JP4755846B2 - Grinding method and grinding machine - Google Patents

Description

  The present invention relates to a workpiece grinding method using a grindstone and a grinding machine, and more particularly to a grinding method that suppresses chatter vibration and a grinding machine that can suppress chatter vibration.

  When grinding a workpiece in a grinding machine, when the grinding amount reaches a certain value, waviness is formed on the outer surface of the grinding wheel and vibration occurs between the workpiece and the grinding wheel, and the grinding wheel shaft generates significant vibration in the normal direction. There are things to do. When the vibration occurs, a chatter mark may occur on the grindstone surface of the workpiece.

  Generally, a grinding machine is configured so that stable driving can be performed by performing appropriate control and rotational driving. However, if grinding is started under certain processing conditions and the processing is continued, periodic clogging and waviness may occur on the outer peripheral surface of the grindstone. Here, n = f / (N / 60), where n is the number of undulations on the outer peripheral surface of the grindstone, Nrpm is the grindstone rotation speed, and fc / s is the chatter frequency. The chatter frequency f is substantially equal to the natural frequency of the grindstone / work system. Therefore, when the period of vibration due to external force is equal to the period of the natural frequency, resonance causes a larger vibration and a chatter mark is likely to occur.

Therefore, in order to suppress chatter vibration, the rotational speed of the motor is appropriately changed by inverter control, and in order to suppress chatter vibration caused by electromagnetic vibration of the motor, the power of the motor is turned off and the grinding wheel is driven by inertia. It has also been proposed to perform grinding by rotating the wheel. Furthermore, when chatter vibration is detected by a vibration sensor, it has also been proposed to suppress chatter vibration by changing grinding conditions (see Patent Document 1).
JP-A-9-11084

  As described above, in the configuration in which the rotational speed of the motor is changed by inverter control, chatter vibration due to resonance can be suppressed to some extent, but the fluctuation of the rotational speed of the motor is a gentle change, and chatter vibration is reduced. Improvement is desired to prevent it more effectively.

  In a configuration in which grinding is performed by rotating the grindstone with inertia while the power of the motor is turned off, chatter vibration caused by electromagnetic vibration of the motor can be suppressed, but chatter vibration caused by electromagnetic vibration of the motor turns on the motor. The workpiece cannot be ground continuously, and there is a problem in improving efficiency.

  Further, in the configuration described in Patent Document 1, it is not concrete how to change the grinding condition after detecting chatter vibration by a vibration sensor, and further improvement is desired.

The present invention has been made in view of the conventional problems as described above, and is a method for grinding a workpiece by a grinding machine, in order to disturb a resonance phenomenon that causes chatter vibration in a control motor for rotating a grinding wheel. Applying rectangular pulses with different amplitudes, periods, and duty ratios at any given time to impart vibration in the rotational direction to the rotation of the grinding wheel, preventing chatter vibration due to resonance, and grinding the workpiece It is characterized by doing.

Also, there is provided a method for grinding a workpiece by a grinding machine, wherein control is performed to rotate the grinding wheel when chatter vibration is detected during grinding of the workpiece by rotating the grinding wheel at a predetermined rotational speed. In order to disturb the resonance phenomenon that causes chatter vibrations to the motor, a rectangular pulse with different amplitude, period, and duty ratio is applied to the motor at random intervals to give vibration in the direction of rotation of the grinding wheel. Grinding is performed while preventing chatter vibration due to the above.

A grinding machine having a control motor for rotating a grinding wheel for grinding a workpiece set on a work table, the rotational speed control means for controlling the rotational speed of the control motor, and the rotation A motor driver that rotationally drives the control motor under the control of the speed control means, and a resonance phenomenon that causes chatter vibration to the motor driver in order to suppress chatter vibration during grinding of the workpiece by the grinding wheel. In order to disturb, a pulse generation means for applying a rectangular pulse having different amplitude, period, and duty ratio to each other at an arbitrary time is provided.

  According to the present invention, the number of rotations of the control motor for rotating the grindstone can be changed at random, and the occurrence of resonance can always be prevented. Accordingly, the workpiece can be ground while preventing chatter vibration.

