Method for correcting relative position between workpiece and workpiece to be machined

Abstract

To provide a method for correcting relative positions between a workpiece and a processing bodies in processing with high precision for a machine tool that has a movable workpiece main-shaft base, a work main shaft which is mounted on the movable workpiece main-shaft base and holds the workpiece, a processing body holding part which holds a processing body, a moving base which supports the processing body holding part movably, and a sending mechanism part which can change relative positions between the movable work main-shaft base and processing body moving base.SOLUTION: After a movable workpiece main-shaft base 4 is moved to a scheduled position for use in workpiece processing, a quantity of deviation in relative position between a workpiece main shaft 11 of the movable workpiece main-shaft base 4 and a processing body holding part 7 is calculated, a quantity of deviation in relative position between a workpiece W and a processing body T in workpiece processing is estimated based upon the calculated quantity of deviation, and a sending mechanism part is so controlled as to correct the estimated quantity of deviation.SELECTED DRAWING: Figure 6A

Description

[Technical Field]

[0001] The present invention relates to a correction method for correcting the relative position between a workpiece and a workpiece machined on a machine tool having a movable workpiece headstock that is movable in a predetermined direction. [Background technology]

[0002] Conventionally, a correction method for correcting the relative position between a workpiece and a tool (machined body) during machining in a machine tool has been known (see, for example, Patent Document 1). This correction method is applied to a machining center having a tilt table, and before machining of the workpiece begins, a reference sphere is attached to the tilt table and the deviation amount of the center position of the reference sphere is measured by a touch probe attached to the tool spindle. Then, after machining of the workpiece begins, machining control is performed so as to correct the relative position between the workpiece and the tool based on the measured deviation amount. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-194451 Summary of the Invention [Problem to be solved by the invention]

[0004] The correction method disclosed in Patent Document 1 can also be applied to a lathe-type multi-tasking machine. This multi-tasking machine typically has a work spindle that holds a workpiece, a work headstock on which the work spindle is mounted, a workpiece holder that holds a tool (workpiece), a workpiece moving table that can move with the workpiece holder mounted, and a feed mechanism that can change the relative positions of the work headstock and the workpiece moving table. By attaching a reference sphere (reference object) to the workpiece spindle and a touch probe (measurement sensor) to the workpiece holder, the relative positions of the workpiece and the workpiece can be corrected in the same manner as in Patent Document 1. The workpiece holder can be configured, for example, by a tool spindle that holds a rotating tool (workpiece) or a turret that holds a non-rotating tool (workpiece) on its circumferential surface.

[0005] There are two types of work headstocks: a fixed type that is immovably fixed to the machine tool, and a movable type that is movable in a predetermined direction. If an attempt is made to apply the compensation method using the reference object to a machine tool that has a movable work headstock, the following problems arise.

[0006] That is, the position of the movable work headstock during workpiece machining is changed depending on the size of the workpiece to be machined, etc. This causes a situation in which the position of the movable work headstock when the reference object is measured differs from the position of the movable work headstock during actual machining. If the position of the movable work headstock differs between when the reference object is measured and when the workpiece is machined, there is a problem in that even if the relative positions of the workpiece and the workpiece during workpiece machining are corrected based on the position information of the measured reference object, the correction accuracy cannot be sufficiently ensured.

[0007] The present invention has been made in view of the above-mentioned circumstances, and has as its object to provide a correction method capable of correcting with high precision the relative position between a workpiece and a workpiece to be machined during workpiece machining in a machine tool equipped with a movable workpiece headstock that can be moved in a predetermined direction. [Means for solving the problem]

[0008] A first invention relates to a correction method for correcting the relative position of a workpiece and the workpiece during machining in a machine tool having a movable work headstock that can be moved in a predetermined direction, a work spindle mounted on the movable work headstock and holding a workpiece, a workpiece holder that holds a workpiece for machining the workpiece, a workpiece moving table that can be moved in a predetermined direction with the workpiece holder mounted thereon, and a feed mechanism that can change the relative positions of the movable work headstock and the workpiece moving table, the correction method comprising: a moving step of moving the movable work headstock by the feed mechanism to a position where it will be used during workpiece machining before machining of the workpiece is started; a positional deviation calculation step of calculating the amount of deviation of the relative position between the workpiece spindle mounted on the movable work headstock that has moved to the intended use position and the workpiece holding table; and a correction control step of estimating the amount of deviation of the relative position between the workpiece and the workpiece during workpiece machining based on the amount of deviation calculated in the positional deviation calculation step, and controlling the feed mechanism to correct the estimated amount of deviation.

[0009] According to the first aspect of the present invention, in a moving step, a movable work headstock supporting a work spindle is moved to a position where it is intended to be used during work machining. Then, in a positional deviation calculation step, the amount of deviation in the relative position between the work spindle mounted on the movable work headstock moved to the intended use position and the workpiece holder is calculated. The steps up to this point are performed before the workpiece is machined. After the start of workpiece machining, in a correction control step, the amount of deviation in the relative position between the workpiece and the workpiece during workpiece machining is estimated based on the amount of deviation in the relative position between the work spindle and the workpiece holder calculated in the positional deviation calculation step, and the feed mechanism is controlled to correct the estimated amount of deviation.

[0010] Therefore, even if the relative positional relationship between the work spindle and the workpiece holder changes due to wear of machine elements or the like, and the amount of deviation in the relative position between the workpiece and the workpiece occurs individually depending on the position of the movable workpiece headstock, the amount of deviation can be appropriately corrected by the feed mechanism during workpiece machining. Therefore, even if the position of the movable workpiece headstock is changed depending on the size of the workpiece, the machining accuracy of the workpiece by the workpiece can be improved.

[0011] The second invention further comprises an attachment step of attaching a reference object to either the work spindle or the workpiece holder mounted on the movable work headstock before starting machining of the workpiece, and attaching a measurement sensor capable of measuring position information of the reference object to the work spindle or the workpiece holder to which the reference object is not attached, and in the positional deviation calculation step, the positional information of the reference object is measured by the measurement sensor, and the amount of deviation in the relative position between the work spindle and the workpiece holder is calculated based on the measured position information.

[0012] According to the second aspect of the present invention, it is possible to grasp the amount of deviation through in-machine measurement using the movable work headstock and the workpiece holder.

[0013] In a third aspect of the present invention, in the attaching step, the reference object is attached to the work spindle mounted on the movable work headstock, and the measurement sensor is attached to the workpiece holder. According to the third aspect of the present invention, the measurement sensor is attached to the workpiece holder. For example, by using an automatic tool changer (ATC) to exchange the tool and measurement sensor, the attachment work is simplified while ensuring attachment accuracy. Furthermore, the position of the reference object attached to the workpiece spindle is measured after the movable workpiece headstock is moved to the intended use position during workpiece machining. Therefore, the position of the movable workpiece headstock can be matched during measurement of the reference object and during workpiece machining. Therefore, even in a machine tool equipped with a movable workpiece headstock, the relative positions of the workpiece and the workpiece during workpiece machining can be accurately corrected based on the measured position information of the reference object.

[0014] A fourth invention is related to the third invention, wherein the machine tool further comprises a fixed work headstock that is immovably fixed at a predetermined position and holds a work spindle that opposes the work spindle of the movable work headstock on the same axis; the mounting step further comprises a step of mounting a reference object to the work spindle mounted on the fixed work headstock before starting machining of the work; the positional deviation calculation step further comprises a step of measuring positional information of the reference object mounted to the work spindle of the fixed work headstock by the measurement sensor mounted on the workpiece holder, and calculating an amount of deviation in relative position between the work spindle of the fixed work headstock and the workpiece holder based on the measured positional information; and the correction control step estimates an amount of deviation in relative position between the work and the workpiece during machining based on the amount of deviation in relative position between each work spindle and the workpiece holder calculated in the positional deviation calculation step, and controls the feed mechanism to correct the estimated amount of deviation.

