Grinding system, grinding method, and method for manufacturing steel product

Abstract

Provided is a grinding system capable of automatically grinding a part to be ground of a work material while suppressing interference between the work material and a grinding tool. The grinding system comprises: a shape measurement device that measures the three-dimensional shape and orientation of the work material; a detection device that detects the position and shape of the part to be ground present on the surface of the work material; a grinding device provided with a grinding tool for grinding the part to be ground; and a control device that generates a path for the grinding tool on the basis of the measured three-dimensional shape and orientation of the work material and the detected position and shape of the part to be ground, and controls the grinding device so that the grinding tool moves along the path. The control device sets an interference risk region on the basis of the measured three-dimensional shape and orientation of the work material, and sets a grinding condition when grinding in the interference risk region.

Description

Grinding system, grinding method, and method for manufacturing steel products

[0001] The present invention relates to a grinding system, and more particularly to a grinding system for grinding a target portion present on the surface of a steel product having a complex shape such as a structural steel, and also to a grinding method and a method for manufacturing a steel product.

[0002] When steel products such as shaped steel are manufactured, defects (flaws) may occur on the outer surface of the product, which requires grinding to remove the defects.

[0003] Removal of defects by grinding is generally performed manually using a grinding tool such as a grinder, because steel products as workpieces have various three-dimensional shapes depending on their applications, and the locations at which the defects occur also vary.

[0004] However, this grinding process is dangerous because it uses tools that rotate at high speeds, and it also presents problems in the working environment, exposing workers to dust and vibrations. Therefore, there is a demand for automation of the defect removal process by grinding.

[0005] For example, Patent Document 1 discloses a system in which defects present on the surface of a workpiece are automatically ground away by an arm robot.

[0006] International Publication No. 2022 / 079974

[0007] The system disclosed in Patent Document 1 automates grinding operations by controlling a grinding device based on measurement results from a shape measurement device and a flaw detection device. However, because the grinding trajectory is generated based on the location of defects on the surface to be ground, there is a risk of contact or collision between the grinding tool and surfaces not to be ground (hereinafter referred to as interference risk) when the workpiece has a complex shape, such as structural steel. If contact or collision occurs, the grinding wheel may break and scatter into the surrounding area. There is also a risk of damaging the workpiece or damaging the equipment.

[0008] In view of the above, the present invention aims to provide a grinding system and a grinding method that can automatically grind a target portion of a workpiece while suppressing interference between the workpiece and the grinding tool, and a method for manufacturing steel products using the grinding method.

[0009] The present invention has been made to solve the above problems, and the gist of the present invention is as follows.

[0010] 1. A grinding system comprising: a shape measuring device that measures the three-dimensional shape and orientation of a workpiece; a detection device that detects the position and shape of a portion to be ground that exists on the surface of the workpiece; a grinding device equipped with a grinding tool that grinds the portion to be ground; and a control device that generates a trajectory of the grinding tool for grinding the portion to be ground based on the three-dimensional shape and orientation of the workpiece measured by the shape measuring device and the position and shape of the portion to be ground detected by the detection device, and controls the grinding device so that the grinding tool moves along the trajectory, wherein the control device sets an interference risk area on the surface of the workpiece where there is a risk of interference between the grinding tool and the workpiece, based on the three-dimensional shape and orientation of the workpiece measured by the shape measuring device, and sets grinding conditions for grinding the interference risk area based on the three-dimensional shape and orientation of the workpiece.

[0011] 2. The grinding system according to claim 1, wherein the control device sets one or both of the attitude and feed direction of the grinding tool as the grinding conditions.

[0012] 3. The grinding system according to 1 or 2 above, wherein the control device divides the surface of the workpiece into a plurality of planes based on the three-dimensional shape and attitude of the workpiece measured by the shape measuring device, extracts an intersection line for each of the planes, and controls the attitude of the grinding tool so that the rotation axis of the grinding tool is inclined toward the intersection line when grinding the interference risk region.

[0013] 4. A grinding method comprising: a shape measuring step of measuring the three-dimensional shape and orientation of a workpiece using a shape measuring device; a detection step of detecting the position and shape of a portion to be ground that exists on the surface of the workpiece; and a grinding step of generating a trajectory for a grinding tool of a grinding device to move based on the measured three-dimensional shape and orientation of the workpiece and the detected position and shape of the portion to be ground, and moving the grinding tool along the trajectory to grind the portion to be ground, wherein in the grinding step, an interference risk area on the surface of the workpiece where there is a risk of interference between the grinding tool and the workpiece is set based on the three-dimensional shape and orientation of the workpiece measured by the shape measuring device, and grinding conditions for grinding the interference risk area are set based on the three-dimensional shape and orientation of the workpiece.

