Apparatus for manufacturing cylindrical materials and method for manufacturing cylindrical materials

Abstract

To enable the ability to judge the quality of tool marks. [Solution] The surface texture inspection device includes an imaging unit that captures the outer surface of a cylindrical material cut by a cutting device and generates an image; a two-dimensional Fourier transform unit that performs a two-dimensional Fourier transform on the image and calculates the intensity for each spatial frequency; and an inspection unit that inspects the surface texture of the outer surface of the cylindrical material based on the peak intensity for each spatial frequency. The inspection unit determines that the cylindrical material is defective if the peak exceeds a threshold.

Description

Technical Field

[0001] The present invention relates to an apparatus and method for manufacturing a cylindrical or tubular cylindrical material. More specifically, the present invention relates to an apparatus and method for manufacturing a cylindrical or tubular cylindrical material, having a cutting device for cutting the outer peripheral surface of the cylindrical or tubular cylindrical material, and a surface property inspection device for inspecting the surface property of the outer peripheral surface of the cylindrical or tubular cylindrical material cut by the cutting device.

Background Art

[0002] For example, the inspection of the surface property of the outer peripheral surface of a billet, which is the base material of a seamless steel pipe, is a visual inspection by an inspector, but it greatly depends on the skill of the inspector. Further, when a flaw occurs on the outer peripheral surface of the billet, maintenance work using a grinder or the like to eliminate the flaw is also added, resulting in a large work load and making the inspection work difficult. If the flaw leaks out, it has a problem of generating a large amount of flaws during pipe manufacturing in the downstream process. Therefore, automation of the inspection process is desired to prevent flaw leakage, rationalize personnel, and improve efficiency.

[0003] A billet is formed by subjecting a continuously cast cylindrical slab to cutting using a NC lathe or a manual lathe. Such cutting is performed to reduce friction during hot extrusion in the UOE pipe manufacturing process, which is one of the seamless steel pipe manufacturing methods, and to suppress the occurrence of wrinkles and flaws on the surface after pipe manufacturing. Further, by making the cross-sectional shape of the billet closer to a perfect circle, wall thickness variation after pipe manufacturing is also suppressed.

[0004] In addition to billets, there are many materials and products that are subjected to cutting on the outer peripheral surface of a cylindrical or tubular cylindrical material formed in a cylindrical or tubular shape. In the cutting of these materials and products, the cylindrical or tubular cylindrical material is rotated relative to a cutting tool in a direction around the axis of the cylindrical or tubular cylindrical material, the cutting tool is brought into contact with the outer peripheral surface of the cylindrical or tubular cylindrical material, and the cutting tool is moved relative to the cylindrical or tubular cylindrical material in the axial direction of the cylindrical or tubular cylindrical material, thereby cutting the outer peripheral surface of the cylindrical or tubular cylindrical material in a spiral shape.

[0005] In the above machining process, streak-like marks (hereinafter referred to as "tool marks") may appear on the outer surface of the cylindrical material due to the cutting tool. For example, if tool marks remain on the outer surface of a billet of cylindrical material, and these tool marks are defective, it can lead to quality assurance and yield problems, such as the occurrence of wrinkles in the steel pipe after manufacturing. Furthermore, the finished product may deviate from the specified surface roughness, resulting in a large number of defects and posing a similar problem. Therefore, it is necessary to judge the quality of the tool marks after machining. In addition, in order to prevent the occurrence of defective tool marks, it is necessary to identify the source of the defective tool marks.

[0006] Conventionally, the following techniques are known for inspecting the outer surface properties of cylindrical materials. For example, Patent Document 1 proposes a method for extracting damaged areas from an image by capturing the surface of a product including damaged areas and tool marks, and then applying a two-dimensional Fourier transform and a two-dimensional inverse Fourier transform to the captured image. Also, for example, Patent Document 2 proposes a method for acquiring defect information by capturing the surface of a product including defects such as scratches, and then applying a two-dimensional Fourier transform and a two-dimensional inverse Fourier transform to the captured image. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 08-128960 [Patent Document 2] Patent No. 2004-264054 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, the technologies described in Patent Documents 1 and 2 cannot determine whether tool marks are of good or bad quality. Furthermore, the technologies described in Patent Documents 1 and 2 cannot identify the source of poorly made tool marks.

[0009] The first object of the present invention is to provide a cylindrical material manufacturing apparatus and a cylindrical material manufacturing method that can determine the quality of a cylindrical material based on the intensity of tool marks. The second object of the present invention is to provide a cylindrical material manufacturing apparatus and a cylindrical material manufacturing method that can identify the source of defective tool marks. [Means for solving the problem]

[0010] A first aspect of the present invention, made to achieve a first objective, is a manufacturing apparatus for a cylindrical or cylindrical material, comprising: a cutting device for cutting the outer circumferential surface of the cylindrical material; and a surface quality inspection device for inspecting the surface quality of the outer circumferential surface of the cylindrical material cut by the cutting device, wherein the cutting device comprises: a rotating part for rotating the cylindrical material and the cutting tool relative to each other about a central axis which is an axis perpendicular to the circular cross-section of the cylindrical material; and a front part for bringing the cutting tool into contact with the outer circumferential surface of the cylindrical material and rotating the cylindrical material relative to the cutting tool by the rotating part. The manufacturing apparatus for cylindrical materials includes a cutting unit that moves a cutting tool relative to the cylindrical material in the axial direction of the cylindrical material to cut the outer surface of the cylindrical material in a spiral shape, and the surface quality inspection apparatus includes an imaging unit that images the outer surface of the cylindrical material cut by the cutting unit and generates an image, a two-dimensional Fourier transform unit that performs a two-dimensional Fourier transform on the image to calculate the intensity for each spatial frequency, and an inspection unit that inspects the surface quality of the outer surface of the cylindrical material by determining that the cylindrical material is defective when the peak of the intensity for each spatial frequency exceeds a threshold.

[0011] A second aspect of the present invention, made to achieve a second objective, is a manufacturing apparatus for a cylindrical or cylindrical material, comprising: a cutting device for cutting the outer circumferential surface of the cylindrical material; and a surface quality inspection device for inspecting the surface quality of the outer circumferential surface of the cylindrical material cut by the cutting device, wherein the cutting device comprises: a rotating section for relatively rotating the cylindrical material and a cutting tool about a central axis which is an axis perpendicular to the circular cross-section of the cylindrical material; and a cutting section for cutting the outer circumferential surface of the cylindrical material in a spiral manner by bringing the cutting tool into contact with the outer circumferential surface of the cylindrical material and moving the cylindrical material and the cutting tool, which are rotated relative to the cutting tool by the rotating section, in the axial direction of the cylindrical material. The surface condition inspection apparatus comprises an imaging unit that images the outer surface of the cylindrical material cut by the cutting device and generates an image; a two-dimensional Fourier transform unit that performs a two-dimensional Fourier transform on the image to calculate the intensity for each spatial frequency; and an inspection unit that inspects the surface condition of the outer surface of the cylindrical material based on the peaks of the intensity for each spatial frequency. The inspection unit determines that at least one of the cutting unit, the rotating unit, and the cylindrical material is defective if the spatial frequency of the peak is not the spatial frequency corresponding to the pitch, where the pitch is defined as the distance the cutting tool moves relative to the cylindrical material in the axial direction while the cylindrical material rotates once relative to the cutting tool.

[0012] A third aspect of the present invention has been made to achieve the first objective, and is a method for manufacturing a cylindrical material formed in the shape of a cylinder or cylindrical body, comprising: a cutting device for cutting the outer surface of the cylindrical material; and a surface quality inspection device for inspecting the surface quality of the outer surface of the cylindrical material cut by the cutting device, wherein the cutting device comprises: a rotating part for rotating the cylindrical material and the cutting tool relative to each other about a central axis which is an axis perpendicular to the circular cross-section of the cylindrical material; and the cylindrical material and the cutting tool for bringing the cutting tool into contact with the outer surface of the cylindrical material and rotating relative to the cutting tool by the rotating part. A method for manufacturing a cylindrical material, comprising: an imaging step of generating an image of the outer surface of the cylindrical material cut by the cutting device, using a cylindrical material manufacturing apparatus having a cutting unit that moves a cutting unit relative to the cylindrical material in the axial direction of the cylindrical material, the imaging step of generating an image of the outer surface of the cylindrical material cut by the cutting device, the two-dimensional Fourier transform step of calculating the intensity for each spatial frequency by performing a two-dimensional Fourier transform on the image of the image, and the inspection step of inspecting the surface properties of the outer surface of the cylindrical material by determining that the cylindrical material is defective when the peak of the intensity for each spatial frequency exceeds a threshold.

