Research On Key Technologies Of Shape Control And Machinability Control In Numerical Control Machining Of Marine Fixed Pitch Propeller

The fixed pitch propeller is an important part of the ship’s propulsion system.The processing of the freeform surface blade structure is difficult,and the multi-axis numerical control programming and processing technology has provided the conditions for its numerical control processing after years of development.However,in the current NC machining programming environment,the machining programming shape precision of the propeller is poor,and the blanks in different regions and different qualities cannot be adjusted adaptively.The cutting parameters during machining are also mostly selected based on experience.Therefore,it is necessary to further study the shape control and cutting performance control technology in the numerical control machining of marine fixed pitch propellers to improve the processing level.Based on theoretical analysis and experimental research,this paper combines software development programming to analyze and optimize the shape and cutting performance influencing factors of the numerical control programming and machining of the propeller,and to improve the processing quality.The main research content are as follows:Firstly,the structural features and design methods of the fixed pitch propeller are analyzed,and the automatic transformation of the type value table of the propeller section from two-dimensional to space cylindrical coordinates is completed by programming,and the rapid modeling is realized.Through the transformation of the model’s blade thickness data,the difficulty of modeling the blade back surface of the propeller blank model and the difficulty in the detection of the blade thickness are solved,and the shape precision of the workpiece is guaranteed for the numerical control programming.Secondly,aiming at the current general NC programming technology,a special programming process is developed to fit the surface characteristics of fixed pitch propeller.The particle swarm optimization algorithm is used to realize the shape control of the propeller and optimize the machining allowance;After the analysis of the distribution range of each data point,the machining layer is calculated and the large margin region in each machining layer is divided;The optimal programming environment and programming parameters are selected by combining the structural features of the free form surface.At last,a special programming template is developed to achieve flexible control and rapid programming of the propeller processing area.Thirdly,the stability analysis of the milling system with fixed pitch propeller is carried out and the stable region is solved,thus the selection range of the cutting parameters is determined so as to prevent the flutter during the milling process.In view of the complex structure of propeller blades and unequal distribution of blade thickness,different parts are applied to different dynamic models for adaptive analysis to improve the reliability of the stable region.Finally,the effect of the single cutting parameters and multiple cutting parameters on the surface quality of the workpiece and the cutting force in the milling process is studied through the material cutting experiment,which provides a reference for the selection of nickel aluminum bronze alloy propeller cutting parameters.