[0014] 5. A method for manufacturing a steel product, comprising grinding a portion to be ground on a surface of the steel product as the workpiece by the grinding method described in 4 above.

[0015] According to the present invention, it is possible to automatically grind the portion of the workpiece to be ground while suppressing interference between the workpiece and the grinding tool.

[0016] FIG. 1 is a schematic diagram showing an example of a grinding system of the present invention. FIG. 1 is a schematic diagram showing an example of defects present on the surface of a workpiece and markings indicating the defects. FIG. 2 is a schematic diagram showing an example of a method for dividing a surface from three-dimensional point cloud data. FIG. 3 is a schematic diagram showing the position of an intersection line. FIG. 4 is a schematic diagram showing an example of a method for determining the presence or absence of an interference risk in a workpiece other than an H-beam. FIG. 5 is a schematic diagram showing an example of a method for setting an interference risk area. FIG. 6 is a schematic diagram showing an example of an interference risk area. FIG. 7 is a schematic diagram showing an example of the structure of a grinder. FIG. 8 is a schematic diagram showing an example of the attitude of a grinding tool when grinding an interference risk area and a non-interference area. FIG. 9 is a schematic diagram showing the difference in the grindable range depending on the orientation of the grinding wheel. FIG. 10 is a schematic diagram showing an example of a grinding trajectory for a workpiece 1 having surfaces S1 to S3. FIG. 11 is a schematic diagram showing the difference in grinding area depending on the orientation of the grinding wheel. FIG.

[0017] Next, a method for carrying out the present invention will be specifically described. Note that the following description shows an example of a preferred embodiment of the present invention, and the present invention is not limited to the following description in any way.

[0018] [Grinding System] First, a grinding system according to one embodiment of the present invention will be described. The grinding system according to this embodiment can incorporate part or all of the features disclosed as embodiments of the grinding method described below.

[0019] The grinding system of the present invention is a grinding system that uses a grinding tool to grind a portion to be ground that exists on the surface of a workpiece, and is equipped with a shape measuring device, a detection device, a grinding device, and a control device.

[0020] (Work Material) The work material is not particularly limited and any material can be used. The material of the work material is not particularly limited and may be any material that can be ground. Examples of such materials include metal, ceramic, concrete, stone, and wood. The metal may be any metal, but typical examples include iron and steel.

[0021] In one embodiment of the present invention, the workpiece may be a steel product. The present invention is particularly suitable for steel products having complex shapes, such as structural steel. The structural steel may be, for example, at least one selected from the group consisting of an H-beam, a T-beam, an I-beam, an equal-leg angle steel, a channel steel, an unequal-leg angle steel, an unequal-leg and unequal-thickness angle steel, a spherical flat steel, and a steel sheet pile.

[0022] Next, a preferred example of a grinding system of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing an example of a grinding system of the present invention. The grinding system 100 of this embodiment is a system that grinds and removes a grinding target portion 2 present on the surface of a workpiece 1. The grinding system 100 includes a shape measuring device 10, a detection device 20, a grinding device 30, and a control device 40. Note that in this embodiment, the workpiece 1 will be described as an H-beam, but as mentioned above, the present invention can be applied to any workpiece other than an H-beam.

[0023] (Shape Measuring Device) In this embodiment, a three-dimensional shape measuring device is used as the shape measuring device 10 to measure the three-dimensional shape and orientation of the workpiece 1 (H-beam). As the three-dimensional shape measuring device, it is preferable to use a device that can acquire the three-dimensional shape of the workpiece 1 as three-dimensional point cloud data. Here, the three-dimensional point cloud data is a set of coordinate data of multiple points that indicate the surface positions of the workpiece 1.

[0024] Examples of the three-dimensional shape measuring device include a laser rangefinder and a 3D camera, among which a 3D camera is preferably used, since the use of a 3D camera makes it possible to obtain not only three-dimensional point cloud data but also color information at each point of the point cloud data.

[0025] The shape measuring device 10 preferably includes a moving means. By using the moving means, a wide range can be measured with a single shape measuring device. Furthermore, when a two-dimensional laser range finder is used as the shape measuring device 10, the three-dimensional shape of the workpiece 1 can be measured by performing measurements while moving the two-dimensional laser range finder using the moving means.

[0026] (Detection Device) The detection device 20 is a means for detecting the position and shape of the portion to be ground 2 present on the surface of the workpiece 1. In this embodiment, a data processing device is used as the detection device 20. By analyzing one or both of the three-dimensional shape and color information of the workpiece 1 obtained by the shape measuring device 10 with the data processing device, the position and shape of the portion to be ground 2 present on the surface of the workpiece 1 can be detected.

