JP5517483B2 - Lathe and method of correcting turret position in lathe - Google Patents

Description

  The present invention relates to a technique for correcting the relative positional relationship between a main spindle of a lathe and a tool post in order to obtain high machining accuracy, and to the above technique in a lathe provided with two or more tool rests.

  Errors and deformations of the machine tool itself are reflected in the machining accuracy of the workpiece machined by the machine tool. As errors of the machine tool itself, there are machining errors and assembly errors of components, and as deformations, there are errors in the installation surface, elastic deformation due to its own weight and processing reaction force, aging of dimensions and shapes, thermal deformation, and the like. A lathe is a machine tool that processes a workpiece gripped by a spindle with a tool mounted on a tool post that moves relative to the spindle, and when the error or deformation changes the relative positional relationship between the spindle and the tool rest, The deformation and error affect the machining accuracy of the workpiece.

  In order to increase the machining accuracy of the workpiece, it is necessary to minimize the error and deformation of the machine tool itself, but it is impossible to make this zero. Therefore, machine tools aimed at high-precision machining are equipped with various correction means that correct the positional relationship between the spindle and the tool post so that errors and deformations in the machine tool itself are not reflected in the machining accuracy. ing. A typical example is a correction means that corrects thermal deformation of the machine tool, and a temperature sensor is attached to the bed or the tool post, and the position between the spindle and the tool post is determined based on the temperature detected by each part of the machine tool. The influence on the relationship is obtained from calculation and actual measurement values, and the machining error due to the thermal deformation of the machine tool is corrected by correcting the position of the tool post so as to cancel the influence.

  In the lathe, when machining a workpiece, the tool post moves in the Z direction (axial direction of the spindle) with respect to the spindle and in the X direction (tool cutting feed direction) perpendicular to the Z direction. If there is a processing error or an assembly error in the guide for guiding the movement, the processing error changes depending on the position of the tool post. Further, the tool post has its own weight, and the guide supporting the tool post is fixed to the bed (frame), and the bed has a magnitude of external force (the weight of the tool post is an external force acting on the bed) Depending on the position at which it acts, it is elastically deformed into a different shape, so that the processing error due to the elastic deformation of the bed also changes depending on the position of the tool post.

  The correction for correcting the positional relationship between the spindle and the tool post in association with the position of the tool post is called pitch error correction, and various techniques have been proposed. For example, in Patent Document 1 below, a machining error when machining is performed with the tool post in the first position and a machining error when machining is performed at a second position away from the first position are measured. Then, an error in the position of the tool post when machining the workpiece is obtained from these two measured values by linear interpolation, and a correction value for the direction and amount to cancel this error is given to the feed motor of the tool post. A technique for correcting a workpiece machining error that changes in relation to the position of the tool post has been proposed.

JP 2002-120127 A

  The technique described in Patent Document 1 is mainly intended to correct a workpiece machining error caused by a deviation of a guide that guides the tool post, and the bed elasticity that the shape of the bed changes depending on the position of the tool post. Processing errors due to deformation are not considered. In general, the elastic deformation of the bed is small compared to thermal deformation and secular change, and the idea that the rigidity of the bed is sufficiently high so that the elastic deformation due to the weight of the tool post does not affect the machining accuracy of the workpiece is a machine tool It is because it is considered common sense in designing.

  Therefore, even in a lathe equipped with a plurality of turrets, pitch error correction is mainly performed for each turret to correct the accuracy of guides and feed screws. Conventionally, little consideration has been given to how the processing accuracy of processing performed with this tool post is affected by the position of other tool post and how to correct it.

  On the other hand, improvement of machining accuracy required for lathes, enlargement of the tool post due to demands for heavy cutting and high-speed machining, reduction of machine frame due to demands for reduction of machine installation area and price reduction, etc. Yes.

  In the background surrounding such machine tools, a lathe equipped with a plurality of turrets, in particular, one of the turrets is a turret for attaching a large rotary tool, When it is a turret with a tool changer to be installed, a turret with a large tool turret, or a turret attached to the bed with a large overhang It has been recognized that the machining error of the machining with the tool mounted on the other tool rest changes depending on the position and moving speed of the tool rest.

  Therefore, in the present invention, in a lathe equipped with a plurality of turrets, machining errors related to the position and moving speed of other turrets occur in machining performed with a tool mounted on one of the turrets. The challenge is to prevent it.

