Calibration unit and calibration method

Abstract

To provide a calibration unit capable of performing highly accurate calibration.SOLUTION: A calibration unit has a triangular column shape whose tops are a step gauge (22) having a known step between two surfaces (30A, 32A) in parallel to each other, a ball gauge (26) having a known radius, and an edge (48) along a Y-axis direction orthogonal to an X-axis direction and a Z-axis direction, and includes an edge unit (40) including a first inclined surface (44) and a second inclined surface (46) sandwiching the edge and an edge gauge (26) whose edge has a tip radius (R) less than a radius of the ball gauge. The step gauge, the edge gauge, and the ball gauge are arranged in order in the X-axis direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to the calibration of a shape measuring machine that measures the shape of a workpiece. [Background technology]

[0002] Patent Document 1 describes a method for calibrating a measuring machine in which a stylus is used to trace a reference gauge, and the obtained measurement data is compared with known shape dimensional values ​​of the master shape portion of the reference gauge, and calculations are performed to calibrate the arm length, stylus height, and stylus tip radius. The calibration method described in this document uses a reference gauge with a sphere fixed to a flat surface, a reference gauge with two spheres, one large and one small, fixed to a flat surface, and a reference gauge with a cylinder fixed to a flat surface.

[0003] Patent Document 2 describes a method for calibrating a measuring machine using a step gauge and a ball gauge to calibrate the arm length, stylus height, and stylus tip radius. The calibration method described in this document uses the measurement results of the ball gauge to temporarily calibrate the arm length and stylus height, and then uses the measurement results of the step gauge to calibrate the arm length, stylus height, and stylus tip radius.

[0004] On the other hand, in the calibration method described in the same document, which uses a ball gauge and a step gauge, there is a problem in that errors in the arcuate motion of the stylus are superimposed on the measurement results.

[0005] Patent Document 3 describes a method for calibrating a measuring machine, which uses a step gauge, a first ball gauge, and a second ball gauge to calibrate the arm length, the stylus height, and the tip radius of the stylus. The calibration method described in this document calibrates the tip radius of the stylus by using a second ball gauge with a smaller radius than the first ball gauge in order to reduce errors caused by the circular motion of the stylus.

[0006] Patent Document 4 describes a tool for measuring the machining accuracy of a stylus tip. The tool described in this document is equipped with a razor blade with a cutting edge angle of 30 degrees or less. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 09-329402 [Patent Document 2] Japanese Patent Application Publication No. 10-332304 [Patent Document 3] JP 2015-175704 A [Patent Document 4] Japanese Utility Model Application Publication No. 05-059208 Summary of the Invention [Problem to be solved by the invention]

[0008] Calibration methods and calibration accuracy are improving day by day. Accordingly, the measurement accuracy required for shape measuring instruments is also increasing. In addition, the workpieces to be measured are becoming smaller, so even a slight measurement error can affect the measurement results.

[0009] There is concern that the inventions described in Patent Documents 1 to 3 may not provide sufficient measurement accuracy when measuring a miniaturized object. The jig described in Patent Document 4 is used to measure the machining accuracy of the stylus tip, and is not used to calibrate the stylus tip radius. If it were used to calibrate the stylus tip radius, there would be concerns about insufficient rigidity and durability.

[0010] The present invention has been made in view of the above circumstances, and has an object to provide a calibration unit that enables highly accurate calibration. [Means for solving the problem]

[0011] In order to achieve the above object, the following aspects of the invention are provided.

[0012] The calibration unit of the first embodiment is a shape measuring machine calibration device that calibrates a shape measuring machine that measures the shape of a workpiece using a stylus that is supported so as to be freely movable in the X-axis direction and is provided at the tip of an arm that is supported so as to be rotatable about the XZ plane using a rotation fulcrum, and the calibration unit is equipped with: a step gauge having two parallel sides and a known step difference between the two sides; a ball gauge having a known radius; and an edge gauge that has a triangular prism shape with an edge along the Y-axis direction perpendicular to the X-axis direction and the Z-axis direction as its apex, and has an edge portion that includes a first inclined surface and a second inclined surface that sandwich the edge, and the edge has a tip radius that is less than the radius of the ball gauge.

[0013] According to the first aspect, the tip radius of the stylus is calibrated using edge measurement data obtained by measuring the edge gauge and the design value of the edge. This makes it possible to calibrate the tip radius of the stylus with high accuracy without being affected by the sphericity of the ball gauge, which is a problem when calibrating the tip radius of the stylus using a ball gauge.

[0014] The edge may have a prescribed length in the Y-axis direction. The prescribed length may be determined from manufacturing conditions of the edge gauge and conditions of use of the edge gauge.

[0015] A moving mechanism may be provided that moves the positions of the step gauge, edge gauge, and ball gauge in the Y-axis direction. A moving mechanism may be provided that moves the step gauge and edge gauge together in the Y-axis direction.

[0016] In a second aspect, in the calibration unit of the first aspect, the first inclined surface and the second inclined surface may have an angle of 80 degrees or less.

