Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/84—Systems specially adapted for particular applications
  • G01N21/88—Investigating the presence of flaws or contamination
  • G01N21/91—Investigating the presence of flaws or contamination using penetration of dyes, e.g. fluorescent ink

Definitions

• This disclosure relates to a surface inspection device and a surface inspection method, and more specifically, to a surface inspection device and a surface inspection method that use images to inspect the surface properties of an object.
• Magnetic particle inspection has been known in the past (see, for example, JP 2011-174893 A and JP 2021-025878 A).
• the object to be inspected is magnetized and magnetic particle liquid is applied to the magnetized object.
• magnetic flux leaks from open flaws, and the magnetic particles in the applied magnetic particle liquid adhere to the flaws.
• the object to which the magnetic particle liquid has been applied is irradiated with ultraviolet light, the attached magnetic particles are excited to emit light, and the emitting parts appear as a flaw pattern.
• Inspection of the surface properties of the object is performed, for example, by an inspector visually observing such flaw patterns in a darkroom.
• the flaws that can be confirmed by magnetic particle inspection come in a wide variety of shapes and patterns, and in some cases they closely resemble harmless pseudo patterns caused by things like accumulations of magnetic particle liquid.
• Inspectors need to distinguish between flaws and false patterns and determine whether they are harmful or harmless. However, this determination is extremely difficult and depends largely on the skill of the inspector. In addition, the fact that magnetic particle inspection is performed in a dark room over a long period of time makes the inspection process difficult. Furthermore, the inspection process is also difficult when the object has a complex shape. For this reason, when magnetic particle inspection is performed by inspectors, surface flaws may be overlooked and the object may be released, resulting in serious complaints. For this reason, there is a demand for the automation of magnetic particle inspection work.
• Magnetic particle inspection is performed by projecting uniform ultraviolet light onto the surface of an object coated with magnetic particle liquid, and then visually observing or photographing the pattern that is created by excited light emission from the magnetic particles that adhere to the flaws.
• Numerous methods have been proposed for imaging objects.
• methods proposed for imaging objects with complex shapes that have unevenness include imaging the object while it is rotating and connecting the captured images in the circumferential direction of the object, and acquiring one- or two-dimensional images while the object is rotating or being transported.
• Japanese Patent Application Laid-Open No. 2011-174893 proposes a method of changing the diameter of magnetic particles that adhere to each flaw size by mixing magnetic particles of multiple sizes, with each size having a different excited emission color. As a result, different colors are excited and emitted depending on the flaw size, and so a color camera can be used to detect the size (i.e., the depth of the flaw, etc.).
• Flaws that occur on the surface of an object include single flaws that occur accidentally on the object, and continuous flaws that occur consecutively on multiple objects due to an abnormality in the equipment. Continuous flaws may continue to occur unless measures are taken, so early detection of continuous flaws is required to prevent the continued production of objects with continuous flaws.
• continuous flaws that occur on steel plates include flaws that occur when a foreign object adheres to a rolling roll and the shape of the foreign object is transferred to the product during rolling. These continuous flaws occur consecutively in the order of production of the manufactured steel plate (manufacturing order), so the continuity is easy to grasp during inspection. For this reason, it is relatively easy to detect continuous flaws on steel plates early.
• the processes after the molding process proceed in an order that differs from the manufacturing order (molding order).
• the reason for the order differing from the manufacturing order is that, for example, last-in, first-out (LIFO) processing is used in various processes such as line-out and loading onto transport carts.
• LIFO last-in, first-out
• the transport order is not an issue since there is no continuity to begin with, but for continuous flaws, the processes after the molding process proceed in an order that differs from the molding order, so information regarding the continuity of continuous flaws is lost, making early detection of continuous flaws difficult.
• the present disclosure therefore aims to provide a surface inspection device and a surface inspection method that can detect continuous flaws at an early stage.
• a first aspect of the present disclosure is a surface inspection device for inspecting the properties of the surface of an object, the surface inspection device having a magnetization unit for magnetizing the object, a magnetic powder adhesion unit for applying a magnetic powder liquid to the magnetized object to adhere magnetic powder to the object, an illumination unit for irradiating ultraviolet light onto the object to which the magnetic powder has been adhered, an imaging unit for generating a plurality of captured images by imaging a plurality of positions along a first direction of the object to which the magnetic powder has been adhered, which has been excited and luminesced by ultraviolet light, and an inspection unit for inspecting the properties of the surface of the object based on the captured images, the inspection unit having a defect identification unit for identifying a defect shown in the inspection image for each inspection image based on the captured images, and a defect identification unit for identifying a defect in the inspection image for the defect identified by the defect identification unit.
• the surface inspection device has a second direction addition processing unit that adds pixel values in a direction corresponding to a second direction perpendicular to the first direction in the inspection images, in a direction corresponding to the second direction, for the plurality of inspection images; a first direction addition processing unit that adds pixel values in a direction corresponding to the first direction in the inspection images, for the flaws identified by the flaw identification unit, in a direction corresponding to the first direction, for the plurality of inspection images; and a continuous flaw determination unit that determines whether the surface of the object has a single flaw that occurs accidentally or a continuous flaw that occurs continuously, based on the addition results in the second direction addition processing unit and the addition results in the first direction addition processing unit.
• a second aspect of the present disclosure is a surface inspection device according to the first aspect, in which the second direction addition processing unit adds up the size of the flaw identified by the flaw identification unit in the direction corresponding to the second direction in the inspection image, taking a predetermined flaw width, and the first direction addition processing unit adds up the size of the flaw identified by the flaw identification unit in the direction corresponding to the first direction in the inspection image, taking a predetermined flaw circumference, and the first direction addition processing unit adds up the size of the flaw identified by the flaw identification unit in the direction corresponding to the first direction in the inspection image, taking a predetermined flaw circumference.
• a third aspect of the present disclosure is the surface inspection device according to claim 1, which is the surface inspection device according to the first or second aspect, and further includes a continuous flaw position output unit that, when the continuous flaw determination unit determines that a continuous flaw has occurred, identifies and outputs the position of the continuous flaw based on the position of the flaw identified by the flaw identification unit, the addition result in the second direction addition processing unit, and the addition result in the first direction addition processing unit.
