Machining method using attachment main shaft

Abstract

A machining method in which machining is performed via a tool mounted to an attachment main shaft, wherein: in a state in which an attachment main shaft (10) is mounted to a main shaft (14), the position of a rotational axis (Oa) of the attachment main shaft in a first direction orthogonal to a rotational axis (Os) of the attachment main shaft is found with the main shaft at a plurality of rotationally indexed positions; a deviation quantity in the first direction, and a deviation quantity in a second direction which is orthogonal to the rotational axis of the attachment main shaft and to the first direction, of the position of the rotational axis of the attachment main shaft relative to the rotational axis of the main shaft are calculated from the positions of the rotational axis found at each of the plurality of rotationally indexed positions; and on the basis thereof, a workpiece is machined with a tool (34) of the attachment main shaft while performing correction to compensate for the deviation quantity in the first direction and the deviation quantity in the second direction.

Description

Machining method using attachment spindle

[0001] The present invention relates to a machining method using an attachment spindle that is attached to the spindle of a machine tool.

[0002] Patent Document 1 describes a correction method in which a touch probe equipped with a spherical touch sensor is placed on a table, a reference tool is attached to the spindle, and the reference tool is moved in the X-, Y-, and Z-axis directions to determine the coordinates where the reference tool abuts against the touch probe, and based on this, a correction value for the attachment spindle is determined.

[0003] JP 2010-260119 A

[0004] In the compensation method of Patent Document 1, a reference tool is brought into contact with a touch probe, and therefore the obtained compensation value contains an error due to the unavoidable lost motion of the touch probe. Furthermore, since the touch probe contains an error that depends on the direction in which the measurement object contacts it, there is a problem that the compensation value obtained by the compensation method of Patent Document 1 also changes depending on the direction in which the reference tool approaches the touch probe. Furthermore, since the compensation method of Patent Document 1 physically contacts the reference tool with the touch probe, it is not possible to perform measurements with a rotating tool.

[0005] The technical problem of the present invention is to solve these problems of the conventional technology, and it is an object of the present invention to provide a machining method that can easily and quickly measure the positional deviation of the attachment spindle relative to the spindle to which it is attached, easily correct machining errors when using the attachment spindle, and machine workpieces with high precision.

[0006] In order to achieve the above object, according to the present invention, a machining method is provided in which an attachment spindle incorporating a rotary actuator is mounted on a machine tool equipped with a spindle instead of a tool holder, and the tool mounted on the attachment spindle is rotated by the rotary actuator while the spindle is stopped from rotating, the method comprising the steps of: mounting the tool holder having a first tool mounted on the spindle; rotating the tool holder with the spindle to machine a workpiece placed on a table; mounting the attachment spindle having a second tool mounted on the spindle instead of the tool holder; indexing the spindle to a plurality of rotation index positions with the attachment spindle mounted; and indexing the attachment spindle at each of the plurality of rotation index positions using a sensor mounted on the table. a step of calculating, from the positions in the first direction of the rotation axis of the attachment spindle determined at each of the plurality of rotation index positions, a deviation amount in the first direction of the position of the rotation axis of the attachment spindle relative to the rotation axis of the spindle at the rotation index position where the spindle stops rotating when machining is performed with the attachment spindle, and a deviation amount in a second direction that is a direction perpendicular to the rotation axis of the attachment spindle and the first direction; and a step of machining the workpiece placed on a table with a second tool rotated by a rotary actuator while correcting to compensate for the deviation amount in the first direction and the deviation amount in the second direction.

[0007] According to the present invention, by using sensors on the machine tool to determine the positional deviation between the rotation axis of the attachment spindle attached to the spindle of the machine tool and the rotation axis of the spindle of the machine tool, in a first direction and in a second direction that are orthogonal to each other, it becomes possible to easily and quickly determine the amount of correction for machining errors, and to machine the workpiece with high precision.

[0008] 10 is a schematic side view showing an example of a machine tool to which the present invention can be applied. FIG. 11 is a schematic side view of a machine tool similar to FIG. 1 with an attachment spindle mounted on a spindle. FIG. 12 is a sectional view showing an example of an attachment spindle. FIG. 13 is a block diagram of an attachment spindle error measuring system according to an embodiment of the present invention. FIG. 14 is a flowchart of an attachment spindle error measuring method. FIG. 15 is a perspective view of a tool measuring device. FIG. 16 is an explanatory diagram of the operation of attachment spindle error measurement. FIG. 17 is an explanatory diagram of the positional deviation of the rotation axis of the attachment spindle with respect to the rotation axis of a spindle to which the attachment spindle is mounted. FIG. 18 is an explanatory diagram of the operation of another example of an attachment spindle error measuring method. FIG. 19 is an explanatory diagram of the operation of the attachment spindle error measuring method according to the example of FIG. 9. FIG. 19 is an explanatory diagram for explaining the positional deviation of the rotation axis of the attachment spindle in the attachment spindle error measuring methods of FIGS. 9 and 10.

[0009] Fig. 1 is a schematic side view showing an example of a machine tool to which the present invention can be applied. In Fig. 1, machine tool 100 is a vertical machining center. In this embodiment, machine tool 100 is a three-axis processing machine having three orthogonal feed axes (X-axis, Y-axis, and Z-axis).

