Date of Award
Doctor of Philosophy (PhD)
Dr. M.A. Elbestawi
The current emphasis of CAD/CAM technology, in particular the die and mold manufacturing sector, is to verify and optimize the NC code in terms of the productivity and machining accuracy prior to the actual machining. Also, there is a trend towards enhancing the on-line control strategies with the technological data. However, the intricate geometry with sculptured surfaces which is found nowadays in most of dies and molds, together with relative high material hardness, makes the NC verification/optimization process a very demanding and difficult task. In this regard, the development of model-based simulation methodology with functions of geometrical and physical modeling is a fundamental advancement in improving productivity, accuracy, and automation. In the course of the thesis presented, a new model-based simulation methodology for die cavity milling operations is developed. The comprehensive and realistic simulation of the milling process is implemented in the form of an integrated geometrical/physical/interaction environment. The geometric sub-environment constructs the volume swept by the cutter (or the surface swept by the cutting edge), accurately updates the model of the stock as the cutter removes the material, and automatically extracts the immersion geometry from the updated model. Based on the knowledge of the material remaining on the surface, two- and three-axis tool paths are computed. In the semi-finishing operation, a three-axis milling strategy is developed to control the scallop height remaining on the surface and avoid cutting with the dead zone of the cutter. The physical/mechanical sub-environment, integrated with the geometric counterpart, consists of a newly developed force model as well as a mathematical model of tool-structure dynamics. The integrated environment can accurately simulate the closed loop of the machine tool-cutting process. It predicts the instantaneous cutting forces, tool tip deflections, and the onset of chatter vibrations. The finishing operation is simulated based on the true path of the cutting edge. The method developed is able to construct the geometric model of feed marks and scallops remaining on the surface. Experimental measurements confirm the validity of the implemented methodology. First, the chip geometry is extracted, the part is updated, and the NC codes are verified for two- and three-axis milling of free-form surfaces. Second, the instantaneous cutting forces, tool tip deflections, the onset of chatter vibrations are predicted and compared with the experimental measurements. Next, a new three-axis milling strategy is implemented to control the scallop height and avoid cutting with the dead zone of the cutter. Lastly, the model of feed marks and scallop height are constructed, the feed mark profile is extracted and compared with the measurement. The developed system enhances the capabilities of the CAM/CAM systems in terms of increased productivity, improved machining accuracy, and heightened the level of automation
Moetakef-Imani, Behnam, "Model Based Die Cavity Machining Simulation Methodology" (1997). Open Access Dissertations and Theses. Paper 1131.