INSPECTION APPARATUS FOR WELDING TIP OF SPOT WELDING GUN AND ANALYSIS METHOD FOR POLLUTION AND ARRAY OF WELDING TIP USING THE SAME

• US 20160171681A1
• Filed: 08/20/2015
• Published: 06/16/2016
• Est. Priority Date: 12/01/2014
• Status: Active Grant

• Current Assignee: Autoit Co., Ltd.
• Original Assignee: Autoit Co., Ltd.
• Inventors: JEONG, Myung Hwan
• Granted Patent: US 10,055,835 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B23K 11/3063 Electrode maintenance, e.g. cleaning, grinding
• CPC Class Codes: G06T 2207/30136 Metal
• CPC Class Codes: G06T 2207/30164 Workpiece; Machine component
• CPC Class Codes: G06T 7/001 using an image reference approach
• CPC Class Codes: G06T 7/64 of convexity or concavity

Abstract

The present invention discloses methods and apparatus for increasing inspection efficiency and reducing time for analyzing an image when inspecting contamination and alignment of the welding tip of the spot welding gun. An apparatus for inspecting a welding tip according to some embodiments of the present invention is configured to inspect the contamination and the alignment of the welding tip based on an end-surface image and a profile image of the welding tip. In particular, when recording the welding tip through an internal housing arranged in an internal space of an external housing, the noise generated from an external light source can be blocked, and hence the contamination and the alignment of the welding tip can be inspected by using a clearer image, thus improving the accuracy of the inspection.

Claims

1. An apparatus for inspecting a welding tip of a spot welding gun, the apparatus comprising:

an external housing including

an internal space therein, and

an external inlet configured to allow each of a pair of welding tips facing each other to be inserted into the internal space;

an internal housing arranged in the internal space of the external housing and including

a first internal inlet formed on a first side of opposing sides facing each other and configured to allow a first welding tip of the pair of welding tips inserted from the external inlet on one side to be inserted,

a second internal inlet formed on a second side of the opposing sides and configured to allow a second welding tip of the pair of welding tips inserted from the external inlet on the other side to be inserted, and

a first monitoring hole and a second monitoring hole respectively arranged close to the first internal inlet and the second internal inlet,

a lighting unit configured to provide light to an inspection space defined by the internal housing;

a camera unit arranged on the external housing and configured to record the pair of welding tips inserted into the inspection space and to acquire images of the pair of welding tips; and

a control unit configured to receive the images of the pair of welding tips from the camera unit and to analyze a state of the welding tips by analyzing the images.

2. The apparatus according to claim 1, further comprising a light diffusing unit arranged being separated from an inner surface of the internal housing toward a center of the internal housing by a predetermined distance and configured to diffuse the light provided to the inspection space.

3. The apparatus according to claim 2, wherein the light diffusing unit includes translucent white glass material or synthetic resin material.

4. The apparatus according to claim 1, wherein the lighting unit includes a light source including a plurality of light emitting diodes.

5. The apparatus according to claim 1, wherein the lighting unit includes

a light source, and

at least one optical fiber including a first facet coupled to the light source and a second facet arranged toward the inspection space.

6. The apparatus according to claim 1, wherein

the internal housing includes a pair of half bodies formed in a symmetric manner with each other,

each of the half bodies includes an opened side,

the opened sides of the half bodies are configured to be engaged with each other to define the inspection space, and

the half bodies are configured to outwardly rotate with respect to a predetermined point where the half bodies are brought into contact with each other, to open the inspection space.

7. The apparatus according to claim 6, further comprising a light diffusing unit including symmetric members, arranged being separated from an inner surface of the internal housing toward a center of the internal housing by a predetermined distance and when the half bodies are engaged with each other, configured to define the inspection space connected to the internal inlets and the monitoring holes and to diffuse the light provided to the inspection space.

8. The apparatus according to claim 6, further comprising:

a support frame arranged on an outer side of the internal housing;

a pair of rotation-force providing units arranged on respective sides of the support frame facing each other; and

a pair of opening and closing units coupled between the respective rotation-force providing units and the respective half bodies, and configured to receive rotation forces from the respective rotation-force providing units, to rotate the respective half bodies, and to open and close the internal housing.