• a fourth aspect of the present disclosure is a surface inspection device according to any one of the first to third aspects, the surface inspection device according to claim 1 having a rotation unit that rotates the object around a rotation axis parallel to the second direction, and the imaging unit generates the multiple captured images by imaging multiple positions of the object along the first direction while rotating the object with the rotation unit.
• a fifth aspect of the present disclosure is a surface inspection method for inspecting the properties of the surface of an object, using a surface inspection device having a magnetization unit that magnetizes the object, a magnetic powder adhesion unit that applies a magnetic powder liquid to the magnetized object to adhere magnetic powder to the object, an illumination unit that irradiates ultraviolet light onto the object to which the magnetic powder has been adhered, an imaging unit that generates a plurality of captured images by imaging a plurality of positions along a first direction of the object to which the magnetic powder has been excited and luminesced by ultraviolet light, and an inspection unit that inspects the properties of the surface of the object based on the captured images, and using the inspection unit to identify defects that appear in the inspection images for each inspection image based on the captured images, and a defect identification step that identifies defects identified by the defect identification unit in the inspection images.
• the surface inspection method includes a second direction addition process step of adding pixel values in a direction corresponding to a second direction perpendicular to the first direction in the inspection images for a plurality of the inspection images in a direction corresponding to the second direction, a first direction addition process step of adding pixel values in a direction corresponding to the first direction in the inspection images for a flaw identified by the flaw identification unit in a direction corresponding to the first direction for a plurality of the inspection images, and a continuous flaw determination step of determining whether an accidental single flaw or continuous flaws have occurred on the surface of the object based on the addition results in the second direction addition process step and the addition results in the first direction addition process step.
• This disclosure provides a surface inspection device and a surface inspection method that can detect continuous flaws at an early stage.
• FIG. 1 is a diagram showing an example of a schematic configuration of a surface inspection device according to an embodiment of the present disclosure and an object to be inspected for surface texture;
• FIG. 2 is a block diagram showing an example of a functional configuration of the processing device.
• FIG. 13 is a diagram showing an example in which an inspection image is generated from a plurality of captured images.
• FIG. 1 is a diagram showing an example of an inspection image obtained for a plurality of objects.
• FIG. 1 is a diagram showing an example of an inspection image obtained for a plurality of objects.
• FIG. 13 is a diagram showing an example of a plurality of inspection images.
• 1A and 1B are diagrams showing an example of a plurality of inspection images and a first flaw image.
• FIG. 13A and 13B are diagrams showing an example of a plurality of inspection images and a second flaw image.
• 1A and 1B are diagrams showing an example of a plurality of inspection images and a first flaw image.
• 13A and 13B are diagrams showing an example of a plurality of inspection images and a second flaw image.
• 1A and 1B are diagrams showing an example of a plurality of inspection images and a first flaw image.
• 13A and 13B are diagrams showing an example of a plurality of inspection images and a second flaw image.
• FIG. 13 is a diagram showing an example of the position of a continuous flaw identified based on a plurality of inspection images.
• FIG. 2 is a block diagram showing an example of a hardware configuration of a processing device.
• 13 is a flowchart showing an example of the flow of a surface inspection process.
• FIG. 13 is a diagram showing a modified example in which the inspection image is corrected.
• FIG. 13 is a
• Magnetic particle inspection explanation In one embodiment of the present disclosure, a surface inspection device that performs magnetic particle inspection for the surface quality of an object to be inspected is described. In the magnetic particle inspection, an inspection is performed for minute defects on the surface of the object that are difficult to visually recognize (hereinafter, referred to as "magnetic particle defects").
• (Description of the configuration of the surface inspection device 10) 1 shows an example of a schematic configuration of a surface inspection device 10 according to an embodiment of the present disclosure and an object 80 to be inspected for surface properties.
• the object 80 is a ferromagnetic object.
• the object 80 is, for example, an integrally molded product including a forged product.
• the shape of the object 80 is a square prism, and a surface inspection of the outer circumferential surface of the object 80 is performed while rotating the object 80.
• the shape of the object 80 may be any shape, and it is not necessary to rotate the object 80.
• the surface inspection device 10 is an inspection device that inspects the surface properties of an object 80.
• the surface inspection device 10 has a magnetization device 12, a magnetic powder adhesion device 14, a rotation device 16, an illumination device 18, an imaging device 20, a marking device 22, and a processing device 24.
• the magnetization device 12 is a device that magnetizes the target object 80, which is a ferromagnetic material.
• the magnetization device 12 is an example of the magnetization unit of the present disclosure.
• the magnetic powder attachment device 14 is a device that applies a magnetic powder liquid to the object 80 magnetized by the magnetization device 12, and attaches magnetic powder to the object 80.
• the magnetic powder attachment device 14 is an example of the magnetic powder attachment section of the present disclosure.
• the rotation device 16 is a mechanism for rotating the object 80 around a rotation axis parallel to a second direction described later. More specifically, the rotation device 16 is a mechanism for rotating the object 80 around a rotation axis parallel to a direction perpendicular to the optical axis of the imaging device 20 described later so as to show the outer peripheral surface to be inspected of the object 80 to the optical axis of the imaging device 20 described later.
• the rotation device 16 has a reducer, a motor, etc., and is therefore capable of rotating the object 80 at a desired speed. In this embodiment, the rotation device 16 rotates the object 80 around an axis perpendicular to the optical axis of the imaging device 20 of the rectangular prism-shaped object 80.
• the rotation device 16 is an example of a rotating unit of the present disclosure.
• the lighting device 18 irradiates ultraviolet light onto the object 80 (more precisely, the space including the object 80) to which the magnetic powder is attached.
• the lighting device 18 may be, for example, a ring-shaped lighting device that emits ultraviolet light.
• the lighting device 18 is arranged coaxially with the imaging device 20 described below, and is configured to irradiate ultraviolet light onto a range (irradiation range) including the imaging range 20A of the imaging device 20.