[0027] For example, when a 3D camera is used as the shape measuring device 10, it is preferable to detect the position and shape of the portion to be ground 2 present on the surface of the workpiece 1 by analyzing color information of the workpiece 1 obtained by the 3D camera with the data processing device. On the other hand, when a laser rangefinder is used as the shape measuring device 10, defects can also be detected based on the shape of irregularities and the like on the surface of the workpiece 1. Furthermore, when performing shape measurement with the laser rangefinder, an image of the workpiece 1 may be simultaneously acquired with a separately provided camera. In this way, the color information obtained by the camera can be analyzed with the data processing device to detect the position and shape of the portion to be ground 2 present on the surface of the workpiece 1.

[0028] In another embodiment of the present invention, the grinding target portion 2 can be detected by using markings that have been provided in advance. This method will be described below with reference to Figure 2. In the following description, directions in space will be indicated using the x-y-z coordinate system shown in Figure 2. Here, x is the longitudinal direction of the H-beam as the workpiece 1.

[0029] FIG. 2( a ) is a schematic diagram showing an example of a defect (2) to be ground that exists on the surface of an H-beam steel as the workpiece 1. As described above, in one embodiment of the present invention, defects can be directly detected by analyzing measurement results obtained using a camera, a laser rangefinder, or the like. Meanwhile, in another embodiment of the present invention, as shown in FIG. 2( b ), the position and shape of the portion 2 to be ground can be identified by detecting a marking 3 applied around the defect. The marking 3 may be applied prior to grinding using the grinding system of the present invention. For example, a preliminary inspection may be performed to identify the position and shape of the defect, and the defect may then be surrounded by a colored line based on the results. Any inspection, such as visual inspection or nondestructive inspection (NDI), may be used. In this case, the data processing device can detect the marking 3 by filtering and extracting color information of the marking 3 from the data measured by the shape measurement device 10. For example, the marking 3 can be detected by applying an RGB or HSV upper / lower limit filter.

[0030] The data processing device is not particularly limited and any device can be used as long as it can detect the position and shape of the grinding target portion 2. Typically, a computer can be used as the data processing device. The computer may be a commercially available general-purpose computer.

[0031] (Grinding Device) The grinding device 30 in this embodiment includes a grinding wheel 31 as a grinding tool, a grinder 32 for driving the grinding wheel 31, and an articulated robot 33. The grinder 32 is attached to the tip of the arm of the articulated robot 33 and can be moved to any position and angle by the articulated robot 33. Then, the grinding wheel 31 is pressed against the surface of the workpiece 1 by the articulated robot 33, and the grinding target portion 2 can be ground by rotating the grinding wheel 31 by the grinder 32.

[0032] In this embodiment, the articulated robot 33 is placed on a traveling carriage 35 that is guided by a traveling axis 34, and the traveling axis 34 is laid parallel to the longitudinal direction (X-axis direction) of the workpiece 1. By making the grinding device 30 movable in this way, it becomes possible to perform grinding over a wide range with one grinding device 30.

[0033] Although not shown, the shape measuring device 10 is also movable in the longitudinal direction of the workpiece 1 in the same manner as the grinding device 30 .

[0034] (Control Device) The control device 40 generates a trajectory of the grinding tool (grinding wheel 31) for grinding the portion to be ground 2, based on the three-dimensional shape and orientation of the workpiece 1 measured by the shape measuring device 10 and the position and shape of the portion to be ground 2 detected by the detection device 20. The control device 40 then controls the grinding device 30 so that the grinding tool moves along the trajectory. For example, the control device 40 can perform inverse kinematics calculations based on the position of the portion to be ground 2, and generate a motion trajectory of the articulated robot 33 that presses the grinding wheel 31 against the position of the portion to be ground.

[0035] At this time, the control device 40 sets an interference risk area on the surface of the workpiece 1 where there is a risk of interference between the grinding tool and the workpiece 1, based on the three-dimensional shape and orientation of the workpiece 1 measured by the shape measuring device 10. Then, the control device 40 sets grinding conditions for grinding the interference risk area based on the three-dimensional shape and orientation of the workpiece 1.

[0036] The grinding conditions can be set by any method. From the viewpoint of avoiding interference, it is preferable that the control device 40 sets one or both of the attitude and feed direction of the grinding tool as the grinding conditions.

[0037] It is more preferable that the control device 40 controls the grinding conditions as follows. First, the control device 40 divides the surface of the workpiece 1 into a plurality of planes based on the three-dimensional shape and orientation of the workpiece 1 measured by the shape measuring device 10, and extracts the intersection lines for each of the planes. Next, when grinding the interference risk area, the control device 40 controls the orientation of the grinding tool so that the rotation axis of the grinding tool is inclined toward the intersection lines. A specific implementation method will be described later.

