JP2789166B2 - Grinding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for grinding a machine tool such as a surface grinder.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for higher precision microfabrication as represented by semiconductor technology. Since the development of NC (Numerical Control), machining accuracy has been dramatically improved by increasing the rigidity of each part of the machine and controlling the position. However, in order to achieve even higher precision in machining, it is necessary to improve the machining intelligence. You need to take your thoughts.

[0003] The intelligence of processing means that physical phenomena occurring at the processing site are taken as information by a sensor, input to a model prepared in advance, compared with the output from the model and a target value determined from the design, and the difference is calculated. In this case, the actuator is moved in accordance with the condition, and the phenomenon itself occurring in the processing is changed in real time to perform the intended processing.

FIG. 11 shows basic physical phenomena generated in processing. When the object is processed, a processing reaction force N and heat H are generated in the portion 100 where the processing is performed. In addition to this, the power source 10
Base 10 by heat generation from 1, heat and transmission of processing reaction force
2, various phenomena such as deformation of the structural body such as the column 103 and the head 104 and divergence of heat H and sound S to the surroundings occur simultaneously. In other words, all components are deformed by force and heat, and in order to achieve higher precision in processing, it is not enough to simply increase the precision by increasing rigidity or to systematize by combining conventional technologies. there were. Various physical phenomena at the time of processing include various information such as ambient temperature change A, deformation B of each structural member due to heat and force, temperature distribution C due to heat transfer, internal strain D, external strain E, and vibration F due to processing. Can be grasped as.

[0005] From such a viewpoint, various attempts have been made at present to produce specific machine tools in order to realize intelligent processing.

An object of the present invention is to provide a method for grinding a machine tool.

[0007]

In order to achieve the above object, according to the present invention, a planar shape of a table surface is detected, and a work is processed in a state where the work is placed on the table surface without applying force. Before detecting the planar shape of the work and grasping the shape of the work before processing, applying force to the work and closely contacting it according to the shape of the table surface, detecting the planar shape of the work, From the planar shape information of the deformed work and the planar shape information of the work in close contact with the table surface, the true thickness of the work and the clearance between the work and the table surface are obtained. The work surface of the work is fixed in close contact with the surface, the cutting amount of the grinding wheel is controlled by the amount of the clearance, and the surface grinding of the work is performed while maintaining the grinding wheel in a predetermined posture by the displacement generating means. Do And wherein the door.

[0008] The grinding wheel is characterized in that it generates a displacement in the direction of lifting the front end side in the feed direction and performs a relative feed operation to the work.

The relative feed operation is performed by moving the table with respect to the grindstone.

The present invention is characterized in that the posture of the work is detected, and the posture of the grindstone is changed in accordance with the change in the posture of the work so that the state of contact of the grindstone with the work is kept constant.

[0011] Information on the amount of deformation of the grindstone, the work and the table when the work force is applied to the work is prepared in advance as knowledge, and the work force applied to the work during grinding is detected.
Based on the detected processing force information and the deformation amount information, at least one of the grindstone and the table is deformed so as to cancel the deformation amount corresponding to the processing force. It is characterized in that the workpiece is ground in an infinite rigidity state with an apparent zero.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments.

FIG. 2 shows a conceptual configuration of the structure of the machine tool of the present invention, and FIG. 4 shows a more specific configuration example.

That is, as shown in FIG. 2, a spindle unit 2 of a motor body as a tool supporting portion for supporting a tool T, an RCC mechanism 3 for changing the attitude of the spindle unit, and a XY axis Move in the direction
A feed table 4 capable of controlling the posture in the Z-axis direction and the Mx and My directions, a processing table 5 fixed on the feed table 4 and serving as a work supporting portion for supporting the work W, and a force for detecting a force acting on the work. The detection unit 6 and the like are incorporated in a highly rigid structure 7.

The structure 7 is configured symmetrically with respect to the center axis of the spindle, so that lateral displacement occurs as symmetrically as possible.

Here, the RCC mechanism means a mechanism having an adjusting ability for controlling the attitude of the apparatus itself so as to maintain a predetermined attitude, in the sense of remote center compliance.

The structure 7 includes a fixed bed 8 on which the feed table 4 is supported, a head 9 on which the spindle unit 2 is supported, and a column 10 connecting the fixed bed 8 and the head 9. I have.

