JP5686578B2 - Geometric error measurement system - Google Patents

Description

  The present invention relates to a geometric error measurement system for measuring and correcting a geometric error in a multi-axis machine tool.

  As machine tools, multi-axis machine tools such as a 5-axis machining center in which a rotary axis and a turning axis are added to a conventional 3-axis machining center for the purpose of performing highly efficient machining and workpieces with complicated shapes are known. Improvement of machining accuracy in such a multi-axis machine tool is desired.

  In multi-axis machine tools, as the number of axes increases, the assembly accuracy tends to deteriorate and the machining accuracy tends to deteriorate. However, there is a limit to the improvement in assembly accuracy, so there is a limit between adjacent axes. A correction system has been developed that measures so-called geometric errors such as tilt and position error and corrects the geometric errors to improve machining accuracy.

  As a geometric error measurement (identification) method in such a correction system, a touch probe is attached to the spindle of the machine tool, a sphere that is a target (a jig to be measured) is installed on the table, and a turning axis or A method has been devised in which the indexing operation of the rotating shaft is performed a plurality of times, the position of the target is measured under each indexing condition, and the geometric error is automatically obtained (identified) based on the measurement results.

JP 2004-219132 A

  However, in the measurement system described above, an unexpected error may occur in the measurement result due to factors such as target misalignment and mechanical damage. Therefore, if the measurement system is equipped with a function that automatically updates the geometric error correction parameter, even if an unexpected measurement error is included, the geometric error correction parameter is automatically updated, and the automatically updated geometric error is updated. Since the correction of the main axis and the rotation axis is performed using the correction parameter, not only the machining accuracy cannot be improved, but also a situation where it is deteriorated may occur.

  The purpose of the present invention is to solve the problems of the conventional measurement system described above, and when equipped with a function for automatically updating the geometric error correction parameter, even if an inappropriate geometric error is measured based on disturbance or the like, An object of the present invention is to provide a geometric error measurement system capable of extremely effectively preventing a situation in which the machining accuracy of a multi-axis machine tool is lowered due to execution of such correction based on an inappropriate geometric error.

Among the present inventions, the invention described in claim 1 is a multi-axis machine tool comprising a plurality of linear axes and rotating axes, wherein a sensor is provided on the spindle and a measurement target is installed on the table, and a plurality of positioning conditions are provided. A geometric error measurement system for measuring the coordinates of the measurement target by the sensor and identifying a geometric error existing between adjacent axes using the measured values, and correcting the geometric error of the machine tool After the geometric error is identified, the addition value obtained by adding the geometric error after the previous identification to the identified numerical value is updated as a new geometric error, and the next geometric error is corrected . identification, geometric errors are those obtained as change from the update, set in advance geometric error and threshold value setting means capable of setting a threshold, identified geometric error threshold value setting means If exceeds the are threshold, it is characterized in that it has a notification means for notifying the situation.

 In the invention described in claim 2, in the invention described in claim 1, when the new geometric error setting value exceeds the threshold set in the threshold setting means, the notification means It is characterized by notifying the situation.

 The invention described in claim 3 is the invention described in claim 1 or claim 2, wherein the newly measured geometric error and the new geometric error setting value calculated from the geometric error are both threshold values. The geometric error update means automatically updates the calculated new geometric error setting value as a new geometric error setting value.

The invention described in claim 4 is the invention described in any one of claims 1 to 3, wherein either a newly measured geometric error or a new geometric error set value calculated from the geometric error is selected. If either of them exceeds the threshold value, the geometric error update means does not automatically update the calculated new geometric error setting value as a new geometric error setting value, but manually sets a new geometric error setting value. It is characterized by making possible.

  The invention described in claim 5 is the invention described in any one of claims 1 to 4, wherein the threshold value setting means is provided for each class including a plurality of geometric error correction parameters (for example, XYZ squareness error, main axis A threshold value can be set separately for each classification (tilt error, tilt error of rotation axis / swivel axis, position error, etc.).