9. The apparatus according to claim 8, wherein

the support frame includes

a pair of support plates arranged on respective sides of the internal housing in a manner that the support plates facing each other, and each including guide holes formed in a symmetric manner on an outer side, the guide holes engaged with the respective half bodies and formed in an inwardly curved manner,

a plurality of connecting bars configured to connect the support plates, and

at least one guide bar vertically arranged between the connecting bars, and

the opening and closing unit includes

a vertical moving bar including a first side movably connected to the guide bar,

a vertical moving-force providing bar including a first end connected to the rotation-force providing unit and a second end coupled to a second side of the vertical moving bar in a screwed manner to move up and down the vertical moving bar with rotation of the rotation-force providing unit, and

a pair of opening and closing bars each including a first end rotatably connected to the vertical moving-force providing bar and a second end connected to one side of each of the half bodies through the guide hole, and when the vertical moving bar moves up and down, moving along the guide hole to rotate each of the half bodies, thus opening and closing the internal housing.

10. The apparatus according to claim 8, further comprising:

an upper sensor arranged at a closing position of the opening and closing unit where the internal housing is closed and configured to be short-circuited by the opening and closing unit to cut off a current with which the opening and closing unit rotates the rotation-force providing unit in a direction of closing the internal housing, and

a lower sensor arranged at an opening position of the opening and closing unit where the internal housing is opened and configured to be short-circuited by the opening and closing unit to cut off a current with which the opening and closing unit rotates the rotation-force providing unit in a direction of opening the internal housing.

11. The apparatus according to claim 1, wherein

the camera unit includes

a first end-surface recording camera arranged at a position close to a second end of the external inlet with a recording direction set to record an end surface of the first welding tip through the first monitoring hole, and

a second end-surface recording camera arranged at a position close to a first end of the external inlet with a recording direction set to record an end surface of the second welding tip through the second monitoring hole, and

the control unit is configured to analyze a contamination level of the welding tip based on images of end surfaces of the welding tips received from the first end-surface recording camera and the second end-surface recording camera.

12. The apparatus according to claim 1, wherein

the camera unit includes

a first alignment inspection camera arranged on the external housing and configured to acquire a first profile image of the pair of the welding tips, and

a second alignment inspection camera arranged on the external housing and configured to acquire a second profile image of the pair of welding tips, and

the control unit is configured to analyze the alignment of the welding tips based on the profile images of the pair of welding tips received from the first alignment inspection camera and the second alignment inspection camera.

13. The apparatus according to claim 12, wherein

the internal housing includes a pair of half bodies formed in a symmetric manner with each other, each of the half bodies including an opened side, the opened sides of the half bodies configured to be engaged with each other to define the inspection space, the half bodies configured to outwardly rotate with respect to a predetermined point where the half bodies are brought into contact with each other, to open the inspection space,

the apparatus further comprises a light diffusing unit including symmetric members, arranged being separated from an inner surface of the internal housing toward a center of the internal housing by a predetermined distance and when the half bodies are engaged with each other, configured to define the inspection space connected to the internal inlets and the monitoring holes and to diffuse the light provided to the inspection space, and

the first alignment inspection camera and the second alignment inspection camera are configured to record profile images of the pair of welding tips with the light diffusing unit on a background in a state in which the pair of half bodies rotate outwardly to open the inspection space.

14. The apparatus according to claim 12, wherein the first alignment inspection camera and the second alignment inspection camera are arranged with recording directions thereof perpendicular to each other.

15. The apparatus according to claim 1, further comprising a welding-force detecting unit arranged on one side of the external housing and configured to be electrically connected to the control unit and to detect a welding force generated by pressing of the pair of welding tips.

16. The apparatus according to claim 1, further comprising a current detecting unit arranged on one side of the external housing and configured to be electrically connected to the control unit and to detect amount of a current from a magnetic field generated from the pair of welding tips.