[0010] Machine tool 100 includes a bed 102 as a base fixed to the floor of a factory or the like. A column 104 is erected on the rear end side of the upper surface of bed 102. An X-slider 106 is attached to the front of column 104 so as to be able to reciprocate in the X-axis direction, which is the horizontal left-right direction (the direction perpendicular to the plane of the paper in FIG. 1 ). X-slider 106 has a block 106a that slides along an X-axis guide rail 108 that extends in the X-axis direction.

[0011] The column 104 is provided with a ball screw (not shown) extending in the X-axis direction and an X-axis servo motor Mx connected to one end of the ball screw as an X-axis feed device that reciprocates the X-slider 106, and a nut (not shown) that engages with the ball screw is attached to the X-slider 106. The column 104 is also provided with an X-axis digital scale (not shown) as an X-coordinate detection device that detects the position of the X-axis feed device. The X-coordinate detection device may also include a rotary encoder (not shown) that detects the rotational position of the X-axis servo motor Mx.

[0012] A spindle head 110 is attached to the front surface of the X-slider 106 so as to be able to reciprocate in the vertical Z-axis direction. The spindle head 110 has a block 110a that slides along a Z-axis guide rail 112 extending in the Z-axis direction. The X-slider 106 is provided with a ball screw (not shown) extending in the Z-axis direction and a Z-axis servo motor Mz connected to one end of the ball screw as a Z-axis feed device that drives the spindle head 110 back and forth. A nut (not shown) that engages with the ball screw is attached to the column 104. The X-slider 106 is also provided with a Z-axis digital scale (not shown) as a Z-coordinate detector that detects the position of the Z-axis feed device. The Z-coordinate detector may also include a rotary encoder (not shown) that detects the rotational position of the Z-axis servo motor Mz.

[0013] A spindle 114 serving as a first spindle is supported by bearings 116 in the spindle head 110 so as to be rotatable about a rotation axis Os serving as a first rotation axis extending in the vertical direction. The spindle head 110 includes a spindle servo motor Ms for driving the rotation of the spindle 114, and a rotary encoder 118 attached to the spindle 114 as a rotation position detection device for detecting the rotational position of the spindle 114 around the rotation axis Os.

[0014] A table 120 is disposed at the front end side (left side in FIG. 1 ) of bed 102 so as to be able to reciprocate in the Y-axis direction, which is the horizontal front-rear direction perpendicular to the X-axis. Table 120 has a block 120a that slides along Y-axis guide rails 122 that extend in the Y-axis direction. A workpiece W to be machined by machine tool 100 is fixed to the upper surface of table 120 facing spindle 114 using a pallet (not shown) or jig (not shown).

[0015] As a Y-axis feed device that drives the table 120 back and forth, the bed 102 is provided with a ball screw 124 extending in the Y-axis direction and a Y-axis servo motor My connected to one end of the ball screw 124, and a nut 126 that engages with the ball screw 124 is attached to the table 120. In addition, a Y-axis digital scale 128 is provided on the bed 102 as a Y-coordinate detection device that detects the position of the Y-axis feed device. The Y-coordinate detection device may be equipped with a rotary encoder (not shown) that detects the rotational position of the Y-axis servo motor My.

[0016] A rotary cutting tool T (hereinafter simply referred to as tool T) such as an end mill or a drill can be attached to the tip of spindle 114 as a first tool. In FIG. 1 , a tapered hole (not shown) conforming to a predetermined standard such as HSK standard (DIN 69893) or ISO 7388 is formed in the tip of spindle 114, and tool T is attached to the tip of spindle 114 via a tool holder 130 conforming to that standard. Machine tool 100 can be equipped with a tool magazine (not shown) that stores a plurality of tools T, and an automatic tool changer (not shown) that exchanges tools T between the tool magazine and spindle 114.

[0017] Machine tool 100 may be equipped with a cleaning air supply device for cleaning the inner surface of the tapered bore of spindle 114 or for blowing air from a tool attached to spindle 114 to remove chips. The cleaning air supply device may include an air supply line (not shown) or an air supply passage (not shown) provided in spindle 114 along the rotation axis Os, and a compressed air supply device (not shown) for supplying compressed air to the air supply line or air supply passage. The compressed air supply device may include a compressor (not shown) that compresses air, an accumulator (not shown) that stores compressed air, a pressure adjustment valve (not shown) disposed at the outlet of the accumulator, and the like. The compressed air supply device may include an ON / OFF valve (not shown) that connects / disconnects the accumulator to the air supply line or air supply passage of spindle 114. The ON / OFF valve may be, for example, a solenoid valve. The compressed air supply device not only cleans the inner surface of the tapered hole of the spindle 114 and blows air from the tool to remove chips, but also serves as an attachment spindle drive source 64 (see FIG. 4) for supplying compressed air as a power source to the attachment spindle 10, which will be described later.

[0018] The machine tool 100 is equipped with a control device 200. The control device 200 can be composed of a computer and associated software, including a CPU (central processing unit), memory devices such as RAM (random access memory) and ROM (read only memory), storage devices such as HDD (hard disk drive) and SSD (solid state drive), input / output ports, and a bidirectional bus interconnecting these, and can include an NC device that controls the servo motors Mx, My, Mz of the X-axis, Y-axis, and Z-axis and the servo motor Ms of the spindle 114, as well as a machine control device that controls peripheral devices (not shown) of the machine tool 100. The peripheral devices of the machine tool can include a tool magazine (not shown), an automatic tool changer (not shown), a compressed air supply device, a machining fluid supply device (not shown), etc.