  In the geometric error measurement system according to claim 1, when the geometric error identified (measured) exceeds a preset threshold value (allowable value), the situation is notified by the notification means. It is possible to easily grasp the state of the machine related to the. Therefore, according to the geometric error measurement system according to claim 1, a situation in which the machining accuracy of the multi-axis machine tool is reduced due to execution of correction based on an inappropriate identification result caused by a change in the machine over time or a measurement error. Can be effectively prevented.

  In the geometric error measurement system according to claim 2, when a new geometric error setting value calculated based on the identified geometric error exceeds a preset threshold value, the situation is notified by the notification means. Therefore, it is possible to easily grasp the state of the machine related to the accumulation of damage. Therefore, according to the geometric error measurement system according to claim 2, a situation in which the machining accuracy of the multi-axis machine tool decreases due to execution of correction based on inappropriate identification results due to accumulation of machine damage or measurement errors. Can be effectively prevented.

  The geometric error measurement system according to claim 3, wherein the geometric error setting value is automatically detected when both the newly measured geometric error and the new geometric error setting value calculated from the geometric error are below a threshold value. As a result, the geometric error setting value does not deviate from the true numerical value based on inappropriate identification due to machine trouble or measurement error. Therefore, according to the geometric error measurement system of claim 3, the situation in which the machining accuracy of the multi-axis machine tool is deteriorated due to the execution of the correction based on the inappropriate geometric error setting value is very effectively prevented. be able to.

  The geometric error measurement system according to claim 4, wherein any one of a newly measured geometric error and a new geometric error setting value calculated from the geometric error exceeds a threshold value. Since the setting value can be manually set without automatically updating the setting value, the newly identified geometric error evaluation result can be surely recognized by the user.

  The geometric error measurement system according to claim 5 can set a threshold separately for each classification including a plurality of geometric error correction parameters, so that an appropriate threshold can be easily set within a short time. it can. For example, the XYZ squareness error and the spindle tilt error are most influenced by the assembly accuracy of the machine, and therefore do not change greatly unless the machine is impelled. Therefore, there is no problem even if these geometric error threshold values are small. On the other hand, the tilt error and position error of the rotation axis and swivel axis can easily change due to thermal displacement of the machine, etc., and change depending on the model and structure, so it is necessary to set a relatively large threshold value. There are many cases. According to the geometric error measurement system of the fifth aspect, it is possible to easily set an appropriate threshold value suitable for each classification of geometric errors within a short time in consideration of such circumstances.

It is explanatory drawing (perspective view) which shows a machining center. It is a block diagram which shows the control mechanism of a machining center. It is a conceptual diagram of a memory | storage means. It is a conceptual diagram of the threshold storage area of a memory | storage means. It is a flowchart which shows the content of the measurement process of geometric error. It is explanatory drawing which shows the state which mounted | wore the spindle head with the touch probe, and mounted | worn the target with the table. It is explanatory drawing which shows a mode that a target sphere is measured in the some index position of C axis | shaft. It is explanatory drawing which shows a mode that a target sphere is measured in the some index position of A axis | shaft. It is a flowchart which shows the content of the threshold value determination process of the measurement result of a geometric error.

  Hereinafter, an embodiment of a geometric error measurement system according to the present invention will be described in detail with reference to the drawings. The geometric error measurement system according to the present embodiment is linked to the geometric error correction system, calculates a new geometric error correction parameter based on the measurement (identification) result, and sets the geometric error correction parameter to a new one. It can be automatically updated as a geometric error setting value (correction value).

<Configuration of multi-axis machine tool>
FIG. 1 shows a 5-axis control machining center (table turning type 5-axis machine) which is an example of a multi-axis machine tool (hereinafter simply referred to as a machining center M). The bed (base) 1 of the machining center M is provided with a substantially U-shaped trunnion 5 slidable along the Y-axis, and the trunnion 5 has a substantially U-shaped cradle in front view. 4 is provided to be rotatable around the A axis (rotating axis). Further, the cradle 4 is provided with a disk-like table 3 so as to be rotatable about a C axis (rotary axis) orthogonal to the A axis. In addition, a spindle head 2 on which a tool can be mounted is provided on the bed 1 so as to be slidable along an X axis perpendicular to the Y axis and a Z axis perpendicular to the X and Y axes. . The spindle head 2 can rotate the mounted tool about the Z axis.