[0015] According to the fourth aspect of the present invention, for a machine tool equipped with a movable work headstock and a fixed headstock opposite the movable work headstock, in the positional deviation calculation step, in addition to positional information of a reference object attached to the work spindle of the fixed work headstock, a measurement sensor measures positional information of a reference object attached to the work spindle of the movable work headstock, and based on the measured positional information of each reference object, the amount of deviation in the relative position between each work spindle and the workpiece holder is calculated, and based on the calculated amount of deviation in each relative position, the amount of deviation in the relative position between the workpiece and the workpiece during workpiece machining is estimated, and the feed drive unit is controlled to correct each estimated amount of deviation, thereby making it possible to appropriately correct the amount of deviation even in a machine tool equipped with both the movable work headstock and the fixed work headstock.

[0016] A fifth aspect of the invention is related to the third aspect of the invention, wherein two movable work headstocks are provided, and the two movable work headstocks are arranged so that the work spindles mounted on each of the movable work headstocks are coaxially opposed to each other; in the mounting step, a reference object is mounted on each work spindle mounted on each movable work headstock; in the moving step, each movable work headstock is moved to a planned use position during work machining; in the positional deviation calculation step, positional information of each reference object is measured by the measurement sensor attached to the workpiece holder, and based on the measured positional information of each reference object, an amount of deviation in relative position between each work spindle mounted on each movable work headstock and the workpiece holder is calculated; and in the correction control step, an amount of deviation in relative position between the workpiece and the workpiece during machining is estimated based on the amount of deviation in relative position between each work spindle and the workpiece holder calculated in the positional deviation calculation step, and the feed mechanism is controlled to correct the estimated amount of deviation.

[0017] According to the fifth aspect of the invention, in a machine tool having two movable work headstocks arranged opposite each other, after each movable work headstock is moved to a position where it is intended to be used during workpiece machining, the position information of each reference object attached to the work spindle of each movable work headstock is measured by a measurement sensor, and based on the position information of each measured reference object, the amount of deviation of the relative position between each work spindle mounted on each movable work headstock and the workpiece holder is calculated, and based on each calculated amount of deviation, the amount of deviation of the relative position between the workpiece and the workpiece during workpiece machining is estimated, and the estimated amount of deviation is corrected by a feed mechanism, so that even in a machine tool having a plurality of movable work headstocks, appropriate correction of the amount of deviation can be performed.

[0018] The sixth invention is the fourth or fifth invention, wherein in the correction control step, during machining of the workpiece, the amount of deviation of the relative position between each workpiece spindle and the workpiece holder calculated in the position deviation calculation step is interpolated according to the position of the workpiece in the opposing direction of each workpiece spindle, and the interpolated value is estimated as the amount of deviation of the relative position between the workpiece and the workpiece at the position of the workpiece, and the feed mechanism is controlled to correct the estimated amount of deviation.

[0019] According to the sixth aspect of the present invention, it is possible to achieve appropriate correction in various usage modes without actually measuring the amount of deviation for all combinations of each work spindle and each planned use position of the workpiece holder.

[0020] The seventh invention is the fourth or fifth invention, wherein the machine tool is configured to machine the workpiece held by the workpiece holder, with both ends of the workpiece in the extension direction supported by two opposing workpiece spindles, and the correction control process, during machining of the workpiece, linearly interpolates the amount of deviation in the relative position between each workpiece spindle and the workpiece holder calculated in the position deviation calculation process according to the position of the workpiece in the extension direction of the workpiece, to estimate the amount of deviation in the relative position between the workpiece and the workpiece at the position of the workpiece, and controls the feed mechanism to correct the estimated amount of deviation.

[0021] According to the seventh invention, during machining of the workpiece, both ends of the workpiece in the extension direction are supported by the two workpiece spindles, and focusing on the point where the workpiece is located between the two workpiece spindles, the amount of deviation of the relative position between each workpiece spindle and the workpiece holder calculated in the position deviation calculation step is linearly interpolated according to the position of the workpiece in the workpiece extension direction, thereby estimating the amount of deviation of the relative position between the workpiece and the workpiece at that position of the workpiece. According to this, if the amount of deviation is measured at representative points (both ends of the workpiece), the amount of deviation at any position of the workpiece can be estimated and the feed mechanism can be corrected, thereby reducing the effort required for actually measuring the amount of deviation and achieving high accuracy.

[0022] An eighth invention is any one of the first to seventh inventions, wherein the machine tool comprises a swivel drive shaft connected to the workpiece moving table and rotatable around a predetermined axis, a swivel drive unit that rotationally drives the swivel drive shaft, and a rotation fixing mechanism that fixes the swivel drive shaft so that it cannot rotate, the rotation fixing mechanism having a plurality of fixing mechanism units that can fix the swivel drive shaft so that it cannot rotate, and configured to be switchable between a plurality of operating states with different combinations of operation / non-operation of the plurality of fixing mechanism units, and the positional deviation calculation step is The correction control step is executed in each of the above states, and during the machining of the workpiece, it is determined which of the plurality of operating states the operating state of the rotation fixing mechanism at the current time corresponds to, and among the amounts of deviation of the relative position between the workpiece spindle and the workpiece holding unit calculated in the position deviation calculation step, the amount of deviation of the relative position between the workpiece and the workpiece holding unit that corresponds to the determined operating state is identified, and based on the identified amount of deviation, the amount of deviation of the relative position between the workpiece and the workpiece is estimated, and the feed mechanism unit is controlled to correct the estimated amount of deviation.

[0023] The ninth invention is the eighth invention, wherein the rotation fixing mechanism has, as the multiple fixing mechanism parts, a first fixing mechanism part that mechanically fixes the swivel drive shaft, and a second fixing mechanism part that is an electromagnetic brake mechanism attached to the swivel drive part.

[0024] According to the eighth and ninth aspects of the present invention, the amount of deviation in the relative position between the workpiece and the workpiece can be corrected with high precision according to the operating state of the rotation fixing mechanism of the swivel drive shaft. Therefore, even if the operation of the rotation fixing mechanism causes deformation of the support structure of the workpiece moving table or bending deformation of the swivel drive shaft, the relative positions of the workpiece and the workpiece can be corrected with high precision during workpiece machining, and the positional relationship between the two can be maintained constant. This in turn makes it possible to improve the machining accuracy of the workpiece by the workpiece as much as possible.

[0025] A tenth invention is any one of the first to ninth inventions, wherein the machine tool comprises a swivel drive shaft connected to the workpiece transfer table and rotatable about a predetermined axis, and a swivel drive unit that rotationally drives the swivel drive shaft; in the positional deviation calculation step, the swivel drive unit rotates the swivel drive shaft to change the angle of the workpiece transfer table about the predetermined axis to a plurality of predetermined angular positions, and measures position information of the reference object at each angular position, and calculates the amount of deviation in the relative position between the workpiece spindle and the workpiece holder based on the measured position information; and in the correction control step, the swivel angle of the swivel drive shaft about the predetermined axis is obtained during machining of the workpiece, and the amount of deviation at each measured position calculated in the positional deviation calculation step is linearly interpolated according to the obtained swivel angle to estimate the amount of deviation in the relative position between the workpiece and the workpiece, and the feed mechanism is controlled to correct the estimated amount of deviation.

