GRINDING PROCESSING APPARATUS

Abstract

A grinding processing apparatus according to an embodiment includes: a rotary table configured to be rotatable and to hold a workpiece; a grinder including a rotation unit and configured to grind a surface of the workpiece held by the rotary table by rotation of the rotation unit; a holding unit configured to hold the grinder such that a rotation axis of the rotation unit forms an angle exceeding 0 degrees and being 60 degrees or less to a vertical axis; a horizontal movement slider configured to slide the holding unit in a horizontal direction in a state where a tip tool of the rotation unit is in contact with the workpiece; and a controller configured to control rotation of the rotary table and the rotation unit, and to control the grinder to linearly slide between a center side and an outer peripheral side of the workpiece.

Claims

1. A grinding processing apparatus, comprising: a rotary table configured to be rotatable and to hold a workpiece; a grinder including a rotation unit and configured to grind a surface of the workpiece held by the rotary table by rotation of the rotation unit; a holding unit configured to hold the grinder such that a rotation axis of the rotation unit forms an angle exceeding 0 degrees and being 60 degrees or less to a vertical axis; a horizontal movement slider configured to slide the holding unit in a horizontal direction in a state where a tip tool of the rotation unit is in contact with the workpiece; and a controller configured to control rotation of the rotary table and the rotation unit, and to control the grinder to linearly slide between a center side and an outer peripheral side of the workpiece.

2. The grinding processing apparatus according to claim 1, wherein the tip tool of the grinder is a cup brush-type wire brush.

3. The grinding processing apparatus according to claim 2, wherein a diameter of a steel wire of the wire brush of the grinder is 0.01 mm or more and 2 mm or less.

4. The grinding processing apparatus according to claim 3, wherein the steel wire is any of a hard steel wire and a plated steel wire.

5. The grinding processing apparatus according to claim 1, wherein, in a case where the angle is formed by tilting an upper side of the rotation axis from the vertical axis toward one direction of two directions along an axis orthogonal to the vertical axis, the controller is configured to slide the grinder in another direction along the orthogonal axis.

6. The grinding processing apparatus according to claim 1, wherein the controller is configured to control the horizontal movement slider to horizontally move the grinder from the outer peripheral side to the center side of the workpiece.

7. The grinding processing apparatus according to claim 1, wherein the controller is configured to control the horizontal movement slider to horizontally move the grinder from the center side to the outer peripheral side of the workpiece.

8. The grinding processing apparatus according to claim 1, wherein the controller is configured to control the rotary table to cause a rotational speed of the workpiece to be 3000 rpm or more and 6000 rpm or less.

9. The grinding processing apparatus according to claim 1, wherein the controller is configured to control the grinder to cause a rotational speed of the rotation unit to be 1000 rpm or more and 15000 rpm or less.

10. The grinding processing apparatus according to claim 1, wherein the controller is configured to control the horizontal movement slider to cause a speed of horizontal movement of the grinder to be 0.5 m/s or more and 5.0 m/s or less.

11. The grinding processing apparatus according to claim 1, wherein the controller is configured to control a rotational speed of the rotary table and a speed of horizontal movement of the grinder to cause each of positions on a surface of the workpiece to come into contact with the tip tool and be ground a same number of times as number of times of grinding at other positions.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Each of FIGS. 1A and 1B shows schematic diagrams illustrating a configuration example of a grinding processing apparatus according to an embodiment.

[0008] FIG. 2 is a block diagram illustrating functions of the grinding processing apparatus according to the embodiment.

[0009] Each of FIGS. 3A and 3B shows diagrams for describing movement of a grinder in the grinding processing apparatus according to the embodiment.

[0010] FIG. 4 is a diagram illustrating a width of a contact surface with a rotation unit in the grinding processing apparatus according to the embodiment.

[0011] FIG. 5 is a diagram for describing a method of measuring variation in surface roughness in the grinding processing apparatus according to the embodiment.