  The machining center M causes the spindle head 2 to approach the workpiece (workpiece) fixed to the table 3 in a state in which the tool mounted on the spindle head 2 is rotated. Various processes can be performed on the workpiece while controlling the relative position and the relative posture between the workpiece and the tool. Further, since the machining center M is configured as described above, the connection of the axes from the workpiece to the tool is in the order of C axis → A axis → Y axis → X axis → Z axis.

<Machining center geometric error>
Next, the geometric error of the machining center M will be described. Here, it is assumed that the geometric error is composed of a total of six components (δx, δy, δz, α, β, γ) in the three directions of the relative translation error between the axes and the three directions of the relative rotation error. Each geometric error is indicated with two sandwiched axis names. For example, a translation error in the Y direction between the C axis and the A axis is expressed as δy _CA , and a rotation error around the Z axis between the Y axis and the X axis is expressed as γ _YX . The symbol indicating the tool is T.

Since the connection of the axis from the workpiece to the tool in the machining center M is the order of the C-axis, A-axis, Y-axis, X-axis, and Z-axis, there are a total of 30 geometric errors when considering the gap between the Z-axis and the tool. If one exists in the redundant relationship but the other is excluded, the final geometric error is δx _CA , δy _CA , α _CA , β _CA , δy _AY , δz _AY , β _AY , γ _AY. , Γ _YX , α _XZ , β _XZ , α _ZT , β _ZT in total. Of these, five of γ _YX , α _XZ , β _XZ , α _ZT , and β _ZT are geometric errors related to the linear axis, and the XY inter-axis perpendicular angle and the Y-Z inter-axis perpendicular angle, respectively. , Z-X axis perpendicularity, tool-Y axis perpendicularity, tool-X axis perpendicularity. The other eight are geometric errors related to the rotation axis, which are the C-axis center position X-direction error, the CA-axis offset error, the A-axis angle offset error, the CA-axis perpendicularity, and the A-axis center position, respectively. The Y-direction error, the A-axis center position Z-direction error, the A-X axis perpendicularity, and the A-Y axis perpendicularity. Hence, geometric errors in the machining center M is as in Table 1 _{below, δx CA, δy CA, α} CA, β CA, δy AY, δz AY, β AY, γ AY, γ YX, α XZ, β XZ, It is identified by _obtaining a total of 13 parameters of α _ZT and β _ZT .

  The above-mentioned geometric error correction parameters are as follows, as shown in Table 2 below: XYZ squareness error in three orthogonal axes, tilt error with respect to the rotation axis / swivel axis, position error with respect to the swing axis / rotation axis, and spindle with respect to the tilt of the spindle There are four types of tilt errors.

<Control mechanism of machining center>
FIG. 2 is a block diagram showing a control mechanism of the machining center M described above. The servo motors for translating the trunnion 5 and the spindle head 2 and the servo motors for rotating the cradle 4 and the table 3 are as follows. Drive control is performed by a control device (numerical control device) 21. In addition, the control device 21 outputs (notifies) an input unit 31 for setting an index position (index condition), a geometric error threshold value (allowable value), and a threshold determination result to be described later. An output means 32 such as a monitor and a speaker is connected.

  Further, the control device 21 is provided with a storage means 22, and in the storage means 22, as shown in FIG. 3, a program storage area 23 for storing various programs, variables used for various calculations, and the like. Are provided, a variable storage area 24 for storing various threshold values, a threshold storage area 25 for storing various preset threshold values, a parameter storage area 26 for storing each geometric error correction parameter, and the like.

  The program storage area 23 calculates a correction parameter calculation program for calculating a geometric error correction parameter used for correcting the geometric error based on the identified geometric error, and is calculated every time the geometric error correction parameter is calculated. A parameter update program for automatically updating the subsequent geometric error correction parameter as a new geometric error correction parameter is stored. Further, in the threshold storage area 25, as shown in FIG. 4, there are 4 XYZ squareness errors in three orthogonal axes, tilt errors with respect to the rotation axis / swing axis, position errors with respect to the rotation axis / swing axis, and spindle tilt errors with respect to the tilt of the spindle A threshold value (a numerical value preset by the manufacturer at the shipping stage or a numerical value arbitrarily set by the user) is stored for each classification. Furthermore, the parameter storage area 26 stores each geometric error correction parameter (or each geometric error correction parameter manually set by the operator) updated based on the previous geometric error measurement.

