| Summary: | 碩士 === 中華大學 === 機械與航太工程研究所 === 87 === It is known from previous study that blades of an air compressor were machined directly from aluminum alloy disk body using 3-axis CNC machining center with a manual operated A-axis rotary table.The result reveals that the rotaried has to be rotaried several times in order to cut one half-blade surface. Besides, it involves techniques for surface dividing and mesh pattern recognition about whether or not the patch surface can be accessed by the cutting tool, especially for the highly twisted rotor blades of an air compressor.
In order to overcome difficulties encountered in 4-axis machining, a self-designed manually operated rotary table has been installed as B-axis that aluminum alloy disk body is fixed on. Therefore, initial workpiece angular position setup can be accomplished by A and B axes manual operations. The experimental results indicated that either roughing waste material between rotor blades or finishing one half-blade surfaces, it is completely accessed by the cutting tool without any further changing angular positions of the workpiece.
The main study subjects include as follows:
1.Design、fabricate and install the B-axis rotary table structure on A-axis end plate.
2.CADDS5 CAD/CAM software package was employed for establishing blade model and generating tool paths.
3.Cutting the rotor blades using CNC machining with 2-axes manual operations.
4.Precision measurements of the finished rotor blades by coordinate machine and roughness tester.
5.Inspect the cutting tool edge damage after finishing the blade cutting by tool microscope and hot copy printer.
Possibility of 4-axis machining is also studied. Characteristics of 4-axis machining reveals that tool axis is always normal to the blade surface , that makes it impossible to cut blades directly on the disk body without interference occurred between cutter and neighbor blades. Therefore, 5-axis cutting command, SURFCUT5 and self-editing 4-axis postprocessor were employed. Because only A-axis is available, B-axis angle variation of the tool path should be kept within a minimum acceptable range. Parameters that affect B-axis angle variation have been studied,which include number of times and angular positions of two manual operated axes , size of the part surface and fixed slew angle used.
Although 5-axis machining is preferred for rotor blade cutting , but it is much more expensive and only a few are installed in the local industry .Therefore , installation of manual operated B-axis actually expands the functions of 4-axis machining and is useful for machining the specified workpiece ,such as rotor blades.
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