Robotic Precision Grinding Of Engine Blade Surface

The quality of the airfoil surface of aero-engine blades has an important impact on the engine's overall performance.The complex blade shape design meets the continuous improvement of the aerodynamic requirements of the blades,and also brings great difficulties to the blade processing and manufacturing.The use of a dedicated blade CNC grinding machine has improved the efficiency and accuracy of blade machining.However,due to the wide variety of blades and most of them are constantly improving and changing,the dedicated blade CNC grinding machines are still difficult to adapt to all blades grinding processes.The use of articulated robots for the machining of aero-engine blades has attracted attention in the field.The application of robots for blade surface grinding has certain technical advantages for blades processing,so this technology has good development prospects.To meet the needs of aero-engine blades manufacturing technology development,this dissertation carried out research on the aero-engine blades robot precision grinding processing related theories and its key technologies.The main research contents and results are as follows.(1)The surface quality and micro-topography characteristics of engine blades was described based on the surface roughness model theory.Through numerical simulation,flow field analysis was performed on a flat blade cascade of a certain type blade,and wall functions at different interfaces between the blade and the airflow were set to obtain several sets of calculation results.Comparing these results with the simulation value of the blade flow field on a smooth surface,a surface roughness value that took into account both blade performance and economic benefits was obtained.According to the principle of blade forming and the geometric characteristics of the blade stacking surface,the processing errors of the blades were studied,the forms and locations of these errors were analyzed,and the possibility of the lack of processing methods becoming the source of errors was pointed out.The plane cascade of the elementary stage of the second-stage compressor of anaero-engine was selected as the research object,and the negative effects caused by various errors were quantitatively analyzed by numerical calculation.(2)The technical method of sub-area grinding of the blade was investigated based on the robot,and the robot's execution end was used to fit the complex surface of the blade to complete the grinding of the blade blank.The spline curve was used to fit the contour curve of the blade blank,and the attributes of the processed area were judged according to the curvature of the blade cross-sectional profile,so as to divide the processed area.This dissertation studied the working mode of a robot holding a grinding tool or a blade workpiece.According to different blades and different processing requirements,four robot-based blade surface grinding schemes and their robot layout schemes were proposed.The space surface fitting and path planning techniques based on robot blade surface grinding were experimentally verified.(3)The contact form and contact force during blade surface grinding were researched on from two aspects,macro-scale and micro-scale.At the macro scale aspect,a contact model of blade surface and grinding tools based on contact theory was proposed.At the micro scale aspect,the blade surface micro elements with milling texture and the grinding tool micro elements with abrasive particle groups were selected for research.The related mathematical model was established theoretically,and the contact force was simulated and analyzed using numerical simulation methods.The behavior characteristics of the abrasive grains were studied.The stress and deformation of the abrasive grains during the grinding process and the behaviors of escape failure were expounded by using the dilatancy theory.A measuring device for the contact force between the contact wheel of the abrasive belt machine and the blade surface was established,and the blade grinding experiments were performed based on the working mode of the robot holding a small belt sander and the positioner holding the blade.(4)For the grinding tools that process blades for a long time,the attenuation factors of the abrasive particles' ability to remove materials were studied to ensure the consistency of the blade surface quality.The life of the grinding tool was determined according to the degree of the abrasive particles wear.The wear process of the abrasive grains was divided into three stages.The grinding capabilities of the abrasive grains in the three stages were numerically analyzed.The numerical values obtained by the simulation were substituted into the parameter model,which could calculate the parameters predicted by the model.Then,the measured parameter values wereobtained through experiments,and they were compared with the simulation values to evaluate the stability and accuracy of the parameter model.