JP2002120127A - Tool position correction method on numerical control lathe and control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve working precision on an NC lathe by properly and automatically correcting positional slippage of a tool installed on a tool rest caused by motion of a tool rest driving mechanism at the time of controlling working motion. SOLUTION: The tool 22-1 to be used for working is fixed on a second tool rest 20 in a position at the time of working. In this state, the second tool rest 20 is arranged at a position P1 under control of an NC device, and a first coordinate Q1 (x1, z1) of a tool knife edge is found by the position P1. Thereafter, the second tool rest 20 is moved to a position P2 from the position P1 in a direction of a logical control axis β, and a second coordinate Q2 (x2, z2) of the tool knife edge is found by the position P2. The NC device finds a rate of change Δx/Δz=(x2-x1)/(z2-z1) of an actual moving axis α at the time of the second tool rest 20 moving in the direction of the logical control axis βfrom the first and second coordinates Q1, Q2 of the fool knife edge and forms a computing expression Xc=(Δx/Δz)×Zp to correct a tool moving position (Xp, Zp) concerning the tool 22-1 designated by a working program.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for correcting a tool position in a numerically controlled lathe. Furthermore, the present invention relates to a control device for performing a tool position correcting method on a numerically controlled lathe.

[0002]

2. Description of the Related Art In recent years, in the field of automatic lathes (ie, lathes capable of automatic machining) represented by numerically controlled lathes (hereinafter referred to as NC lathes), bar-shaped workpieces (hereinafter, referred to as bar materials) are used. Equipped with various types of tools, including rotating tools, on the turret to enable machining of workpieces with more complex shapes, enabling various automatic machining operations such as milling in addition to turning. Combined mechanization is in progress.
Furthermore, in order to shorten the processing time, at least one main spindle and at least one tool post, each of which can operate along different control axes, are collectively mounted on one lathe machine base, and the same bar material is mounted. Various multi-function NC lathes have been proposed which enable simultaneous processing of different types (for example, outer diameter cutting and boring) and simultaneous processing of different bars.

[0003] In this type of NC lathe, in order to realize high-precision automatic machining, a high-precision guide is provided to a drive mechanism for feeding a spindle or a tool post along a given control axis on the lathe machine base. / It is required to provide a positioning function. The guiding accuracy and positioning accuracy of the driving mechanism include not only the operating accuracy of a driving source (for example, an AC servomotor), but also the dimensional accuracy and assembly of components such as a guide member (for example, a slide guide) and a feed screw device (for example, a ball screw). It depends on mechanical structural accuracy such as accuracy and rigidity.

Here, in a conventional NC lathe, a tool post includes a control axis (generally referred to as a Z axis) parallel to a rotation axis of a main shaft for gripping a bar, and one or two control axes orthogonal to the control axis. Configurations are known that move along a control axis (generally referred to as the X or Y axis). In this configuration, the tool mounted on the tool rest moves the tool rest to various positions along the Z-axis, thereby bringing the cutting edge into contact with a desired portion in the longitudinal direction of the bar to be machined. The longer the is, the more the guide / positioning accuracy of the Z-axis drive mechanism of the tool rest has an influence on the machining accuracy. For example, when the actual Z-axis guide direction of the tool rest is slightly inclined with respect to the normal (theoretical) Z-axis parallel to the spindle rotation axis due to the lack of the guide / positioning accuracy of the Z-axis drive mechanism. Is that even if the tool is first accurately aligned at the coordinate system origin, the tool tip moves along the Z-axis from the regular path parallel to the Z-axis as the tool post moves in the Z-axis direction. There is a tendency that the displacement gradually becomes large in the direction orthogonal to. Therefore, it is necessary to improve the operation accuracy and mechanical structure accuracy of the Z-axis drive mechanism as much as possible, especially for a tool rest that can move in the Z-axis.

[0005] On the other hand, in a conventional NC lathe, a main (or front) main spindle that grips and rotates a bar supplied from outside the lathe, and a rotation axis parallel to the rotation axis of the first main spindle. The auxiliary (or rear side) second member which can be disposed coaxially in front of the first main shaft in the axial direction and coaxially opposed thereto, and grips and rotates a partially processed bar material delivered from the first main shaft. There is known a configuration including a main shaft and a turret tool rest movable in an orthogonal coordinate system having a control axis (Z axis) parallel to the rotation axes of both main shafts and a control axis (X axis) orthogonal to the Z axis. ing.
In this configuration, the turret tool rest can hold a pair of tools in opposite directions and coaxially in a tool holding portion at a desired circumferential indexing angle position. Not only can the bars held by each of the second spindles be processed sequentially, but also the feed operations of the two spindles are performed in synchronism with the feed operation of the turret tool post itself, so that the bars held by the two spindles can be simultaneously moved. Processing can also be performed.

In the NC lathe having such a configuration, a pair of tools oriented in opposite directions at a desired tool holding portion on a turret tool post are mutually accurate due to an assembling error to the tool holding portion. Is not coaxially arranged,
As a result, the error of the actual position with respect to the designated position when each tool is moved according to the machining program may be different from each other. In such a case, when the pair of tools is used to simultaneously process the rods gripped on the first and second spindles arranged coaxially and opposed to each other,
Since both tools move in accordance with the same feed operation of the turret tool rest, there is a difference in machining accuracy between the tools. Therefore, in the above configuration, a pair of tools oriented in opposite directions to each other are coaxially arranged as accurately as possible on the tool holding portion in order to maintain a high level of machining accuracy when simultaneously machining different bar materials. Is required.

[0007]

In the above-mentioned conventional NC lathe having a tool rest capable of moving in the Z-axis, high-precision automatic machining is realized in addition to further improving the guide / positioning accuracy of the Z-axis drive mechanism. There was no effective countermeasure. However, there is a limit in improving the operation accuracy and mechanical structure accuracy of the Z-axis drive mechanism, and it is therefore difficult to reduce the error in the Z-axis feed operation to an acceptable level in precision machining on the order of μm. Was. Therefore, in the NC device incorporated in the NC lathe, it is effective to supplementally execute a tool position correction method for appropriately automatically correcting the position coordinates of the tool specified on the program before starting the machining operation control. it is conceivable that. However, conventionally known tool position correction methods include dimensional errors and assembling errors of the tool itself, such as automatically correcting the position of the cutting edge of the tool on the tool post at a specific position with reference to the center axis of the bar to be processed. It is a method of correcting the misalignment of the cutting edge due to, it is difficult to apply to automatically correct the misalignment of the cutting edge of the tool post mounting tool caused by the error of the feed operation of the tool post drive mechanism. there were.