[0026] According to the tenth aspect of the present invention, the relative position between the workpiece and the workpiece can be appropriately corrected according to the rotation angle of the workpiece moving table around a predetermined axis, thereby improving the machining accuracy of the workpiece by the workpiece as much as possible.

[0027] In the eleventh invention, in the positional deviation calculation process, the amount of deviation in the relative position between the work spindle and the workpiece holder is calculated based on an image captured by a camera inside or outside the machine tool.

[0028] According to the eleventh aspect of the present invention, it is possible to measure the amount of deviation in the relative position between the work spindle and the workpiece holder in a non-contact manner, for example, by using an in-machine camera of a machine tool or a camera mounted on a robot such as an AGV that carries in and out workpieces.

[0029] A twelfth invention relates to a machine tool having a movable work headstock movable in a predetermined direction, a work spindle mounted on the movable work headstock and holding a workpiece, a workpiece holder that holds a workpiece for machining the workpiece, a workpiece moving table that is movable in the predetermined direction with the workpiece holder mounted thereon, and a feed mechanism that can change the relative positions of the movable work headstock and the workpiece moving table, and the machine tool is equipped with a program execution unit that is configured to execute the following steps: a moving step of moving the movable work headstock by the feed mechanism to a position where it will be used during workpiece machining before machining of the workpiece is started; a positional deviation calculation step of calculating the amount of deviation in the relative position between the workpiece spindle mounted on the movable work headstock that has moved to the intended use position and the workpiece holder; and a correction control step of estimating the amount of deviation in the relative position between the workpiece and the workpiece during workpiece machining based on the amount of deviation calculated in the positional deviation calculation step, and controlling the feed mechanism to correct the estimated amount of deviation.

[0030] According to the twelfth aspect of the present invention, the amount of deviation in the relative position between the work spindle and the workpiece holder can be automatically measured and corrected in accordance with the position of the movable work headstock specified in a machining program, for example, thereby realizing a machine tool with high machining accuracy.

[0031] A thirteenth invention relates to a program for use in a machine tool having a movable work headstock movable in a predetermined direction, a work spindle mounted on the movable work headstock and holding a workpiece, a workpiece holder that holds a workpiece for machining the workpiece, a workpiece moving table that is movable in the predetermined direction with the workpiece holder mounted thereon, and a feed mechanism that can change the relative positions of the movable work headstock and the workpiece moving table, the program causing a computer to function as a correction unit that is configured to execute the following steps before machining of the workpiece is started: a movement step of moving the movable work headstock by the feed mechanism to a position where it will be used during workpiece machining; a positional deviation calculation step of calculating the amount of deviation in the relative position between the workpiece spindle mounted on the movable work headstock that has moved to the intended use position and the workpiece holder; and a correction control step of estimating the amount of deviation in the relative position between the workpiece and the workpiece during workpiece machining based on the amount of deviation calculated in the positional deviation calculation step, and controlling the feed mechanism to correct the estimated amount of deviation.

[0032] By using the thirteenth aspect of the invention, it is possible to achieve the same effect as the twelfth aspect of the invention by updating the program of an existing machine tool. Note that the program for the machine tool may be distributed electronically or may be recorded on a program recording medium such as a CD, DVD, HDD, or flash memory. [Effects of the Invention]

[0033] According to the correction method of the present invention, the amount of deviation in the relative position between the work spindle of the movable work headstock and the workpiece holder after the movable work headstock has been moved to a position where it is planned to be used during workpiece machining is calculated, the amount of deviation in the relative position between the workpiece and the workpiece during workpiece machining is estimated based on the calculated amount of deviation, and the feed mechanism is controlled to correct the estimated amount of deviation, so that the relative position between the workpiece and the workpiece during workpiece machining can be corrected with high precision even in a machine tool equipped with a movable work headstock. [Brief explanation of the drawings]

[0034] [Figure 1] 1 is an overall perspective view showing an example of a machine tool that realizes a method for correcting the relative position between a workpiece and a tool according to an embodiment. FIG. [Figure 2] FIG. 1 is a vertical cross-sectional view taken along the B axis showing the support structure of the tool headstock by the swivel drive shaft. [Figure 3] 10 is a table for explaining the operating state of a rotation fixing mechanism of a swivel drive shaft connected to a tool headstock. [Figure 4] FIG. 2 is a block diagram showing a control configuration of the machine tool. [Figure 5] FIG. 10 is a perspective view showing how a reference sphere attached to a first workpiece spindle is measured by a touch probe attached to a tool spindle. [Figure 6A] FIG. 10 is an explanatory diagram for explaining the operation of measuring the reference sphere by the machine tool. [Figure 6B] FIG. 10 is an explanatory diagram for explaining the operation of measuring the reference sphere by the machine tool. [Figure 6C] FIG. 10 is an explanatory diagram for explaining the operation of measuring the reference sphere by the machine tool. [Figure 7] FIG. 10 is an explanatory diagram for explaining positional deviation data generated by the measurement data processing device. [Figure 8] 1 is a schematic diagram showing a state in which a workpiece, both ends of which are supported by a first workpiece spindle and a second workpiece spindle, is machined by a tool held by a tool spindle. [Figure 9] FIG. 8 is a view corresponding to FIG. 7 and shows the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0035] 1 is an overall perspective view showing an example of a machine tool 1 that realizes a method for correcting the relative position between a workpiece W and a tool T (an example of a workpiece) in an embodiment. In the following description, the front side and the rear side refer to the front side and the rear side of the machine tool 1, respectively, and the left side and the right side refer to the left side and the right side when the machine tool 1 is viewed from the front side.

[0036] The machine tool 1 in this example is a five-axis controlled compound lathe and includes a bed 2, a first workpiece headstock 3 and a second workpiece headstock 4 arranged on the bed 2 so as to face each other in the Z-axis direction (left-right direction), a turret tool rest 5 arranged between the first workpiece headstock 3 and the second workpiece headstock 4 so as to be movable in the X-axis (up-down) direction and the Z-axis direction, a tool headstock 6 (an example of a workpiece moving table) arranged on the bed 2 so as to be movable in the X-axis, Y-axis (front-back) direction and the Z-axis direction, a tool spindle 7 (an example of a workpiece holding unit) held by the tool headstock 6 and which rotates a tool T, and a control device 50 (see FIG. 4) which controls the operation of each part of the machine tool 1. On the left side of the workpiece machining area on the bed 2, a tool changer 8 is arranged which automatically exchanges the tool T attached to the tool spindle 7 for a tool T to be used in the next process.

[0037] The first work headstock 3 is fixed to the upper surface of the bed 2 and holds the first work spindle 10 rotatably about the C-axis, which is parallel to the Z-axis. Meanwhile, the second work headstock 4 holds the second work spindle 11 coaxially with the first work spindle 10 and rotatably about the C-axis, and is movable in the Z-axis direction by a pair of guide rails (not shown) provided on the upper surface of the bed 2, and is moved in the Z-axis direction by a feed motor 33a and a feed screw (not shown). The first work spindle 10 is driven by a first spindle motor (not shown), and the second work spindle 11 is driven by a second spindle motor (not shown). The first work headstock 3 constitutes a fixed work headstock, and the second work headstock 4 constitutes a movable work headstock.

