JP3396409B2 - Method and apparatus for measuring shape and size of work - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for measuring the shape and size of a work machined by a machine tool, and in particular, a measuring head having a measuring element is mounted on a main shaft to directly determine the coordinate values on the surface of the work. In three dimensions, at that time, the displacement of the probe center with respect to the spindle axis, that is, eccentricity,
Positional deviation of the center of the tracing stylus with respect to a prescribed reference position in the axial direction of the main shaft, that is, deviation, and further, the prescribed approach from when the tracing stylus of the measuring head contacts the workpiece or other object to be measured until a measurement signal is issued. And method for measuring the shape and size of a work capable of measuring the shape and size of the work with high accuracy even if a pressing margin corresponding to the pushing direction along the direction, that is, the normal direction is unavoidably included Is. In particular, the present invention, the approach direction to the measured object such as a workpiece,
In other words, a work shape measuring method and device that enables highly accurate work shape measuring even when using a measuring head in which the pressing allowance of the probe differs each time the normal direction changes in the three-dimensional space. And about.

[0002]

2. Description of the Related Art Machining of workpieces by machine tools, for example,
When machining a curved surface of a mold with a three-dimensional shape, the three-dimensional shape dimension of the workpiece is measured during the workpiece machining process to detect the machining state of the workpiece, and thus the machining to reach the desired geometric dimension can be performed. Grasping the degree of progress and processing accuracy is generally performed at the processing site. In the measurement of the three-dimensional shape dimension of the work in this case,
Each time, the work is carried in to the three-dimensional measuring machine outside the machine tool for measurement, which makes setting of the work on the measuring machine complicated, and when machining the work again after the measurement, There is also a disadvantage that it takes time to reset the work on the machine. Therefore, for a workpiece that is still attached to the table of the machine tool, a measuring head having a measuring element for exchanging the tool and the tool is attached to the spindle of the machine tool by a tool exchanging device or the like, and using the measuring head, Direct measurement of the geometry of the work as it is mounted on the table is also commonly performed as an efficient method.

[0003]

However, when the measuring head is mounted on the spindle of not only the machine tool but also the three-dimensional measuring machine outside the machine tool, the shape and dimension of the workpiece must be measured.
As an unavoidable factor associated with mechanical engagement between mechanical elements, eccentricity, deviation, etc. occur between the center of the measuring element of the measuring head and the axis of the spindle. However, the center of the measuring element of the measuring head is correctly positioned in the three-dimensional direction (X, Y, Z-axis directions) with respect to the axis of the spindle, and the center of the measuring element has no eccentricity or deviation with respect to the axis of the spindle. If the measurement is not performed after realizing, the position of the center of the contact point will deviate from the measurement target position on the work surface, and the scale of machine tools and measuring machines and encoders of the feed mechanism Even if a high-precision positioning function is used, it is impossible to measure the shape and dimension with high accuracy. For this reason, conventionally, for example, when the measuring head is mounted on the spindle of a machine tool to measure the shape and size of a workpiece, an indicator or the like attached to a bed or the like on the machine tool is used when the measuring head is mounted. A method has been adopted in which the so-called centering operation of aligning the center of the probe of the measuring head with the main axis of the spindle is performed, and then the shape and dimension of the workpiece are measured.

However, in alignment using an existing measuring instrument such as an indicator, it is difficult to achieve highly accurate alignment due to play inside the measuring head and contact pressure of the measuring head, and the spindle axis is There is an unavoidable deviation between the center of the contact point and the center of the contact point, and when measuring the curved surface of the workpiece, the contact point eventually measures a position on the curved surface of the workpiece that is offset from the target measurement point. This resulted in a decrease in measurement accuracy.

Moreover, in the case of a work having a complicated shape such as a curved surface of a die, since the measurement of the shape of the work is performed more than once during the machining process, the measurement of the shape is performed. It became extremely troublesome to carry out the process, resulting in a decrease in processing efficiency. On the other hand, for example, when a measuring head is mounted on the spindle of a machine tool to measure the shape and dimension of a workpiece, the contact point of the measuring head mechanically contacts the target measurement position of the workpiece to perform measurement. A non-contact type measuring head is used which obtains a measured value from a change in the amount of electricity such as a change in capacitance or a change in eddy current when the tip of the stylus approaches the measurement position of the workpiece. In the case of a stylus, it is equipped with a configuration that emits a measurement signal such as an electric signal indicating contact when a certain amount of pushing is performed in a fixed direction from the time of actual contact with the measurement position, and a non-contact stylus. Also in the above, the measurement signal is emitted when the above-described change in the amount of electricity reaches a constant level, that is, when the approaching motion amount until reaching a constant threshold value has elapsed. When the amount of pushing and the amount of approaching motion are collectively defined as a pressing margin, the contact point of the measuring head has a unique pressing margin. It is necessary to obtain the pressing margin of the measuring head, and to perform the correction process on the measured geometrical dimension of the workpiece to obtain the actual geometric dimension.

Particularly in the case of a relatively inexpensive and low-precision measuring head which is generally used, for example, a spherical shape, aside from the measuring head of a well-known high-precision measuring machine realized as a three-dimensional measuring machine. When the contact point of the probe moves toward the surface of an object to be measured, such as a workpiece, in the direction of the normal line, the direction of the normal line depends on the difference in the measurement position on the surface. Has a non-uniformity with a different press allowance for each, and the measurement error due to this non-uniformity of the press allowance is mixed into the workpiece such as a work having a complicated curved surface. , Has been recognized to adversely affect measurement results.

Therefore, in the three-dimensional measuring device, a measuring force is different depending on the contact direction of the measuring probe with the work, and a point having directionality is regarded as a roving characteristic, and a three-dimensional measuring method for improving the characteristic is specified. It is disclosed in Japanese Patent Publication No. 6-63760. This improved 3D measurement method
The surface of the reference sphere is divided into a plurality of areas, the measurement value is obtained by detecting the measurement signal by contacting the measurement probe in the normal direction to each divided area, and the virtual sphere formed from the measurement value and the actual reference The correction value corresponding to each divided surface is obtained from the sphere and stored, and when the work is measured next by the measurement probe, the position coordinates and the moving direction at the contact point with respect to the work are detected, and the moving direction A method is disclosed in which a correction value corresponding to the moving direction (normal direction) at the time of measuring the corresponding reference sphere is read out, and the measurement value when the workpiece is contacted and measured is corrected by this correction value. .
However, in this method, in the case of a work having a complicated curved surface shape, if the divided area of the reference sphere is subdivided infinitely and precise correction data is not held, when the work is actually measured, the It is difficult to obtain the roving correction value corresponding to the measurement direction, that is, the pressing allowance correction value, and there is a problem that the storage capacity becomes huge.

Therefore, in view of various problems in the above-mentioned conventional technique, the main object of the present invention is to measure the shape and size of the workpiece to be processed by using the probe of the measuring head mounted on the spindle. In this case, in addition to the eccentricity and deviation described above between the spindle axis and the center of the contact point, it is possible to obtain highly accurate measurement results even if there is an uneven pressing margin characteristic. An object of the present invention is to provide a shape measuring method and apparatus.

Another object of the present invention is that the measuring head of the measuring head has a different press allowance depending on the difference of the measuring directions, and in particular, the approaching direction in which the measuring element is taken infinitely in three-dimensional space from any one point. Or, the shape and dimension of the workpiece can be measured not only when the envelope characteristic is smooth when the approaching motion is performed along the normal direction, but also when the irregular curved surface with a curved line is used as the envelope surface. When performing, regardless of whether the measuring head is contact type or non-contact type, the press allowance of the probe corresponding to the measuring direction to the work is easily obtained from the press allowance data of the probe obtained by using the calibration means in advance. The present invention provides a method and apparatus for measuring the shape of a workpiece, which is capable of realizing highly accurate measurement of the shape of the workpiece by correcting the measured coordinate value of the workpiece by the calculated pressing allowance. .