• the lighting device 18 may be configured such that the ultraviolet light from the lighting device 18 is uniformly irradiated onto the irradiation range by providing a diffusion film on the front surface of the lighting device 18, for example.
• the lighting device 18 is an example of a lighting unit of the present disclosure.
• the imaging device 20 generates multiple captured images by capturing images of multiple positions along a first direction, described below, of the object 80 to which magnetic powder that is excited and luminous by ultraviolet light is attached.
• the imaging device 20 is a camera capable of capturing monochrome or color images of the surface of the object 80 (for example, the outer peripheral surface around the rotation axis).
• the imaging device 20 may be, for example, a two-dimensional camera in which imaging elements such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) are arranged two-dimensionally.
• the imaging device 20 is positioned so that the optical axis of the imaging device 20 is included in a plane including the rotation axis of the object 80.
• the imaging device 20 captures an image of at least a range including the outer peripheral surface of the object 80 visible from the imaging device 20 as the imaging range 20A so that the outer peripheral surface is included in the angle of view of the imaging device 20.
• the imaging device 20 is positioned so that the optical axis of the imaging device 20 is coaxial with the lighting device 18.
• the imaging sensitivity can be brought to a state close to maximum.
• the captured image captures magnetic particles that are attached to the surface of the object 80 and are excited and luminous by ultraviolet light irradiated from the lighting device 18.
• the imaging device 20 When generating multiple captured images, the imaging device 20 generates each captured image by changing the relative positional relationship with one object 80 along a certain direction that can be set arbitrarily.
• the direction in which the relative positional relationship changes is referred to as the first direction. Therefore, for example, when an image is generated in a state in which the object 80 is rotating by the rotation device 16, the first direction is the direction (rotation direction, circumferential direction) in which the rotation speed of the object 80 is moving on the optical axis of the imaging device 20, and each position of the surface of the object 80 captured in each captured image is apparently aligned along the first direction on the optical axis of the imaging device 20.
• the direction perpendicular to the first direction is referred to as the second direction.
• the second direction is a direction parallel to the rotation axis when the object 80 rotates.
• the imaging device 20 is an example of an imaging unit of the present disclosure.
• the marking device 22 is a device that marks the surface of the object 80.
• the marking device 22 may be, for example, a robot arm with a drawing tool at its tip.
• the marking device 22 draws specified symbols, letters, marks, etc. at specified positions on the surface of the object 80, for example, at positions where problematic surface characteristics have been detected. In this way, it becomes possible to easily check positions on the surface of the object 80 that will become the product that are problematic in terms of quality.
• the processing device 24 is a device that performs various controls related to the surface inspection device 10 and various calculations related to the inspection of the target object 80, and is configured by a computer with a hardware configuration described below.
• FIG. 2 shows an example of the functional configuration of the processing device 24.
• the processing device 24 includes, as its functional configuration, a control unit 26 and an inspection unit 28.
• the control unit 26 is a functional unit that controls the various devices included in the surface inspection device 10 to perform their functions. More specifically, the control unit 26 controls each of the magnetization device 12, the magnetic powder adhesion device 14, the rotation device 16, the lighting device 18, the imaging device 20, and the marking device 22.
• the control unit 26 controls the magnetization device 12 and the magnetic powder adhesion device 14 to operate them, magnetize the object 80, and apply magnetic powder liquid to the magnetized object 80 to adhere magnetic powder to the surface of the object 80.
• the control unit 26 also turns on the lighting device 18 and starts irradiating ultraviolet light.
• the control unit 26 also operates the rotation device 16 to rotate the object 80. Note that the lighting device 18 remains on until the inspection is completed.
• the control unit 26 synchronizes the timing of various controls by acquiring the rotation angle and rotation period of the object 80 from a rotary encoder or the like provided on the rotation device 16.
• the control unit 26 also causes the imaging device 20 to capture images of the surface of the object 80 in accordance with a predetermined period of rotation of the object 80, thereby generating multiple captured images relating to multiple points along the circumferential direction (first direction) around the entire outer periphery of the object 80.
• the control unit 26 then acquires the captured images generated by the imaging device 20 from the imaging device 20.
• the control unit 26 controls the rotation device 16 to stop the rotation of the object 80.
• the inspection unit 28 performs an inspection of the surface of the object 80 based on the captured images acquired by the control unit 26.
• the inspection unit 28 has, as functional units for performing the inspection, an image linking unit 30, a flaw identification unit 32, a second direction addition processing unit 34, a first direction addition processing unit 36, a continuous flaw determination unit 38, and an output unit 44.
• each functional unit of the inspection unit 28 performs data processing on the multiple captured images acquired by the control unit 26, thereby obtaining an inspection result regarding the surface properties of the surface of the object 80. The inspection results will be described later.
• the image connection unit 30 extracts a central image area 50A, which is a part of the captured image 50, from each captured image 50 obtained by capturing an image of an object 80 with the imaging device 20.
• the central image area 50A is an image area located at the center of the vertical direction of the captured image 50 (a direction corresponding to the first direction. For example, if the captured image is captured by rotating the object 80, a direction corresponding to the rotation direction of the object 80 on the optical axis of the imaging device 20) and extending from one end to the other end of the horizontal direction of the captured image 50 (a direction corresponding to the second direction.
• the central image area 50A is an area on the captured image 50 that corresponds to the imaging area 20A1 located on the optical axis of the imaging device 20 within the imaging range 20A of the imaging device 20 and extending from one end to the other end in the direction of the rotation axis of the object 80.
• the control unit 26 causes the imaging device 20 to capture images of the surface of the rotating object 80 at a predetermined pitch so that a central image area 50A of the entire circumference of the object 80 is obtained.
• the image linking unit 30 then links the central image areas 50A of the entire circumference of each object 80 in the order they were captured, thereby generating the inspection image 52.
• each object 80 is rotated from a predetermined posture
• the position of the magnetic particle flaw is identified based on the coordinates of the inspection image 52, assuming that the object 80 is rotated from a predetermined position. Therefore, if the object 80 is rotated from a position different from the predetermined position, a discrepancy occurs between the position of the magnetic particle flaw on the inspection image 52 and the position of the magnetic particle flaw on the surface of the object 80, and the correct position of the magnetic particle flaw cannot be identified.
