Application of Plunge Milling on Hydraulic Turbine Blades

Founded in 1951, Harbin Electric Machinery Co., Ltd. is a key enterprise producing large and medium-sized power generation equipment, large and medium-sized AC and DC motors and supporting control equipment. The main products are: turbines, hydro-generators, steam turbine generators, control equipment for power station main engines and large and medium-sized AC and DC motors. It has cooperation with more than 30 companies in 12 countries including Siemens, Westinghouse, Hitachi, Alstom and ABB. The company has more than 6,200 employees and has a total of more than 3,800 sets of equipment, including 309 high-precision equipment and 37 CNC equipment. It is a state-owned large-scale enterprise with an annual production capacity of 5,000 MW steam turbine generator, 2,500 MW hydro-generator unit and 600 MW AC and DC motor. At present, hydropower units are provided for large-scale water conservancy projects such as the Three Gorges of the Yangtze River and Gezhouba.

The milling of the turbine generator blades has always been a bottleneck affecting the blade processing efficiency. Since the blade blanks are castings, the dimensions are large (Fig. 1), and the blade skirts are all twisted curved structures. Generally, it must be processed on the five-axis CNC gantry milling. The original process adopts corn milling cutter side milling, the processing efficiency is very low, and it takes one or two days to process a blade. Moreover, due to the high price of the machine tool, the number of five-axis CNC milling machine milling machines is small, the working time is high, and the processing cost of the blade is further increased.

In order to solve this difficulty, Seco uses its own milling cutter, which not only improves the processing efficiency of the blade, but also realizes the machining on the three-wheel linkage CNC gantry milling machine, which greatly reduces the processing cost of the blade. Now the processing time of Seco's R220.79-8160-40 plunge cutter is shortened to 5-6 hours, and the processing range of the parts is also expanded.

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Seco's R22079-8160-40 Plunger


The processing material of the blade is usually martensitic stainless steel such as 1Cr13. The processing amount of the blade skirt is about 50 to 70 mm. The cutter head adopts R220.79-8160-40) insert milling cutter with diameter Ø160mm. The insert is combined with SCET120612T-M14, T250M and SCET120612T-M14, 620470. The cutting parameters are: V c =200 m/min. f z =0.1mm/t, a p =30mm, ae=70 mm, the machine tool is a three-axis linkage CNC milling machine (Figure 2).

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Figure 1 Turbine blade parts

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Figure 2 XKA2140 X 80A CNC Gantry Milling Machine


Since the three-axis linkage CNC gantry iron bed is widely used in China, it is easy to find a processing partner, which alleviates the processing pressure of the 5-axis CNC gantry milling machine in the factory, and also greatly improves the processing efficiency. At present, the plunge milling method has been applied to the processing of other parts.

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