In addition, the above-mentioned conventional technique can simultaneously process the rods gripped on the first and second spindles which are coaxially arranged and opposed by using a pair of tools oriented in opposite directions on the turret tool rest. In the NC lathe, there was no effective countermeasure for realizing high-precision simultaneous machining of both bars, in addition to further improving the assembling accuracy of each tool to the tool holding portion of the turret tool post. However, there is a limit in improving the accuracy of assembling each tool to the tool holding portion. Therefore, it has been difficult to reduce the misalignment of both tools to an acceptable degree in precision machining on the order of μm. Therefore, conventionally, the turret tool post feed is performed while automatically correcting the position of the tool so that only a predetermined one of a pair of tools oriented in opposite directions can be maintained at a desired level. The operation was controlled. However, such a method cannot flexibly cope with fluctuations in the level of machining accuracy required in a simultaneous machining process on a pair of bars, and only the machining accuracy with the first set tool is always available. There was a problem that the desired level was set.

Accordingly, an object of the present invention is a tool position correcting method for an NC lathe having a tool rest movable along a plurality of control axes orthogonal to each other on a lathe machine base,
A tool that can automatically correct the displacement of the cutting edge of the tool rest mounted tool caused by the operation of the tool rest drive mechanism when controlling the machining operation, thereby realizing high-precision automatic machining in the NC lathe. It is to provide a position correction method.

Another object of the present invention is to provide a lathe machine comprising a first and a second spindle which can be coaxially opposed to each other, and a tool rest which can be moved along a plurality of control axes orthogonal to each other. A tool position correcting method for an NC lathe having a tool holding portion on a tool post and capable of simultaneously processing bars gripped on both main spindles by a pair of tools held in a desired tool holding portion on a tool rest in a direction opposite to each other. In order to flexibly cope with fluctuations in the level of machining accuracy required in a simultaneous machining process on a pair of bars, each machining tool is controlled so that the machining accuracy of both tools is set to a desired level. It is an object of the present invention to provide a tool position correcting method which can automatically correct the position of the tool as needed.

Still another object of the present invention is to provide a control device for performing the above-described tool position correcting method on an NC lathe.

[0012]

According to one aspect of the present invention, there is provided a numerical tool having a tool post movable on a lathe machine along a plurality of theoretical control axes orthogonal to each other. In a control lathe, a tool position correction method for automatically correcting a positional shift of a cutting edge of a mounted tool caused by movement of the tool post, wherein a tool used for processing is fixed to the tool post in a posture at the time of processing. Mounting, the tool rest is arranged at a first position on the lathe machine base, and at the first position, a first coordinate of a cutting edge of the tool is converted into an orthogonal coordinate system having the plurality of theoretical control axes. The tool post is moved from the first position to the second position in the axial direction of one theoretical control axis on the lathe machine base at the second position, and at the second position, the cutting edge of the tool is A second coordinate is obtained in the orthogonal coordinate system, and the second coordinate of the cutting edge of the tool is obtained. From the coordinates and the second coordinates, when the tool post moves in the axial direction of the one theoretical control axis, a change rate of an actual movement axis with respect to the theoretical control axis is determined, and the change rate is specified by a machining program. Calculating a correction amount for the tool movement position from the coordinate value of the tool movement position on the tool on the one theoretical control axis and the change rate;
A tool position correction method is provided, wherein the tool movement position is corrected according to the correction amount.

According to a second aspect of the present invention, there is provided a tool position correcting method according to the first aspect, wherein the one theoretical control axis extends in parallel to a rotation axis of a main shaft of the numerical control lathe. provide.

According to a third aspect of the present invention, there is provided the first or second aspect.
A control device for performing the tool position correction method according to the above, wherein a calculation formula for calculating the correction amount is created and stored from the first coordinates and the second coordinates of the cutting edge of the tool. And correcting the tool movement position specified by the input machining program according to the correction amount calculated from the calculation formula, and controlling the movement of the tool post based on the corrected tool movement position. A control device characterized by the following.

According to a fourth aspect of the present invention, there are provided a first main shaft and a second main shaft which have rotational axes parallel to each other and which can be coaxially arranged, and which are parallel to the rotational axes of the first and second main shafts. A tool rest movable along a theoretical control axis, and a pair of tools mounted on the tool rest in opposite directions along the theoretical control axis to each of the first and second spindles. A numerically controlled lathe configured to simultaneously process different gripped bars, a tool position correcting method for automatically correcting a moving position of the tool post in a simultaneous processing step by the pair of tools, comprising: The pair of tools used for processing are fixedly mounted on the tool post in a posture at the time of processing, and for each of the pair of tools mounted on the tool post, the actual position with respect to the tool position specified by a processing program. Find the error, A correction ratio that relatively represents a degree of correcting the error with respect to the error calculated in relation to the error, calculating an optimum correction amount for the error based on the correction ratio, and setting the tool post according to the optimum correction amount. And a tool position correcting method for correcting the moving position of the tool.

According to a fifth aspect of the present invention, there is provided a control device for performing the tool position correcting method according to the fourth aspect, wherein a calculation formula for calculating the optimum correction amount is stored and input. Correcting the tool movement positions of the pair of tools specified by the processed machining program according to the optimum correction amount calculated from the calculation formula, and controlling the movement of the tool post based on the corrected tool movement positions. A control device is provided.

