JP2010234430A - Method of cutting runner for casting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for successfully cutting a runner, even in the case of a casting with a product part having complicated shapes and a number of curved faces with unclear contours, and even in the case that position and posture relative to the product part are varied. <P>SOLUTION: The method cuts the runner of a workpiece as a casting in which one or more product parts after mold release are linked with programmed sections, while a cutting torch is position-controlled by a robot system of a teaching reproduction type. In the reproduction step, for the actual target workpiece to be cut set in a prescribed tool, points on the actual workpiece corresponding to a plurality of specified points selected on the product parts of a teaching workpiece are measured with a three-dimensional visual sensor which is positioned at the same position and posture as during the teaching step. On the basis of the three-dimensional coordinate values, a product coordinate system is defined for each product part. On the basis of deviation between the product part coordinate system of the teaching workpiece and that of the actual workpiece, the teaching data of the torch are corrected and, on the basis of the corrected teaching data, the robot is position-controlled. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for cutting a runner or a feeder part of a cast product by moving a plasma torch or the like attached to a robot.

  The mold is provided with a sprue, runner, weir, feeder, etc. based on the casting plan, and the cast product after mold separation is connected to the product part and the plan part (poor, feeder, runner, etc.) In the process of commercialization, it is necessary to separate the product part and the plan part. The separation operation is usually performed by cutting runners and weirs (collectively referred to as runner cuts). As a method of cutting the runner, various methods such as a press method, a grindstone cutting method, a thermal cutting method such as gas or plasma, etc. are taken according to the material, shape, size, quantity, etc. of the casting (product part). However, in many cases, a method using a robot equipped with a thermal cutting torch is used for a material that is difficult to break, a complex shape product, or a curved cut product. In order to perform runner cutting with a robot, a method is adopted in which a torch is taught to pass through a predetermined path near the product part and a regenerating operation is performed. However, positioning accuracy of the cast product is poor or distortion occurs. When the torch is positioned according to the teaching data, there is a problem that the runner cannot be cut well.

  In order to solve the above problem, it is conceivable to correct the teaching data in accordance with the position and orientation of the actual casting to be cut. For example, Patent Literature 1 discloses a technique for this purpose. The technique of Patent Document 1 relates to a robot control method for correcting the position and posture of already created teaching data when processing operations such as arc welding and spot welding are realized by a robot. That is, when the workpiece to be machined is set at the reference position, a user coordinate system in which the origin and the axial direction of the Cartesian coordinate system are desired values is defined by specifying a plurality of feature points on the workpiece. A base coordinate system (also referred to as a robot coordinate system) which is a Cartesian coordinate unique to a robot individual, in which the robot is moved according to the axial direction of the user coordinate system to teach a work route, and the position and orientation data of the teaching point on this work route In the control method of an industrial robot that performs motion control by calculating each joint angle data of the robot based on the base coordinate value data at the time of reproduction, The position and orientation data is stored as user coordinate value data based on the user coordinate system, and based on the user coordinate value data and the user coordinate system at the time of reproduction. Base coordinate value data is calculated, each joint angle data of the robot is calculated based on the base coordinate value data, and when the workpiece is placed at a position different from the reference position, the positions of the plurality of feature points And redefine the user coordinate system, re-calculate the base coordinate value data based on the user coordinate value data and the redefined user coordinate system at the time of reproduction, and recalculate the base coordinates It is characterized in that each joint data of the robot is calculated based on the value data. It is also disclosed that a robot automatically performs redefinition of a user coordinate system by measuring re-designation of the positions of the plurality of feature points with a position measuring device.

JP 2007-1115011 A

In recent years, casting products used for automobile parts have been manufactured with high heat resistance, thin walls, and complicated shapes, for example, due to demands for pollution prevention and weight reduction. In general, in the runner cutting operation, in order to accurately position an integral cast product (corresponding to the workpiece of Patent Document 1 described above) in which the product portion and the design portion after mold breaking are connected, it is called the workpiece. A dedicated positioning jig is required for each product type. However, the workpiece is likely to be distorted in the runner, and in such a case, it is difficult to accurately position even if a jig is used, and good runner cutting cannot be performed if the position or posture varies greatly. To solve this problem, the technique disclosed in Patent Document 1 is effective, but in order to define a user coordinate system, a plurality of feature points (uniquely defined points) are used (refer to Patent Document 1). In the first embodiment, three points) must be specified. However, in the workpiece, feature points are specified on a product part that is less deformed or distorted than the plan part, but the product part has many curved surfaces with complicated shapes and unclear outlines, and the feature points are 3 Those that also have dots are rare. Therefore, the technique of Patent Document 1 can hardly cope with a so-called single-piece workpiece in which one product part is arranged in one mold. However, even if the product part has only one feature point, if the work has three or more product parts, the work has three or more feature points. Can be defined. However, in this case, if the relative position or posture between product parts in the workpiece fluctuates due to distortion of the runner or the like, the mutual positional relationship of the feature points changes, and the user coordinate system can be redefined with high accuracy. There is a problem that it is difficult to cut the runner well.
Therefore, the present invention is excellent even in a cast product having a product part with many curved surfaces with complicated shapes and unclear outlines, and even when the position and posture between product parts are fluctuating. It aims at providing the method which can cut | run a runner.

