Sand mold inspection device

Abstract

This invention provides a sand mold inspection device that can detect the presence or absence of abnormalities in the sprue cup of a sand mold by detecting the boundaries of the irregularities in the sprue cup of the sand mold with high precision. [Solution] The sand mold inspection device 10 comprises an irradiation unit 2 configured to irradiate light onto the sprue cup of the sand mold from multiple directions, an imaging unit 1 that generates multiple brightness images by photographing the sprue cup of the sand mold when light is irradiated from each direction, an image generation unit 3 that generates one inspection image by combining the multiple brightness images, and an image processing unit 4 that inspects for abnormalities in the sprue cup of the sand mold by processing the inspection image according to the part of the sprue cup of the sand mold.

Description

Technical Field

[0006] , , ,

[0001] The present disclosure relates to a sand mold inspection device.

Background Art

[0002] Conventionally, methods for inspecting sand molds have been known. For example, Patent Document 1 describes a method for detecting mold collapse of a master mold formed of sand. In this method, illumination is performed obliquely from the vicinity of the master mold to generate a shadow of a protrusion formed on the concave surface of the master mold on the concave surface, the concave surface of the master mold where the shadow is generated is imaged, and the area value of the shadow of the protrusion formed on the imaged concave surface of the master mold is compared with a previously obtained reference area value to detect mold collapse. Further, in this method, an illumination means is provided facing the concave surface of the master mold, and illumination is performed from four directions. When the area values of the shadows generated in each direction differ from the previously obtained reference area value in two or more directions, it is determined that mold collapse has occurred in the master mold.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the method described in Patent Document 1, four images are obtained corresponding to the four illumination directions, but only partial information on the boundaries of the concavities and convexities of the object can be obtained.

[0005] Therefore, an object of the present disclosure is to provide a sand mold inspection device capable of detecting the presence or absence of an abnormality in the pouring cup of a sand mold by detecting the boundary of the concavities and convexities of the pouring cup of the sand mold with high accuracy.

Means for Solving the Problems

[0006] The sand mold inspection apparatus of this disclosure comprises: an irradiation unit configured to irradiate light onto the sprue cup of the sand mold from multiple directions; an imaging unit that generates multiple brightness images by photographing the sprue cup of the sand mold when light is irradiated from each direction; an image generation unit that generates a single inspection image by combining the multiple brightness images; and an image processing unit that inspects abnormalities in the sprue cup of the sand mold by image processing the inspection image according to the location of the sprue cup of the sand mold. [Effects of the Invention]

[0007] According to this disclosure, by detecting the boundaries of the irregularities in the sprue cup of the sand mold with high precision, it is possible to detect whether or not there is an abnormality in the sprue cup of the sand mold. [Brief explanation of the drawing]

[0008] [Figure 1] This is a diagram showing the configuration of the sand mold inspection device 10. [Figure 2] This diagram shows the irradiation unit 2 and the imaging unit 1. [Figure 3] This diagram shows the shape of the sprue cup at the top of a sand mold. [Figure 4] This diagram shows the shape of the sprue cup at the top of a sand mold. [Figure 5] This is a flowchart illustrating the inspection procedure for sand molds. [Figure 6] This is a diagram illustrating an example of an image used for examination. [Figure 7] This is a diagram illustrating the detailed procedure for step S108. [Figure 8] This diagram shows an example of the R1 test area. [Figure 9] This figure shows an example of a foreign object X1 detected in the inspection area R1. [Figure 10] This diagram shows an example of the R2 test area. [Figure 11] This figure shows examples where the percentage of occlusion in the examination region R2 exceeds a predetermined percentage. [Figure 12] This diagram shows an example of the R3 test area. [Figure 13]It is a diagram showing an example of a foreign object X3 detected in the inspection area R3. [Figure 14] It is a diagram for explaining the classification of the part where the water splashes back.

Embodiment for Carrying Out the Invention

[0009] Hereinafter, embodiments will be described with reference to the drawings. FIG. 1 is a diagram showing the configuration of a mold inspection apparatus 10.

[0010] The mold inspection apparatus 10 includes an irradiation unit 2, a photographing unit 1, an inspection image generation unit 3, an image processing unit 4, and a control unit 5. FIG. 2 is a diagram showing the configurations of the irradiation unit 2 and the photographing unit 1.