[0012] FIG. 6 is a schematic diagram illustrating an example of a rotary table of the grinding processing apparatus according to the embodiment as viewed from obliquely above.

DETAILED DESCRIPTION

[0013] A grinding processing apparatus according to an embodiment is described in detail below with reference to drawings.

[0014] A grinding processing apparatus according to an embodiment includes: a rotary table configured to be rotatable and to hold a workpiece; a grinder including a rotation unit and configured to grind a surface of the workpiece held by the rotary table by rotation of the rotation unit; a holding unit configured to hold the grinder such that a rotation axis of the rotation unit forms an angle exceeding 0 degrees and being 60 degrees or less to a vertical axis; a horizontal movement slider configured to slide the holding unit in a horizontal direction in a state where a tip tool of the rotation unit is in contact with the workpiece; and a controller configured to control rotation of the rotary table and the rotation unit, and to control the grinder to linearly slide between a center side and an outer peripheral side of the workpiece.

[0015] Each of FIGS. 1A and 1B shows schematic diagrams illustrating a configuration example of a grinding processing apparatus 1 according to the embodiment. As illustrated in FIGS. 1A and 1B, the grinding processing apparatus 1 includes a rotary table 10, a grinder 20, a holding unit 30, an elevation slider 40, a horizontal movement slider 50, and a control apparatus 60.

[0016] The rotary table 10 can hold a workpiece P, and can rotate around a vertical axis C1 by a driving mechanism (not illustrated) such as a motor. Representative examples of a material of the workpiece include aluminum, titanium, and stainless steel. The workpiece P has a diameter of about 100 mm or more and about 600 mm or less.

[0017] As illustrated in FIG. 6, the rotary table 10 preferably has holes 101 penetrating through the rotary table 10. When the rotary table 10 has the holes 101, fingers (or jigs) can be inserted into the holes 101 from a lower side of the rotary table 10 to push out upward the workpiece P on the rotary table 10 after grinding processing of the workpiece P is finished. By the operation, the workpiece P can be easily detached from the rotary table 10.

[0018] The number of holes 101 may be plural (for example, three) as illustrated in FIG. 6, or one. In a case where one hole 101 is provided, the hole 101 has, for example, a partially-discontinuous annular shape (hereinafter, referred to as substantially annular shape). When one hole 101 (having substantially annular shape) or the plurality of holes 101 are provided as described above, detachment is easily performable irrespective of a stop position of the rotary table 10, which is preferable. More preferably, the plurality of holes 101 are provided. This is because, when the plurality of holes 101 are provided as described above, the gravity and the like applied to a portion supporting a portion inside the holes 101 of the rotary table 10 caused by provision of the holes 101 can be dispersed, and it is unnecessary to make the rotary table 10 thick more than necessary.

[0019] The plurality of holes 101 provided in the rotary table 10 are preferably disposed at positions such that a gravity center configured by centers of the plurality of holes 101 is substantially coincident with a rotation center of the rotary table 10. As a first example, the plurality of holes 101 are disposed such that centers of the even number of holes 101 provided in the rotary table 10 are at positions substantially point symmetrical about the rotation center of the rotary table 10. The positions substantially point symmetrical about the rotation center of the rotary table 10 are defined as positions deviated by 30 degrees or less from respective positions point symmetrical about the rotation center of the rotary table 10. As a second example, the plurality of holes 101 are disposed such that a gravity center configured by centers of three or more odd number of holes 101 is substantially coincident with the rotation center of the rotary table 10. For example, in a case where three holes 101 are provided, the three holes 101 are disposed at positions of 0 degrees, 120 degrees, and 240 degrees (angle deviation by about 30 degrees is allowed) on a circumference of an x-z plane around the rotation center of the rotary table 10. As described above, the plurality of holes 101 provided in the rotary table 10 are disposed such that the gravity center configured by the centers of the plurality of holes 101 is substantially coincident with the rotation center of the rotary table 10. This makes it possible to reduce backlash of the workpiece P when the rotary table 10 is rotated.