The feed table 4 can be moved in the XY axis direction via linear motion guide mechanisms 11 arranged in two directions of the X axis and the Y axis. Is performed by the feed screw mechanism 12, and a nano drive ring 40 is provided so as to enable fine movement feed as appropriate.

As shown in FIG. 6 (a), the linear motion guide mechanism 11 includes a track rail 111, a moving block 112 provided movably along the track rail 111, and opposing the track rail 111 and the moving block 112. And rolling elements 114 interposed between the rolling element rolling grooves 113a and 113b formed between the surfaces.

As shown in FIG. 4, the spindle unit 2 has a Z
The RCC mechanism 3 is mounted on the Z-axis table 13 guided in the axial direction.
Attached through.

The Z-axis table 13 is driven in the Z-axis direction via a screw feed mechanism 12 with a nano-drive ring for fine positioning using a nano-drive ring 40 for a large stroke ball.

Further, as shown in FIG.
A self-deformation monitor sensor 100 for monitoring the deformation of the structure 7 itself is provided. Self deformation monitor sensor 1
00 is appropriately provided on the fixed bed 5, the column 7 and the head 6, and monitors the deformation of each part.

FIGS. 1A and 1B show a specific configuration example of the spindle unit 2. As shown in FIG. 1, the spindle unit 2 includes a spindle 21 and a built-in type motor Ms integrated with the spindle 21, and a cooling pipe 23 that absorbs heat is provided on an outer periphery of the motor Ms. Be attached.

As the spindle 21, for example, a precision spindle such as a hydrostatic air bearing is used.

By mounting the RCC mechanism 3 between the spindle unit 2 and the Z-axis table 13, the tool T can be freely tilted with high precision or displaced in the Z direction via the spindle unit 2. It has become.

The RCC mechanism 3 is a ring member and includes an annular fixed ring 31 fixed to the end of the Z-axis table 13, a movable ring 32 fixed to the outer periphery of the spindle unit 2, and a fixed ring 31 and a movable ring. And an annular spring portion 33 having a thin annular flat plate structure. The annular spring portion 33 has an outer diameter end connected to the fixed ring 31 and an inner diameter end connected to the movable ring 32. The annular spring portion 33 is configured to be displaceable in a direction in which the spindle unit 2 is inclined with respect to the Z axis, which is a cutting axis direction, and in the Z axis direction, and is rigid in the horizontal direction and cannot be displaced. The annular spring portion 32 may not be a complete ring, but may have a hole-shaped notch.

The fixed ring 31 is a substantially L-shaped ring member, and has an inner peripheral surface having a stepped cylindrical outer diameter ring portion 311 and an inwardly extending inward extending from one end of the outer diameter ring portion 311 inward. And a flange portion 312. The movable ring 32 is a ring member having a substantially rectangular cross section. The outer periphery of the movable ring 32 is concentrically disposed at a predetermined distance from the inner periphery of the outer ring portion 311, and the upper end surface thereof is vertically aligned with the inward flange portion 312. They are arranged facing each other with a predetermined separation. The outer diameter end of the annular spring portion 33 is connected to the inner peripheral step portion 31 of the outer diameter ring portion 311.
3, the inner diameter end is connected to the upper end of the movable ring 21.

A piezoelectric element 34 as displacement means for changing the distance between the inward flange 312 and the fixed ring 32 is interposed between the inward flange 312 of the fixed space 31 and the upper and lower opposing surfaces of the fixed ring 32. Have been. This piezoelectric element 3
Reference numerals 4 are plurally arranged in the circumferential direction of the annular spring portion 33, and in this embodiment, are evenly arranged at four positions corresponding to the main feed direction and the transverse feed direction.

As the displacement means, in addition to the piezoelectric element and the electrostrictive element, a magnetostrictive element, a thermal actuator which expands and contracts by utilizing thermal expansion of an object, an actuator which expands and contracts by fluid pressure, a voice coil and a magnetostrictive element, and the like can be used. In short, various actuators that expand and contract in proportion to the command value based on the command value can be used.

On the other hand, a strain gauge 35 is attached to the base of the annular thin portion 33 at the base of the fixed ring 31 or the movable ring 32, and the displacement of the spindle unit 2 and the force and displacement acting on the spindle unit 14 are reduced. It can be detected.