[0038] The turret tool rest 5 has a turret 5a that can rotate around an axis parallel to the Z axis, and is configured to be movable in the Z-axis direction and the X-axis direction by a feed motor and a feed screw (both not shown). Turning tools 5b are radially arranged at intervals around the periphery of the turret 5a.

[0039] The tool headstock 6 is connected to a column 12 erected on the upper surface of the bed 2 via a saddle 13 , a slider 14 , and a ram 15 .

[0040] The column 12 is gate-shaped and spans both the left and right ends of the upper surface of the bed 2. The saddle 13 is configured to be movable in the Z-axis direction by a pair of guide rails (not shown) provided on the front side of the column 12, and is moved in the Z-axis direction by a pair of feed screws 37 and a pair of feed motors 33b.

[0041] The slider 14 is movable in the X-axis direction by a pair of guide rails provided on the front side of the saddle 13, and is moved in the X-axis direction by a pair of feed screws 38 and a pair of feed motors 33c.

[0042] The ram 15 is supported by a guide plate (not shown) so as to be movable in the Y-axis direction while inserted into a ram guide hole 14a formed in the slider 14. The ram 15 is moved in the Y-axis direction by a feed screw (not shown) and a feed motor 33d that are arranged at the lower end of the center of the slider 14 in the width direction.

[0043] As shown in FIG. 2, the tool headstock 6 is fixed to a swivel drive shaft 16 that is rotatably supported on a ram 15, and is configured to be swivelable around a B-axis (an example of a predetermined axis) that is parallel to the Y-axis by a swivel motor 31 (an example of a swivel drive unit) that is connected to the swivel drive shaft 16.

[0044] The slewing drive shaft 16 is supported rotatably about the B axis by a front bearing 17 and a rear bearing (not shown) provided in the ram 15, and is configured so that rotation about the B axis can be fixed by a rotation fixing mechanism 35. The rotation fixing mechanism 35 includes an electromagnetic brake mechanism 32 attached to the slewing motor 31, and a coupling mechanism 30 provided in the ram 15. The coupling mechanism 30 corresponds to a first fixing mechanism, and the electromagnetic brake mechanism 32 corresponds to a second fixing mechanism.

[0045] The electromagnetic brake mechanism 32 can employ a known configuration including a movable member that rotates together with the motor shaft and a friction member that is driven in the axial direction by electromagnetic force and comes into contact with the movable member.

[0046] The coupling mechanism 30 has an annular piston 30a located forward of the front bearing 17. The piston 30a is hydraulically movable parallel to the B axis. Interlocking teeth are formed on the rear end surface of the piston 30a in an annular region centered on the B axis. Similarly, interlocking teeth are formed on the front surfaces of the outer ring 17a and the inner ring 17b of the front bearing 17 in annular regions centered on the B axis. The interlocking teeth of the piston 30a, the interlocking teeth of the outer ring 17a of the front bearing 17, and the interlocking teeth of the inner ring 17b of the front bearing 17 form a three-piece coupling. When the piston 30a moves rearward, the interlocking teeth of the piston 30a mesh with the interlocking teeth of the outer ring 17a and the inner ring 17b of the front bearing 17. This prevents the swivel drive shaft 16 from rotating, and the tool headstock 6 connected to the swivel drive shaft 16 is clamped at a desired swivel angle.

[0047] The rotation locking mechanism 35 is configured to be switchable between a plurality of operating states that vary the operation / non-operation of the coupling mechanism 30 and the electromagnetic brake mechanism 32. As shown in FIG. 3 , the plurality of operating states are a coupling operating state in which only the coupling mechanism 30 is operating, a brake operating state in which only the electromagnetic brake mechanism 32 is operating, and a lock-release state in which both the coupling mechanism 30 and the electromagnetic brake mechanism 32 are deactivated. In the coupling operating state and the brake operating state, the tool headstock 6 is fixed so as not to rotate together with the swivel drive shaft 16, allowing milling and turning to be performed with a tool T attached to the tool spindle 7. The user can freely select either the coupling operating state or the brake operating state for milling and turning. In the lock-release state, the tool headstock 6 is rotatable around the B-axis together with the swivel drive shaft 16, allowing contouring to be performed with a tool T attached to the tool spindle 7. In the positional deviation measurement mode described later, the rotation fixing mechanism 35 is controlled to the same state every time (in this example, the coupling operating state as an example).

[0048] The tool headstock 6 has a built-in spindle motor that rotates and drives a tool spindle 7, and a tool T is detachably attached to the tip of the tool spindle 7. Also, a touch probe 20, which will be described later, can be attached to the tip of the tool spindle 7 in place of the tool T.

[0049] The touch probe 20 is a contact-type measurement sensor, and is used in a positional deviation measurement mode that is performed before starting machining of the workpiece W. The positional deviation measurement mode is a mode separate from the normal operation mode in which the workpiece W is machined, and is a mode for measuring the amount of deviation in the relative position between the tool spindle 7 and each of the workpiece spindles 10, 11 by measuring a reference sphere 9a (see FIG. 5) attached to each of the workpiece spindles 10, 11 with the touch probe 20. The amount of deviation measured in the positional deviation measurement mode is used as a correction amount when machining the workpiece W in the normal operation mode.

[0050] 4, the control device 50 is composed of a program storage unit 51, a program execution unit 52, and a drive control unit 53. An NC operation panel 60 and a measurement data processing device 70 are connected to the control device 50. The control device 50, the NC operation panel 60, and the measurement data processing device 70 are each composed of a computer including a CPU, RAM, ROM, etc.

[0051] The NC operation panel 60 has an input unit 61 and a display unit 62. The display unit 62 is capable of displaying the execution status of the NC program 51a in the program execution unit 52, etc. The input unit 61 has a mode selection button 61a, a cycle execution button 61b, and a measurement start button 61c. The mode selection button 61a is a button for selecting either a normal operation mode or a positional deviation measurement mode. The cycle execution button 61b is a button for causing the machine tool 1 to execute a machining operation of the workpiece W based on the NC program 51a in the normal operation mode. The measurement start button 61c is a button for causing the machine tool 1 to start a positional deviation measurement process using the touch probe 20 in the positional deviation measurement mode.

[0052] The program storage unit 51 stores an NC program 51a that is executed in the normal operation mode, and a positional deviation measurement program 51b that is executed in the positional deviation measurement mode.

[0053] The program execution unit 52 executes the NC program 51a or the positional deviation measurement program 51b in accordance with a command input from the input unit 61 of the NC operation panel 60, and transmits command signals (such as a speed command signal or a position command signal) defined in each of the programs 51a, 51b to the drive control unit 53. Specifically, when the cycle execution button 61b is pressed with the normal operation mode selected by the mode selection button 61a, the program execution unit 52 executes the NC program 51a stored in the program storage unit 51, and transmits a command signal to the drive control unit 53 to cause the machine tool 1 to perform the operation defined in the NC program 51a.

[0054] When the positional deviation measurement mode is selected by the mode selection button 61a and the measurement start button 61c is pressed, the program execution unit 52 executes the positional deviation measurement program 51b stored in the program memory unit 51 and sends a command signal to the drive control unit 53 to cause the machine tool 1 to perform the measurement operation of the reference sphere 9a using the touch probe 20.

