Al7075 workpiece material with a carbide cutting tool. Validation of the proposed model is performed for impeller hub roughing toolpaths. Validation test proves that presented model is computationally efficient and cutting forces can be predicted reasonably well. The result of validation test and detailed comparison with the simulation are also presented in the paper.

High Performance 5-Axis Milling of Complex Sculptured Surfaces

5-axis milling processes are used widely in various industries such as aerospace, die-mold and biomedical industries where surface quality and integrity is important and the production tolerances are very tight. Therefore, improving surface quality and integrity without sacrificing productivity is crucial in these industries. Improvements in CAD/CAM, cutting tool and the machine tool technologies allow the production of high precision parts with less cycle times. In order to obtain desired quality and productivity, process parameters such as feedrate, spindle speed, axial and radial depth of cut have to be selected appropriately. Most of the time, selection criterion is based on engineering expertise or trial and error methods. Besides, to prevent the cutter or the machine to be damaged, machining parameters are selected conservatively, and therefore, virtual machining simulation for milling processes is an increasing demand before the production of the free-form surfaces.