[0019] In this embodiment, machine tool 100 is capable of controlling the rotational angular position of spindle 114 about rotation axis Os (Cs-axis control). Specifically, in this embodiment, spindle 114 can be controlled in both a speed control mode and a position control mode (sometimes referred to as Cs-axis control mode). In other words, machine tool 100 to which the present invention is applied can perform Cs-axis control in addition to axial feed control of the X-axis, Y-axis, and Z-axis.

[0020] In the speed control mode, the spindle 114 is controlled based on the speed (number of rotations), and in this case, the rotational angle position of the spindle 114 about the rotation axis Os is not controlled. In contrast, in the Cs-axis control mode, the spindle 114 is controlled based on the rotational angle amount from an origin position about the rotation axis Os, along with the rotational speed, and therefore the rotational angle position of the spindle 114 about the rotation axis Os is controllable. The origin of the rotation angle can be set to a predetermined position determined, for example, relative to a certain position of the spindle head 110. Furthermore, the origin can also be changed to any position deviated from this predetermined position.

[0021] As shown in FIG. 2 , an attachment spindle 10 can be attached to the tip of the spindle 114 instead of a tool T. Referring to FIG. 3 , an example of the attachment spindle 10 has a housing 12. The housing 12 has a tapered shank portion 12a formed on the base end side to fit into a tapered hole in the spindle 114. In this embodiment, the housing 12 has a two-face contact type tool holder shape conforming to the HSK standard (DIN 69893). The housing 12 may also have a 7 / 24 taper tool holder shape as specified by ISO 7388. The housing 12 also has a V-groove 12b that engages with an exchange arm (not shown) of an automatic tool changer of the machine tool 100. Furthermore, in order to receive compressed air from the air passage of the spindle 114 to the attachment spindle, the tool holder is provided with a compressed air supply path that can be separated from the spindle 114, such as a coolant pipe in the case of an HSK standard tool holder, or a pull stud bolt with a center hole in the case of a 7 / 24 taper tool holder.

[0022] Within the housing 12, a main shaft 14 serving as a second main shaft is rotatably supported by bearings 16 around a rotation axis Oa serving as a second rotation axis. The rotation axis Oa of the attachment main shaft 10 coincides with the rotation axis Os of the main shaft 114 when the attachment main shaft 10 is attached to the tip of the main shaft 114.

[0023] The attachment spindle 10 further includes a spindle drive device that rotationally drives the spindle 14. In this embodiment, the spindle drive device includes an air turbine 20 as a rotary actuator disposed within the air chamber 18 of the housing 12. The air turbine 20 is coupled to the spindle 14 so as to rotate about the rotation axis Oa. The housing 12 has an air supply passage 22 that supplies air to the air chamber 18, and an exhaust passage 24 that exhausts air from the air chamber 18 to the outside. When the attachment spindle 10 is attached to a spindle 114 of the machine tool 100, the air supply passage 22 communicates with the air passage of the spindle 114.

[0024] The housing 12 also has a positioning protrusion 26. The positioning protrusion 26 includes a recess 26a extending parallel to the rotation axis Oa, a ball 28 accommodated in the recess 26a so as to be movable in the direction of the rotation axis Oa, and a coil spring 30 disposed in the recess 26a as a biasing member. After the ball 28 is accommodated in the recess 26a, a cap 32 is attached to the opening of the recess 26a. As shown in FIG. 3 , the cap 32 has a shape that allows a portion of the ball 28 to protrude outward but prevents it from detaching from the cap 32 beyond the opening of the cap 32. In this way, the ball 28 is biased against the cap 32 by the coil spring 30 so that a portion of the ball 28 protrudes outward from the opening of the cap 32. When the attachment spindle 10 is attached to the spindle 114 of the machine tool 100, the ball 28 engages with a positioning engagement portion 132 of the spindle head 110. As a result, the attachment spindle 10 is positioned at the origin position around the rotation axis Oa in the Cs axis control mode.

[0025] The housing 12 further has an opening in the center of the end opposite the tapered shank portion 12a, through which the spindle 14 protrudes. A tool mounting hole 14a is formed in the front end of the spindle 14, and a tool 34 serving as a second tool is mounted in this tool mounting hole 14a. In this embodiment, the tool 34 is fixed in the tool mounting hole 14a by a collet chuck 36. In this embodiment, the collet chuck 36 is forced into the tool mounting hole 14a and grips the tool 34 by threading and tightening a nut 38 onto a threaded portion formed on the outer peripheral surface of the front end of the spindle 14.

[0026] The attachment spindle error measuring system and measurement method of the present invention will be described below, taking as an example a case where the present invention is applied to a machine tool 100. Fig. 4 is a block diagram showing a preferred embodiment of the attachment spindle error measuring system of the present invention. In Fig. 4, an attachment spindle error measuring system 50 comprises, as main components, a control device 52, an input unit 54, a servo amplifier 56, a servo motor 58, a position detection device 60, a memory device 62, and a tool measuring device 70 as a sensor.

[0027] The control device 52 controls the current output from the servo amplifier to the servo motor 58 in accordance with a tool measurement program input from the input unit 54, and causes relative movement between the attachment spindle 10 attached to the spindle 114 and the tool measuring device 70. In the embodiment shown in Figures 1 and 2, the control device 52 can be configured as a control device 200. In other words, it can be configured as part of the NC device or machine control device of the machine tool to which the present invention is applied.