[0010]

In view of the above-mentioned object of the present invention, the present invention is known in a method for measuring the shape and size of a workpiece, in which the coordinate values of the surface of the workpiece are measured by a probe of a measuring head mounted on a spindle. By asymptotically moving the tracing stylus of the measuring head along each normal direction toward a plurality of calibration measuring points of a predetermined calibrating means having dimensions, the pressing margin PLn in each normal direction of the tracing stylus is obtained. Obtained and stored the press allowance PLn in each normal direction of the probe of the measurement head obtained in association with each normal direction, the position of the measurement point of the workpiece and the measurement start point corresponding to the measurement point Based on a measurement procedure created in advance including a movement command to the position, the spindle and the workpiece are relatively moved, the probe of the measurement head is positioned at the measurement start point, and the measurement of the measurement head is performed. Measure the child The coordinate value (x, y, z) of the measurement point at the time of receiving the measurement signal at the measurement point is detected by the asymptotic movement along the normal direction from the starting point to the measurement point, and the measurement is performed. A plurality of normal directions near the point are selected, and a plurality of normal directions corresponding to the selected normal directions are selected.
From the stored press allowance, the press allowance PL corresponding to the normal direction at the time of measuring the workpiece is calculated, and the calculated press allowance is obtained with respect to the coordinate values (x, y, z) of the fetched measurement points. The coordinate values (Hx, H
y, Hz), and the coordinate value (H
(x, Hy, Hz) to provide a method for measuring the shape and size of a work by calculating the measured value of the shape and size of the work.

Further, according to the present invention, in the method for measuring the shape and size of a work, in which the coordinate values of the surface of the work are measured by the measuring head of the measuring head mounted on the main spindle, the center of the measuring head of the measuring head mounted on the main spindle is measured. Position coordinate value (x ₀ ,
y ₀ , z ₀ ) and an eccentricity amount (ΔX, ΔY) corresponding to a deviation between the axis of the main shaft and a deviation amount (ΔZ) corresponding to a deviation from a predetermined reference position in the axial direction of the main shaft,
The eccentric amount calculated (ΔX, ΔY), and stores the deviation amount ([Delta] Z), the measurement of the measuring head along the normal direction toward the plurality of calibration measurement point of a predetermined calibration means having a known dimension The push allowance PLn in each normal direction of the probe is obtained by asymptotically moving the probe, and the obtained press allowance PLn in each normal direction of the probe of the measuring head is associated with each normal direction. Based on a measurement procedure created in advance that includes a movement command to the position of the measurement point of the work and the position of the measurement start point corresponding to the measurement point, and relatively moves the spindle and the work. , The measurement head of the measuring head is positioned at the measurement start point obtained by taking in the stored eccentricity amount (ΔX, ΔY) and deviation amount (ΔZ) at the position of the measurement start point, From the obtained measurement start point to the measurement point The coordinate values (x, y, z) of the measurement point when the measurement signal at the measurement point is received are moved asymptotically along the direction of the normal line and detected, and the plurality of values in the vicinity of the measurement point are acquired. A normal direction is selected, a pressing margin PL corresponding to the normal direction at the time of measuring the workpiece is calculated from the plurality of stored pressing margins corresponding to the selected plurality of normal directions, and the taken-in PL is fetched. Coordinate value (x,
For y, z), the coordinate value (Hx, Hy, Hz) of the measuring point corrected by the obtained pressing margin PL, the stored eccentricity amount (ΔX, ΔY) and the deviation amount (ΔZ) is obtained, The present invention provides a method for measuring the shape and size of a work, in which the measured value of the shape and size of the work is calculated from the coordinate values (Hx, Hy, Hz) of the corrected measurement points.

Further, the present invention is a work shape measuring apparatus for measuring coordinate values of a surface of a work by means of a measuring head of a measuring head mounted on a main shaft, wherein the measuring head of the measuring head has a predetermined dimension. A calibration pressing margin calculating means for determining a pressing margin PLn in each normal direction of the probe by asymptotically moving along each normal direction toward the plurality of calibration measurement points of the calibration means, and the obtained measurement. The pressing margin storage means for storing the pressing margin PLn in each normal direction of the head tracing element in association with each normal direction, and the position of the measurement point of the workpiece and the measurement start point corresponding to the measurement point. Based on a measurement procedure created in advance including a movement command to a position, the spindle and the workpiece are relatively moved, the probe of the measuring head is positioned at the measurement start point, and from the measurement start point. The measurement Measuring element moving means for asymptotically measuring and moving along the normal direction toward the measuring element, and the measuring element moving means moves the measuring element of the measuring head asymptotically along the normal direction from the measurement starting point to the measuring point. Move
Measuring coordinate value reading means for reading coordinate values (x, y, z) of the measuring point when a measuring signal at the measuring point is received, and a plurality of normal directions in the vicinity of the measuring point are selected,
A plurality of stored data corresponding to the selected plurality of normal directions
The pressing margin calculating means for obtaining the pressing margin PL corresponding to the normal direction at the time of measuring the workpiece from the pushed pressing margin, and the coordinate value (x, y, y) of the measuring point read by the measuring coordinate value reading means. z), the coordinate value (H) of the measurement point corrected by the pressing margin PL obtained by the measuring pressing margin calculating means.
x, Hy, Hz) for obtaining the coordinate value (Hx, Hy, Hz) of the measurement point of the workpiece corrected by the corrected coordinate value computing means. The present invention provides a work shape measuring device configured to calculate and measure.

Further, according to the present invention, in a work shape measuring apparatus for measuring coordinate values of a surface of a work by means of a measuring head of a measuring head mounted on a main shaft, a center of a measuring head of the measuring head mounted on the main shaft is measured. Coordinate value of position (x ₀ ,
y ₀ , z ₀ ) and an eccentricity amount (ΔX, ΔY) corresponding to a deviation amount between the axis of the main shaft and a deviation amount (ΔZ) corresponding to a deviation amount from a predetermined reference position in the axial direction of the main shaft. With the deviation amount calculating means and the eccentricity / deviation amount calculating means
Calculated eccentricity (ΔX, ΔY) and deviation and eccentricity, deviation storing means for storing ([Delta] Z), the measuring element of the measuring head into a plurality of calibration measurement point of a predetermined calibration means having a known dimension A calibration pressing margin calculating means for obtaining a pressing margin PLn in each normal direction of the probe by asymptotically moving along each of the facing normal directions, and the measuring head obtained by the calibration pressing margin calculating means . Pushing margin storage means for storing the pushing margin PLn in each normal direction of the probe in association with each normal direction, and the position of the measurement point of the work and the position of the measurement start point corresponding to the measurement point. Based on a measurement procedure created in advance including the movement command, the spindle and the workpiece are moved relative to each other, and the tracing stylus of the measuring head is stored at the position of the measurement start point in the eccentricity / deviation amount storage means. Eccentricity (ΔX, Δ
Y) and a deviation amount (ΔZ) are taken in to position at a measurement start point obtained, and a probe moving means for asymptotically moving along the normal direction from the obtained measurement start point to the measurement point. The measuring point when the measuring signal of the measuring head is asymptotically moved along the normal direction from the obtained measurement starting point to the measuring point by the measuring element moving means, Measurement coordinate value reading means for reading the coordinate values (x, y, z) of a plurality of normal lines , and a plurality of normal line directions in the vicinity of the measurement point are selected, and a plurality of pressing margins corresponding to the selected plurality of normal line directions. Recorded by storage means
A pressing margin calculating means for measuring the pressing margin PL corresponding to the normal direction at the time of measuring the workpiece from the stored pressing margin, and coordinate values (x, y, x) of the measuring point read by the measuring coordinate value reading means. z) is corrected by the pressing margin PL obtained by the measuring pressing margin calculating means and the eccentricity amount (ΔX, ΔY) and the deviation amount (ΔZ) stored in the eccentricity / deviation amount storing means. A coordinate value calculation means for obtaining the coordinate value (Hx, Hy, Hz) of the point, and the coordinate value (H) of the measurement point of the workpiece corrected by the correction coordinate value calculation means.
(x, Hy, Hz) The present invention provides a workpiece shape dimension measuring device configured to calculate and measure the shape dimension of the workpiece.