[0017] According to the second aspect, when measuring the contact angle of a groove shape, it is possible to suppress measurement errors in the contact angle caused by the superposition of calibration errors in the tip radius of the stylus.

[0018] A third aspect may be configured such that in the calibration unit of the first or second aspect, the tip radius of the edge is 0.1 micrometers or less.

[0019] According to the third aspect, it is possible to suppress a calibration error caused by the shape of the edge superimposed on the tip radius of the stylus.

[0020] A fourth aspect is a shape measuring machine calibration device according to any one of claims 1 to 3, wherein in the calibration unit of any one of the first to third aspects, the length of the edge in the Y-axis direction is less than the radius of the ball gauge.

[0021] According to the fourth aspect, the edge gauge can be manufactured with high accuracy.

[0022] A fifth aspect may be configured such that in the calibration unit according to any one of the first to fourth aspects, the material of the edge portion is diamond.

[0023] According to the fifth aspect, the edge portion can be manufactured by highly accurate micromachining, and the edge portion can have a certain degree of rigidity.

[0024] A calibration unit according to a sixth aspect calibrates a shape measuring machine that measures the shape of an object to be measured using a stylus that is supported movably in the X-axis direction and is provided at the tip of an arm that is supported rotatably about the XZ plane using a rotation fulcrum, and is a shape measuring machine calibration device that includes a calibration unit and a signal processing unit, wherein the calibration unit includes a step gauge having two parallel surfaces and a step difference between the two surfaces is known, a ball gauge having a known radius, and an edge gauge that has a triangular prism shape with an edge along a Y-axis direction perpendicular to the X-axis direction and a Z-axis direction as its apex, and includes an edge portion including a first inclined surface and a second inclined surface that sandwich the edge, and the edge has a tip radius that is less than the radius of the ball gauge, and the signal processing unit calculates a design value of the step gauge, a design value of the ball gauge, and a design value of the edge gauge. a design value acquisition unit that acquires design value data from a step gauge measured using the stylus, a step measurement data acquisition unit that acquires step measurement data obtained by measuring a step gauge using the stylus, a ball measurement data acquisition unit that acquires ball measurement data obtained by measuring a ball gauge using the stylus, and an edge measurement data acquisition unit that acquires edge measurement data obtained by measuring an edge gauge using the stylus; and a calibration unit that calibrates the stylus height, which is the distance in the Z-axis direction from the rotation fulcrum to the tip of the stylus when the arm is horizontally in a position parallel to the X-axis direction, and the arm length, which is the distance in the X-axis direction from the rotation fulcrum to the stylus, using the step measurement data, ball measurement data, design value of the step gauge, and design value of the ball gauge, and calibrates the tip radius of the stylus using the edge measurement data and the design value of the edge gauge.

[0025] According to the sixth aspect, it is possible to obtain the same effects as those of the first aspect.

[0026] In the sixth aspect, the same items as those specified in the second to fifth aspects can be appropriately combined. In this case, the components performing the processes or functions specified in the calibration unit can be understood as the components of the shape measuring machine calibration device performing the corresponding processes or functions.

[0027] In a seventh aspect, in the shape measuring machine calibration device of the sixth aspect, the calibration unit may be configured to provisionally calibrate the tip radius of the stylus using the edge measurement data and a design value of the edge gauge, and to calibrate the arm length and the stylus height using the provisionally calibrated tip radius of the stylus.

[0028] According to the seventh aspect, the tip radius of the stylus is provisionally calibrated using edge measurement data obtained by measuring the edge gauge and a design value of the edge. The provisionally calibrated tip radius of the stylus is used to calibrate the arm length and the stylus height. This makes it possible to calibrate the arm length and the stylus height with high accuracy. Effect of the Invention

[0029] According to the present invention, the tip radius of the stylus is calibrated using edge measurement data obtained by measuring the edge gauge and the design value of the edge. This makes it possible to calibrate the tip radius of the stylus with high accuracy without being affected by the sphericity of the ball gauge, which is a problem when calibrating the tip radius of the stylus using a ball gauge. [Brief description of the drawings]

[0030] [Figure 1] FIG. 1 is a perspective view showing the overall configuration of the calibration unit. [Diagram 2] FIG. 2 is a front view of the edge gauge. [Diagram 3] FIG. 3 is a side view of the edge gauge. [Figure 4] FIG. 4 is an enlarged view of the edge portion shown in FIG. [Diagram 5] FIG. 5 is an enlarged view of the edge portion shown in FIG. [Figure 6] FIG. 6 is a schematic diagram of edge gauge measurement. [Figure 7] FIG. 7 is a schematic diagram showing the measurement results of the edge gauge. [Figure 8] FIG. 8 is a functional block diagram of the calibration device. [Figure 9] FIG. 9 is an explanatory diagram of the arm length and stylus height. [Figure 10]FIG. 10 is a flow chart showing the procedure of the calibration method. [Figure 11] FIG. 11 is a diagram showing the overall configuration of a contour measuring machine, which is an example of a shape measuring device. [Figure 12] FIG. 12 is an explanatory diagram of the problem. [Figure 13] FIG. 13 is an explanatory diagram of the problem. [Figure 14] FIG. 14 is an explanatory diagram of the problem. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In this specification, the same components as those described above are designated by the same reference numerals, and the description thereof will be omitted as appropriate.

