JP3972920B2 - NC machine tool and correction processing method - Google Patents

Description

  The present invention relates to an NC machine tool and a correction machining method for machining a workpiece by relatively moving a tool and a table in an NC machine tool, and measuring a machining surface on the machine to correct an uncut residue exceeding an allowable value.

  Conventionally, in an NC machine tool such as a machining center, a workpiece is machined according to reference NC data to be machined into a target shape, and then a machining error of the workpiece with respect to the target shape is measured, and a portion where the machining error is outside the allowable range is corrected. A correction processing method is described in Patent Document 1.

  In the NC machine tool described in Patent Document 1, a touch sensor is attached to the spindle instead of a tool, and the touch sensor is sequentially brought into contact with the measurement points set on the machining surface in accordance with the measurement NC data. A three-dimensional coordinate value (X, Y, Z) is measured, and a machining error is calculated from the measured three-dimensional coordinate value of each measurement point and a target three-dimensional coordinate value in a target shape corresponding to the measurement point. Is extracted from the allowable range, corrected NC data is created for the extracted portion, and correction processing is performed.

Further, in the NC machine tool described in Patent Document 2, a plurality of surface elements constituting the workpiece machining surface are classified for each inclination angle, and the tool tip shape is projected onto the tool trajectory for each classified surface element. Then, based on the projected tool tip shape, an uncut amount is calculated for each surface element, and a surface element whose calculated uncut amount is outside the allowable range is extracted and correction processing is performed.
JP-A-6-277781 (paragraph number [0026] from page 4 to paragraph number [0035] from page 6 [FIG. 1]) JP 2003-108207 A (3rd page paragraph number [0020] to 3rd page paragraph number [0028], FIG. 2)

  By the way, in the NC machine tool correction machining method described in Patent Document 1, machining accuracy is measured for all the surface elements constituting the target shape, and thus a great deal of time and cost are required for measurement. In workpiece shape measurement, the number of measurement points increases as accurate measurement is required, and the number of measurement points increases as the shape becomes complicated. For example, in a mold used for plastic working or the like, the number of measurement points may be tens of thousands to hundreds of thousands, and measurement may be virtually impossible.

  The machining accuracy of a workpiece machined by an NC machine tool varies depending on the thermal displacement of the machine, the material and rigidity of the workpiece, the rigidity of the tool, thermal expansion and wear, etc., even if the target shape is the same. For this reason, in the calculation method of the remaining amount of each surface element in the NC machine tool described in Patent Document 2, it is assumed that the tool tip position during machining matches the target shape. The remaining uncut amount of each surface element considering thermal displacement, workpiece deformation, etc. cannot be calculated.

  The present invention has been made in view of the above circumstances, and it is possible to estimate the amount of uncut material regardless of the thermal displacement of the machine, the material of the workpiece, etc., and to greatly reduce the time required for measuring the shape of the workpiece after machining. An object of the present invention is to provide a correction machining method for an NC machine tool that can be shortened and can efficiently perform workpiece correction machining.

   In order to solve the above-described problem, the structural feature of the invention described in claim 1 is that a reference NC for machining a workpiece into a target shape, comprising a table for holding the workpiece and a spindle on which a tool is mounted. An NC machine tool that relatively moves a spindle and a table according to data and processes the workpiece into a target shape with a tool, and includes a measuring device that measures the shape of the workpiece held on the table, and constitutes a machining surface of the workpiece A plurality of surface elements are classified into a plurality of sections according to surface characteristics, and an error coefficient corresponding to an uncut amount based on the surface characteristics is determined and stored for each section, and at least one of the plurality of surface elements is stored. The reference point set for one surface element is measured by a measuring device, the uncut amount of the reference point is determined from the measured value of the reference point, the error factor of the category to which the surface element with the reference point belongs and each unmeasured surface element Calculate the estimated remaining amount of each unmeasured surface element from the relationship with the error coefficient of the category to which it belongs and the uncut amount of the reference point, and perform correction processing of each unmeasured surface element based on the calculation result of the estimated remaining amount. It is to judge necessity.

   The structural feature of the invention according to claim 2 is that, in claim 1, a surface element group to be processed with the same tool is formed among the plurality of surface elements, and a reference is made to at least one surface element for each of the surface element groups. The point is set.

   The structural feature of the invention according to claim 3 is that, in claim 1 or claim 2, in determining whether or not correction processing is necessary, a predetermined required measurement range including a predetermined maximum allowable uncut value is set. , Compare the required measurement range with the estimated uncut amount of each unmeasured surface element, measure the unmeasured surface element with the estimated uncut amount within the required measurement range as the required measurement surface element, and estimate the scrap It is determined that correction processing is required for unmeasured surface elements whose residual amount exceeds the required measurement range and measurement surface elements whose required measurement results exceed the allowable maximum value among the measurement surface elements that require measurement. Judged that correction processing is unnecessary for unmeasured surface elements that do not exceed the required measurement range and measurement surface elements that require measurement surface elements that do not exceed the maximum allowable value. That is.

   The structural feature of the invention according to claim 4 is that, in any one of claims 1 to 3, the surface characteristics are characteristics related to the shape and dimensions of each surface element.