[0020] Further, as illustrated in FIG. 6, the rotary table 10 preferably includes convex portions 102. The number of convex portions 102 may be one or plural as illustrated in FIG. 6.

[0021] In a case where one convex portion 102 is provided, the convex portion 102 may have a substantially annular shape. The convex portions 102 are preferably disposed near an outer peripheral portion (outside of workpiece P). When the convex portions 102 are disposed on the outside of the workpiece P as described above, even if the rotary table 10 is slightly inclined (for example, due to pushing of grinder 20), centrifugal force can prevent the workpiece P from falling, which is preferable.

[0022] Each of the convex portions 102 preferably has a structure that includes a hard body integrated with (or connected to) the rotary table 10 at a center part and includes an annular elastic body at an outer peripheral part.

[0023] In a case where the outer peripheral part of each of the convex portions 102 is made of the elastic body, even when the convex portion 102 and the workpiece P come into contact with each other, the convex portion 102 hardly damages the workpiece P, which is preferable. In contrast, in a case where each of the convex portions 102 is wholly made of the elastic body, capability for supporting and preventing the workpiece P from falling may be reduced. Therefore, each of the convex portions 102 preferably includes the hard body at the center part.

[0024] A height of each of the convex portions 102 is preferably or more and two times or less of a thickness of the workpiece P. When the height of each of the convex portions 102 is lower than of the thickness of the workpiece P, the function of preventing the workpiece P from falling may not be sufficiently exerted. In contrast, when the height of each of the convex portions 102 is higher than two times of the thickness of the workpiece P, a possibility that the workpiece P falls at placement of the workpiece P or at removal of the workpiece P is increased, which is not preferable.

[0025] The grinder 20 includes a main body unit 21 and a rotation unit 22, and can rotate the rotation unit 22 around a rotation axis C2. As illustrated in FIG. 4, the rotation unit 22 of the grinder 20 includes a rotary shaft (for example, spindle) 221, and a tip tool 222 detachably connected to a front end of the rotary shaft 221. The grinder 20 brings the tip tool 222 of the rotation unit 22 into contact with a surface of the workpiece P held by the rotary table 10, and grinds the surface of the workpiece P. The tip tool 222 includes a grinding stone, a file, or a cup brush-type wire brush.

[0026] The holding unit 30 holds the grinder 20 such that an angle (hereinafter, referred to as grinder angle in some cases) of the rotation axis C2 of the rotation unit 22 of the grinder 20 to a vertical axis C3 exceeds 0 degrees and is 60 degrees or less. The grinder angle means an angle formed by tilting an upper side of the rotation axis C2 of the rotation unit 22 from the vertical axis C3 toward a positive direction of two directions of a z-axis. More preferable grinder angle is 10 degrees or more and 50 degrees or less.

[0027] The grinder 20 preferably brings the tip tool 222 into contact with the workpiece P after three or more seconds elapse from rotation start of the rotation unit 22 at the preferable grinder angle . When three or more seconds elapse from rotation start of the rotation unit 22 as described above, a rotational speed of the rotation unit 22 when the tip tool 222 comes into contact with the workpiece P can be controlled. Therefore, when the rotational speed of the rotation unit 22 is controlled to a certain rotational speed during a period from start to end of the grinding, partial difference of surface roughness of the workpiece P can be reduced. Further, a time from rotation start of the rotation unit 22 until the rotation unit 22 comes into contact with the workpiece P may be appropriately changed based on an acceleration of the rotation unit 22.

[0028] The elevation slider 40 can be elevated in a vertical direction, namely, in a y-axis direction while holding the holding unit 30. Elevation of the holding unit 30 by the elevation slider 40 makes it possible to control contact/non-contact of the tip tool 222 of the rotation unit 22 of the grinder 20, to the surface of the workpiece P. In addition, elevation of the holding unit 30 by the elevation slider 40 makes it possible to control pushing pressure of the tip tool 222 of the rotation unit 22 of the grinder 20, to the surface of the workpiece P.