The turret position correction method according to the present invention is a turret position correction method applied to a lathe provided with at least two turrets 4 and 5 that are moved and positioned on a bed in at least two directions orthogonal to each other. . In the present invention, the relative position of at least one of the two tool rests 4 with respect to the spindles 2 and 3 is related to the position information of the other tool rest 5 and the moving speed information of the other tool rest 5. to correct.

That is, the lathe according to the present invention includes at least two tool rests 4 and 5 that are moved and positioned on the bed in at least two directions orthogonal to each other, and the spindles 2 and 3 of one of the two tool rests 4 are provided. Is corrected in relation to position information of the other tool rest 5 of the two tool rests and movement speed information of the other tool rest 5 .

  The position correcting means in the lathe of the present invention includes a database 14 including a table in which correction values to be given to one (self) and the other tool rest are registered for each predetermined position of each tool rest 4 and 5; The position information or the movement destination information of the tool rests 4 and 5 is received, the correction value is read from the position on the table corresponding to the position or the movement destination position, the necessary interpolation calculation is performed, and the correction value is further corrected at a predetermined change rate. Correction value output means 15 for outputting while changing the angle, and coordinate origin shift means 13 for shifting the coordinate origin serving as a reference for the moving position of the tool post that is currently being processed using the output correction value. be able to.

Also based Dzu rather correction to each tool rest in the moving speed information, the database 14, for each predetermined speed of movement of the tool rest, on the other hand has registered the correction value to be given to the (itself) and the other tool rest Although it may be a database including a table, it is convenient to perform correction by a method of increasing or decreasing a correction value obtained based on position information based on speed information.

  That is, the database 14 includes a second table in which increase / decrease data for increasing / decreasing the correction value to be applied to the tool post to be corrected is included for each of a plurality of predetermined moving speeds of the tool rests 4 and 5. The value output means 15 receives the moving speed information of each tool post, reads the increase / decrease data corresponding to the moving speed information from the second table, and increases / decreases the correction value obtained from the position information with the increase / decrease data. And

  In a lathe equipped with a main spindle 3 that moves on a bed, the position and moving speed of the main spindle may affect the processing accuracy of processing performed by a tool mounted on the one tool post. In such a case, the above method can be applied by regarding the head stock 31 of the moving spindle as the other tool rest.

  Further, when the ratio of the weight of the tool attached to the tool post is larger than the weight of the other tool post 5, the correction value may be changed depending on which tool is attached to the tool post. desirable. The change of the correction value is the same means as the change of the correction value based on the moving speed of the tool post described above, that is, the third table in which increase / decrease data for increasing / decreasing the correction value according to the weight of the tool to be mounted is registered. This is preferably performed by means of increasing and decreasing the correction value in terms of simplifying the control procedure and improving the control response.

  Note that which tool is mounted on the other tool post automatically depends on the tool data registered in the lathe controller and the tool change performed immediately before, which is automatically applied to the position correction means. Can be recognized. When the above automatic recognition cannot be performed, such as when the tool is changed manually, the type of tool or the weight of the tool is manually input for recognition.

  According to the present invention, machining errors caused by elastic deformation of the machine tool itself depending on the position and speed of the tool post are corrected, and machining can be performed with higher accuracy. In particular, it is effective in improving machining accuracy in a composite lathe equipped with a tool post on which a large rotating tool is mounted.

The block diagram which showed the principal part of the lathe concerning this invention Flowchart showing the overall flow of the correction procedure in the lathe of FIG.

  Next, specific embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an example of a two-spindle opposed lathe according to the present invention. The two-spindle counter lathe in the figure is mounted on the bed so that it can be moved and positioned in the direction of the main axis so that it is opposed to the left main axis 2 on the same main axis axis a as the left main axis 2 and is supported on a main spindle fixed to the bed. The right main spindle 3 supported by the main spindle and the first and second tool rests 4 and 5 positioned independently in the Z direction and the X direction, respectively. The first tool post 4 and the second tool post 5 are disposed to face each other with the spindle axis a interposed therebetween.

  The first tool post 4 is mounted on a first Z moving table (not shown) that is screwed into a first Z feed screw 41 that is mounted on the bed in the Z direction. The first tool post 4 drives the first Z feed screw 41 forward and backward. The movement position in the Z direction is set by the 1Z feed motor 42. Further, the first tool post 4 is screwed into a first X feed screw 43 mounted in the X direction on the first Z moving table, and a first X feed motor 44 for driving the first X feed screw 43 in the forward and reverse directions. To set the movement position in the X direction.