[0017]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the drawings, the same or similar components are denoted by common reference numerals. First, an overall configuration of a numerical control (NC) lathe 10 in which a tool position correcting method according to the present invention can be conveniently implemented will be outlined with reference to FIG. The NC lathe 10 has two spindles 14 and 16 and two tool rests 18 and 20 collectively mounted on one lathe machine base 12 and includes turning tools such as cutting tools and drills and rotating tools such as milling tools. It has a multifunctional structure that enables simultaneous processing of different types (for example, outer diameter cutting and boring) of the same bar and simultaneous processing of different bars by various tools 22.

That is, the NC lathe 10 is a lathe machine 12
A first spindle 14 installed on the lathe base 12 and having a rotation axis 14a; a first tool rest 18 installed on the lathe base 12 and capable of holding a plurality of tools 22 in a parallel arrangement; A second tool rest 20 capable of holding a plurality of tools 22 in a parallel arrangement in each of a first row and a second row each having a different cutting edge orientation, and being installed on a lathe machine base 12; A second main shaft 16 having a rotation axis 16 a parallel to the rotation axis 14 a of the first main shaft 14 and capable of being arranged opposite to the first main shaft 14 is provided.

The lathe machine 12 has an inclined guide surface 1 on the front of the machine.
2a having a so-called slant bed structure,
The main shaft 14, the second main shaft 16, the first tool rest 18, and the second tool rest 20 are independently slidably supported in three orthogonal coordinate systems based on the inclined guide surface 12a.
The lathe machine 12 further includes a control (NC) device 2 described later.
An operation panel 26 for operating the operation panel 4 is mounted.

The first main spindle 14 is a main (or front) main spindle which grips and rotates a bar supplied from outside the lathe, and is rotatable on the first headstock 28 via a bearing device (not shown). Built in. The first headstock 28 is used for the lathe machine 12
Is slidably mounted on the first spindle mounting portion 30 set at one end in the longitudinal direction. The first spindle mounting section 30 has a first
The headstock 28 is connected to a feed control axis (Z) parallel to the inclined guide surface 12a and the rotation axis 14a of the first spindle 14 in an orthogonal three-axis coordinate system based on the inclined guide surface 12a of the lathe machine base 12.
A first spindle drive mechanism 32 (AC servomotor, slide guide, ball screw, etc.) that moves linearly along one axis is installed. The first headstock 28 further includes a first headstock 28.
For example, a built-in AC servomotor is built in as a rotation drive source 34 (FIG. 2) for driving the main shaft 14 to rotate. Therefore, the first spindle 14 is provided with the first spindle drive mechanism 32
By this operation, the first headstock 28 can be linearly reciprocated together with the first headstock 28 along the feed control axis (Z1 axis) parallel to its own rotation axis 14a.

At the approximate center of the lathe machine base 12 in the longitudinal direction, a first
A column 36 is erected adjacent to the spindle mount 30. The column 36 is provided with a guide as an auxiliary support device for supporting the bar gripped by the first spindle 14 at a predetermined position separated from the first headstock 28 in the axial direction forward in the vicinity of the processed portion at the tip thereof. A bush 38 is installed. The guide bush 38 is coaxially arranged with respect to the first main shaft 14, and centers and supports the bar material during the turning process so that the processed portion does not run out.

The first tool post 18 is placed on the lathe
It is movably mounted on the front surface of a column 36 functioning as a tool rest mounting portion, and is retracted and disposed on the side of a guide bush 38 located in front of the first main shaft 14 in the axial direction. In the column 36, the first tool rest 18 is provided with the inclined guide surface 12a and the rotation axis 14a of the first main shaft 14 (that is, the Z1 axis) in an orthogonal three-axis coordinate system based on the inclined guide surface 12a of the lathe machine base 12. Feed control axis perpendicular to the axis (referred to as X1 axis)
And a feed control axis (Y) orthogonal to both the Z1 axis and the X1 axis.
The first tool post drive mechanism 40 (to be referred to as one axis) moves linearly along the axis (each AC servomotor for X1-axis drive and Y1-axis drive, slide guide, ball screw, etc.)
Is installed.

The first tool rest 18 is a so-called comb tool rest for holding a plurality of tools 22 in a parallel arrangement.
A turning tool such as a drill or a rotating tool such as a milling tool is moved along an imaginary plane parallel to the front surface of the column 36 and the first spindle 1
4 can be installed in an arrangement that can be radially positioned with respect to the rotation axis 14a. In the illustrated example, the first tool rest 18 is a first tool rest that can hold a plurality of tools 22 arranged in parallel in the Y1 axis direction.
In the vicinity of the holding part 42 and the first holding part 42, a plurality of tools 2
2 which can hold the two in parallel in the X1 axis direction
4.

Therefore, the first tool rest 18 is provided with the Y1
The cutting edge of the desired tool 22 indexed and selected from the first holding unit 42 by the axis movement is moved to the X1 axis of the first tool rest 18 itself according to the machining program input to the NC device 24 and the first spindle 14 described above. The interpolation operation can be performed in cooperation with the Z1-axis movement. Similarly, the first tool rest 18 changes the cutting edge of the desired tool 22 indexed and selected from the second holding unit 44 by the X1-axis movement of the first tool rest 18 itself according to the machining program input to the NC device 24. The interpolation operation can be performed by the cooperation of the Y1 axis movement and the Z1 axis movement of the first spindle 14. Further, the first tool rest 18 is configured to move the cutting edge of the rotary tool 22 </ b> R mounted on the second holding portion 44 to the NC device 2.
The interpolation operation can be performed by the cooperation of the X1-axis movement and the Y1-axis movement of the first tool rest 18 itself in accordance with the machining program input to 4. In this manner, under the control of the NC device 24, the bar held by the first main shaft 14 can be processed into a desired shape by the desired tool 22 on the first tool rest 18.

The second tool rest 20 is movably mounted on a second tool rest mounting part 46 set on the lathe machine base 12 on the opposite side of the first spindle mounting part 30 across the column 36. Second
The second tool post 20 and the lathe machine 1
A feed control axis (referred to as an X2 axis) that is parallel to the inclined guide surface 12a and orthogonal to the rotation axis 14a of the first spindle 14 (that is, the Z1 axis) in an orthogonal two-axis coordinate system based on the second inclined guide surface 12a. And a feed control axis (Z
A second tool post drive mechanism 48 (each of an AC servomotor for X2-axis drive and Z2-axis drive, a slide guide, a ball screw, etc.) for linearly moving along each of the two axes is installed.