• the posture (up and down, left and right, rotation angle) of the object 80 when it is placed is adjusted so that the object 80 can start rotating from a predetermined posture.
• the rotation angle of the object 80 may be detected by a rotary encoder or the like provided in the rotation device 16, and the control unit 26 may control the rotation device 16 based on the detection result to cause the object 80 to start rotating from a predetermined posture.
• the object 80 is not a highly symmetrical shape such as a cylindrical shape, but has a shape with a biased center of gravity due to an asymmetrical shape
• the object 80 will move to a position where its center of gravity is lowered due to the bias of the center of gravity of the object 80, and the object 80 can be rotated from the changed posture, thereby reducing the labor required for posture adjustment.
• the positions of the object 80 corresponding to the starting end 52A and the ending end 52B of the inspection image 52 can be aligned across multiple inspection images 52, making it possible to identify the position of the magnetic particle flaw based on the coordinates of each inspection image 52.
• n inspection images 52 for n objects 80 are shown, and a pseudo-pattern portion 54 appears as an image in each inspection image 52.
• magnetic particle liquid may accumulate due to changes in shape or skin condition of the object 80, and the accumulated magnetic particle liquid may show a pattern similar to a scratch (i.e., a pseudo-pattern).
• a pseudo-pattern is not caused by harmful defects (leakage magnetic flux) such as scratches on the surface of the object 80, and is therefore harmless to the quality of the object 80.
• the pseudo-pattern portion 54 is a portion that shows a pseudo-pattern. As an example, the pseudo-pattern portion 54 occurs at a corner that connects the sides of the object 80, which is a rectangular prism.
• the pseudo-pattern portion 54 occurs in a specific portion of the object 80. Therefore, it is possible to identify the position of the pseudo-pattern portion 54 based on the design shape of the object 80. Also, as described above, by aligning the positions of the object 80 corresponding to the starting end 52A and the ending end 52B of the inspection image 52 in multiple inspection images 52, the coordinates of the inspection image 52 corresponding to the position of the pseudo-pattern portion 54 become constant in each inspection image 52. Therefore, it is possible to set a pseudo-pattern area 56, which is an image area where the pseudo-pattern portion 54 occurs, on the inspection image 52 based on the position of the pseudo-pattern portion 54 on the object 80.
• the flaw identification unit 32 identifies flaws captured in the inspection images 52 for each inspection image 52 based on the captured image 50. More specifically, the flaw identification unit 32 first acquires data on the shape of the object 80, and identifies the position of the pseudo pattern portion 54 on the object 80 based on the shape of the object 80. The data on the shape of the object 80 may be stored in advance in the processing device 24, or may be provided to the processing device 24 from outside. Then, the flaw identification unit 32 sets a pseudo pattern area 56, which is the image area where the pseudo pattern portion 54 occurs, on the inspection image 52 based on the identified position of the pseudo pattern portion 54 on the object 80.
• the flaw identification unit 32 sets the effective image area of the inspection image 52 excluding the pseudo pattern area 56 as the inspection area 58. Then, the flaw identification unit 32 performs a predetermined image processing on the inspection area 58. Specifically, the flaw identification unit 32 performs a predetermined pre-processing such as shading and smoothing on the inspection area 58. The flaw identification unit 32 also binarizes the inspection area 58 after pre-processing based on a predetermined threshold. The threshold may be experimentally determined in advance based on the type of object 80, etc. Then, the flaw identification unit 32 removes noise components from the binarized inspection area 58 by a predetermined process. This causes the magnetic powder flaw 60 to be extracted from the inspection area 58.
• a predetermined image processing such as shading and smoothing on the inspection area 58.
• the flaw identification unit 32 also binarizes the inspection area 58 after pre-processing based on a predetermined threshold. The threshold may be experimentally determined in advance based on the type of object 80,
• the magnetic powder flaws 60 are flaws that are harmful to the quality of the object 80 and may be single or continuous flaws, but at this point, it is not possible to determine whether the magnetic powder flaw 60 is a single or continuous flaw. Early detection of continuous flaws is required to prevent the continued production of objects 80 with continuous flaws due to an abnormality in the equipment, etc. Note that the magnetic powder flaws 60 are an example of a flaw disclosed herein.
• the flaw identification unit 32 identifies magnetic powder flaws 60 that are captured in areas of the surface of the object 80 other than the pseudo pattern area 56 based on the inspection image 52. That is, the flaw identification unit 32 determines whether or not the magnetic powder flaw 60 is displayed as an image in the inspection area 58 of the inspection image 52, and identifies the presence, position, size, etc. of the magnetic powder flaw 60 in the inspection image 52.
• the magnetic powder flaw 60 is identified based on, for example, the brightness value and coordinates on the inspection image 52 of the magnetic powder flaw 60 that appears as an image in the inspection image 52, the pitch obtained from a rotary encoder of the rotating device 16, the size of the object 80, and other information.
• the control unit 26 identifies the magnetic powder flaws 60 that are captured in the inspection image 52 by the flaw identification unit 32, and stores information about the identified magnetic powder flaws 60 (existence, position, size, etc.) in the processing device 24.
• the control unit 26 also controls the marking device 22 to mark the position of the magnetic powder flaw 60. Specifically, the control unit 26 notifies the marking device 22 of the position of the magnetic powder flaw 60 stored in the processing device 24, and controls the marking device 22 to mark the position of the magnetic powder flaw 60.
• the second direction addition processing unit 34 adds pixel values of the flaws identified by the flaw identification unit 32 in the direction corresponding to the second direction in the inspection image 52 for the multiple inspection images 52.
• FIG. 7 shows an example of multiple inspection images 52 and a first flaw image 62.
• the second direction addition processing unit 34 arranges the n inspection images 52 in a direction corresponding to the second direction, adds the brightness values of the flaws depicted in each of the inspection images 52 in the direction corresponding to the second direction, and generates a first flaw image 62 showing the addition result.