[0038] 1, the articulated robot 33 preferably includes a grinding reaction force measuring device 36. By using the grinding reaction force measuring device 36, it is possible to measure the reaction force generated when the grinding wheel 31 is brought into contact with the surface of the workpiece 1. It is preferable that the control device 40 adjusts the position of the grinding wheel 31 so that the reaction force measured by the grinding reaction force measuring device 36 becomes a value suitable for grinding.

[0039] [Grinding Method] Next, a grinding method according to one embodiment of the present invention will be described. The grinding method of the present invention includes a shape measurement step, a detection step, and a grinding step. Preferred embodiments of each step will be described below with reference to the drawings. Note that matters not specifically mentioned can be the same as those in the embodiment of the grinding system described above.

[0040] (Shape Measuring Step) In the shape measuring step, the three-dimensional shape and orientation of the workpiece 1 are measured by the shape measuring device 10 .

[0041] (Detection Step) In the detection step, the detection device 20 is used to detect the position and shape of the grinding target portion 2 present on the surface of the workpiece 1. For the detection, the marking 3 may be used as described above. When the marking 3 is used, the marking step may be performed before the detection step. The marking step is preferably performed before the shape measurement step.

[0042] (Grinding process) In the grinding process, a trajectory along which the grinding wheel 31 acting as a grinding tool moves is generated based on the three-dimensional shape and posture of the workpiece 1 and the position and shape of the portion to be ground 2, and the grinding wheel 31 is moved along the trajectory to grind the portion to be ground 2.

[0043] This embodiment is characterized in that, in the grinding process, an interference risk area is set based on the three-dimensional shape and orientation of the workpiece 1 measured by the shape measuring device 10, and grinding conditions for grinding the interference risk area are set. The setting of the interference risk area and grinding conditions is not particularly limited, and can be performed by any method depending on the shape and dimensions of the workpiece 1 and grinding device 30.

[0044] From here, a preferred embodiment for setting the interference risk area and grinding conditions will be described with reference to the drawings. That is, in one embodiment of the present invention, the grinding process preferably includes the following steps: A "surface division step" for dividing the surface of the workpiece 1 into multiple faces based on the three-dimensional shape and orientation of the workpiece 1 measured by the shape measuring device 10; An "interference risk area setting step" for extracting the intersection lines of each face divided in the face division step and setting an interference risk area based on the face configuration and information about each face; and A "grinding condition setting step" for setting grinding conditions in the interference risk area.

[0045] (Surface Division Process) In order to determine whether there is a risk of interference between the grinding tool and the workpiece and to perform control based on that determination, it is preferable to use information about the faces that make up the surface of the workpiece 1. However, as described above, the data obtained by measuring the workpiece 1 with the shape measuring device 10 is usually three-dimensional point cloud data. Although the three-dimensional point cloud data represents the three-dimensional shape of the workpiece 1, it is merely a set of coordinate data for multiple points that indicate the surface positions of the workpiece 1, and does not include information about the faces that make up the surface of the workpiece 1. Therefore, in this embodiment, first, the faces that make up the surface of the workpiece 1 are identified, and the surface is divided into multiple faces.

[0046] An example of a method for dividing surfaces from three-dimensional point cloud data will be described with reference to FIG.

[0047] 3(a) is a schematic diagram showing the cross section of an H-shaped steel as the workpiece 1 in the Y-Z plane as viewed from the X-axis direction. In this embodiment, it is assumed that grinding of the workpiece 1 is performed in two stages, and an example will be described in which six faces (hereinafter simply referred to as "surfaces") indicated by thick lines in FIG. 3(a) out of the 12 faces that make up the surface of the workpiece 1 are divided into multiple faces. After grinding of the six faces is completed, the workpiece 1 is turned over and the remaining six faces are subjected to the same process, thereby grinding the entire surface of the workpiece 1.

[0048] First, the surface is divided according to the direction of the normal at each point of the 3D point cloud data. In this example, the surface can be divided into three types: surfaces whose normals point in the positive direction of the Y axis (Sy+), surfaces whose normals point in the negative direction of the Y axis (Sy-), and surfaces whose normals point in the positive direction of the Z axis (Sz+).

[0049] Next, as shown in FIG. 3C, the point cloud constituting the plane (Sy+) whose normal is in the positive direction of the Y axis is divided into multiple parts based on the position in the Y axis direction. Specifically, the Y coordinate of each point and the threshold Y ｔｈｒ In this example, the surface (Sy+) whose normal is in the positive direction of the Y axis is divided based on the magnitude relationship between the threshold Y ｔｈｒ The surface is divided into two surfaces: one with a smaller Y coordinate than (Sy+-) and one with a larger Y coordinate than (Sy++).