[0029] The horizontal movement slider 50 can move in a horizontal direction, namely, in the z-axis direction while holding the elevation slider 40 (arrow in FIG. 1B). Horizonal movement of the elevation slider 40 by the horizontal movement slider 50 makes it possible to control a contact position on the surface of the workpiece P by the tip tool 222 of the rotation unit 22 of the grinder 20.

[0030] As illustrated in FIG. 2, the control apparatus 60 includes a processing circuit 61 and a memory 62. The processing circuit 61 includes a dedicated or general-purpose processor that realizes various kinds of functions by executing programs stored in the memory 62. The term processor includes a processor such as a graphics processing unit (GPU) in addition to a dedicated or general-purpose central processing unit (CPU).

[0031] The processing circuit 61 may further include a hardware element such as an application specific integrated circuit (ASIC) and a programmable logic device (for example, simple programmable logic device (SPLD), complex programmable logic device (CPLD), or field programmable gate array (FPGA)). In a case where the processing circuit 61 includes the ASIC, functions corresponding to the programs are directly incorporated as logic circuits in the ASIC in place of the programs stored in the memory 62. The processing circuit 61 can realize various kinds of functions by combining software processing using the processor and hardware processing using the hardware element such as the ASIC.

[0032] In a case where the processing circuit 61 includes the processor, the functions may be realized by a single processor, or a plurality of independent processors may be combined to configure a processing circuit, and the processors may realize the respective functions. In a case where the plurality of processors are provided, the memory 62 storing the programs may be provided individually for each processor, or one memory 62 may collectively store the programs corresponding to the functions of all processors.

[0033] The memory 62 includes, for example, a semiconductor memory element such as a random access memory (RAM) and a flash memory, a hard disk, and an optical disk. The memory 62 may include a portable medium such as a universal serial bus (USB) memory and a digital video disk (DVD). The memory 62 stores various kinds of processing programs (including operating system (OS), etc., in addition to application programs) used by the processing circuit 61, and data necessary for execution of the programs.

[0034] The processing circuit 61 functions as a controller, and realizes a table rotation control unit F1, a grinder rotation control unit F2, a grinder elevation control unit F3, and a grinder horizontal movement control unit F4 by executing computer programs stored in the memory 62 or a non-transitory recording medium such as a memory inside the processing circuit 61. All or a part of the units F1 to F4 is not limited to realization by the control apparatus 60 executing the computer programs, and may be provided as circuits such as an ASIC in the control apparatus 60.

[0035] The table rotation control unit F1 has a function of rotating the workpiece P held by the rotary table 10 around the vertical axis C1 by controlling a driving mechanism (for example, motor) rotating the rotary table 10 to rotate the rotary table 10. The table rotation control unit F1 rotates the rotary table 10 such that a rotational speed of the rotary table 10 becomes 50 Hz or more and 100 Hz or less, namely, 3000 rpm or more and 6000 rpm or less. The rotational speed of the rotary table 10 is preferably 90 Hz or more and 100 Hz or less, namely, 5400 rpm or more and 6000 rpm or less. This is because, when the rotational speed of the rotary table 10 is less than 5400 rpm, a portion that cannot be ground may be generated. The rotational speed of the rotary table 10 is desirably determined in relation to a speed of horizontal movement described below.

[0036] The grinder rotation control unit F2 has a function of rotating the rotation unit 22 around the rotation axis C2 by controlling a driving mechanism (for example, motor) rotating the rotation unit 22. The grinder rotation control unit F2 controls the grinder 20 such that a rotational speed of the rotation unit 22 becomes 1000 rpm or more and 15000 rpm or less. When the rotational speed of the rotation unit 22 is less than 1000 rpm, the grinding processing may not be performed. In contrast, when the rotational speed of the rotation unit 22 exceeds 15000 rpm, rotation becomes unstable, and the processing cannot be performed with high accuracy. The rotational speed of the rotation unit 22 is preferably 5000 rpm or more and 11000 rpm or less.