[0013] A fourth aspect of the present invention has been made to achieve a second objective, and is a method for manufacturing a cylindrical material formed in the shape of a cylinder or cylindrical body, comprising: a cutting device for cutting the outer circumferential surface of the cylindrical material; and a surface quality inspection device for inspecting the surface quality of the outer circumferential surface of the cylindrical material cut by the cutting device, wherein the cutting device comprises: a rotating part for rotating the cylindrical material and a cutting tool relative to each other about a central axis which is an axis perpendicular to the circular cross-section of the cylindrical material; and a cutting part for bringing the cutting tool into contact with the outer circumferential surface of the cylindrical material and moving the cylindrical material and the cutting tool, which are rotated relative to the cutting tool by the rotating part, relative to each other in the axial direction of the cylindrical material, thereby cutting the outer circumferential surface of the cylindrical material in a spiral manner. A method for manufacturing a cylindrical material, comprising: an imaging step of using a material manufacturing apparatus to image the outer surface of the cylindrical material cut by the cutting device and generate an image; a two-dimensional Fourier transform step of performing a two-dimensional Fourier transform on the image to calculate the intensity for each spatial frequency; and an inspection step of inspecting the surface properties of the outer surface of the cylindrical material based on the peaks of the intensity for each spatial frequency, wherein the inspection step determines that at least one of the cutting part, the rotating part, and the cylindrical material is defective if the spatial frequency of the peak is not the spatial frequency corresponding to the pitch, where the pitch is defined as the distance the cutting tool moves relative to the cylindrical material in the axial direction while the cylindrical material rotates once relative to the cutting tool. [Effects of the Invention]

[0014] The present invention provides a cylindrical material manufacturing apparatus and a cylindrical material manufacturing method that can determine the quality of the cylindrical material based on the intensity of tool marks. Furthermore, the present invention provides a cylindrical material manufacturing apparatus and a cylindrical material manufacturing method that can identify the source of defective tool marks. [Brief explanation of the drawing]

[0015] [Figure 1] This is a perspective view showing an example of a cutting apparatus and a cylindrical material, which are part of a manufacturing apparatus for cylindrical materials according to the first embodiment of the present invention. [Figure 2] It is a diagram showing an example of tool marks generated in the first and second processes in machining. [Figure 3] It is a perspective view showing an example of a surface property inspection device and a cylindrical material among manufacturing devices for cylindrical materials. [Figure 4] It is a side view showing an example of a rotation support device, an illumination imaging device, and a cylindrical material. [Figure 5] It is a front view showing an example of a rotation support device, an illumination imaging device, and a cylindrical material. [Figure 6] It is a plan view showing an example of an illumination imaging device. [Figure 7] It is a block diagram showing an example of the functional configuration of a processing device. [Figure 8] It is a diagram showing an example in which a plurality of captured images are generated by a plurality of imaging devices. [Figure 9] An example of generating an inspection image from a plurality of captured images is shown. [Figure 10] It is a diagram showing an example of an inspection image and a power spectrum obtained after the end of the first process. [Figure 11] It is a diagram showing an example of an inspection image and a power spectrum obtained after the end of the second process. [Figure 12] It is a block diagram showing an example of the hardware configuration of a processing device. [Figure 13] It is a flowchart showing an example of the flow of a method for manufacturing a cylindrical material according to the first embodiment of the present invention. [Figure 14] It is a flowchart showing an example of the flow of a method for manufacturing a cylindrical material according to the second embodiment of the present invention. [Figure 15] It is a plan view showing a first modification example of an illumination imaging device. [Figure 16] It is a plan view showing a second modification example of an illumination imaging device.

Embodiments for Carrying Out the Invention

[0016] [First Embodiment] First, a first embodiment of the present invention will be described.

[0017] Figure 1 shows an example of a cutting device 10A and a cylindrical material 12, which are part of a cylindrical material manufacturing apparatus 10 according to the first embodiment of the present invention. The cylindrical material 12 is formed in a cylindrical or cylindrical shape (hereinafter referred to as "cylindrical"). A cylindrical shape refers to a solid round bar with a circular cross-section, while a cylindrical shape refers to a hollow round bar with a circular cross-section. In the example shown in Figure 1, the cylindrical material 12 is formed in a cylindrical shape. The cylindrical material 12 is, as an example, a billet that will be the base material for a jointless steel pipe. The cylindrical material 12 can be anything other than a billet, as long as it is formed in a cylindrical shape. The cylindrical material 12 may be made of metal or other materials.

[0018] In order to explain the directions of the cylindrical material manufacturing apparatus 10 below, the X-axis direction, Y-axis direction, and Z-axis direction are defined. The X-axis direction is perpendicular to the cylindrical cross-section of the cylindrical material 12, the Z-axis direction is vertical, and the Y-axis direction is perpendicular to the X-axis direction and the Z-axis direction.

[0019] The cylindrical material manufacturing apparatus 10 is a device that cuts the outer surface of a cylindrical material 12 and then inspects the surface properties of the outer surface of the cylindrical material 12. The cylindrical material manufacturing apparatus 10 has a cutting device 10A as a device for cutting the outer surface of the cylindrical material 12. The cutting device 10A is, for example, an NC (Numerical Control) lathe. Since NC lathes are well known, the cutting device 10A will be briefly described here. The cutting device 10A has a rotating part 50 and a cutting part 52.

[0020] In the following explanation, the axis perpendicular to the circular cross-section is defined as the central axis 12A of the cylindrical material 12. The axial direction of the cylindrical material 12 refers to the direction along the central axis 12A of the cylindrical material 12. The outer surface of the cylindrical material 12 refers to the surface that exists in the direction around the axis of the cylindrical material 12 which is formed in a cylindrical shape. The radial direction of the cylindrical material 12 refers to the direction perpendicular to the central axis 12A of the cylindrical material 12.

[0021] The rotating part 50 is composed of a motor drive device or the like, and rotates the cylindrical material 12 in the direction of the axis of the cylindrical material 12. The cutting section 52 includes a moving section 54 and a cutting tool 56. The cutting tool 56 is a component used to cut the outer surface of the cylindrical material 12 by contacting it from the radially outer side of the cylindrical material 12, thereby removing scale from the cylindrical material 12 or processing the cross-sectional shape of the cylindrical material 12 to make it closer to a perfect circle. The moving unit 54 is composed of a motor drive device and the like, and moves the cutting tool 56 in the radial and axial directions of the cylindrical material 12. In the cutting process using the cutting device 10A, the rotating part 50 rotates the cylindrical material 12, and the moving part 54 moves the cutting tool 56 radially to bring the cutting tool 56 into contact with the outer surface of the cylindrical material 12. With the radial position of the cutting tool 56 fixed at this contact position, the moving part 54 moves the cutting tool 56 in the axial direction of the cylindrical material 12, thereby cutting the outer surface of the cylindrical material 12 in a spiral shape. In this cutting process, the cutting tool 56 moves a constant distance (hereinafter referred to as "pitch") in the axial direction of the cylindrical material 12 while the cylindrical material 12 rotates once.

[0022] The cylindrical material 12 may be machined with a single pitch, or it may be machined multiple times with different pitches. The following explanation will use the case where the cylindrical material 12 is machined twice with different pitches as an example. Specifically, the first step is a roughing step in which rough machining is performed on the outer surface of the cylindrical material 12, and the second step is a finishing step in which finishing is performed on the outer surface of the cylindrical material 12. In the first step, machining is performed with a first pitch, and in the second step, machining is performed with a second pitch different from the first pitch. Figure 2 shows an example where the second pitch is larger than the first pitch. The same cutting device 10A may be used for the first and second steps, or different cutting devices 10A may be used. In machining with the cutting device 10A, streak-like marks (hereinafter referred to as "tool marks 70") may be made on the outer surface of the cylindrical material 12 due to the cutting of the cutting tool 56.