[0011] The irradiation unit 2 is configured to irradiate light toward the pouring cup of the mold from a plurality of directions. As shown in FIG. 2, the irradiation unit 2 may have a plurality of light sources 12(1), 12(2), 12(3), 12(4) arranged in a ring shape. The irradiation unit 2 may be a multi-spectral lighting device as used in LumiTrax (registered trademark).

[0012] The photographing unit 1 generates a plurality of luminance images by photographing the pouring cup of the mold when light is irradiated from each direction.

[0013] The inspection image generation unit 3 generates an inspection image by synthesizing a plurality of luminance images. For example, the inspection image generation unit 3 generates an inspection image according to the shape or reflectance of the surface of the pouring cup by synthesizing a plurality of luminance images by the photometric stereo method. The inspection image generation unit 3 may generate an inspection image from a plurality of luminance images by the method described in JP-A-2020-42053 or by LumiTrax (registered trademark).

[0014] The image processing unit 4 inspects for abnormalities in the pouring cup of the mold by performing image processing on the inspection image according to the part of the pouring cup of the mold.

[0015] The control unit 5 controls the entire mold inspection device 10. The display unit 6 displays a message, inspection images, etc. when an abnormality is detected.

[0016] The alarm sound generation unit 7 generates an alarm sound when an abnormality is detected. FIG. 3 and FIG. 4 are diagrams showing the shape of the sprue cup at the upper part of the mold.

[0017] The horizontal cross-section of the sprue cup has a shape of a rounded rectangle composed of a first semi-circle HC1, a rectangle RC, and a second semi-circle HC2. The first semi-circle HC1 constitutes part of the backflow prevention. The backflow prevention is a semi-donut-shaped part provided at a position one step above the bottom surface of the sprue cup, and has the role of preventing the molten metal (molten liquid) from splashing or the flow from being disturbed.

[0018] FIG. 5 is a flowchart showing the inspection procedure of the mold. In step S101, the sprue cup is cleaned.

[0019] In step S102, the control unit 5 sets the control variable i to 1. In step S103, the control unit 5 causes the light source 12(i) of the irradiation unit 2 to emit light.

[0020] In step S104, the imaging unit 1 performs high-speed imaging to generate the i-th image. In step S105, when i = 4, the process proceeds to step S107, and when i ≠ 4, the process proceeds to step S106. In step S106, the control unit 5 increments the control variable i. Then, the process returns to step S103.

[0021] In step S107, the inspection image generation unit 3 generates an inspection image by synthesizing the first image, the second image, the third image, and the fourth image. FIG. 6 is a diagram showing an example of the inspection image.

[0022] In step S108, the image processing unit 4 inspects for abnormalities in the sprue cup of the sand mold by processing the inspection image according to the location of the sprue cup of the sand mold.

[0023] Figure 7 is a diagram illustrating the detailed steps of step S108. In step S201, the image processing unit 4 sets the inner bottom surface of the sprue cup as the inspection area R1. Figure 8 shows an example of the inspection area R1.

[0024] In step S202, the image processing unit 4 determines whether or not a foreign object of a predetermined area or larger exists in the inspection area R1. If a foreign object of a predetermined area or larger exists in the inspection area R1, the process proceeds to step S203. If no foreign object of a predetermined area or larger exists in the inspection area R1, the process proceeds to step S204. For example, the predetermined area can be a diameter of 10 mm.

[0025] Figure 9 shows an example of a foreign object X1 detected in the inspection area R1. For example, the image processing unit 4 generates a difference image between the inspection area R1 of the inspection image of the spout cup to be inspected obtained in step S107 and the inspection area R1 of a pre-stored inspection image of the spout cup in a normal state, and detects a region in the difference image where pixels with a pixel value of a predetermined threshold or higher are continuous. The image processing unit 4 may also detect whether the number of pixels in that region is equal to or greater than the number of pixels corresponding to a predetermined area.

[0026] In step S203, the control unit 5 indicates that a foreign object is present on the bottom surface of the spout cup. For example, the control unit 5 may display a message on the display unit 6 indicating that a foreign object is present on the bottom surface of the spout cup, along with an inspection image or difference image, and generate an alarm sound from the alarm sound generation unit 7.

[0027] In step S204, the image processing unit 4 sets the area of ​​the sprue hole as the inspection area R2. Figure 10 shows an example of the inspection area R2.

