2. Runner processing
Main parts processing points: The water bucket is the key part of the runner. The bucket shape and the tail and tail of the bucket must be processed and repaired in strict accordance with the airfoil requirements. The final effect of the processing will be directly related to the mechanical strength and hydraulic power of the runner. Performance, affecting unit output and rotor erosion. The focus of this process will focus on the overall processing of the rotary water bucket and the overall processing size of the workpiece. The processing process is as follows:
(1) After the casting wheel of the whole casting wheel is inspected, the whole casting wheel is affected by the casting technology, and the overall shape and size data is irregular. The inspection before the CNC machining is one of the key points to ensure the processing quality. The Fiji runner uses a combination of manual scribing and FARO measuring equipment to determine the machining center and machining allowance at the center and each part and to check the machining allowance inside and outside each bucket (see Figure 2).
figure 2
In the figure, D is cut to be tangent to the end face of the bucket (240.3mm), D1 is the pitch diameter (1 700mm), and L 1 is the vertical distance from the center of the bucket to the pitch circle.
(2) Rotor processing process The simple process of runner processing is as follows: draw center line, reference line, and check machining allowance → upper NCφ 2.5m vertical semi-finished car, fine car round and plane → upper small dragon door milling, The upper part of the back of the rough and fine milling bucket, the upper part of the upper part of the rough milling front and the water dividing edge → 90° in the cross direction, the adjacent screw hole is the same as the drilling hinge pin hole → the lower part of the back of the rough milling bucket Part, rough milling front lower half end face and water dividing edge → upper NCφ 160mm boring machine, rough, fine milling water bucket front and front and back intersection, the rest of the milling bucket. The same hinge of the runner and the milling tire is shown in Figure 3.
Figure 3 Rotating and milling tires
After the runner finishes the vehicle, it is aligned according to the groove and the hub plane. The NC gantry milling (three-axis) and NCφ 1.6m vertical boring and milling machine (three-axis) rough milling, finishing the water bucket on the front and the water bucket are divided. The edge of the blade is 180.7mm. According to the structure of the Fiji runner, in order to ensure the accuracy of the positioning of the steering wheel after the turning over, the runner and the milling tire are combined and placed in the same direction as the 90° adjacent joint screw hole in the cross direction. Processing pin. On-site processing is shown in Figure 4.
Figure 4
The processing on the back of the bucket is done by three-axis small-gantry milling. The front, front and back of the bucket and the rest of the machining are completed by the NCφ 160mm boring machine. Plunge milling is used for roughing. When inserting and milling the water bucket blade, it can be milled from the top of the workpiece to the root of the workpiece. When inserting and milling, the cutting edge of the milling cutter is made up of the contours of the blades. The depth of the milling can reach 250mm without vibration. Trembling or distortion, the cutting direction of the tool relative to the workpiece can be either downward or upward, but generally it is more common to cut down. When the bevel is milled, the plunge cutter moves in a combined motion along the Z and X axes. Finishing is done by ball end mills and copy milling cutters. When programming CNC machining, pay attention to the following aspects.
First, the tool should be slowly cut in and out of the workpiece. This prevents the tool from being deflected due to the sudden increase in cutting force, which causes the tool to break or chip.
Second, all tool rails should be smooth and continuous. This is good for extending tool life, reducing spindle vibration, and increasing machining productivity.
The feed rate and radial depth of cut should be as uniform as possible, which is beneficial to improve tool life and reduce frequent noise pollution.
Third, in the roughing process, in order to ensure maximum cutting efficiency, the planned tool path should be able to adapt to constant speed feed. In the finishing process, in order to improve the surface quality of the machine, the generated tool path keeps the tool cut with constant force. In high-speed milling, different programming strategies should be used for different part materials and shapes.
In the whole process of roughing and finishing, the three factors of cutting depth, feed rate and cutting speed should be coordinated to achieve higher cutting efficiency and processing quality under the conditions of cutting force and tool life.
When milling, asymmetric milling is used to control the plunging angle and the cutting angle, which has a great influence on reducing the number of impacts and impacts of the tool, which is beneficial to improve the tool life. In order to improve the processing efficiency, ensure the machining accuracy and the quality of the profile, the tool is selected, the cutting mode and the tool axis control mode are determined.
3. Conclusion
The Fiji 1# water bucket wheel CNC machining was successfully completed. The shape, inner surface, outer surface, end surface, water dividing edge and water cutting edge of the bucket have all passed the test. Special process measures taken throughout the processing process increase processing efficiency and reduce costs. Both in theory and in practice, we have accumulated rich work experience, laying a solid foundation for the processing of water bucket type runners. At the same time, it also filled the blank of the company's whole-cast CNC machining water bucket, and enhanced our company's impact type. The competitiveness of the turbine market.