[0050] Similarly, the point group constituting the plane (Sz+) whose normal is in the positive direction of the Z axis is also divided into multiple parts based on the position in the Z axis direction. Specifically, the Z coordinate of each point and the threshold Z ｔｈｒ In this example, the surface (Sz+) whose normal is in the positive direction of the Z axis is divided based on the magnitude relationship between the threshold Z ｔｈｒ The surface is divided into two surfaces: a surface with a larger Z coordinate (Sz++) and a surface with a smaller Z coordinate (Sz+-).

[0051] Furthermore, the threshold Z ｔｈｒ For points that make up a surface with a Z coordinate greater than , the Y coordinate of each point and the threshold Y ｔｈｒ Based on the magnitude relationship with ｔｈｒ The surface is divided into two surfaces: one with a smaller Y coordinate than (Sz++-) and one with a larger Y coordinate than (Sz+++).

[0052] In this way, by combining the identification of faces based on the normal direction and the division using a threshold, the surface can be divided into six faces S1 to S6 as shown in Fig. 3(d). In other words, the point clouds that make up each of the six faces S1 to S6 can be identified from the three-dimensional point cloud data that makes up the surface.

[0053] (Interference Risk Area Setting Process) Next, the intersection lines of each surface divided in the surface division process are extracted, and an interference risk area is set based on the surface configuration and information about each surface. When grinding is performed while the workpiece 1 is placed on a floor, pedestal, or the like, there is a possibility that the grinding tool will interfere with the floor or pedestal. Therefore, it is preferable that the interference risk area setting process also take into account the surface of the floor or pedestal that comes into contact with the workpiece 1 (hereinafter collectively referred to as the floor surface). In this case, the floor surface is also taken into consideration in all processes of the present invention. For example, it is preferable that the shape measurement process acquires three-dimensional point cloud data that includes the floor surface. Furthermore, it is preferable that the surface division process also includes the floor surface as a target for surface division.

[0054] 4 is a schematic diagram showing the positions of the intersection lines. In this example, six intersection lines L1 to L6 are extracted for a combination of two adjacent surfaces from among surfaces S1 to S6 and floor surface F. Note that the intersection lines L1 to L6 are all parallel to the X-axis, and are therefore shown as points in the figure.

[0055] Next, for each intersection line, the presence or absence of an interference risk is determined according to the information on each face and the face configuration of the workpiece 1. The method for evaluating the interference risk is not particularly limited, but for example, the presence or absence of an interference risk can be determined based on the direction in which the faces at the intersection line meet. Specifically, if the direction in which the faces at the intersection line meet is an "opening direction," it can be determined that there is no interference risk, and if it is a "closing direction," it can be determined that there is an interference risk.

[0056] In other words, the presence or absence of an interference risk can be determined based on the cross product vector of the normals of each adjacent face at the intersection line (this is referred to as the intersection line vector). For example, as shown in Figures 3 and 4, if a coordinate system is set so that the longitudinal direction of the workpiece 1 is the X-axis and the cross section is the Y-Z plane, if the X component of the intersection line vector is less than 0, it is determined that there is an interference risk between the adjacent faces. Conversely, if the X component of the intersection line vector is 0 or greater, it is determined that there is no interference risk between the adjacent faces.

[0057] According to the above determination method, of the intersection lines L1 to L6 shown in FIG. 4, only the intersection lines L1, L4, and L5 have an interference risk, and it can be determined that there is no interference risk for the remaining three.

[0058] The above-mentioned determination method can also be applied to workpieces other than H-shaped steel. For example, when the back surface of a steel sheet pile is to be ground as shown in Figure 5(a), of the intersection lines L1 to L4, only two, L2 and L3, have an interference risk, and it can be determined that there is no interference risk for the remaining two. Also, when an angle steel with unequal legs and thickness is to be ground as shown in Figure 5(b), of the intersection lines L1 to L3, only two, L1 and L3, have an interference risk, and it can be determined that there is no interference risk for the remaining one.

[0059] Next, an interference risk area is set based on the above-mentioned determination result. Although the method for setting the interference risk area is not particularly limited, it is preferable to set the interference risk area as a predetermined range from the intersection line determined to have an interference risk on the surface of the workpiece 1.

