JP2009146057A - Method and unit for correcting position error - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a unit for correcting a position error of a main shaft, which improves quality of a working surface while simplifying setting work. <P>SOLUTION: The position error correction method includes a first process for setting a tool length L<SB>i</SB>of a reference tool and origin coordinates X<SB>i</SB>, Y<SB>i</SB>, Z<SB>i</SB>which as tip coordinates of the mounted reference tool; a second process for calculating a tool length difference ΔL between a tool length L<SB>c</SB>of a tool in use for processing and a tool length L<SB>i</SB>of the reference tool; a third process for calculating a deviation amount, based on the tool length difference ΔL and a squareness error produced between orthogonally intersecting two shafts; a fourth process for calculating use origin coordinates X<SB>p</SB>, Y<SB>p</SB>, Z<SB>p</SB>as tip coordinates of the tool in use, based on the deviation amount; and a fifth processing for calculating an instruction position of the main shaft, using the use origin coordinates X<SB>p</SB>, Y<SB>p</SB>, Z<SB>p</SB>. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a position error correction method for correcting a position error of a spindle in a machine tool, and a position error correction apparatus for executing the correction method.

  Conventionally known machine tools include a machine tool 31 as shown in FIG. The machine tool 31 includes a main shaft 32 on which a tool can be mounted and a table 33 on which a workpiece can be fixed. The main shaft 32 is a table in two orthogonal directions (X axis and Z axis). 33 is provided to be movable in the Y-axis direction orthogonal to the X-axis and the Z-axis, respectively, and the main shaft 32 is processed while being fed in the three-axis direction relative to the workpiece fixed to the table 33. Will do.

However, the three axes are not strictly orthogonal due to manufacturing errors and the like, and there is a squareness error between the axes. For example, there is a squareness error α _XZ between the _XZ axes as shown in FIG. 2, and the Z axis that should be orthogonal to the X axis in design is the Z ′ axis. In this case, a position error occurs in the X-axis direction due to the movement of the main shaft 32 in the Z′-axis direction.
Further, when a tool having a different tool length is mounted on the spindle 32, if the Z coordinate of the tool tip is matched, a position error ΔX _XZ occurs in the X-axis direction. Therefore, when the spindle 32 is raised by the difference in tool length during tool replacement, there is a problem that a step in the X-axis direction is formed on the machining surface and the quality of the machining surface is deteriorated. .

Therefore, in order to cope with the above problem, for example, a position error correction method for the spindle as disclosed in Patent Document 1 has been devised. In the position error correction method disclosed in Patent Document 1, lattice points are set at predetermined intervals in the operation region of the main axis, and the correction amount of the position error for each lattice point is calculated, while moving in the three axis directions of the main axis. It controls the feeding operation.
In addition, the origin coordinate of the tool tip is set in advance for each tool, and each time the tool is replaced, the feed operation of the spindle is controlled using the origin coordinate corresponding to the tool, thereby eliminating the above step. There is also a method.

Japanese Patent No. 3174704

When machining as shown in FIG. 5 is performed using the correction method of Patent Document 1, the command value in the X-axis direction is minus when machining vertically downward in section a, and machining at an inclination angle θ2 in section b. Sometimes it is a plus. That is, the command value in the X-axis direction is inverted during curved surface processing when transitioning from section a to section b. At the time of this reversal, a follow-up delay occurs due to backlash or lost motion of the feed screw, etc., resulting in the formation of protrusions etc. on the machined surface, and the quality of the machined surface tends to deteriorate, especially when the machined surface is curved. There is a problem.
Also, the Z axis and the spindle axis are not strictly parallel due to manufacturing errors or the like, and there is a parallelism error β _XZS in the XZ plane between the Z axis and the spindle axis as shown in FIG. Yes. Therefore, due to the parallelism error β _XZS , in a tool having a different tool length, a deviation ΔX _ZS occurs in the X coordinate of the tool tip. However, the correction method of Patent Document 1 has a problem in that the deviation ΔX _ZS cannot be corrected.
Furthermore, in the method in which the origin coordinates of the tool tip are set in advance for each tool and correction is attempted, the origin coordinates must be set for each tool, which is troublesome.