[0032] [Problem description] First, a problem to be solved by the calibration device for a form measuring machine according to the present embodiment will be described in detail. Note that in the present embodiment, the calibration device for a form measuring machine may be simply referred to as a calibration device.

[0033] The measurement targets of contour measuring machines, such as linear guides and ball screws, are becoming smaller. This is in response to the demand for lower costs and environmental considerations, such as lower power consumption and fuel consumption. To reduce the power consumption and fuel consumption of ball screws and other components, the power source, such as motors, is also becoming smaller.

[0034] When ball screws and other devices are miniaturized, the accuracy of measurement of the roughness and shape of the raceway surface becomes important. If the accuracy of measurement of the roughness and shape of the raceway surface does not meet certain standards, it will cause load fluctuations, making it difficult to miniaturize the power side. In addition, there are concerns about the impact on performance, such as the generation of abnormal noise, and the impact on durability, such as wear on the balls.

[0035] Furthermore, linear motion guides have been commercialized in which the number of rolling grooves per unit length is increased and the rolling balls are made smaller in order to achieve higher rigidity and higher precision.

[0036] The measurement accuracy of the contact angle of the groove in a ball screw is becoming insufficient as the object to be measured becomes smaller. The contact angle is the angle between the line passing through the contact point between the raceway surface and the ball and the center of the raceway surface, and the perpendicular line drawn vertically from the center of the raceway surface. The contact points are shown in Figure 12 using the symbols 5, 6, 7, and 8. The contact angle is shown in Figure 12 using the symbols α and β.

[0037] The reason for the insufficient measurement accuracy is thought to be that the number of measurement points is reduced due to the miniaturization of the measured object, which leads to a large analysis error. In addition, in the evaluation of the contact angle, it is thought that the calculation accuracy of the tip radius of the stylus in the calibration of the probe is affecting the measurement accuracy.

[0038] 12 to 14, the reasons why the measurement accuracy is insufficient in the evaluation of the contact angle will be explained. Below, an example is shown in which the contact angle of a ball screw groove is derived by using a stylus with a calibrated tip radius by applying a ball gauge similar to the inventions described in Patent Documents 1 to 3.

[0039] Figures 12 to 14 are explanatory diagrams of the problem. Figure 12 shows a cross section of a ball screw groove. Figure 12 illustrates the case where the raceway surface is small and the case where the raceway surface is large, with the center O of the raceway surface coinciding.

[0040] Reference number 1 represents the orbital surface when the orbital surface is small. Reference number 2 represents the orbital surface when the orbital surface is large. Reference number 3 represents a sample circle for orbital surface 1. Reference number 4 represents a sample circle for orbital surface 2. Sample circle 3 is a circle calculated by applying the least squares method to the measured values ​​at all measurement points on orbital surface 1. The same is true for sample circle 4. For example, the radius of sample circle 3 is 2.0 micrometers. The radius of sample circle 4 is 10.0 micrometers.

[0041] Reference numerals 5 and 6 indicate contact points on raceway surface 1 derived as analytical results. Reference numerals 7 and 8 indicate contact points on raceway surface 2 derived as analytical results. Reference numerals α and β indicate contact angles derived from the contact points.

[0042] Reference numeral 9 denotes a stylus. Reference numerals 10, 11, and 12 denote line segments connecting the center O and the arcs when the angles from a perpendicular line 13 dropped from the center O are 44 degrees, 45 degrees, and 46 degrees, respectively, in the sample circles 3 and 4.

[0043] Figure 13 is an enlarged view of the vicinity of contact point 5 on raceway surface 1 shown in Figure 12. Reference numeral 1A denotes the measurement result of raceway surface 1 to which the provisional tip radius of the stylus 9 has been applied. Figure 14 is an enlarged view of the vicinity of contact point 7 on raceway surface 2 shown in Figure 12. Reference numeral 2A denotes the measurement result of raceway surface 2 to which the provisional tip radius of the stylus 9 has been applied.

[0044] Reference numeral 14 shown in Figures 13 and 14 indicates the fluctuation of the measurement result caused by the calibration error of the tip radius of the stylus 9. In this way, the calibration error of the tip radius of the stylus 9 may be superimposed on the measurement result. Here, reference numeral 5A shown in Figure 13 indicates the point that should have been identified as the contact point. Reference numeral 5 indicates the actually identified contact point.

[0045] In the example shown in Figure 13, an error in the tip radius of the stylus 9 is superimposed on the measurement result of the raceway surface 1, so that contact point 5A, which should have been derived, is actually contact point 5, which has an error of about 1 degree.