[0023] Figure 2 shows an example of tool marks 70 generated in the first and second processes of machining. The tool mark from the first process is denoted as the first tool mark 70A, and the tool mark from the second process is denoted as the second tool mark 70B. In Figure 2, to facilitate understanding of the tool marks 70, a localized portion of the outer surface of the cylindrical material 12 is shown in magnified view. Furthermore, since the tool marks 70 are formed in a spiral shape on the outer surface of the cylindrical material 12, strictly speaking, they are inclined with respect to the Z-axis direction when viewed from the Y-axis direction, but in Figure 2, the tool marks 70 are shown as schematic lines parallel to the Z-axis direction.

[0024] The tool marks 70 tend to become thicker (in other words, darker in color) as the degree of damage or deterioration of the cutting tool 56 (hereinafter referred to as "degree of deterioration") increases. This is because the degree of cutting defects changes according to the degree of deterioration of the cutting tool 56, and the higher the degree of deterioration of the cutting tool 56, the greater the difference in cutting allowance between the well-cut and poorly-cut areas. Specifically, when the degree of deterioration of the cutting tool 56 is low, the tool marks 70 do not appear or are so thin that they are not visible; when the degree of deterioration of the cutting tool 56 is moderate, tool marks of moderate thickness appear; and when the degree of deterioration of the cutting tool 56 is high, thick tool marks 70 appear.

[0025] Furthermore, the tool marks 70 appear at a frequency corresponding to the pitch of the cutting tool 56. Specifically, when the pitch of the cutting tool 56 is normal (i.e., when the cutting tool 56 moves at the pitch preset in the cutting device 10A), the tool marks 70 appear at a constant frequency corresponding to the normal pitch. Also, if the pitch of the cutting tool 56 differs between the first and second processes, the periods at which the first tool marks 70A and the second tool marks 70B appear will differ. On the other hand, for example, if the pitch of the cutting tool 56 is abnormal due to a malfunction in the cutting section 52 (i.e., when the cutting tool 56 moves at a pitch different from the pitch preset in the cutting device 10A, or when the pitch fluctuates), the tool marks 70 may appear at a position shifted from the normal pitch, or the tool marks 70 may appear at an irregular frequency, corresponding to the abnormal pitch.

[0026] Furthermore, the period at which tool marks 70 appear may vary depending on the quality of the cylindrical cross-sectional shape of the cylindrical material 12. Specifically, if the cylindrical cross-sectional shape of the cylindrical material 12 is good (i.e., if the roundness is high), the amount of cutting (i.e., cutting depth) of the cutting tool 56 is stable, and if there are no defects in the cutting area 52, the cutting tool 56 moves at a normal pitch, so the tool marks 70 appear at a constant period. On the other hand, if the cylindrical cross-sectional shape of the cylindrical material 12 is poor (i.e., if the roundness is low), the amount of cutting of the cutting tool 56 varies according to the distortion of the cylindrical cross-sectional shape of the cylindrical material 12, which causes the load acting on the cutting tool 56 to fluctuate, and the pitch of the cutting tool 56 to fluctuate, causing the tool marks 70 to appear at an irregular period.

[0027] Similarly, if there is no axial runout or eccentricity in the cylindrical material 12 rotated by the rotating part 50, the amount of cutting (i.e., cutting depth) of the cutting tool 56 will be stable, and if there are no defects in the cutting part 52, the cutting tool 56 will move at a normal pitch, and the tool marks 70 will appear at a constant period. On the other hand, if there is axial runout or eccentricity in the cylindrical material 12 rotated by the rotating part 50, the amount of cutting of the cutting tool 56 will fluctuate according to the axial runout or eccentricity, causing the load acting on the cutting tool 56 to fluctuate, and the pitch of the cutting tool 56 to fluctuate, resulting in the tool marks 70 appearing at an irregular period.

[0028] In the example shown in Figure 2, tool marks 70 when the degree of deterioration of the cutting tool 56 is low and tool marks 70 when the degree of deterioration of the cutting tool 56 is moderate are not defective tool marks, but tool marks 70 when the degree of deterioration of the cutting tool 56 is high are defective tool marks. For example, if tool marks 70 remain on the outer surface of a billet as a cylindrical material 12, and these tool marks 70 are defective, during pipe manufacturing, it may cause problems in terms of quality assurance and yield, such as the occurrence of wrinkles in the steel pipe after manufacturing. Also, in the finished product after pipe manufacturing, it will deviate from the specified surface roughness, resulting in a large number of defects, which is also a problem. Therefore, it is necessary to judge the quality of the tool marks 70 after machining. Furthermore, in order to prevent the occurrence of defective tool marks 70, it is necessary to identify the source of the defective tool marks 70.

[0029] Figure 3 shows an example of a cylindrical material manufacturing apparatus 10, including a surface texture inspection device 10B and a cylindrical material 12. The cylindrical material manufacturing apparatus 10 includes a surface texture inspection device 10B as a device for determining the quality of tool marks 70 and identifying the source of defective tool marks 70. The surface texture inspection device 10B inspects the surface texture of the outer surface of the cylindrical material 12 cut by the cutting device 10A, and based on the inspection results, determines the quality of the tool marks 70 and identifies the source of defective tool marks 70. Inspection by the surface texture inspection device 10B is performed, for example, after the completion of the second process.

[0030] The surface texture inspection apparatus 10B includes a rotating support device 14, an illumination and imaging device 16, and a processing device 20. The illumination and imaging device 16 includes an illumination device 22 and a plurality of imaging devices 24.

[0031] Figures 4 and 5 show an example of a rotating support device 14, an illumination imaging device 16, and a cylindrical material 12. Figure 4 is a side view seen from the X-axis direction, and Figure 5 is a front view seen from the Y-axis direction. The rotating support device 14 is a mechanism that rotates the cylindrical material 12 in the direction of its axis. Specifically, the rotating support device 14 is a mechanism that rotates the cylindrical material 12 around a central axis 12A that is parallel to the direction perpendicular to the optical axis 24A, so that the outer surface of the cylindrical material 12 to be inspected is shown with respect to the optical axis 24A of each imaging device 24, which will be described later.

[0032] The rotating support device 14 comprises a drive unit 26 and a pair of roller units 28. The drive unit 26 is a drive source having a reduction gear and a motor, etc. The pair of roller units 28 are arranged side by side in the Y-axis direction. The pair of roller units 28 are configured symmetrically in the Y-axis direction. Each roller unit 28 has a plurality of rollers 30 and a shaft member 32. The shaft member 32 is formed in a rod shape and extends in the X-axis direction. The plurality of rollers 30 are arranged coaxially in the X-axis direction and are fixed to the shaft member 32. The output shaft of the drive unit 26 is connected to the shaft member 32 provided on one of the roller units 28.

[0033] A cylindrical material 12 is rotatably mounted on a pair of roller sections 28. The cylindrical material 12 is positioned on the pair of roller sections 28 such that its central axis 12A is parallel to the X-axis direction. In the first embodiment, the rotation support device 14 is configured to support the cylindrical material 12 from below in the vertical direction by the pair of roller sections 28, so that the outer diameter of the cylindrical material 12 can be arbitrarily changed within the range in which the outer surface of the cylindrical material 12 falls within the depth of field of the imaging device 24, which will be described later. As an example, Figures 4 and 5 show a configuration in which a cylindrical material 12 with a small outer diameter and a cylindrical material 12 with a large outer diameter are mounted on a pair of roller sections 28. The cylindrical material 12 with a small outer diameter is shown by a solid line, and the cylindrical material 12 with a large outer diameter is shown by a dashed line.

[0034] With the cylindrical material 12 rotatably mounted on a pair of roller sections 28, when the drive unit 26 is activated, the rotational force of the drive unit 26 is transmitted to one of the roller sections 28, causing that roller section 28 to rotate while supporting the cylindrical material 12 from vertically below. As one roller section 28 rotates, the frictional force generated between the roller section 28 and the cylindrical material 12 causes the cylindrical material 12 to rotate around its central axis 12A. The other roller section 28 of the pair of roller sections 28 rotates as a driven roller due to the frictional force generated between it and the cylindrical material 12, supporting the cylindrical material 12 from vertically below. The rotational speed of the drive unit 26 is adjustable, and by adjusting the rotational speed of the drive unit 26, the cylindrical material 12 can be rotated at a desired speed.

