Measurement-Grinding Intergrated Manufacturing Method And Technology For Large Propeller Blades

As far as large-scale,moderm marine equipment is concerned,one of the key factors that would affect the efficiency and processing noise of ship power system is propeller blade shape and manufacturing accuracy.However,in the case of large marine propeller manufacturing,manual grinding method is usually adopted in the finishing machining process,which is time consuming;while the quality of products processed by this kind of processing method is quite poor.Therefore,a new processing method and numerical control machine tools are needed to replace the traditional processing methods,so as to realize the digital finishing machining of large propeller blades.In this paper,measurement-grinding-manufacturing method and technology for large propeller blades is devoted.As for the related technical problems,a series of key technology research work have been carried out.The details of the studies are shown as follows:A measurement-grinding-manufacturing method for large propeller blades is proposed.The machining localization of propeller blade is realized through measurement and registration.The machining parameters are modified based on the machining allowance distribution model.The abrasive belt grinding is adopted as the machining method to realize digital processing of large propeller blades.Firstly,in order to improve the measurement efficiency and accuracy of the large free-form surface,an investigation is carried out for the measuring methods of fast laser scanning of the free-form curve which deformed through cross section line.A bidirectional mixed prediction method is proposed for the measurement of unknown surfaces.This method can be used to estimate the position and the normal direction of the unknown surface model in advance.By using the support vector regression method and orthogonal experiment,the relationship between the angle of the estimated normal and the incident light,the distance between the measurement and the measurement error are established.A surface registration method based on particle swarm optimization is proposed for the registration of the measurement model and the design model.In order to ensure that the machining allowance is distributed evenly,the uniform distribution optimization algorithm is proposed.Secondly,because of the difficulty in guaranteeing the machining accuracy of the large workpiece,a new information-localization strategy for machining large thin-walled parts is presented.A method of large scale workpiece partition processing and related reference point measurement is proposed.This strategy uses sub-areas and fiducials calibration methods to improve processing precision of large parts,which are of poor machinability,low rigidity,and poor deformation coupling.Each divided sub-area is calibrated by the machining benchmark fiducials.In each sub-area,a modified model for the correction of the associated fiducials is established.Based on the studies of marine propeller material,single factor experiment is carried out to study the influence of grinding process parameters(abrasive grain size,grinding speed,grinding depth and feed rate)on the surface integrity(surface roughness,grinding force,material removal amount,and residual stress)of casting aluminum bronze alloy.After the grinding-polishing process,the surface topography and composition of surface were analyzed.The results will be beneficial for the finish machining of propeller blades.Thirdly,in order to control the removal amount of the material precisely in the grinding process,the relationship between the contact pressure,dwell time and material removal had been analyzed.Finite element method and Hertz contact theory are used to study the contact stress distribution between the contact wheel and the workpiece.Then,a controllable material removal strategy considering force-geometry model of belt grinding processes had been proposed.According to the workpiece geometry model,this strategy successfully achieved the precise control of material removal amount by controlling the contact pressure and dwell time.Besides,in five-axis CNC abrasive belt grinding machines,machining errors occurred due to the deformation of the contact wheel.To overcome this issue,an effective method based on the second-order osculation principle is proposed for grinding free from surface.In this method,considering the characteristics of belt grinding,the contact wheel posture is adjusted at grinding point to reduce grinding errors.Based on the obtained optimal feed direction,the maximum width of the grinding belt is worked out to improve efficiency.In brief,a grinding-polishing device integrated with measurement and manufacture for propeller blade is developed.The measurement,grinding and polishing of all blades have been completed while the parts were loaded.A flexible automatic clamping system for various types of marine propellers is invented.An integrated control system with measurement and manufacture is developed.