[0046] On the other hand, in the example shown in Fig. 14, as in the example shown in Fig. 13, fluctuations in the measurement results occur due to errors in the tip radius of the stylus 9, and the errors in the tip radius of the stylus 9 are superimposed on the measurement results of the raceway surface 2, but the contact point 7 that should have been derived is actually derived. Even if the deviation between the measurement results and the design value data is 0.1 micrometers, this results in an error of about 1 degree in contact angle.

[0047] The calibration method according to the prior art does not pose a problem for measurements such as the example shown in FIG. 14, but it can be problematic when measuring the grooves of a miniaturized ball screw, as in the example shown in FIG. 13.

[0048] The inventions described in Patent Documents 1 to 3 are premised on the ball gauge being a perfect sphere, but the inventors focused on the practical difficulty of producing a perfect sphere and considered that deviation from a perfect sphere in an actual ball gauge could result in a calibration error in the tip radius of the stylus 9. They then discovered that, as shown in Figure 13, the effect of a calibration error in the tip radius of the stylus 9 could become apparent in shape measurement of a miniaturized workpiece.

[0049] The calibration device and calibration method described below are intended to solve new technical problems that have not been made apparent by calibration according to conventional techniques, which the inventors have focused on.

[0050] [Calibration unit configuration example] Fig. 1 is a perspective view showing an overall configuration of a calibration unit. The calibration device according to this embodiment includes a calibration unit 20 shown in Fig. 1. The calibration unit 20 includes a step gauge 22, an edge gauge 24, and a ball gauge 26. In the calibration unit 20, the step gauge 22, the edge gauge 24, and the ball gauge 26 are arranged along a first direction.

[0051] The step gauge 22 has a structure in which a block gauge 32 is attached onto a reference base 30. The thickness of the block gauge 32 is known, and a step dimension H0, which is the distance between an upper surface 30A of the reference base 30 and an upper surface 32A of the block gauge 32, is also known. The upper surface 30A of the reference base 30 and the upper surface 32A of the block gauge 32 correspond to an example of two surfaces parallel to each other.

[0052] The edge gauge 24 is supported by a holder (not shown). The edge gauge 24 has a structure in which an edge portion 40 is exposed from the upper surface 20A of the calibration unit 20. The step gauge 22 and the edge gauge 24 are supported by a first moving mechanism 28 so as to be movable in the second direction.

[0053] The ball cage 26 is supported on the upper end of the support 50. The sphericity and radius of the ball cage 26 are accurately calculated in advance. The ball cage 26 is supported by a second moving mechanism 29 so as to be movable in the second direction.

[0054] Here, the first direction corresponds to the X-axis direction when the calibration unit 20 is placed on a shape measuring machine, and the second direction corresponds to the Y-axis direction when the calibration unit 20 is placed on a shape measuring machine.

[0055] [Example of edge gauge structure] Fig. 2 is a front view of the edge gauge. Fig. 3 is a side view of the edge gauge. As shown in Figs. 2 and 3, the edge gauge 24 includes an edge portion 40, an edge support portion 41, and a fixing portion .

[0056] The edge portion 40 is disposed at the tip of the fixing portion 42. The edge support portion 41 supports a lower portion of the edge portion 40. The fixing portion 42 supports the edge portion 40 supported by the edge support portion 41, and is supported by the calibration unit 20 shown in FIG. 1 using a holder (not shown).

[0057] Fig. 4 is an enlarged view of the edge portion shown in Fig. 2. In Fig. 4, the edge 48 is further enlarged and illustrated. The edge portion 40 includes a first inclined surface 44, a second inclined surface 46, and an edge 48. The edge portion 40 has a triangular prism shape with the edge 48 as the apex.

[0058] The edge portion 40 has a first inclined surface 44 on one side of the edge 48 and a second inclined surface 46 on the other side of the edge 48 in a second direction perpendicular to the first direction in which the edge 48 extends.

[0059] The first inclined surface 44 and the second inclined surface 46 form a specified angle. The cross-sectional shape of the edge portion 40 in a front cross section parallel to the paper surface of Fig. 4 is a triangle. The cross-sectional shape of the front cross section of the edge portion 40 is preferably an isosceles triangle or an equilateral triangle.

[0060] The prescribed angle θ between the first inclined surface 44 and the second inclined surface 46 is 80 degrees or less. From the viewpoint of calibration of the tip radius of the stylus, the smaller the angle θ, the better. A lower limit value of the angle θ may be prescribed based on the manufacturing conditions and the usage conditions of the edge gauge 24.

[0061] The tip radius R of the edge 48 can be less than the radius of the ball gauge 26. The smaller the tip radius R of the edge 48, the smaller the calibration error of the tip radius of the stylus can be. The tip radius R of the edge 48 is preferably 0.1 micrometers or less. The stylus is illustrated in FIG. 6 with the reference numeral 49.

[0062] Fig. 5 is an enlarged view of the edge portion shown in Fig. 3. Fig. 5 is a view of the edge portion 40 viewed from the side of the first inclined surface 44 shown in Fig. 4. As shown in Fig. 5, the edge 48 has a specified length in the second direction. The length of the edge 48 in the second direction is specified in consideration of manufacturing constraints of the edge portion 40, durability constraints, and the like.

