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Five-axis machining of integral impeller

The overall machining of the impeller uses the hub and blades to be formed on a single blank, rather than the process of forming the blades and then welding them to the hub. Its processing technology plan is as follows:

1. In order to improve the strength of the overall impeller, the blank is generally made of forged parts, and then the reference surface is turned to process the basic shape of the impeller rotary body. The blank of the air compressor rotor is shown in Figure 3.

2. The position of the groove for grooving the impeller airflow channel should be selected in the middle of the airflow channel. Use a flat-bottomed tapered shank rod milling cutter to run parallel to the airflow channel, and ensure that there is a certain processing margin between the bottom of the groove and the surface of the hub. As shown in Figure 4.

Among them, the flat-bottom taper shank rod milling cutter is a carbide tool. Its specifications are: the diameter of the flat bottom part is: 3mm, the half-cone angle is 2°, the diameter of the tool shank is: 6mm, and the length of the tapered part is: 20mm. The spindle speed selected in this step is: 10000r/min, and the feed speed is: 800mm/min. The control panel of CNC machine tools is generally equipped with spindle speed and feed speed adjustment (override) switches, which can adjust the spindle speed and feed speed according to the actual processing conditions during the machining process.

3. The grooving process of the impeller airflow channel and the rough machining of the blades are performed using a spherical tapered shank rod milling cutter. Starting from the grooving position, the grooves are expanded from the center to the outer edge to the blades on both sides. The grooving process must ensure that the blade shape is retained. There is a certain finishing allowance. Normally, groove expansion and finish milling of the hub surface are completed in one process. Since this impeller has narrow channels, high blades, and severe distortion, and the UG CNC machining programming needs to determine the cutting area based on the driving surface, the groove expansion process needs to be processed in two parts. Part One: Select the driving surface as the hub surface and expand the groove. At this time, the surface of the hub cannot be processed, and further groove expansion processing is required; the second part: further groove expansion and rough machining of the blades. The driving surface is selected as the offset surface of the blade surface, and the groove is further expanded while the blade is roughed. Among them, the spherical taper shank rod milling cutter is a carbide tool. Its specifications are: the diameter of the ball head part is: 3mm, the half taper angle is 2°, the diameter of the tool shank is: 6mm, and the length of the tapered part is: 20mm. The spindle speed selected in this step is: 20000r/min, and the feed speed is: 3000mm/min.

4. The finishing of blades and hubs is carried out with a uniform margin to ensure good surface processing quality. Ball end milling cutters are used for finishing because the minimum distance between adjacent blades is 3.1mm, and the deepest part of the blade is 17.15mm. Considering interference, the rotor finishing tool uses a 2.5-diameter ball-end milling cutter from the Swiss Fraisa company, and the tool clearance is 20mm. The spindle speed during processing is: 260000r/min, and the feed speed is: 5000mm/min.

5. Variable fillet finishing: The left side of the large and small blades is variable fillet. The fillet radius changes linearly from the leading edge to the trailing edge of the blade from 1.25mm to 2.2mm to 1.25mm. The maximum fillet occurs at 22% close to the trailing edge. The right side of the blade has a constant fillet of 1.25mm. The radius of the corner can be completed by one tool pass. At this time, the radius of the ball head part of the tool is at least the minimum radius of the radius of the corner. Select the tool, spindle speed, feed speed, and finish machining of the blade and hub. The above procedures must go through indexing and rotation, and the entire hub or blade must be processed before the next procedure is executed to ensure uniform stress release and reduce processing deformation errors.

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