  Accordingly, the present invention has been made in view of the above problems, and provides a spindle position error correction method and a position error correction apparatus capable of improving the quality of a machined surface and simplifying a setting operation. It is something to be offered.

In order to achieve the above object, the invention according to claim 1 of the present invention is provided on the machine tool main body so as to be relatively movable with respect to the workpiece, and is capable of mounting tools having different tool lengths. A position error correction method for correcting a position error of a main spindle, which is used for machining, a first step of setting a tool length of a reference tool and an origin coordinate serving as a tip coordinate of a mounted reference tool The second step of calculating the tool length difference between the tool length of the tool to be used and the tool length of the reference tool, and calculating the deviation amount based on the tool length difference and the geometric error of the machine tool body A third step, a fourth step of calculating a use origin coordinate serving as a tip coordinate of the tool to be used based on the deviation amount, and a fifth step of calculating a command position of the spindle using the use origin coordinate And executing.
The “geometric error” in the present invention refers to an accuracy error originally occurring in the machine tool main body, for example, a perpendicularity error between two orthogonal axes or a perpendicularity error between a rotation axis and a rectilinear axis.・ Including parallelism error.

According to a second aspect of the present invention, in the first aspect of the present invention, a position for correcting a position error of a spindle provided so as to be relatively movable in a biaxial direction at least orthogonal to the workpiece. In the error correction method, in the third step, a deviation amount is calculated based on the tool length difference and a squareness error occurring between the two orthogonal axes.
Furthermore, the invention according to claim 3 is a position for correcting a position error of a spindle provided in the invention according to claim 1 or 2 so as to be relatively movable with respect to the workpiece in at least the spindle axis direction. In the error correction method, in the third step, a deviation amount is calculated based on the tool length difference and a parallelism error occurring between the spindle axis and the movement direction of the spindle.

  On the other hand, in order to achieve the above object, the invention according to claim 4 of the present invention is provided with a tool having a different tool length provided on the machine tool main body so as to be movable relative to the workpiece. A position error correction device for correcting a position error of a spindle that is made possible, the tool length of a reference tool, the tool length of a tool used for machining, and the tip coordinates of a reference tool mounted on the spindle Tool length difference calculation for calculating the tool length difference between the origin coordinates and the storage means for storing the geometric error of the machine tool body and the tool length of the tool used and the tool length of the reference tool Means, a deviation amount calculating means for calculating a deviation amount based on the tool length difference and the geometric error, and calculating a use origin coordinate serving as a tip coordinate of the tool to be used based on the deviation amount. Use origin coordinate calculation means, Characterized in that it comprises a command position calculating means for calculating a command position of the main spindle with the origin coordinates.

According to the present invention, every time a tool having a different tool length is mounted on the spindle, the use origin coordinate is newly calculated based on the tool length and the origin coordinate of the tool used, and the position of the spindle is calculated using the use origin coordinate. Make a command. Therefore, a step or the like is not formed on the processed surface due to a deviation or the like caused by tool change, and the quality of the processed surface can be improved. In addition, once the origin coordinates are set using the reference tool, the use origin coordinates are newly calculated based on the tool length of the tool used even if the tool is replaced during machining. Thus, it is possible to improve work efficiency without requiring complicated work such as setting the origin coordinates.
In particular, according to the second aspect of the present invention, the conventional position command for correcting the deviation caused by the squareness error for each machining point, although the deviation caused by the squareness error can be corrected. Unlike the case, for example, when performing the machining shown in FIG. 5, the command value in the X-axis direction is not reversed during curved surface machining from the section a to the section b. Therefore, the projections that have been formed on the processed surface due to backlash or lost motion during the reversal are not formed, and the quality of the processed surface can be further improved.
On the other hand, in particular, according to the invention described in claim 3, the position error correction is performed in consideration of the deviation caused by the parallelism error between the spindle axis and the moving direction of the spindle, so that the machined surface has an extremely high quality. be able to.