The second tool rest 20 is capable of holding a plurality of tools 22 in a comb-like manner in first and second rows having different cutting edge directions. Is rotated along an imaginary plane parallel to the inclined guide surface 12a of the lathe machine 12 and the first spindle 14
Can be provided in an arrangement that can be positioned parallel or coaxially with respect to the rotation axis 14a. In the illustrated example, the second tool post 20
The first holding unit 50 is capable of holding a plurality of tools 22 in a first row by orienting the plurality of tools 22 so as to face a column 36 on which the first tool rest 16 is mounted, and arranging the tools 22 in parallel in the X2 axis direction.
(FIG. 3) and a plurality of tools 2 on the opposite side of the first holding portion 50.
2 is oriented in the opposite direction and coaxially at the same position as the plurality of tools 22 mounted on the first holding unit 50, and the second
And a second holding portion 52 (FIG. 3) that can be held in a row. The first row of tools 22 mounted on the first holding portion 50 of the second tool rest 20 has a cutting edge direction for processing the bar material gripped by the first main shaft 14. The second tool post 2
0 of the second row of tools 22 mounted on the second holding portion 52,
It has a cutting edge direction for processing the bar material gripped by the second main shaft 16.

Therefore, the second tool rest 20 changes the cutting edge of the desired tool 22 indexed and selected from the first holding unit 50 by the X2-axis movement of the second tool rest 20 in accordance with the machining program input to the NC device 24. The cooperation between the X2-axis movement and the Z2-axis movement of the tool rest 20 itself can perform an interpolation operation, and the Z-axis movement of the second tool rest 20 itself can be performed in accordance with the machining program input to the NC device 24. 1 spindle 14
Can be operated by being superimposed on the Z1 axis movement. In this manner, the bar gripped by the first main shaft 14 is
A desired shape can be machined by a desired tool 22 selected from the first row on the tool rest 20.

The second spindle 16 is provided on the lathe machine base 12 on the opposite side of the first spindle mount 30 with the column 36 interposed therebetween, and the second spindle mount is set adjacent to the second tool rest mount 46. 54
Movably mounted on the rotating shaft 14a of the first spindle 14.
The first main shaft 14, that is, the guide bush 38, is disposed coaxially and opposingly in front of the guide bush 38 in the axial direction. The second main shaft 16 is an auxiliary (or rear-side) main shaft that grips and rotates a partially processed bar material delivered from the first main shaft 14, and is a second main shaft via a bearing device (not shown). The headstock 56 is rotatably built in.

The second spindle mounting portion 54 includes the second spindle 16
Is a feed control axis (referred to as an X3 axis) parallel to the X2 axis, which is one feed control axis of the second tool post 20, in an orthogonal two-axis coordinate system based on the inclined guide surface 12a of the lathe machine base 12.
And a second spindle drive mechanism 58 (X3-axis drive and Z-axis drive) for linearly moving along a feed control axis (referred to as Z3 axis) parallel to the Z1 axis which is the feed control axis of the first spindle 14.
Each AC servo motor for driving three axes, a slide guide, a ball screw, etc.) are installed. The second headstock 56 further incorporates, for example, a built-in AC servomotor as a rotation drive source 60 (FIG. 2) for rotating the second spindle 16. Therefore, the second spindle 16 is
By the operation of the spindle drive mechanism 58, it is possible to perform a linear reciprocating operation together with the second headstock 56 along each of the X3 axis and the Z3 axis.

As described above, the second spindle 16 is connected to the second tool rest 2.
It is possible to move linearly along a feed control axis (X3 axis) parallel to the X2 axis, which is one feed control axis of zero. Therefore, the second
The tool rest 20 moves the second holding unit 5 by at least one of the X2 axis movement of itself and the X3 axis movement of the second main shaft 16.
2, a desired tool 22 can be indexed and selected from the tools 22 in the second row. Then, the second tool rest 20 relatively moves the cutting edge of the selected desired tool 22 by the cooperation of the X3-axis movement and the Z3-axis movement of the second spindle 16 according to the machining program input to the NC device 24. An interpolation operation can be performed, and the Z3 axis movement of the second spindle 16 can be superimposed on the Z2 axis movement of the second tool post 20 itself in accordance with the machining program input to the NC device 24, and the operation can be performed. The X3 axis movement of the second spindle 16 can be operated by being superimposed on the X2 axis movement of the second tool rest 20 itself. In this way, the bar material gripped by the second spindle 16 is
A desired shape can be machined by a desired tool 22 selected from the second row on the tool rest 20.

Under the control of the NC device 24, the NC lathe 10 simultaneously uses a maximum of three tools 22 selected on the two tool rests 18 and 20 having the above-described configuration, and uses the front side and the rear side. The bars held by the main spindles 14 and 16 can be automatically machined respectively, and in particular, they are configured to simultaneously perform a unique interpolation operation commanded to each of the three tools 22.

FIG. 2 shows the configuration of the NC unit 24 for performing such various automatic machining. NC device 24
Includes an input unit 100, a display unit 102, an arithmetic control unit 104, and a servo control unit 106. The input unit 100 is provided with a keyboard 108 with numerical keys installed on the operation panel 26.
1 (FIG. 1), and data (tool selection, article shape, dimensions, and the like) necessary to control the operations of the first and second spindles 14 and 16 and the first and second tool rests 18 and 20.
A machining program (that is, a block sequence) relating to each tool 22 including a spindle speed, a tool feed speed, and the like is input from the input unit 100. The display unit 102 operates the operation panel 26.
Has a display screen 110 (FIG. 1) such as a CRT (cathode ray tube) or an LCD (liquid crystal display) installed in the display unit. The processing program input by the input unit 100 is displayed on the display screen 110, and the display screen is displayed in an interactive manner. For example, automatic programming while simulating on the 110 is enabled.