[0055] The drive control unit 53 is a functional unit that controls the operation of the feed motor 33 (an example of a feed mechanism unit), spindle motor 34, swing motor 31, coupling mechanism 30, and electromagnetic brake mechanism 32. The feed motor 33 is a motor for realizing feed operations in the X-axis, Y-axis, and Z-axis directions, and is composed of the above-mentioned feed motors 33a to 33d, etc. The spindle motor 34 is composed of motors that drive the first workpiece spindle 10, second workpiece spindle 11, and tool spindle 7, etc. In the normal operation mode, the drive control unit 53 controls the drive of the feed motor 33 to correct the amount of deviation in the relative position between the workpiece W and the tool T, based on positional deviation data generated by a measurement data processing device 70, which will be described later.

[0056] 5, the touch probe 20 has a stylus 21, a spherical contact point 22 fixed to the tip of the stylus 21, and a circuit case 23 connected to the base end of the stylus 21. An output circuit is housed within the circuit case 23. The output circuit detects the displacement of the stylus 21 when the contact point 22 comes into contact with the object to be measured (in this example, a reference sphere 9a, which will be described later) and outputs an ON / OFF signal. The ON / OFF signal output from the output circuit is input to a measurement data processing device 70.

[0057] As will be described later, the reference sphere 9a is attached by an operator to the end faces of the first work spindle 10 and the second work spindle 11. The reference sphere 9a is fixed integrally to a mounting jig 9b, and the mounting jig 9b is positioned and fixed to the end faces of the work spindles 10, 11 (only the first work spindle 10 is shown in FIG. 5).

[0058] The touch probe 20 is attached to the tool spindle 7, and as the tool headstock 6 moves in accordance with the measurement operation of the machine tool 1, the probe stylus 22 at the tip of the probe comes into contact with the reference sphere 9a in five directions: -X, +X, -Y, +Y, and +Z (see arrows in FIG. 5). When the probe stylus 22 comes into contact, an on / off signal is output from the touch probe 20 and input to the measurement data processing device 70. Note that the number of measurement points by the touch probe 20 is not necessarily limited to five, as long as three or more points are secured.

[0059] As shown in FIG. 4, the measurement data processing device 70 includes a positional deviation calculation unit 71 and a data storage unit 72. The positional deviation calculation unit 71 calculates the contact position between the stylus 22 of the touch probe 20 and the reference sphere 9a based on an on / off signal input from the touch probe 20, and calculates the center position of the reference sphere 9a (an example of position information) based on the calculated contact position. The positional deviation calculation unit 71 then calculates the amount of deviation of the calculated center position of the reference sphere 9a from its normal position (a position geometrically determined based on design values) and generates the calculated deviation data as positional deviation data, which is the amount of deviation between the tool spindle 7 and each workpiece spindle 10, 11 to which the reference sphere 9a is attached. The positional deviation calculation unit 71 then stores the generated positional deviation data in the data storage unit 72. The normal position of the reference sphere 9a attached to the workpiece spindle 10 of the first workpiece headstock 3, which is a fixed headstock, is geometrically determined based on design values. On the other hand, the normal position of the reference sphere 9a attached to the work spindle 11 of the second work headstock 4, which is a movable headstock, may be determined based on, for example, a design value, a command value for moving the second work headstock 4 to the intended use position, an output value of a linear scale that detects the position of the second work headstock 4 in the movement direction, or a movement distance calculated from an output value of a rotary encoder of the feed motor 33 that drives the second work headstock 4, etc.

[0060] Next, the measurement process of the reference sphere 9a in the positional deviation measurement mode will be described in detail with reference to FIGS. 6A to 6C.

[0061] 6A, first, an operator attaches a reference sphere 9a to each of the first work spindle 10 and the second work spindle 11, and also attaches the touch probe 20 (an example of a measurement sensor) to the tool spindle 7. Note that the attachment of the touch probe 20 to the tool spindle 7 may be performed automatically by the tool changer 8.

[0062] After completing the installation of the reference sphere 9a and the touch probe 20, the operator selects the positional deviation measurement mode using the mode selection button 61a on the NC operation panel 60. In the positional deviation measurement mode, operations such as the cycle execution button 61b used in the normal operation mode are disabled. In this positional deviation measurement mode, when the operator presses the measurement start button 61c, the program execution unit 52 of the control device 50 executes the positional deviation measurement program 51b, and the machine tool 1 starts a measurement operation under the control of the drive control unit 53. In this measurement operation, as shown in FIG. 6B , under the control of the drive control unit 53, the feed motor 33 moves the second workpiece headstock 4 to a position where it will be used during NC machining of the workpiece W. This position where it will be used is identified by the drive control unit 53 by analyzing the NC program 51a stored in the program storage unit 51. In the example of Figure 6B, the planned use position of the second work headstock 4 (position indicated by the solid line) is shown to be located to the left of its original position (position indicated by the two-dot chain line), but this is not limited to this, and the planned use position of the second work headstock 4 may also be located to the right of its original position.

[0063] After the second workpiece headstock 4 has moved to the intended use position, as shown in Fig. 6C, under the control of the drive control unit 53, the feed motor 33 and the swivel motor 31 sequentially move the tool headstock 6 to a plurality of predetermined angular positions (in this example, three angular positions where the swivel angle θ around the B axis is 0°, 45°, and 90°) relative to each reference sphere 9a. At each angular position, the stylus 22 of the touch probe 20 comes into contact with the reference sphere 9a from the five directions (-X, +X, -Y, +Y, and +Z; see Fig. 5), and the on / off signals output from the touch probe 20 are input to the measurement data processor 70. As described above, the measurement data processor 70 calculates the amount of deviation of the center position of each reference sphere 9a based on the on / off signals from the touch probe 20, and stores the calculated amount of deviation in the data memory unit 72 as positional deviation data.

[0064] 7 shows an example of positional deviation data stored in the data storage unit 72 of the measurement data processing device 70. The top three rows represent the positional deviation amounts in the X-axis, Y-axis, and Z-axis directions of the center position of the reference sphere 9a attached to the first workpiece spindle 10, while the bottom three rows represent the positional deviation amounts in the X-axis, Y-axis, and Z-axis directions of the center position of the reference sphere 9a attached to the second workpiece spindle 11. The positional deviation amounts are displayed in three columns according to the rotation angle θ of the tool headstock 6 about the B-axis. The first, second, and third columns from the left correspond to rotation angles θ of 0°, 45°, and 90°, respectively. The deviation amount of the center position of the reference sphere 9a of the first work spindle 10 shown in the positional deviation data corresponds to the deviation amount of the relative position between the first work spindle 10 and the tool spindle 7, and the deviation amount of the center position of the reference sphere 9a of the second work spindle 11 corresponds to the deviation amount of the relative position between the second work spindle 11 and the tool spindle 7. Note that in Fig. 7, the deviation amount is represented by three letters (for example, XL0) for convenience, but in reality, these are replaced with numerical values.

[0065] Next, the correction control of the relative position between the workpiece W and the tool T, which is executed by the drive control unit 53 of the control device 50 based on the positional deviation data in the normal operation mode, will be described.

[0066] The drive control unit 53 first estimates the amount of deviation in the relative position between the workpiece W and the tool T that is predicted to occur when processing control of the workpiece W is executed based on the NC program, based on the position deviation data stored in the data memory unit 72.

[0067] Specifically, the drive control unit 53 estimates, as the amount of deviation in the relative position between the workpiece W and the tool T, a value obtained by linearly interpolating the positional deviation data in accordance with the position of the tool T in the Z-axis direction during workpiece machining and the swing angle θ of the tool headstock 6 about the B-axis. Here, when the estimated values ​​of the deviations in the X-axis, Y-axis, and Z-axis directions are δx, δy, and δz, the distances from both ends of the workpiece W to the tip position of the tool T during machining are a and b (see FIG. 8), and the swing angle of the tool headstock 6 about the B-axis is θ, the estimated deviation δx is calculated using the following formula: Note that the deviations δy and δz in the Y-axis and Z-axis directions can be calculated in the same way as the deviation δx in the X-axis direction, and therefore a detailed calculation formula will be omitted here.

