Research On Milling-Grinding Compound Machining Method For Large Marine Propeller

The marine propeller is the key component for propelling ships.Its manufacturing efficiency and machining accuracy directly determine the safety and stability of the ship.As a kind of complex surface parts,the traditional processing of large marine propellers is mainly a combination of manual shovel and manual grinding,which has the disadvantages of long processing cycle,poor operating environment and processing accuracy depending on the manual skill of the workers and the surface quality is difficult to control.With the advancement of science and technology,the universal use of NC machine tools has gradually replaced the backward manual processing.In recent years,with the rapid development of shipbuilding industry,higher requirements have been put forward for the processing efficiency and accuracy of marine propellers.There is an urgent need for both new digital processing equipments and methods to replace the existing processing methods and improve the processing efficiency and accuracy of large marine propellers.Therefore,this paper proposes a measurement-processing integration processing method.By means of online scanning measurement,data model matching,extracting processing allowance and other methods,based on the distribution of blank allowance obtained,the goal of obtaining large marine propeller products by one-time clamping of the propeller blank is achieved by using milling-grinding compound processing machine tool.The main research work is as follows:1.The structural characteristics and processing requirements of large marine propellers are analyzed,and the overall processing scheme of propellers is worked out.The large-scale marine propeller milling-grinding compound machine tool is determined,the main data measuring equipment is analyzed,and the suitable measuring equipment is selected according to the research content of this subject,and the NC equipment integrating measurement and processing is established.2.The commonly used path planning methods are introduced,and according to the actual situation,the appropriate path planning method of large marine propellers is chosen.The geometric relationship between the linear residual deviation caused by linear interpolation and the machining step length and the travel line distance during the machining process is analyzed.Based on this,the calculation method of the step size and the machining line spacing is studied.The tool contact data are determined according to the step size and the machining line spacing.In addition,the allowance extraction method of large propeller blank is studied.The point cloud data obtained by scanning is matched with the theoretical model,and the allowance distribution of each cutter contact point is obtained by matching and comparison.According to the allowance distribution,the tool path is redesigned to reduce the number of empty cutters and the processing efficiency is improved.3.The processing algorithm and control method of large marine propeller are studied.A tool attitude optimization method is proposed for the interference problem that may occur during the milling process which optimizes the tool machining curve to make it smoother while avoiding interference problems.Relying on the floating pressure grinding head,considering the influence of the process parameters on the processing quality during the polishing and grinding process,the removal model of the material is established to obtain reasonable process parameters.Based on Open CASCADE software platform and objectoriented C++ programming language,a special software for milling and grinding of large marine propeller is developed.The software can realize off-line tool position calculation,tool path optimization calculation,propeller allowance extraction and generate NC machining program according to the allowance distribution.4.Processing simulation is carried out on VERICUT simulation platform to verify the correctness of the program generated by the large marine propeller milling-grinding compound processing software.And the program is used to carry out actual processing experiments,and the experimental results are tested and analyzed to verify the practicability and reliability of the milling-grinding compound machining method and algorithm for large marine propeller.