The arithmetic and control unit 104 stores the R
AM (random access memory) 112 and ROM (read only memory) 114, and CP constituting a processing unit
U (central processing unit) 116. A plurality of machining programs related to a plurality of tools 22 including various data input by the input unit 100 are stored in a RA
It is stored in M112 or ROM114. Also, ROM
A control program for driving the first and second spindles 14 and 16 and the first and second tool rests 18 and 20 is stored in the 114 in advance. The CPU 116 controls the RAM 11
2 or machining program and RO stored in ROM 114
A control command is output to the servo control unit 106 based on the control program stored in M114.

The servo control unit 106 includes a first spindle movement control unit 118, a first spindle rotation control unit 120, a first tool rest movement control unit 122, a second tool rest movement control unit 124, and a second spindle movement control unit 126. And a second spindle rotation control unit 128. The first spindle movement control unit 118 operates the first spindle drive mechanism 32 based on a command from the CPU 116 to move the first spindle 14 together with the first headstock 28 in the Z1 axis. The first spindle rotation control unit 120, based on a command from the CPU 116,
By operating the rotation drive source 34, the first spindle 14 is indexed and rotated within the first headstock 28. The high-speed rotation of the first spindle 14 during turning is based on data such as the number of rotations.
It is controlled via another control circuit (not shown).

The first tool post movement control unit 122 includes a CPU 1
The first tool post drive mechanism 40 is operated based on the instruction 16 to move the first tool post 18 in the X1-axis or Y1-axis. The second tool post movement control unit 124 operates the second tool post drive mechanism 48 based on a command from the CPU 116 to
The tool post 20 is interpolated by Z2 axis movement and X2 axis movement.

The second spindle movement control unit 126 is a CPU
6 to operate the second spindle drive mechanism 58,
The second spindle 16 is interpolated by Z3 axis movement and X3 axis movement. The second spindle rotation control unit 128 operates the rotation drive source 60 based on a command from the CPU 116 to
Is indexed and rotated in the second headstock 56. The high-speed rotation of the second spindle 16 during the turning process is controlled via another control circuit (not shown) based on data such as the number of rotations.

In the above control system, the NC unit 24
The first spindle drive mechanism 32, the first tool post drive mechanism 40,
The second tool post drive mechanism 48 and the second spindle drive mechanism 58
By controlling in association with each other, the first tool post 18
Associated with the first spindle 14 by the desired tool 22 selected at (i.e., relative to the bar gripped by the first spindle 14).
A machining step, a machining step related to the first spindle 14 by a desired tool 22 selected from the first row at the second tool rest 20, and a desired tool 22 selected from the second row at the second tool rest 20 And (i.e., for the bar held by the second spindle 16) with respect to the second spindle 16. Further, the NC device 24 performs the above-described interpolation operation of the tool 22 selected by the first tool post 18, the above-described interpolation operation of the tool 22 selected from the first row by the second tool post 20,
The first spindle drive mechanism 32, the first tool post drive mechanism 40, and the second tool post drive mechanism 48 so that the above-described interpolation operation of the tool 22 selected from the second row can be simultaneously performed by the second tool post 20. In addition, the second spindle drive mechanism 58 can be appropriately controlled to overlap.

As described above, the NC lathe 10 has a feed control axis (Z2 axis) parallel to the rotation axis 14a of the first main shaft 14.
And a second tool rest 20 that moves along a feed control axis (X2 axis) orthogonal to the Z2 axis. In this configuration, the tool 22 mounted on each of the first holding portion 50 and the second holding portion 52 of the second tool rest 20 moves the second tool rest 20 to Z2.
By moving to various positions along the axis,
The cutting edge is brought into contact with a desired portion in the longitudinal direction of a different bar to be machined gripped by each of the main shaft 14 and the second main shaft 16. Therefore, in this configuration, the longer the finished workpiece is, the more the guide / positioning accuracy of the second turret drive mechanism 48, particularly the Z2-axis direction driving structure, exerts on the machining accuracy. For example, as shown in FIG.
When trying to move in the axial direction, the actual Z2-axis guide direction of the second tool post 20, that is, the moving axis α, due to lack of guidance / positioning accuracy of the second tool post drive mechanism 48 (FIG. 1).
(Shown by a solid line in FIG. 3B) is the first spindle rotation axis 14.
The normal Z2 axis parallel to a, that is, the theoretical control axis β (FIG.
(Indicated by a dashed line in (b)), the second tool rest 20 moves in the Z2-axis direction even if the tool 22 is first accurately positioned at the coordinate system origin position. Accordingly, the path of the cutting edge of the tool 22 tends to gradually deviate from a normal path parallel to the Z2 axis in a direction orthogonal to the Z2 axis.

A first tool position correcting method according to the present invention comprises:
The misalignment of the cutting edge of the tool rest mounting tool 22 caused by the feed operation of the second tool rest driving mechanism 48 is determined by the second
The present invention can be advantageously applied in order to reduce to a level acceptable in precision machining of, for example, μm, which cannot be achieved only by improving the operation accuracy and mechanical structure accuracy of the tool post drive mechanism 48. Hereinafter, a preferred embodiment of the tool position correcting method will be described with reference to FIG. In the following description, the second tool post 20
A tool position correction procedure when a tool (for example, a drill) 22-1 for drilling a bar end face is mounted on the first holding portion 50 of FIG.
It will be understood that tool position correction can be performed in a similar procedure.

First, as shown in FIG. 3A, a tool 22-1 used for machining is fixedly mounted on the first holding portion 50 of the second tool rest 20 in a posture at the time of machining. In that state,
The tool rest 20 is arranged at a first position P1 on the lathe machine 12 (FIG. 1) under the control of the NC device 24 (FIG. 2), and at this first position P1, the cutting edge of the cutting edge of the tool 22-1 is moved. One coordinate Q1 (x
1, z1) is obtained in a rectangular coordinate system having an X2 axis and a Z2 axis. Next, the second tool rest 20 is moved to the NC device 24.
Under the control of the normal Z parallel to the first spindle rotation axis 14a.
It moves from the first position P1 to the second position P2 on the lathe machine base 12 in the two-axis direction, that is, the direction of the theoretical control axis β (FIG. 3).
(B)) At this second position P2, the second coordinates Q2 (x2, z2) of the cutting edge of the tool 22-1 are obtained in the above-described orthogonal coordinate system. These first and second coordinates Q1 and Q2 can be obtained by actual measurement using a measuring instrument (not shown) attached to the lathe machine base 12, for example. The first and second coordinates Q1 and Q2 obtained in this manner are immediately stored in the RAM 112 (FIG. 2) of the NC device 24.