  Geometric error correction for correcting the geometric error of the machining center M by the control device 21, the trunnion 5, the servo motors for translating the spindle head 2, and the servo motors for rotating the cradle 4 and the table 3. The geometric error measurement system S including the system is configured.

<Measuring process of geometric error>
FIG. 5 is a flowchart showing the content of the geometric error measurement process (identification process) by the geometric error measurement system S. When identifying the geometric error, as shown in FIG. 6, a touch probe 11 is attached to the spindle head 2 instead of a tool, and a target sphere 12 as a target is fixed to the table 3 (assembled on the base of the target sphere 12). Fixed by a magnet etc.). The touch probe 11 has a sensor (not shown) that senses that the target sphere 12 has been touched, and can emit a signal using infrared rays, radio waves, or the like when the touch is sensed. Yes. On the other hand, the control device 21 of the machining center M stores, as a measurement value, the current position of each axis at the moment of receiving a signal emitted from the touch probe 11 by the connected receiver (or when the delay is taken into consideration). 22 can be stored.

  In step (hereinafter simply indicated by S) 1, the rotation axis (C axis) and the turning axis (A axis) are determined under a plurality of conditions in accordance with a command from the control device 21. Then, the center position and the like of the target sphere 12 are measured by the touch probe 11, and the geometric error is identified (measured) by using the calculation method described below in S2 based on the measured value.

[Calculation method of geometric error]
Here, the relationship between the measured value of the center position of the target sphere 12 and the geometric error will be described. The center position of the target sphere 12 is a table coordinate system (the coordinate system on the table 3 in which the intersection of the A axis and the C axis is the origin in an ideal state with no geometric error, and the X axis is parallel to the X axis of the machining center M) ) And (R, 0, H). The center position measurement value (x, y, z) of the target sphere 12 when there is no geometric error can be expressed by the following [Equation 1], where a is the A-axis angle and c is the C-axis angle.

On the other hand, the measurement value (x ′, y ′, z ′) of the center position of the target sphere 12 when there is a geometric error including the error (δx _WC , δy _WC , δz _WC ) of the mounting position of the target sphere 12. The matrix relational expression is the following [Equation 2]. However, the approximation is made assuming that the geometric error is minute.

  When this [Equation 2] is expanded, the following [Equation 3] is obtained. Here, in order to simplify the equation, the product of geometric errors is assumed to be minute and approximated to zero.

When identifying the geometric error, first, the A axis is determined in a state where the upper surface of the table 3 is perpendicular to the spindle head 2 (Z axis) (A axis angle a = 0 °), and the C axis angle c is set to 0. The center positions of the target spheres 12 at n locations for one round are measured by calculating at an arbitrary angle pitch from °. For example, if the angle pitch is 30 °, 12 measurements from 0 ° to 330 ° are performed as shown in FIG. 7 (hereinafter, this measurement is referred to as index measurement). As a result, when i = 1 to n, n spherical center position measurement values (x _i ′, y _i ′, z _i ′) are obtained, and the measurement values draw a circular locus. The A-axis and C-axis indexing positions (indexing conditions) in geometric error identification are stored in advance in the storage unit 22 of the control device 21.

Here, the radius of the measurement value on the XY plane, that is, the distance from the center position of the C axis to each center position measurement value is R when there is no geometric error, and the radius error when there is a geometric error. ΔR _XY is added. This ΔR _XY can be calculated as shown in the following [Equation 4] by modifying and approximating [Equation 3].

Substituting [Equation 3] into [Equation 4], the following [Equation 5] is obtained. Therefore, ΔR _XY is a circular locus including zero-order (radius error), first-order (center deviation), and second-order (elliptical shape) components.

Also, the sine-cosine function of n to the divided angle theta ₁ through? _N at regular intervals 360 ° has the following properties: [Expression 6].

