KR20190009682A - An method for controlling grinding apparatus - Google Patents

Abstract

Disclosed is a grinding apparatus control method including a step of vacuum-adsorbing and fixing a workpiece placed on a chuck table provided in a processing space of the apparatus main body, a step of acquiring and storing a set value of a processing condition of the workpiece fixed to the chuck table, a first measurement step of measuring the initial thickness and the flatness of the workpiece fixed to the chuck table, a step of grinding the workpiece by driving a grinding wheel to rotate, a second measurement step of measuring the thickness and the flatness of the workpiece during the grinding, a step of continuing a step of performing processing in order to satisfy the thickness and the flatness set in accordance with the measurement result in the first measurement step and finishing the processing when the result measured in the second measurement step satisfies the set thickness and flatness, a step of supplying and recovering cooling water during the processing, and a step of dressing a grinding tooth of the grinding wheel.

Description

AN METHOD FOR CONTROLLING GRINDING APPARATUS [0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grinding apparatus, and more particularly, to a control method of a grinding apparatus capable of performing automatic grinding processing of various semiconductor modules and wafers.

Generally, silicon wafers used for producing electronic components such as semiconductor devices are manufactured by a slicing process for thinly cutting a single crystal silicon ingot, a lapping process for maintaining the thickness and flatness of the cut wafer, Etching process for removal of impurities or defects, polishing process for improving the surface damage or flatness, and subsequent cleaning process, for example, a lapping process, a process for removing impurities or defects .

In addition, grinding is performed to control the thickness and flatness of the silicon wafer by grinding the surface of the sliced silicon wafer in the process of manufacturing the silicon wafer in the lapping process or before the polishing process.

Such a grinding process is a process added to satisfy the required high flatness as semiconductor devices are highly integrated.

On the other hand, the grinding apparatus used in the grinding process is composed of a spindle, a grinding wheel attached to the bottom of the spindle and rotated, and a chuck table on which a workpiece such as a wafer is attracted.

When the wafer is loaded on the chuck table, the chuck table adsorbs the wafer transferred by vacuum pressure and rotates the adsorbed wafer at a constant speed. Then, the spindle located at the upper portion of the chuck table rotates and descends to be brought into contact with the wafer, thereby polishing the wafer.

The grinding wheel is comprised of a grinding tooth disposed at the lower edge of the rotating grinding body. The grinding teeth are formed of diamond material and are installed at regular intervals, and the wafer is polished while rotating.

However, since it is difficult to confirm the polishing thickness of the wafer during the grinding process as described above, the wafer on the chuck table is moved again, measured by a separate thickness measuring device, and then repeatedly polished until a desired thickness is reached. It took a long time and productivity was low.

In addition, after the grinding wheel is used for a certain period of time, the surface of the grinding tooth becomes a certain thickness and must be managed through polishing or the like so as to maintain the planarization state. In this case, There was an inconvenience such as the need to reattach it.

Korean Patent No. 10-1459607

SUMMARY OF THE INVENTION It is an object of the present invention to provide a grinding apparatus control method capable of automatically controlling the operation of grinding wheels as well as processing and measuring a workpiece.

According to another aspect of the present invention, there is provided a method of controlling a grinding apparatus including vacuum chucking a workpiece placed on a chuck table installed in a processing space of a main body of the apparatus, Acquiring and storing a value for setting a processing condition of a workpiece fixed to the chuck table; A first measuring step of measuring an initial thickness and a flatness of a workpiece fixed to the chuck table; Rotating the grinding wheel to grind the workpiece; A second measuring step of measuring a thickness and a flatness of the workpiece during the grinding process; Continuing the machining step so as to satisfy the set thickness and flatness according to the measurement result in the first measuring step, and when the measured result in the second measuring step satisfies the set thickness and flatness, ≪ / RTI > Supplying and recovering cooling water during the processing step; And dressing a grinding wheel of the grinding wheel.

Thus, it is possible to precisely process the workpiece to a desired thickness while automatically measuring the thickness of the workpiece.

It is preferable to further include an air jetting step of jetting air to the measurement position of the workpiece in the first and second measuring steps.

Thereby, the thickness can be measured while removing the foreign substance on the workpiece, and the precision can be increased.

The method may further include outputting an alarm signal when the thickness of the workpiece measured in the first measuring step is less than a predetermined thickness.

This saves unnecessary costs and time due to polishing of unfinished unfinished workpieces.

