Plunge Milling Of The Semi-open Integral Impeller With Fixed Rotating Axis

As a type of energy conversion machine, turbomachinery is widely used for many industries, such as transport industry, aerospace industry, petrochemical industry, which occupies an important place in the national economy. Impeller is the core component of turbomachinery, so in order to enhance industry competition ability and improve the development of national economy, it is essential to improve the design and manufacture methods of impeller. Impeller machining involves many aspects, academy and enterprises have taken a great deal of research from different aspects, but improving the processing efficiency at the stage of rough machining is always a difficult problem. Plunge milling with fixed rotating axis, a high-efficiency processing method, was used in this thesis and targets integral impeller, which based on the maximum tool-path planning area. In order to further improve efficiency, the method of taken segmentation channel width as the standard is proposed, and gives a method to divide the impeller channel at the part of same width between the channel hub and shroud. Each segmentation is optimized for choosing different tools and tool axis direction for processing in each segment. Main content of the thesis includes:First of all, Construction idea of the impeller digital model was given, then B-splint curve, ruled surface and ruled surface used for the model construction was introduced. During the modeling, algorithm and principles were given through theoretical derivations and analyses. Based on above works, the impeller digital model was constructed.In order to remove machining allowance quickly at the stage of rough machining of the impeller, the more efficient method of the plunge milling with fixed rotational axes of machine tool is used. Considering the envelope surface of the plunge milling cutter is a general cylindrical surface, an optimization model for maximizing the bottom area of the cylindrical surface is established. The bottom area is constructed by intersecting an impeller tunnel with a number of half-planes and then projecting the intersecting curves on a given plane whose normal vector is same as the tool axis of the plunge milling cutter. Under the condition of meeting the needs of engineering, the optimization model was predigested based on related algorithm. The optimal direction of the tool-axis is obtained by solving this optimization model with the Matlab software.For the situation of segmentation channel processing has no generic algorithm, the method of taken segmentation channel width as the standard is proposed, and gives a method to divide the impeller channel at the part of same width between the channel hub and shroud. Each segmentation is optimized for choosing different tools and tool axis direction for processing in each segment. Finally, case study simulation validates the correctness and the effectiveness of the presented method.Using UG software to complete semi-finishing and finishing machining of the blades, finishing machining of the hub, clean-up machining.At last, The orthogonal test of four factors at three different levels was used in this paper. Data are analyzed by extreme difference analysis method, some suggestions about cutting parameters selection are put forward based on analysis result.