Next, the CPU 116 (FIG. 2) of the NC unit 24 checks the first coordinates Q1 (x1, z) of the cutting edge of the tool 22-1.
1) and the second coordinates Q2 (x2, z2), the rate of change 実 際 of the actual movement axis α with respect to the Z2 axis when the second tool rest 20 moves in the normal Z2 axis (theoretical control axis β) direction. x / △ z
= (X2-x1) / (z2-z1)
Tool 2 on second turret 20 specified by machining program
Formula Xc = (△ x / △ z) × Zp for calculating a correction amount for correcting the tool movement position (Xp, Zp) relating to 2-1 is created. Here, Zp is the designated coordinate value on the Z2 axis of the tool movement position in the machining program, and therefore, the correction amount Xc is the designated coordinate value X on the X2 axis of the tool movement position.
p, that is, the tool 22 on the second tool post 20
This is a correction amount for canceling the position shift of −1 in the X2 axis direction. The calculation formula of the correction amount Xc thus created is immediately stored in the RAM 112 of the NC device 24.

Thereafter, when the machining process is executed, the CPU 116 of the NC unit 24 determines all the tool movement positions of the tool 22-1 on the second tool rest 20 specified by the machining program input and stored in the RAM 112. (Xpn, Z
pn), the stored formula Xcn = (△ x / △ z)
A correction amount is calculated using × Zpn, and these tool movement positions are automatically corrected. Therefore, the tool movement position automatically corrected is (Xpn-Xcn, Zpn). Then, when the second tool rest movement control unit 126 (FIG. 2) operates the second tool rest driving mechanism 48 in accordance with the command of the tool movement position automatically corrected, the second tool rest 20 is moved to the second tool rest 20.
The tool 22-1 moves while automatically canceling the positional deviation caused by the lack of the operation accuracy and the mechanical structure accuracy of the tool rest driving mechanism 48, and accurately positions the tool 22-1 at the specified position. As a result, the tool 22-1 attached to the first holding portion 50 of the second tool rest 20 can perform desired processing on the bar with high accuracy.

As described above, according to the above-described tool position correcting method, the processing program is executed without considering at what position on the X2 axis the second tool rest 20 is to be processed. Prior to execution, the Z of the second turret drive mechanism 48
The displacement of the cutting edge of the tool 22 on the second tool post 20 caused by the two-axis feed operation is measured in advance and input to the NC device 24, and such a displacement is automatically corrected as needed in controlling the machining operation. can do. Therefore, NC
In the lathe 10, a tool on the second turret 20 at a level that can be achieved only by improving the operation accuracy and mechanical structural accuracy of the second turret drive mechanism 48 and that can be tolerated by precision machining on the order of μm, for example. 22 can realize high-precision automatic machining.

In the above-described tool position correcting method, the first position P1 of the second tool rest 20 and the first position P1 of the second tool rest 20 for obtaining the rate of change △ x / △ z of the movement axis α of the second tool rest 20 with respect to the Z2 axis. The position P2 of the second position is desirably the two ends of the Z2-axis feed stroke by the second tool rest driving mechanism 48 from the viewpoint of improving the reliability of the change rate Δx / Δz. Alternatively, the coordinates of the cutting edge of the tool 22-1 may be determined at three or more positions, and the rate of change may be determined from these coordinates by curve approximation to create a secondary or tertiary calculation formula.
Further, the above-described first position P1 of the second tool rest 20 is
Although the position where the cutting edge of the tool 22-1 is arranged on the first spindle rotation axis 14a is illustrated, the position is not limited to this, and another position can be selected within a range where measurement by a measuring instrument is possible.

Further, according to the above-described tool position correcting method, all the tools 22 mounted on the first and second holding portions 50 and 52 of the second tool rest 20 are prepared for calculating the correction amounts. By using the above two formulas, it is also possible to automatically correct all the tool movement positions specified by the machining program. However, in this case, the rotation axis 14 of the first spindle 14 is
It is assumed that the machining process is performed in a state where a and the rotation axis 16a of the second main shaft 16 are coaxially arranged.

Further, the above-described tool position correcting method can be applied to correct the displacement of the blade edge of the tool rest mounted tool caused by the operation of the X2-axis driving structure of the second tool rest driving mechanism 48. it can. Alternatively, the present invention can be applied to an X1-axis driving structure and a Y1-axis driving structure of the first tool post driving mechanism 40 in the NC lathe 10.

In the above embodiment, the lack of mechanical structural accuracy of the second turret drive mechanism 48 is caused by the second turret 20
When moving in the two-axis direction, the displacement of the tool
The displacement does not always occur only in the axial direction, and a three-dimensional displacement may occur in a direction deviating from the X2 · Z2 plane. In such a case, the above-described tool position correction method corrects only the X2 axis direction component of the actual displacement of the tool edge. In contrast, the X axis, Y
In a tool rest having a configuration movable in three orthogonal directions of the axis and the Z axis, a calculation formula for obtaining the correction amount Yc in the Y axis direction can be created in the same manner as the above procedure. Using the correction amounts Xc and Yc, the X and Y coordinates of the tool movement position specified by the machining program can be automatically corrected. As a result, a three-dimensional displacement of the tool edge can be accurately corrected.