[0037] The grinder elevation control unit F3 has a function of elevating the grinder 20 in the y-axis direction by controlling a driving mechanism (for example, motor) elevating the holding unit 30 by rotational movement. FIG. 3A illustrates the grinder 20 disposed at a grinding processing start position. The grinder elevation control unit F3 can control contact/non-contact of the tip tool 222 of the rotation unit 22 of the grinder 20, to the surface of the workpiece P by controlling elevation of the holding unit 30. Further, the grinder elevation control unit F3 can control pushing pressure of the tip tool 222 of the rotation unit 22 of the grinder 20, to the surface of the workpiece P by controlling elevation of the holding unit 30.

[0038] The grinder horizontal movement control unit F4 has a function of horizontally moving (horizontally sliding) the grinder 20 in the z-axis direction (positive direction or negative direction of z-axis) by controlling a driving mechanism (for example, motor) horizontally moving the elevation slider 40 by rotational movement. FIG. 3B illustrates the grinder 20 disposed at a grinding processing end position after the grinder 20 is horizontally moved in the negative direction of the z-axis from the state illustrated in FIG. 3A. The grinder horizontal movement control unit F4 can control the contact position (position along radial direction of workpiece P) on the surface of the workpiece P by the tip tool 222 of the rotation unit 22 of the grinder 20 by controlling horizontal movement of the elevation slider 40. The grinder horizontal movement control unit F4 horizontally moves the elevation slider 40 such that a speed becomes 0.5 m/s or more and 5.0 m/s or less. The speed of horizontal movement of the elevation slider 40 is preferably 0.5 m/s or more and 2.0 m/s or less. This is because, when the speed of horizontal movement of the elevation slider 40 exceeds 2.0 m/s, a portion that cannot be ground may be generated. The speed of horizontal movement of the elevation slider 40 is desirably determined in relation to the rotational speed of the rotary table 10.

[0039] The rotational speed of the rotary table 10 and the speed of horizontal movement of the grinder 20 are adjusted such that, for example, each of the positions on the surface of the workpiece P comes into contact with the rotation unit 22 (namely, tip tool 222) and is ground the same number of times (for example, once) as the number of times of grinding at the other positions. For example, a case where the tip tool 222 of the rotation unit 22 comes into contact with and grinds each of the positions on the surface of the workpiece P only once is considered. In a case where the rotational speed of the rotary table 10 is 5400 rpm, the number of times of rotation is 5400 per one minute. Therefore, the time necessary for one rotation is 60/5400 [seconds], namely, 0.011 [seconds]. When it is assumed that, as illustrated in FIG. 4, the width in the z-axis direction of the contact surface with the rotation unit 22 is z1 [m], and the elevation slider 40 advances by z1 [m] in the z-axis direction every 0.01 [seconds], the speed of horizontal movement of the elevation slider 40 is z1/0.01 m/s, namely, z1100 m/s. In a case where the length z1 in the z-direction of the contact surface is 0.02 [m] and the rotational speed of the rotary table 10 is 5400 rpm, the speed of horizontal movement of the elevation slider 40 is 2.0 m/s. When the speed of horizontal movement of the elevation slider 40 is greater than 2.0 m/s, a portion that is not ground is generated on the surface of the workpiece P, whereas when the speed of horizontal movement of the elevation slider 40 is less than 2.0 m/s, the number of times of grinding is varied among the positions on the surface of the workpiece P.

[0040] As described above, the units F1 to F4 can control rotation of the rotary table 10 and the rotation unit 22, and can control the grinder 20 to linearly slide between the center side and the outer peripheral side of the workpiece P.