As means for detecting the displacement, in addition to a resistance type sensor such as a strain gauge, an electromagnetic induction type sensor such as a differential transformer or an eddy current sensor, a capacitance type sensor or the like can detect a minute displacement. Various sensors can be used.

As the force detecting means, an elastic member which is elastically deformed in response to a load, and a force acting from a detected value of the distortion of the elastic member may be detected.

FIG. 1C schematically shows the operation state of the RCC mechanism 3 (a contracted state). For example, if one of the piezoelectric elements 34 located at positions facing each other is contracted and the other is extended, the piezoelectric element 34 is inclined. Further, by selecting the piezoelectric element 34 to be expanded and contracted, the spindle unit 2 can be inclined in any direction.

If the amount of expansion and contraction of all the piezoelectric elements 34 is set to be the same, the tool T is displaced in the Z-axis direction while maintaining the same posture.

As described above, the RCC mechanism 3 generates a displacement so that the tool is displaced by itself and assumes a predetermined posture. The predetermined posture can be variously set depending on the cutting conditions and the like, but usually, in the case of a surface processing tool such as a surface grinder, the posture of the tool is controlled such that the front end in the feed direction is lifted. .

That is, as shown in the dotted line of FIG. 3A and FIG. 3D, in the case of a normal tool, when the tool is fed, the head on the front front side in the feed direction is lowered due to the frictional reaction force, and the work surface is cut. Cannot get high precision flatness. Therefore, as shown in FIG. 3B, the posture of the cup grindstone T as a plane machining tool is caused to be angularly displaced so that the head on the front end side in the feed direction of the cup grindstone T is lifted, thereby preventing biting into the machining surface. I do. In this case, since it has an active element such as the piezoelectric element 34, it is an active RCC mechanism (active RCC mechanism).

Further, instead of the active RCC mechanism 3, the movement of the cup grindstone T in the reverse feed direction is changed to the movement of the cup grindstone T in the direction in which the front end of the cup grindstone T moves away from the workpiece W, as shown in FIG. Motion conversion mechanism 3 such as link mechanism for conversion
A passive configuration may be provided in which the front end of the tool in the feed direction can be lifted by a feed reaction force acting on the tool during the tool feed operation mechanically.

The Z-axis table 13 is a hollow frame, and is guided in the Z-axis direction through a pair of linear motion guide mechanisms 14 arranged parallel to each other on the inner periphery of a mounting hole 601 provided in the structure head 6. Is done.

The feed screw mechanism 12, as shown in FIG.
A ball screw shaft 121 and a nut 123 screwed to the ball screw shaft 121 via a number of balls 122
And a nano drive ring 40 interposed between the ball nut 123 and the member to be fed 124.

The nano drive ring 40 has a ring-shaped spring 41 which is displaced in the axial direction, and a piezoelectric element 42 as a displacement means which expands and contracts by an electric signal.

When a voltage is applied to the piezoelectric element 42, FIG.
As shown in (b), the piezoelectric element 42 expands and the member to be fed 124 is finely fed. Further, the fine movement feed amount can be detected by the strain gauge 43 attached to the ring-shaped spring 41,
Driven precisely by feedback control. The ring-shaped spring 41 includes a fixed ring 411 fixed to the nut 123 and a movable ring 4 fixed to the feed member 124.
12 and a flat annular portion 413 connecting the fixed ring 411 and the movable ring 412.

As shown in FIGS. 6A to 6D,
An actuator 50 that can expand and contract in the Z-axis direction is incorporated in each moving block 112 of the linear guide mechanism 11 that supports the feed table 4 so that the attitude of the feed table 4 can be controlled.

The actuator 50 has the same basic structure as the nano drive ring 40. A piezoelectric element 52 as a displacement means that expands and contracts by an electric signal is incorporated in a ring-shaped spring 51 that is displaced in the Z-axis direction. I have.

When a voltage is applied to the piezoelectric element 52, the piezoelectric element 52 expands and the feed table 4 is displaced in the Z-axis direction.
In addition, the displacement in the Z-axis direction can be detected by the strain gauge 53 attached to the ring-shaped spring 51, and the drive is precisely performed by feedback control. The ring-shaped spring 51 includes a fixed ring 511 fixed to the moving block, a movable ring 512 fixed to the table 4, and a flat annular portion 513 connecting the fixed ring 511 and the movable ring 512. . The fixed ring 511 is provided with a stopper portion 514 protruding upward, and abuts on the lower surface of the movable ring 512 to position the lower limit position.