[0060] FIG. 6 is a schematic diagram showing an example of a method for setting an interference risk area, and in this diagram, the periphery of the intersection line L5 shown in FIG. 4 is shown enlarged. This intersection line L5 is the intersection line that has been determined to have an interference risk, as described above. Therefore, of the surfaces S4 and S5 tangent to the intersection line L5, the ranges of a distance Lr from the intersection line L5 are set as interference risk areas S4r and S5r. In the diagram, the interference risk areas are indicated by dashed lines. Note that the portions of the surfaces S4 and S5 other than the interference risk areas can be considered as areas with no interference risk (non-interference areas).

[0061] Here, it is preferable to determine the value of the distance Lr in advance, taking into consideration the shape of the workpiece 1, the dimensions and shape of the tool to be used, etc. The value of the distance Lr can be determined independently for each surface, but may also be the same for each surface.

[0062] By setting the interference risk areas for the intersection lines L1 and L4 in the same manner, it is possible to set the interference risk area (Sr) over the entire surface as shown in FIG.

[0063] (Grinding Condition Setting Step) In the next grinding condition setting step, grinding conditions for grinding the interference risk region are set based on the three-dimensional shape and posture of the workpiece. In other words, when setting the grinding conditions, the grinding conditions for each position are set based on whether the grinding location is an interference risk region or not.

[0064] FIG. 8 is a schematic diagram showing the structure of a typical grinder 32. A drive unit 32b is located at the tip of a main body 32a of the grinder 32. A grinding wheel 31 is attached to the drive unit 32b so that it can rotate around a rotation axis indicated by a chain line. A portion of the grinding wheel 31 is covered with a cover 32c to prevent dust and other particles from scattering. When setting grinding conditions, the structure of the grinding tool is taken into consideration and grinding conditions are set to avoid interference. While this embodiment uses a grinder and a rotating grinding wheel as an example, when using other types of grinding devices, such as a belt-type grinding device, the conditions can be set according to the structure of the device.

[0065] 9 is a schematic diagram showing an example of the posture of the grinding tool when grinding the interference risk region and the non-interference region. When grinding the interference risk region, the posture is controlled so that the rotation axis R of the grinding wheel 31 (grinding tool) is tilted toward the intersection line L, as shown in FIG. 9( a). In this case, it is preferable to tilt the grinding wheel 31 toward the intersection line L so that the rotation axis R of the grinding wheel 31 is at a certain angle (for example, 10 to 20°) with respect to the normal line N of the grinding surface in the y-z plane.

[0066] FIG. 10 is a schematic diagram showing the difference in the grindable range depending on the orientation of the grinding wheel. When grinding using a grinding wheel 31, the tip 31a of the grinding wheel 31 is typically pressed against the workpiece 1. However, the grinding wheel 31 has a predetermined radius, and a portion of the grinding wheel 31 is covered by a cover 32c. Therefore, as shown in FIG. 10(a), if the tip of the grinding wheel 31 does not face the direction of the intersection line L, the side of the grinding wheel 31 interferes with the workpiece 1 on the left side, making it impossible to grind the area indicated by the arrow (near the intersection line L). On the other hand, as shown in FIG. 10(b), if the tip of the grinding wheel 31 faces the direction of the intersection line L, grinding can be performed up to the vicinity of the intersection line L without interference. Therefore, when grinding an interference risk area, it is preferable to face the tip 31a of the grinding wheel 31 toward the intersection line.

[0067] In this way, by orienting the grinding wheel 31 toward the line of intersection and tilting the grinding wheel 31 toward the line of intersection, interference between the grinding wheel 31 (and the grinder 32) and the workpiece 1 can be suppressed compared to when the grinding wheel 31 faces in another direction and is not tilted toward the line of intersection. The feed direction, speed, pressing force, etc. of the grinding wheel 31 can also be adjusted according to the attitude of the grinding wheel 31.

[0068] When grinding areas other than the interference risk area (non-interference area), there are no restrictions on the grinding conditions of the grinding wheel 31, so the most efficient grinding conditions can be set. For example, when grinding by feeding the grinding wheel 31 along the longitudinal direction (x direction) of the workpiece 1, as shown in Figure 9(b), the grinding wheel 31 is oriented so that its rotation axis is oriented in the same direction as the normal to the grinding surface when viewed in the y-z plane in the non-interference area (the grinding wheel 31 is oriented in the longitudinal direction of the workpiece 1). This increases the contact area between the workpiece 1 and the grinding wheel 31, improving grinding efficiency.

[0069] (Method of Generating Grinding Locus) Next, a method of generating a grinding locus in the grinding process, that is, a method of setting the tip position of the grinding wheel 31, will be described.

[0070] 11 is a schematic diagram showing an example of a grinding path in a workpiece 1 having surfaces S1 to S3. In this example, the area indicated by marking 3 is the part to be ground.

