The Research On Online Measurement And Allowance Calculate Of Large-sized Screw Propeller In NC Machining

The measurement of screw propeller is an important procedure in its manufacture. The surface of large-sized screw propeller is complex and the blank is difficult to fix. The traditional measurement by hand costs time, and the precision of examining is easily influenced by man-made factors. To realize the unification of measurement reference coordination and machine reference coordination, decrease positional error brought by repetitious fix, achieve the reasonable distribution of allowance, alleviate the labor intensity of operators, it is significance to develop the on-line measurement and calculation for screw propeller. The paper introduces a method of the on-line measurement——measure with gauge head on the machine and analysis result by software to solve the measurement and allowance estimate base on the studying of traditional measurement procedure of blades. The main works as follows: Two kinds of the feasible measurement procedure are provided in this thesis. The auto-layout of the measurement is realized, including the ascertaining of measurement bound, choosing measured nodes, planning measure path and so on. The math model of blank in state searching based on least square is established to solve the problems for screw propeller with many blades, including the estimate of allowances of blank, the correction z offset of blades, the offset of back rake and so on. When the objective function achieve excellently, the state of blank is in the reasonable location, and the allowance distribution is in good status. Using Genetic Algorithms the math model of blank in state searching is optimized and solved. To avoid converging to local extremum in searching process, enhance calculation efficiency and decrease process time simultaneously, the searching for excellent extremum of model is realized based on some research on improvement of genetic algorithms. An on-line measurement system of screw propeller for for special Lathe-Mill NC Machine with Seven-Five Axis is developed. The practicability and reliability of the algorithms are validated through experiment.