By this actuator 50, FIG.
As shown in (e) to (h), the attitude of the table 4 can be freely changed, and by directly correcting the running parallelism, pitching, and rolling of the table 4, it has not been possible in the past. Such accuracy can be obtained.

FIG. 8 shows a six-component table constituting the working table 5. A grip 5a such as a vacuum chuck for gripping the work W is provided at the center of the processing table 5, and a force detector 6 for detecting a force acting on the work W is provided therearound.

Further, a non-contact laser displacement meter 70 is provided as a measuring device for measuring the planar shape of the work W gripped on the processing table 5, and combined with the feed of the feed table 4 in the XY directions. The surface shape of the work W can be measured and grasped. It is effective to check the shape of the workpiece W before, during, and after processing.

When the machine tool is a surface grinder and the tool is a cup grindstone, a dresser fixed to the table is preferably provided at an appropriate position on the feed table 4 for dressing the cup grindstone.

In order to minimize the influence of heat on the deformation, the temperature of the grinding oil and the cooling medium of the spindle unit and the motor for driving the table can be adjusted by separate devices. .

As described above, this machine tool has the following functions. (A) Attitude control function of spindle 2 (b) Attitude control function of work W (table 4) (c) Ultra-fine movement feed function by screw feed mechanism 12 with nano drive ring (d) Shape grasp function of work w (e) Processing force grasping function (f) Self-deformation monitoring function (g) Infinite rigidity function Each function will be described below.

(A) Attitude control function of the spindle unit 2 An air spindle 21 rotatably supported by a static pressure air bearing is used as the spindle 2, and a piezoelectric element 312 and a strain gauge 35 are incorporated between the Z-axis table 13. By attaching the elliptical RCC mechanism 3, the tool T can be freely inclined with high precision via the spindle 2 or displaced in the Z direction.

(B) Attitude Control Function of Work W (Table 4) As shown in FIGS. 6 (e) to 6 (h), the table 4 is moved by the actuators 50 provided on the plurality of moving blocks 12 of the linear motion guide mechanism 11. Position, and thus the position of the workpiece W, can be freely changed, and by directly correcting the running parallelism, pitching, and rolling of the table 4, it is possible to obtain an accuracy that could not be obtained conventionally. become.

(C) Ultra-fine movement feed function by the screw feed mechanism 12 with the nano drive ring 40 Just by attaching the nano drive ring 40 to the nut 123 of the ball screw, it is possible to drive at a high resolution that could not be considered by motor drive. This is a fine movement feed function.

In this embodiment, the screw feed mechanism 12 in the X-axis and Y-axis directions and the screw feed mechanism 12 in the Z-axis direction are all provided, so that the feed amount can be controlled with ultra-high precision, and The amount of cut can be made.

(D) A function for grasping the shape of the work W, etc. A non-contact laser displacement meter 70 is provided, and the height of the work W in the XY plane coordinates is measured in combination with the feed table 4 so that the work W can be measured. Can grasp the planar shape of. It is effective to check the shape of the workpiece before, during and after processing.

The flatness of the table surface and the flatness of the workpiece (the two types, ie, when the workpiece is allowed to stand without being restrained on the table and when the workpiece is restrained and fixed), are used. It is preferable that each measurement can be repeated in-line.

The measurement by the displacement meter 70 is configured so that after the tool T retreats upward in the cutting direction after machining, the tool T moves on the measurement surface and can measure the displacement.

(E) Working force grasping function In order to know the working force point of the tool T, the working force is converted into six axes (the axial force in the cutting direction, the main feed direction and the transverse feed direction, and the rotation around the axis in those directions). Is configured to be able to detect the moment.

(F) Self-deformation monitoring function The deformation of the column 10 can be monitored by a group of deformation sensors attached to the column 10. Column 1 due to heat generated during processing
By using the information of the deformation of 0 to know the change in the posture of the tool and the work, the deformation can be corrected by controlling the posture of the tool or the work, and ultra-precision machining can be realized.
Preferably, this deformation of the column 10 can be detected with minimum resolution by a method having an internal reference in the device.

(G) Infinite rigidity function The displacement of each part of the machine with respect to the load is examined and grasped.
By correcting the displacement according to the processing force from the axial force sensor 6, it is possible to perform processing as if the rigidity is infinite.