[0063] If the length of the edge 48 in the second direction is increased, it is difficult to manufacture with high precision the edge portion 40. For example, if the length of the edge 48 in the second direction is less than the radius of the ball gauge 26, the edge portion 40 can be manufactured with high precision.

[0064] 5, the planar shape of the edge portion 40 as viewed in the first direction is a trapezoid. Note that the planar shape of the edge portion 40 as viewed in the first direction may be a quadrangle other than a trapezoid, such as a rectangle.

[0065] Diamond is an example of a material for the edge portion 40. By using diamond for the edge portion 40, it is possible to set the tip radius R of the edge 48 to 0.05 micrometers or less.

[0066] The tip of the stylus for measuring small workpieces is not a sphere, but a cone shape with a small tip radius. The small workpieces mentioned here are assumed to be linear guides with rolling balls with a diameter of about 1.0 mm, ball screws, etc. The workpiece corresponds to an example of the object to be measured.

[0067] During measurement, the contact position between the workpiece and the tip of the stylus changes continuously. When measuring a small workpiece using a stylus with a tip diameter of about 0.5 to 1.0 mm, the measurement position does not change continuously, which can lead to variations in the contact point and detection of multiple contact points.

[0068] Therefore, the tip radius of a stylus for measuring a small workpiece is set to 2.0 micrometers, 5.0 micrometers, etc. When the tip radius is 2.0 micrometers, etc., diamond is used as the material for the tip of the stylus.

[0069] When the tip of the stylus is diamond, the edge gauge 24 that measures the tip of the stylus needs to have a hardness equal to or greater than that of the tip of the stylus, so diamond is used as the material for the edge portion 40 of the edge gauge 24 shown in Figure 2, etc.

[0070] It should be noted that the small workpieces described above are merely examples, and workpieces that have groove shapes and hole shapes of about 1.0 mm and that use a stylus with a tip radius of 2.0 micrometers or the like during measurement can be included in the concept of a small workpiece herein.

[0071] [Advantages of calibrating the stylus tip radius using an edge gauge] Fig. 6 is a schematic diagram of edge gauge measurement. Fig. 6 is a schematic diagram of measurement of the edge gauge 24 using a stylus 49. As shown in Fig. 6, the stylus 49 is moved in the X-axis direction, and the tip 49A of the stylus 49 is brought into contact with the first inclined surface 44, the edge 48, and the second inclined surface 46 in that order, to measure the edge gauge 24.

[0072] 7 is a schematic diagram showing the measurement results of the edge gauge. The result waveform 60 shown in FIG. 7 includes a first waveform element 62 which is a measurement result of the first inclined surface 44, a second waveform element 64 which is a measurement result of the edge 48, and a third waveform element 66 which is a measurement result of the second inclined surface 46.

[0073] 7, the radius of tip 49A of stylus 49 that measured edge 48 appears, but is hardly affected by tip radius R of edge 48 since the measurement target is edge 48.

[0074] [Function block diagram] 8 is a functional block diagram of the calibration device. The calibration device according to this embodiment includes a signal processing unit 70. The signal processing unit 70 includes a measurement value acquiring unit 71 and a design value acquiring unit 72. The measurement value acquiring unit 71 acquires measurement data of the step gauge 22, edge gauge 24, and ball gauge 26 output from the detection unit of the shape measuring machine. The data here includes one or more measurement values.

[0075] The measurement value acquiring unit 71 may include a step measurement data acquiring unit that acquires measurement data of the step gauge 22, an edge measurement data acquiring unit that acquires measurement data of the edge gauge 24, and a ball measurement data acquiring unit that acquires measurement data of the ball gauge 26. The acquired measurement data is stored using a measurement data storage unit (not shown).

[0076] The design value acquisition unit 72 acquires design values ​​of the step gauge 22, the edge gauge 24, and the ball gauge 26. Like the measurement value acquisition unit 71, the design value acquisition unit 72 may acquire the design values ​​of the step gauge 22, the edge gauge 24, and the ball gauge 26 individually. The acquired design values ​​are stored using a design value storage unit (not shown). The design value acquisition unit 72 may acquire the design values ​​by reading out each design value stored in advance.

[0077] The signal processing unit 70 includes a processing unit 74, a data storage unit 76, a calibration unit 78, a calibration data storage unit 80, and a calibration data output unit 82. The processing unit 74 executes signal processing such as calculations using design values ​​and measured values. The results of the signal processing performed by the processing unit 74 are stored in the data storage unit 76.

[0078] The calibration unit 78 generates calibration data for the arm length, calibration data for the stylus height, and calibration data for the stylus tip radius using the results of signal processing using the processing unit 74. The calibration unit 78 can generate calibration data for the arm length and calibration data for the stylus height using the step measurement data, the ball measurement data, the step design value, and the ball design value.

[0079] When generating the calibration data for the arm length and the calibration data for the stylus height, the calibration unit 78 may generate provisional calibration data for the stylus tip radius using the edge measurement data and the edge design value.