[0028] The input unit 54 is an element that inputs a tool measurement program to the control device 52, and may include input devices such as a keyboard (not shown) or a touch panel (not shown) connected to an input / output port of the control device 52 (control device 200 in the embodiment of FIGS. 1 and 2), a server (not shown), a personal computer (not shown), or a CAM (Computer Aided Manufacturing) device connected to the control device 52 via a communication network.

[0029] Servo motor 58 is an element that drives the feed axis of the machine tool to which attachment spindle 10 is attached, and in the embodiment of FIGS. 1 and 2, can be composed of X-axis servo motor Mx, Y-axis servo motor My, Z-axis servo motor Mz, and spindle servo motor Ms of machine tool 100.

[0030] The position detection device 60 is an element that outputs the coordinates of the feed axis of the machine tool to which the attachment spindle 10 is attached to the control device 52, and in the embodiment of Figures 1 and 2, can be configured by an X-axis digital scale, a Y-axis digital scale 128, a Z-axis digital scale, and a rotary encoder 118. The position detection device 60 may also be configured by rotary encoders (not shown) provided on the X-axis servo motor Mx, the Y-axis servo motor My, and the Z-axis servo motor Mz, instead of the X-axis digital scale, the Y-axis digital scale 128, and the Z-axis digital scale.

[0031] The memory device 62 is an element that stores the measured attachment spindle error, and in the embodiment of Figures 1 and 2, can be configured by a memory device such as a RAM (random access memory) or ROM (read only memory) provided in the control device 200 and / or a storage device such as an HDD (hard disk drive) or SSD (solid state drive).

[0032] The tool measuring device 70 may be a non-contact tool measuring device that outputs a skip signal when it detects a tool to be measured. Referring to FIG. 6 , the tool measuring device 70 shown as an example is a laser-type measuring device that includes a laser emitting unit that emits a thin, linear laser beam and a laser receiving unit that receives the laser beam. The device outputs a skip signal when a measurement target crosses the laser beam between the laser emitting unit and the laser receiving unit. To move the tool closer to the laser beam, a command to move the tool along one of the X, Y, and Z axes is issued. However, if a skip signal is output before the tool reaches the commanded target position, the axis movement stops, and the program moves to the next block without reaching the commanded target position. A skip signal is a signal that triggers the tool to stop movement and skip a command even though the movement command has not been completed.

[0033] More specifically, tool measuring device 70 has a frame that positions the laser irradiation unit and laser receiving unit at predetermined positions. The frame has a base unit 72 that is fixed to an appropriate portion of the machine tool to which attachment spindle 10 is attached. The predetermined portion of the machine tool to which base unit 72 is attached can be a support member, such as table 120 of machine tool 100, that is movable relatively to the spindle in a horizontal direction about the rotation axis of the spindle to which attachment spindle 10 is attached, for example, the rotation axis Os of spindle 114 of machine tool 100.

[0034] The frame of the tool measuring device 70 has a pair of arms 74a, 74b that are parallel to the rotation axis of the spindle when the base 72 is fixed to a support member of the machine tool. A laser emitting unit 76a that emits laser light L and a laser receiving unit 76b (see FIG. 7) that receives the laser light L are disposed at the tips of the pair of arms 74a, 74b so as to face each other. Thus, the laser measuring device that constitutes the tool measuring device 70 has a generally U-shaped frame made up of the base 72 and the pair of arms 74a, 74b, and is configured to emit laser light L between the arms 74a, 74b. The laser measuring device further includes a skip signal generating circuit (not shown) that outputs a skip signal when the laser light L irradiated from the laser emitting unit 76a toward the laser receiving unit 76b is interrupted.

[0035] The tool measuring device 70 is fixed to the table 120 so as to irradiate the laser beam L in a direction perpendicular to the rotation axis Os of the spindle 114 of the machine tool 100. The tool measuring device 70 is preferably fixed to the table 120 so as to irradiate the laser beam Lx or Ly parallel to the X-axis or Y-axis. Hereinafter, the attachment spindle error measuring method will be described assuming that the tool measuring device 70 is disposed on the table 120 so as to irradiate the laser beam Ly in the Y-axis direction, as shown in FIG. 2 , but the tool measuring device 70 may also be disposed so as to irradiate the laser beam Ly in the X-axis direction (the direction perpendicular to the paper surface).

[0036] When machining the workpiece W, a very thin tool is attached to the spindle 14 of the attachment spindle 10 as a second tool, and therefore the attachment spindle 10 is usually used after the workpiece W has been machined by tool T, which is a rotary cutting tool such as an end mill or drill that is attached to the tip of the spindle 114 of the machine tool 100 as a first step.

[0037] It has been explained that the attachment spindle 10 is mounted on the spindle 114 of the machine tool 100 so that its rotation axis Oa coincides with the rotation axis Os of the spindle 114. However, in reality, the rotation axis Oa of the attachment spindle 10 mounted on the spindle 114 does not completely coincide with the rotation axis Os of the machine tool 100. In the present invention, before machining by the attachment spindle 10 begins, the amount of deviation of the rotation axis Oa of the attachment spindle 10 from the rotation axis Os of the machine tool 100 is measured by the attachment spindle error measuring method described below.

[0038] 5, after machining a workpiece W with tool T as a first tool, the attachment spindle 10 is attached to the tip of the spindle 114 in order to machine the workpiece W with the attachment spindle 10 (step S10). This may be performed manually by an operator, but is typically performed by an automatic tool changer of the machine tool 100 in accordance with a machining program input into the control device 52. During automatic tool change, the spindle 114 of the machine tool 100 is indexed to the origin position by Cs-axis control. Furthermore, when the attachment spindle 10 is attached to the spindle 114, the ball 28 of the attachment spindle 10 engages with the positioning engagement portion 132 of the spindle head 110 of the machine tool 100, and the attachment spindle 10 is positioned at the origin position P0 (see FIG. 8) in the Cs-axis control mode.

