Grinding method of a workpiece and grinding apparatus
An adaptive work table-reciprocation control system and method that can reduce a grinding time. The system uses a vibration sensor head installed on a chuck surface in the vicinity of the workpiece to detect a vibration signal emitted from the contact zone between the grinding wheel and the workpiece. When the value of the vibration signals falls below a trigger level, a work table direction of motion is reversed.
1. A method of grinding a workpiece surface of a workpiece using a rotable grinding wheel, where the workpiece is provided on a chuck on a work table and moved reciprocally in the horizontal direction, said method comprising:
detecting vibration signals emitted from a contact zone between the grinding wheel and the workpiece;
moving the work table in a moving direction when a value (E i ) of the vibration signal is higher than a previously set trigger value (E 0 ) of the vibration signal; and
transmitting a reverse signal to a drive unit of the work table to reverse a moving direction of the work table when the value (E i ) of the vibration signal reduces to a value equal to or below the previously set trigger value (E 0 ).
2. The method of claim 1 , further comprising moving the workpiece reciprocally relative to the grinding wheel.
3. The method of claim 1 , further comprising filtering the vibration signals with a low-pass filter.
4. The method of claim 3 , wherein the filtering prevents the transmitting of a reverse signal when the grinding wheel is above a gap in the workpiece.
5. The method of claim 4 , wherein the filtering blocks vibrations above a cutoff frequency from being detected and the cutoff frequency is between 5 and 500 Hz.
6. The method of claim 4 , wherein the width of the gap in the workpiece, measured in a direction of travel of the grinding wheel, is 0.01 to 10 mm.
7. The method of claim 1 , further comprising extracting a basic frequency from the vibration signal.
8. The method of claim 7 , wherein the basic frequency is between 1 and 100 Hz.
9. The method of claim 1 , wherein vibration signals are detected with a vibration sensor head installed on a surface of the chuck.
10. A grinding apparatus comprising:
a work table;
a chuck provided on the work table and configured to receive a workpiece;
a drive unit configured to reciprocate the work table in a first direction;
a grinding wheel spindle configured to move a grinding wheel in a second direction substantially perpendicular to a surface of the work table;
a vibration sensor head configured to detect a vibration signal generated from an interference area of the grinding wheel and the workpiece;
a comparison part configured to compare the value (E i ) of the vibration signal with the trigger value (E 0 ) of the vibration signal; and
an output part configured to output a signal to advance the work table in a first direction when the value (E i ) of the vibration signal at the basic frequency is higher than the trigger value (E 0 ) of the vibration signal at the basic frequency, and to output a reverse signal to the drive unit of the work table in a second direction when the value (E i ) of the vibration signal at the basic frequency reaches the trigger value (E 0 ) or less of the vibration signal at the basic frequency.
11. The grinding apparatus of claim 10 , further comprising a low-pass filter configured to receive the amplified vibration signal and to allow a specified frequency band to pass there-through.
12. The grinding apparatus of claim 11 , wherein the low-pass filter has a cut-off frequency between 5 and 500 Hz.
13. The grinding apparatus of claim 10 , further comprising a protective cover near the vibration sensor head.
14. The grinding apparatus of claim 10 , further comprising an amplifier configured to amplify the vibration signal detected by the vibration sensor head.
15. The grinding apparatus of claim 10 , further comprising a recording part configured to extract a basic frequency from the vibration signal having passed through the low-pass filter and to receive a value (E i ) of the vibration signal at the basic frequency.
16. The grinding apparatus of claim 10 , further comprising a storage part configured to store a trigger value (E 0 ) of the vibration signal at the basic frequency.
17. A grinding apparatus comprising:
a work table;
a chuck provided on the work table and configured to receive a workpiece;
a drive unit configured to reciprocate the work table in a first direction;
a grinding wheel spindle configured to move a grinding wheel in a second direction substantially perpendicular to a surface of the work table;
means for detecting vibration signals emitted from a contact zone between the grinding wheel and the workpiece;
means for determining, based on the vibration signals, whether the grinding wheel is grinding the workpiece.
18. The apparatus of claim 13 , wherein the means for determining includes a means for comparing the vibration signals to a preset vibration frequency.