The cooling water supply and recovery step may include the steps of injecting cooling water to the polishing position during the processing step; Recovering the injected cooling water; Centrifuging the recovered cooling water to separate the sludge and the cooling water; And resupplying the separated cooling water to the cooling water storage tank.

Thus, the cooling water can be used to cool the frictional force during the polishing process, and the used cooling water can be recovered and reused to reduce the cost.

The dressing step may be performed before the grinding step, during the machining step, and after the machining step, according to a preset order, and returning the grinding wheel to an initial position; Raising the dressing tool located at the lower portion of the grinding wheel returned to the initial position using an actuator; And rotating the grinding wheel to grind the dressing tool to the dressing tool for dressing the dressing tool.

As a result, the polishing process and the dressing process are automatically performed in the machining space, thereby reducing the machining time.

Further, it is preferable that the step of dressing during the grinding process is set so as to measure a load of the grinding wheel and to be performed when the measured load exceeds a set load.

Thus, the grinding tool is controlled to maintain a state suitable for the machining conditions, thereby enhancing the machining reliability and effectively performing the machining process.

Calculating a wear thickness of the grinding target based on the measured thickness of the workpiece measured by the first and second measuring apparatuses; And an initial value of the grinding wheel during the machining process of the workpiece on the basis of the wear thickness calculated in the step of calculating the wear thickness of the grinding tool.

Thus, the state and thickness of the grinding tooth according to the number of machining times are confirmed, reflected by the grinding machining time, and the machining process can be performed more accurately and the time can be shortened.

The dressing step may further include comparing the abrasion thickness of the grinding tooth calculated in the grinding toe wear thickness calculating step with the replacement reference thickness to determine the replacement time of the grinding tooth and outputting the replacement signal .

Thus, the working time of the grinding tooth can be accurately informed to the worker.

According to the grinding apparatus control method of the present invention, the workpiece such as a wafer is attracted and polished, and the machining process can be automatically performed so as to satisfy the desired thickness and flatness while automatically measuring the polishing thickness.

Therefore, the wafer processing time can be reduced and the machining precision can be further improved.

Further, since grinding teeth of the grinding wheel can be automatically dressed when necessary, the grinding process can be easily performed and the grinding process can be performed while the grinding wheel is maintained in the best condition. Therefore, It is possible to improve the reliability of the apparatus.

1 is a perspective view showing a grinding apparatus to which a grinding apparatus control method according to an embodiment of the present invention is applied.
FIG. 2 is a schematic block diagram of the grinding apparatus shown in FIG. 1. FIG.
Fig. 3 and Fig. 4 are diagrams excerpted from the main part of Fig. 1, respectively, for explaining the state at the time of the yearly turning.
5 is a schematic view for explaining the dressing process.
6 is a flowchart illustrating a grinding apparatus control method according to an embodiment of the present invention.

Hereinafter, a method of controlling a grinding apparatus according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

First, the grinding apparatus 100 will be described with reference to FIGS. 1 to 4. FIG.

The grinding apparatus 100 includes a main body 110, a chuck table 120 installed on the main body 110, a grinding wheel 130 installed on the chuck table 120, a chuck table 120, A dressing module 150 installed on the apparatus main body 110 and dressing the grinding tooth 131 of the grinding wheel 130, and a dressing module 150 for dressing the grinding wheel 131 of the grinding wheel 130. The thickness measuring module 140 measures the thickness and the flatness of the workpiece, A cooling water supply unit 170, an output unit 180, an input and setting unit 190, a control unit 200, and a storage unit 210.

In the apparatus main body 110, a processing space 111 for processing a workpiece is formed at a predetermined depth from the front surface. The front surface of the processing space 111 can be opened and closed with a transparent window. The output unit 180 and the input and setting unit 190 may be externally exposed to the apparatus main body 110. The input and setting unit 190 may include an operation panel, a plurality of operation indicators, an operation button, and a touch pad 191 on the front surface of the apparatus main body 110. Of course, the output unit 180 may include at least one of a speaker, an alarm lamp, and a display installed in the apparatus main body 110.

A chuck table (120) is rotatably installed on the inner bottom of the processing space (111). A workpiece 10 such as a wafer to be machined is moved and seated on the chuck table 120 and the seated workpiece 10 is fixed on the chuck table 120 by the suction pressure.

The grinding wheel 130 is spaced apart from the upper portion of the chuck table 120 and disposed at a position where the rotation center of the chuck table 120 and the rotation center of the grinding wheel 130 are spaced from each other. A grinding wheel 131 is disposed at a lower edge of the grinding wheel 130 at regular intervals in a circular arc direction. The grinding tooth 131 grinds the surface of the workpiece placed on the chuck table 120 rotating in the opposite direction when the grinding wheel 130 rotates while descending.