[0035] The illumination and imaging device 16 is positioned approximately vertically above the cylindrical material 12. In this specification, "approximately vertically above" means not only perfectly vertically above, but also vertically above that includes errors that are generally acceptable in the art to which the present invention belongs and that do not contradict the spirit of the present invention. Of the illumination and imaging device 16, the illumination device 22 irradiates light onto the cylindrical material 12, which is being rotated by the rotating support device 14, from approximately vertically above. Of the illumination and imaging device 16, each imaging device 24 images multiple circumferential positions on the outer surface of the cylindrical material 12, which is irradiated with light from the illumination device 22 and rotated by the rotating support device 14. Each imaging device 24 is an example of the imaging unit of the present invention.

[0036] The multiple imaging devices 24 are, for example, identical in configuration. The multiple imaging devices 24 are arranged side by side in the X-axis direction. They are also arranged at the same position (i.e., the same height) in the Z-axis direction. The fields of view (i.e., imaging range) of the multiple imaging devices 24 are predetermined to include the entire length of the outer surface of the cylindrical material 12 without any gaps between the fields of view of adjacent imaging devices 24, even if the outer diameter of the cylindrical material 12 changes. The focal length of each imaging device 24 is set so that the outer surface of the cylindrical material 12 is within the depth of field, even if the outer diameter of the cylindrical material 12 changes.

[0037] The illumination and imaging device 16 is positioned approximately vertically above the central axis 12A of the cylindrical material 12. The specific configuration of the illumination and imaging device 16 will be described later, but among the illumination and imaging device 16, the illumination device 22 is positioned such that its optical axis 22A intersects with the central axis 12A of the cylindrical material 12 and is parallel to the Z-axis direction. Similarly, among the illumination and imaging device 16, each imaging device 24 is positioned such that its optical axis 24A intersects with the central axis 12A of the cylindrical material 12 and is parallel to the Z-axis direction. Each imaging device 24 is positioned to image the outer surface of the cylindrical material 12 along the optical axis 22A of the illumination device 22 when viewed from the X-axis direction. As an example, each imaging device 24 is positioned such that its optical axis 24A coincides with the optical axis 22A of the illumination device 22 when viewed from the X-axis direction. In other words, the illumination device 22 is positioned to illuminate each imaging device 24 coaxially with its optical axis 24A when viewed from the X-axis direction.

[0038] Figure 6 shows an example of an illumination and imaging device 16. The illumination device 22 is, for example, a linear illumination device, arranged so that its longitudinal direction is parallel to the X-axis direction and its transverse direction is parallel to the Y-axis direction. The illumination device 22 may be, for example, an LED light, an incandescent light bulb light, or a fluorescent light. The illumination device 22 is configured to irradiate light uniformly using a diffusion film. The illumination range of the illumination device 22 is set to be wider than the field of view of each imaging device 24 in order to suppress uneven illumination. The light emitted from the illumination device 22 may be white light or light of any color. The illumination device 22 is a perforated illumination device having a plurality of through holes 34. The plurality of through holes 34 are aligned in the X-axis direction, and each through hole 34 penetrates in the Z-axis direction. An imaging device 24 is arranged inside each through hole 34.

[0039] Multiple imaging devices 24 are arranged in the X-axis direction by being positioned inside each through-hole 34. Each imaging device 24 is a camera capable of capturing the outer surface of the cylindrical material 12 as a monochrome or color image. Each imaging device 24 is a two-dimensional camera (i.e., an area camera) in which image sensors such as CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) are arranged in two dimensions. The horizontal axis of the field of view of each imaging device 24 is set parallel to the X-axis direction, and the vertical axis of the field of view of each imaging device 24 is set parallel to the Y-axis direction. In the first embodiment, there are three imaging devices 24, but any number may be used.

[0040] Figure 7 shows an example of the functional configuration of the processing unit 20. The processing unit 20 has an imaging control unit 40, an inspection image generation unit 42, a two-dimensional Fourier transform unit 44, and an inspection unit 46 as its functional configuration. The processing unit 20 is a device that performs various controls related to the surface texture inspection device 10B and various calculations related to the inspection of the cylindrical material 12, and is composed of a computer with a hardware configuration described later.

[0041] The imaging control unit 40 controls the rotating support device 14, the illumination device 22, and the multiple imaging devices 24 so that the entire circumference of the outer surface of the cylindrical material 12 is imaged. The imaging control unit 40 obtains the rotation angle of the cylindrical material 12 from a rotary encoder or the like provided on the rotating support device 14, and synchronizes the timing of imaging by each imaging device 24 with the rotation angle of the cylindrical material 12.

[0042] Figure 8 shows an example in which multiple imaging devices 24 generate multiple captured images 60. The imaging control unit 40 instructs each imaging device 24 to capture images at multiple circumferential positions on the outer surface of the cylindrical material 12, in accordance with the rotation angle of the cylindrical material 12. At this time, the imaging control unit 40 instructs each imaging device 24 to capture images of the entire circumference of the outer surface of the cylindrical material 12 in multiple steps. As a result, multiple captured images 60 covering the entire circumference of the outer surface of the cylindrical material 12 in the circumferential direction, and the entire circumference of the outer surface of the cylindrical material 12 in the axial direction, are generated by the multiple imaging devices 24. The imaging control unit 40 then acquires the multiple captured images 60 generated by the multiple imaging devices 24 from each imaging device 24.

[0043] Figure 9 shows an example of how an inspection image 66 is generated from multiple captured images 60. The inspection image generation unit 42 extracts a central image region 62 that forms part of the captured image 60 from each captured image 60 obtained by imaging the cylindrical material 12 with multiple imaging devices 24. The central image region 62 is located in the center of the captured image 60 in the vertical direction (i.e., the direction corresponding to the rotation direction of the cylindrical material 12) and is an image region that extends from one end to the other in the horizontal direction (i.e., the direction corresponding to the axial direction of the cylindrical material 12) of the captured image 60. The central image region 62 is located on the optical axis of the imaging device 24 within the imaging range of the imaging device 24 and is a region on the captured image 60 that corresponds to the imaging region that extends from one end to the other in the horizontal direction (i.e., the direction corresponding to the axial direction of the cylindrical material 12) of the imaging range of the imaging device 24. The imaging control unit 40 causes the imaging device 24 to image the outer surface of the rotating cylindrical material 12 at a predetermined pitch so that a central image region 62 covering the entire circumference of the cylindrical material 12 can be obtained. The inspection image generation unit 42 then generates a concatenated image 64 by concatenating the extracted central image regions 62 in a direction corresponding to the vertical direction of the image 60 for each image 60 generated by each imaging device 24 (i.e., for each image group A to C corresponding to each imaging device 24), and further concatenates the generated concatenated images 64 in a direction corresponding to the horizontal direction of the image 60 to generate an inspection image 66. In this way, the inspection image 66 is generated based on multiple image 60s. Here, we have shown an example of generating an inspection image 66 by concatenating captured images 60, but subsequent processing may be performed using only the captured images 60. Furthermore, the real-space length per pixel (imaging resolution) of the captured images 60 may be defined. Defining the imaging resolution makes it easier to calculate the period of tool marks on the captured images 60 in terms of real-space length.

[0044] Figure 10 shows an example of an inspection image 66 and power spectrum obtained after the completion of the first process. In Figure 10, as in Figure 2, tool marks 70 are shown as schematic lines parallel to the vertical direction of the inspection image 66. As an example, Figure 10 shows an inspection image 66 obtained when the degree of deterioration of the cutting tool 56 is low, and an inspection image 66 obtained when the degree of deterioration of the cutting tool 56 is high. The power spectrum corresponding to each inspection image 66 is a graph of the intensity for each spatial frequency obtained by performing a two-dimensional Fourier transform on each inspection image 66. The horizontal axis represents spatial frequency [1 / mm], and the vertical axis represents intensity. The intensity corresponds to the contrast of the striped pattern of the tool marks 70 shown in the inspection image 66 (i.e., the darkness of the color of the tool marks 70). That is, the stronger the contrast of the striped pattern of the tool marks 70 shown in the inspection image 66 (i.e., the darker the color of the tool marks 70), the higher the intensity.

[0045] The two-dimensional Fourier transform unit 44, when the inspection image 66 is generated by the inspection image generation unit 42, performs a two-dimensional Fourier transform on the inspection image 66 to calculate the intensity for each spatial frequency.