[0080] The calibration unit 78 can also generate calibration data for the stylus tip radius using the edge measurement data and the edge design value. Various calibration data generated by the calibration unit 78 is stored in a calibration data storage unit 80.

[0081] The calibration unit 78 transmits the calibration data of the arm length, the calibration data of the stylus height, and the calibration data of the stylus tip radius to the control unit of the shape measuring device via the calibration data output unit 82. The shape measuring device can measure the workpiece using the various calibration data transmitted from the signal processing unit 70 of the calibration device.

[0082] The function of the signal processing unit 70 of the calibration device shown in Fig. 8 can be realized by executing a program using hardware. The hardware can be configured using a processor, a memory, a storage device, and a communication interface. An example of the processor is a CPU (Central Processing Unit).

[0083] Examples of the memory include a read only memory (ROM) and a random access memory (RAM). Examples of the storage device include a hard disk device and a storage device.

[0084] [Calibration method explanation] [Parameters applied to the calibration method] Fig. 9 is an explanatory diagram of parameters applied to the calibration method. Fig. 9 shows a schematic configuration of a detector 100 provided in a shape measuring instrument. Reference numeral 102 denotes a stylus. Reference numeral 102A denotes the tip of the stylus 102. The stylus 102 shown in Fig. 9 corresponds to the stylus 49 shown in Fig. 6.

[0085] Reference numeral 104 denotes an arm. Reference numeral 104A denotes the tip of the arm 104. Reference numeral 106 denotes a rotation fulcrum. Reference numeral 108 denotes a sensor. The arm 104 illustrated in Fig. 9 using a two-dot chain line represents a horizontal state in which the arm 104 is supported parallel to the X-axis direction.

[0086] The stylus 102 is fixed to the tip of an arm 104. The arm 104 is supported rotatably about the XZ plane using a rotation fulcrum 106. The tip of the arm 104 includes a tip 104A of the arm 104 and represents a region having a certain length from the tip 104A of the arm 104.

[0087] LH1 is the arm length. The arm length LH1 is the distance from the rotation fulcrum 106 to the tip 104A of the arm 104. LV1 is the stylus height. The stylus height LV1 is the total length of the stylus 102. The stylus height LV1 is the distance in the Z-axis direction from the rotation fulcrum 106 to the tip 102A of the stylus 102 when the arm 104 is in a horizontal position.

[0088] LH2 is the distance in the X-axis direction from the rotation fulcrum 106 to the sensor 108 when the arm 104 is in the horizontal state. LV2 is the distance in the Z-axis direction from the rotation fulcrum to the sensor 108. θ represents the inclination angle of the arm 104 with respect to the horizontal state of the arm 104.

[0089] x0i represents the i-th sample point of the detection signal of a scale (not shown). z0i represents the i-th sample point of the detection signal of the sensor 108. (x1i, z1i) represents the coordinates of the position of the tip 102A of the stylus 102 corresponding to the i-th sample point.

[0090] θ is expressed using the following formula 1. x1i is expressed using the following formula 2. z1i is expressed using the following formula 3.

[0091]

number

[0092] 9 is expressed by the following formula 4. L2 is expressed by the following formula 5. θ1 is expressed by the following formula 6. θ2 is expressed by the following formula 7.

[0093]

number

[0094] [Procedure for calibration method] Fig. 10 is a flow chart showing the procedure of the calibration method. In the measurement value acquisition step S10, the design value acquisition unit 72 shown in Fig. 8 acquires the design value of the step gauge 22, the design value of the edge gauge 24, and the design value of the ball gauge 26. A design value storage step may be executed to store each of the acquired design values. After the measurement value acquisition step S10, the process proceeds to the ball gauge measurement step S12.

[0095] In the ball gauge measurement step S12, the measurement value acquisition unit 71 acquires measurement data of the ball gauge 26. A storage step may be executed to store the acquired measurement data. After the ball gauge measurement step S12, the process proceeds to a step gauge measurement step S14.

[0096] In the step gauge measurement step S14, the measurement value acquisition unit 71 acquires measurement data of the step gauge 22. A storage step may be executed to store the acquired measurement data. After the step gauge measurement step S14, the process proceeds to an edge gauge measurement step S16.

[0097] In the edge gauge measurement step S16, the measurement acquisition unit 71 acquires measurement data of the edge gauge 24. A storage step may be executed to store the acquired measurement data. After the edge gauge measurement step S16, the process proceeds to a stylus tip radius provisional calibration step S18.

[0098] In the stylus tip radius temporary calibration step S18, the calibration unit 78 uses the edge measurement data to derive temporary calibration data for the stylus tip radius. After the stylus tip radius temporary calibration step S18, the process proceeds to an evaluation function value calculation step S20.

[0099] In the evaluation function value calculation step S20, the processing unit 74 calculates a specified evaluation function value using the step measurement data and the ball measurement data. The sum of the following items can be defined as the evaluation function.