  The structural features of the invention according to claim 5 are a table for holding a workpiece, a spindle on which a tool is mounted, a data storage unit for storing reference NC data for machining the workpiece into a target shape, and a data storage. The shape of the workpiece held on the table is determined in an NC machine tool composed of a control unit that relatively moves the spindle and the table according to the reference NC data stored in the unit and processes the workpiece into a target shape with a tool. The measuring device is equipped with a measuring device, and the data storage unit includes a plurality of sections in which a plurality of surface elements constituting the work surface of the work are classified according to surface characteristics, and an error corresponding to the uncut amount based on the surface characteristics for each section. The coefficient is stored, and the control unit classifies the plurality of surface elements of the workpiece processed by the reference NC data into a plurality of sections, and at least one of the plurality of surface elements. Measuring means for measuring a reference point set on the surface element by a measuring device, detection means for determining the uncut amount of the reference point from the measured value of the reference point, and an error coefficient of a classification to which the surface element having the reference point belongs Based on the relationship between the error coefficient of the category to which each unmeasured surface element belongs and the uncut amount of the reference point, the calculation means for calculating the estimated uncut amount of each unmeasured surface element, and the calculation result of the estimated uncut amount And determining means for determining whether or not each unmeasured surface element needs to be corrected.

  The structural feature of the invention according to claim 6 is that, in claim 5, the surface characteristics are characteristics related to the shape and dimensions of each surface element.

  In the invention according to claim 1 configured as described above, a reference point is set on at least one surface element constituting the machining surface machined by the tool, the reference point is measured, and an uncut amount is obtained. The amount of uncut surface on the unmeasured surface is obtained by estimation calculation from the amount of uncut material on the reference point. As a result, the uncut amount of the reference point set on one surface element of the machined surface processed in the same manner affected by the thermal displacement of the machine, the material of the workpiece, etc. is actually measured by the measuring device. Since the remaining amount of unmeasured surface element is estimated and calculated based on the measured remaining amount of the reference point, the unremoved amount including the thermal displacement of the machine and the material of the workpiece is calculated for each unmeasured surface element. An estimation calculation can be performed.

  In the invention according to claim 2 configured as described above, a surface element group is formed for each same tool, and a reference point is set and measured for each surface element group. It is possible to estimate and calculate the remaining amount of unmeasured surface element after making the remaining amount to be cut common to the same surface element group. For this reason, even if there is no data of the remaining amount of cutting due to the type of tool, the remaining amount of cutting including the remaining amount of cutting due to the type of tool can be estimated and calculated for each unmeasured surface element.

  In the invention according to claim 3 configured as described above, the unmeasured surface element in which the estimated uncut amount calculated for each unmeasured surface element is within a predetermined measurement range including the upper limit portion of the uncut allowance value Since only the measurement is performed with the measuring device, the measurement time can be greatly shortened. Since it is judged that correction processing is necessary for surface elements whose measured uncut amount exceeds the maximum allowable uncut amount and unmeasured surface elements whose estimated remaining amount exceeds the required measurement range, the surface elements that require correction processing are determined in a short time. To find out exactly.

   In the invention according to claim 4 configured as described above, a plurality of surface elements constituting the machining surface of the workpiece are classified into a plurality of categories according to surface characteristics such as the inclination angle of the surface and the size of the radius. Estimate the uncut amount of the measured surface element from the surface characteristics of each unmeasured surface element and the measured uncut amount of the reference point, and accurately estimate the uncut amount of each unmeasured surface element according to the actual situation. Can do.

  In the invention according to claim 5 configured as described above, the measuring means sets and measures a reference point on at least one surface element constituting the machining surface machined by the tool, and the detection means scrapes from the measurement result. The remaining amount is obtained, and the calculation means obtains the uncut surface remaining amount on the unmeasured surface from the remaining uncut amount of the reference point by estimation calculation. As a result, the uncut amount of the reference point set on one surface element of the machined surface processed in the same manner affected by the thermal displacement of the machine, the material of the workpiece, etc. is actually measured by the measuring device. Based on the measured uncut amount of the reference point, the uncut amount of each unmeasured surface element is estimated and calculated. As a result, the NC machine tool can estimate and calculate the uncut amount including the influence of the thermal displacement of the machine, the material of the workpiece, and the like for each unmeasured surface element.

   In the invention according to claim 6 configured as described above, a plurality of surface elements constituting the machining surface of the workpiece are classified into a plurality of categories according to surface characteristics such as the inclination angle of the surface, the size of the radius, and the like. Since the uncut amount of the measured surface element is estimated and calculated from the surface characteristics of each unmeasured surface element and the measured uncut amount of the reference point, the NC machine tool will determine the uncut amount of each unmeasured surface element according to the reality. It can be estimated accurately.

   Hereinafter, a correction machining method for an NC machine tool according to an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 10 denotes a machining center as an NC machine tool, which includes a table 12 for holding a workpiece W and a spindle 15 on which a tool T is mounted, and the spindle 15 according to reference NC data for machining the workpiece W into a target shape. And the table 12 is moved relatively, and the workpiece W is machined with the tool T so as to have a target shape. After the machining of the workpiece W by the tool T is finished, the measuring device 18 for measuring the shape of the workpiece shown in FIG. 2 is attached to the spindle 15 in place of the tool T, and the processed workpiece held on the table 12 is mounted. A reference point set on at least one of the plurality of surface elements constituting the machining surface is measured.