[0068] δx=K1+(K2-K1)×{a / (a+b)} where:

[0069] (i) When the rotation angle of the tool headstock 6 around the B axis is 0° or more and 45° or less K1=(XL45-XL0)×θ / 45 K2=(XR45-XR0)×θ / 45

[0070] (ii) When the rotation angle of the tool headstock 6 around the B axis is 45° or more and 90° or less K1=XL45+(XL90-XL45)×θ / 45 K2=XR45+(XR90-XR45)×θ / 45 The drive control unit 53 then controls the feed motor 33 to correct the estimated deviations δx, δy, and δz, thereby correcting the position of the tool headstock 6 in the X-, Y-, and Z-axis directions. As an example, if δx is 10 μm, δy is 15 μm, and δz is −20 μm, the drive control unit 53 controls the feed motor 33 to correct the position of the tool headstock 6 by −10 μm in the X-axis direction, −15 μm in the Y-axis direction, and +20 μm in the Z-axis direction relative to the position defined by the NC program 51 a. This corrects the deviations in the relative positions of the tool T and workpiece W, thereby improving the machining accuracy of the workpiece W.

[0071] As described above, according to this embodiment, the center positions of the reference spheres 9a attached to the first workpiece spindle 3 and the second workpiece spindle 4 are measured by the touch probe 20, and during workpiece machining, the amount of deviation in the relative position between the workpiece W and the tool T is estimated based on positional deviation data, which is the amount of deviation of the measured center positions from the normal position, and the feed motor 33 is controlled to correct the estimated amount of deviation, thereby improving the machining accuracy of the workpiece W by the tool T.

[0072] In this embodiment, when the reference sphere 9a of the second work spindle 11 is measured with the touch probe 20, the measurement is performed with the second work headstock 4 moved to the position where it is to be used during workpiece machining. Therefore, the position of the second work headstock 4 can be matched when measuring the reference sphere 9a and when the workpiece is machined. Therefore, based on the position information of the measured reference sphere 9a (the amount of deviation from the center position in this example), the relative positions of the workpiece W and the tool T during workpiece machining can be corrected with high precision.

[0073] Furthermore, in this embodiment, the positional deviation data (i.e., the amount of deviation in the relative position between each workpiece spindle 10, 11 and the tool spindle 7) is linearly interpolated in accordance with the tool position in the extension direction of the workpiece W, and the value is estimated as the amount of deviation in the relative position between the workpiece W and the tool T at that tool position. This makes it possible to accurately estimate the amount of deviation in the relative position between the workpiece W and the tool T. This in turn makes it possible to significantly improve the accuracy of correction of the relative position between the workpiece W and the tool T by the feed motor 33.

[0074] (Embodiment 2) Figure 9 is a diagram equivalent to Figure 7 showing embodiment 2. This embodiment differs from embodiment 1 in that positional deviation data is generated taking into account the operating state of the rotation fixing mechanism 35 of the swivel drive shaft 16, and correction control is executed based on the positional deviation data. Note that the hardware configuration of the machine tool 1 is the same as in embodiment 1, and therefore the same components are designated by the same reference numerals and detailed description thereof will be omitted.

[0075] That is, in this embodiment, when the measurement start button 61c is pressed in the positional deviation measurement mode, under the control of the drive control unit 53, the measurement operation of the reference sphere 9a of each work spindle 10, 11 is carried out using the touch probe 20 in each of the states of the coupling operation state, the brake operation state, and the fixed release state (see Figure 3) in the same procedure as in embodiment 1, and the positional deviation data is generated by the positional deviation calculation unit 71 of the measurement data processing device 70 and stored in the data memory unit 72.

[0076] 9 shows an example of positional deviation data stored in the data storage unit 72 of the measurement data processing device 70. In this positional deviation data, the positional deviation amounts are described for each of the coupling operating state, the brake operating state, and the lock release state in the same data configuration as in embodiment 1. Note that in FIG. 9, the positional deviation amounts are represented by four alphabetic characters (e.g., XaL0) for convenience, but in practice these are replaced with numerical values.

[0077] Next, the correction control of the relative position between the workpiece W and the tool T, which is executed by the drive control unit 53 of the control device 50 based on the positional deviation data in the normal operation mode, will be described.

[0078] When performing correction control, the drive control unit 53 first determines whether the current operating state of the rotation locking mechanism 35 (coupling mechanism 30 and electromagnetic brake mechanism 32) is a front coupling operating state, a brake operating state, or a lock release state. The drive control unit 53 then extracts (specifies) the positional deviation data corresponding to the determined operating state from the positional deviation data (see FIG. 9 ) stored in the data storage unit 72, estimates the amount of deviation in the relative position between the workpiece W and the tool T based on the extracted positional deviation data, and controls the feed motor 33 to correct the estimated amount of deviation. The estimation of the amount of deviation in the relative position is performed by linearly interpolating the positional deviation data in accordance with the position of the tool T in the Z-axis direction during workpiece machining and the rotation angle θ of the tool headstock 6 about the B-axis, as in the first embodiment.

[0079] As described above, in the positional deviation measurement mode of this embodiment, the touch probe 20 measures each reference sphere 9a in each of the three operating states of the rotation locking mechanism 35 (the coupling operating state, the brake operating state, and the lock release state) to generate positional deviation data. During workpiece machining, the relative position between the workpiece W and the tool T is corrected using the positional deviation data corresponding to the current operating state of the rotation locking mechanism 35. This improves the accuracy of correction of the relative position between the workpiece W and the tool T as much as possible. Specifically, when the coupling mechanism 30 or the electromagnetic brake mechanism 32, which are components of the rotation locking mechanism 35, are activated, the fitting clearances between the components inside the machine change, causing the position of the tool headstock 6 to change, for example, as shown by the two-dot chain line in FIG. 2 . In this embodiment, the relative position between the tool T and the workpiece W can be corrected taking into account such positional changes in the tool headstock 6. This significantly improves correction accuracy compared to when the operating state of the rotation locking mechanism 35 is not taken into account.

[0080] (Other embodiments) In each of the above-described embodiments, the touch probe 20 is attached to the tool spindle 7 held by the tool headstock 6, but the present invention is not limited to this. The touch probe 20 may be attached to the turret 5a of the turret tool rest 5. In this case, the amount of deviation of the center position of each reference sphere 9a measured by the touch probe 20 corresponds to the amount of deviation in the relative position between the turret 5a and each workpiece spindle 10, 11. Therefore, during workpiece machining, the relative position between the tool 5b attached to the turret 5a and the workpiece W can be corrected by controlling the feed motor 33 to correct this amount of deviation. In this case, the turret 5a corresponds to the workpiece holder, and the turret tool rest 5 corresponds to the workpiece moving table.

[0081] In each of the above-described embodiments, the amount of deviation in the relative position between the workpiece W and the tool T is corrected by correcting the position of the tool headstock 6 using the feed motor 33, but the present invention is not limited to this and the positions of the workpiece headstocks 3 and 4 may be corrected, or the positions of both the workpiece headstocks 3 and 4 and the tool headstock 6 may be corrected. In other words, as long as the relative position between the workpiece W and the tool T can be corrected, the object to be moved by the feed motor 33 and the direction of movement are not limited.