By the way, as described above, the NC lathe 10
The second tool post 20 has first and second holding portions 50, 5
2, at least a pair of tools 22 can be mounted in a direction opposite to each other and coaxially along the Z2 axis. Then, the second tool rest 20 synchronizes with the feed operation of the
The first and second spindles 14, 16 are rotated by using the pair of tools 22, which are mounted oppositely and coaxially at corresponding positions, by appropriately feeding the second spindles 14, 16.
It is possible to carry out the simultaneous processing of the different rods gripped by the respective members. In this configuration, the second tool post 20
The pair of tools 22 oriented in opposite directions at the corresponding positions above are not accurately coaxially arranged due to an assembly error or the like to the first and second holding portions 50 and 52, and as a result, The error in the X2 axis direction of the actual position with respect to the designated position when each tool 22 is moved according to the machining program may be different from each other. In such a case, when the pair of tools 22 is used to simultaneously machine the rods gripped on the first and second spindles 14 and 16 coaxially opposed to each other, the two tools 22 use the second tool post. Since the movement is performed in accordance with the same feed operation of the tool 20, a difference occurs in the processing accuracy of the tools 22.

The second tool position correcting method according to the present invention comprises:
When a pair of tools 22 held in opposite directions at the corresponding positions on the second tool rest 20 are displaced in the X2 axis direction, the machining accuracy of the two tools 22 is set to a desired level. In order to be able to carry out the simultaneous processing in the state set as described above, the method can be advantageously applied. Less than,
A preferred embodiment of the tool position correcting method will be described with reference to FIGS. In the following description, the first and second holding portions 5 of the second tool rest 20 will be described in order to facilitate understanding.
Tool (for example, drill) 2 for drilling the bar end face at 0 and 52
The procedure for correcting the tool position when the 2-1 and 22-2 are mounted is illustrated and described. However, it is understood that the tool position can be corrected in the same procedure for other turning tools such as a cutting tool. Like.

First, as shown in FIG. 4, the first and second spindles 14 and 16 are coaxially opposed to each other to grip the rods W and W ', respectively.
2-1 and 22-2 are fixedly mounted on the first and second holding portions 50 and 52 of the second tool rest 20, respectively, in a posture at the time of machining. In this state, the second tool rest 20 is driven under the control of the NC device 24 (FIG. 2), and for example, the tools 22-1 and 22-2
-2, test drilling is performed on the axial end surfaces of the rods W and W 'in the X2 axis direction with respect to the designated position, thereby making it possible to reduce an error in the X2 axis direction with respect to the specified position for each of the tools 22-1 and 22-2. Measure and find. In the example of FIG. 5, the errors γ ₁ and γ _{2 of the} tools 22-1 and 22-2 when performing drilling at the center of the axial end surfaces of the bars W and W ′ are enlarged. Shown. In addition, instead of performing test drilling, the errors γ ₁ , γ ₂ are calculated by a conventionally known three-point contact method in which the tools 22-1 and 22-2 are brought into contact with the outer peripheral surfaces of the bars W and W ′. You can also ask. The errors γ ₁ and γ ₂ obtained in this manner are stored in the RAM of the NC unit 24.
112 (FIG. 2).

Here, when the conventional tool position correcting method is applied, the NC device 2
4 CPU 116 calculates the error γ stored in the RAM 112.
_1, only one of a predetermined one of the gamma ₂ so as to cancel 100%, of the tool specified position on the machining program X2
The axis coordinates are corrected, and the second tool post 20 is moved. On the other hand, the second tool position correcting method according to the present invention requires N
In the RAM 112 of the C device 24, each tool 22-1, 22-
The correction ratio indicating the degree of relative correction to the errors γ ₁ , γ ₂ of ₂ can be freely set and input. That is, according to the present invention, in a series of machining programs, high machining accuracy is required only for the bar W gripped by the first spindle 14 in one simultaneous machining step, and both spindles are used in another simultaneous machining step. Bars W, W gripped by 14 and 16
In the case where the same degree of processing accuracy is required for ′ ′ and further high processing accuracy is required only for the bar W ′ gripped by the second spindle 16 in other simultaneous processing steps, individual simultaneous processing In the process, a machining program can be created by appropriately designating a correction ratio for the errors γ ₁ and γ ₂ .

For example, the error γ ₂ is not considered (correction ratio 0
%) Completely offset the only error gamma ₁ (the correction ratio 100
If%) is required, on the operator processing program, the correction ratio error gamma ₁ (percentage) the Meikisuru predetermined code (for example, arguments A100), the tool 22-
It can be specified by adding it to the block that instructs 1. Also, using the same code, the errors γ ₁ and γ ₂ are equally canceled (correction ratio 50%) (for example, the argument A50 is also written), and the error γ ₁ is not considered (correction ratio 0%). error γ ₂ only fully offset (correction ratio 10
0%) (for example, the argument A0 is also described) can be specified on the machining program. That is, in this method, the error γ ₁
Can be freely specified as a percentage of 0 to 100.

On the other hand, in the RAM 112 of the NC unit 24,
Formula Xoc = Rγ _{1 for} calculating the optimum correction amount for correcting the tool movement position of the two tools 22-1 and 22-2 on the second tool post 20 specified by the machining program in the X2 axis direction.
+ (1-R) γ ₂ is stored in advance. Where R
Is the correction ratio (decimal number) specified for the error γ ₁ of the tool 22-1. Therefore, the optimum correction amount Xoc is the error γ of the two tools 22-1 and 22-2 on the second tool post 20. _1, the correction amount for canceling according to a specified percentage of the gamma _2.

Thereafter, when executing the machining step, the CPU 116 of the NC unit 24 executes the tool 22 in each simultaneous machining step in the machining program inputted and stored in the RAM 112.
A correction ratio designated for an error γ _{1 of} −1 is read from a predetermined code, and stored formula Xoc = Rγ ₁ +
(1-R) gamma ₂ calculates an optimum correction amount using the, all tools moving position for both tools 22-1 and 22-2 that are specified in the simultaneous processing step (i.e. moving position of the second tool rest 20 ) Is automatically corrected. Then, in accordance with these automatically corrected tool movement position commands, the second tool post movement control unit 126 (FIG. 2) causes the second tool post drive mechanism 4
8, the second tool rest 20 moves while automatically canceling the errors γ ₁ and γ ₂ according to the specified correction ratio, and moves the pair of tools 22-1 and 22-2 to desired positions. Position. As a result, the pair of tools 22 mounted on the first and second holding portions 50 and 52 of the second tool rest 20 in opposite directions to each other.
According to -1 and 22-2, it is possible to simultaneously perform the bar workpieces W and W 'gripped by the first and second spindles 14 and 16 with desired processing accuracy.