[0046] As described above, the stronger the contrast of the striped pattern of the tool marks 70 in the inspection image 66, the higher the intensity. Therefore, it is considered possible to determine the quality of the tool marks 70 based on their intensity. Specifically, a threshold corresponding to the acceptable limit of the tool marks 70 is set for the intensity for each spatial frequency calculated by the two-dimensional Fourier transform unit 44. If the peak is below the threshold, the tool marks 70 can be judged to be good, and if the peak exceeds the threshold, the tool marks 70 can be judged to be poor.

[0047] Furthermore, the intensity for each spatial frequency peaks (i.e., reaches its maximum value) at the spatial frequency corresponding to the period of the tool mark 70. In other words, in the power spectrum, the peak of intensity for each spatial frequency appears at the spatial frequency corresponding to the period of the tool mark 70. Also, the period of the tool mark 70 corresponds to the pitch of the cutting tool 56. Therefore, when the pitch of the cutting tool 56 is normal (i.e., the cylindrical material 12 is normal and cutting is performed at the pitch preset in the cutting device 10A), a peak appears at the spatial frequency corresponding to the normal pitch. When the pitch of the cutting tool 56 is normal, the spatial frequency corresponding to the normal pitch can be calculated, and a peak appears at the calculated spatial frequency corresponding to the normal pitch. Figure 10 shows, as an example, the power spectrum corresponding to the inspection image 66 obtained when the pitch of the cutting tool 56 is normal. Since the period (pitch) of tool marks in real space and the spatial frequency are inversely related, the spatial frequency corresponding to a normal pitch can be calculated. In other words, when cutting is performed normally at a predetermined pitch, the reciprocal of the pitch (mm) is the spatial frequency corresponding to the normal pitch.

[0048] On the other hand, for example, if the pitch of the cutting tool 56 is abnormal due to a malfunction in the cutting section 52 (i.e., if cutting is performed at a pitch different from the pitch preset in the cutting device 10A, or if cutting is performed with a fluctuating pitch), a peak will appear at the spatial frequency corresponding to the abnormal pitch. Also, if the cylindrical cross-sectional shape of the cylindrical material 12 is poor (i.e., if the roundness is low), or if axial runout or eccentricity occurs in the cylindrical material 12 that rotates due to the rotating section 50, the pitch of the cutting tool 56 will fluctuate as described above, and a peak will appear at the spatial frequency corresponding to the abnormal pitch. When the pitch of the cutting tool 56 is abnormal, a peak will appear at a spatial frequency different from the calculated spatial frequency corresponding to the normal pitch, corresponding to the abnormal pitch.

[0049] Therefore, by calculating the spatial frequency corresponding to a normal pitch, if the peak spatial frequency is the calculated spatial frequency, it can be determined that the cylindrical material 12 is normal and that cutting is being performed at the pitch preset in the cutting device 10A. Conversely, if the peak spatial frequency is not the calculated spatial frequency (i.e., it is a different spatial frequency from the calculated spatial frequency), it can be determined that cutting is not being performed at the pitch preset in the cutting device 10A.

[0050] The inspection unit 46 inspects the surface properties of the outer surface of the cylindrical material 12 based on the intensity peaks for each spatial frequency calculated by the two-dimensional Fourier transform unit 44. Specifically, the inspection unit 46 analyzes the intensity for each spatial frequency and identifies the intensity peaks for each spatial frequency. Then, the inspection unit 46 compares the peaks with a threshold value set in advance corresponding to the permissible limit value of the tool marks 70 and determines whether the tool marks 70 are good or bad. If the peak is below the threshold, the inspection unit 46 determines that the tool marks 70 are good (i.e., the cylindrical material 12 is good), and if the peak exceeds the threshold, it determines that the tool marks 70 are bad (i.e., the cylindrical material 12 is bad).

[0051] Furthermore, the inspection unit 46 analyzes the cause of the defect in the cylindrical material 12 in which the tool marks 70 were determined to be defective. Specifically, the inspection unit 46 analyzes the spatial frequency and identifies the spatial frequency of the peak identified above. Subsequently, the inspection unit 46 calculates the spatial frequency corresponding to a normal pitch and determines whether the spatial frequency of the peak is the calculated spatial frequency.

[0052] The inspection unit 46 identifies the process causing the defect if the spatial frequency of the peak matches the calculated spatial frequency. Here, we will explain under the assumption that the cylindrical material 12 is normal and that the cutting device 10A is cutting at the pitch set in advance. Figure 11 shows an example of an inspection image and power spectrum obtained after the completion of the second process. Figure 11 shows two examples of inspection images 66 obtained after the completion of the second process: inspection image 66a obtained when the degree of deterioration of the cutting tool 56 is low in both the first and second processes, and inspection image 66b obtained when the degree of deterioration of the cutting tool in the first process is low, but the degree of deterioration of the cutting tool 56 in the second process is high. That is, in inspection image 66a, where the degree of deterioration is low, no tool marks 70 appear to be particularly dark or thick, but in inspection image 66b, which includes a cutting tool with a high degree of deterioration, some tool marks 70 appear to be dark or thick. In the example shown in Figure 11, thin tool marks 70 can be seen in inspection image 66a. In inspection image 66a, it is thought that a mixture of first tool marks 70A and second tool marks 70B, which indicate a low degree of deterioration of the cutting tool 56, are present. Furthermore, since the power spectrum corresponding to inspection image 66a is obtained by frequency-converting inspection image 66a, a peak appears at the spatial frequency corresponding to the period of the tool marks 70. That is, because the periods of the tool marks 70 differ between the first process, which performs cutting with a small pitch, and the second process, which performs cutting with a large pitch, a peak 80A appears in the power spectrum at the spatial frequency corresponding to the period of tool mark 70A, and a peak 80B appears at the spatial frequency corresponding to the period of tool mark 70B. Therefore, from the relationship between the peak 80 of the power spectrum and the tool mark 70 on the inspection image 66a, it is possible to identify the first tool mark 70A, which corresponds to the first process (corresponding to the peak 80A of the power spectrum), and the second tool mark 70B, which corresponds to the second process (corresponding to the peak 80B of the power spectrum). On the other hand, inspection image 66b shows both thin tool marks 70A and thick or dark tool marks 70B. Also, similar to inspection image 66a, the power spectrum corresponding to inspection image 66b shows a peak at the spatial frequency corresponding to the period of the tool marks 70. Therefore, from the relationship between the peak 80 of the power spectrum and the tool marks 70 on inspection image 66b, we can identify the first tool mark 70A, which corresponds to the first process (corresponding to the peak 80A of the power spectrum), and the second tool mark 70B, which corresponds to the second process (corresponding to the peak 80B of the power spectrum). In this case, tool marks 70 made by a highly degraded cutting tool will be thick or dark as described above, so the power spectrum will have a peak value that exceeds the threshold. Therefore, it can be seen that the tool mark corresponding to the peak that exceeds the threshold is the tool mark 70B corresponding to the second process. As described above, the inspection unit 46 checks whether the spatial frequency of the peak appearing in the power spectrum corresponding to the inspection image 66 matches the spatial frequency corresponding to the period of the tool marks 70, which has been calculated in advance, for the cylindrical material 12 that has been determined to be defective. In other words, the reciprocal of the spatial frequency value in which a peak exceeding the threshold appears can be determined to be the pitch of the tool marks 70 made by a cutting tool with a high degree of deterioration.

[0053] On the other hand, the above explanation has been based on the premise that the cylindrical material 12 is normal and that cutting is being performed at the pitch set in the cutting device 10A. However, if this premise does not hold, the inspection unit 46 will identify the element causing the defect based on the fact that the spatial frequency of the peak does not correspond to the spatial frequency of the period of the tool mark 70 that was calculated in advance. Specifically, if the spatial frequency of the peak is not the calculated spatial frequency, it means that there is an abnormality in the pitch of the cutting tool 56. Examples of abnormalities in the pitch of the cutting tool 56 include defects in the cutting part 52, axial runout or eccentricity of the cylindrical material 12 that is rotated by the rotating part 50, and defects in the cross-sectional shape of the cylindrical material 12. Therefore, the inspection unit 46 will determine that at least one of the cutting part 52, the rotating part 50, and the cylindrical material 12 is defective. In this case, the inspection unit 46 may, for example, identify the defective part among the cutting part 52, the rotating part 50, and the cylindrical material 12 based on the peak and the spatial frequency of the peak.