[0082] In each of the above-described embodiments, the amount of deviation in the relative position between the workpiece W and the tool T is corrected in all directions, including the X-axis, Y-axis, and Z-axis directions, but this is not limiting. For example, the amount of deviation may be corrected in only one or two of the X-axis, Y-axis, and Z-axis directions. In this case, the measurement of the center position of each reference sphere 9a by the touch probe 20 only needs to be performed in the one or two axial directions.

[0083] In the above-described embodiments, an example has been described in which the first workpiece headstock 3 is a fixed headstock and the second workpiece headstock 4 is a movable headstock, but the present invention is not limited to this. That is, the machine tool 1 may have only one movable headstock, or both workpiece headstocks may be configured with movable headstocks. In the former case, it is sufficient to move one workpiece headstock to its intended use position and then measure the positional deviation of the reference sphere 9a. In the latter case, it is sufficient to move the two workpiece headstocks to their intended use positions and then measure the positional deviation of the reference sphere 9a. The estimation and correction processes for the positional deviation amounts between the workpiece W and the tool T may be performed in the same manner as in the above-described embodiments.

[0084] In each of the above-described embodiments, the reference sphere 9a is used as an example of a reference object attached to the first work spindle 10 and the second work spindle 11, but the present invention is not limited to this and, for example, a cubic member may be used as the reference object and the position of each surface may be measured by the touch probe 20. The reference object may also be a reference mark attached to each work spindle 10, 11. In this case, an image sensor such as a camera may be used as a measurement sensor attached to the tool spindle 7, and the amount of positional deviation of the reference mark may be measured by the image sensor, thereby calculating the amount of deviation in the relative position between each work spindle 10, 11 and the tool spindle 7.

[0085] In each of the above embodiments, an example has been described in which the measurement sensor is configured by the touch probe 20, but the present invention is not limited to this. The measurement sensor may be configured by, for example, a non-contact probe that utilizes the principle of a laser displacement meter, or may be configured by an image sensor such as a camera as described above.

[0086] In each of the above-described embodiments, the amount of deviation of the center position of the reference sphere 9a is calculated as the amount of deviation (positional deviation data) of the relative position between the tool spindle 7 and each of the work spindles 10, 11. However, this is not limited to this. For example, the work spindles 10, 11 may be rotated by 120° each time, and based on the position information of the reference sphere 9a measured at each angular position, the amount of deviation of the axial center position of each of the work spindles 10, 11 may be calculated and generated as the positional deviation data.

[0087] In the above embodiment, the machine tool 1 is a combined lathe, but is not limited thereto. For example, the machine tool 1 may be an additive machining machine that performs additive machining, or a hybrid machine that can perform both cutting and additive machining. In additive machining, for example, a supply nozzle is used instead of the tool T, and powder material supplied from the supply nozzle to the workpiece surface is melted and solidified by a laser or the like. In this case, the supply nozzle and / or laser unit functions as the workpiece that processes the workpiece. Furthermore, the amount of deviation in the relative position between the workpiece spindle and the workpiece holder may be based on the tip of the supply nozzle, the intended arrival point of the powder material supplied from the supply nozzle, or the laser irradiation point.

[0088] In the above-described embodiments, the reference object and the measurement sensor are attached before the movable work headstock is moved, but this order is not limited to this and may be reversed. Also, since the reference object and the measurement sensor have a complementary relationship, the measurement sensor may be provided on the movable work headstock and the reference object may be provided on the workpiece holder.

[0089] Furthermore, the measurement sensor is not limited to being mounted on either the movable workpiece headstock or the workpiece holder. For example, an internal camera mounted inside the machine tool or an external camera mounted on a manipulator of a robot such as an AGV that loads and unloads workpieces into and out of the machine tool may capture images of the workpiece spindle of the movable workpiece headstock and its vicinity, as well as the workpiece holder and its vicinity, and the amount of deviation in their relative positions may be calculated based on the captured images. To facilitate detection of the positions of the workpiece spindle and the workpiece holder from the captured images, for example, reference objects with predetermined markers may be attached to each, or to only one of them. Additionally, if the workpiece spindle or the workpiece holder has a marker or other feature that can be used to obtain position information, that may also be used as the reference object.

[0090] In each of the above embodiments, the amount of positional deviation between the workpiece W and the tool spindle 7 is calculated when the workpiece W is supported at both ends by the first workpiece spindle 10 and the second workpiece spindle 11. The calculated amount of positional deviation is linearly interpolated based on the position of the tool T in the workpiece extension direction (the direction in which the two workpiece spindles 10 and 11 face each other), and the resulting value is estimated as the amount of relative positional deviation between the workpiece W and the tool T at the position of the tool T. However, the interpolation method does not necessarily have to be linear. For example, if the amount of deflection of the guide rail varies nonlinearly based on the position of the second workpiece support table 4, which is a movable support table, the amount of deviation may be calculated using a nonlinear function. Furthermore, the workpiece W does not necessarily have to be supported at both ends, and may be supported in a cantilevered manner. In this case, the amount of relative positional deviation between the workpiece W and the tool T may be estimated by performing an interpolation calculation based on the position of the tool T in the workpiece extension direction based on the amount of positional deviation between the workpiece spindle supporting the workpiece and the tool spindle 7.

[0091] It should be noted that the above-described embodiments are illustrative in all respects and are not limiting. Those skilled in the art will appreciate that modifications and variations are possible. The scope of the present invention is defined not by the above-described embodiments but by the claims. Furthermore, the scope of the present invention includes modifications from the embodiments within the scope of the claims and their equivalents. [Explanation of symbols]

[0092] T Tool (workpiece) double work θ turning angle 1 Machine tools 3. First work headstock (fixed work headstock) 4. Second work headstock (movable work headstock) 6 Tool headstock (workpiece moving table) 7 Tool spindle (workpiece holding part) 9a Reference sphere (reference object) 10 First work spindle (work spindle) 11 Second work spindle (work spindle) 16 Swivel drive shaft 20 Touch probe (measurement sensor) 30 Coupling mechanism (first fixing mechanism part) 31 Swing motor (swing drive unit) 32 Electromagnetic brake mechanism (second fixing mechanism part) 33 Feed motor (feed mechanism) 35 Rotation and fixing mechanism

Claims

1. A correction method for correcting the relative position of a workpiece and a workpiece during machining in a machine tool having a movable work headstock movable in a predetermined direction, a work spindle mounted on the movable work headstock and holding a workpiece, a workpiece holder holding a workpiece for machining the workpiece, a workpiece moving table movable in a predetermined direction with the workpiece holder mounted thereon, and a feed mechanism capable of changing the relative positions of the movable work headstock and the workpiece moving table, comprising: a moving step of moving the movable work headstock to a position where it is to be used during workpiece machining by the feed mechanism before starting machining of the workpiece; a positional deviation calculation step of calculating a relative positional deviation between the workpiece holder and the workpiece spindle mounted on the movable workpiece headstock moved to the intended use position; a correction control step of estimating the amount of deviation in the relative position between the workpiece and the workpiece during workpiece machining based on the amount of deviation calculated in the position deviation calculation step, and controlling the feed mechanism unit to correct the estimated amount of deviation.

2. a mounting step of mounting a reference object to either the work spindle or the workpiece holder mounted on the movable work headstock before starting machining of the workpiece, and mounting a measurement sensor capable of measuring position information of the reference object on the other of the work spindle or the workpiece holder to which the reference object is not mounted, 2. A correction method according to claim 1, wherein in the positional deviation calculation step, the measurement sensor measures positional information of the reference object, and calculates the amount of deviation in the relative position between the work spindle and the workpiece holder based on the measured positional information.