Here, the grinding wheel 130 can be moved vertically and horizontally by a wheel drive unit (not shown), and can be rotationally driven based on the center of the grinding wheel 130 to be driven in three axes.

The dressing module 150 can be dressed automatically in the machining space 111 to be maintained in a state optimized for abrasive machining, And a detailed description will be given later.

The thickness measurement module 140 is installed in the upper part of the processing space 111 of the apparatus main body 110 so as to be movable up and down. The cutting chamber 112 is also provided in the upper part of the machining space and is intercepted from the outside when the thickness measuring module 140 is inserted into the cutoff chamber 112 at the time of polishing. When the thickness of the workpiece is to be measured during the machining process, the shutter (not shown) of the cutoff chamber 112 is opened and the thickness measurement module 140 is lowered to measure the thickness of the workpiece 10 placed on the chuck table 120 . The thickness measuring module 140 includes a contact probe 141, a holder 143 for supporting the contact probe 141, and a lifting and driving part 143 for vertically moving the holder 143 in the working space 111 And a thickness calculating unit 147 for calculating the thickness of the workpiece 10 based on the contact information of the contact probe 141 and the contact probe 141.

The contact probe 141 includes a first contact probe 141a and a second contact probe 141b which are disposed at a lower portion of the holder 143 so as to be spaced apart from each other. The first and second contact probes 141a and 141b can detect the thickness and the flatness of the workpiece 10 accurately by sensing the positions of the first and second contact probes 141a and 141b in contact with each other. For example, the first contact probe 141a and the second contact probe 141b can be made to touch and sense different positions of the workpiece 10, so that accurate Thickness and flatness can be measured.

The holder 143 is supported by an elevation driving unit 145 mounted on the apparatus main body 110 and is moved up and down to be moved into and out of the shutoff chamber 112.

The thickness calculating unit 147 calculates the thickness and the flatness of the workpiece 10 based on the sensing information from the first and second contact probes 141a and 141b and outputs the calculation information to the controller 200. [ . That is, the thickness calculating section 147 accurately calculates the thickness and the flatness of the workpiece 10 based on the contact point of the first contact probe 141a as a reference point and the contact point of the second contact probe 141b can do. Of course, when the initial position value is set before the first and second contact probes 141a and 141b are lowered, the first and second contact probes 141a and 141b detect a plurality of points of the workpiece 10 The thickness and flatness of the workpiece 10 at two points can be calculated.

It is possible to precisely measure both the working thickness and the flatness of the workpiece 10 by measuring the thickness when the pair of contact probes 141a and 141b are brought into contact with the surface of the workpiece 10 while descending.

As described above, the control unit of the apparatus main body can automatically perform precision machining so as to obtain the desired thickness and flatness while precisely adjusting the machining time and the descent height of the grinding wheel in the control unit based on the measured value measured by the thickness measuring module.

The dressing module 150 is installed inside the machining space 111 and spaced apart from the lower part of the grinding wheel 130 so as to face each other. The dressing module 150 is installed vertically movably in the apparatus main body 110 and is capable of being dressed by being brought into contact with the grinding tooth 131 when the dressing module 150 is lifted for dressing (see FIG. 5).

The dressing module 150 includes a module main body 151, a dressing tool 153 coupled to an upper end of the module main body 151, and an actuator 155 supporting the module main body 151 and moving the module main body 151 up and down.

According to this configuration, the grinding tool 130 is used to dress the grinding tooth 131 automatically before or after the grinding operation or after the grinding process using the dressing module 150 Management.

The air spraying unit 160 is used for securing the measurement accuracy by removing foreign matter or the like at the measurement position when measuring the thickness of the workpiece 10 by using the thickness measurement module 140. The air injection unit 160 includes first and second air injection nozzles 161 and 162 installed to spray air toward the contact ends of the first and second contact probes 141a and 141b and air injection nozzles 161 and 162 And an air pump 163 for supplying compressed air. The first and second air injection nozzles 161 and 162 are installed in the holder 143. Thus, when the thickness measuring module 140 descends and contacts the workpiece 10 to measure the thickness, the foreign matter at the contact position of the workpiece 10 or the like is removed by the injection pressure of the compressed air, It is possible to prevent a contact error caused by a foreign material (abrasive material) that can give a high accuracy of thickness measurement, thereby improving the accuracy of thickness measurement.

