Tool compensating device for the computerized numerically control machine tool
The present invention relates to a computerized numerically control machine tool, more particularly to an apparatus for sensing a position of a cutting tool so as to compensate a positional deviation from the standard position of the cutting tool in a computer numerical controlled machine tool.
An apparatus for sensing a position of a cutting tool in a computerized numerical control machine tool is provided including an arm supporting and moving a sensor that cooperates with the cutting tool. Also provided is a housing including a gear assembly and a driving motor for moving the arm, and a stopper for defining an operating position of the arm. The driving motor supplies rotation force to the gear assembly so as to pivot the arm against the stopper and then apply force to an elastic member. When the driving motor is stopped, the elastic member applies a force, through the gear assembly, urging the arm against the stopper in the operating position.
Generally, the computerized numerical control machine tool automatically processes a work piece by using a computer after confirming the position of a cutting tool on a basis of a pre-programmed process condition such as a target processing measurement, a desired shape, a transferring speed of the cutting tool, etc.
The work piece, which is supported and rotated between the headstock and the tailstock, is automatically processed by the cutting tool mounted to the tool rest sliding on the bed 12a on a basis of the pre-programmed process condition.
However, problems with the conventional computerized numerical control machine tool as described above are that a cutting edge of the cutting tool for processing the work piece may be worn due to the friction between the cutting edge and the work piece and the processing precision of the cutting tool may deteriorate due to the change of the cutting tool’s position.
A variety of endeavors for solving these problems have been proposed. One approach, a program for compensating the cutting tool’s position so as to compensate a positional deviation between the coordinates of the cutting tool for processing the work piece and the standard coordinates in order to enhance the processing capability of the cutting tool during operation of processing the work piece, has been proposed. This program is preliminarily input to the computerized numerical control lathe.
However, one problem with the apparatus for sensing a position of the cutting tool as, described above is that the arm having the sensor must be maintained at a sensing position until the sensor senses the position of the cutting tool. Therefore, the driving motor must be continuously operated and thereby it may be damaged due to the overload applied thereto.
Therefore, the present invention has been developed to solve the abovementioned problems. It is an object of the present invention to provide an apparatus for sensing a position of a cutting tool which is capable of preventing the overload from being applied the driving motor by stopping the driving motor from operating while a sensor sense the position of the cutting tool in a computerized numerical control machine tool.
In order to accomplish the above object, the present invention provides a tool compensating apparatus for the computerized numerical control machine tool, the apparatus comprising: [0016] a first sensor for sensing a position of a cutting tool in the computerized numerical control machine tool; [0017] an arm for moving the first sensor to a predetermined position for sensing the position of the cutting tool; [0018] a gear assembly for pivoting the aim in a range of predetermined angles, the gear assembly being combined to the aim; [0019] a driving motor for supplying the gear assembly with a driving force; and [0020] a housing for enclosing the gear assembly, a stopper and the driving motor.
At this time, if the arm excessively pivots in accordance with the rotation of the worm wheel, the second sensor judges whether the cam adjacent to the worm wheel passes by the second sensor or not. When the cam passes by the second sensor, the second sensor supplies a signal for stopping the operation of the driving motor to the control part of the computerized numerical control machine tool.
Meanwhile, when the arm excessively pivots, the worm wheel tends to continuously rotate due to its inertial force. Accordingly, the worm engaged with the worm wheel moves toward the other end of the worm shaft along the worm shaft and it may alleviate the rotation of the worm wheel. Since the worm moves back to its initial position by means of the elastic member for elastically supporting the worm, the worm wheel may rotate in the reverse direction and thereby the cam moves a position to be sensed by the second sensor.
The control part of the computerized numerical control machine tool compares the detected value input from the apparatus 20 for sensing a position of the cutting tool with a standard value, and then calculates a displacement of the cutting tool and it sends a control signal for compensating the position of the cutting tool to the computerized numerical control machine tool in accordance with the result.
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