3. 3. A correction method according to claim 2, wherein in the attaching step, the reference object is attached to the workpiece spindle mounted on the movable workpiece headstock, and the measurement sensor is attached to the workpiece holder.

4. the machine tool further comprises a fixed work headstock that is immovably fixed at a predetermined position and that holds a work spindle that is coaxially opposed to the work spindle of the movable work headstock; the attaching step further includes a step of attaching a reference object to the work spindle mounted on the fixed work headstock before starting machining of the workpiece; the positional deviation calculation step further includes a step of measuring positional information of the reference object attached to the work spindle of the fixed work headstock by the measurement sensor attached to the workpiece holder, and calculating the amount of deviation of the relative position between the work spindle of the fixed work headstock and the workpiece holder based on the measured positional information, 4. The correction method according to claim 3, wherein the correction control step estimates the amount of deviation in the relative position between the workpiece and the workpiece holder during workpiece machining based on the amount of deviation in the relative position between each workpiece spindle and the workpiece holder calculated in the position deviation calculation step, and controls the feed mechanism unit to correct the estimated amount of deviation.

5. Two movable work headstocks are provided, and the two movable work headstocks are arranged so that the work spindles mounted thereon are coaxially opposed to each other; In the attaching step, a reference object is attached to each work spindle mounted on each movable work headstock; In the moving step, each of the movable work headstocks is moved to a position where it is to be used during workpiece machining; In the positional deviation calculation step, positional information of each of the reference objects is measured by the measurement sensor attached to the workpiece holder, and based on the measured positional information of each of the reference objects, a deviation amount of a relative position between each of the workpiece spindles mounted on each of the movable workpiece headstocks and the workpiece holder is calculated; 4. The correction method according to claim 3, wherein the correction control step estimates the amount of deviation in the relative position between the workpiece and the workpiece holder during workpiece machining based on the amount of deviation in the relative position between each workpiece spindle and the workpiece holder calculated in the position deviation calculation step, and controls the feed mechanism unit to correct the estimated amount of deviation.

6. 6. The correction method according to claim 4 or 5, wherein the correction control step, during workpiece machining, estimates a value obtained by interpolating the amount of deviation in the relative position between each workpiece spindle and the workpiece holder calculated in the position deviation calculation step according to the position of the workpiece in the opposing direction of each workpiece spindle as the amount of deviation in the relative position between the workpiece and the workpiece at the position of the workpiece, and controls the feed mechanism unit to correct the estimated amount of deviation.

7. the machine tool is configured to perform machining of the workpiece using a workpiece held by the workpiece holder, with both end portions of the workpiece in an extension direction being supported by the two workpiece spindles facing each other; 6. A correction method according to claim 4 or 5, characterized in that, in the correction control step, during workpiece machining, the amount of deviation in the relative position between each workpiece spindle and the workpiece holder calculated in the position deviation calculation step is linearly interpolated depending on the position of the workpiece in the extension direction of the workpiece, and the value is estimated as the amount of deviation in the relative position between the workpiece and the workpiece at the position of the workpiece, and the feed mechanism is controlled to correct the estimated amount of deviation.

8. the machine tool comprises a swivel drive shaft connected to the workpiece moving table and rotatable about a predetermined axis, a swivel drive unit that rotationally drives the swivel drive shaft, and a rotation fixing mechanism that fixes the swivel drive shaft so that it cannot rotate; the rotation fixing mechanism has a plurality of fixing mechanism parts that can fix the revolving drive shaft so that it cannot rotate, and is configured to be switchable between a plurality of operating states in which the plurality of fixing mechanism parts are activated / deactivated in different combinations; the positional deviation calculation step is executed in each of the plurality of operating states, 2. The correction method according to claim 1, wherein the correction control step determines which of the plurality of operating states the current operating state of the rotation fixing mechanism corresponds to during workpiece machining, identifies the amount of relative positional deviation between the workpiece spindle and the workpiece holder calculated in the positional deviation calculation step that corresponds to the determined operating state, estimates the amount of relative positional deviation between the workpiece and the workpiece based on the identified amount of deviation, and controls the feed mechanism to correct the estimated amount of deviation.

9. The correction method according to claim 8, characterized in that the rotation fixing mechanism has, as the plurality of fixing mechanism parts, a first fixing mechanism part that mechanically fixes the swivel drive shaft, and a second fixing mechanism part that is an electromagnetic brake mechanism attached to the swivel drive part.

10. the machine tool includes a swivel drive shaft connected to the workpiece transfer table and rotatable about a predetermined axis, and a swivel drive unit that rotationally drives the swivel drive shaft, In the positional deviation calculation step, the angle of the workpiece moving table about the predetermined axis is changed to a plurality of predetermined angular positions by rotating the swivel drive shaft using the swivel drive unit, position information of the reference object is measured at each angular position, and an amount of deviation of the relative position between the workpiece spindle and the workpiece holder is calculated based on the measured position information; 3. The correction method according to claim 2, wherein the correction control step acquires the rotation angle of the rotation drive shaft around the predetermined axis during workpiece machining, linearly interpolates the amount of deviation at each angular position calculated in the positional deviation calculation step according to the acquired rotation angle, estimates the amount of deviation in the relative position between the workpiece and the machined body, and controls the feed mechanism unit to correct the estimated amount of deviation.

11. 2. The correction method according to claim 1, wherein the positional deviation calculation step calculates the amount of deviation in the relative position between the work spindle and the workpiece holder based on an image captured by a camera inside or outside the machine tool.

12. A machine tool having a movable work headstock movable in a predetermined direction, a work spindle mounted on said movable work headstock and holding a workpiece, a workpiece holder that holds a workpiece for machining said workpiece, a workpiece moving table that is movable in the predetermined direction while said workpiece holder is mounted thereon, and a feed mechanism that can change the relative positions of said movable work headstock and said workpiece moving table, a moving step of moving the movable work headstock to a position where it is to be used during workpiece machining by the feed mechanism before starting machining of the workpiece; a positional deviation calculation step of calculating a relative positional deviation between the workpiece holder and the workpiece spindle mounted on the movable workpiece headstock moved to the intended use position; a program execution unit configured to execute a correction control step of estimating the amount of deviation in the relative position between the workpiece and the workpiece during workpiece machining based on the amount of deviation calculated in the position deviation calculation step, and controlling the feed mechanism unit to correct the estimated amount of deviation.

13. A program used in a machine tool having a movable work headstock movable in a predetermined direction, a work spindle mounted on the movable work headstock and holding a workpiece, a workpiece holder that holds a workpiece for machining the workpiece, a workpiece moving table that is movable in a predetermined direction while the workpiece holder is mounted thereon, and a feed mechanism that can change the relative positions of the movable work headstock and the workpiece moving table, a moving step of moving the movable work headstock to a position where it is to be used during workpiece machining by the feed mechanism before starting machining of the workpiece; a positional deviation calculation step of calculating a relative positional deviation between the workpiece holder and the workpiece spindle mounted on the movable workpiece headstock moved to the intended use position; A program for a machine tool, characterized by causing a computer to function as a correction unit configured to execute a correction control process in which, based on the amount of deviation calculated in the positional deviation calculation process, an amount of deviation in the relative position between the workpiece and the workpiece during workpiece machining is estimated, and the feed mechanism unit is controlled to correct the estimated amount of deviation.

Images