Study On Numerical Simulation And Key Technologies Of High-speed Machining Process For Auto Panel Dies

Auto panel dies are large and complex equipments for automobile production. High-speed machining (HSM) technology can be widely used to produce auto panel dies for its great increases in material removal rate, machining accuracy, and machined surface quality, while decreases in machining cost. Technologies of high-speed machining process are very important for HSM application. The study on numerical simulation and key technologies of high-speed machining process for auto panel dies has great theoretic significance and practicability.Mo-Cr alloy iron is the most important material often used to make auto panel dies. Firstly, the static and dynamic mechanical properties of Mo-Cr alloy iron were studied based on the high temperature elongation experiment and the high-speed compression experiment. Material's elastic modulus, tensile yield strength, ultimate tensile strength, and the stress-strain relation at various temperatures and various strain rate were studied and the initial data for establishing finite element models of high-speed machining were gained. In high-speed cutting experiments, the cutting forces of high-speed machining dies surface feature with varied cutting parameters were measured. These data were used to validate and improve finite element models, and were the foundation of accurate numerical simulation of high-speed machining process for auto panel dies.In order to study high-speed machining mechanism and optimize machining parameter, the technique route of numerical simulation of high-speed machining process for auto panel dies was marked out. Complex phenomena such as high-speed cutting force, cutting heat and heat-force coupling were deeply analyzed. Large deformation theory and virtual work principle were applied to study high-speed machining process. The finite element governing equation adapted to high-speed machining was achieved. Several key finite element techniques for heat-force coupling in high-speed machining process were studied. The material constitutive equation was established based on the experiments data. The chip separation criterion was applied and the numerical simulation of high-speed cutting Mo-Cr alloy iron was achieved by using DEFORM. The cutting force and chip shape in numerical simulation were analogical with the result got from theory models and high-speed machining experiments. Setting machining efficiency, cutting tool life and machined surface quality as optimization objects, the most appropriate high-speed machining parameters were selected, and the rule of machining parameters affecting cutting tool life and machined surface quality were acquired.The quality of machining shape surface is the key factor for auto panel dies manufacturing. Based on analyzing and comparing excellence and shortcoming of continuous 3-axis and continuous 5-axis numerical control machining, the advantage of 3 +2-axis (i.e. positional 5-axis) numerical control for zonally high-speed machining auto panel dies surface was shown. The key techniques of applying 3+2-axis numerical control to high-speed machining auto panel dies shape surface such as optimizing of tool axis obliquity with the normal of cutting surface, the machining zone partition and the optimization cutter shaft direction design were studied. The calculation program of optimizing cutter shaft for 3+2-axis numerical control machining was developed and the problem of how to improve machining quality of high-speed machining auto panel dies shape surface was resolved.It is very imperative to develop high-speed machining database for manufacturing industries that apply high-speed machining commonly. Case-based reasoning (CBR) is an available approach for developing high-speed machining database. The function of high-speed machining database system for auto panel dies with case-based reasoning was marked out, and its structure was established. The study emphasized on resolving key techniques such as the expression of high-speed machining case, case similarity and its calculation, case attribute's weight factor and their distributing, the dynamic adaptation of similarity and weight, case searching, case rewriting, case saving and the mechanism of case based reasoning system learning by itself. The high-speed machining database system for auto panel dies with case based reasoning was developed and integrated into UG system.In order to make the best recycle of automobile panel dies with partial physical lacuna or fatigue abrasion, a technique coupling extracting disfigurement feature and FEM was proposed. Applying feature inducement technique, the original basic feature morphology of the disfigurement die was resumed based on extracting features from its point cloud of a die such as disfigurement edges and original morphology etc. The basic feature morphology was rectified and the CAD model of the partial lacuna was repaired simulating dynamical pressing process. So that, the reliable foundation was provided for rapidly physically repairing automobile panel dies based on numerical control high-speed machining technology.The study in this dissertation offered a theoretic guidance and technical assurance for accelerating the high quality application of high-speed machining in the whole life cycle of automobile panel dies. The research result was applied to productive practice and its effect was fine. With further study, the finite element simulation precision for high-speed machining will be improved. The error compensating technique of high-speed machining auto panel dies shape surface will become an aspect of the further study. Based on network cooperating, high-speed machining database system which is more intelligent will be researched and developed.