Error Analysis And Parameter Optimization Of Visual Inspection Device For Casting Turbine Blades

Turbine blades work in high temperature,high pressure and high speed.In order to adapt to the harsh environment,turbine blades are made of hard alloy materials such as titanium alloy and nickel base alloy.The structure of the turbine blades is complex,and they have large thin edge and cross-section,which is easy to deform when casting,and the blade profile can not meet the design requirements.The key to ensure the quality of the casting turbine blades is to inspect them accurately.The existing contact measurement methods have low efficiency and low precision.For the non-contact measurement of the blades,this paper is devoted to parameter error of line structured light vision sensor,the geometric error model and the method to improve the accuracy of visual inspection device,including:(1)Error modeling and parameter optimization of line structured light vision sensor.Based on the principle of laser triangulation,a mathematical model was established to obtain the imaging formula of the line structured light vision sensor.The optimum structure parameters of the sensor were calculated by control variable method.The installation angle,the installation method and the installation distance were optimized to improve the measurement accuracy of the sensor.The relationship between the sensor surface and the image plane was established,the measurement range and the measurement depth of field were taken as constraint condition to optimize the structure parameters of the sensor.After optimization,the average measurement error of the standard ball was improved to 0.0206 mm.(2)Geometric error analysis of visual inspection device for the casting turbine blades.The geometrical errors such as installation error,manufacturing error and motion error were analyzed respectively.The influence of each error on the inspection accuracy was pointed out,and the maximum allowable value of the geometric deviation of the device was calculated by the turbine blade.The laser tracker and industrial gasket were used to adjust the geometrical structure of this inspection device,which was to ensure verticality of translational axis and blade,rotational axis and blade.After optimization of the structure,the average measurement error of the standard ball was increased to 0.0301 mm.(3)The measurement experiment of precision stability when the device was under environmental vibration.According to the national standard,environmental vibration conditions of the inspection device can be determined.The modal frequency can be analyzed by combining with material characteristics of the device,and the most affected location of device was found out by ADAMS.On this basis,the vibration test platform can be set up,and the vibration signal of horizontal direction and vertical direction was applied by an exciter.At the same time,the calibration accuracy of the device was calibrated with the standard ball,which tested precision stability of the device in environmental vibration.(4)Measurement experiment of visual inspection device for casting turbine blades.According to the German VDI/VDE standard,precision of the visual inspection device can be evaluated by standard double ball.Two different blades were measured,and analysis of the blade profile by a software which is named iCloud3 D.“Surface scanning-Data Processing-Error calculation” of a single blade only needs 3min,which greatly improved the inspection efficiency and the level of automation.