  The second tool post 5 is mounted on a second Z moving base (not shown) that is screwed into a second Z feed screw 51 mounted on the bed in the Z direction, and drives the second Z feed screw 51 forward and backward. The movement position in the Z direction is set by the 2Z feed motor 52. Further, the second tool post 5 is screwed into a second X feed screw 53 mounted in the X direction on the second Z moving table, and a second X feed motor 54 for driving the second X feed screw 53 forward and backward. To set the movement position in the X direction.

  The headstock 31 of the right spindle 3 is moved and positioned in the Z direction by a spindle feed motor 33 that is screwed into a spindle feed screw 32 mounted on the bed in the Z direction and drives the spindle feed screw 32 forward and backward. Is done.

  A first tool 45 is mounted on the first tool post 4 toward the spindle axis a side. A second tool 55 is mounted on the second tool post 5 toward the spindle axis a side. Although not shown in the drawing, for example, a tool changer is mounted on the first tool post 4, and one of the tools accommodated in a tool magazine (not shown) is changed as the first tool 45 by the tool changer in a timely manner. Is attached. Further, for example, the second tool 55 is mounted on the second tool post 5 via a tool turret (not shown) mounted on the second tool post 5. The first turret 4 and the second turret 5 can be turrets that are also moved and positioned in the Y direction perpendicular to the Z and X directions. Since the amount of movement in the Y direction is small, the lathe according to this embodiment does not perform correction based on the movement position of the tool rests 4 and 5 in the Y direction.

  The feed motors 42, 44, 52, 54 and 33 have their rotational directions and rotational speeds controlled by machining programs registered and executed in the NC controller 12 of the lathe controller 11. The positions of the respective tool rests 4 and 5 instructed from the NC control unit 12 are set by the distances from the coordinate origin o of the coordinates 46 and 56 set for the respective tool rests. The coordinates 46 and 56 in the figure indicate the directions of the coordinate axes, and do not indicate the origin positions of the coordinates.

  The machining shape of the workpiece is determined by the relative positional relationship between the cutting edges of the tools 45 and 55 mounted on the respective tool rests 4 and 5 and the spindles 2 and 3 that work the workpiece in cooperation with the tool rest. The positions of the cutting edges of the tools 45 and 55 with respect to the tool rests 4 and 5 are different for each tool. Therefore, tool data including the positional relationship between the cutting edge of the tool used for machining and the tool post (actually the tool mounting part of the tool post) is registered in the NC control unit 12 to replace the tool and index the turret. Each time the angle is changed, the coordinate origin shift means 13 of the NC control unit 13 makes the turret position output from the NC control unit a position corresponding to the position of the tool cutting edge based on the tool data. The coordinate origin that is the origin of the movement position of each tool post is moved (shifted).

A correction amount database 14 and a correction program (correction value output means) 15 are registered in the lathe controller 11, and the correction program 15 receives coordinate information and moving speed information of the tool rests 4 and 5 from the NC control unit 12. The correction information is output to the NC control unit 12. The correction program 15 searches the correction amount database 14 based on the received coordinate information and speed information, and receives correction values or increase / decrease data registered in the database.

  Tables 1 to 5 show examples of tables registered in the correction amount database 14.

  Tables 1 and 2 are tables used when machining a work gripped by the left main spindle 2 with a tool mounted on the first tool post 4. Table 1 shows that the correction amount of the X coordinate of the first tool post 4 (self) with respect to its own position (coordinates) is such that the first tool post 4 is in the range of −400 to 400 mm in the Z direction and the X direction. In addition, the correction amount of the X coordinate of the first tool rest 4 at the position of every 100 mm when moving in the range of −200 to 200 mm is registered in units of microns. Table 2 also shows that the correction amount of the X coordinate of the first tool post 4 relative to the position (coordinates) of the second tool post 5 is in the range of −400 to 400 mm in the second tool post 5 in the Z direction, and X The correction amount of the X coordinate of the first tool post 4 at the position of every 100 mm when moving in the range of −200 to 200 mm in the direction is registered in units of microns. In addition, the column marked with “...” In Tables 2 and 4 is a column in which the numerical value is omitted, and some numeric value is actually registered.