[0041] The grinder horizontal movement control unit F4 preferably changes a traveling direction of the grinder 20 based on the grinder angle . In a case where the angle of the grinder 20 is positive, the traveling direction of the grinder 20 is the negative direction (arrow direction illustrated in FIG. 4) or the positive direction (direction opposite to arrow direction illustrated in FIG. 4) of the two directions of the z-axis. In the former case, (1) the grinder horizontal movement control unit F4 horizontally moves the grinder 20 from the outer peripheral side of the workpiece P as the grinding processing start position (position illustrated in FIG. 3A) to the center side of the workpiece P as the grinding processing end position (position illustrated in FIG. 3B) along the negative direction of the z-axis, or (2) the grinder horizontal movement control unit F4 horizontally moves the grinder 20 from the center side of the workpiece P as the grinding processing start position to the outer peripheral side of the workpiece P as the grinding processing end position along the negative direction of the z-axis. In the cases (1) and (2), the moving direction of the grinder 20 is a direction opposite to a direction in which the grinder 20 is inclined, and the grinding processing can be progressed without catching grinding powder (powder generated by grinding). Thus, these cases are more suitable than cases (3) and (4) described below. When the grinding processing is progressed without catching the grinding powder, the grinding processing can be stably performed, which makes it possible to reduce variation in surface roughness of the workpiece P after the processing.

[0042] On the other hand, in the latter case, (3) the grinder horizontal movement control unit F4 horizontally moves the grinder 20 from the outer peripheral side of the workpiece P as the grinding processing start position to the center side of the workpiece P as the grinding processing end position along the positive direction of the z-axis, or (4) the grinder horizontal movement control unit F4 horizontally moves the grinder 20 from the center side of the workpiece P as the grinding processing start position (position illustrated in FIG. 3B) to the outer peripheral side of the workpiece P as the grinding processing end position (position illustrated in FIG. 3A) along the positive direction of the z-axis. In the cases (3) and (4), the tip tool 222 may be caught or hooked by the workpiece P. At that time, the tip tool 222 may unstably contact with the workpiece P, and the grinding processing may be nonuniformly performed. Further, in the case (4), unprocessed portion may be generated. On the other hand, in the case where the grinder 20 is horizontally moved along the negative direction of the z-axis (in cases (1) and (2) described above), contact resistance between the tip tool 222 and the workpiece P is low, and the processed surface is stable as compared with the case where the grinder 20 is horizontally moved along the positive direction (in cases (3) and (4) described above).

[0043] Further, the grinder horizontal movement control unit F4 preferably changes a moving speed of the grinder 20 as appropriate. The moving speed of the grinder 20 is desirably determined in relation to the rotational speed of the rotary table 10.

[0044] The rotation of the rotary table 10 is preferably started after the rotated rotation unit 22 of the grinder 20 comes into contact with the workpiece P. This is because, when the rotation unit 22 and the rotary table 10 come into contact with each other in a state where both are rotated, shaking of the rotary table 10 may occur. In a case where the rotary table 10 is rotated at the timing as described above, the grinder 20 is preferably held at a position where the rotary table 10 and the grinder 20 are in contact with each other until the rotational speed of the rotary table 10 becomes a certain rotational speed, and then, horizontal movement of the grinder 20 is preferably started. By controlling the horizontal movement start timing of the grinder 20, surface roughness on the entire surface of the workpiece P can be controlled to the equal degree.

[0045] The control apparatus 60 preferably includes a removing step of removing the grinding powder generated in the grinding step. As the removing step, for example, a method of blowing air or nitrogen like an air blower or an air knife, or dust collection can be used.

[0046] The control apparatus 60 may also include, for example, a step of evaluating the grinding state after the removing step. The step of evaluating the grinding state may be, for example, a method using a roughness meter that can measure three-dimensional surface roughness, a method of acquiring an image of the grinding state and evaluating the grinding state by machine learning, or a method of evaluating the grinding state based on a gloss level.