In the machine tool having the above-described configuration, the posture of the tool T, the displacement in the cutting direction (Z-axis direction), and the transverse feed direction orthogonal to the main feed direction (X-axis direction) and the main feed direction (Y-axis direction). It is preferable to detect a total of three axes of the inclination and to perform real-time control so that it becomes an arbitrary magnitude.

Further, a total of three axes, ie, the posture of the workpiece gripping portion of the processing table 5 (same as the posture of the feed table 4), the displacement in the cutting direction, and the inclination in the main feed direction and the transverse feed direction orthogonal to the main feed direction are shown. Preferably, it can be detected and controlled in real time so that it can be of any size.

For real-time control, it is preferable to have a computer / interface similar to a personal computer.

FIG. 10 shows a schematic control configuration of the machine tool.

The RCC mechanism 3 for controlling the tool attitude and the actuator 50 for controlling the table attitude are based on information on the attitude of the spindle unit 2 and the working table 5 obtained from an external sensor or a force sensor or displacement sensor. The posture of the processing table 5 is a linear motion guide mechanism 11
The rails 111, the moving block 112, the base 8 of the structure, the ball screw shaft 121, the ball nut 122, and the like change depending on the deformation of each system component, and the attitude of the tool T is also the linear motion guide of the Z-axis table 13. Mechanism 14
Ball screw shaft 121 or column 10 of the structure itself
It changes due to deformation of components such as the head 9 and the like, and the deformation of each component is generated by heat and force.

In order to know the attitude of the processing table 5 and the tool T, a displacement sensor 70 for directly viewing the attitude of the processing table 5 and the tool T, and a visual sensor such as a video camera can be used. Further, instead of directly detecting the attitude of the machining table 5 or the tool T, the amount of deformation of each component may be detected. To detect the amount of deformation of each component, the amount of deformation of the component may be directly detected, or the distortion may be detected. Further, the amount of deformation may be calculated by detecting heat and force applied to each component. Furthermore, since it is conceivable that the vibration characteristics including sound change depending on the internal force state of each component, the vibration characteristics may be detected as posture information. In short, all components generate information as distortion, temperature, sound, shape, and the like, and the control device 201 uses the tool T based on all available information among the information generated from these components. In addition, by recognizing the attitude of the processing table 5, each minute displacement amount is calculated, and the driving of the RCC mechanism 3 and the actuator 50 is controlled through the driving drivers D3 and D50.

When the machine tool 1 of the present invention is applied to a grinder, the ultra-high-precision flat surface grinding required for photomasks, silicon wafers, etc., which has been difficult with conventional grinding, is achieved by incorporating various sensors and actuators. This is made possible by the use of intelligent machine elements.

FIG. 9 shows a procedure for performing the soft mode.

[Procedure] The plane shape of the work holding portion 5a of the processing table 5 is grasped by the displacement meter 70 without placing the work W. In order to grasp the planar shape, the Z displacement of the work gripping portion 5a is transmitted to the feed table 4 in the XY direction, and the Z displacement is calculated by the internal sensor.
All points on the Y coordinate plane are measured and stored (see FIG. 9A).

Then, the Z displacement of the processing table 5 is 0.1
[Μm], the output of the piezoelectric element 52 of the actuator 50 is measured at multiple points and stored, and 0.1 [μm] / 2
Ensure accuracy of 00 [mm]

[Procedure] Next, the work W is placed on the work holding portion 5a without suction, and the planar shape of the work W is grasped. Without sucking the work W into the work holding portion 5a of the work W, the Z
The displacement is measured and stored at all points in the XY directions.

The Z displacement of the work W is a dimension obtained by adding the clearance between the work holding portion 5a of the work W and the lower surface of the work W and the thickness of the work W. (See FIG. 9B)

[Procedure] Next, the work W on the work holding portion 5a is sucked and the lower surface of the work W is brought into close contact with the work mounting portion 5a so that there is no gap. The planar shape of the workpiece W in this state is
As Z displacement.

The Z displacement of the work is the thickness of the work (see FIG. 9C).

[Procedure] All the Z displacements of the processing table 5 are measured and stored in advance by an external sensor, and the output of the piezoelectric element 52 of the actuator 50 such that the Z displacement becomes zero is measured in the same manner as in the procedure. Calculate and store.

[Procedure] Grinding (a certain height)-(gap) is the thickness of the work W. In order to obtain a flat surface, the gap is added to the cut amount to grind the entire cut (FIG. 9 (d)). )reference).