[0100] <1> Square of the difference between the step calculated from the step measurement data and the known step dimension H0 <2> Squared circularity of ball measurement data Circularity is the maximum deviation from a least squares circle.

[0101] <3> Symmetry of ball measurement data The symmetry of the ball measurement data is determined by applying the square of the difference between the left and right R values ​​when A is set to 90 degrees plus or minus γ in the polar coordinate data (A, R). The origin of the polar coordinate is the center of the least squares circle.

[0102] It is to be noted that multiple ball measurement data with different measurement ranges in the Z-axis direction may be applied as the ball measurement data. When multiple ball measurement data are obtained, the evaluation function may include the shape error between the ball measurement data as an item of the evaluation function described above.

[0103] After the evaluation function value calculation step S20, the process proceeds to a convergence determination step S22. In the convergence determination step S22, the calibration unit 78 determines whether or not the evaluation function value calculated in the evaluation function value calculation step S20 converges. If the evaluation function value calculated in the evaluation function value calculation step S20 does not converge, the result is No. If the result is No, the process proceeds to an optimization calculation step S24.

[0104] In the optimization calculation step S24, the calibration unit 78 executes the optimization calculation until the evaluation function value calculated in the evaluation function value calculation step S20 converges. That is, each step from the stylus tip radius temporary calibration step S18 to the convergence determination step S22 is repeatedly executed until the convergence determination step S22 is judged as Yes.

[0105] That is, the calibration unit 78 performs optimization calculations until the evaluation function value calculated in the evaluation function value calculation step S20 converges, and calculates optimal calibration data for the arm length LH1 and optimal calibration data for the stylus height LV1.

[0106] On the other hand, if it is determined in the convergence determination step S22 that the evaluation function value has converged, a Yes determination is made. If the Yes determination is made, the process proceeds to a stylus tip calibration step S26. If the Yes determination is made, a storage step of storing each calibration data may be executed.

[0107] In the stylus tip calibration step S26, the calibration unit 78 uses the edge measurement data to calculate optimal calibration data for the stylus tip radius provisionally calibrated in the stylus tip radius provisional calibration step S18. After the stylus tip calibration step S26, a storage step may be executed to store the calibration data for the stylus tip radius.

[0108] Using the calibration method described above, the calibration data of LH2 and LV2 shown in Fig. 9 can be derived. Note that the calibration method described here is just one example, and other calibration methods may be applied in which the step measurement data and ball measurement data are used to calibrate the arm length LH1 and the stylus height, and the edge measurement data is used to calibrate the stylus tip radius.

[0109] [Effects] According to the calibration device and calibration method configured as above, the following advantageous effects can be obtained.

[0110] [1] The stylus tip radius is calibrated using an edge gauge. The tip of the edge of the edge gauge has a radius of 0.1 micrometers or less. This suppresses calibration errors caused by the roundness of the ball gauge when the stylus tip radius is calibrated using a ball gauge.

[0111] [2] The angle of the edge gauge is set to 80 degrees or less, which is suitable for measuring the contact angle in the groove of a small ball screw.

[0112] [3] Diamond is applied to the material of the edge of the edge gauge. This allows the edge to be manufactured with high precision. In addition, a certain durability of the edge can be ensured. Furthermore, the tip of the stylus to which diamond is applied can be calibrated.

[0113] [Equipment application examples] The above-mentioned calibration device and the calibration method can be applied to a shape measuring device. Fig. 11 is a diagram showing the overall configuration of a contour measuring machine, which is an example of a shape measuring device. In Fig. 11, the same components as those shown in Fig. 9 are assigned the same reference numerals.

[0114] The contour measuring machine 120 shown in Fig. 11 includes a measuring unit 122 and a data processing unit 124. The measuring unit 122 includes a feed device 130. The feed device 130 is supported so as to be movable in the Z-axis direction by a column 134 erected on a base 132. The feed device 130 includes a built-in scale 136 that detects displacement in the X-axis direction.

[0115] The measuring unit 122 includes a detector 100. The detector 100 is supported so as to be freely movable in the X-axis direction by using a feed device 130. The detector 100 includes a stylus 102, an arm 104, and a sensor 108. The structure of the detector 100 is as described with reference to Fig. 9. Here, a description of the detector 100 will be omitted.

[0116] The contour measuring machine 120 includes a control device (not shown). The control device executes a measurement program to automatically measure the contour of the workpiece W. The control device can control the operation of the X-axis direction moving mechanism and the Z-axis direction moving mechanism based on a specified measurement procedure. The control unit may share the same hardware as the data processing unit 124.

[0117] The data processing unit 124 includes a computer 140. The computer 140 includes a keyboard 142 and a mouse 144. The computer 140 is connected to a monitor device 146.

[0118] The computer 140 includes a measurement data input unit (not shown) that is communicatively connected to a scale detection signal detector that outputs a scale detection signal for outputting a detection signal of the scale 136, and a sensor detection signal detector that outputs a detection signal of the sensor 108.