As described above, according to the above-described tool position correcting method, the bars W and W ′ held by the first and second spindles 14 and 16 are subjected to a plurality of simultaneous machining steps in one machining program. In the case where different machining accuracy is required at any time or a large number of parts are required to be manufactured with different machining accuracy, a pair of tools mounted on the second turret 20 in opposite directions in a flexible manner. 22 allows both bars W and W 'to be simultaneously processed with desired accuracy. When one of the bars W and W ′ is machined by one tool 22 on the second tool rest 20, the tool 22
May be specified as 100%.

Although some preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various changes and modifications can be made within the scope of the claims. is there. For example, each of the first and second tool position correcting methods according to the present invention can hold the plurality of tools described above in a first row and a second row showing different cutting edge directions in a comb-like manner. The present invention can be applied not only to the NC lathe having a table but also to an NC lathe having a turret tool rest capable of holding a pair of tools in a desired circumferential indexing angle position in opposite directions and coaxially.

[0057]

As is apparent from the above description, according to the present invention, in an NC lathe having a tool rest movable along a plurality of control axes orthogonal to each other on a lathe machine stand, a tool rest driving mechanism is provided. It is possible to automatically correct the displacement of the cutting edge of the tool rest mounted tool caused by the above operation when the machining operation is controlled, thereby realizing high-precision automatic machining in the NC lathe. .

Further, according to the present invention, there are provided a first and a second spindle which can be coaxially opposed to each other on a lathe machine base, and a tool rest which can be moved along a plurality of control axes orthogonal to each other. An NC lathe capable of simultaneously processing bars gripped on both main spindles by a pair of tools held in a desired tool holding portion on a tool rest in a direction opposite to each other.
In order to flexibly cope with fluctuations in the level of machining accuracy required in a simultaneous machining process on a pair of bars, the machining accuracy of each tool is set so that the machining accuracy of both tools is set to the desired level. The position can be automatically corrected as needed.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an N to which a tool position correcting method according to the present invention is applicable.
It is a perspective view which shows the whole structure of a C lathe.

FIG. 2 is a block diagram showing a configuration of an NC device incorporated in the NC lathe in FIG. 1;

FIGS. 3A and 3B are diagrams for explaining a procedure for implementing a first tool position correcting method according to the present invention, in which (a) a tool post is arranged at a first position, and (b) a tool post is placed in a second position; Shows the state of being arranged.

FIG. 4 is a view for explaining a procedure for implementing a second tool position correcting method according to the present invention, and shows a state in which a first main shaft and a second main shaft are coaxially opposed to each other;

FIG. 5 is a view for explaining an implementation procedure of a second tool position correcting method according to the present invention, showing an axis shift between a pair of tools.

[Explanation of symbols]

 Reference Signs List 10 NC lathe 14 First spindle 16 Second spindle 18 First turret 20 Second turret 22 Tool 24 NC device 40 First turret drive mechanism 48 Second turret drive mechanism 50 ··· First holding unit 52 ··· Second holding unit 112 ··· RAM 114 ··· ROM 116 ··· CPU

Claims (5)

[Claims] 1. A numerical control lathe having a tool rest movable along a plurality of theoretical control axes orthogonal to each other on a lathe machine stand, and automatically correcting a displacement of a cutting edge of a mounted tool caused by movement of the tool rest. A tool position correction method for performing a process, wherein a tool used for processing is fixedly mounted on the tool post in a posture at the time of processing, and the tool post is disposed at a first position on the lathe machine base. ,
In the first position, a first coordinate of a cutting edge of the tool is obtained in an orthogonal coordinate system having the plurality of theoretical control axes, and the tool rest is placed on the lathe machine in an axial direction of one theoretical control axis. Moving from the first position to the second position,
At the second position, second coordinates of the cutting edge of the tool are obtained in the rectangular coordinate system, and from the first coordinates and the second coordinates of the cutting edge of the tool,
When the tool rest moves in the axial direction of the one theoretical control axis, a change rate of an actual moving axis with respect to the theoretical control axis is determined, and the one of the tool moving positions for the tool specified by a machining program is determined. A tool position correction method, comprising: calculating a correction amount for the tool movement position from a coordinate value on a theoretical control axis and the change rate; and correcting the tool movement position according to the correction amount. 2. The tool position correcting method according to claim 1, wherein the one theoretical control axis extends parallel to a rotation axis of a main shaft of the numerically controlled lathe. 3. A control device for performing the tool position correcting method according to claim 1 or 2, wherein the correction amount is calculated from the first coordinates and the second coordinates of the cutting edge of the tool. While creating and storing a calculation formula for performing, the tool movement position specified by the input machining program is corrected according to the correction amount calculated from the calculation formula,
A control device for controlling the movement of the tool post based on the corrected tool movement position. 4. A first main shaft and a second main shaft which have rotation axes parallel to each other and are coaxially opposed to each other, and along a theoretical control axis parallel to the rotation axes of the first and second main shafts. A movable tool rest, and a pair of tools mounted on the tool rest in opposite directions along the theoretical control axis to each other to separate different bars held on the first and second main spindles, respectively. A numerical control lathe configured to be capable of simultaneous machining, a tool position correcting method for automatically correcting a moving position of the tool post in a simultaneous machining process by the pair of tools, wherein the pair of tools used for simultaneous machining is used. A tool is fixedly mounted on the tool post in a posture at the time of machining, and for each of the pair of tools mounted on the tool post,
An error of the actual position with respect to the tool position specified by the machining program is determined, and a correction ratio that relatively represents a degree of correcting the error with respect to the error obtained with respect to the pair of tools is set, based on the correction ratio. Calculating an optimum correction amount for the error, and correcting the moving position of the tool post according to the optimum correction amount. 5. A control device for performing the tool position correction method according to claim 4, wherein the control device stores a calculation formula for calculating the optimum correction amount and specifies the calculation formula by the input machining program. A controller that corrects a tool movement position of the pair of tools according to the optimum correction amount calculated from the calculation formula, and controls movement of the tool post based on the corrected tool movement position. .