Then, paying attention to the secondary sine component of [Equation 5], the property of [Equation 6] is used. The [Delta] R _xyi corresponding to each center position measurement values, C axis angle c 2 order sine components r _b2 by taking the average by multiplying quadratic sine value of _i is obtained when the indexing respectively, deform it Then, the following [Equation 7] is obtained, and the XY inter-axis perpendicular angle γ _YX can be obtained.

Further, the primary component is extracted. By _multiplying ΔR _XYi by the primary cosine value or sine value of the C-axis angle c _i, a primary cosine component r _a1 and a primary sine component r _b1 are obtained, which are transformed into the following [Equation 8] Is obtained.

  [Formula 3] is obtained by transforming [Formula 3] and obtaining the average of the X coordinate x ′ and the Y coordinate y ′ of each center position measurement value. This [Equation 9] is for obtaining the center of the circular locus, that is, the primary component, and can be used instead of [Equation 8].

On the other hand, as can be seen from the equation Z coordinates of the center position measurement values of the number 3], Z coordinate values 0 next to the C-axis angle c _i, is a circle having a primary cosine-sine component. In order to extract the primary component of this circle, the following [Equation 10] is obtained by multiplying the Z coordinate of each center position measurement value by the cosine value and sine value of the C-axis angle c _i when calculated. It is done. β _AY can be obtained from another method or from the measurement and formula described later and substituted to obtain β _CA and α _CA which are geometrical errors related to the C axis inclination error.

Next, the A-axis is tilted at any angle a _t other than 0 °, to measure the center position of the target ball 12 in one round n locations with indexing at any angle pitch C axis angle c from 0 ° (Indexing measurement). As before, the center position measurement value draws a circular locus, but the radius, that is, the distance from the intersection of the A axis and the C axis to each center position measurement value is R when there is no geometric error, When there is a geometric error, a radius error ΔR is added. ΔR is expressed by the following [Equation 11] obtained by modifying and approximating [Equation 3].

Substituting [Equation 3] into this [Equation 11] yields the following [Equation 12] ( _note that detailed equations of r _a0 , r _a1 , r _b1 , and r _a2 are omitted).

Similar to [Equation 5], [Equation 12] is a circular locus including 0-secondary components. Focusing on the quadratic sine component and multiplying ΔR _i corresponding to each center position measurement value by the quadratic sine value of the C-axis angle c _{i obtained} respectively, the following [Equation 13] is obtained. It is done. By substituting [Equation 7] or γ _YX obtained by another method for this [Equation 13], β _XZ can be obtained.

  Here, depending on the index angle of the A axis, it may not be possible to measure for one round due to interference between the spindle head 2 and the table 3 or the like, or the limitation of the movable range of each axis. [Equation 13] cannot be used when there is no center position measurement value for one round. In that case, the following [Equation 14] is obtained by solving the coefficient of [Equation 12] by the method of least squares using a plurality of center position measurement values.

Next, as shown in FIG. 8, indexing the C-axis angle c _t to 90 ° or -90 °, to measure the center position of the target ball 12 m locations by indexing the A-axis to any of a plurality of angles ( Indexing measurement). In many cases, the A-axis cannot mechanically rotate once, and even if it can, it cannot be measured by the touch probe 11, and therefore, measurement is performed within a certain angular range instead of one round. Focusing on the X coordinate of the center position measurement value, the following [Expression 15] is obtained from [Expression 3].

That is, it can be said that [Equation 15] indicates an arc including 0th and 1st order components. However, 90 ° C-axis angle _{c t,} Mixing changed and -90 °, also adds zero-order component which is dependent on _{c t.} The following [Equation 16] is obtained by obtaining the coefficient of each component of [Equation 12] by using the least square method or the like as a variable. Therefore, the geometric errors γ _AY and β _AY related to the tilt error of the A axis can be obtained by obtaining and substituting β _XZ by the above method or another method.

Next, attention is paid to the Y and Z coordinates of the center position measurement value. The radius error of the circular locus due to the geometric error, that is, the error ΔR _YZ of the distance from the center of the A axis to the sphere center can be obtained from the following [ _Equation 17].