[0014]

[Function] To obtain the press allowance PL (PL _X , PL _Y , PL _Z ) by the calculation method when the probe of the measuring head mounted on the spindle of the machine tool or the measuring machine actually measures the shape dimension of the workpiece. The plurality of pressing margin data are obtained using a calibration means such as a calibration sphere having a known radius, and are stored in the storage means in association with the approach direction (normal direction) at the time of measurement.

The pressing margin data has, for example, a known radius dimension (R), a well-known calibration sphere used for dimensional calibration and position calibration is set on a table, and a plurality of calibrated spheres on the spherical surface are provided. For each point, position the probe at the measurement start point for each of the plurality of points, measure the calibration sphere radius by moving the probe closer to the measurement start point along the normal direction, and measure the probe head of the measurement head. (R + r)-(R) from the known radius (r), the measured radius (Rs) of the calibration sphere, and the known radius (R).
s) = Pushing allowance PLn is obtained, and the process of finding such a pushing allowance PLn is repeated at a plurality of points on the calibration spherical surface,
Pressing allowance data is obtained in, for example, a table format that has a one-to-one correspondence with the approach direction (normal direction) of the contact point, and the pressing allowance data table is stored in an appropriate pressing allowance storage means. The step of obtaining the press allowance data by using the calibrating means such as the calibrating sphere may be programmed in advance as a fixed calibrating procedure and executed according to the calibrating program.

After obtaining the press allowance data of the probe of the measuring head mounted on the spindle as described above, the step of measuring the shape and size of the work is performed using the measuring head mounted on the spindle. In the process of measuring the shape and dimension of the work, a plurality of measurement points designated in advance by the measurement program or the like on the measurement surface of the work (the principle of the measurement method of the present invention does not change even if only one measurement point is required. The position of the measuring element center of the measuring head is set to the measurement starting point defined on the normal line to the measuring point by the movement of the main axis as described above. At this time, the normal line may be a normal line obtained by calculation in advance with respect to the measurement point selected for the shape designed for machining of the workpiece, and the coordinate values of several points in the vicinity of each measurement point of the workpiece may be actually calculated. Obtained by measuring with the probe of the measuring head, find the normal line standing on the plane including the measurement point determined from the coordinate values of the obtained several points, and use the thus obtained normal line in the actual measurement of each measurement point. You may make it a line.

Thus, the center of the contact point is set to the position of the measurement starting point.
After the placement is completed, work piece centered along the specified normal line
Of contact type or non-contact type by approaching to the measurement point of
The coordinate value of the fixed point is obtained by actual measurement. In this case,
At the stage of obtaining the value, if the contact type is used,
Says it will receive the measurement signal when pushed by the minute
There is no end. Coordinate value of the measurement point measured in this way
For the (X, Y, Z), the press allowance data table described above
From the multiple points close to the above normal direction at the measurement point of the workpiece
Select (for example, four) normal directions and select the selected normal direction.
Depending on the press allowance PL1, PL2, PL3, PL4
Pushing allowance PL (PL _X, PL_Y, P
L_Z) Is calculated arithmetically. That is, this algorithm is an example
For example, the press allowances PL1, PL2, P corresponding to the four normal directions
Positions of 4 points on the surface of a calibration sphere exhibiting L3 and PL4
Due to the positional relationship, it has the same normal direction as the approach direction when measuring the workpiece.
If the pushing margin of the point corresponding to the measured point is calculated proportionally
good.

The press allowance PL (PL _X , P
L _Y , PL _Z ) is corrected to the coordinate values (x, y, z) of the workpiece measurement point by the press allowance components distributed in the three-dimensional axial directions, so that the coordinates of the measurement point in the three-dimensional coordinate system are corrected. The values (H _X , H _Y , H _Z ) are obtained.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on the embodiments shown in the accompanying drawings. FIG. 1 is a block diagram showing the overall configuration of a measuring apparatus used for carrying out the method for measuring the shape and dimension of a work according to the present invention, and FIG.
With the measuring head of the measuring head mounted on the spindle eccentric with respect to the spindle axis, deviated, and with the pressing margin different in the approaching direction, the measuring target point of the workpiece is measured by the measuring method according to the present invention. FIG. 3 and FIG. 4 are schematic explanatory views for explaining the measurement process when performing the measurement, FIG. 3 and FIG. 4 are flow charts when performing the shape dimension measurement of the work according to the present invention, and FIG. Using the reference calibration sphere as a calibration means, for example, a schematic explanatory view for explaining a step of detecting the pressing margin of the probe of the measuring head installed on the table of the machine tool and mounted on the spindle. Reference numeral 6 denotes a pressing allowance measuring point for a plurality of pressing allowance measuring points on the surface of the reference calibration sphere, by bringing the contact point of the measuring head close to each of the pressing allowance measuring points in the direction of the normal line that is uniquely determined. Position of,
Therefore, an explanatory view for explaining the process of obtaining the press allowance of the probe in correspondence with the normal direction and obtaining the press allowance data table, FIG. 7 and FIG. 8 show the press allowance at the target measurement point P ₁ of the workpiece as a reference calibration. Multiple points Q ₁ , Q of the press allowance data table obtained using a sphere
₂ , a schematic explanatory view for explaining a process of calculating based on a plurality of pressing margins obtained from Q ₃ , Q ₄ , FIG. 9 shows points P ₁ , Q
FIG. 10 is a plan view showing a state in which ₁ , Q ₂ , Q ₃ , and Q ₄ are plotted on the surface of a reference calibration sphere, and FIG. 10 is a probe (contact type of a contact type) which a measuring head mounted on a spindle of a machine tool generally has. When measuring the measurement target point of an object to be measured such as a workpiece with a spherical measurement feeler), when the spindle axis center and the center of the contact point are correctly aligned, the measurement start point and the measurement target point are the same point. FIG. 11 is a schematic explanatory view for schematically explaining the situation in the case of approaching (approaching) in the direction of the normal line standing upright. FIG. FIG. 12 is a schematic explanatory view for schematically showing the amount, and FIG. 12 is a diagram showing an object to be measured such as a work piece by a measuring element (an example of a contact type spherical measuring feeler) included in a measuring head mounted on a spindle of a machine tool. When measuring the measurement target point of the object , It is an outline for schematically explaining the situation when approaching (approaching operation) from the measurement start point to the measurement target point in the normal direction standing at the same point while the spindle axis center and the center of the contact point do not match. FIG.