• the second direction is the axial direction of the rotation axis when rotating the object 80
• the direction corresponding to the second direction is the horizontal direction in the inspection image 52 (or the captured image 50)
• the first direction is the circumferential direction when rotating the object 80
• the direction corresponding to the first direction is the vertical direction in the inspection image 52 (or the captured image 50).
• the first flaw image 62 is not processed in the direction corresponding to the first direction, and is merely added in the direction corresponding to the second direction, so that the first flaw image 62 includes information regarding the position of the magnetic powder flaw 60 in the first direction (circumferential position).
• the second direction addition processing unit 34 may convert the size of the magnetic powder flaw 60 in the inspection image 52 (i.e., the width size of the pixel containing the pixel value corresponding to the magnetic powder flaw 60) to a predetermined size (hereinafter also referred to as the flaw width) regardless of the size of the magnetic powder flaw 60, and then perform the addition. Specifically, for example, even if the inspection image 52 shows a magnetic powder flaw 60 with a length of 30 pixels in the axial direction of the object 80 and a magnetic powder flaw 60 with a length of 2 pixels as an image, the length of the first flaw image 62 is unified to 5 pixels, etc.
• the width of the first flaw image 62 is converted to 6 pixels, etc.
• the position of the first flaw image 62 after size conversion is set based on the center of gravity of the magnetic powder flaw 60. This makes it possible to make the added value dependent on the number of magnetic powder flaws 60 that appear at the corresponding position, rather than on the widthwise size of the magnetic powder flaw 60.
• FIG. 8 shows an example of multiple inspection images 52 and a second flaw image 64.
• the first direction addition processing unit 36 arranges the n inspection images 52 in a direction corresponding to the first direction, similar to the first flaw image 62, and adds the brightness values of flaws depicted in each of the inspection images 52 in the direction corresponding to the first direction to generate a second flaw image 64 showing the addition result.
• the second flaw image 64 is not processed in the direction corresponding to the second direction, and is simply added in the direction corresponding to the first direction, so the second flaw image 64 includes information regarding the position in the second direction (axial position) of the magnetic powder flaw 60.
• the first direction addition processing unit 36 may convert the size of the magnetic powder flaw 60 in the inspection image 52 (i.e., the circumferential size of the pixel containing the pixel value corresponding to the magnetic powder flaw 60) to a predetermined size (hereinafter also referred to as the flaw circumference) regardless of the size of the magnetic powder flaw 60, and then perform the addition. Specifically, for example, even if the inspection image 52 shows a magnetic powder flaw 60 with a width of 6 pixels in the circumferential direction of the object 80 and a magnetic powder flaw 60 with a width of 2 pixels as an image, the width of the second flaw image 64 is unified to 3 pixels, etc.
• the length of the second flaw image 64 is converted to 20 pixels, etc.
• the position of the second flaw image 64 after size conversion is set based on the center of gravity of the magnetic powder flaw 60. This makes it possible to make the added value dependent on the number of magnetic powder flaws 60 that appear at the corresponding position, rather than on the circumferential size of the magnetic powder flaw 60.
• FIG. 9 shows an example of multiple inspection images 52 and a first flaw image 62.
• the added value (axial added value) obtained by adding in the direction corresponding to the axial direction and the axial threshold value will be described.
• the added value obtained by adding in the direction corresponding to the axial direction corresponds to the total number of pixels in the axial direction of the added magnetic powder flaw 60.
• the added value obtained by adding in the direction corresponding to the axial direction is shown by the length of the bar graph 70 shown by the added first flaw image 62.
• the axial threshold value is a threshold value used to determine whether a continuous flaw 68 has occurred. In other words, if the added value obtained by adding in the direction corresponding to the axial direction exceeds the axial threshold value, there is a possibility that a continuous flaw 68 has occurred.
• the axial threshold value is set to a value of 2 pixels or more and less than 3 pixels of the bar graph in the first flaw image 62.
• the specific value of the axial threshold value can be set arbitrarily.
• the size of the magnetic powder flaw 60 in the inspection image 52 can be set to a predetermined size before generation, regardless of the size of the magnetic powder flaw 60 (the length in the direction corresponding to the width direction of the magnetic powder flaw 60 in the inspection image 52). This makes it possible to obtain an added value in the direction corresponding to the axial direction according to the number of magnetic powder flaws 60 without being affected even if the length of the magnetic powder flaws 60 differs or noise occurs in the inspection image 52.
• FIG. 10 shows an example of multiple inspection images 52 and a second flaw image 64.
• the sum obtained by adding in the direction corresponding to the circumferential direction (circumferential sum) and the circumferential threshold will be described.
• the sum obtained by adding in the direction corresponding to the circumferential direction corresponds to the total number of pixels in the circumferential direction of the added magnetic powder flaw 60.
• the sum obtained by adding in the direction corresponding to the circumferential direction is shown by the length of the bar graphs 72A and 72B shown by the added second flaw image 64.
• the circumferential threshold is a threshold used to determine whether a continuous flaw 68 has occurred. In other words, if the sum obtained by adding in the direction corresponding to the circumferential direction exceeds the circumferential threshold, there is a possibility that a continuous flaw 68 has occurred.
• the circumferential threshold is set to a value of 2 pixels or more and less than 3 pixels of the bar graph in the second flaw image 64.
• the specific value of the circumferential threshold can be set arbitrarily.
• the size of the magnetic powder flaw 60 in the inspection image 52 can be set to a predetermined size before generation, regardless of the size of the magnetic powder flaw 60 (the length in the direction corresponding to the circumferential direction of the magnetic powder flaw 60 in the inspection image 52). This makes it possible to obtain an added value in the direction corresponding to the circumferential direction according to the number of magnetic powder flaws 60 without being affected even if the width of the magnetic powder flaw 60 differs or noise occurs in the inspection image 52.
• FIG. 11 shows an example of multiple inspection images 52 and a first flaw image 62.
• the second direction addition processor 34 adds the pixel value corresponding to the single flaw 66 and the pixel value corresponding to the continuous flaw 68 in the second direction in the same manner as above to generate the first flaw image 62.