Substituting [Equation 3] into this [Equation 17] gives the following [Equation 18]. Detailed expressions of r _a0 and r _c0 are omitted.

Therefore, ΔR _YZ is an arc locus including 0-second order components, and the following [Equation 19] is obtained by solving the coefficient of each component by the least square method or the like.

Here, obtaining the coefficient of [Equation 18] is the same as obtaining the radius and center position of the arc and the size of the elliptic component included in the arc. In general, the accuracy of obtaining the center position and elliptical component of an arc becomes worse as the arc angle is smaller. Therefore, as shown in FIG. 8, indexed to both the C-axis 90 ° (the center position of the target ball 12 _e p1 _{to e p4)} and -90 ° (the center position of the target ball 12 _e n1 _{to e n4)} To measure. Thereby, the arc angle can be widened and the identification accuracy can be increased. When it is not necessary to obtain α _XZ , the calculation may be performed by ignoring the secondary components r _a2 and r _b2 as 0 in [Equation 19].

  From the above, by measuring the center position of the target sphere 12 at a plurality of positions by the above-described method and calculating using the above-described mathematical formula, in addition to the eight geometric errors related to the rotation axes (A-axis and C-axis), the linear axis It is possible to identify eleven geometric errors in total with respect to (Y axis, X axis, Z axis). The remaining two need to be identified by another method.

The measurement result (identification value) obtained by the above method is obtained from the update of the geometric error correction parameter based on the previous measurement result , regardless of the numerical value (set value) of the geometric error correction parameter stored in the parameter storage area 26. The amount of change. The evaluation of the change can be used for checking whether or not the damage has been received (damaged or not) due to a change with time or a collision.

  In addition, as described above, after the geometric error is identified, the set geometric error correction parameter is updated in steps after S3. That is, after the geometric error is identified, first, in S3, the numerical value (setting value) of each geometric error correction parameter stored in the parameter storage area 26 is referred to (immediately after the operation of the geometric error measurement system is started). The setting value of the geometric error correction parameter is “0”). In subsequent S4, each geometric error correction parameter is recalculated by adding the set value of each geometric error correction parameter stored in the parameter storage area 26 to the identified numerical value. As described above, a value obtained by adding each set geometric error correction parameter to the identification value obtained as a result of the measurement becomes each newly set (updated) geometric error correction parameter (set value). The updated set value represents the geometric error itself of the machining center M. The evaluation of the set value after the update can be used for checking whether or not damage has accumulated.

  As described above, after calculating the geometric error correction parameter, in S5, threshold determination (evaluation of the identification result) is performed on the identification result (calculation result of the geometric error correction parameter). FIG. 9 is a flowchart showing the contents of the threshold determination process. The threshold determination is executed for all geometric error correction parameters.

  When determining the threshold value, a geometric error correction parameter evaluation loop is executed according to the procedure from S21. That is, in the geometric error correction parameter evaluation loop, first, in S22, the identification value of the geometric error correction parameter obtained by measuring the geometric error is acquired. Thereafter, in S23, the contents of the threshold value storage area 25 of the storage means 22 are referred to confirm the corresponding geometric error classification of the geometric error correction parameter for performing threshold determination. In S24, the geometric error classification is set. Get the threshold value.

  Then, in S25, when the geometric error correction parameter threshold acquired in S24 is compared with the identification value of the geometric error correction parameter obtained by measurement, and it is determined that the identification value exceeds the threshold (in S25, “ If “NO”, the alarm flag is validated for the corresponding geometric error correction parameter in S26. Thereafter, in S27, the geometric error correction parameter evaluation loop is terminated.

  On the other hand, if it is determined in S25 that the identification value is below the threshold value (if "YES" in S25), the geometric error correction parameter evaluation loop is terminated without enabling the alarm flag.

  In the threshold determination process, the above threshold determination (geometric error correction parameter evaluation loop) is executed for all geometric error correction parameters. After threshold determination is performed for all geometric error correction parameters, all geometric error correction parameters newly calculated in S6 in the geometric error measurement process (FIG. 5) (that is, previous measurement results). Threshold value for which a new geometric error correction parameter is set by executing the same threshold determination for the geometric error correction parameter updated based on the above (calculated by adding the currently measured identification value) If the value exceeds the value, the alarm flag is enabled for the geometric error correction parameter.