[0039] 8, the position Pr0 of the rotation axis Oa of the spindle 14 of the attachment spindle 10 when the Cs axis is at the origin position P0 is shown. The positional deviation (deviation) of the rotation axis Oa of the spindle 14 of the attachment spindle 10 from the rotation axis Os of the spindle 114 of the machine tool 100 is expressed by the following equation: δx=X ｃａ（０） -Xs=rcosφ…(1) δy=Y ｃａ（０） -Ys=rsinφ…(2)

[0040] After the attachment spindle 10 is mounted on the spindle 114 of the machine tool 100, the attachment spindle error measuring method is executed in step S12 and thereafter. This can be done automatically, for example, by writing a command to read the attachment spindle error measuring program into the machining program input to the control device 52. The attachment spindle error measuring program may be executed independently of the execution of the machining program.

[0041] First, the spindle 14 of the attachment spindle 10 is rotated at a predetermined rotational speed, for example, the rotational speed used during machining (step S12). Preferably, this is continued for a predetermined time to warm up the attachment spindle 10 (step S14). This warm-up operation stabilizes the rotation of the attachment spindle 10.

[0042] Next, by Cs-axis control, the spindle 114 of the machine tool 100 is moved to a first measurement position Pr1, which is a predetermined rotational position about the rotation axis Os (step S16). In the example of FIG. 8 , this is a rotational position at an angle θ1 from the origin position Pr0 around the rotation axis Os. Rotation of the spindle 114 to the first measurement position Pr1 can be performed in the Cs-axis control mode. At this time, the ball 28 of the attachment spindle 10 disengages from the positioning engagement portion 132 of the spindle head 110.

[0043] Next, with the spindle 114 fixed at the first measurement position Pr1, the spindle 114 of the machine tool 100 is moved relative to the table 120 so that the tool 34 of the attachment spindle 10 crosses the laser beam L from the positive and negative sides. A movement direction coordinate value of the rotation axis Os is calculated based on the coordinate when the tool 34 of the attachment spindle 10 blocks the laser beam L (step S18). For example, as shown in FIG. 7 , if the tool measuring device 70 is fixed to the table 120 so that the laser beam L is irradiated in the Y-axis direction, this can be performed by moving the spindle 114 in the X-axis direction, as described below.

[0044] In this embodiment, the X-axis direction is a first direction perpendicular to the rotation axis Oa of the attachment main shaft 10, and the Y-axis direction is a second direction perpendicular to the rotation axis Oa of the attachment main shaft 10 and the first direction.

[0045] (1) By controlling the X-axis, Y-axis, and Z-axis, the tool 34 of the attachment spindle 10 is positioned at a predetermined first measurement start position P1, which is a predetermined distance away from the laser beam L in the -X-axis direction. (2) By controlling the X-axis, as shown by arrow A1, the spindle 114 is moved in the + direction along the X-axis from the first measurement start position P1, and the tool 34 of the attachment spindle 10 is made to approach the laser beam L. At this time, the tool 34 may be stationary, but it is preferable to make it approach the laser beam L while rotating. (3) When the tool 34 of the attachment spindle 10 blocks the laser beam L, a skip signal is output from the skip signal circuit of the tool measuring device 70 to the control device 52. The control device 52 calculates the X-coordinate value X － （１） is read from the position sensing device 60.

[0046] (4) Next, the X-axis, Y-axis, and Z-axis are controlled to position the tool 34 of the attachment spindle 10 at a predetermined second measurement start position P2 that is a predetermined distance away from the laser beam L in the +X-axis direction. (5) The X-axis is controlled to move the spindle 114 from the second measurement start position P2 in the -X-axis direction as shown by arrow A2, and the tool 34 of the attachment spindle 10 approaches the laser beam L. At this time, the tool 34 may be stationary, but it is preferable to rotate the tool 34 while it approaches the laser beam L. (6) When the tool 34 of the attachment spindle 10 blocks the laser beam L, a skip signal is output from the skip signal circuit of the tool measuring device 70 to the control device 52. The control device 52 calculates the X-coordinate value X ＋ （１） is read from the position sensing device 60.

[0047] The X-coordinate value X is set as the coordinate value in the movement direction of the rotation axis Oa of the attachment spindle 10 at the first measurement position Pr1 (in this case, the coordinate value of the rotation axis Oa measured by moving the spindle 114 in the X-axis direction).ｃａ（１） can be expressed by the following formula (3): ｃａ（１） = (X － （１） +X ＋ （１） ) / 2=Xs+rcos(φ+θ1)...(3)

[0048] Next, in the Cs-axis control mode, spindle 114 of machine tool 100 is moved to second measurement position Pr2, which is a predetermined rotational position about rotation axis Os (step S20). In the example of Fig. 8, second measurement position Pr2 is a rotational position at an angle θ2 from origin position Pr0 around rotation axis Os.