• FIG. 12 shows an example of multiple inspection images 52 and a second flaw image 64.
• the first direction addition processor 36 adds the pixel value corresponding to the single flaw 66 and the pixel value corresponding to the continuous flaw 68 in the first direction in the same manner as above to generate a second flaw image 64.
• the continuous flaw determination unit 38 determines whether an accidental single flaw or continuous flaws have occurred on the surface of the object 80 based on the sum of the second direction summation processing unit 34 and the first direction summation processing unit 36. More specifically, the continuous flaw determination unit 38 determines whether continuous flaws 68 have occurred continuously on multiple objects 80 based on the sum of the axial direction corresponding to the axial direction added by the second direction summation processing unit 34 and the sum of the circumferential direction corresponding to the circumferential direction added by the first direction summation processing unit 36.
• the continuous flaw determination unit 38 compares the sum of the axial direction corresponding to each axial direction with the axial threshold value, and compares the sum of the circumferential direction corresponding to each circumferential direction with the circumferential threshold value. If the sum of the axial direction corresponding to each axial direction is below the axial threshold value, or if the sum of the circumferential direction corresponding to each circumferential direction is below the circumferential threshold value, the continuous flaw determination unit 38 determines that no continuous flaws 68 have occurred.
• the continuous flaw determination unit 38 determines that a continuous flaw 68 has occurred if there is an added value in the axial direction that exceeds the axial threshold value, and there is an added value in the circumferential direction that exceeds the circumferential threshold value.
• the added values in the directions corresponding to each circumferential direction are below the circumferential threshold value, or the added values in the directions corresponding to each axial direction are also below the axial threshold value, so the continuous flaw determination unit 38 determines that a continuous flaw 68 has not occurred.
• the continuous flaw determination unit 38 determines that a continuous flaw 68 has occurred.
• the continuous flaw determination unit 38 determines that a continuous flaw 68 has occurred, then the magnetic powder flaw 60 on the surface of the object 80 has been determined to be a continuous flaw 68.
• the flaw identification unit 32 determines that there is a magnetic powder flaw 60 on the surface of the object 80, and then the continuous flaw determination unit 38 determines that no continuous flaw 68 has occurred, then the magnetic powder flaw 60 on the surface of the object 80 has been determined to be not a continuous flaw 68, i.e., the magnetic powder flaw 60 has been determined to be a single flaw 66. Therefore, the continuous flaw determination unit 38 can be considered as a determination unit that determines whether the magnetic powder flaw 60 is a single flaw 66 or a continuous flaw 68.
• the output unit 44 (continuous flaw position output unit) identifies the position of the continuous flaw 68 based on the added value in the direction corresponding to the axial direction, the added value in the direction corresponding to the circumferential direction, the circumferential position of the magnetic powder flaw 60 shown in the first flaw image 62, and the axial position of the magnetic powder flaw 60 shown in the second flaw image 64.
• the output unit 44 identifies the circumferential position of the continuous flaw 68 based on a bar graph 70 in which the added value in the direction corresponding to the axial direction exceeds the axial threshold value, and identifies the axial position of the continuous flaw 68 based on a bar graph 72 in which the added value in the direction corresponding to the circumferential direction exceeds the circumferential threshold value.
• FIG. 13 shows an example of the position of a continuous flaw 68 identified based on multiple inspection images 52.
• the example shown in FIG. 13 is the same as the example shown in FIG. 11 and FIG. 12.
• the position where the circumferential position of the continuous flaw 68 and the axial position of the continuous flaw 68 overlap is identified as the position of the continuous flaw 68.
• the output unit 44 then outputs to the outside the inspection result including the result of the continuous flaw determination unit 38 determining that the continuous flaw 68 has occurred and the position of the continuous flaw 68.
• the output unit 44 may identify the object 80 that has been determined to have the continuous flaw 68 by the continuous flaw determination unit 38, and include the identified object 80 and the position of the identified continuous flaw 68 in the inspection results.
• the output unit 44 may also include warning information in the inspection results that warns of an abnormality, such as the occurrence of the continuous flaw 68.
• FIG. 14 shows an example of the hardware configuration of the processing device 24.
• the processing device 24 is configured by a computer.
• the processing device 24 has a CPU (Central Processing Unit) 90, a memory 92, a storage device 94, an input device 96, an output device 98, a storage medium reading device 100, and a communication I/F (Interface) 102.
• Each component is connected to each other so that they can communicate with each other via a bus 104.
• the storage device 94 stores programs for executing the surface inspection process.
• the CPU 90 is a central processing unit that executes various programs and controls each component. That is, the CPU 90 reads the programs from the storage device 94 and executes the programs using the memory 92 as a working area. The CPU 90 controls each of the components and performs various calculation processes according to the programs stored in the storage device 94.
• Memory 92 is made up of RAM (Random Access Memory) and serves as a working area to temporarily store programs and data.
• Storage device 94 is made up of ROM (Read Only Memory), HDD (Hard Disk Drive), SSD (Solid State Drive), etc., and stores various programs and data, including the operating system.
• the input device 96 is a device for performing various inputs, such as a keyboard or a mouse.
• the output device 98 is a device for outputting various information, such as a display or a printer.
• a touch panel display may be used as the output device 98 to function as the input device 96.
• the storage medium reading device 100 reads data stored in 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.
• an interface conforming to standards such as Ethernet (registered trademark), FDDI, or Wi-Fi (registered trademark), for example, is used.
• the computer is made up of the CPU 90, memory 92, and storage device 94.
• the computer may be configured as a sub-computer that controls part of the operation of the processing device 24, or as a main computer that controls the entire operation of the processing device 24.
• an integrated circuit such as an LSI (Large Scale Integration) or an IC (Integrated Circuit) chip set may be used for part or all of the computer.
• the integration of the computer is not limited to LSI, and a dedicated circuit or processor may be used.
• the processor referred to here is a processor in a broad sense, and may be a general-purpose processor or may include a dedicated processor such as a GPU (Graphics Processing Unit), an ASIC (Application Specific Integrated Circuit), or an FPGA (Field Programmable Gate Array).
