Research On Evolutionary Modeling Method For Multi-form Intermediate Process Models And Its Application

In recent years,the aviation industry has rapidly developed in our country,and the CNC programming task in aviation product research and production is getting more and more heavy.At present,a large number of addendum surfaces and intermediate characteristics that require in the CNC programming for complex integral structure still rely on artificial design,but the low efficiency and long cycle in the CNC programming becomes the bottleneck problem which restricts the delivery of aviation product manufacturing task.This thesis takes the automatic generation of intermediate characteristics for aviation complex parts in multi-axis machining as research objects,a in-deep research in the evolutionary modeling method for multi-form intermediate process models and its application has been conducted in this thesis.The main contents and innovative achievements are as follows:(1)Aimed at the representation of intermediate surfaces,a modeling method of process models based on morphing technology is presented.Firstly,the multi-form intermediate process models and its evolution concept are introduced,and the morphing technology to build intermediate surfaces in NC machining is given.Secondly,a boundary surface discretization method based on the non-equidistant parallel interception for complex machining characteristics is proposed.On this basis,the modeling procedure and the key algorithm of morphing for surface entities are given,and the verification is conducted on the parts of impeller and casing.(2)Aimed at the design of intermediate surfaces,a design method of process models with process constraint is presented.The design method of intermediate surfaces is proposed based on the blending function constraint and the virtual control surface constraint respectively,which is able to control the interlayer allowance distribution and geometry change of intermediate surfaces.On this basis,a selection method of process models based on the constraint of tool cutting depth is given,and the process intermediate surfaces of impeller channel machining with process constraint are constructed.The simulation result indicates that the presented method can avoid self-intersection problem in approximation equidistant surface offset method,also can obtain the intermediate surface which satisfies the manufacturability requirement and has the features of with constraint,controllable and devisable.(3)Aimed at the distribution mode optimization of intermediate surfaces,a synchronous optimization method about the tool sequence and the distribution mode of multi-form intermediate surfaces is proposed.Through introducing the cutter size as the parameter,an optimization mathematical model about distribution mode of intermediate surfaces takes the minimum processing time as optimization goal and cutting depth as main constraints is established,and a two-step method of calculation the largest cuter set and optimization cutter tool sequence is given for solving this optimization model.Taking impeller as an example,the optimized distribution of process surfaces for impeller channel machining is calculated.A comparison of machining on the optimized and unoptimized process surfaces is carried out.The result shows that the optimization method presented in this thesis reduces the total processing time by 111.7 seconds and improves the machining efficiency by 5.96%for a single impeller channel.(4)Aimed at how to optimize the cutting order for the multi-form intermediate process surfaces,a tool path definition and generation method of single processing area based on template is established,and a cutting order optimization method based on the breadth-first algorithm for different processing areas is presented.Firstly,the single-parameter curves characterization method of the trajectory template in the uv plane is given,and the trajectory template is mapped to the physical domain to calculate the continuous tool path on the process surface.Secondly,under the condition of determining the cutting path on single processing area,an optimization model about cutting order with the shortest total tool path as the main goal is established,and a solving method based on the tabu search algorithm is given to calculate the optimization model.Finally,taking the simulation processing and machining experiment of casing as example,the result shows that the optimization method presented in this thesis optimizes the cutting order and engage or retract position,reduces the lifting times and vacant path.