Multi-axis Machining NC Tool Path Generation For Centrifugal Impeller

In this thesis, the geometric modeling and Numerical Control (NC) machining of centrifugal impeller, which has long and short blades on the channel one by one, are analysed and studied. The researching works include B-Spline surface modeling of blades, merging of short blade edge, finding intersection between surfaces, and NC tool path generation for the channel of this kind of centrifugal impeller. The main works are as follows:1. Build the blades' model using the algorithms of non-uniform B-spline surface, and build the channel's model through rotating the long vane's bottom boundary. Embedding Matlab7.0 environment, the centrifugal impeller can be demonstrated.2. By analysing the known datas, the two sides of blade are separated, merging these two sides smoothly is necessary. Firstly, this thesis gives two ways to solve this problem: Fergusson parametric cubic surface method and energy minimization method, and analyses the advantages and disadvantages of these two methods. At last, this thesis proposes a new method, which is based on Fergusson cubic curve, can obtain the merging surface indirectly but highly effectively.3. Finding intersection between surfaces is widely applied in surface clip, NC tool path generation and 3D modeling. This thesis uses the idea of disperse - iteration - track to obtain the intersection curves between two surfaces. This method can be used in the modeling and NC tool path generation of centrifugal impeller's channel, and the result is satisfied.4. In this thesis, two methods for NC tool path generation for the channel of centrifugal impeller are proposed. The first one is an improved method of old algorithm that using short blade to cut original tool path, this method has solve the problems existed before. The second one is a new method, the channel is considered as two blocks, for each block, the tool path is generated seperataly, this new method works well when evading the island and uplifting the tool, and has high efficiency.5. Carry on the NC machining experiments for the two new methods of tool path generation. The methods have been proved available.