表３と表４は、第１刃物台４に装着した工具で右主軸３に把持されたワークを加工するときに用いるテーブルである。表３には、自分自身の位置（座標）に対する第１刃物台４（自分自身）のＸ座標の補正量が、第１刃物台４がＺ方向に−４００〜４００ｍｍの範囲で、かつＸ方向に−２００〜２００ｍｍの範囲で動いたときの、１００ｍｍ毎の位置における第１刃物台４のＸ座標の補正量が、ミクロン単位で登録されている。また、表４には、第２刃物台５の位置（座標）に対する第１刃物台４のＸ座標の補正量が、第２刃物台５がＺ方向に−４００〜４００ｍｍの範囲で、かつＸ方向に−２００〜２００ｍｍの範囲で動いたときの、１００ｍｍ毎の位置における第１刃物台４のＸ座標の補正量が、ミクロン単位で登録されている。

Tables 3 and 4 are tables used when machining a work gripped by the right main spindle 3 with a tool mounted on the first tool post 4. Table 3 shows that the correction amount of the X coordinate of the first tool post 4 (self) relative to its own position (coordinates) is such that the first tool post 4 is in the range of −400 to 400 mm in the Z direction and the X direction. In addition, the correction amount of the X coordinate of the first tool rest 4 at the position of every 100 mm when moving in the range of −200 to 200 mm is registered in units of microns. Table 4 also shows that the correction amount of the X coordinate of the first tool rest 4 with respect to the position (coordinates) of the second tool rest 5 is in the range of −400 to 400 mm in the second tool rest 5 in the Z direction, and X The correction amount of the X coordinate of the first tool post 4 at the position of every 100 mm when moving in the range of −200 to 200 mm in the direction is registered in units of microns.

表５は、各刃物台の移動速度による補正量の重み付けを登録したテーブルで、適宜設定した速度毎に補正量に与える重み付けが％表示で登録されている。登録された補正量の値は、個々の機械について実際に加工したワークの寸法を計測することによって得られた値である。

Table 5 is a table in which weights of correction amounts according to the moving speeds of the respective tool rests are registered. Weights to be given to the correction amounts for each appropriately set speed are registered in%. The registered correction value is a value obtained by measuring the dimensions of the workpiece actually processed for each machine.

  Tables 1 to 5 are tables in which correction amounts for the first tool rest 4 are registered. If a similar correction is necessary when machining a workpiece with a tool mounted on the second tool post 5, a table similar to Tables 1 to 5 for correcting the position of the second tool post 5 in the X direction is used. sign up. If there are three or more tool rests and the same correction is performed for the third tool rest and the fourth tool rest, the same tables as those in Tables 1 to 5 are registered for these tool rests.

  The correction program 15 calculates a correction amount for the tool rest that is currently processing the workpiece from the position information and the moving speed information of the tool rests 4 and 5 given from the NC control unit 12. For example, the first tool post 4 is machining a workpiece gripped by the left main spindle at a position of Z = −300 mm and X = −100 mm, and the second tool post is at a position of Z = 300 mm and X = −200 mm. The correction amount of the first tool post 4 when the moving speed of the first tool post 4 is 3000 mm / min and the second tool post 5 is stopped is based on the position of the first tool post 4 from Table 1. The correction amount is 8 microns, the correction amount based on the position of the second turret 5 from Table 2 is 3 microns, the weight based on the movement speed of the first turret is 80% from Table 5, and is based on the movement speed of the second turret. Since the weighting is 100%, a coordinate shift signal of 8 × 0.8 + 3 × 1 = 9.4 microns is output to the NC control unit 12. Upon receiving this signal, the NC control unit 12 shifts the origin of the coordinate o serving as the movement reference of the first tool rest 4 in the X direction by 9.4 microns.

  When the tool post is at a position intermediate between the positions registered in the table, it is effective to obtain the correction amount by approximating the position to the registered coordinates, or to obtain the correction amount by interpolation. The approximation here is, for example, that the columns of Z coordinate −300 mm and X coordinate −100 mm in Table 1 are regarded as correction amounts when they are in the ranges of Z coordinate −350 to −250 mm and X coordinate −150 to −50 mm. Is the correction amount. Similarly, in Table 5, a weighting amount of 80% with a speed of 3000 mm / min is used for a speed in the range of 2000 to 4000 mm / min.

  When interpolating, for example, if the Z coordinate of the first tool post is −250 mm and the X coordinate is −50 mm, X = −100 in Table 1 and 7.5 between Z = −300 and −200 are read. , X = 0, Z = 5.5 in the middle of −300 and −200, and 6.5 in the middle of 7.5 and 5.5.

  Similarly, in Tables 2 to 4 and 5, the position or velocity is approximated to the value registered in the table, or the coordinate shift value to be given to the NC control unit 12 is obtained by the interpolation operation as described above.

