Research On Adaptive NC Machining For The Root Area Of A Welded Impeller

Impeller is a key component in aircraft engine.The welded impellers is widely used with the improvement of engine performance requirements.Because it can bring many advantages such as decreasing the part quantities and weight of impeller,avoiding the air flow loss,making the engine structure greatly simplified and improving the efficiency of pneumatic,but its special structure form has brought great difficulties for welded impeller′s manufacturing.To solve the problem,the paper researches an adaptive NC machining technology,which contains contact measurement,the blank impeller root area surface adaptive reconfiguration based on the measured data and the tool path regenerating of reconstruct blank surface,etc.And the paper proposes an on-line measurement program generation algorithm,which can be performed on a style of AC dual-table Five-axis linkage CNC machine.And an adaptive reconstruction surface algorithm,which based on the measurement data with the root area of original theory surface.And a tool path generation and optimization algorithm based on surface mapping.These algorithms can solve the problem of "steps",over cutting produced by machining the welded impeller in traditional NC machining technology,and the problem of being unable to generate the blade root area machining tool path with efficiently and automatically.The paper′s main research as follows:(1)The research on on-line measurement technology based on a style of AC dual-table Five-axis linkage CNC machine.The main content contains probe setting,measure points sampling,measure paths planing and on-line measurement program generating,etc.We can use the measurement program to measure the root area of blade,and then let the measurement data be processed.At last,we can get the actual measurement data of welded impeller′s root area.(2)The research on curve and surface modeling.For curve modeling,this paper adopts cubic curve with tolerance constrained to fit measure data.In this way,the curve can through these actual points as soon as possible,and the curve can be modeled with fairing.For surface modeling,this paper selects a welded internal theory section curve and two actual measured curve to compose the adaptable surface of the root area.(3)The research on tool path regeneration based on parametric surface mapping.First according to the characteristics of the blade surface,the mapping relation between the theory surface H_d and adaptive surface is established by UV parameter domain based on section line.Second,by mapping the coordinate of tool path,the machining tool path of adaptive surface can be obtained.And then thepaper puts forward a method and algorithm,the method can adjust the length of tool path based on chord error comparison and make the max tool path error meet requirements,the algorithm can smooth tool vector based on a second order continuous of local tool orientation and make the variation of tool vector meet the requirements.Finally,The paper finished the measuring and processing experiments of welded impeller by using the adaptive processing system.The measuring program and generating code produced by the system were verified reliability,and the algorithms were verified effectively.