• the operation of the processor may be performed not only by a single processor, but also by multiple processors located at physically separate locations working together.
• (Explanation of surface inspection method) 15 shows an example of the flow of surface inspection processing executed by the CPU 90 of the processing device 24.
• the CPU 90 reads out a program for executing the surface inspection processing from the storage device 94, expands it into the memory 92, and executes it, whereby the CPU 90 functions as each functional unit of the processing device 24 and executes the surface inspection processing.
• the surface inspection method is executed in the surface inspection device 10.
• the object 80 is carried into the surface inspection device 10.
• step S10 the control unit 26 controls the magnetization device 12 and the magnetic powder adhesion device 14 to operate them.
• the magnetization device 12 executes a magnetization step of magnetizing the target object 80
• the magnetic powder adhesion device 14 executes a magnetic powder adhesion step of applying a magnetic powder liquid to the target object 80 magnetized by the magnetization device 12 to adhere the magnetic powder.
• step S12 the control unit 26 controls the lighting device 18 to turn it on. This causes the lighting device 18 to execute an illumination step of illuminating the space including the object 80 with ultraviolet light.
• step S14 the control unit 26 controls the rotation device 16 to operate it.
• the rotation device 16 executes a rotation step in which the object 80 is rotated around the central axis of the object 80 as the rotation axis.
• step S16 the control unit 26 controls the imaging device 20 to capture an image of the surface of the object 80 in accordance with a predetermined period of rotation of the object 80.
• the imaging device 20 executes an imaging step of capturing an image of the surface of the object 80 to which magnetic powder is attached in a space illuminated with ultraviolet light by the lighting device 18.
• step S18 the image linking unit 30 executes an image linking step in which it extracts a central image area 50A from each captured image 50, and links the central image areas 50A of the entire circumference of the object 80 in the order they were captured to generate an inspection image 52. As a result, an inspection image 52 is obtained for each object 80.
• step S20 the flaw identification unit 32 identifies the position of the pseudo-pattern portion 54 on the surface of the object 80, and executes a region setting step in which a pseudo-pattern region 56, which is the image region in which the pseudo-pattern portion 54 occurs, is set on the inspection image 52.
• step S22 the flaw identification unit 32 sets the effective image area of the inspection image 52 excluding the pseudo pattern area 56 as the inspection area 58, and executes an image processing step in which predetermined image processing (e.g., predetermined preprocessing, binarization processing, and noise removal processing) is performed on the inspection area 58.
• predetermined image processing e.g., predetermined preprocessing, binarization processing, and noise removal processing
• step S24 the flaw identification unit 32 executes a flaw identification step to determine whether or not a magnetic powder flaw 60 is present on the surface of the object 80 by determining whether or not a magnetic powder flaw 60 is present as an image in the inspection area 58 of the inspection image 52.
• the flaw identification unit 32 determines that a magnetic powder flaw 60 is present on the surface of the object 80, the surface inspection process proceeds to step S26.
• step S26 the control unit 26 identifies the position of the magnetic powder flaw 60 from the inspection image 52, and executes a storage step to store the identified position of the magnetic powder flaw 60 in the storage device 94.
• step S28 the control unit 26 executes a marking step in which the marking device 22 is controlled to mark the position of the magnetic powder flaw 60.
• step S30 the second direction addition processing unit 34 executes an image generation step in which it generates a first flaw image 62 indicating the circumferential position of the magnetic powder flaw 60 based on the inspection image 52, and the first direction addition processing unit 36 executes an image generation step in which it generates a second flaw image 64 indicating the axial position of the magnetic powder flaw 60.
• step S32 the second direction addition processing unit 34 executes a second direction addition processing step in which the pixel values of the first flaw image 62 in which the circumferential position of the magnetic powder flaw 60 is the same are added to calculate an added value in the direction corresponding to the axial direction
• the first direction addition processing unit 36 executes a first direction addition processing step in which the pixel values of the second flaw image 64 in which the axial position of the magnetic powder flaw 60 is the same are added to calculate an added value in the direction corresponding to the circumferential direction.
• the second direction addition processing unit 34 executes an addition process in which the pixel values of the first flaw image 62 are added when the first flaw image 62 in which the circumferential position of the magnetic powder flaw 60 is the same is generated.
• the first direction addition processing unit 36 executes an addition process in which the pixel values of the second flaw image 64 are added when the second flaw image 64 in which the axial position of the magnetic powder flaw 60 is generated is generated.
• step S34 the continuous flaw determination unit 38 executes a continuous flaw determination step to determine whether or not a continuous flaw 68 has occurred based on the result of comparing the added value in the direction corresponding to the axial direction with the axial threshold value and the result of comparing the added value in the direction corresponding to the circumferential direction with the circumferential threshold value.
• the continuous flaw determination unit 38 determines that a continuous flaw 68 has occurred, the surface inspection process proceeds to step S36.
• step S36 the output unit 44 identifies the circumferential and axial positions of the continuous flaw 68, and outputs to the outside the inspection results including the result that it has been determined that the continuous flaw 68 has occurred and the position of the continuous flaw 68. After the output unit 44 outputs to the outside the inspection results, the surface inspection process ends.
• step S24 determines in step S24 that there are no magnetic powder flaws 60 on the surface of the object 80
• the surface inspection process proceeds to step S38. In this case, since there are no magnetic powder flaws 60 on the object 80, the object 80 is transported from the surface inspection device 10 to the next process.
• step S34 determines in step S34 that there are no continuous flaws 68
• step S38 proceeds to step S38. In this case, since there are no continuous flaws 68 on the object 80, the object 80 is transported from the surface inspection device 10 to the next process.
• step S38 the CPU 90 determines whether or not surface inspection has been completed for all of the objects 80. If surface inspection has not been completed for all of the objects 80, the surface inspection process proceeds to step S10, where surface inspection is performed on the next object 80. On the other hand, if surface inspection has been completed for all of the objects 80, the surface inspection process ends.