  The machining center 10 includes a bed 11, and a slide table 12 that moves along the X-axis direction (left-right direction) and a column 13 that moves along the Z-axis direction (front-back direction) are provided on the bed 11. ing. The column 13 includes a headstock 14 that moves in the Y-axis direction (vertical direction). The spindle stock 14 is rotatably driven by a motor, and a spindle 15 on which a tool T is detachably mounted is supported on the tip. ing. A tilt table 16 is mounted on the slide table 12 so as to be swingable about an A axis parallel to the X axis, and on the tilt table 16, a rotary table 17 as a table for holding the workpiece W is orthogonal to the A axis. It is supported so as to be rotatable around the B axis.

  In the measuring device 18, the touch probe 19 is movably mounted on the main body 20, protrudes forward in the axial direction, and is held in an initial posture by a compression spring. The touch probe 19 has a sphere portion 21 formed at the tip, and the sphere portion 21 tilts in an arbitrary direction by receiving an external force, and the displacement amount of the sphere portion 21 is detected by the tilt angle. A mounting portion 22 projects from the rear of the main body 20, the mounting portion 22 is fitted into a fitting hole formed at the tip of the main shaft 15, and the measuring device 18 is mounted on the main shaft 15 stopped at a fixed position. . In a state where the measuring device 18 is attached to the main shaft 15, the axis passing through the center of the sphere 21 of the touch probe 19 coincides with the axis of the main shaft 15. A connection terminal 23 projects rearward from the main body 20, and when the measuring device 18 is attached to the main shaft 15, the electric terminal 23 is connected to an electric terminal provided on the main shaft 14, and information on the displacement amount of the sphere 21 is obtained. It is transmitted to the control device 24.

  As shown in FIG. 3, the control device 24 of the machining center 10 includes a data storage unit 25 and a drive control unit 26. For example, reference NC data generated by the CAD / CAM 30 is stored in the data storage unit 25 as a reference NC data file. 27 is stored. Then, the drive control unit 26 reads the reference NC data from the reference NC data file 27, and in accordance with the reference NC data, the X, Y, Z, and X of the slide table 12, the column 13, the headstock 14, the tilt table 16, and the rotary table 17 are read. The drive shaft motors 29 for the A and B axes are driven, and the main shaft motor for the main shaft 15 is driven to rotate. As a result, the tool T attached to the tip of the main spindle 15 processes the workpiece W so as to have a target shape. The data storage unit of the present invention corresponds to the data storage unit 25 and the CAD / CAM 30 of the present embodiment, and the control unit of the present invention corresponds to the control device 24 and the CAD / CAM 30 of the present embodiment.

  In order to measure a reference point set on at least one surface element among a plurality of surface elements constituting a processed surface of a processed workpiece held on the table 12 by mounting the measuring device 18 on the spindle 15. The measurement NC data is created by the CAD / CAM 30 and is stored in the data storage unit 25 as the measurement NC data file 28. If the reference point is a plane parallel to the XZ plane including the X and Z axes and is set at the center portion of the surface element located at the center portion of the workpiece W, the measurement error can be reduced.

   The CAD / CAM 30 obtains a surface normal vector at the reference point of the surface element for which the reference point is set, rotates the workpiece W so that the surface normal vector coincides with the axis of the main axis 15, and the touch probe 19 After the measuring device 18 is positioned with respect to the workpiece W at the measurement start position whose tip is separated from the reference point by a predetermined amount in the surface normal vector direction, the touch probe 19 is moved closer to the reference point from the surface normal direction. 21, the tilt table 16 and the rotary table 17 are rotated around the A and B axes so that the touch probe 19 is slightly moved backward with respect to the main body 20. NC data for measurement is created to move the slide table 12, column 13 and headstock in the X, Y and Z axis directions, and the NC data file for measurement 2 It is stored in the data storage unit 25 as. The retraction amount of the touch probe 19 due to the contact between the spherical portion 21 and the surface element is measured by a displacement type built in the main body 20, and the measurement retraction amount of the touch probe 19 and the setting of the touch probe 19 in the target shape are set. From the difference from the retraction amount, the uncut amount of the surface element on which the reference point is set is obtained by CAD / CAM 30. In order to reduce the measurement error of the measuring device 18, a reference surface parallel to the XZ plane and having a known height in the Y direction is provided on the rotary table 17, and the height of this reference surface is the same as described above. The measurement retraction amount of the touch probe 19 may be calibrated based on the measurement value measured by the measurement NC data.

  As an example of the workpiece W, a molding die is shown in FIG. The molding die 31 is composed of a plurality of surface elements 32 constituting a processed surface, and the surface elements 32 are classified into a plurality of types based on the shape. That is, it is roughly divided into a plane 33 that forms the bottom surface of the mold 31, a spherical surface 34 that forms the bottom corner of the mold 31, and a corner curved surface 35 that forms the side corners of the mold 31. The surface elements 32 of each shape are further divided according to the shape-specific dimensions, and the plurality of surface elements 32 constituting the machining surface of the workpiece W are classified into a plurality of sections according to the surface characteristics related to the shape and dimensions of each surface element 32. The The dimension peculiar to the shape is an inclination angle θ with respect to the XY plane at the time of processing for the plane 33, and a radius R for the spherical surface 34 and the corner curved surface 35. The degree of the amount of uncut residue generated on the machined surface is obtained from the measured values of the surface that were trial-machined for each category, and an error coefficient corresponding to the uncut amount based on the surface characteristics is determined for each category and the data storage unit 25.

