1. Field of the Invention
The present invention relates to improvements in a method of controlling an elliptical vibrator. The elliptical vibrator is used for processing a workpiece such as steel product by causing elliptical vibrations to a tool, for example.
2. Description of the Background Art
An elliptical vibratory processing apparatus has been used for processing a workpiece into a required shape. The elliptical vibratory processing apparatus for example has an elliptical vibrator which is formed of a body in the shape of an octagonal prism and step horns provided respectively on both ends of the body. One of the step horns has its end provided with a tool and this tool elliptically vibrates to process the workpiece.
Specifically, driving piezoelectric elements of a required number are provided to the elliptical vibrator. A predetermined sinusoidal voltage having a predetermined phase difference (e.g. 90xc2x0) is applied individually to the driving piezoelectric elements. Accordingly, flexure vibrations are caused to the elliptical vibrator in each of the horizontal direction (X direction) and the vertical direction (Y direction). The flexure vibrations in the two directions of the elliptical vibrator are mechanically synthesized. Then, an end (cutting edge) of the tool, which is provided to the elliptical vibrator, is allowed to draw a trajectory of elliptical vibrations (see FIG. 3).
For the cutting operation shown in FIG. 3 for example, the cutting tool 2 is caused to elliptically vibrate with respect to the workpiece 1 to be cut and move in a cutting direction indicated by xe2x80x9cAxe2x80x9d relatively with respect to workpiece 1, so that cutting tool 2 can elliptically vibrate to cut workpiece 1.
Suppose that the distance by which cutting tool 2 moves in cutting direction A is constant. Then, a higher steadiness with which the edge of cutting tool 2 draws an elliptical trajectory 16 in a required shape (preset target shape) enables workpiece 1 to be processed with higher precision through the elliptical vibrations.
Here, the flexure vibrations in the two directions as described above interfere with each other to cause tool interference.
For example, the horizontal flexure vibrations of the elliptical vibrator interfere with (impede) the vertical flexure vibrations. Then, it is impossible to control the vertical flexure vibrations for allowing the vertical flexure vibrations to have a required amplitude.
As the horizontal flexure vibrations, the vertical flexure vibrations of the elliptical vibrator also interfere with the horizontal flexure vibrations, which makes it impossible to control the horizontal flexure vibrations so as to allow the horizontal flexure vibrations to have a required amplitude.
In other words, it is impossible to steadily control and shape the trajectory, as required, of the elliptical vibrations drawn by the edge of a tool such as the cutting tool.
Consequently, there arises a disadvantage, due to the fact that the elliptical vibration trajectory drawn by the tool edge cannot be shaped as required, that the workpiece cannot be processed with high precision through elliptical vibrations.
One object of the present invention is to provide a method of controlling an elliptical vibrator for processing a workpiece through elliptical vibrations of a tool. An elliptical vibration trajectory drawn by an edge of the tool can be controlled with steadiness so as to shape the trajectory as required, and thus the workpiece can be processed with high precision through the elliptical vibrations.
A method of controlling an elliptical vibrator according to the present invention is used for processing a workpiece by means of a tool through elliptical vibrations thereof, vibrations in two directions being synthesized by an elliptical vibratory processing apparatus for causing elliptical vibrations and transmitting the elliptical vibrations to the tool. An amount of interference by vibrations in one of the two directions with vibrations in the other direction is correctively eliminated from the vibrations in that other direction.
According to the method of controlling an elliptical vibrator of the present invention, the vibrations in the two directions are vibrations in any of flexure vibration mode, longitudinal vibration mode, torsional vibration mode, shear vibration mode, and radial vibration mode.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.