Now, in general, during a step of performing machining of a work set on a table by a machine tool, in particular, an NC machine tool that performs machining while performing tool exchange according to a predetermined NC program, By mounting a measuring head having a tracing stylus instead of a tool on the spindle of a machine tool to measure the shape and dimension of a work piece as it is installed on a table, it is usually at the processing site.
It is running. In measuring the shape and dimensions of such a workpiece, the relative movement of the feed mechanism is performed between the spindle of the machine tool and the table on which the workpiece is mounted, and the measuring head of the measuring head mounted on the spindle is used as the target of each workpiece. Try to get closer to the point. Therefore, when measuring the shape and dimension of the work by the measuring head mounted on the spindle of the machine tool, a measuring program is created with the spindle center as a reference. On the other hand, when the measuring head is mounted on the spindle of a coordinate measuring machine outside the machine tool and the measuring point of the measuring head measures the target measuring point of the workpiece, the center of the measuring head is measured. It is general to perform the measurement with the measuring head on the basis of.

First, as shown in FIG. 10, in an example having a measuring head mounted on the main shaft 9, the contact type probe 11 is mounted with its center properly aligned with the axial center of the main shaft 9. Consider when being done. In this case, the spindle 9
And the work W are used to approach the measurement target point P (x, y, z) of the work W from the normal direction V toward the measurement head 11 of the measurement head toward the measurement target point P. When operated, the tracing stylus 11 correctly contacts the measurement target point P in accordance with the relative movement of the spindle 9, so that the three-dimensional coordinate P (x, y, z) of the measurement target point P is successfully detected. be able to. Therefore, if three-dimensional coordinate values are detected for many measurement target points P of the work W, the three-dimensional shape dimensions of the work W can be measured with high accuracy from these coordinate values.

However, in general, when the measuring head is mounted on the main shaft 9 of the machine tool by an appropriate mounting device such as a tool changing device, the shaft center of the main shaft 9 and the measuring head 11 of the measuring head are completely correct. It is difficult to obtain a state in which the center coincides with the mechanical structure, and in addition, the center of the probe 11 generally deviates from the axis of the main shaft 9 due to play inevitably included in the measuring head. ing. FIG. 11 illustrates and shows the state of occurrence of such a shift.

As shown in FIG. 11, the deviation between the axis of the main shaft 9 and the center of the probe 11 is the amount of deviation (ΔX, ΔY) between the two in two-dimensional coordinates and the measurement program in the axial direction of the main shaft 9. The amount of deviation from the reference position (Δ)
Z) and. The deviation amount (ΔX, ΔY) corresponds to the eccentricity amount, and the deviation amount (ΔZ) corresponds to the deviation amount. The relative movement between the spindle 9 and the work W was executed in order to detect the coordinate value of the measurement target point P of the work W by the tracing stylus 11 in the state having such deviation amounts (ΔX, ΔY, ΔZ). The situation is shown in FIG. That is, the spindle 9
Of the measuring head 11 by the relative movement between the workpiece and the workpiece W.
Is moved toward the measurement target point P of the workpiece W along the predetermined normal direction V, the tracing stylus 11 moves the measurement target point P
The coordinate value of the point P ′ on the surface of the work W deviated from is detected. It goes without saying that not only the deviations in the X and Y axis directions shown in FIG. 12, but also the detection deviations based on the deviation amount (ΔZ) in the axial direction of the main shaft 9 of the probe 11 are mixed. Therefore, when the shape dimension of the workpiece W is measured by obtaining the coordinate values of a large number of points P ′ having such a positional deviation, the shape dimension measurement value naturally includes an error.

In the process of detecting the contact point between the probe 11 and the workpiece W shown in FIGS. 10 and 12, the probe 1 is generally used.
No. 1 does not immediately issue a detection signal at the time of contact with the work W, but the detection signal is issued after a certain amount of pushing toward the inside of the work W along the normal direction V. The amount is the pushing amount, and the pushing amount between the individual measuring elements 11 generally has large and small variations. On the other hand, when an approach operation is performed along the normal line direction V, various pressing margins are often exhibited depending on the difference in the normal line direction. In particular, although the cost is low, measurement of a measuring head manufactured with low accuracy is performed. In the child 11, this tendency is remarkable. Therefore, it is impossible to measure the shape and size of the work W with high accuracy unless the characteristics of the pressing margin of such a probe are also taken into consideration.

According to the present invention, for example, when the geometrical dimensions of the processed work W are measured by a measuring head mounted in exchange for a tool on the spindle 9 of the machine tool on which the processing is performed,
Even if the center of the measuring element 11 of the measuring head with respect to the axis of the main shaft 9 is mounted so as to include the above-mentioned eccentricity and deviation amount, and the pressing margin of the measuring head differs depending on the difference in the measuring direction, it is high. An object of the present invention is to provide a method and an apparatus capable of accurately measuring the shape and size of the work W.

Here, referring to FIG. 1, as one embodiment of the present invention, a measuring head 1 mounted on a spindle 9 of a machine tool M.
Consider the case where the shape dimension of the work W is measured by 0. The machine tool M performs machining of the work W on the table 12 according to, for example, an NC machining program (not shown). Therefore, the machine tool M includes a Z-axis feed mechanism Fz including a feed motor that feeds the spindle 9 in the Z-axis direction, and feed motors that feed the table 12 in the X-axis direction and the Y-axis direction. Included X-axis direction, Y
An axial feed mechanism Fx, Fy is provided. And
These three-axis feed mechanisms Fx, Fy, Fz are scale devices, encoder devices, etc. that send position signals indicating the position of the spindle 9 in the Z-axis direction and the position of the table 12 in the X-axis direction and the Y-axis direction, respectively. Needless to say, it is equipped with.

On the other hand, during the machining process of the work W, the measuring head 10 is mounted on the spindle 9 of the machine tool M in place of the tool by a tool exchanging device (not shown) or the like, and the measuring head of the measuring head 10 has the same measuring head. The shape dimension of the workpiece W is measured by 11. The measurement of the shape dimension of the work W is performed by a measurement program MRP created in advance based on the design and machining data of the work W, and this measurement program MRP makes a plurality of measurements on the work W with reference to the axis of the spindle 9. The measurement procedure including the target point P, the normal direction V at each measurement target point, the approach start point of the center of the probe 11 to each measurement target point P, etc. is recorded. Further, the measurement program MRP may include a calibration procedure for obtaining a pressing margin data table of the tracing stylus 11 of the measuring head 10 by using a calibration means described later.

Then, the various measuring steps of measuring the shape and dimension of the work W and creating the press allowance data table of the probe 11 of the measuring head 10 are performed based on the commands in the measuring procedure and the calibration procedure included in the measuring program MRP. To be done.
That is, the measurement procedure command of the measurement program MRP is
It is read by the measurement program reading unit 13 and converted into measurement data. The measurement data interpreted by the measurement program reading unit 13 is input to the operation command unit 15, and at this time, the operation command unit 15 controls the axial movement of the feed mechanisms Fx, Fy, Fz of the machine tool M in each axial direction. The operation command based on the measurement data is input to the axis movement control unit 17. Therefore,
The axis movement control unit 17 sends a movement control signal in each axis direction to the feed mechanisms Fx, Fy, and Fx in each axis direction according to the operation command.
Fz is sent to drive the feed operation, and at the same time, the start of the axial movement is output to the position detection unit 19 and the measurement signal detection unit 21 to drive the position detection operation and the measurement signal detection operation. The operation command unit 15 is also connected to an eccentricity / deviation amount storage unit 41, which will be described later, and is configured to send an operation command in consideration of the eccentricity / deviation amount to the axis movement control unit 17.