[0028] In step S205, the image processing unit 4 proceeds to step S206 if the percentage of the inspection area R2 that is occluded is greater than or equal to a predetermined percentage. If the percentage of the inspection area R2 that is occluded is not greater than or equal to a predetermined percentage, the unit proceeds to step S207. For example, the predetermined percentage can be 80%.

[0029] Figure 11 shows an example where the percentage of occlusion in the examination area R2 exceeds a predetermined percentage. For example, the image processing unit 4 generates a difference image between the inspection area R2 of the inspection image of the spout cup to be inspected obtained in step S107 and the inspection area R2 of a pre-stored inspection image of the spout cup in a normal state, and detects the area of ​​pixels with a pixel value above a predetermined threshold within the difference image as a blocked area. The image processing unit 4 may also calculate the ratio of the number of pixels in the blocked area to the number of pixels in the inspection area R2 as the blocked percentage.

[0030] In step S206, the control unit 5 indicates that the sprue hole is blocked. The control unit 5 may display a message indicating that the sprue hole is blocked, along with an inspection image or difference image, on the display unit 6, and may also generate an alarm sound from the alarm sound generation unit 7.

[0031] In step S207, the image processing unit 4 sets the area for the water return to the inspection area R3. Figure 12 shows an example of the inspection area R3.

[0032] In step S208, the image processing unit 4 determines whether or not there is a foreign object of a predetermined size or larger in the inspection area R3. If there is a foreign object of a predetermined size or larger in the inspection area R3, the process proceeds to step S209. If there is no foreign object of a predetermined size or larger in the inspection area R3, the process proceeds to step S210. For example, the predetermined size can be a diameter of 10 mm.

[0033] Figure 13 shows an example of a foreign object X3 detected in the inspection area R3. For example, the image processing unit 4 generates a difference image between the inspection area R3 of the inspection image of the spout cup to be inspected obtained in step S107 and the inspection area R3 of a pre-stored inspection image of the spout cup in a normal state, and detects a region in the difference image where pixels with a pixel value of a predetermined threshold or higher are continuous. The image processing unit 4 may also detect whether the number of pixels in that region is equal to or greater than the number of pixels corresponding to a predetermined area.

[0034] In step S209, the control unit 5 notifies that a foreign object is present in the water return container. For example, the control unit 5 may display a message indicating the presence of a foreign object in the water return container, along with an inspection image or difference image, on the display unit 6, and also generate an alarm sound from the alarm sound generation unit 7.

[0035] In step S210, the image processing unit 4 detects the outer contour and the inner contour of the hot water return.

[0036] In step S211, the image processing unit 4 calculates the maximum value MXA of the distance from the center O of the first semicircle HC1 to the outer contour in the scalding region A. The center O is the center of the semicircle that constitutes the inner contour of the scalding.

[0037] Refer to Figure 14 to explain the divisions of the hot water return section. Let line segment L1 be the line segment connecting the center O of the first semicircle HC1 and the rightmost point RE of the first semicircle HC1 located to the right of the center O of the first semicircle HC1. Let line segment L2 be the line segment obtained by rotating line segment L1 counterclockwise by 45 degrees. Let line segment L3 be the line segment obtained by rotating line segment L1 counterclockwise by 135 degrees. Let line segment L4 be the line segment obtained by rotating line segment L1 counterclockwise by 180 degrees. Line segment L4 is also the line segment connecting the center O of the first semicircle HC1 and the leftmost point LE of the first semicircle HC1 located to the left of the center O of the first semicircle HC1.

[0038] In the region where the water is turned over, the area between line segment L1 and line segment L2, and the area between line segment L3 and line segment L4 are defined as region A. In the region where the water is turned over, the area between line segment L2 and line segment L4 is defined as region B.

[0039] In step S212, the image processing unit 4 calculates the minimum value MNA of the distance from the center O of the first semi-circle HC1 to the inner contour in the water splashing region A.

[0040] In step S213, when MNA is greater than or equal to the threshold value TH1 and MXA is less than or equal to the threshold value TH2, the process proceeds to step S215 assuming it is normal. When MNA is less than the threshold value TH1 or MXA is greater than the threshold value TH2, the process proceeds to step S214. For example, TH1 = 65 mm and TH2 = 80 mm can be set.

[0041] In step S214, the control unit 5 notifies that the shape of the water splashing region A is abnormal. For example, the control unit 5 may display a message indicating that the shape of the water splashing region A is abnormal and the inspection image on the display unit 6, and may also generate an alarm sound from the alarm sound generation unit 7.