  The error coefficient of each section is determined relative to an error coefficient of a plane having an inclination angle θ of 0 having a plane base value of 1. The error coefficient k1 of the plane 33 is stored as a graph that increases as the inclination angle θ increases as shown in FIG. The error coefficient k2 of the spherical surface 34 is a spherical base value larger than 1 when the ratio 2 × R / D between the spherical radius R and the tool radius D / 2 is 1, as shown in FIG. It is memorize | stored as a graph which decreases gradually toward 1 as it becomes. As shown in FIG. 7, when the ratio 2 × R / D between the radius R of the curved surface and the radius D / 2 of the tool is 1, the error coefficient k3 of the corner curved surface 35 is larger than 1 and smaller than the spherical base value. And is stored as a graph that gradually decreases toward 1 as the ratio increases. In addition, the ratio of the slope angle θ of the plane, the radius R of the spherical surface and the curved surface, and the radius D / 2 of the tool T is divided into a plurality of parts, and the error coefficient determined based on the measured value of the surface trial-worked for each section. May be registered in the data storage device 25.

  In CAD / CAM 30, the uncut amount of the reference point is obtained from the measured value of the reference point, the relationship between the error coefficient of the section to which the surface element having the reference point belongs and the error coefficient of the section to which each unmeasured surface element belongs, and the reference point When calculating the estimated remaining amount of each unmeasured surface element from the uncut amount of P, for example, if the reference point P is set on a plane 33 parallel to the XY plane at the time of machining, the mold 31 6 is obtained from the graph shown in FIG. 6 based on the radius R of the spherical surface 34 and the radius D / 2 of the tool T used for machining. An estimation calculation is performed by multiplying the uncut amount of the reference point by k2. The estimated uncut amount of the curved corner surface 36 of the mold 31 is obtained by calculating an error coefficient k1 of a plane inclined by the inclination angle θ from the graph shown in FIG. An error coefficient k3 is obtained from the graph shown in FIG. 7 based on the diameter D of the tool T used, and is estimated and calculated by multiplying the uncut amount of the reference point by a product k1 × k3 of these error coefficients. For a surface element composed of a convex spherical surface or a convex curved surface, the surface element is assumed to be composed of a plurality of elementary planes, and the estimated uncut amount is calculated from an error coefficient k1 corresponding to the inclination angle θ of each elementary plane.

  The CAD / CAM 30 calculates the uncut remaining amount of the reference point from the measured value of the reference point, calculates the estimated uncut amount of each unmeasured surface element, and performs a predetermined required measurement including a predetermined maximum allowable uncut amount Set the range, compare the required measurement range with the estimated uncut amount of each unmeasured surface element, and set the unmeasured surface element with the estimated uncut amount included in the required measurement range as the required measurement surface element Correction processing is required for unmeasured surface elements that are measured by the measurement device 18 and whose estimated uncut remaining amount exceeds the required measurement range, and for measured surface elements that require measurement results that exceed the allowable maximum value. Is stored. Then, NC data for correction processing is created for the surface element determined to require correction processing, and is stored in the data storage unit 25 as the NC data file 37 for correction processing.

    Next, the operation of the NC machine tool correction machining method will be described. The CAD / CAM 30 stores the programs shown in FIGS. The workpiece W is held on the rotary table 17 by a jig, and the drive control unit 26 reads and executes the reference NC data from the reference NC data file 27 to process the workpiece W into the molding die 31 (S1 in FIG. 8). .

  When the machining of the workpiece W by the reference NC data is completed, as shown in step 2, the NC machine tool 10 performs the measurement of the reference point P and the calculation of the estimated remaining amount of the unmeasured surface element. The detailed operation of Step 2 is shown in FIG. First, the CAD / CAM 30 displays a screen of the target shape of the workpiece W as shown in FIG. 4 on a display device (not shown) based on the model data of the workpiece W stored in advance for creating the reference NC data. (S100 in FIG. 9). When the screen of the target shape of the workpiece W is displayed, the operator designates the surface element H to be measured from the shape screen of the workpiece W using a touch pen or a mouse (not shown) (S101 in FIG. 9). Here, it is assumed that the central plane 33 of the mold 31 in FIG. 4 is designated as the surface element H to be measured. When a surface element to be measured is designated, the CAD / CAM 30 creates NC data for measurement for the machining center 10 to perform measurement.

  The measurement NC data is created by creating the reference point P of the surface element H to be measured designated in step 101. In creating the reference point P, the center of the designated surface element is set as the reference point P (S102 in FIG. 9). Next, the routine proceeds to step 103, where the surface normal vector of the surface element H at the reference point P is obtained. In step 104, measurement NC data for measuring the coordinates of the reference point P by making the touch probe 19 approach the reference point P from the direction of the surface normal vector of the surface element H is created. Specifically, the surface element H of the workpiece W in FIG. 4 is a plane having no inclination, that is, a plane having an inclination angle θ of 0 °. Accordingly, the surface normal vector of the surface element H at the reference point P is directed in the vertical direction.

  In order to bring the touch probe 19 into contact with the reference point P from the direction of the surface normal vector of the surface element H, the Z axis is made parallel to the surface normal vector of the surface element H at the reference point P. There is a need. Therefore, NC data for turning the workpiece W around the A axis and the B axis by the tilt table 16 and the rotary table 17 so that the surface element H is parallel to the X axis and the Y axis, and X− In the Y plane, in order to position the touch probe 19 in the direction of the surface normal vector of the reference point P, the NC data for moving the slide table 12 and the headstock 14 and the column 13 are brought close to the work W to touch the touch probe 19. NC data for detecting the coordinate position in the Z direction in contact with the surface element H is created. Thus, when the measurement NC data is created, the CAD / CAM 30 transfers and stores the measurement NC data in the measurement NC data file 28 of the data storage unit 25, and via the main control unit 41, A measurement start signal is given to the drive control unit 26 of the machining center 10.