  After the threshold value determination of the identification value and the new geometric error correction parameter as described above is completed, an alarm flag is confirmed in S7. That is, if it is determined in S7 that there is no alarm flag, each geometric error correction parameter is automatically updated in S8 (that is, each geometric error correction parameter calculated based on the current measurement is updated). A message indicating that the geometric error correction operation has been completed is output on the monitor screen, which is the output means 32, and the processing is terminated.

  On the other hand, if it is determined in S7 that an alarm flag is present, in S10, the geometric error correction parameter (identified value or newly calculated geometric error correction) exceeding the threshold value is displayed on the monitor screen as the output means 32. By distinguishing the display of (parameter) from the display of other geometric error correction parameters (for example, by emitting light or blinking in a different color), it is notified that there is a geometric error correction parameter that exceeds the threshold. To do. Further, the geometric error classification (stored in the threshold storage area 25) including the geometric error correction parameter (identified value or newly calculated geometric error correction parameter) exceeding the threshold is displayed on the monitor screen. To do. In this case, an alarm sound is output from the speaker which is the output means 32. In such a case, automatic update of each geometric error correction parameter is not executed, and in step S11, control is performed so that the user can update each geometric error correction parameter manually (manually), and the manual update is performed on the monitor screen. A message indicating that it is possible is displayed and the process is terminated.

  As described above, the geometric error measurement system S considers the importance of the measurement result (identification value), performs threshold determination on the measurement result, and automatically sets the geometric error correction parameter only when there is no problem in the determination. If there is a problem in the update and determination, the user is informed by a message output, an alarm output, or the like without executing the automatic update.

<Effects of geometric error measurement system>
As described above, the geometric error measurement system S has a threshold storage area 25 that is a threshold setting means capable of setting a geometric error threshold in advance, and the identified geometric error exceeds the threshold set in the threshold storage area 25. In this case, the output unit 32 is a notification unit that notifies the situation, so that the state of the machine related to the change with time can be easily grasped, which is caused by a change with time of the machine or a measurement error. It is possible to effectively prevent a situation in which the machining accuracy of the machining center M is lowered due to execution of correction based on the inappropriate identification result.

  Further, the geometric error measurement system S has a parameter storage area 26 which is a geometric error update means capable of updating and storing a geometric error set value, and the measured value after the new geometric error is measured (after identification). In addition, a new geometric error setting value is calculated by adding the geometric error setting value stored in the parameter storage area 26, and the new geometric error setting value is set in the threshold storage area 25. When the threshold value is exceeded, the output means 32 notifies the situation, so that the state of the machine related to the accumulation of damage can be easily grasped. Therefore, according to the geometric error measurement system S, it is possible to effectively prevent a situation in which the machining accuracy of the machining center M is lowered due to execution of correction based on inappropriate identification results due to accumulation of machine damage or measurement errors. be able to.

  Furthermore, the geometric error measurement system S calculates a new geometric error setting value by adding the geometric error setting value stored in the parameter storage area 26 to the measured value after the measurement of the new geometric error. In addition, when both the newly measured geometric error and the new geometric error setting value calculated from the geometric error are below the threshold value, the calculated new geometric error setting value is stored in the parameter storage area 26. Is automatically updated as a new geometric error setting value. Therefore, according to the geometric error measurement system S, a situation in which the geometric error setting value is far from the true numerical value based on inappropriate identification due to a machine trouble or a measurement error does not occur, and an inappropriate geometric error setting is performed. A situation in which the machining accuracy of the multi-axis machine tool decreases due to the execution of the correction based on the value can be prevented very effectively.

  The geometric error measurement system S calculates a new geometric error setting value by adding the geometric error setting value stored in the parameter storage area 26 to the measured value after the new geometric error is measured. At the same time, if either one of the newly measured geometric error or a new geometric error setting value calculated from the geometric error exceeds the threshold value, a new calculated value is stored in the parameter storage area 26. It is possible to manually set a new geometric error setting value without automatically updating the geometric error setting value as a new geometric error setting value. Therefore, according to the geometric error measurement system S, the newly identified geometric error evaluation result can be surely recognized by the user.