[0042] In step S215, the image processing unit 4 calculates the maximum value MXB of the distance from the center O of the first semi-circle HC1 to the outer contour in the water splashing region B.

[0043] In step S216, the image processing unit 4 calculates the minimum value MNB of the distance from the center O of the first semi-circle HC1 to the inner contour in the water splashing region B.

[0044] In step S217, when MNB is greater than or equal to the threshold value TH1 and MXB is less than or equal to the threshold value TH3, the process ends assuming it is normal. When MNB is less than the threshold value TH1 or MXB is greater than the threshold value TH3, the process proceeds to step S218.

[0045] Here, TH3 < TH2 can be set. For example, TH2 = 80 mm and TH3 = 75 mm can be set. This is because when the erosion in the part of the water splashing region B becomes large, the spout cup is more likely to collapse, so as to detect abnormalities before collapse.

[0046] In step S218, the control unit 5 indicates that the shape of the water return area B is abnormal. For example, the control unit 5 may display a message indicating that the shape of the water return area B is abnormal and an inspection image on the display unit 6, and also generate an alarm sound from the alarm sound generation unit 7.

[0047] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0048] 1. Imaging unit, 2. Irradiation unit, 3. Inspection image generation unit, 4. Image processing unit, 5. Control unit, 6. Display unit, 7. Alarm sound generation unit, 10. Inspection device, 12(1) to 12(4) Light source.

Claims

1. An illumination unit configured to irradiate light from multiple directions toward the sprue cup of the sand mold, A shooting unit that generates multiple brightness images by photographing the sprue cup of the sand mold when the aforementioned light is irradiated from each direction, An image generation unit generates a single inspection image by combining the aforementioned multiple brightness images, A sand mold inspection apparatus comprising: an image processing unit that inspects for abnormalities in the sprue cup of a sand mold by processing the inspection image according to the location of the sprue cup of the sand mold.

2. The sand mold inspection apparatus according to claim 1, wherein the image generation unit generates the inspection image corresponding to the shape or reflectance of the surface of the spout cup by synthesizing the plurality of luminance images using a photometric stereo method.

3. The spout cup has a bottom portion, The sand mold inspection apparatus according to claim 1 or 2, wherein the image processing unit determines that a foreign object is present in the bottom portion of the inspection image when there is a region having an area greater than or equal to a predetermined value in the bottom portion of the inspection image.

4. The aforementioned spout cup has a water return, The sand mold inspection apparatus according to claim 1 or 2, wherein the image processing unit determines that a foreign object is present in the return portion of the inspection image when there is a region having an area greater than or equal to a predetermined value in the return portion of the inspection image.

5. The aforementioned spout cup has a water return, The sand mold inspection apparatus according to claim 1 or 2, wherein the image processing unit detects the inner and outer contours of the scalding surface, and detects an abnormality in the shape of the scalding surface based on the shapes of the outer and inner contours.

6. The horizontal cross-section of the spout cup has the shape of a rounded rectangle consisting of a first semicircle, a rectangle, and a second semicircle, and the first semicircle constitutes a part of the spout return. The first region of the hot water return area consists of a region between a first line segment connecting the center of the first semicircle and the rightmost point of the first semicircle located to the right of the center of the first semicircle, and a second line segment obtained by rotating the first line segment counterclockwise by 45 degrees, and a region between a third line segment obtained by rotating the first line segment counterclockwise by 135 degrees and a fourth line segment obtained by rotating the first line segment counterclockwise by 180 degrees. The image processing unit determines the minimum distance from the center of the first semicircle to the inner contour of the first region of the scalding water, and the maximum distance from the center of the first semicircle to the outer contour of the first region of the scalding water. The sand mold inspection apparatus according to claim 5, wherein if the minimum value is less than a first threshold, or the maximum value is greater than a second threshold, it is determined that the shape of the first region of the molten metal is abnormal.

7. Of the aforementioned hot water return region, the region between the second line segment and the third line segment is defined as the second region. The image processing unit determines the minimum distance from the center of the first semicircle to the inner contour of the second region of the water return, and the maximum distance from the center of the first semicircle to the outer contour of the second region of the water return. The sand mold inspection apparatus according to claim 6, wherein if the minimum value is less than the first threshold or the maximum value is greater than the third threshold, it is determined that the shape of the second region of the molten metal is abnormal, and the third threshold is smaller than the second threshold.

Images