  When the correction amount is obtained by approximating the position and speed of the tool post to the values registered in the correction amount table, the correction amount changes in units of microns at the intermediate position between the registered position and speed. For example, when the position of the first tool post 4 is corrected using the registered values in the table of Table 1, the correction amount changes by 1 micron when passing through a position of 250 mm in the Z direction at a position of X = −100 mm. To do. If this correction amount is applied to the NC control unit as it is, there is a risk that a streak will occur on the workpiece at a position of Z = 250 mm. In order to avoid this streak, when the correction amount changes stepwise, a new correction amount is set while gradually changing the change amount at a predetermined change rate corresponding to the moving distance of the tool post. To.

  When calculating the correction amount by interpolation, this kind of consideration is considered unnecessary, but in case the correction amount suddenly changed for some reason, the maximum allowable rate of change was set and calculated from the table. It is desirable to change the correction amount at the maximum registered change rate when the change rate exceeds this change rate.

  FIG. 2 is a flowchart showing overall control performed in the correction program 15. First, the correction program 15 reads the positions and movement speeds of the first tool post and the second tool post from the NC control unit 12 (steps 101 and 102). Next, it is determined whether the correction is for the first turret or the second turret (when both the first turret and the second turret are machining, this determination is performed alternately). For each turret, it is determined whether the right spindle work is being processed or the left spindle work is being processed (steps 103 and 104), and the procedure as described above in steps 105, 106, 107, and 108 is performed. Read the correction amount with.

  Here, Tables 1 and 2 are correction amount tables used in Step 105, Tables 3 and 4 are correction amount tables used in Step 106, and Tables 1 to 5 are referred to for correction amount tables used in Steps 107 and 108. Since it is self-explanatory, it is omitted.

  In steps 109 and 110, the origin of the coordinates serving as the reference for the position of each tool post is gradually changed and output to the NC control unit 12. By repeating this control loop at regular time intervals, in a lathe equipped with a plurality of tool rests, the tool that is actually machining the machining error based on the elastic deformation of the machine that changes depending on the position and speed of each tool rest. Compensation can be performed including not only the position and speed of the platform, but also the elastic deformation of the machine due to the position and speed of other turrets that are waiting, the same workpiece, or other workpieces are being machined. It is possible to improve the accuracy, in particular, the workpiece machining accuracy in a lathe provided with a plurality of turrets including a large turret.

2, 3 Spindle 4, 5 Turret 12 NC control unit 13 Coordinate origin shift means 14 Database 15 Correction value output means 33 Spindle feed motor 42, 44 Feed motor 52 for turret 4 52, 54 Feed motor for turret 5

Claims (4)

In a lathe provided with at least two tool rests that are moved and positioned in at least two directions orthogonal to each other on a bed, the relative position of the two tool rests with respect to the main axis of one of the tool rests is determined by the two tool rests. A lathe comprising position correcting means for correcting in relation to position information of the other tool rest of the table and movement speed information of the other tool rest. The position correction means includes a first table in which correction values to be given to the one tool post when the other tool post is at each of a plurality of predetermined positions, and the other tool post has a predetermined value. A second table in which increase / decrease data of the correction value given to the one tool post when moving at each of a plurality of moving speeds is registered, and position information or movement destination information of the other tool post is stored; The correction value is read from the position on the first table corresponding to the received position or the position of the moving destination, and the increase / decrease data corresponding to the moving speed information is received by receiving the moving speed information of the other tool post. A correction value output means for increasing / decreasing the correction value read from the second table, and a coordinate source for shifting a coordinate origin serving as a reference for the movement position of the one tool post using the increased / decreased correction value. And a shifting means, according to claim 1 lathe according. In a method for correcting a tool post position in a lathe provided with at least two tool rests that are moved and positioned in at least two directions orthogonal to each other on a bed, a relative position of at least one of the two tool rests to a main axis of the tool post Is corrected in relation to the position information of the other tool rest and the moving speed information of the other tool rest, and a method for correcting the tool rest position in a lathe. A first table in which correction values to be given to the one tool post when the tool post is located at the moving position for each of a plurality of movement positions of the other tool post, and the other tool post having a predetermined A second table in which increase / decrease data of the correction value to be given to the one tool post when moving at each of a plurality of moving speeds is prepared, and corresponds to position information of the one tool post The correction value is read or interpolated from the position on the first table, the moving speed information of the other tool rest is received, and the increase / decrease data corresponding to the moving speed information is read from the second table. The tool in a lathe according to claim 3 , wherein the correction value is increased or decreased, and the coordinate origin serving as a reference of the moving position of the one tool post is shifted at a predetermined change rate using the correction value after the increase or decrease. Stand Correction method of location.

Images