Hereinafter, a spindle position error correction method and a position error correction apparatus according to an embodiment of the present invention will be described with reference to the drawings. Note that the position error correction method and the position error correction apparatus in this embodiment will be described as being applied to the machine tool 31 shown in FIG.
FIG. 2 is an explanatory view schematically showing that a _squareness error α _XZ exists between the X and Z axes in the machine tool 31, and FIG. 3 is a diagram between the Z axis and the spindle axis line in the machine tool 31. It is explanatory drawing which showed typically that the parallelism error (beta) _XZS exists in XZ plane. FIG. 4 is a block diagram of the position error correction apparatus 1.

The position error correction apparatus 1 includes origin coordinates X _i , Y _i , Z _i , reference tool length L _i , tool length L _{c of} various tools, and machine tool 31 set as described later. tool length reads the storage means 2 for storing a geometric errors such as squareness error α and parallelism errors beta, a reference tool length L _i and tool length L _c to be used from the storage means 2 with Based on the tool length difference calculation means 3 for calculating the difference ΔL, the squareness error α, the parallelism error β stored in the storage means 2 and the tool length difference ΔL calculated by the tool length difference calculation means 3. Correction amount calculation means (deviation amount calculation means) 4 for calculating correction amounts δX, δY, δZ of the origin coordinates, origin coordinates X _i , Y _i , Z _i and correction amount calculation stored in the storage means 2 Based on the correction amounts δX, δY, δZ calculated by the means 4, Moving the coordinates _{X p,} Y _p, as used origin coordinate calculation means 5 for determining the _{Z p,} use was calculated by the use origin coordinate computing means 5 origin coordinates _{X p,} Y _p, the main shaft 32 using _{Z p} Command position calculating means 6 for calculating a command position for the control. Then, the command position calculation means 6 outputs the calculated command position to each servo amplifier 7, and each servo amplifier 7 controls the servo motor 8 of each axis based on the command position, and the X axis of the main shaft 32. The movement in the Y-axis and Z-axis directions is controlled. Note that the command position calculation means 6 determines the command position based on the use origin coordinates X _p , Y _p , Z _p in consideration of the deviation ΔX _XZ in the X-axis direction caused by the _squareness error α _XZ as described later. The calculation is performed, and right angle error correction is not performed for each processing point as in the correction method described in Patent Document 1.

Here, a position error correction method by the position error correction apparatus 1 will be described.
First, when machining with the machine tool 31, the work is fixed on the table 33, the reference tool _Ti is attached to the spindle 32, and the reference tool _Ti is brought into contact with a predetermined corner of the work from two directions. Then, the origin coordinates X _i , Y _i , Z _i are set, and the origin coordinates X _i , Y _i , Z _i and the tool length of the reference tool T _i used for the setting (that is, the reference tool length) L _i Are stored in the storage means 2 (first step). Thereafter, when machining is performed using the reference tool T _i , the command position calculation means 6 calculates the command position using the set origin coordinates X _i , Y _i , and Z _i .