  Referring to FIG. 1, as conceptually and schematically, a grinding machine 1 according to an embodiment of the present invention includes a machine base 3, and a grinding wheel base 5 is placed on the machine base 3 on the X axis. It is mounted so that it can reciprocate in the direction. A control motor 7 such as a servo motor is mounted on the grinding wheel base 5, and a grinding wheel 9 is mounted on the output shaft of the control motor 7. Further, the control motor 7 is provided with a vibration sensor 11 for detecting chatter vibration of the grinding wheel 9. This vibration sensor 11 is the same as the vibration sensor described in Patent Document 1 and is composed of an acceleration sensor, and since it is well known, detailed description thereof is omitted.

  A work table 13 that supports a work W to be ground by the grinding wheel 9 is provided at a position close to the machine base 3 so as to be movable in the Z-axis direction. On the work table 13, a work head 15 for supporting one end of the work W and rotating the work W is provided, and a tailstock for rotatably supporting the other end of the work W is provided. 17 is provided.

  The grinding machine 1 is provided with an X-axis servo motor 19 for moving the grindstone table 5 in the X-axis direction, and a Z-axis servo motor for moving the work table 13 in the Z-axis direction. 21 is provided. Further, the grinding machine 1 is provided with a control device 23 such as a CNC device for controlling the entire operation of the grinding machine 1.

  In the configuration as described above, when the grinding machine 1 is driven under the control of the control device 23 and the workpiece W is ground by the grinding wheel 9, chatter vibration is generated and chatter marks are formed on the finished surface of the workpiece W. May occur. Therefore, in the present embodiment, the following configuration is adopted to prevent the chatter vibration.

  That is, as shown in FIG. 2, the control device 23 has grinding conditions input from the input means 25, for example, the material and diameter of the workpiece W, the material, diameter and type of the grinding wheel 9, and the cutting depth for the workpiece W. A rotation speed calculating means 27 for calculating an appropriate rotation speed of the grinding wheel 9 according to various conditions such as a grinding speed is provided. As a configuration for obtaining the appropriate rotational speed of the grinding wheel 9, a data table 29 in which rotational speeds of various grinding wheels 9 are set in advance corresponding to the material of the workpiece W and the like is created, and the grinding wheel 9 The proper rotation speed is obtained.

  An arithmetic expression such as an empirical expression for calculating an appropriate rotation speed of the grinding wheel 9 is stored in the memory 31 in advance, and data necessary for this arithmetic expression is input from the input means 25 to rotate the grinding wheel 9. It is also possible to adopt a configuration for obtaining the speed.

  Further, the control device 23 is provided with a rotation speed control means 33 for controlling the rotation speed of the control motor 7 based on the calculation result of the rotation speed calculation means 27. Under the control of the rotational speed control means 33, the rotational speed of the control motor 7 is controlled via the motor driver 35.

  Further, the control device 23 is provided with pulse generation means 37 for generating a pulse having a steep rise and fall, for example, like a rectangular pulse, and the conditions of the pulses generated by the pulse generation means 37 are set. Pulse condition adjusting means 39 for adjusting is provided. This pulse condition adjusting means 39 includes an amplitude adjusting means 41 for adjusting the amplitude of the pulse waveform generated from the pulse generating means 37, a period adjusting means 43 for adjusting the period, and a duty ratio adjusting means 45 for adjusting the duty ratio. Yes.

  The amplitude adjusting unit 41 stores a plurality of types of amplitudes in advance, and the cycle adjusting unit 43 stores a plurality of types of cycles. Further, the duty ratio adjusting means 45 stores a plurality of types of duty ratios in advance. Then, the combination of the amplitude selected from the amplitude adjusting means 41, the cycle selected from the period adjusting means 43, and the duty ratio selected from the duty ratio adjusting means 45 is switched every predetermined time or every arbitrary time. Switching means 47 is provided.

  Further, the control device 23 is provided with chatter vibration detecting means 49. The chatter vibration detection means 49 is provided in each of the charge-voltage converter, amplification amplifier, frequency analysis calculator, secondary converter, frequency setter, threshold setter and chatter determiner described in Patent Document 1. The apparatus has a corresponding configuration, and has a function of determining chatter vibration by vibration by the vibration sensor 11. That is, the chatter vibration detecting means 49 can adopt the same configuration as that described in Patent Document 1 and is well known, and therefore detailed description of the chatter vibration detecting means 49 is omitted.

  In the above configuration, when the control motor 7 is driven at a rotation speed appropriate for the grinding of the workpiece W and the workpiece W is ground by the grinding wheel 9 under the control of the control device 23, chatter vibration may occur due to resonance. is there. Vibration during grinding of the workpiece W is always detected by the vibration sensor 11, and chatter vibration is detected by the chatter vibration detecting means 49 when the magnitude of the vibration exceeds a preset threshold value.