  Then, the drive control unit 26 of the machining center 10 reads the measurement NC data from the measurement NC data file 28 of the data storage unit 25 and measures the coordinate position in the Z-axis direction of the reference point P of the workpiece W by the touch probe 19. To do. (S105). Then, the CAD / CAM 30 compares the coordinate position in the Z-axis direction of the reference point P in the target shape of the workpiece W based on the model data with the coordinate position in the Z-axis direction of the actually measured reference point P. The deviation of the coordinate position of the point P in the Z-axis direction, that is, the uncut amount of the surface element H where the reference point P is set is obtained.

  Next, the CAD / CAM 30 recognizes the model shape. The recognition of the model shape is mainly classified into a plurality of types according to the surface characteristics of each surface element according to the processed element and the surface element according to the shape and dimensions (S106). Specifically, it is classified into machining processes with different machining conditions such as tools and feed rates, and the model shape is decomposed into predetermined shapes, for example, planes, corner curved surfaces, spherical surfaces, etc., and classified for each surface element To do. In the mold 31 shown in FIG. 4, 33 is classified as a plane, 35 is classified as a corner curved surface, and 34 is classified as a spherical surface. Further, an inclined corner curved surface such as 36 is classified so as to belong to both a flat surface and a corner curved surface. In addition, in the metal mold | die 31 of FIG. 4, suppose that it classify | categorized only by the shape as what was processed with the same tool and the same process conditions for easy description. These classified surface elements are further classified by dimensions. Specifically, the plane 33 is divided for each predetermined inclination angle θ, and the corner curved surface 35 and the spherical surface 34 are divided based on the ratio of the radius D / 2 of the tool to the corner radius R.

When the recognition of the model shape in step 106 is completed, the process proceeds to step 107, and the uncut amount of each unmeasured surface element is estimated from the uncut amount of the surface element H to which the reference point P obtained in step 105 belongs. An error coefficient is used to estimate the uncut surface amount of the unmeasured surface element.
As shown in FIGS. 5 to 7, the error coefficient is determined based on the division of each surface element and stored in the data storage unit 25. Specifically, on the plane 33, the inclination angle θ is 0 ° as shown in FIG. 5, that is, the uncut amount on the horizontal plane is the smallest, and the uncut amount increases as the inclination angle increases. Further, as shown in FIGS. 6 and 7, it has been experimentally clarified that the amount of uncut material decreases as the ratio of the radius D / 2 of the tool and the corner radius R increases as shown in FIGS. Further, there is an association between the surface element 32 of the plane 33, the corner curved surface 34, and the spherical surface 35, and the corner curved surface 34 and the spherical surface 35 can be regarded as a plane when the ratio of the tool radius D / 2 to the corner radius R increases. it can. For this reason, it is possible to estimate the uncut amount of the corner curved surface 34 and the spherical surface 35 based on the uncut amount of the flat surface 33. Specifically, as apparent from FIG. 5, when the error coefficient K1 on the horizontal plane (inclination angle θ is 0 °) is 1.0, and the uncut amount at this time is 20 μm, the corner curved surface is substantially flat. The ratio of the radius D / 2 of the tool that can be considered and the corner radius 2R is about 2.0 or more. If this ratio is about 2.0 or more, the error coefficient K2 is 1.0 from FIG. 0.0 = 20 μm. Similarly, in the spherical surface, the ratio of the radius D / 2 of the tool that can be regarded as a plane and the corner radius R is about 2.0 or more. When this ratio is about 2.0 or more, the error coefficient K3 is 2.0 from FIG. Therefore, 20 μm × 2.0 = 40 μm.

  From the relationship between the error coefficients K1, K2, and K3 of the section to which the surface element having the reference point P belongs and the error coefficients K1, K2, and K3 of the section to which each unmeasured surface element belongs and the uncut amount of the reference point P Calculate the estimated uncut amount of each unmeasured surface element. Specifically, in FIG. 6, the surface element H having the reference point P is a horizontal plane, and when the measured uncut amount is 20 μm, the error coefficient K1 is 1.5 from the plane of FIG. Therefore, the estimated uncut error is estimated as 20 μm × 1.5 = 30 μm. Further, in the case of an inclined corner curved surface that belongs to both the flat surface 33 and the corner curved surface when classified in step 106, the uncut amount is generated due to both the inclined plane and the corner curved surface. Therefore, the estimated uncut amount is obtained by integrating the error coefficients K1 and K2. In this way, when the calculation of the estimated uncut surface amount of the unmeasured surface element of the workpiece W is completed in step 107, the CAD / CAM 30 temporarily stores the estimated uncut surface amount of the unmeasured surface element. Proceed to step 3.