The cooling water supply unit 170 supplies the cooling water to the polishing position so that the grinding wheel 130 can cool the frictional heat when the workpiece 10 is polished. The cooling water supply unit 170 includes a cooling water supply nozzle 171 and a cooling water pump 173 and a cooling water storage tank 175 connected to the cooling water supply nozzle 171 for forcibly supplying cooling water. The cooling water supply unit 170 is operated in conjunction with the polishing process to supply the cooling water to the polishing processing position. The supplied cooling water is recovered by a recovery unit (not shown), and the polishing powder is separated and collected by means of a magnet, a filter, etc., and then only the cooling water can be recovered to the cooling water storage tank 175 and reused.

The output unit 180 may include at least one of a speaker, an alarm lamp, and a display installed in the apparatus main body 110. The operator can check and check the operation state of the apparatus, the abnormal signal, the replacement signal, and the like by outputting the alarm signal, the operation signal, the check signal, and the timing of replacing the grinding tool through the output unit 180. For example, when the thickness of the workpiece 10 measured by the thickness measurement module 140 is measured to be equal to or less than a target thickness input from the input and setting unit 190, the control unit 200 controls the output unit 180 By outputting an abnormal signal, the operator can check the signal.

The input and output unit 190 is installed in the apparatus main body 110 and may include a plurality of input buttons, a touch pad, and the like as described above. The type and type of the workpiece 10, the polishing target thickness, the polishing time, the rotational speed of the grinding wheel 130, the dressing time, the dressing order, the number of dressings, the thickness of the grinding tool, Information and the like can be inputted and set.

The controller 200 controls the operation of the thickness measuring module 140 to measure the thickness of the workpiece 10 and controls the chuck table 120 and the grinding wheel 130 to perform the polishing process according to the measured result, And the operation of the cooling water supply unit 170 are controlled.

In order to precisely process the workpiece 10 to a desired thickness, the controller 200 controls the workpiece measurement module 140 to measure the workpiece before the polishing process, measures it during the polishing process, do.

Particularly, the controller 200 compares the information set by the input and setting unit 190 with the information measured by the thickness measuring module 140 to remove the driving of the grinding wheel 130, When the set values are not compared with each other, control is performed so that an alarm signal is output through the output unit 180. Therefore, it is possible to properly set erroneously set values or to classify workpieces that do not meet machining conditions. Further, since the workpiece 10 mounted on the chuck table 120 can be confirmed, it is possible to prevent the unnecessary polishing process from proceeding and to prevent the workpiece from being damaged.

Further, if the dressing process is performed using the dressing module 150, the thickness of the grinding tooth 131 may be changed, thereby affecting the polishing thickness in the polishing process in the future. The controller 200 predicts and calculates the polishing thickness of the grinding tool 131 on the basis of the change in thickness of the workpiece 10 measured by the thickness measuring module 140 so as to prevent and correct it. The control unit 200 compares the calculated polishing thickness of the grinding tooth 131 and the reference thickness stored in the storage unit 210 to determine whether the grinding tooth 131 is to be replaced, Lt; / RTI > Therefore, the operator can replace the grinding tool based on the grinding tool replacement information output through the output unit 180. [ The control unit 200 corrects the initial position value of the grinding wheel 130 based on the calculated thickness of the grinding tooth 131 and reflects the initial position value of the grinding wheel 130 so that the grinding process is performed .

The storage unit 210 stores and manages information input and set through the input and setting unit 190. For example, information such as the type of the workpiece 10, the target thickness of the workpiece 10, the initial thickness, the dressing processing time, the dressing cycle, the initial thickness of the grinding tool, and the thickness of the grinding tool compensation is stored and managed in the storage unit 210 . In addition, various inputs and set information can be stored.

A control method for grinding the workpiece 10 using the grinding apparatus having the above-described structure will be described.

First, the workpiece 10 placed on the chuck table 120 installed in the processing space 111 of the apparatus main body 110 is vacuum-adsorbed and fixed (S10). That is, the workpiece 10 is moved and mounted at the mounting position of the chuck table 120 using equipment such as a handler (not shown). In this state, When the button is operated, a vacuum suction force acts on the chuck table 120 to fix the workpiece 10 by vacuum suction.

Next, the control unit 200 acquires and stores a value that sets the machining conditions of the workpiece 10 fixed to the chuck table 120 (S12). That is, the operator inputs the information (the type and thickness of the workpiece) and the processing conditions (polishing thickness, error, number of polishing, dressing conditions, dressing cycle, etc.) .