[0049] After the spindle 114 is moved to the second measurement position Pr2, the spindle 114 is fixed at the second measurement position Pr2, and the same steps as those (1) to (6) are carried out to obtain the X － （２） and X ＋ （２） is calculated, and based on this, the X coordinate value X of the rotation axis Oa of the attachment spindle 10 at the second measurement position is calculated. ｃａ（２） is calculated using the following equation (4) (step S22). ｃａ（２） = (X － （２） +X ＋ （２） ) / 2=Xs+rcos(φ+θ2)...(4)

[0050] Furthermore, in the Cs-axis control mode, spindle 114 of machine tool 100 is moved to third measurement position Pr3, which is a predetermined rotational position about rotation axis Os (step S24). In the example of Fig. 8, third measurement position Pr3 is a rotational position at an angle θ3 from origin position Pr0 around rotation axis Os.

[0051] After the spindle 114 is moved to the third measurement position Pr3, the spindle 114 is fixed at the third measurement position Pr3, and the same steps as those of steps (1) to (6) are carried out to obtain X － （３） and X ＋ （３） is calculated, and based on this, the X coordinate value X of the rotation axis Oa of the attachment spindle 10 at the third measurement position Pr3 is calculated. ｃａ（３）is calculated using the following equation (5) (step S26). ｃａ（３） = (X － （３） +X ＋ （３） ) / 2=Xs+rcos(φ+θ3)...(5)

[0052] Furthermore, in the Cs-axis control mode, spindle 114 of machine tool 100 is moved to fourth measurement position PR4, which is a predetermined rotational position about rotation axis Os (step S28). In the example of Fig. 8, fourth measurement position Pr4 is a rotational position at an angle θ4 from origin position Pr0 around rotation axis Os.

[0053] After the spindle 114 is moved to the fourth measurement position Pr4, the spindle 114 is fixed at the fourth measurement position Pr4, and the same steps as those of steps (1) to (6) are carried out to obtain X － （４） and X+(4), and based on this, the X coordinate value X of the rotation axis Oa of the attachment spindle 10 at the fourth measurement position Pr4 is calculated. ｃａ（４） is calculated using equation (6) (step S30). ｃａ（４） = (X － （４） +X ＋ （４） ) / 2=Xs+rcos(φ+θ4)...(6)

[0054] The obtained X ｃａ（１） , X ｃａ（２） , X ｃａ（３） , X ｃａ（４） Based on the equations (1) to (6), the positional deviation in the X-axis direction (amount of deviation in the first direction) δx and the positional deviation in the Y-axis direction (amount of deviation in the second direction) δy of the rotational axis Oa of the attachment spindle 10 from the rotational axis Os of the spindle 114 of the machine tool 100 are expressed by the following equations (7) and (8).

[0055]

[0056] The control device 200 of the machine tool 100 calculates the amount of correction for the machining error based on the positional deviations δx and δy in the X-axis and Y-axis directions (step S32). The control device 200 then rotates the spindle 114 of the machine tool 100 to the origin position P0 in the Cs-axis control mode and fixes it at this position (step S34). At this time, the ball 28 of the attachment spindle 10 engages with the positioning engagement portion 132 of the spindle head 110 of the machine tool 100. The workpiece W is machined with the tool 34, which serves as a second tool and is rotated by the attachment spindle 10 (step S36).

[0057] According to this embodiment, the amount of deviation in the X-axis direction (first direction) and the amount of deviation in the Y-axis direction (second direction) between the rotation axis Oa of the spindle 14 of the attachment spindle 10 attached to the spindle 114 of the machine tool 100 and the rotation axis Os of the spindle 114 of the machine tool 100 are determined using the tool measuring device 70 as a sensor mounted on the table 120 of the machine tool 100, thereby making it possible to easily and quickly determine the amount of correction for the machining error.

[0058] In the above-described method, the spindle 114 is moved in the positive direction along the X axis from the first measurement start position P1, and then moved in the negative direction along the X axis from the second measurement start position P2. However, the present invention is not limited to this approach, and the spindle 114 may first be moved in the negative direction along the X axis from the second measurement start position P2, and then moved in the positive direction along the X axis from the first measurement start position P1.

[0059] As described above, the spindle 114 of the machine tool 100 is positioned at a plurality of rotation index positions, four measurement positions Pr1, Pr2, Pr3, and Pr4 in the Cs-axis control mode using one laser beam L irradiated in the Y-axis direction, and the position X of the rotation axis Oa of the attachment spindle 10 is measured in the X-axis direction as a first direction perpendicular to the rotation axis Oa of the attachment spindle 10. ｃａ（１） , X ｃａ（２） , X ｃａ（３） , X ｃａ（４）and based on this, calculate the positional deviation in the X-axis direction (amount of deviation in the first direction) δx and the positional deviation in the Y-axis direction (amount of deviation in the second direction) δy of the rotational axis Oa of the attachment spindle 10 from the rotational axis Os of the spindle 114 of the machine tool 100.

[0060] The present invention is not limited to this, and as shown in Figures 9 to 11, in addition to the laser light Ly irradiated in the Y-axis direction, laser light may also be irradiated in the X-axis direction, and the spindle 114 of the machine tool 100 may be positioned at two measurement positions in the Cs-axis control mode to determine the positional deviation in the first direction (X-axis direction) and the positional deviation in the second direction (Y-axis direction), and based on this, the misalignment of the rotation axis Oa of the attachment spindle 10 in the first and second directions may be calculated.