When proceeding to step 3, the CAD / CAM 30 reads out the estimated uncut amount of one unmeasured surface element from the temporarily stored uncut surface amount of the unmeasured surface element, and goes from step 3 to step 9. The correction processing necessity determination shown is executed.
Here, the concept of the necessity determination of the correction process shown in step 3 to step 9 will be described with reference to FIG. FIG. 12 is a diagram showing the relationship between the estimated uncut amount of each surface element calculated in step 2, the uncut remaining allowable maximum value γ and the required measurement range α-β, which will be described later. The uncut allowance maximum value γ indicates the maximum uncut amount that the die 31 can accept as a product. Further, the measurement required range α-β is a value set with a predetermined width with an uncut remaining allowable maximum value γ interposed therebetween. These allowable uncut values γ and the required measurement range α-β are stored in the CAD / CAM 30. In addition, the uncut remaining allowable value for which each surface element of the mold 31 is regarded as acceptable as a product is a value between 0 and the uncut remaining allowable maximum value γ. In such a relationship, it is determined whether or not it is necessary to correct the estimated remaining shaving amount estimated in step 3. First, in the case of an unmeasured surface element whose estimated uncut amount is between α and 0, that is, a value sufficiently smaller than the uncut allowance maximum value, it is considered that even if the uncut amount is measured, the uncut allowance value is entered. Therefore, it is determined that the surface element does not require correction processing without performing measurement by the measuring device 18. Conversely, in the case of an unmeasured surface element whose estimated remaining amount is larger than β, that is, a value sufficiently larger than the maximum allowable remaining value, it is considered that the allowable remaining value does not enter even if the remaining amount is measured. Therefore, it is determined that the surface element needs to be corrected without performing measurement by the measuring device 18. If the estimated uncut amount is a value between α and β, that is, an unmeasured surface element that is within the required measurement range, the uncut remaining allowable maximum value γ unless the uncut amount is actually measured due to an error in the estimation calculation, etc. Since it is difficult to determine whether or not the value exceeds, actual measurement by the measurement device 18 is performed. As a result, when the actually measured uncut amount exceeds the uncut allowable maximum value γ, it is determined that the surface element needs correction processing. Further, when the actually measured uncut amount does not exceed the uncut allowable maximum value γ, it is determined that the surface element does not require correction processing.

  As described above, the measurement apparatus measures only the unmeasured surface element whose estimated uncut amount estimated for each unmeasured surface element is within the predetermined measurement range α-β including the upper limit portion of the uncut value allowable value. Therefore, the measurement time can be greatly shortened. Since it is judged that correction processing is necessary for surface elements whose measured uncut amount exceeds the maximum allowable uncut amount and unmeasured surface elements whose estimated remaining amount exceeds the required measurement range, the surface elements that require correction processing are determined in a short time. To find out exactly.

  Hereinafter, step 4 in FIG. 9 will be described. In step 4, it is determined whether or not the estimated uncut amount of the unmeasured surface element read in step 3 is within the measurement required range. This required measurement range is set to a range that includes the maximum allowable uncut value for the target shape of the workpiece W, and it is difficult to determine whether it is within the allowable uncut value due to calculation error of the estimated uncut amount If the estimated uncut surface amount of the unmeasured surface element that is used to extract the unmeasured surface element is within the required measurement range, the process proceeds to step 5, and the estimated uncut surface element amount of the unmeasured surface element is required to be measured. If it is outside the range, the process proceeds to step 6.

  In Step 5, since it is difficult to determine whether or not it is within the allowable uncut value due to a calculation error of the estimated uncut amount, actual measurement is performed as a measurement surface element. This measurement procedure is the same as the measurement procedure for the reference point P, and the measurement NC data for measuring the coordinates by bringing the touch probe 19 closer from the direction of the surface normal vector of the measurement surface element to be measured is created. In this way, when the measurement NC data is created, the CAD / CAM 30 transfers the measurement NC data to the measurement NC data file 28 of the data storage unit 25 and stores it in the drive control unit 26 of the machining center 10. A measurement start signal is given. Then, the drive control unit 26 of the machining center 10 reads the measurement NC data from the measurement NC data file 28 of the data storage unit 25, and measures the coordinate position in the Z-axis direction of the measurement surface element required by the touch probe 19.

  In step 5, when the coordinate position in the Z-axis direction of the measurement surface element is measured, the process proceeds to step 7 and the coordinate position in the Z-axis direction of the measurement surface element in the target shape of the workpiece W based on the model data. Then, the coordinate positions in the Z-axis direction of the measurement surface elements actually measured are compared. The deviation of the coordinate position in the Z-axis direction, that is, the uncut amount of the surface element requiring measurement is obtained, and it is determined whether or not the uncut amount is larger than the uncut remaining allowable maximum value. If it is determined by this determination that the uncut remaining amount is not larger than the maximum uncut remaining allowable value, that is, the uncut remaining amount is equal to or less than the maximum unleaved allowable value, the process proceeds to step 8, and the uncut remaining amount is the maximum uncut remaining allowable value. If it is determined that it is larger, correction processing is necessary, so that it is stored in the CAD / CAM 30 as a surface element requiring correction processing in step 9, and the process proceeds to step 10.

  On the other hand, when it is determined in step 4 that the estimated remaining amount of the unmeasured surface element is outside the required measurement range and the process proceeds to step 6, it is then determined whether or not the estimated remaining amount of the unmeasured surface element is larger than the required measurement range. Determined. Here, when it is determined that the estimated remaining amount of the unmeasured surface element is larger than the required measurement range, correction processing is necessary, and thus the process proceeds to Step 9 where the estimated remaining amount of the unmeasured surface element is the required measurement range. If it is determined that the estimated remaining amount of unmeasured surface element is smaller than the required measurement range, there is no need for correction processing, and it is stored in the data storage unit 25 as a surface element that does not require correction processing. , Go to Step 10.