• the inspection target 80 is magnetized, and the magnetized target 80 is coated with a magnetic powder liquid to attach magnetic powder.
• a space including the target 80 is illuminated with ultraviolet light, and the surface of the target 80 to which magnetic powder is attached is imaged in the space illuminated with ultraviolet light.
• a magnetic powder flaw 60 on the surface is identified, and based on the inspection image 52, a first flaw image 62 showing a position corresponding to the circumferential direction of the magnetic powder flaw 60 and a second flaw image 64 showing a position corresponding to the axial direction of the magnetic powder flaw 60 are generated.
• pixel values of the magnetic powder flaws 60 having the same circumferential position are added in a direction corresponding to the axial direction to calculate an added value in the direction corresponding to the axial direction.
• pixel values of the magnetic powder flaws 60 are added in a direction corresponding to the circumferential direction to calculate an added value in the direction corresponding to the circumferential direction. Then, based on whether or not the added value in the direction corresponding to the axial direction exceeds a preset axial threshold value, and whether or not the added value in the direction corresponding to the circumferential direction exceeds a preset circumferential threshold value, it is determined whether or not continuous flaws 68 have occurred consecutively in the multiple objects 80.
• the second direction addition processing unit 34 can convert the size in the direction corresponding to the width direction of the magnetic powder flaw 60 to a predetermined size before the addition process, regardless of the size of the magnetic powder flaw 60 (particularly, the length of the magnetic powder flaw 60 in the axial direction of the object 80). This makes it possible to obtain an added value in the direction corresponding to the axial direction according to the number of magnetic powder flaws 60 without being affected even if the length of the magnetic powder flaws 60 varies or noise occurs in the inspection image 52.
• the first direction addition processing unit 36 can convert the size of the magnetic powder flaw 60 in the direction corresponding to the circumferential direction to a predetermined size before the addition process, regardless of the size of the magnetic powder flaw 60 (particularly the width of the magnetic powder flaw 60 in the circumferential direction of the target object 80). This makes it possible to obtain an added value in the direction corresponding to the circumferential direction according to the number of magnetic powder flaws 60, without being affected even if the width of the magnetic powder flaw 60 varies or noise occurs in the inspection image 52.
• the position of the continuous flaw 68 is identified based on the added value in the direction corresponding to the axial direction, the added value in the direction corresponding to the circumferential direction, the circumferential position of the magnetic powder flaw 60 identified by the flaw identification unit 32, and the axial position of the magnetic powder flaw 60 identified by the flaw identification unit 32, and the position of the continuous flaw 68 is output. Therefore, not only can the occurrence of the continuous flaw 68 be discovered early, but the position of the continuous flaw 68 can also be identified early.
• the position of the pseudo-pattern portion 54 on the surface of the object 80 is identified based on the shape of the object 80, and it can be determined whether or not there are magnetic particle flaws 60 in areas of the surface of the object 80 other than the pseudo-pattern area 56. This makes it possible to prevent the pseudo-pattern portion 54 from being mistakenly determined to be a continuous flaw 68.
• the object 80 rotates from a predetermined posture. Therefore, the positions of the object 80 corresponding to the starting end 52A and the ending end 52B of the inspection image 52 can be aligned across multiple inspection images 52. This makes it possible to identify the position of the magnetic powder flaw 60 based on the coordinates of each inspection image 52.
• Modification 16 and 17 show modified examples of correcting the inspection image 52.
• the object 80 is rotated from a predetermined posture
• the object 80 is rotated from a posture different from the predetermined posture.
• a marker 82 is provided on the surface of the object 80.
• the marker 82 is provided at a corner of the side of the object 80.
• the marker 82 is formed, for example, from a material that emits fluorescence by excitation.
• the control unit 26 controls the rotation device 16 so that the object 80 rotates one or more times. As a result, two markers 82 appear as images in the inspection image 52 obtained by imaging the object 80 by the imaging device 20 while the object 80 is rotating.
• the inspection unit 28 has a correction unit 46 as an additional functional unit.
• the correction unit 46 corrects the inspection image 52 so that the marker 82 is positioned at a predetermined position within the inspection image 52.
• the inspection image 52 is corrected so that the marker 82 appears as an image at each of the starting end 52A and the ending end 52B of the inspection image 52.
• the corrected inspection image 52 is then used in the above-mentioned surface inspection process.
• the positions of the object 80 corresponding to the start end 52A and end end 52B of the inspection images 52 can be aligned across multiple inspection images 52, so the position of the magnetic particle flaw 60 can be identified based on the coordinates of each inspection image 52.
• a ring-shaped imaging device 20 is used, but a line-shaped imaging device 20 may also be used. Also, a pair of line-shaped lighting devices 18 may be arranged horizontally above and below the imaging device 20. Also, depending on the size and shape of the object 80, multiple lighting devices 18 may be arranged to illuminate from multiple directions.
• the lighting device 18 is arranged so as to illuminate the surface of the object 80 in a direction perpendicular to the surface, but this is not limited to this depending on the shape of the object 80 or the form of the magnetic particle flaw 60.
• the shape of the lighting device 18 is not limited to a ring or line shape.
• the shape of the object 80 is not limited to a rectangular prism. Also, depending on the shape of the object 80, the inspection image 52 may be acquired without rotating the object 80, or the inspection image 52 may be acquired while translating the object 80.
• a two-dimensional camera in which image sensors are arranged two-dimensionally is used as the imaging device 20, but a one-dimensional camera in which image sensors are arranged one-dimensionally may also be used.
• the surface of the object 80 may be maintained based on the marked position.
• the maintenance may be performed by a maintenance device or may be performed manually.
• whether or not a continuous flaw 68 has occurred is determined based on a first determination result of whether or not the sum value in the direction corresponding to the axial direction exceeds the axial threshold value, and a second determination result of whether or not the sum value in the direction corresponding to the circumferential direction exceeds the circumferential threshold value.
• whether or not a continuous flaw 68 has occurred may be determined based on either the first determination result or the second determination result.

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• 2023
  • 2023-07-04 JP JP2024576093A patent/JPWO2024166415A1/ja active Pending
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