  In addition, in the geometric error measurement system S, the threshold value storage area 25 can set a threshold value separately for each classification including a plurality of geometric error correction parameters. Therefore, an appropriate threshold value suitable for each geometric error classification can be set. Can be set easily within a short time.

<Example of geometric error measurement system change>
The geometric error measurement system according to the present invention is not limited to the aspect of the above embodiment, and can be appropriately changed as necessary without departing from the gist of the present invention. For example, the measurement system for geometric errors is not limited to a system for notifying that a measured value exceeds a threshold value by displaying on a monitor screen or outputting an alarm from a speaker. Various light emitting means such as LEDs and lamps are used. It is also possible to change to the one that notifies the situation by turning on and blinking in the mode.

  In addition, the geometric error measurement system is not limited to one in which the threshold setting unit can set a threshold separately for each classification including a plurality of geometric error correction parameters, as in the above embodiment, and for each geometric error correction parameter. It is also possible to change the threshold value to one that can be set.

  On the other hand, the geometric error measurement method using the geometric error measurement system is not limited to the embodiment described above, and can be appropriately changed as necessary. For example, the geometric error measurement method is not limited to a method of obtaining a geometric error by measuring the diameter and position of a spherical target (a jig to be measured) as in the above-described embodiment. It is also possible to change to a method for obtaining a geometric error by using a target having another shape and measuring a length of a predetermined side of the rectangular parallelepiped target or a distance between predetermined surfaces.

  Further, the measurement of the target installation position (center position) and diameter is not limited to the method of bringing the touch probe into contact with the target as in the above embodiment, and a method using a laser displacement meter that can measure the distance in a non-contact manner, It is also possible to change to a method of obtaining the center position and diameter of the target from the measured values of each displacement sensor by bringing three or more displacement sensors into contact with the target at the same time.

  Since the geometric error measurement system according to the present invention has excellent effects as described above, it can be suitably used as a geometric error measurement (identification) system in various multi-axis machine tools.

S ·· Geometric error measurement system M · · Machining center 1 · Bed 2 · Spindle head 3 · Table 4 · Cradle 5 · · Trunnion 11 · · Touch probe 12 · · Target ball 21 · · · Control device 22 · · · Storage means 25..Threshold storage area (threshold setting means)
26 .. Parameter storage area (geometric error update means)

Claims (5)

In a multi-axis machine tool having a plurality of linear axes and rotating axes, a sensor is provided on the spindle and a measurement target is installed on the table, and the coordinates of the measurement target are measured by the sensor under a plurality of positioning conditions. A geometric error measurement system for identifying a geometric error existing between adjacent axes using the measured value of
It is equipped with a geometric error correction system for correcting geometric errors of machine tools,
It has a geometric error update means that can update and store the geometric error setting value. After identifying the geometric error, add the geometric error after the previous identification to the identified numerical value and set the new geometric error setting. Update as a value , and identify the next geometric error as a change from the update of the geometric error ,
Threshold setting means capable of setting a geometric error threshold in advance;
A geometric error measurement system comprising: an informing means for informing the situation when the identified geometric error exceeds a threshold set in the threshold setting means.   2. The geometric error measurement system according to claim 1, wherein when the new geometric error setting value exceeds a threshold set in the threshold setting means, the notification means notifies the situation. If both the newly measured geometric error and the new geometric error setting value calculated from the geometric error are below the threshold,
The geometric error measurement system according to claim 1 or 2, wherein the geometric error update means automatically updates the calculated new geometric error set value as a new geometric error set value. If one of the newly measured geometric error or the new geometric error setting value calculated from the geometric error exceeds the threshold,
2. The geometric error updating means is capable of manually setting a new geometric error setting value without automatically updating the calculated new geometric error setting value as a new geometric error setting value. The geometric error measurement system according to any one of?   The geometric error measurement system according to any one of claims 1 to 4, wherein the threshold setting means can set a threshold separately for each classification including a plurality of geometric error correction parameters.

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