On the other hand, when the machining is continued by exchanging with a tool T _c having a different tool length from the reference tool T _i , the position error correction device 1 uses the tool length L _c of the tool T _{c to be} used and the reference tool T _i . The tool length _Li is read from the storage means 2, and the tool length difference calculation means 3 calculates the tool length difference ΔL = L _c −L _i (second step). Next, the correction amount calculation means 4 obtains a deviation ΔX _XZ = α _XZ · ΔL generated in the X-axis direction using the calculated tool length difference ΔL and the squareness error α _XZ between the X-Z axes ( Third step), a correction amount δX _XZ = −ΔX _XZ is calculated. Further, a deviation ΔY _YZ = α _YZ · ΔL generated in the Y-axis direction is obtained using the squareness error α _YZ between the Y-Z axes (third step), and a correction amount δY _YZ = −ΔY _YZ is calculated.
Further, the correction amount calculation means 4 uses the calculated tool length difference ΔL and the parallelism error β _XZS in the XZ plane between the Z axis and the spindle axis to _obtain X resulting from the parallelism error β _XZS. A deviation ΔX _ZS = β _XZS · ΔL in the axial direction is obtained (third step), and a correction amount δX _ZS = −ΔX _ZS is calculated. In addition, a deviation ΔY _ZS = β _YZS · ΔL in the Y-axis direction due to the parallelism error β _YZS in the YZ plane between the Z axis and the main axis is obtained (third step), and the correction amount δY _ZS = −ΔY _ZS is calculated. In this case, since the correction amount is obtained based on the Z-axis coordinates, the correction amount δZ in the Z-axis direction is zero. Further, it is _{assumed that the squareness} error α _XZ between the X and Z axes, the parallelism error β _XZS between the Z axis and the spindle axis, and the like are measured in advance and stored in the storage unit 2.

When the correction amounts δX (= δX _XZ + δX _ZS ), δY (= δY _YZ + δY _ZS ), and δZ (= 0) in the respective axis directions are calculated as described above, the use origin coordinate calculation means 5 stores them. The origin coordinates X _i , Y _i , Z _i are read from the means 2 and the correction amounts δX, δY, δZ are added to the origin coordinates X _i , Y _i , Z _i , and used origin coordinates X _p , Y _p , calculating a Z _p (fourth step). Then, the command position calculation means 6 calculates the command position using the newly calculated use origin coordinates X _p , Y _p , Z _p (fifth step), and each axis of the spindle 32 is calculated according to the calculated command position. Machining with the newly mounted tool _Tc is performed while controlling movement in the direction.

According to the position error correction apparatus 1 that performs position error correction as described above, every time a tool having a different tool length is mounted on the spindle 32, the use origin coordinate X is based on the origin coordinates X _i , Y _i , Z _{i. p, Y} p, newly calculated _{Z p,} performs a position command of the spindle 32 with the use origin coordinates _{X p,} Y _p, the _{Z p.} Therefore, a step or the like is not formed on the processed surface due to the deviation ΔX _XZ or the like caused by tool change, and the quality of the processed surface can be improved.

Further, not only the squareness error α between the X and Z axes, but also the deviations ΔX _ZS and ΔY _ZS caused by the parallelism error β between the Z axis and the spindle axis that could not be corrected by the conventional position error correction method. Therefore, the processed surface can be made extremely high quality.
Furthermore, once the origin coordinates X _i , Y _i , Z _i are set using the reference tool T _i , the used origin coordinates X _p , Y _p , Z _p are newly set based on the tool length L _c after the replacement. Therefore, a complicated operation such as setting the origin coordinates for each tool is not required, and the work efficiency can be improved.
In addition, a position command such as correcting a deviation (for example, ΔX _XZ ) due to the squareness error for each machining point is performed (that is, correction in the X-axis direction is performed at any time despite moving in the direction parallel to the Z-axis). For example, when the machining shown in FIG. 5 is performed, the command value in the X-axis direction is not reversed during the curved surface machining from the section a to the section b. Therefore, the projections that have been formed on the processed surface due to backlash or lost motion during the reversal are not formed, and the quality of the processed surface can be further improved.

  Note that the configuration according to the position error correction method and the position error correction apparatus of the present invention is not limited to the aspect described in the above embodiment, and is appropriately selected as necessary without departing from the spirit of the present invention. It can be changed.