At this time, the attitude of the cup grindstone T is controlled to slightly lift the front end in the feed direction by using the RCC mechanism 3 as described above.

[Procedure] All the points of the Z displacement of the work W (7) are measured without chucking the work W. It should be a flat surface, and if not, it is corrected and the procedure is repeated (see FIG. 9E).

-Execution of the hard mode-The procedure is the same.

As a procedure, non-deformable gripping is performed using a hot wax or ice chuck and a multi-point extruding table.

Are the same. Procedure Work flat and grind itself in infinite rigidity mode.

Procedure All points were measured, and it should have been a flat surface. If not, grinding was repeated in infinite rigidity mode.

[0083]

As described above, according to the present invention,
Super-high precision flat surface grinding becomes possible.

[Brief description of the drawings]

FIGS. 1A and 1B show a tool posture control device according to an embodiment of the present invention. FIG. 1A is a schematic sectional view, and FIG.
2 is a bottom view, and FIG. 2C is a sectional view of a main part of the RCC mechanism.

FIG. 2 is a perspective view showing a conceptual configuration of a structure of a machine tool according to one embodiment of the present invention.

FIG. 3 is an explanatory diagram of a posture control mechanism.

FIG. 4 is a diagram showing a more specific configuration of a machine tool according to one embodiment of the present invention.

FIG. 5 is a configuration diagram of a ball screw feed mechanism with a nano drive ring.

6 (a) to 6 (d) are views showing a linear motion guide mechanism provided with an actuator for controlling the attitude of a feed table,
FIGS. 7E to 7H are explanatory diagrams of the attitude control state of the feed table.

FIG. 7 is a view showing a mounting position of a deformation sensor of the structure.

FIG. 8 is a diagram showing a processing table and a displacement sensor.

FIG. 9 is a diagram showing an example of a grinding procedure.

FIG. 10 is a diagram showing a control configuration.

FIG. 11 is a diagram showing basic physical phenomena occurring in machining of a machine tool.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 machine tool 2 spindle unit 3 RCC mechanism (displacement generating means) 4 feed table 5 processing table (work supporting part) 6 force sensor 7 structure 8 fixed base 9 head 10 column 11 linear motion guide mechanism 12 ball screw feed mechanism 13 Z Axis table 40 Nano drive ring 50 Posture control actuator 60 Joint member for whirling absorption 70 Displacement sensor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B23Q 15/013 B23Q 15/14 B23Q 17/20 B24B 7/00-7/08 B23C 3/00 H01L 21 / 304

Claims (5)

(57) [Claims] 1. A flat shape of a table surface is detected, and a flat shape of the work is detected before processing in a state where the work is mounted on the table surface without applying a force to grasp the shape of the work before processing. Applying a force to the workpiece to closely adhere to the shape of the table surface to detect the planar shape of the workpiece, the planar shape information of the undeformed workpiece on the table surface and the planar shape of the workpiece in close contact with the table surface The true thickness of the work and the clearance between the work and the table surface are obtained from the shape information, and during grinding, a force is applied to the work to fix it in close contact with the table surface, taking into account the clearance of the work surface of the work. A grinding method characterized in that the cutting amount of the grinding wheel is controlled by the amount of the cutting, and the surface of the work is ground while maintaining the grinding wheel in a predetermined posture by the displacement generating means. 2. The grinding method according to claim 1, wherein the grinding wheel performs a relative feeding operation with respect to the workpiece by generating a displacement in a direction of lifting a front end side in a feeding direction. 3. The grinding method according to claim 2, wherein the relative feed operation is performed by moving a table with respect to the grindstone. 4. The method according to claim 1, wherein the posture of the work is detected, and the posture of the grindstone is changed according to the change of the posture of the work to keep the state of contact of the grindstone with the work constant.
4. The grinding method according to 2 or 3. 5. Preliminarily, information on the amount of deformation of a grindstone, a work and a table when a work force is applied to a work is prepared as knowledge, and the work force applied to the work during grinding is detected.
Based on the detected processing force information and the deformation amount information, at least one of the grindstone and the table is deformed so as to cancel the deformation amount corresponding to the processing force. The grinding method according to claim 1, 2, 3, or 4, wherein the workpiece is ground in an infinite rigidity state with an apparent zero.