For the impeller channel with relatively standardized shape, the three-dimensional machining with the section line method cannot be completed, so the five coordinate method is generally used in the machining. Next, let's introduce how the CNC machine tool processes the impeller channel.
1、 Analysis of the overall processing scheme of impeller
Impeller integral processing refers to the processing of the hub and blade on the same blank, rather than the process of welding the blade on the hub after processing and forming. In order to improve the mechanical strength of the impeller, the blank is generally reduced by forging, and then the datum plane is turned to process the basic shape of the impeller.
Then carry out the slotting processing of the impeller air flow channel. In the slotting processing, the slot position should be selected in the middle of the air flow channel, and the flat bottom taper shank rod milling cutter should be used to mill from the inside to the outside, and ensure that there is a certain machining allowance between the slot bottom and the wheel hub surface.
The third step is to expand the groove of the impeller air flow channel. The groove expansion processing and fine milling of the hub surface are completed in one processing, which not only has high processing efficiency, but also can ensure the processing requirements.
The last step is the finish machining of blade profile. Time shows that the finish machining and root cleaning of blade profile should be completed in one process, so as to ensure that there are no knife marks on the blade surface and the consistency of surface machining is good.
2、 Generation of tool path and calculation of tool position in blade finishing
The generation and in place calculation of blade finishing tool path is the basis of the generation of tool path for slotting and slotting. Therefore, the blade finishing algorithm is discussed first.
1. Tool position calculation method
The spherical taper handle rod milling and side milling are used for the finish machining of blade profile, which is completed in one process with root cleaning.
2. Tool path generation
As mentioned above, for this kind of impeller, the feed direction should be processed by punching the wheel center to the rim. When the step size is set to walk to step size, the discrete subdivision can be carried out according to the surface parameters, and the equal parameter step size calculation method can meet the requirements of side milling of blade profile. This is because during blade modeling, the data given in places with large curvature are dense, and there are more cutting segments after discretization by equal parameter length method. In this way, the roughness and consistency of machining are good. How big the parameter step is depends on the size of impeller and the form of blade profile data.
If the equal parameter step method is adopted for discretization, the tool path needs to be graphically displayed to observe whether the distribution of tool positions is reasonable. If it is unreasonable, it is necessary to reset parameters for calculation, and individual files can be directly modified in place.
3、 Generation of tool path for slotting machining
The tool path of slot expanding machining can be synthesized by using the tool path of precision milling blade profile.
4、 Generation of tool path for slotting
The tool path for slotting is generated by one of the tool paths for slotting. The tool path for slotting is the tool path for the last tool of slotting by using the tool semi precision flat bottom taper shank bar milling cutter and the selected center slotting tool path. The tool center of this tool path retracts along the tool axis vector direction. The length of each retraction can be determined according to the processing material and tool size, and the tool path is cut to calculate each slotting tool path.