  As described above, when chatter vibration is detected by the chatter vibration detecting means 49, a pulse is applied from the pulse generating means 37 to the motor driver 35. Therefore, the rotation speed of the control motor 7 rotating at a predetermined rotation speed is rapidly accelerated or decelerated by the applied pulse. Therefore, the resonance phenomenon causing the chatter vibration is disturbed, and the chatter vibration is suppressed.

  By the way, in the above description, when chatter vibration is detected by the chatter vibration detecting means 49, the case where a pulse is applied to the motor driver 35 from the pulse generating means 37 is described. However, the control motor 7 is driven to rotate. It is also possible to apply a pulse from the pulse generation means 37 to the motor driver 35 from the beginning of starting the grinding of the workpiece W.

  In this case, it is desirable not to always apply a constant pulse, but to apply a pulse in which, for example, the amplitude, period, and duty ratio are appropriately changed in accordance with the shape, size, and the like of the workpiece W and the grinding wheel 9. By doing so, chatter vibration due to resonance can be effectively prevented. In this case, the amplitude arbitrarily selected from the plurality of amplitudes stored in the amplitude adjusting means 41, the period arbitrarily selected from the plurality of periods stored in the period adjusting means 43, and the duty ratio adjusting means 45 are stored. After a pulse generated by combining arbitrarily selected duty ratios from a plurality of duty ratios applied for a certain period of time output from the pulse generating means 37, the switching means 47 applies the amplitude, period, duty The combination of the ratios can be changed, and the changed pulses can be output again from the pulse generating means 37 and applied to the motor driver.

  As described above, pulses having different amplitudes, periods, and duty ratios are applied to the motor driver 35 to the control motor 7 that is rotationally driven via the motor driver 35 under the control of the rotational speed control means 33. Therefore, the occurrence of resonance is inhibited, and chatter vibration due to resonance is effectively prevented. It is desirable to change the three types of amplitude, period, and duty ratio each time. However, it is not always necessary to change the three types. In short, it is only necessary to prevent chatter vibration due to resonance. Therefore, by changing only one of the three types, resonance may be inhibited.

  As can be understood from the above description, since the resonance is prevented by changing the rotation speed of the control motor 7 that rotates the grinding wheel 9, chatter vibration due to resonance can be prevented, and chatter marks are generated. High precision grinding can be performed.

It is a conceptual and schematic explanatory drawing of the grinding machine which concerns on embodiment of this invention. It is a functional block diagram which shows the structure of the control apparatus in the said grinding machine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Grinding machine 7 Control motor 9 Grinding wheel 11 Vibration sensor 13 Work table 23 Control device 27 Rotation speed calculation means 29 Data table 33 Rotation speed control means 35 Motor driver 37 Pulse generation means 39 Pulse condition adjustment means 41 Amplitude adjustment means 43 Period adjustment Means 45 Duty ratio adjusting means 47 Switching means 49 Chatter vibration detecting means

Claims (3)

A grinding method for workpieces by a grinding machine, in order to disturb a resonance phenomenon that causes chatter vibrations in a control motor for rotating a grinding wheel, rectangular pulses having different amplitudes, periods, and duty ratios are given at arbitrary times. A grinding method characterized by applying a disturbance in a rotating manner to impart a rotational vibration to the rotation of the grinding wheel to prevent chatter vibration due to resonance and grinding a workpiece. A method for grinding a workpiece by a grinding machine, wherein when a chatter vibration is detected during grinding of a workpiece by rotating the grinding wheel at a predetermined rotational speed, a control motor for rotating the grinding wheel is provided. In order to disturb the resonance phenomenon causing chatter vibration, rectangular pulses having different amplitudes, periods, and duty ratios are applied disturbanceally every arbitrary time to impart vibration in the direction of rotation of the grinding wheel, thereby causing chatter due to resonance. A grinding method characterized by performing grinding while preventing vibration. A grinding machine having a control motor for rotating a grinding wheel for grinding a workpiece set on a work table, the rotational speed control means for controlling the rotational speed of the control motor, and the rotational speed control In order to suppress chatter vibration during grinding of the workpiece by the grinding wheel and the motor driver that rotates the control motor under the control of the means, to disturb the resonance phenomenon that causes chatter vibration to the motor driver And a pulse generating means for disturbanceally applying rectangular pulses having different amplitudes, periods, and duty ratios every arbitrary time .

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