[0119] The computer 140 includes a design value acquisition unit (not shown). The design value acquisition unit acquires the design values ​​of the workpiece W. The computer 140 includes a calibration data acquisition unit and a calibration data storage unit (not shown). The calibration data acquisition unit acquires various calibration data derived using a calibration device. The calibration data storage unit stores the acquired various calibration data. The various calibration data include the above-mentioned calibration data for the arm length LH1, calibration data for the stylus height LV1, and calibration data for the stylus radius.

[0120] That is, the computer 140 acquires measurement data at each measurement point in measuring the contour shape of the workpiece W. The computer 140 calculates the contour shape of the workpiece W based on the acquired measurement data. The computer 140 can display the measurement data of the workpiece W and the contour shape of the workpiece W using the monitor device 146.

[0121] The contour measuring machine 120 may include the signal processing unit shown in Fig. 8. For example, the computer 140 shown in Fig. 11 may include hardware and software that realizes the functions of the signal processing unit 70 of the calibration device.

[0122] When calibrating the arm length LH1, stylus height LV1, and stylus tip radius in the contour measuring instrument 120 shown in Fig. 11, the calibration unit 20 shown in Fig. 1 is placed on the upper surface of the base 132. At that time, the edge 48 of the edge gauge 24 is aligned with the Y-axis direction. The alignment here may include an allowable error range.

[0123] In this example, a contour measuring instrument is exemplified, but the above-mentioned calibration device can also be applied to a roughness measuring instrument and a combination instrument of a roughness measuring instrument and a contour measuring instrument.

[0124] The above-described embodiment of the present invention may be modified, added, or deleted as appropriate within the scope of the gist of the present invention. The present invention is not limited to the above-described embodiment, and many modifications may be made by a person having ordinary knowledge in the relevant field within the technical concept of the present invention. [Explanation of symbols]

[0125] 20...calibration unit, 22...step gauge, 24...edge gauge, 26...ball gauge, 40...edge portion, 44...first inclined surface, 46...second inclined surface, 48...edge, 70...signal processing portion, 71...measurement value acquisition portion, 72...design value acquisition portion, 74...processing portion, 78...calibration portion, 82...calibration data output portion

Claims

1. 1. A calibration unit for calibrating a shape measuring machine that measures a shape of a workpiece using a stylus provided at a tip of an arm that is supported so as to be movable in an X-axis direction and rotatably supported about an XZ plane using a rotation fulcrum, comprising: A step gauge having two parallel surfaces and a step difference between the two surfaces is known; A ball gauge with a known radius and an edge gauge having a triangular prism shape with an edge along a Y-axis direction perpendicular to the X-axis direction and the Z-axis direction as a vertex, the edge gauge including an edge portion including a first inclined surface and a second inclined surface sandwiching the edge, the edge having a tip radius less than the radius of the ball gauge; a movement mechanism that supports the step gauge and the edge gauge so as to be movable in the Y-axis direction; Equipped with a calibration unit, the step gauge, the edge gauge, and the ball gauge being arranged in this order in the X-axis direction;

2. The calibration unit of claim 1 , wherein the first inclined surface and the second inclined surface have an angle of less than 80 degrees.

3. 3. A calibration unit according to claim 1 or 2, wherein the tip radius of the edge is 0.1 micrometers or less.

4. A calibration unit according to claim 1 , wherein the length of the edge in the Y-axis direction is less than a radius of the ball gauge.

5. 5. A calibration unit according to claim 1, wherein the edge portion is made of diamond.

6. 1. A calibration method applied to a calibration unit that calibrates a shape measuring machine that measures a shape of a workpiece using a stylus provided at a tip of an arm that is supported so as to be movable in an X-axis direction and rotatably supported about an XZ plane using a rotation fulcrum, comprising: The calibration unit includes: A step gauge having two parallel surfaces and a step difference between the two surfaces is known; A ball gauge with a known radius and an edge gauge having a triangular prism shape with an edge along a Y-axis direction perpendicular to the X-axis direction and the Z-axis direction as a vertex, the edge gauge including an edge portion including a first inclined surface and a second inclined surface sandwiching the edge, the edge having a tip radius less than the radius of the ball gauge; a movement mechanism that supports the step gauge and the edge gauge so as to be movable in the Y-axis direction; the step gauge, the edge gauge, and the ball gauge are arranged in this order in the X-axis direction; acquiring a design value of the step gauge, a design value of the ball gauge, and a design value of the edge gauge; acquiring step measurement data obtained by measuring the step gauge using the stylus; obtaining ball measurement data obtained by measuring the ball gauge using the stylus; acquiring edge measurement data obtained by measuring the edge gauge using the stylus; using the step measurement data, the ball measurement data, the design value of the step gauge, and the design value of the ball gauge, calibrating a stylus height, which is the distance in the Z-axis direction from the rotation fulcrum to the tip of the stylus when the arm is in a horizontal state parallel to the X-axis direction, and an arm length, which is the distance in the X-axis direction from the rotation fulcrum to the stylus; A calibration method in which the edge measurement data and a design value of the edge gauge are used to calibrate the tip radius of the stylus.

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