[0061] 11, similarly to step S10 described above, when the attachment spindle 10 is attached to the tip of the spindle 114 of the machine tool 100, the positional deviation (deviation) of the rotation axis Oa of the spindle 14 of the attachment spindle 10 from the rotation axis Os of the spindle 114 of the machine tool 100 is expressed by the following equation: δx=X ｃａ（０） -Xs=rcosφ…(9) δy=Y ｃａ（０） -Ys=rsinφ…(10)

[0062] (7) Next, after warming up in the same manner as in steps S12 and S14 described above, spindle 114 of machine tool 100 is moved by Cs-axis control to first measurement position Pr1, which is a predetermined rotational position about rotation axis Os, and fixed at first measurement position Pr1. In the example of Fig. 11, this is the rotational position at an angle θ1 from origin position Pr0 around rotation axis Os.

[0063] (8) Next, as shown in Fig. 9, the X-axis, Y-axis, and Z-axis are controlled to position the tool 34 of the attachment spindle 10 at a predetermined first measurement start position P1, which is a predetermined distance in the -X-axis direction from the laser beam Ly irradiated in the Y-axis direction. (9) The X-axis is controlled to move the spindle 114 in the + direction along the X-axis from the first measurement start position P1, as shown by arrow A1, to move the tool 34 of the attachment spindle 10 toward the laser beam Ly. At this time, the tool 34 may be stationary, but it is preferable to rotate the tool 34 while it approaches the laser beam Ly. (10) When the tool 34 of the attachment spindle 10 blocks the laser beam Ly, a skip signal is output from the skip signal circuit of the tool measuring device 70 to the control device 52. The control device 52 calculates the X-coordinate value X － （１） is read from the position sensing device 60.

[0064] (11) Next, the X-axis, Y-axis, and Z-axis are controlled to position the tool 34 of the attachment spindle 10 at a predetermined second measurement start position P2 that is a predetermined distance away from the laser beam Ly in the +X-axis direction. (12) The X-axis is controlled to move the spindle 114 from the second measurement start position P2 in the -X direction as shown by arrow A2, and the tool 34 of the attachment spindle 10 approaches the laser beam Ly. At this time, the tool 34 may be stationary, but it is preferable to rotate the tool 34 while it approaches the laser beam Ly. (13) When the tool 34 of the attachment spindle 10 blocks the laser beam Ly, a skip signal is output from the skip signal circuit of the tool measuring device 70 to the control device 52. The control device 52 calculates the X-coordinate value X ＋ （１） is read from the position sensing device 60.

[0065] The X-coordinate value X is used as the coordinate value in the movement direction of the rotation axis Oa of the attachment main shaft 10 at the first measurement position Pr1. ｃａ（１） can be expressed by the following formula (11): ｃａ（１） = (X － （１） +X ＋ （１）) / 2=Xs+rcos(φ+θ1)...(11)

[0066] Next, in the Cs-axis control mode, spindle 114 of machine tool 100 is moved to second measurement position Pr2, which is a predetermined rotational position about rotation axis Os. In the example of Fig. 11, second measurement position Pr2 is a rotational position at an angle θ2 from origin position Pr0 around rotation axis Os.

[0067] After the spindle 114 is moved to the second measurement position Pr2, the spindle 114 is fixed at the second measurement position Pr2, and the same steps as the above steps (8) to (13) are carried out to obtain X － （２） and X ＋ （２） is calculated, and based on this, the X coordinate value X of the rotation axis Oa of the attachment spindle 10 at the second measurement position is calculated. ｃａ（２） is calculated using the following equation (12): ｃａ（２） = (X － （２） +X ＋ （２） ) / 2=Xs+rcos(φ+θ2)...(12)

[0068] (14) Next, by controlling the Cs axis, the spindle 114 of the machine tool 100 is again moved to the first measurement position Pr1, which is a predetermined rotational position about the rotation axis Os, and fixed at the first measurement position Pr1. (15) Next, as shown in FIG. 10 , the X-, Y-, and Z-axes are controlled to position the tool 34 of the attachment spindle 10 at a predetermined third measurement start position P3, which is a predetermined distance in the negative Y-axis direction from the laser beam Lx irradiated in the X-axis direction. (16) By controlling the Y-axis, the spindle 114 is moved in the positive direction along the Y-axis from the third measurement start position P3, as shown by arrow B1, so that the tool 34 of the attachment spindle 10 approaches the laser beam Lx. At this time, the tool 34 may be stationary, but it is preferable to rotate the tool 34 while it approaches the laser beam Lx. (17) When the tool 34 of the attachment spindle 10 interrupts the laser beam Lx, a skip signal is output from the skip signal circuit of the tool measuring device 70 to the control device 52. The control device 52 calculates the X coordinate value Y － （１）is read from the position sensing device 60.

[0069] (18) Next, the X-axis, Y-axis, and Z-axis are controlled to position the tool 34 of the attachment spindle 10 at a predetermined fourth measurement start position P4, which is a predetermined distance away from the laser beam Lx in the +Y-axis direction. (19) The Y-axis is controlled to move the spindle 114 in the - direction along the Y-axis from the fourth measurement start position P4, as shown by arrow B2, to move the tool 34 of the attachment spindle 10 toward the laser beam Lx. At this time, the tool 34 may be stationary, but it is preferable to rotate the tool 34 while it approaches the laser beam Lx. (20) When the tool 34 of the attachment spindle 10 blocks the laser beam Lx, a skip signal is output from the skip signal circuit of the tool measuring device 70 to the control device 52. The control device 52 calculates the Y coordinate value Y ＋ （１） is read from the position sensing device 60.

