Development Of Five-axis Linkage Edm Machine Tool And The Presetting System

Nowadays, multi-axis linkage EDM machine tools in some developed countries have stepped into the stage of industry application and commercial distribution, whereas, domestic multi-axis linkage EDM machine tools are in the starting stage. Multi-axis linkage EDM machine tools often applied in aviation, spaceflight and military so on, are prohibited goods to our country. So it is of realistic significance for developing aviation, spaceflight and defense, even the whole manufacturing industry, to develop multi-axis linkage EDM machine tools with own intellectual property rights.Nozzle and turbine blisks, as key parts of a liquid rocket engine, are attention focuses in manufacturing industry all the time. But they can be machined very difficultly because of specialities of material and structure characeteristic. Electrical discharge machining (EDM) with multi-axis linkage is deemed to be an efficacious method for machining mentioned parts. Aiming at generic technologies in five-axis linkage micro and moulding EDM machine tools, error analysis and design for five-axis linkage EDM machine tools are developed. According to the problem that machining efficiency is very low because of overlong auxiliary time of measurement and adjustment for complicated electrodes in EDM for rimed turbine blisks, the presetting system for complicated electrodes is designed.By analyzing machining methods of tangent and oblique small holes on nozzles, a topologic structure and a lower body array for the five-axis linkage micro-EDM machine tools are built under the foundation of multi-body system kinematics and its spatial position error model, which is simplified with actual designing situation of machine tools, is deduced by using homogeneous coordinate transformation. Furthermore, simplified error models for a five-axis linkage moulding EDM machine tool and the presetting system for complicated electrodes are obtained. Simplified error models have some guidance significance to error distribution and compensation for machine tools.Aiming at tangent small holes on the nozzle, the five-axis linkage micro-EDM machine tool is developed under the foundations of specification of machining equipment from micro-EDM and the simplified error model in the paper. The machine tool is composed of a mechanical system, an electrical system and a software system. A spindle servo system, as the important part of micro-EDM machine tool, has important influnces to machining efficiency, machining quality and electrode relative wear. After adjusting PID parameters, The systen with high resolution, high accuracy, rapid speed and rapid response so on, can implement servo feed control strategies for micro-EDM that large displacement movement is implemented in short circuit and open circuit and small displacement movement is implemented in near-short circuit and near-open circuit. For difficult-to-cut materials applied in aviation and space flight widely, a high-low voltage combined pulse generator is designed to improve machining efficiency of micro-EDM under the precondition that machining accuracy of tangent small holes is satisfiedRimed turbine blisks with complicated curves made of difficult-to-cut material is the typical part in five-axis linkage moulding EDM. Based on the specification of EDM for rimed turbine blisks and the simplified error model, the general scheme of five-axis linkage EDM machine tool are determined and design indexes of main parts are proposed in the paper. For improving geometric motion accuracy of machine tools, a compensation algorithm of interval division is proposed in the paper. Uniform compensation in the whole compensation field can be obtained by the algorithm and precision error at any point in the field can reach the minimum. Positioning accuracy compensation to the C axis of five-axis linkage EDM machine tool is accomplished to vertify correction of the algorithm.Off-line pose adjustment and measurement for complicated electrodes are an efficacious method and a beneficial supplement respectively in improving production period of rimed turbine blisks. Based on requirements of pose adjustment and measurement for complicated electrodes and the simplified error model, the presetting system for complicated electrode faced to rimed turbine blisks based on electric figure measuring method is developed to make electrode measurement and manufacturing process uniform. A low-voltage circuit for measuring figure, of which the repetitive positioning accuracy can arrive at 2μm, is designed in the paper so as to measure surfaces with high repetitive positioning accuracy and avoid damage of electrode surface in measuring procedure. UG secondary development function is used to obtain the information of sample points on measurement surfaces as complicated electrode models are known and the information of obstacle-avoiding points and the planned measuring path are generated according to the information of sample points. Mathematic and measured points of the same section line are fitted by cubic uniform B-spline curve on the same coordinate system and approximate corresponding points (optical points) to mathematic points are obtained on the measured curve by using the Newton 1-D optimizing method when measured points are used as initial iteration points. By comparing the projection of length between mathematic and optical points on the normal line at mathematic points with design tolerance of electrode surfaces, qualification of complicated electrodes is decided finally.Numerous TC4 process experiments, machining experiments for tangent small holes and multi-axis linkage micro-milling are carried out on the developed five-axis linkage micro-EDM machine tool. The experiment of pose adjustment and measurement for a certain complicated electrode is carried out and an EDM experiment for rimed turbine blisks is implemented with qualified electrodes.