Examples

[0047] Grinding processing of a surface of a disk-shaped metal member as the workpiece P was performed by the grinding processing apparatus 1 according to the embodiment. Table 1 indicates processing conditions and results of Examples 1 to 8. The workpieces P according to Examples 1 to 3, 5, 7, and 8 correspond to disk-shaped members made of an aluminum alloy and having a diameter of 500 mm, subjected to grinding processing. The workpieces P according to Examples 4 and 6 correspond to disk-shaped members made of titanium and having a diameter of 500 mm, subjected to grinding processing. In each of Examples 1 to 8, the workpiece P was fixed to the rotary table 10 of the grinding processing apparatus 1, and surface grinding processing by the grinder 20 was performed. The rotational speed of the rotary table 10 and the speed of horizontal movement of the grinder 20 were adjusted such that each of the positions on the surface of the workpiece P came into contact with the tip tool 222 and was ground only once that is the same number of times as the number of times of grinding at the other positions.

[0048] As the tip tool 222 according to Examples 1 to 4 and 6 to 8, a cup brush-type wire brush including steel wires each having a diameter of 0.3 mm was used. On the other hand, as the tip tool 222 according to Example 5, a cup brush-type wire brush including steel wires each having a diameter of 0.1 mm was used. The diameter of each of the steel wires of the brush was desirably 0.01 mm or more and 2 mm or less, and further desirably 0.1 mm or more and 1.0 mm or less. As a type of the steel wire, a hard steel wire was used. In addition to the hard steel wire, the steel wire might include a plated steel wire (hard steel wire+(brass, zinc, and the like), plated steel twisted wire (hard steel wire+brass), wrapped wire (wire in which thin plated steel wire was wound around plated steel twisted wire), piano wire, stainless steel wire, brass wire, and phosphor bronze wire), and the like.

[0049] Further, in each of Examples 1 to 8, the angle of the rotation axis C2 of the rotation unit 22 of the grinder 20 to the vertical axis C3, namely, the grinder angle was set to an angle that exceeded 0 degrees and was 60 degrees or less. In each of Examples 1 to 8, the tip tool 222 was brought into contact with the workpiece P on the outer peripheral side of the workpiece P, the grinding processing was started, and the grinding processing of the surface by the grinder 20 was performed by horizontally moving the grinder 20 to the center side along the negative direction of the z-axis (in order from FIG. 3A to FIG. 3B). The rotational speed of the rotary table 10 was set to 5400 rpm within a range of 3000 rpm or more and 6000 rpm or less, and the speed of horizontal movement of the elevation slider 40, namely, the speed of horizontal movement of the grinder 20 was set to 2.0 m/s. In the state, the grinder 20 was linearly moved from the center side to the outer peripheral side of the workpiece P to grind the surface of the workpiece P.

[0050] In each of Examples 1 to 8, after the grinding processing, surface roughness Ra of the disk-shaped member as the workpiece P was measured, and variation in the surface roughness Ra was determined. The surface roughness Ra was a numerical value obtained by averaging difference of irregularities in a certain length that was referred to as arithmetic average roughness. A method of calculating variation in the surface roughness Ra was as follows.

[0051] Variation in the surface roughness Ra of the surface of the disk-shaped member as the workpiece P was determined by using n pieces (n is 2 or more) of surface roughness Ra. First, the surface roughness Ra was measured at n points on the disk-shaped workpiece P. Thereafter, variation in the surface roughness, namely, a standard deviation 6 was calculated from the n pieces of surface roughness Ra based on the following expression (1).

[00001]$\begin{array}{cc}\left[\mathrm{Expression}1\right]& \\ =\sqrt{\frac{1}{n}{.Math.}_{i=1}^n{\left({\mathrm{Ra}}_i-\stackrel{\_}{\mathrm{Ra}}\right)}^2}& \left(1\right)\end{array}$

For example, as illustrated in FIG. 5, the surface roughness Ra was measured at a sample point P1 at a center of the workpiece P and at each of other sample points P4, P8, P12, and P16 on a straight line forming a diameter of the workpiece P. Thereafter, variation in the surface roughness, namely, the standard deviation was calculated from five pieces (n=5) of surface roughness Ra based on the above-described expression (1). FIG. 5 is a top view illustrating the workpiece P. The sample points P8 and P4 were at positions close to the outer periphery of the workpiece P. Further, the sample points P8, P16, P1, P12, and P4 were arranged in this order at substantially equal intervals.