[0054] The inspection results from the inspection unit 46 are transmitted to, for example, a display or other information processing device, and countermeasures corresponding to the inspection results (for example, cleaning tool marks 70, maintenance of each part, etc.) are implemented.

[0055] Figure 11 shows an example of the hardware configuration of the processing unit 20. The processing unit 20 is composed of a computer. The processing unit 20 has a CPU (Central Processing Unit) 90, memory 92, storage device 94, input device 96, output device 98, storage medium reader 100, and communication I / F (Interface) 102. Each component is connected to the others so as to be able to communicate with each other via a bus 104.

[0056] The storage device 94 stores a program for performing surface condition inspection. The CPU 90 is a central processing unit that executes various programs and controls each component. Specifically, the CPU 90 reads the program from the storage device 94 and executes the program using memory 92 as a workspace. The CPU 90 controls each component and performs various calculations according to the program stored in the storage device 94.

[0057] Memory 92 is composed of RAM (Random Access Memory) and temporarily stores programs and data as a working area. Storage device 94 is composed of ROM (Read Only Memory), HDD (Hard Disk Drive), or SSD (Solid State Drive), etc., and stores various programs and data, including the operating system.

[0058] The input device 96 is a device for performing various types of input, such as a keyboard or mouse. The output device 98 is a device for outputting various types of information, such as a display or printer. A touch panel display may be used as the output device 98 and function as the input device 96.

[0059] The storage medium reader 100 reads data stored on various storage media such as CD (Compact Disc)-ROM, DVD (Digital Versatile Disc)-ROM, Blu-ray disc, or USB (Universal Serial Bus) memory, and writes data to the storage media. The communication I / F 102 is an interface for communicating with other devices. For example, the communication I / F 102 uses an interface that conforms to standards such as Ethernet (registered trademark), FDDI, or Wi-Fi (registered trademark).

[0060] Figure 13 shows an example of the flow of a method for manufacturing a cylindrical material according to the first embodiment. First, in step S10, the cylindrical material 12 is set in the cutting device 10A, and the cutting device 10A cuts the outer surface of the cylindrical material 12. Step S10 includes a rotation step in which the cylindrical material 12 is rotated relative to the cutting tool 56 around a central axis which is an axis perpendicular to the circular cross-section of the cylindrical material 12 using a rotating part 50, and a movement step in which the cutting tool 56 is brought into contact with the outer surface of the cylindrical material 12, and the cylindrical material 12 rotated by the rotating part 50 is moved relative to the cutting tool 56 in the axial direction of the cylindrical material 12, thereby cutting the outer surface of the cylindrical material 12 in a spiral shape. Step S10 is an example of a cutting step of the present invention.

[0061] Next, in step S12, the NC control device of the cutting device 10A or the operator of the cutting device 10A determines whether the cutting process on the cylindrical material 12 has been completed. If the second cutting process has not been performed, it is determined that the cutting process on the cylindrical material 12 has not been completed, and the manufacturing method of the cylindrical material proceeds to step S10 (i.e., the second cutting process). On the other hand, if the second cutting process has been performed, it is determined that the cutting process on the cylindrical material 12 has been completed, and the manufacturing method of the cylindrical material proceeds to step S14. From step S14 onward, the cylindrical material 12 is brought into the surface texture inspection device 10B and inspected by the surface texture inspection device 10B.

[0062] In step S14, multiple imaging devices 24 image the outer surface of the cylindrical material 12 cut by the cutting device 10A, and generate multiple imaged images 60 covering the entire circumference, including the entire length of the outer surface of the cylindrical material 12. Step S14 is an example of the imaging steps of the present invention.

[0063] Next, in step S16, the inspection image generation unit 42 extracts a central image region 62 that forms part of the captured image 60 from each captured image 60, connects the extracted central image regions 62 in a direction corresponding to the vertical direction of the captured image 60 to generate a concatenated image 64, and then connects the generated concatenated images 64 in a direction corresponding to the horizontal direction of the captured image 60 to generate an inspection image 66.

[0064] Next, in step S18, the two-dimensional Fourier transform unit 44 performs a two-dimensional Fourier transform on the inspection image 66 to calculate the intensity for each spatial frequency. Step S18 is an example of the two-dimensional Fourier transform step of the present invention.

[0065] Next, in step S20, the inspection unit 46 analyzes the intensity for each spatial frequency of the results calculated in step S18 and identifies the peak intensity for each spatial frequency.

[0066] Next, in step S22, the inspection unit 46 compares the peak with a preset threshold corresponding to the permissible limit value of the tool marks 70 from the first and second processes, and determines whether the tool marks 70 are good or bad. Here, if the peak is below the threshold, the inspection unit 46 determines that the tool marks 70 are good (i.e., the cylindrical material 12 is good), and the manufacturing method of the cylindrical material is completed. After the manufacturing method of the cylindrical material is completed, the cylindrical material 12 is transported to the next process after inspection. On the other hand, if the peak exceeds the threshold, the inspection unit 46 determines that the tool marks 70 are bad (i.e., the cylindrical material 12 is bad), and proceeds to step S24.

[0067] In step S24, the inspection unit 46 analyzes the spatial frequencies of the results calculated in step S18 and identifies the spatial frequencies of the peaks identified in step S20.

[0068] Next, in step S26, the inspection unit 46 calculates the spatial frequencies corresponding to the normal pitches of the first and second processes and determines whether the spatial frequencies identified in step S24 correspond to the spatial frequencies corresponding to the normal pitches of the first and second processes that were calculated in advance. That is, it checks whether the spatial frequencies identified in step S24 match the spatial frequencies corresponding to the periods of the tool marks 70 of the first and second processes. Here, if the spatial frequency identified in step S24 matches the spatial frequency calculated in advance, the inspection unit 46 proceeds to step S28. On the other hand, if the spatial frequency identified in step S24 does not match the spatial frequency calculated in advance, the inspection unit 46 proceeds to step S30.

[0069] In step S28, the inspection unit 46 identifies the process that caused the defect. Specifically, if the spatial frequency identified in step S24 corresponds to the spatial frequencies corresponding to the normal pitches of the first and second processes calculated in advance, the inspection unit 46 determines that the cause of the defect (i.e., the reason the peak exceeded the threshold) lies in the second process. Also, if the spatial frequency identified in step S24 corresponds to the spatial frequency corresponding to the normal pitch of the second process calculated in advance, the pitch of the cutting tool 56 is normal, and therefore, based on the fact that the peak exceeded the threshold, the inspection unit 46 determines that an abnormality has occurred in the cutting conditions in the second process (for example, conditions such as damage or deterioration of the cutting tool 56). After step S28, the manufacturing method of the cylindrical material is completed.

[0070] In step S30, the inspection unit 46 identifies the element causing the defect. Specifically, if the spatial frequency identified in step S24 does not match the calculated spatial frequency, it indicates an abnormality in the pitch of the cutting tool 56. Examples of abnormalities in the pitch of the cutting tool 56 include defects in the cutting unit 52, axial runout or eccentricity of the cylindrical material 12 rotated by the rotating unit 50, and defects in the cross-sectional shape of the cylindrical material 12. Therefore, the inspection unit 46 determines that at least one of the cutting unit 52, the rotating unit 50, and the cylindrical material 12 is defective. After step S28, the manufacturing method of the cylindrical material is completed. Steps S14 to S30 are examples of surface property inspection steps of the present invention. Also, steps S20 to S30 are examples of inspection steps of the present invention.

[0071] As described above, in the first embodiment, multiple imaging devices 24 image the outer surface of the cylindrical material 12 cut by the cutting device 10A and generate multiple imaged images 60 covering the entire circumference including the entire length of the outer surface of the cylindrical material 12. A two-dimensional Fourier transform unit 44 performs a two-dimensional Fourier transform on the inspection image 66 based on the imaged images 60 to calculate the intensity for each spatial frequency. An inspection unit 46 inspects the surface properties of the outer surface of the cylindrical material 12 based on the peak intensity for each spatial frequency. If the peak is below a threshold, the inspection unit 46 determines that the tool marks 70 on the outer surface of the cylindrical material 12 are good (i.e., the cylindrical material 12 is good), and if the peak exceeds the threshold, it determines that the tool marks 70 are poor (i.e., the cylindrical material 12 is poor). In this way, according to the first embodiment, it is possible to determine the quality of the tool marks 70 (i.e., the quality of the cylindrical material 12).

