Developable Surface Approximation For Impeller Blade Surface And Rough Machining Area Planning

As a type of representative channel parts with sculptured surface, impellers are widely used in aviation, aerospace, nuclear power, energy power, petroleum chemical industry and so on. In three dimensional twisted blade impeller machining, around80%of the processing time is spent on rough machining. In order to reduce the time needed for rough machining of impeller, improve production efficiency, impeller rough machining area planning problem is studies deeply in the paper. The objects modeled with developable surface can be manufactured without tensile and tearing material, which makes the objects modeled with developable surface has good processing properties, so research on that impeller vane surfaces are approximated by developable surface is of great significance in improving the impeller machining precision and so on.First of all, through the MATLAB software, the use of quasi-uniform B-spline interpolation algorithm, shaft plate line and cover plate line of suction surface and pressure surface are generated, and then suction surface and pressure surface are generated by the interpolation to their two boundary curves with Ruled Surface, thus impeller geometry modeling are finished;On this basis, approximation to impeller blade surface by developable surface is completed under the use of splicing technology between cylinder and cone, the corresponding theory and method is verified by MAT ALB software.Secondly, intersection problems between multistage b-spline curves are studied deeply in the paper. B-spline curve control polygon is optimized by using the optimization method of convex hull, and combined with using the rectangular test method and accurate intersection function, the intersecting operation between multistage b-spline curves is completed.Finally, the largest projection area of impeller flow channel is achieved in accordance with related knowledge on projection transformation and the rotating movement group. Thus the best projection direction is produced, and it is regarded as the direction of generatrix, corresponding projection curves are taken as directrix, then cylindrical surface is modeled. So the approximation to impeller passage by cylindrical surface is completed, and the goal of optimizing the impeller passage rough machining area is achieved.