In addition, the dressing condition may be separately set in the step S12 (S11). That is, in the step S11, a dressing time (before polishing, before and after processing) and a dressing cycle (number of times of polishing, polishing thickness, etc.) can be set.

The controller 200 controls the thickness measuring module 140 to obtain the initial thickness of the workpiece 10 fixed to the chuck table 120 in a state in which the information about the workpiece to be machined and the set values to be machined are obtained, And flatness are measured (S13). At this time, the control unit 200 drives and controls the air spraying unit 160 to spray the compressed air onto the surface of the workpiece 10 to be measured in thickness (S14). By injecting the compressed air to the thickness measuring position, foreign matter or the like at the position where the thickness is to be measured is removed, thereby improving the measurement accuracy of the thickness measuring module 140 and reducing the measurement error.

The controller 200 receives the measured value of the thickness of the workpiece 10 in the measurement step S13 and compares the input thickness information of the workpiece 10 with the set workpiece thickness information (S15).

If it is determined in step S15 that the measurement thickness is less than the processing condition, that is, the target thickness, the controller 200 outputs an alarm signal through the output unit 180 (S16). Then, when the alarm signal is output, the operator confirms whether the machining conditions of the workpiece are normally inputted and set, confirms the mounting state of the workpiece 10 to correct the wrong part, or removes the workpiece that does not meet the machining conditions The incidence of defective products can be remarkably reduced.

If it is determined in step S15 that the measured thickness satisfies the machining condition, the controller 200 moves the grinding wheel 130 to the machining position to perform the polishing process (S17).

That is, in the polishing process S17, the control unit 200 rotates the chuck table 120 and the grinding wheel 130 in opposite directions to rotate the workpiece 10 adsorbed and fixed on the chuck table 120 Polishing is performed. At this time, the control unit 200 drives and controls the cooling water supply unit 170 to cool the frictional heat by spraying the cooling water (cutting water) to the abrasive machining position of the workpiece 10, and controls the used cooling water to be recovered (S18).

After performing the polishing process S17 as described above for a preset machining time, the control unit 200 stops the polishing process and controls the thickness measuring module 140 so as to adjust the thickness of the workpiece 10 during polishing, (S19). At this time, it is also possible to precisely measure the thickness by removing the foreign substances (cooling water, abrasive particles, etc.) at the thickness measurement position by spraying the compressed air to the part for measuring the thickness secondarily by driving and controlling the air jet part 160 ).

The controller 200 determines whether the thickness of the workpiece measured in step S19 satisfies the target thickness (S210). If the target thickness is satisfied, the controller 200 determines whether the dressing process is performed (S22). In step S22, a criterion for determining whether or not to perform the dressing process may be determined by checking a dressing period stored in the storage unit 210, and the like. If it is confirmed that the dressing process is to be performed, a dressing process S27 to be described later is performed.

Another example of a criterion for judging whether or not the dressing process is performed in the step S22 is to measure the load acting on the grinding wheel 130 during the polishing process, It can be judged whether dressing is necessary or not. That is, when the load acting on the grinding wheel 130 is less than the reference value, it is determined that the grinding tooth 131 is worn and dulled, so that the dressing process can be performed.

On the other hand, if it is determined in step S21 that the measured thickness does not satisfy the target thickness, it is checked whether the dressing process is to be performed (S23). If the result of the determination is that it is not time to perform the dressing process, So that the measurement step S19 is repeated.

If it is confirmed in step S23 that the dressing process is to be performed, the controller 200 determines whether the dressing process is to be performed on the basis of the thickness variation measured in the first and second thickness measuring steps S13 and S19 The thickness of the grinding tooth 131 is calculated in anticipation of the polishing thickness (S24).

The controller 200 determines whether the thickness of the grinding tooth calculated in step S24 satisfies the reference thickness (S25). If it is determined that the thickness does not satisfy the reference thickness, the controller 200 outputs an alarm signal (S26). That is, when the thickness of the calculated grinding tooth is less than the reference thickness, it is determined that the grinding tooth is worn in a state unsuitable for use, and an alarm signal is output through the output unit 180 so that an operator or manager can grasp the grinding tooth 131 It can be replaced. Therefore, the grinding process can be normally performed using the grinding tool in the best state.