[0070] The Y-coordinate value Y is set as the coordinate value in the movement direction of the rotation axis Oa of the attachment spindle 10 at the first measurement position Pr1 (the coordinate value of the rotation axis Oa measured by moving the spindle 114 in the Y-axis direction). ｃａ（１） can be expressed by the following formula (13): ｃａ（１） = (Y － （１） +Y ＋ （１） ) / 2=Ys+rsin(φ+θ1)...(13)

[0071] Next, in the Cs-axis control mode, the spindle 114 of the machine tool 100 is moved to a second measurement position Pr2, which is a predetermined rotation position around the rotation axis Os.

[0072] After the spindle 114 is moved to the second measurement position Pr2, the spindle 114 is fixed at the second measurement position Pr2, and steps similar to the above steps (15) to (20) are carried out to obtain Y － （２） and Y ＋ （２） is calculated, and based on this, the Y-coordinate value Y is calculated as the movement direction coordinate value of the rotation axis Oa of the attachment spindle 10 at the second measurement position (the coordinate value of the rotation axis Oa measured by moving the spindle 114 in the Y-axis direction). ｃａ（２）is calculated using the following equation (12): ｃａ（２） = (Y － （２） +Y ＋ （２） ) / 2=Ys+rsin(φ+θ2)...(14)

[0073] The obtained X ｃａ（１） , X ｃａ（２） , Y ｃａ（１） , Y ｃａ（２） Based on the equations (9) to (14), the positional deviation in the X-axis direction (amount of deviation in the first direction) δx and the positional deviation in the Y-axis direction (amount of deviation in the second direction) δy of the rotational axis Oa of the attachment spindle 10 from the rotational axis Os of the spindle 114 of the machine tool 100 are expressed by the following equations (15) and (16).

[0074]

[0075] DESCRIPTION OF SYMBOLS 10 Attachment spindle 12 Housing 12a Tapered shank portion 12b V-groove 14 Spindle 14a Tool mounting hole 15 Process 16 Bearing 18 Air chamber 20 Air turbine 22 Air supply passage 24 Exhaust passage 26 Projection portion 26a Recessed portion 28 Ball 32 Cap 34 Tool 36 Collet chuck 38 Cap nut 50 Attachment spindle error measurement system 52 Control device 54 Input portion 56 Servo amplifier 58 Servo motor 60 Position detection device 62 Storage device 70 Tool measurement device 72 Base portion 74a Arm portion 74b Arm portion 76a Laser irradiation portion 76b Laser receiving portion 100 Machine tool 102 Bed 104 Column 106 X-slider 106a Block 108 X-axis guide rail 110 Spindle head 110a Block 112 Z-axis guide rail 114 Spindle 116 Bearing 118 Rotary encoder 120 Table 120a Block 122 Y-axis guide rail 126 Nut 128 Y-axis digital scale 130 Tool holder 132 Engagement portion 200 Control device

Claims

1. A machining method for machining a workpiece on a machine tool equipped with a spindle, in which an attachment spindle incorporating a rotary actuator is mounted on the spindle instead of a tool holder, and the tool mounted on the attachment spindle is rotated by the rotary actuator while the spindle is stopped from rotating, comprising the steps of: mounting the tool holder with a first tool mounted on the spindle; rotating the tool holder with the spindle to machine a workpiece placed on a table; mounting the attachment spindle with a second tool mounted on the spindle instead of the tool holder; indexing the spindle to a plurality of rotational index positions while the attachment spindle is mounted; and determining the position of the rotational axis of the attachment spindle in a first direction perpendicular to the rotational axis of the attachment spindle at each of the plurality of rotational index positions using a sensor mounted on the table; a step of calculating, from the position in a first direction of the rotation axis of the attachment spindle determined at each of the plurality of rotation index positions, an amount of deviation in the first direction of the position of the rotation axis of the attachment spindle relative to the rotation axis of the spindle at a rotation index position where the spindle stops rotating when machining is performed by the attachment spindle, and an amount of deviation in a second direction that is a direction perpendicular to the rotation axis of the attachment spindle and the first direction; and a step of machining the workpiece placed on a table with a second tool rotated by a rotary actuator while correcting the amount of deviation in the first direction and the amount of deviation in the second direction to compensate for the amount of deviation in the first direction.

2. A machining method according to claim 1, wherein the step of determining the position of the rotation axis of the attachment spindle determines the position of the rotation axis of the attachment spindle while rotating a rotary actuator.

3. The processing method according to claim 1, wherein the sensor comprises a laser emitting section that emits a laser beam in a linear pattern and a laser receiving section that receives the laser beam, and outputs a skip signal when the laser beam is blocked.

4. The processing method according to claim 3, further comprising: positioning the sensor so that the laser beam is irradiated in the X-axis or Y-axis direction of the machine tool; and having the spindle of the machine tool approach the laser beam from both directions along the Y-axis or X-axis so that a second tool attached to the attachment spindle crosses the laser beam.

5. The machining method according to claim 3, wherein the sensors include a first sensor arranged so that the laser light is irradiated in the X-axis direction and a second sensor arranged so that the laser light is irradiated in the Y-axis direction, and the machining method includes: causing the spindle of the machine tool to approach the laser light from both directions along the X-axis so that the second tool crosses the laser light irradiated in the Y-axis direction; and causing the spindle of the machine tool to approach the laser light from both directions along the Y-axis so that the second tool crosses the laser light irradiated in the X-axis direction.

6. A processing method according to claim 4 or 5, wherein when the spindle of the machine tool is brought closer to the laser beam, the attachment spindle is brought closer to the laser beam while being rotated.

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