[0072] Furthermore, the inspection unit 46 determines whether the spatial frequency of the peak deemed defective matches the spatial frequency corresponding to the normal pitch of the first and second processes. If the result of the determination is that it matches the spatial frequency corresponding to the pitch of the second process, the inspection unit 46 determines that there is an abnormality in the cutting conditions in the second process (for example, conditions such as damage or deterioration of the cutting tool 56). On the other hand, if the spatial frequency of the peak is not the spatial frequency corresponding to the normal pitch of the first and second processes calculated in advance, the inspection unit 46 determines that at least one of the cutting part 52, the rotating part 50, and the cylindrical material 12 is defective. In this way, according to the first embodiment, the source of defective tool marks 70 can be identified.

[0073] [Second Embodiment] Next, a second embodiment of the present invention will be described.

[0074] In the second embodiment, the operation of the inspection unit 46 differs from that of the first embodiment. The differences in the operation of the inspection unit 46 in the second embodiment will be explained below.

[0075] Figure 14 shows an example of the flow of the manufacturing method for a cylindrical material according to the second embodiment. Steps S10 to S20 are the same as in the first embodiment, so their explanation is omitted.

[0076] In step S32, the inspection unit 46 analyzes the spatial frequency of the result calculated in step S18 and identifies the spatial frequency of the peak identified in step S20.

[0077] Next, in step S34, the inspection unit 46 predicts the spatial frequencies corresponding to the normal pitches of the first and second processes and determines whether the spatial frequencies identified in step S32 are the spatial frequencies corresponding to the normal pitches of the first and second processes that were calculated in advance. Here, if the spatial frequencies identified in step S32 are the spatial frequencies that were calculated in advance, the inspection unit 46 proceeds to step S36. On the other hand, if the spatial frequencies identified in step S32 are not the spatial frequencies that were calculated in advance, the inspection unit 46 proceeds to step S38.

[0078] In step S36, the inspection unit 46 compares the peak with a preset threshold corresponding to the permissible limit of the tool marks 70, and determines whether the tool marks 70 are good or bad. Here, if the peak is below the threshold, the inspection unit 46 determines that the tool marks 70 are good (i.e., the cylindrical material 12 is good), and the manufacturing method of the cylindrical material is completed. After the manufacturing method of the cylindrical material is completed, the cylindrical material 12 is transported to the next process after inspection. On the other hand, if the peak exceeds the threshold, the inspection unit 46 determines that the tool marks 70 are bad (i.e., the cylindrical material 12 is bad), and proceeds to step S40.

[0079] In step S38, the inspection unit 46 identifies the element causing the defect. Specifically, if the spatial frequency of the peak identified in step S32 is not the predicted spatial frequency, it indicates an abnormality in the pitch of the cutting tool 56. Examples of abnormalities in the pitch of the cutting tool 56 include defects in the cutting unit 52, axial runout or eccentricity of the cylindrical material 12 rotated by the rotating unit 50, and defects in the cross-sectional shape of the cylindrical material 12. Therefore, the inspection unit 46 determines that at least one of the cutting unit 52, the rotating unit 50, and the cylindrical material 12 is defective. After step S38, the manufacturing method of the cylindrical material is completed.

[0080] In step S40, the inspection unit 46 identifies the process that caused the defect. Specifically, the inspection unit 46 determines whether the spatial frequency of the peak that was determined to have exceeded the threshold in step S36 matches the spatial frequency corresponding to the normal pitch of the first process or the second process. If the result of the determination is that it matches the spatial frequency predicted for the second process, the inspection unit 46 determines that the cause of the defect (i.e., the reason why the peak exceeded the threshold) lies in the second process. Alternatively, the inspection unit 46 can determine that the pitch of the cutting tool 56 is normal, and based on the fact that the peak exceeded the threshold, the inspection unit 46 determines that there is an abnormality in the cutting conditions in the second process (for example, conditions such as damage or deterioration of the cutting tool 56). After step S40, the manufacturing method of the cylindrical material is completed. Steps S14 to S20 and steps S32 to S40 are examples of surface property inspection steps of the present invention. Also, steps S20 and steps S32 to S40 are examples of inspection steps of the present invention.

[0081] As described above, in the second embodiment, if the spatial frequency of the peak is not the spatial frequency corresponding to the cutting pitch, the inspection unit 46 determines that at least one of the cutting unit 52, the rotating unit 50, and the cylindrical material 12 is defective. On the other hand, if the spatial frequency of the peak is the spatial frequency corresponding to the cutting pitch, and the peak exceeds a threshold, the inspection unit 46 determines which cutting pitch the spatial frequency of the peak exceeding the threshold corresponds to. If, as a result of the determination, the spatial frequency of the peak exceeding the threshold corresponds to the pitch of the second process, the inspection unit 46 determines that an abnormality has occurred in the cutting conditions in the second process (for example, conditions such as damage or deterioration of the cutting tool 56). In this way, according to the second embodiment, the source of defective tool marks 70 can be identified.

[0082] Furthermore, the inspection unit 46 determines that the tool marks 70 formed on the outer surface of the cylindrical material 12 are good (i.e., the cylindrical material 12 is good) if the peak is below the threshold, and determines that the tool marks 70 are poor (i.e., the cylindrical material 12 is poor) if the peak exceeds the threshold. In this way, according to the second embodiment, it is possible to determine whether the tool marks 70 are good or bad (i.e., whether the cylindrical material 12 is good or bad).

[0083] In the above embodiments, the cutting device 10A is an NC lathe, but a manual lathe may also be used.

[0084] Furthermore, the rotating part 50 of the cutting device 10A rotates the cylindrical material 12 about a central axis which is an axis perpendicular to the circular cross-section of the cylindrical material 12, but the cutting tool 56 may also be rotated relative to the cylindrical material 12 in the direction of the outer circumference of the cylindrical material 12. Also, the moving part 54 of the cutting device 10A moves the cutting tool 56 in the radial and axial directions of the cylindrical material 12, but the cylindrical material 12 may also be moved relative to the cutting tool 56 in the radial and axial directions of the cylindrical material 12.

[0085] Furthermore, in each of the above embodiments, the cylindrical material 12 is subjected to two cutting processes consisting of a first and a second step. However, the number of cutting processes performed on the cylindrical material 12 may be one or three or more.

[0086] Furthermore, in each of the above embodiments, the surface properties of the outer surface of the cylindrical material 12 are inspected after the second step (i.e., the final step), but the surface properties of the outer surface of the cylindrical material 12 may be inspected after each step.

[0087] Furthermore, in each of the above embodiments, the pitch of the cutting tool 56 is different in the first and second steps, but the pitch of the cutting tool 56 may be the same in the first and second steps. Moreover, the pitch of the cutting tool 56 may be the same in the first and third steps, the pitch of the cutting tool 56 may be the same in the second and fourth steps, and the pitch may be different in the second and fourth steps and in the first and third steps.

[0088] Furthermore, in each of the above embodiments, the illumination imaging device 16 may be configured as follows. Figure 14 shows a first modified example of the illumination imaging device 16. In the first modified example, the illumination imaging device 16 has a plurality of illumination devices 22. The plurality of illumination devices 22 are arranged in a line in the X-axis direction. An imaging device 24 is arranged between adjacent illumination devices 22. In the first modified example, as in the first embodiment (see Figure 4), each imaging device 24 is arranged to image the outer surface of the cylindrical material 12 along the optical axis 22A of the illumination device 22 when viewed from the X-axis direction. As an example, each imaging device 24 is arranged such that the optical axis 24A of the imaging device 24 coincides with the optical axis 22A of the illumination device 22 when viewed from the X-axis direction. Even with such a configuration, the same effects as in the above embodiments can be obtained.