  As described above, in the above-described embodiment, the estimated remaining amount of the unmeasured surface element is obtained based on the measured remaining amount of the reference point P and the error coefficient set for each surface element, and this unmeasured surface Only the surface elements that need to be measured are measured as indicated by the circles in FIG. 10 in comparison with the estimated uncut remaining amount of elements and the required measurement range. Thereby, the measurement surface element which the workpiece | work W measures is decreased, and measurement time can be shortened significantly.

  Proceeding to step 10, it is determined whether or not correction processing is necessary for all unmeasured surface elements. If not, the process returns to step 3 and repeats step 4 to step 10 to repeat all unmeasured. The necessity of correction processing is determined for the surface element. When the determination of whether or not correction processing is necessary for all unmeasured surface elements is completed, the process proceeds to step 11 and correction processing is performed on the surface elements that require correction processing stored in the data storage unit 25 (● in FIG. 11). Surface element). Specifically, as a result of machining along the target shape, the uncut residue remains beyond the maximum allowable allowable value, so that the CAD / CAM 30 is used for correction machining at a deeper position where the CAD / CAM 30 is further cut than the target shape. A target machining surface is set, correction machining NC data is generated and stored in the correction machining NC data file 37, and the machining center 10 performs correction machining based on the correction machining NC data.

  After the correction processing is completed, for example, the reference point P is set again from the corrected surface elements, the shape is measured by the measuring device 18, and the steps 2 to 11 in FIG. It converges below the maximum allowable uncut value. Alternatively, after performing the correction process several times, the mold 31 in which the uncut amount between the mold 31 and the target shape does not fall below the maximum allowable uncut value is excluded as a rejected product.

  In this way, the measurement device 18 actually measures the uncut amount of the reference point P set on one surface element of the machined surface that has been machined in the same manner affected by the thermal displacement of the machine and the material of the workpiece. In addition, since the uncut surface amount of each unmeasured surface element is estimated on the basis of the actually measured uncut amount of the reference point P, the influence of the thermal displacement of the machine, the material of the workpiece W, etc. on each unmeasured surface element is included. It is possible to accurately estimate and calculate the amount of uncut residue. In addition, since the estimated amount of uncut material estimated and calculated for each unmeasured surface element is measured by the measuring device only for unmeasured surface elements that are within the required measurement range including the upper limit of the uncut value, the measurement time is greatly increased. Can be shortened. Since it is judged that correction processing is necessary for surface elements whose measured remaining amount exceeds the allowable value and unmeasured surface elements whose estimated remaining amount exceeds the required measurement range, the surface elements that require correction processing are accurately determined in a short time. Can be found.

  Furthermore, the multiple surface elements that make up the work surface of the workpiece are classified into multiple categories according to surface characteristics such as the inclination angle of the plane and the radius of the corner curved surface, and the uncut amount of each unmeasured surface element Since the estimation calculation is performed from the surface characteristics of the measurement surface element and the measurement uncut amount of the reference point P, the uncut amount of each unmeasured surface element can be accurately estimated according to reality.

  In the above embodiment, the classification means of the present invention corresponds to step 106 in FIG. 9, and the measurement means and detection means correspond to step 105. The computing means corresponds to step 107, and the judging means corresponds to step 4 to step 9 in FIG.

  In the above embodiment, when machining using a plurality of tools, if a surface element group is formed for each same tool and a reference point is set for each surface element group and measured, the type of tool It is possible to estimate and calculate the uncut surface amount of the unmeasured surface element after making the uncut surface amount due to the same in the same surface element group. For this reason, even if there is no data of the remaining amount of cutting due to the type of tool, the remaining amount of cutting including the remaining amount of cutting due to the type of tool can be accurately estimated and calculated for each unmeasured surface element.

  Also, if the estimated amount of remaining shaving can be estimated and calculated with a value equivalent to the actual measured value, the estimated amount of remaining shaving is compared with the maximum allowable amount of remaining shaving. If it is determined that correction is necessary, and the estimated uncut remaining amount is equal to or less than the allowable maximum value, it may be determined that correction is unnecessary. In this way, the measurement time can be further shortened.

[Other Embodiments]
The present invention is not limited to the above-described embodiment. For example, the embodiments described below are also included in the technical scope of the present invention, and various other than the following can be made without departing from the scope of the invention. It can be changed and implemented.

(1) Although the workpiece W of the embodiment is the mold 31, the shape of the workpiece W is not limited to the mold.
(2) In the above embodiment, the measuring device 18 is detachably attached to the main shaft 15 of the machining center 10 to measure the shape of the workpiece. However, the configuration may be such that the machining center 10 is confronted with a three-dimensional measuring device. .
(3) The measuring device 18 measures the shape in contact with the workpiece. For example, the measuring device 18 includes a non-contact distance sensor, and measures the shape of the workpiece by scanning the surface of the workpiece with the distance sensor. It may be configured.
(4) In the above embodiment, the operator designates the selection of the reference point P. However, the CAD / CAM 30 may automatically set it. Further, at this time, if the reference point P is set to a surface element having the smallest error coefficient value, for example, a horizontal plane, the processing accuracy is improved because the processing is simple. As a result, since measurement is performed on surface elements with good machining accuracy, the estimation calculation accuracy of the estimated uncut remaining amount can be improved, and the extraction accuracy of the measurement surface elements to be measured can be improved. It can be shortened.