On the other hand, the apparatus for measuring the shape and size of the work W according to the present invention, when performing the measurement of the shape and size of the work W in accordance with the measurement program MRP, presses the probe head 11,
If necessary, correction data such as the eccentricity amount and the deviation amount are first obtained, and then the three-dimensional coordinate values of the plurality of measurement target points P are detected through the detection operation of the tracing stylus 11, and the correction data and coordinate detection values thereof are detected. A correction amount calculation unit 30 and a data storage unit 4 that function to calculate and measure the shape and size of the work W from the above.
0, a measurement value calculation unit 50, and a measurement result output / display unit 60 are provided.

The correction amount calculation unit 30 is provided to calculate the correction amount such as the eccentricity / deviation amount of the tracing stylus 11 and the pressing margin according to the operation command from the operation command unit 15 described above. The quantity calculation unit 31 is connected to the position detection unit 19 and the measurement signal detection unit 21 described above, and uses the non-contact type tool tip position measurement device described later to convert the data of the center coordinates of the probe 11 into the position detection unit 19. Input, the eccentricity amount and the deviation amount of the probe 11 with respect to the axis of the main shaft 9 is calculated based on the input from the calibration press margin calculation unit 33. When measuring the predetermined dimension of the calibrating means with the calibrating means by moving the calibrating means close to each other from a plurality of normal directions, the metric based on the detection data from the position detecting section 19 and the measurement signal detecting section 21. 11 seeds It is composed of 押代 PLn corresponding to the normal direction so as determined by calculation.

The eccentricity and deviation amount of the tracing stylus 11 of the measuring head 10 calculated by the correction amount calculation unit 30 are stored in the eccentricity / deviation amount storage unit 41 of the data storage unit 40. The table is stored in the press allowance data storage unit 43. Further, after the above-mentioned eccentricity and deviation amount and the press allowance data table are obtained, it is finally the work W.
In the process in which the measurement process of the geometrical dimensions is performed, the measurement coordinate value detection unit 51 of the measurement value calculation unit 50 outputs the three-dimensional measurement target point P output from the measurement signal detection unit 21 and the position detection unit 19 described above. The eccentricity / deviation amount correction unit 53 receives the coordinate value data and reads the eccentricity / deviation amount storage unit 41 from the eccentricity / deviation amount storage unit 41 with respect to the received three-dimensional coordinate values of each measurement target point P. Correct by. Further, based on the press allowance data table read out from the press allowance data storage unit 43 by the press allowance correcting unit 55, the measuring press allowance calculating unit 54 has the presser head 11 of the measuring head 10 with respect to the measurement target point P. The margin PL is calculated and sent to the margin correction unit 55 to correct the margin, thereby obtaining the correct three-dimensional coordinate value of the measurement target point P, and the work shape dimension calculator 57.
To each measurement point. Then, the workpiece shape dimension calculation unit 57 calculates the shape dimension of the work W from the correct three-dimensional coordinate values of each of the plurality of measurement target points P, completes the measurement, and measures the calculated shape dimension data of the work W. The result is output / displayed to the outside of the apparatus via the display unit 60.

FIG. 2 shows that when the method of measuring the shape and dimension of the work W according to the present invention is carried out on a machine tool, the center of the contact point 11 has an eccentricity or deviation with respect to the axis of the spindle 9.
In addition, the measurement process until the probe 11 detects the three-dimensional coordinate value of the measurement target point P of the work W in the state where the probe 11 has different pressing margins in the approaching direction to the measurement point will be described. .

In FIG. 2, when starting measurement of the measurement target point P of the work W from the arbitrary position (a) of the spindle 9 to which the measuring head 10 is attached, the measurement is started from the arbitrary position (a). Moved and positioned to point (b).
Positioning to this measurement start point (b) is performed by the measurement program M
The measuring element 11 with respect to the measurement starting point P designated by RP
In consideration of the eccentricity and deviation, the positioning is performed with a correction operation so that the center position of the probe 11 is located at an appropriate measurement start point with respect to the measurement target point P.

Next, a passing point (c) from the measurement starting point (b) along the normal direction (assuming the normal vector in the three-dimensional coordinate system to be (l, m, n)) with respect to the measurement target point P.
The approach operation is performed via. This approaching operation is, of course, the feed mechanism Fx, Fy, F in each feed axis direction of the machine tool M.
It goes without saying that the relative movement between the spindle 9 and the workpiece W is performed by the axial movement of the three-axis feed mechanism including z.

Eventually, the contact point 11 is a position at which the measurement target point P on the workpiece W is detected in a contact type or a non-contact type, that is, in the contact type, it is a position at which the measurement target point P geometrically contacts the measurement target point P. In the formula, the detection position (d) corresponding to the position where the change of the eddy current or the capacitance theoretically starts is reached. When the probe 11 reaches the position (e) further pushed in by the amount corresponding to the pressing margin from the detection position (d), a measurement signal, a so-called skip signal, is emitted from the measuring head 10. Such a measurement signal is detected by the measurement signal detection unit 21 shown in FIG. 1, and the position detection unit 19 responds to the measurement signal by the position detection device such as a scale or encoder associated with each feed mechanism Fx, Fy, Fz. From this, the coordinate value (x, y, z) of the measurement target point P is detected.

In the process of detecting the three-dimensional coordinate values (x, y, z) of the measurement target point P described above, the spindle 9 of the machine tool M is used.
Performs relative movement with respect to the work W from a position deviated from the measurement start point (b) designated by the measurement program MRP so that the center of the probe 11 approaches the measurement target point P in the normal direction. Since it is operating, the eccentricity of the probe 11 and the amount of deviation corresponding to the amount of deviation are mixed in the coordinate value of the point P detected as described above. Also, the press allowance is included. Therefore, the present invention corrects the eccentricity, the deviation amount, and the pressing margin to obtain the correct three-dimensional coordinate values (Hx, Hy, Hz) of the measurement target point P with the axis of the spindle 9 as a reference. is there.

That is, the measurement detected according to the measurement signal
As described above, the three-dimensional coordinate value of the fixed target point P is set to P (x,
y, z), and the correct three-dimensional coordinate value is P (Hx, Hy, H
z), eccentricity amount (ΔX, ΔY), deviation amount (ΔZ),
PL for PL (PL_X, PL_Y, PL _Z).
Then, the vector of the normal line at the measurement target point P is (l,
m, n), the correct three-dimensional coordinate value P (Hx, H
y, Hz) is given by the following equation.

[0038]

[Equation 1] In the present invention, the coordinate values of the three-dimensional coordinates of each measurement target point P are shown in FIG.
The position detection unit 1 according to the measurement signal of the measurement signal detection unit 21 of
When detected from 9, the three-dimensional coordinate value of each point P is input to the measurement coordinate value detection unit 51 in the measurement value calculation unit 50, and the eccentricity and deviation of the probe 11 are calculated according to the above equations (1) to (6). The correction of the amount and the correction of the press allowance are performed, and the work shape dimension calculation unit 57 performs the operation of plotting the coordinate values of the plurality of correct measurement target points P in the three-dimensional coordinate system to correctly measure the shape dimension of the work W. You get the value. As described above, according to the present invention, the center position of the measuring head 11 of the measuring head 10 has an eccentricity or deviation with respect to the axis of the main shaft 9, and the measuring head 11 is different depending on the approaching direction to the measuring point. Even if there is a margin, it is possible to obtain a correct measured value of the shape dimension of the work W, so that it is possible to realize high accuracy of measurement. 3 and 4 are flow charts showing the measuring steps S1 to S10 in the measurement of the shape and dimension of the work W.