[0089] Figure 15 shows a second modified example of the illumination imaging device 16. In the second modified example, the illumination imaging device 16 has a pair of illumination devices 22. Each illumination device 22 is a bar illumination extending in the X-axis direction. The pair of illumination devices 22 are arranged side by side in the Y-axis direction. Multiple imaging devices 24 are arranged between the pair of illumination devices 22. In the second modified example, as in the first embodiment (see Figure 4), each imaging device 24 is arranged to image the outer surface of the cylindrical material 12 along the optical axis 22A of the illumination device 22 when viewed from the X-axis direction. The same effects as in the above embodiment can be obtained with this configuration as well.

[0090] Furthermore, the illumination device 22 may be in a configuration other than those shown in Figures 6, 14, and 15. For example, the illumination device 22 may be a ring illumination device arranged coaxially with the imaging device 24, a line illumination device where the optical axis 24A of the imaging device 24 and the optical axis 22A of the illumination device 22 are parallel when viewed from the X-axis direction, or a coaxial incident illumination device that emits incident light coaxial with the imaging device 24.

[0091] Although one embodiment of the present invention has been described above, it goes without saying that the present invention is not limited to the above, and can be implemented in various ways without departing from the spirit of the invention. [Explanation of Symbols]

[0092] 10. Manufacturing apparatus for cylindrical materials 10A cutting equipment 10B Surface texture inspection device 12 cylindrical material 14. Rotating support device 16 Illumination and imaging device 20 Processing Units 22 Lighting devices 24 Imaging device 26 Drive unit 28 Roller section 30 Laura 32 Shaft member 34 through holes 40 Imaging control unit 42 Inspection Image Generation Unit 44-dimensional Fourier transform section 46. ​​Inspection Department 50 Rotating part 52 Cutting part 54 Mobile section 56 Cutting tools 60 captured images 62 Center image area 64 Linked Images 66 Test results 70 Tool marks 90 CPU 92 memory 94 Storage device 96 Input device 98 Output device 100 Storage medium reader 102 Communication I / F 104 Bus

Claims

1. A manufacturing apparatus for cylindrical or cylindrical materials, A cutting device for cutting the outer surface of the cylindrical material, A surface texture inspection device for inspecting the surface texture of the outer surface of the cylindrical material cut by the cutting device, It has, The cutting device is A rotating part that rotates the cylindrical material and the cutting tool relative to each other around a central axis which is an axis perpendicular to the circular cross-section of the cylindrical material, A cutting unit that brings the cutting tool into contact with the outer circumferential surface of the cylindrical material, and moves the cylindrical material and the cutting tool, which rotate relative to the cutting tool by the rotating unit, relative to each other in the axial direction of the cylindrical material, thereby cutting the outer circumferential surface of the cylindrical material in a spiral shape, It has, The surface properties inspection apparatus, An imaging unit that captures an image of the outer surface of the cylindrical material cut by the cutting device and generates an image of the captured image, A two-dimensional Fourier transform unit performs a two-dimensional Fourier transform on the captured image to calculate the intensity for each spatial frequency, An inspection unit that inspects the surface properties of the outer surface of the cylindrical material by determining that the cylindrical material is defective when the intensity peak for each spatial frequency exceeds a threshold, A manufacturing apparatus for cylindrical materials, comprising a cylindrical shape.

2. If the pitch is defined as the distance the cutting tool moves relative to the cylindrical material in the axial direction while the cylindrical material rotates once relative to the cutting tool, then when cutting the cylindrical material with a single pitch, or when cutting multiple times with different pitches, The aforementioned inspection unit is A cylindrical material manufacturing apparatus according to claim 1, wherein, with respect to the cylindrical material deemed to be defective, if the spatial frequency of the peak is the spatial frequency corresponding to the pitch, it is determined that an abnormality has occurred in the cutting conditions corresponding to the spatial frequency of the peak.

3. A manufacturing apparatus for cylindrical or cylindrical materials, A cutting device for cutting the outer surface of the cylindrical material, A surface texture inspection device for inspecting the surface texture of the outer surface of the cylindrical material cut by the cutting device, It has, The cutting device is A rotating part that rotates the cylindrical material and the cutting tool relative to each other around a central axis which is an axis perpendicular to the circular cross-section of the cylindrical material, A cutting unit that brings the cutting tool into contact with the outer circumferential surface of the cylindrical material, and moves the cylindrical material and the cutting tool, which rotate relative to the cutting tool by the rotating unit, relative to each other in the axial direction of the cylindrical material, thereby cutting the outer circumferential surface of the cylindrical material in a spiral shape, It has, The surface properties inspection apparatus, An imaging unit that captures an image of the outer surface of the cylindrical material cut by the cutting device and generates an image of the captured image, A two-dimensional Fourier transform unit performs a two-dimensional Fourier transform on the captured image to calculate the intensity for each spatial frequency, An inspection unit that inspects the surface properties of the outer surface of the cylindrical material based on the intensity peaks for each spatial frequency, It has, The aforementioned inspection unit is If the pitch is defined as the distance the cutting tool moves relative to the cylindrical material in the axial direction while the cylindrical material rotates once relative to the cutting tool, A cylindrical material manufacturing apparatus that determines that at least one of the cutting section, the rotating section, and the cylindrical material is defective if the spatial frequency of the peak is not the spatial frequency corresponding to the pitch.

4. A method for manufacturing a cylindrical or cylindrical material, A cutting device for cutting the outer surface of the cylindrical material, A surface texture inspection device for inspecting the surface texture of the outer surface of the cylindrical material cut by the cutting device, It has, The cutting device is A rotating part that rotates the cylindrical material and the cutting tool relative to each other around a central axis which is an axis perpendicular to the circular cross-section of the cylindrical material, A cutting unit that brings the cutting tool into contact with the outer circumferential surface of the cylindrical material, and moves the cylindrical material and the cutting tool, which rotate relative to the cutting tool by the rotating unit, relative to each other in the axial direction of the cylindrical material, thereby cutting the outer circumferential surface of the cylindrical material in a spiral shape, Using a manufacturing apparatus for cylindrical materials having the following characteristics: The imaging step involves imaging the outer surface of the cylindrical material cut by the cutting device and generating an image of the captured image, The process involves a two-dimensional Fourier transform step, in which the captured image is transformed to calculate the intensity for each spatial frequency, An inspection step in which the surface properties of the outer surface of the cylindrical material are inspected, by determining that the cylindrical material is defective when the intensity peak for each spatial frequency exceeds a threshold, A method for manufacturing a cylindrical material having the following characteristics.

5. If the pitch is defined as the distance the cutting tool moves relative to the cylindrical material in the axial direction while the cylindrical material rotates once relative to the cutting tool, then when cutting the cylindrical material with a single pitch, or when cutting multiple times with different pitches, The aforementioned inspection step is, A method for manufacturing a cylindrical material according to claim 4, wherein, with respect to the cylindrical material deemed to be defective, if the spatial frequency of the peak is the spatial frequency corresponding to the pitch, it is determined that an abnormality has occurred in the cutting conditions corresponding to the spatial frequency of the peak.

6. A method for manufacturing a cylindrical or cylindrical material, A cutting device for cutting the outer surface of the cylindrical material, A surface texture inspection device for inspecting the surface texture of the outer surface of the cylindrical material cut by the cutting device, It has, The cutting device is A rotating part that rotates the cylindrical material and the cutting tool relative to each other around a central axis which is an axis perpendicular to the circular cross-section of the cylindrical material, A cutting unit that brings the cutting tool into contact with the outer circumferential surface of the cylindrical material, and moves the cylindrical material and the cutting tool, which rotate relative to the cutting tool by the rotating unit, relative to each other in the axial direction of the cylindrical material, thereby cutting the outer circumferential surface of the cylindrical material in a spiral shape, Using a manufacturing apparatus for cylindrical materials having the following characteristics: The imaging step involves imaging the outer surface of the cylindrical material cut by the cutting device and generating an image of the captured image, The process involves a two-dimensional Fourier transform step, in which the captured image is transformed to calculate the intensity for each spatial frequency, An inspection step to inspect the surface properties of the outer surface of the cylindrical material based on the intensity peaks for each spatial frequency, It has, The aforementioned inspection step is, If the pitch is defined as the distance the cutting tool moves relative to the cylindrical material in the axial direction while the cylindrical material rotates once relative to the cutting tool, A method for manufacturing a cylindrical material, wherein if the spatial frequency of the peak is not the spatial frequency corresponding to the pitch, it is determined that at least one of the cutting part, the rotating part, and the cylindrical material is defective.

Images