[0071] If the entire part to be ground indicated by marking 3 is within the interference risk area, machining points are set under machining conditions suitable for the interference risk area. Also, if the entire part to be ground indicated by marking 3 is within the non-interference area, machining points are set under machining conditions suitable for the non-interference area. On the other hand, as shown in Figure 11, if part of the part to be ground is within the interference risk area and the remaining part is within the non-interference area, machining points can be set under machining conditions suitable for each area. The connection of the set machining points then forms the grinding trajectory.

[0072] 11, the area of ​​the surfaces of the faces S1 and S2 within a distance Lr from the intersection line L is the interference risk area, and the remaining area is the non-interference area. Machining points within the interference risk area are indicated by black circles, and machining points within the non-interference area are indicated by white circles.

[0073] When setting the processing points, it is preferable to perform coordinate transformation for calculation. Therefore, the coordinate transformation method will be explained. Here, the average value of the x, y, and z coordinates of each surface is set as the representative point coordinate p ０ = (x ０ , y ０ , z ０ ), the normal vector formed by each surface is the representative vector n ０ = (n ｘ０ , n ｙ０ , n ｚ０ ) is defined as

[0074] To perform coordinate transformation, first calculate the translation component t using the following equation (1):

[0075] Next, to calculate the rotational components, the z-axis of the calculation coordinate system and the representative vector n ０ Specifically, first, the z-axis direction is rotated so that the vectors n ０ｚ (0,0,1) and the representative vector n of the surface ０ From the inner product of the above, the rotation angle θ is calculated using the following equation (2).

[0076] Next, as shown in the following formula (3), n ０ and ０ｚ The rotation axis vector n = (nx, ny, nz) is calculated from the cross product.

[0077] From the obtained rotation angle θ and rotation axis vector n, the rotation component R is calculated using the Rodrigues rotation formula shown in the following equation (4). θ Ask for.

[0078] Finally, the simultaneous transformation matrix T for transforming the coordinates of the surface into the calculation coordinate system is shown in Equation (5). Coordinate transformation is performed by multiplying the coordinate values ​​of the surface by this simultaneous transformation matrix.

[0079] The machining points P are arranged according to the marking positions after coordinate transformation and the machining parameters in each region, and the points are connected to generate a grinding trajectory. By operating the articulated robot according to the generated trajectory, automatic grinding can be performed while avoiding interference between the workpiece 1 and the grinding wheel 31.

[0080] Furthermore, when determining the grinding path, it is desirable to take into consideration the difference in the grinding area depending on the direction of the grinding wheel. The reason for this is as follows.

[0081] Figure 12 is a schematic diagram showing the difference in grinding area depending on the direction of the grinding wheel. In this figure, it is assumed that grinding is performed while the grinding wheel is moved in a direction perpendicular to the paper surface, that is, from the front to the back of the paper. This direction of grinding wheel movement is called the feed direction.

[0082] 12(a) shows a case where the tip 31a of the grinding wheel is oriented in a direction perpendicular to the feed direction, in other words, where the direction of the grinding wheel and the feed direction are perpendicular to each other. Here, the direction of the grinding wheel is the direction of an imaginary line connecting the tip 31a of the grinding wheel and the center of rotation of the grinding wheel. In this case, the length of the part of the grinding wheel where the tip comes into contact with the workpiece 1 in the y-axis direction is short, as shown by the arrow. Therefore, even if the grinding wheel is moved in this state to perform grinding, the grinding area per pass is small.

[0083] 12(b) shows the case where the tip 31a of the grinding wheel is oriented parallel to the feed direction, in other words, the direction of the grinding wheel is parallel to the feed direction. In this case, the length of the portion of the grinding wheel where the tip comes into contact with the workpiece 1 in the y-axis direction is long, as shown by the arrow. Therefore, if the grinding wheel is moved in this state to perform grinding, the grinding area per pass can be increased, and grinding efficiency can be improved.

[0084] For the above reasons, when there is no need to consider the risk of interference, it is preferable that the direction of the grinding wheel and the feed direction are parallel, as shown in Fig. 12(b). However, when there is a risk of interference as explained in Fig. 10, it is preferable that the direction of the grinding wheel be perpendicular to the feed direction, as shown in Fig. 12(a).

[0085] An example of a grinding trajectory determined in consideration of the above points is shown in Fig. 13. Here, the portion to be ground defined by marking 3 is a rectangle with a length in the x-axis direction of ML and a length in the y-axis direction of MBr + MBp. MBr is the length in the interference risk region, and MBp is the length in the non-interference region.

[0086] In such a case, there are two possible grinding trajectories: a pattern in which the path direction is parallel to the x-axis as shown in FIG. 13(a), and a pattern in which the path direction is perpendicular to the x-axis as shown in FIG. 13(b).