1 is a schematic perspective view of a machining center as an NC machine tool according to an embodiment of the present invention. 1 is an overview diagram of a measuring device that measures the shape of a workpiece. The block diagram which shows the electrical structure of a machining center. The top view of the metal mold | die for shaping | molding as an example of the workpiece | work W. FIG. The graph which shows the error coefficient of a plane. The graph which shows the error coefficient of a corner curved surface. The graph which shows the error coefficient of a spherical surface. The flowchart which shows the operation | movement procedure of NC machine tool. The flowchart which shows the operation | movement procedure which estimates the amount of uncut parts. Explanatory drawing which shows the setting state of the measurement surface element required in a metal mold | die for shaping | molding. Explanatory drawing which shows the setting state of the surface element of the correction process required in the metal mold | die for shaping | molding. The figure explaining the concept of the necessity determination of a correction process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Machining center (NC machine tool), 11 ... Bed, 12 ... Slide table, 13 ... Column, 14 ... Spindle table, 15 ... Spindle, 16 ... Tilt table, 17 ... Rotary table (table), 18 ... Measuring device, 19 DESCRIPTION OF SYMBOLS ... Touch probe, 20 ... Main body, 21 ... Sphere part, 22 ... Mounting part, 23 ... Connection terminal, 24 ... Control device, 25 ... Data storage part, 26 ... Drive control part, 27 ... Reference NC data file, 28 ... Measurement NC data file, 29 ... Drive shaft motor for each axis, 30 ... CAD / CAM, 31 ... Mold for molding, 32 ... Surface element, 33 ... Plane, 34 ... Spherical surface, 35 ... Corner curved surface, 36 ... Inclined Corner curved surface, 37: NC data file for correction processing, P: Reference point.

Claims (6)

A table for holding a workpiece and a spindle on which a tool is mounted; the spindle and the table are moved relative to each other according to reference NC data for machining the workpiece into a target shape; In NC machine tools that machine into shapes,
A measuring device for measuring the shape of the workpiece held on the table;
Classifying a plurality of surface elements constituting the machining surface of the workpiece into a plurality of sections according to surface characteristics, and determining and storing an error coefficient corresponding to an uncut amount based on the surface characteristics for each section,
A reference point set on at least one of the plurality of surface elements is measured by the measuring device;
Obtain the uncut amount of the reference point from the measured value of the reference point,
Calculate the estimated uncut amount of each unmeasured surface element from the relationship between the error coefficient of the category to which the surface element with the reference point belongs and the error coefficient of the category to which each unmeasured surface element belongs and the uncut amount of the reference point And
A correction machining method for an NC machine tool, wherein the necessity of correction machining for each unmeasured surface element is determined based on a calculation result of the estimated remaining uncut amount. In claim 1,
An NC machine tool correction characterized in that a surface element group to be processed with the same tool is formed among the plurality of surface elements, and a reference point is set to at least one surface element for each of the surface element groups. Processing method. In claim 1 or claim 2,
The determination of the necessity of the correction machining is performed by setting a predetermined required measurement range including a predetermined maximum allowable uncut amount and comparing the required measurement range with the estimated uncut amount of each unmeasured surface element. And measuring the unmeasured surface element having the estimated uncut amount within the measurement required range as the measurement surface element required by the measuring device,
It is determined that correction processing is necessary for an unmeasured surface element whose estimated uncut remaining amount exceeds the required measurement range and a measured surface element whose measurement result exceeds the allowable uncut maximum value among the required measurement surface elements. ,
No correction processing is required for the unmeasured surface element whose estimated uncut remaining amount does not exceed the required measurement range, and the measurement surface element whose measurement result does not exceed the allowable maximum remaining value of the unmeasured surface elements. A correction machining method for an NC machine tool, characterized in that a judgment is made. In any one of Claim 1 to Claim 3,
The NC machine tool correction processing method according to claim 1, wherein the surface characteristic is a characteristic related to a shape and a dimension of each surface element. A table for holding a workpiece, a spindle on which a tool is mounted, a data storage unit for storing reference NC data for machining the workpiece into a target shape, and a spindle according to the reference NC data stored in the data storage unit And an NC machine tool configured to move the table relatively and control the workpiece into the target shape with the tool,
A measuring device for measuring the shape of the workpiece held on the table;
The data storage unit
Storing a plurality of sections classified by surface characteristics into a plurality of surface elements constituting the work surface of the workpiece, and an error coefficient corresponding to an uncut amount based on the surface characteristics for each section;
The controller is
A classifying means for classifying a plurality of surface elements of the workpiece machined by the reference NC data into the plurality of sections;
Measuring means for measuring a reference point set on at least one of the plurality of surface elements by the measuring device;
Detecting means for obtaining a reference point uncut amount from the measured value of the reference point;
Calculate the estimated uncut amount of each unmeasured surface element from the relationship between the error coefficient of the category to which the surface element with the reference point belongs and the error coefficient of the category to which each unmeasured surface element belongs and the uncut amount of the reference point Computing means for
Determination means for determining whether or not correction processing of each unmeasured surface element is necessary based on the calculation result of the estimated uncut amount;
NC machine tool characterized by comprising In claim 5,
The NC machine tool, wherein the surface characteristic is a characteristic related to a shape and a dimension of each surface element.

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