For example, in the above embodiment, the correction amounts δX, δY, and δZ are calculated based on the Z-axis coordinates, but naturally the correction amounts δX, δY, and δZ are calculated based on the X-axis coordinates or the Y-axis coordinates. There is no problem.
In the above embodiment, both the deviation caused by the perpendicularity error between the two orthogonal axes and the deviation caused by the parallelism error between the spindle axis and the moving direction of the spindle are corrected. There is no problem even if it is configured to perform only one of the deviations. In addition, in the position error correction method of the present invention, for example, in a 5-axis control machine tool that is rotatably provided with a table for placing a workpiece, the rotation axis of the table and the straight axis of the main shaft It is also possible to apply to correction of deviation caused by parallelism error or squareness error. However, in this case, it is premised on machining with the rotation axis determined.
Further, in the above embodiment, the correction amount calculation means performs both the calculation of the deviation amount and the correction amount. However, the calculation of the deviation amount and the calculation of the correction amount are performed by separate calculation means. There is no problem even if it is configured, or the origin coordinate calculation means calculates the correction amount by receiving the deviation amount and also calculates the use origin coordinate.

Further, the use origin coordinates X _p , Y _p , Z _p calculated once are stored in the storage means 2 or the like in association with the use tool T _c , and the workpiece having the same shape is processed by the tool T _{c on} and after the next time. Can also be configured such that the use origin coordinate calculation means 5 reads the use origin coordinates X _p , Y _p , Z _p from the storage means 2.
In addition, it goes without saying that the position error correction apparatus according to the present invention is applicable to machine tools other than the portal machining center as shown in FIG.

It is explanatory drawing which showed the external appearance of the machine tool generally known conventionally. It is explanatory drawing which showed typically that _squareness error (alpha) _XZ exists between _XZ axes in a machine tool. It is explanatory drawing which showed typically that parallelism error (beta) _XZS exists in the XZ plane between a Z-axis and a spindle axis in a machine tool. It is a block block diagram of a position error correction apparatus. It is explanatory drawing which showed an example of a process.

Explanation of symbols

  1 .... Position error correction device 2 .... Storage means 3 .... Tool length difference calculation means 4 .... Correction amount calculation means 5 .... Use origin coordinate calculation means 6 .... Command position calculation means 7.・ Servo amplifier, 8. ・ Servo motor.

Claims (4)

A position error correction method for correcting a position error of a spindle provided on a machine tool body so as to be relatively movable with respect to a workpiece and capable of mounting a tool having a different tool length,
A first step of setting a tool length of the reference tool and an origin coordinate serving as a tip coordinate of the mounted reference tool;
A second step of calculating a tool length difference between a tool length of a tool used for machining and a tool length of the reference tool;
A third step of calculating a deviation amount based on the tool length difference and a geometric error of the machine tool body;
A fourth step of calculating a use origin coordinate serving as a tip coordinate of the use tool based on the deviation amount;
And a fifth step of calculating a command position of the spindle using the use origin coordinates. A position error correction method for correcting a position error of a spindle provided so as to be relatively movable in two axial directions orthogonal to a workpiece,
2. The position error correction method according to claim 1, wherein, in the third step, a deviation amount is calculated based on the tool length difference and a squareness error occurring between the two orthogonal axes. A position error correction method for correcting a position error of a spindle provided to be movable relative to a workpiece at least in the direction of the spindle axis,
3. The deviation amount according to claim 1, wherein, in the third step, a deviation amount is calculated based on the tool length difference and a parallelism error occurring between the spindle axis and the movement direction of the spindle. Position error correction method. A position error correction device for correcting a position error of a spindle that is provided in a machine tool main body so as to be movable relative to a workpiece and that can be mounted with tools having different tool lengths,
Storage means for storing a tool length of a reference tool, a tool length of a tool used for machining, an origin coordinate serving as a tip coordinate of a reference tool mounted on the spindle, and a geometric error of the machine tool body When,
Tool length difference calculating means for calculating the tool length difference between the tool length of the tool used and the tool length of the reference tool;
A deviation amount calculating means for calculating a deviation amount based on the tool length difference and the geometric error;
Based on the deviation amount, a use origin coordinate calculation means for calculating a use origin coordinate serving as a tip coordinate of the use tool;
A position error correction device comprising command position calculation means for calculating a command position of the spindle using the use origin coordinates.

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