Parametric Modeling And CNC Machining Of Marine Propellers

Marine propeller is the core of the ship’s power system,and its blade surface is a typical free-form surface.The quality of the design and machining directly affects the performance of the propeller,and the complex working environment of propeller also requires higher modeling and manufacturing precision.The process from design to processing of marine propellers is complicated and tedious,and the cycle is long.Therefore,it is necessary to establish a parameterized mathematical model of the propeller that can comprehensively consider the design,analysis,and processing of the propeller.Based on the parameterized model,various subsequent researches on the propeller are carried out so as to shorten the design and manufacturing cycle of the propeller and improve production efficiency.In this paper,a parameterized equation of the blade surface of the propeller is established for the purpose of achieving the parameterized design to NC machining of the propeller.3D solid model of the propeller was established based on the points obtained by the parametric equations;The structural parameters of propeller are optimized for the purpose of improving the propeller open water efficiency,and the simulation of the hydrodynamic performance of the propeller was performed;The CNC machining process of the propeller was analyzed and formulated.The NC machining program was compiled based on the parametric model and the NC machining simulation and experiments was verified.The details are as follows:Based on the analysis of the structure and forming principle of the marine propeller,the parameter equation of the propeller section is established.The coordinate conversion formula of the two-dimensional section to the three-dimensional space is derived,and the overall parameterization of the blade surface is realized.The data points under the specified precision of the blade surface are calculated and imported into the UG to establish a three-dimensional solid model.Compared with the propeller model established by the traditional point value,the surface of the propeller model established by the parametric method is better.Taking the maximum open water efficiency of the propeller as the goal,the parameters of the propeller surface ratio,pitch ratio and speed coefficient were optimized,and the best matching parameters under the specified conditions of the propeller were obtained.The open water efficiency of optimized propeller is increased by approximately 3.18%.The hydraulic performance of the propeller was simulated and the open water efficiency of the propeller was verified.The influence of pitch angle and side slope on open water performance of propeller is analyzed.The propeller CNC machining process was analyzed.The processing stages are divided,and the blanks,tools,and cutting methods are determined.The interference and overcutting during processing are judged and the geometric relationship between the tool and the workpiece is established.The non-interference tool path algorithm is studied.The tool path for roughing and finishing are calculated based on the parameterized model,and the tool position is converted into a CNC machining program by post processing.The numerical control machining simulation environment was established,and the numerical control machining program was introduced to carry out numerical control machining simulation.The tool path and the NC program simulation were verify by simulation,and the propeller achieves a good surface quality.Finally,machining experiments were performed on a five-axis CNC machine.The parametric model established in this paper has achieved good results in propeller optimization analysis and numerical control machining.Based on the the NC machining method of parametric mathematical Model,the CNC machining program can be obtained by modifying the parameters of the propeller within a certain parameter range,which has a large engineering application prospects.