[0052] Selection of the sample points was not limited to the five points P8, P16, P1, P12, and P4 illustrated in FIG. 5. The surface shape of the workpiece P was sequentially formed from the center side to the outer peripheral side (or from outer peripheral side to center side) while the contact surface with the rotation unit 22 of the grinder 20 was slid in the positive direction of the z-axis. Therefore, the sample points were suitably set within a wide range from the center side to the outer peripheral side of the workpiece P.

Comparative Examples

[0053] Table 1 indicates processing conditions and results of Comparative Examples 1 to 4. In Comparative Example 1, grinding processing of the surface of the disk-shaped member made of an aluminum alloy was performed under the same processing condition as Example 1 except that the grinder angle was set to zero degrees. In Comparative Example 2, grinding processing of the surface of the disk-shaped member made of an aluminum alloy was performed under the same processing condition as Example 1 except that the grinder angle was set to 65 degrees. In Comparative Examples 3 and 4, grinding processing of the disk-shaped members respectively made of an aluminum alloy and titanium was manually performed.

TABLE-US-00001 TABLE 1 Processing Condition Rotational Speed of Material Material Processing Grinder of Wire, of Grinder Method [rpm] etc Workpiece Angle Example 1 Machine 5000 Steel Wire Aluminum 10 Prosess 0. 3[mm] Alloy Example 2 Machine 5000 Steel Wire Aluminum 0.5 Prosess 0.3[mm] Alloy Example 3 Machine 5000 Steel Wire Aluminum 45 Prosess 0.3[mm] Alloy Example 4 Machine 5000 Steel Wire Titanium 10 Prosess 0.3[mm] Example 5 Machine 5000 Steel Wire Aluminum 10 Prosess 0.1[mm] Alloy Example 6 Machine 11000 Steel Wire Titanium 10 Prosess 0.3[mm] Example 7 Machine 11000 Steel Wire Aluminum 10 Prosess 0.3[mm] Alloy Example 8 Machine 5000 Steel Wire Aluminum 10 Prosess 0.3 mm] Alloy Comparative Machine 5000 Steel Wire Aluminum 0 Example 1 Prosess 0.3[mm] Alloy Comparative Machine 5000 Steel Wire Aluminum 65 Example 2 Prosess 0.3[mm] Alloy Comparative Manual 12000 Steel Wire Aluminum 0 Example 3 Process 0.3[mm] Alloy Comparative Manual 12000 Steel Wire Titanium 0 Example 4 Process 0.3[mm] Result Average Value of Surface Variation in Surface Roughness Ra [m] Roughness Ra Example 1 3.693 0.141 Example 2 3.348 0.348 Example 3 3.610 0.456 Example 4 2.946 0.167 Example 5 4.516 0.263 Example 6 3.557 0.138 Example 7 2.948 0.381 Example 8 1.582 0.130 Comparative 3.357 1.316 Example 1 Comparative Grinding Impossible (some Example 2 parts cannot be ground) Comparative 1.754 0.825 Example 3 Comparative 3.405 1.125 Example 4

[0054] Under the processing condition of Comparative Example 2, in particular, in a case where the grinder angle was 65 degrees, the angle was excessively large, and grinding was impossible (some parts cannot be ground). Further, with reference to Comparative Examples 1, 3, and 4, the average value of the surface roughness Ra was not different from any of Examples 1 to 8. However, variation in the surface roughness Ra exceeded 0.8 and was excessively large. When variation in the surface roughness Ra increases, a product may be determined as defective in a subsequent step. On the other hand, under the processing conditions of Examples 1 to 8, variation in the surface roughness Ra can be suppressed. In other words, under the processing conditions of Examples 1 to 8, variation in the surface roughness Ra of a surface having predetermined roughness can be reduced.

[0055] According to at least one embodiment described above, it is possible to provide the grinding processing apparatus that reduces variation in surface roughness of the disk-shaped workpiece P, in particular, the large disk-shaped workpiece P.

[0056] While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.