The measuring steps S7 to S1 shown in FIG.
In the process of 0, the three-dimensional coordinate value is detected and corrected individually for each of the plurality of measurement target points P1 to Pn on the surface to be measured of the work W, that is, the measurement points P1 to Pn. Although it is described that the measurement process is repeated a plurality of times, it goes without saying that the three-dimensional coordinate values regarding the plurality of measurement target points P1 ... Pn are first detected and then the probe 11 is used.
The eccentricity amount and the deviation amount of the
Further, the pushing margin is fetched from the data storage unit 40, and the pushing margin of each measurement target point P1 ... Pn is calculated in the measuring pushing margin calculating unit 54, and the individual coordinate values are sequentially corrected by the obtained pushing margin. However, it goes without saying that it is good.

In the step S8 shown in FIG. 4, the normal direction in the case of performing the approaching operation of the respective measurement target points P1 to Pn is the work W in advance at the stage of creating the measurement program MRP.
Alternatively, the normal direction may be determined from the shape data to be designed and processed, and the vector (l, m, n) may be input in the program. Further, as shown in FIG. In the process of measuring the measurement target points P1 to Pn, for example, the coordinate values of three points which are selected in advance in the vicinity of the measurement target point P1 are directly measured using the tracing stylus 11, and these three points are measured. The normal line VL that is set up on the narrow plane M including the measurement target points formed by the coordinate values may be obtained as the normal line direction in the approaching movement of the measurement target point P1. In this case, although not shown, the correction amount calculation unit 30 of FIG. 1 is appropriately provided with a calculation unit for calculating a vector in the normal direction, and the calculated vector in the normal direction is stored in the data storage unit 40. A normal vector storage unit for storing may be provided.

Next, at the measuring step S2 shown in FIG. 3, the center position (x ₀ ,
A method and means for obtaining x ₀ , z ₀ ) will be briefly described. That is, the center position (x ₀ , y ₀ ,
When measuring z ₀ ), for example, the position of the tip of the probe 11 is detected using a non-contact type tool tip position detection device or the like provided on the table 12 or the like of the machine tool M to measure the probe. The center position can be easily obtained by obtaining the outer diameter dimension of 11 and the position of the most distal end point. Such a non-contact type tool tip position detecting device is already known in the market and the like, but as a typical example, it is disclosed in Japanese Patent Application No. 8-311432 filed by the applicant of the present application. There is something. That is, in the device disclosed in Japanese Patent Application No. 8-311432, one light beam is projected between the light emitter and the light receiver on the rotatable swivel table installed on the table of the machine tool. A measuring signal or a skip signal is transmitted when the light beam is cut off, and the light beam is cut off by the relative movement of the machine tool between a known master tool and a practical tool using such one light beam. An apparatus for detecting the tool tip position of a practical tool is disclosed by using the coordinate value of the master tool in each of the three-dimensional coordinate values as a reference by moving the tool. In addition to the non-contact type tool tip position detecting device using such a light beam, various tool measuring devices using a laser beam and a line sensor are well known. Is used, the tip position and the outer diameter dimension of the measuring head 11 of the measuring head 10 according to the present invention can be detected and easily measured.
The center position (x ₀ , y ₀ , z ₀ ) of can be obtained. If the center position (x ₀ , y ₀ , z ₀ ) of the probe 11 thus obtained is compared with the known axial center of the main shaft 9 in the three-dimensional space, the probe in the measurement step S3 of FIG. 11 eccentricity amount (ΔX, ΔY) and deviation amount (Δ
It is obvious that Z) can be calculated, and the calculated eccentricity (Δ
X, ΔY) and the deviation amount (ΔZ) are stored in the eccentricity / deviation amount storage unit 41 in step S4.

Next, the pressing margin P which is different for each normal direction of the tracing stylus 11 of the measuring head 10 shown in the measuring steps S5 and S6 of FIG.
An embodiment of a method for obtaining L using a calibrating means and creating a pressing margin data table will be described. First, the principle of obtaining the pressing margin PLn of the tracing stylus 11 of the measuring head 10 by using the calibration sphere 72 having the known radius R shown in FIG. 5 as the calibration means will be described.

That is, for example, the table 1 of the machine tool M
The calibrating sphere 72 is installed on the measuring sphere 72, and the sphere radius of the calibrating sphere 72 is measured by the measuring element 11 of the measuring head 10 to obtain the pressing margin PLn of the measuring element 11. In this case, first, a well-known indicator device is attached to the spindle 9 of the machine tool M in advance, and the indicator device is brought into contact with the surface of the calibration sphere 72 to show at least 4 same scale marks.
By reading the three-dimensional coordinate value of the point position, the calibration sphere 7
Find the center position of 2.

Next, the measuring head 10 is mounted on the main shaft 9 of the machine tool M, and a straight line connecting the center position of the calibration sphere 72 determined by the probe 11 and four arbitrary measuring points on the spherical surface,
That is, the normal direction set at each measurement point is obtained. After that, the tracing stylus 11 is fed by means of feeding in three axial directions, for example, feed driving of feeding mechanisms Fx, Fy, Fz in the X, Y, Z directions of the machine tool M, and target measurement points on the surface of the calibration sphere 72. Positioning is performed to the measurement starting point in the same manner as in the measurement step of the workpiece W shown in FIG. That is, in positioning at the measurement starting point, the eccentricity amount (ΔX, ΔY) and the deviation amount (ΔZ) of the tracing stylus 11 which have already been obtained are taken into consideration.
Position so that the center position of is on the normal line for the approaching motion. Next, each time the measurement head 10 is caused to approach the positions of the four measurement points of the calibration sphere 72 from their respective normal directions, and a measurement signal is emitted from the measurement head 10 in response to contact with the probe 11, the measurement signal detector 21 (Fig. 1)), and at that time, the position detector 19 detects the three-dimensional coordinate values of the four measurement points on the calibration sphere 72. The radius Rs of the spherical surface defined by the coordinate values of these four measurement points is calculated. Since the pressing margin PLn is present between the radius Rs of the calibration sphere 72 as the actual measurement value obtained from this calculation result and the radius r of the probe 11, and the known radius value R, PLn = (R + r) -(Rs) ··································· (7) from the expression (7)
Ln can be obtained.

Now, the tracing stylus 1 of the above-mentioned measuring head 10
As described above, the pressing margin PLn of 1 generally exhibits different pressing margins each time the approaching movement direction at the time of measurement, that is, the normal direction to various measurement points is different. Therefore, in the present invention, considering that the pressing margin of the probe 11 differs depending on the normal direction in advance, the plurality of selected calibration points on the spherical surface of the calibration sphere 72 are respectively arranged as shown in FIG. Plural press allowances PLn calculated by the above equation (7) are obtained by approaching from the normal direction, and these press allowances PL1, PL2, ... PLn.
m, PL2m ... PL4m ... And the latitude data φ and the longitude θ that uniquely determine the position of each point on the calibration spherical surface are used to create the press allowance data table. This pressing margin data table is also shown in FIG. Here, since one normal direction is determined corresponding to the position of each point on the calibration spherical surface, the position indicated by latitude φ and longitude θ in the press allowance data table does not correspond to one normal direction. Needless to say. Therefore, it should be noted that the pressing margin data table shown in FIG. 6 can be understood as indicating pressing margins corresponding to various normal line directions of the probe 11.

The pressing allowance data table thus created is stored in the pressing allowance data storage section 43 (see FIG. 1) of the data storage section 40 (step S6 in FIG. 3). Next, based on the press allowance data table stored in the press allowance data storage unit 43 in this manner, the respective measurement target points P1, P2, ...
The press allowance PL (PL _X , P
FIG. 6 shows the step S7 in which L _Y , PL _Z ) is calculated.
~ It demonstrates using FIG.