If the thickness of the grinding target satisfies the reference thickness in step S25, the controller 200 controls the dressing module 150 and the grinding wheel 130 to perform a dressing process (S27). A dressing process is performed for a predetermined time to dress the worn and dulled grinding teeth 131 so as to be in a state suitable for grinding.

After the dressing process, the controller 200 corrects the initial position of the grinding wheel based on the thickness of the grinding tooth 131 calculated in step S24 (S28). In other words, if the initial position value of the grinding wheel 130 is corrected by calculating the thickness of the grinding tooth 131 in consideration of the thickness change of the worn grinding tooth 131 through the grinding process, And the polishing conditions (polishing height, polishing time, and the like) are reset and performed based on the corrected initial position values, so that the polishing process can be effectively performed.

After correcting the initial position value of the grinding wheel 130 as described above, it is determined whether or not the polishing process is to be continued (S29), and the polishing process is continued or the polishing process is terminated.

As described above, according to the grinding apparatus control method of the present invention, since the workpiece can be grinded automatically while the thickness and the flatness can be automatically measured, the grinding process can be performed. Can be improved.

Further, by having a configuration capable of automatically dressing the grinding teeth before and after the machining operation, it is possible to maintain the state of the grinding tool well.

The thickness measurement module 140 measures the thickness before polishing and automatically measures the thickness after the dressing process so as to check whether the polishing process is normally performed or not, Can be predicted and calculated. In consideration of the thickness information of the grinding tooth 131 measured in this manner, the control unit 200 applies a value whose thickness has been changed by the dressing process to a correction value when controlling the grinding height of the grinding wheel 130, It is possible to compensate for the polishing operation position (height) of the wheel 130 and to control the workpiece 10 to a desired thickness quickly and precisely.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. Those skilled in the art will readily appreciate that many modifications and variations of the present invention are possible without departing from the spirit and scope of the appended claims.

100 .. Grinding device 110 .. Device body
120. Chuck table 130 .. Grinding wheel
140 .. Thickness measurement module 150 .. Dressing module
160 .. Air jetting section 170 .. Cooling water supply section
180 .. Output section 190 .. Input and setting section
200. Control unit 210. Storage unit

Claims (8)

Fixing a workpiece placed on a chuck table provided in a processing space of the apparatus main body by vacuum suction;
Acquiring and storing a value for setting a processing condition of a workpiece fixed to the chuck table;
A first measuring step of measuring an initial thickness and a flatness of a workpiece fixed to the chuck table;
Rotating the grinding wheel to grind the workpiece;
A second measuring step of measuring a thickness and a flatness of the workpiece during the grinding process;
Continuing the machining step so as to satisfy the set thickness and flatness according to the measurement result in the first measuring step, and when the measured result in the second measuring step satisfies the set thickness and flatness, ≪ / RTI >
Supplying and recovering cooling water during the processing step; And
And dressing a grinding tooth of the grinding wheel. The method according to claim 1,
Further comprising an air jetting step of jetting air to a measurement position of the workpiece in the first and second measuring steps. 3. The method according to claim 1 or 2,
Further comprising the step of outputting an alarm signal when the thickness of the workpiece measured in the first measuring step is equal to or less than a predetermined thickness. The method according to claim 3, wherein the cooling water supply and recovery step comprises:
Spraying cooling water to a polishing position during the machining process;
Recovering the injected cooling water;
Centrifuging the recovered cooling water to separate the sludge and the cooling water; And
And retransmitting the separated cooling water to the cooling water storage tank. 5. The method of claim 4, wherein the dressing comprises:
Wherein the grinding step is performed before the grinding step, during the machining step, and after the machining step,
Returning the grinding wheel to an initial position;
Raising the dressing tool located at the lower portion of the grinding wheel returned to the initial position using an actuator; And
And rotating the grinding wheel to grind the dressing tool to the dressing tool so as to dress the dressing tool. 6. The method of claim 5,
Wherein during the grinding process,
Wherein the load of the grinding wheel is measured and set to be performed when the measured load exceeds a set load. 3. The method according to claim 1 or 2,
Calculating a wear thickness of the grinding target based on the measured thickness of the workpiece measured in the first and second measuring apparatuses; And
Wherein the initial value of the grinding wheel is compensated during the machining process of the workpiece based on the wear thickness calculated in the step of calculating the wear thickness of the grinding tool. 8. The method of claim 7,
The dressing step may further include comparing the abrasion thickness of the grinding tooth calculated in the grinding toe wear thickness calculating step with the replacement reference thickness to determine the replacement time of the grinding tooth and outputting the replacement signal A grinding device control method.

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