[0087] In the non-interference region, since no contact occurs as shown in Fig. 10(a), it is preferable that the grinding wheel direction and the feed direction are parallel, as shown in Fig. 12(b). Therefore, in order to shorten the time required for grinding, it is preferable to set the trajectory so that the grinding wheel direction and the feed direction are parallel and the number of passes is reduced. That is, if ML > MBp, it is preferable to set a pass parallel to the x-axis, and if ML < MBp, it is preferable to set a pass parallel to the y-axis.

[0088] On the other hand, in the interference risk region, in order to avoid the contact shown in Fig. 10(a), it is preferable to orient the grinding wheel perpendicular to the feed direction as shown in Fig. 10(b). Note that the interference risk region is usually a limited region near the intersection line L, and therefore is narrow, with ML > MBr in most cases.

[0089] 13(a) and 13(b) based on the above assumptions, it can be seen that the pattern in Fig. 13(a) has higher grinding efficiency. This is because the pattern in Fig. 13(a) has a smaller area per pass and a longer total grinding distance, but the number of passes is smaller, resulting in less turn time between passes. In contrast, the pattern in Fig. 13(b) has a larger grinding area per pass and a shorter total grinding distance, but the number of passes is larger, resulting in more turn time between passes.

[0090] Therefore, as shown in FIG. 13( a), by setting a trajectory so that grinding is performed while moving the grinding tool in a direction parallel to the intersection line L, the search time can be shortened and grinding can be performed more efficiently.

[0091] As described above, according to the present invention, it is possible to automatically grind the portion of a workpiece to be ground while suppressing interference between the workpiece and the grinding tool. The method of the present invention can be applied to various workpieces, but is particularly suitable for steel products. Therefore, in one embodiment of the present invention, a steel product can be manufactured by grinding the portion to be ground on the surface of a steel product as a workpiece using the grinding method described above.

[0092] REFERENCE SIGNS LIST 1 Workpiece 2 Grinding target part 3 Marking 10 Shape measuring device 20 Detection device 30 Grinding device 31 Grinding wheel 31a Grinding wheel tip 32 Grinder 32a Main body 32b Drive unit 32c Cover 33 Articulated robot 34 Traveling axis 35 Traveling carriage 36 Grinding reaction force measuring device 40 Control device 100 Grinding system L Intersection line S Surface P Processing point R Rotation axis F Floor surface

Claims

1. A grinding system comprising: a shape measuring device that measures the three-dimensional shape and orientation of a workpiece; a detection device that detects the position and shape of a portion to be ground that exists on the surface of the workpiece; a grinding device equipped with a grinding tool that grinds the portion to be ground; and a control device that generates a trajectory of the grinding tool for grinding the portion to be ground based on the three-dimensional shape and orientation of the workpiece measured by the shape measuring device and the position and shape of the portion to be ground detected by the detection device, and controls the grinding device so that the grinding tool moves along the trajectory, wherein the control device sets an interference risk area on the surface of the workpiece where there is a risk of interference between the grinding tool and the workpiece, based on the three-dimensional shape and orientation of the workpiece measured by the shape measuring device, and sets grinding conditions for grinding the interference risk area based on the three-dimensional shape and orientation of the workpiece.

2. The grinding system according to claim 1, wherein the control device sets one or both of the attitude and feed direction of the grinding tool as the grinding conditions.

3. A grinding system as described in claim 1 or 2, wherein the control device divides the surface of the workpiece into a plurality of faces based on the three-dimensional shape and attitude of the workpiece measured by the shape measuring device, extracts the intersection line for each face, and controls the attitude of the grinding tool so that the rotation axis of the grinding tool is tilted toward the intersection line when grinding the interference risk area.

4. A grinding method comprising: a shape measuring step of measuring the three-dimensional shape and orientation of a workpiece using a shape measuring device; a detection step of detecting the position and shape of a portion to be ground that exists on the surface of the workpiece; and a grinding step of generating a trajectory for a grinding tool of a grinding device to move based on the measured three-dimensional shape and orientation of the workpiece and the detected position and shape of the portion to be ground, and moving the grinding tool along the trajectory to grind the portion to be ground, wherein in the grinding step, an interference risk area on the surface of the workpiece where there is a risk of interference between the grinding tool and the workpiece is set based on the three-dimensional shape and orientation of the workpiece measured by the shape measuring device, and grinding conditions for grinding the interference risk area are set based on the three-dimensional shape and orientation of the workpiece.

5. A method for manufacturing a steel product, in which the grinding target portion on the surface of the steel product as the workpiece is ground by the grinding method described in claim 4.

Images