Now, the measurement target points P1, P2, ...
・ Measurement target point P1 is representative of the measurement head 1 in Pn
Consider a case where measurement is performed with a probe 11 of 0. At this time, as described above, the normal direction at the measurement target point P1 is the normal direction instructed in advance by the measurement program MRP or, as described with reference to FIG.
The coordinate values of the neighboring points are measured and selected in the direction of the normal VL of the narrow plane M including the measurement target point P1 determined by these measured coordinate values.

Next, the press allowance PL (PL _X , PL _Y , PL _Z ) when the probe 11 measures the measurement target point P 1 is directly applied to the normal VL, and the press allowance data table ( (See Figure 6) is difficult to obtain. In other words, the press allowance data table does not store the press allowance so much as to cover all the measurement target points P1, P2, ... Pn.
Therefore, a plurality of normal lines close to the normal line VL are selected from the latitude φ and the longitude θ of the press allowance data table. As an example, 4
Two normals have been selected. Naturally, the four points having such four normals are the four points Q1, Q2, Q3, Q4 on the surface of the calibration sphere 72 (see FIGS. 5 and 6), and the measurement target point P1.
As shown in FIG. 9, the points on the calibration sphere having the normal direction corresponding to the normal line VL (corresponding to points P1) on the calibration sphere are the above-mentioned four points Q1, Q2, Q3, Q
Located inside 4. The area L of the four points Q1, Q2, Q3, Q4 and the point P1 in FIG.
It is FIG.

Referring to FIG. 8, four points Q1, Q2, Q3, Q4
If the press allowances of the probe 11 corresponding to the respective normal directions in are the press allowance vectors PL1m, PL2m, PL3m, PL4m, first, a circle connecting the points Q1 and Q4 and the points Q2 and Q3. The points Q5 and Q6, which are found as the intersections of the arcuate line and the arcuate line passing through the point P1, are obtained, and the pushing margin vector at the point Q5 is determined from the length ratio of the arcuate line between Q2, Q5 and Q5, Q3. The push allowance vector of Q3 is calculated by the ratio distribution of the push allowance vector, and similarly, the push allowance vector of the same point Q6 is also obtained for the point Q6 by the same calculation method. Then point Q
Based on the length ratio of the arcuate line between points 5, P1 and points P1, Q6, the pushing margin vector of points Q5, Q6 is calculated by ratio distribution, and finally the pushing margin PL (PL _X , PL _X at point P1 is calculated. PL _Y , PL _Z )
Is to seek. Such a calculation is performed in the measurement pressing margin calculating unit 54 shown in FIG. The push margin PL (PL _X , PL _Y , PL _Z ) of the measurement target point P1 thus obtained
It suffices to correct the actually measured coordinate values (x, y, z) at the measurement target point P1 of the work W in the pressing margin correcting unit 55 using.

As described above, the measuring steps S2 to S
Eccentricity of the probe 11 of the measuring head 10
(ΔX, ΔY) and deviation amount (ΔZ) and approaching operation during measurement
Direction PL, PL, PLx, P
Ly, PLz) and perform measurement steps S8 to S10
If so, the corrected coordinate value (H_X, H_Y, H
_Z) Can be obtained. Therefore, as shown in FIG.
As shown in the measuring step S11 in the flowchart of
The same measurement process is applied to each of the measurement target points P2 to Pn.
Is repeatedly performed by the tracing stylus 11 of the measuring head 10.
If so, the coordinates corrected for all the measurement points P1 to Pn
Value (H_X, H_Y, H_Z) Can be asked. Therefore, this
All corrected coordinate values (H_X, H_Y, H_Z) Using
Three-dimensional by the work shape dimension calculator 57 (see FIG. 1)
An operation that connects the coordinate values in space to obtain the geometric dimension
If it is executed, as shown in the measurement step S12 of FIG.
Highly accurate measurement of the geometry of W
Of.

In the above description, the probe 1 is attached to the spindle 9 of the machine tool M.
1 is mounted, that is, the coordinate value (x ₀ , y ₀ , z ₀ ) of the center position of the probe 11 of the measuring head 10 mounted on the spindle 9 and the axis of the spindle 9 are Eccentricity amount (ΔX, ΔY) corresponding to the deviation amount and deviation amount (ΔX amount corresponding to the deviation amount from the predetermined reference position in the axial direction of the main shaft 9).
The method for measuring the shape and dimension of the work W has been described on the assumption that Z) already exists. However, when measuring the shape and dimension of the work W using a three-dimensional measuring machine or the like, the measuring program is generally created with reference to the center of the probe of the measuring head. It is not necessary to consider the above, and it suffices to correct only the pressing margin which is inevitably included in the measuring head and differs depending on the measuring direction with respect to the measured coordinate value.

[0052]

As is apparent from the description including the various embodiments of the present invention, according to the present invention, the shape and size of the work can be measured by the probe of the measuring head mounted on the spindle. It is possible, and even if the center position of the contact point of the measuring head is mounted with eccentricity and deviation with respect to the main shaft axis, it is also inevitably included in the measuring head, and the approach direction at the time of measurement Even when exhibiting different press allowance characteristics with different press allowances, the press allowance at the time of the measurement is calculated from the press allowance data table obtained in advance, and the coordinate value of the measurement point is calculated with the obtained allowance. It is possible to correct, and therefore, the geometrical dimension of the work can be measured with high accuracy.

In the above-described measuring device of the present invention, the measuring head mounted on the spindle may have either a contact type contact point or a non-contact type contact point. On the other hand, it is inevitable that eccentricity and deviation will occur when the measuring head is mounted instead of a tool, and it is a contact point of a non-contact type measuring head, for example, a capacitance type or eddy current type measuring head. However, in the coordinate detection of the measurement target point of the workpiece, a certain threshold value is existing corresponding to the pressing margin of the contact type measuring head. Therefore, based on the measuring method of the present invention, the working principle of the measuring device. It can be easily understood that highly accurate measurement of the work shape dimension can be performed by performing the measurement.

Further, in the above-mentioned embodiment, the pressing allowance data table is created by using the calibration sphere having the known radius R as the calibrating means, and the pressing allowance at the measurement target point of the work is calculated from it. However, the calibrating means is not limited to the calibrating sphere, and it is also possible to adopt a method or principle of creating a press allowance data table by using, for example, a master work having a congruent shape as the work as the calibrating means.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of a measuring apparatus used for carrying out a method for measuring a shape and dimension of a work according to the present invention.

FIG. 2 is a diagram illustrating a measurement target point of a workpiece according to the present invention in a state where a tracing stylus of a measuring head mounted on a spindle is eccentric or deviated from a spindle axis center and the tracing stylus has different pressing margins in an approaching direction. FIG. 3 is a schematic explanatory diagram for explaining a measurement process when the measurement is performed by the measurement method according to FIG.

FIG. 3 is a first half portion of a flow chart when the shape dimension measurement of a work according to the present invention is performed.

FIG. 4 is the latter half of the flow chart when the shape dimension measurement of the work according to the present invention is performed.

FIG. 5 shows a step of using a reference calibration sphere having a known radius dimension as a calibrating means, for example, installing it on a table of a machine tool and detecting a pressing margin of a probe of a measuring head mounted on a spindle. It is a schematic explanatory view for explaining.

FIG. 6 is a view showing a plurality of pressing margin measuring points on the sphere surface of a reference calibration sphere, where the contact point of the measuring head is made to approach from each of the pressing margin measuring points in the direction of the normal line uniquely determined. It is explanatory drawing explaining the process which calculates | requires the press allowance of the said measuring element corresponding to the position of a measurement point, therefore, a normal line direction, and obtains a press allowance data table.