17. A method of analyzing contamination of a welding tip of a spot welding gun based on an image of a distal end of the welding tip by using a welding-tip inspecting apparatus including an external housing, an internal housing, a lighting unit, a camera unit, and a control unit, the method comprising, by the control unit:

(a) receiving a YCbCr image containing brightness information, blue information, and red information on a distal end of the welding tip;

(b) separating the YCbCr image into a Y image containing the brightness information, a Cb image containing the brightness information and the blue information, and a Cr image containing the brightness information and the red information;

(c) detecting a tip area by extracting an area corresponding to predetermined tip color information from the YCbCr image and specifying the tip area as a region-of-interest;

(d) detecting an end surface of the welding tip based on a difference in brightness between pixels in an area corresponding to the region-of-interest in the Y image; and

(e) measuring a contamination level of the end surface by comparing color information of each pixel in the end surface with predetermined reference color information.

18. The method according to claim 17, wherein the step (c) includes

a brightness filtering step of detecting a pixel out of a predetermined reference brightness range from the YCbCr image and excluding a detected pixel from the tip area,

a blue filtering step of detecting a pixel out of a predetermined reference blue range from the YCbCr image and excluding a detected pixel from the tip area,

a tip-area detecting step of detecting, as the tip area, an area corresponding to a reference red range from the YCbCr image on which the brightness filtering step and the blue filtering step have been performed,

a separating step of separating the tip area and the other area from the YCbCr image,

a specifying step of specifying an image corresponding to the tip area as a region-of-interest, and

a shape-information extracting step of extracting shape information of the region-of-interest.

19. The method according to claim 17, wherein the step (d) includes

an edge detecting step of detecting an edge of the welding tip based on a difference in brightness between pixels located in an area corresponding to the region-of-interest in the Y image, and

an ellipse detecting step of detecting an ellipse based on the detected edge information and the shape information of the tip area.

20. The method according to claim 19, wherein the step (d) further includes an end-surface determining step of detecting a plurality of ellipses in the ellipse detecting step and determining, as the end surface, an ellipse with a diameter of each detected ellipse and a height ratio of each detected tip area within a tolerance in comparing the height ratio of each detected tip area with a predetermined reference ratio.

21. The method according to claim 18, wherein the step (e) includes

a pixel counting step of counting a total number of pixels in an area corresponding to the end surface in an image of the tip area,

a contamination-pixel counting step of determining, as a contamination pixel, a pixel having color information different from a color of the tip area among pixels of an area corresponding to the end surface, and

a contamination-level measuring step of calculating a contamination ratio based on the pixels of the area corresponding to the end surface and the contamination pixel and measuring a contamination level of the welding tip based on a color information level of the contamination pixel calculated by comparing color information of the contamination pixel in the YCbCr image with predetermined color information.

22. A method of analyzing alignment of a welding tip of a spot welding gun based on a profile image of the welding tip by using a welding-tip inspecting apparatus including an external housing, an internal housing, a lighting unit, a camera unit, and a control unit, the method comprising, by the control unit:

(a) acquiring a first profile image and a second profile image of a pair of welding tips facing each other;

(b) removing noise from the first profile image and the second profile image;

(c) acquiring first profile binary data and second profile binary data by binarizing the first profile image and the second profile image based on a predetermined reference value;

(d) extracting edges of the pair of welding tips based on the first profile binary data and the second profile binary data; and

(e) inspecting the alignment of the pair of welding tips based on whether or not a pair of virtual lines extended from respective side edges of the welding tips match each other.

23. The method according to claim 22, wherein the step (e) includes

a step of extending a straight virtual line from a side edge of each welding tip among the extracted edges of the pair of welding tips in a direction to the opposing welding tip,

a step of determining whether or not the pair of virtual lines extended from the side edges of the respective welding tips,

a step of determining, when the pair of virtual lines extended from the side edges of the respective welding tips do not match each other, whether or not the pair of virtual lines are parallel to each other, and

a step of measuring a distance between the virtual lines when the virtual lines are parallel to each other and measuring an angle between the virtual lines when the virtual lines are not parallel to each other.

24. The method according to claim 22, further comprising (f) inspecting a zero point of the pair of welding tips by measuring a distance between centers of edges of the distal ends of the pair of welding tips and comparing a measured distance value with a predetermined reference value.