FIG. 7 shows an example of how to obtain a normal vector at a target measurement point P ₁ of a work, and a plurality of points Q ₁ , Q _{2 of} a pressing margin data table obtained by using a reference calibration sphere for the pressing margin at the same point P ₁ .
Q _3, a schematically shown diagram a process of calculating explained on the basis of a plurality of押代obtained from Q _4.

[8] Similarly, the plurality of obtained from a plurality of points _{Q 1, Q 2, Q 3} , Q 4 of押代data table obtained using the reference calibration sphere押代in the target measurement point P ₁ of the workpiece push It is a schematic explanatory drawing explaining the process of calculating based on cost.

FIG. 9 is a plan view showing a state in which the points P ₁ , Q ₁ , Q ₂ , Q ₃ , Q ₄ are plotted on the surface of a reference calibration sphere.

FIG. 10 When measuring a measurement target point of an object to be measured, such as a work, by a tracing stylus (an example of a contact-type spherical measuring feeler) that a measuring head mounted on a spindle of a machine tool generally has , In order to schematically explain the situation when approaching (approaching) from the measurement start point to the measurement target point in the normal direction standing at the same point in the state where the spindle axis center and the center of the contact point are correctly aligned, FIG.

FIG. 11 is a schematic explanatory view for schematically showing an eccentric amount and a deviation amount of a center of a tracing stylus of a measuring head with respect to an axis of a main shaft.

FIG. 12 is a view showing a spindle axis when measuring a measurement target point of an object to be measured such as a work by a tracing stylus (an example of a contact-type spherical measuring feeler) included in a measuring head mounted on a spindle of a machine tool; Schematic explanatory diagram for schematically explaining the situation when approaching (approaching operation) from the measurement start point to the measurement target point in the normal direction standing at the same point while the center and the center of the contact point do not match. Is.

[Explanation of symbols]

9 ... Spindle 10 ... Measuring head 11 ... Stylus 13 ... Measurement program reading unit 15 ... Operation command section 17 ... Axis movement control unit 19 ... Position detector 21 ... Measured signal detector 30 ... Correction amount calculation unit 31 ... Eccentricity / deviation amount calculator 33 ... Calibration allowance calculation unit 40 ... Data storage unit 41 ... Eccentricity / deviation amount storage unit 43 ... Pushing allowance data storage section 50 ... Measured value calculator 51 ... Measured coordinate value detection unit 53 ... Eccentricity / deviation correction unit 54 ... Pushing allowance calculation unit for measurement 55 ... Pushing allowance correction section 57 ... Work shape dimension calculation unit 72 ... Standard calibration sphere M ... Machine tools W ... work MRP ... Measurement program

─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-4-63664 (JP, A) JP-A-2-44207 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B23Q 17/20 G01B 21/00

Claims (2)

(57) [Claims] 1. A method for measuring the shape and size of a work, wherein the coordinate values of the surface of the work are measured by a probe of a measuring head mounted on a spindle, the coordinate value of the center position of the probe of the measuring head mounted on the spindle. (X ₀ , y ₀ , z ₀ ) and the amount of eccentricity (ΔX, ΔY) that corresponds to the amount of deviation from the axis of the spindle, and the amount of deviation (ΔZ) that corresponds to the amount of deviation from the predetermined reference position in the direction of the axis of the spindle. look, the eccentric amount ([Delta] X, [Delta] Y) determined and stored the deviation ([Delta] Z), the measurement along each normal line direction toward the plurality of calibration measurement point of a predetermined calibration means having a known dimension The push allowance PLn in each normal direction of the probe is obtained by asymptotically moving the probe of the head, and the press allowance Pn in each normal direction of the probe of the obtained measurement head is obtained.
Ln is stored in association with each of the normal directions, based on a measurement procedure created in advance including a position of a measurement point of the work and a movement command to a position of a measurement start point corresponding to the measurement point, To the measurement start point obtained by moving the spindle and the workpiece relative to each other, taking in the stored eccentricity amount (ΔX, ΔY) and deviation amount (ΔZ) of the probe of the measurement head to the position of the measurement start point. Positioning, the probe of the measuring head is asymptotically moved along the normal direction from the obtained measurement start point to the measurement point, and the coordinate value of the measurement point when the measurement signal at the measurement point is received ( (x, y, z) are detected and taken in, a plurality of normal line directions in the vicinity of the measurement point are selected, and a plurality of the stored press allowances corresponding to the selected plurality of normal line directions are calculated to calculate the In the normal direction when measuring the workpiece Flip seek 押代 PL was, coordinate values of the captured measurement point (x, y, z) eccentricity with the stored and 押代 PL obtained above with respect to ([Delta] X, delta
Y) and the deviation amount (ΔZ) are used to obtain the coordinate value (Hx, Hy, Hz) of the measurement point, and the shape and dimension of the workpiece are calculated from the coordinate value (Hx, Hy, Hz) of the corrected measurement point. A method for measuring the shape and size of a workpiece, characterized in that the measured value of is calculated. 2. A workpiece shape measuring apparatus for measuring coordinate values on a surface of a work by a probe of a measuring head mounted on a spindle, wherein a coordinate value of a center position of a probe of the measuring head mounted on the spindle. (X ₀ , y ₀ , z ₀ ) and the amount of eccentricity (ΔX, ΔY) corresponding to the deviation of the axis of the main shaft and the amount of deviation (ΔZ) corresponding to the deviation of the main shaft from the predetermined reference position in the axial direction. And an eccentricity / deviation amount calculating means for obtaining the eccentricity / deviation amount (ΔX, Δ
Y) and an eccentricity / deviation amount storage means for storing the deviation amount (ΔZ), and along each normal line direction toward a plurality of calibration measurement points of a predetermined calibration means having a known dimension for the probe of the measuring head. And asymptotically moving it to obtain a pressing margin PLn in each normal direction of the probe, and a calibration pressing margin calculating means, and each normal direction of the measuring head of the measuring head obtained by the calibration pressing margin calculating means. The press allowance storage means for storing the press allowance PLn in the above in association with each normal direction, and the movement command to the position of the measurement point of the workpiece and the position of the measurement start point corresponding to the measurement point in advance. Based on the created measurement procedure, the spindle and the workpiece are moved relative to each other, and the eccentricity (ΔX, ΔX, stored in the eccentricity / deviation amount storage means at the position of the measurement start point of the probe of the measurement head is stored.
And a probe moving means for positioning the measurement start point obtained by taking in ΔY) and the deviation amount (ΔZ) and asymptotically moving along the normal direction from the obtained measurement start point to the measurement point. The measuring point when the measuring element of the measuring head is moved asymptotically along the normal direction from the obtained measurement starting point to the measuring point by the measuring element moving means, and the measuring signal at the measuring point is received. Measuring coordinate value reading means for reading the coordinate values (x, y, z) of the plurality of normal direction directions, and a plurality of normal direction directions in the vicinity of the measuring point are selected, and a plurality of the press allowances corresponding to the plurality of normal direction directions are selected. By storage
A measurement pressing margin calculating means for obtaining a pressing margin PL corresponding to the normal direction at the time of measuring the workpiece from the stored pressing margin, and coordinate values (x, y, x) of the measurement point read by the measurement coordinate value reading means. z) is corrected by the pressing margin PL obtained by the measuring pressing margin calculating means, the eccentricity amount (ΔX, ΔY) and the deviation amount (ΔZ) stored in the eccentricity / deviation amount storing means. Coordinates of points (Hx, Hy, H
z) for calculating the coordinate value of the workpiece, and the coordinate size (Hx, Hy, Hz) of the measurement point of the workpiece corrected by the coordinate value calculating means. This is a work shape measurement device.