The present invention controls the position of a cutting torch by a teaching reproduction type robot system, and cuts a runner of a workpiece which is a cast product in which one or a plurality of product parts are connected by a design part after mold separation. In the way to
In the teaching process, for the teaching work set on the specified tool,
1) A plurality of designated points selected on the product part are measured with a three-dimensional visual sensor attached to the robot, and a product coordinate system for each product part is defined based on those three-dimensional coordinate values.
2) Teach the movement path of the torch for cutting the runner of the product part and store the teaching data in the product coordinate system;
In the regeneration process, for the actual workpiece to be cut set on the specified tool,
3) The points on the actual workpiece corresponding to the plurality of designated points selected on the product part of the teaching workpiece are measured with a three-dimensional visual sensor positioned at the same position and posture as in the teaching process, and the three-dimensional Define the product coordinate system for each product part based on the coordinate values,
4) The teaching data of the torch is corrected based on the difference between the product part coordinate system of the teaching work and the product part coordinate system of the actual work, and the position of the robot is controlled based on the corrected teaching data. .
In other words, the present invention defines a product coordinate system for each product part, and the product position during teaching and playback.
By correcting the teaching data of the cutting torch based on the deviation of the standard system, the runner can be cut well even if the position and posture of each product part differ to some extent.

In the present invention, as the designated point, not only a point that can be uniquely defined, but also a point that can define a line or a surface by calculating a plurality of coordinate values can be taken.
In the present invention, when a designated point at which the three-dimensional coordinate value can be uniquely specified at the designated point is referred to as a feature point, the coordinate system defined for each product is based on the number of the feature points. It is preferable to select and define from the following four methods.
A1: By three feature points
A2: One feature point, a uniquely defined one-direction reference line A3: one feature point, a uniquely defined normal passing through the feature point, and another feature point A4 : One plane that is uniquely defined based on a plurality of designated points on the plane portion, and two points that are uniquely defined projected on the plane. The present invention uses a three-dimensional visual sensor. Measure not only the coordinate values of feature points, but also the coordinate values of multiple points in a given direction to obtain uniquely defined reference lines and surfaces, and define the coordinate system based on these In addition, it is possible to expand the variety that can automatically cut the runner even for a workpiece having a product portion having a complicated shape and an unclear outline.

  According to the present invention, a runner can be automatically and satisfactorily cut even for a cast product having a product part with a complicated shape, and even when the position and orientation of the product parts vary.

Flowchart for explaining the outline of the present invention Conceptual diagram for explaining a coordinate system according to the present invention. Flow chart for selecting the coordinate system definition method The figure for demonstrating coordinate system definition method A1 The figure for demonstrating coordinate system definition method A2 The figure for demonstrating coordinate system definition method A3 The figure for demonstrating coordinate system determination method A4

  The present invention is a method for automatically cutting a runner of a cast product by controlling the position of a plasma torch or the like using a teaching reproduction type robot system, and is based on the technique in Patent Document 1. The biggest difference is in the definition method of the user coordinate system. Although details will be described later, first, the user coordinate system is set for each product unit. Accordingly, one is sufficient for a one-piece workpiece, but two are defined for a two-piece workpiece. Hereinafter, the user coordinate system is referred to as a product coordinate system and abbreviated as S coordinate. Secondly, the definition of the S coordinate is automatically performed at the time of teaching and at the time of reproduction, and a predetermined designated point is measured as described later using a three-dimensional visual sensor provided on the robot hand, thereby enabling the product This is possible even when three feature points are not obtained in the portion or when no feature points are obtained. A three-dimensional visual sensor (hereinafter abbreviated as a 3D sensor) is an imaging device that performs image processing on a laser slit light captured image, a stereo captured image, and the like to calculate a three-dimensional coordinate value of a predetermined position, a tilt of a predetermined surface, and the like. Some of the robots such as those manufactured by Kawasaki Heavy Industries, Ltd.

  First, the outline of the present invention will be described based on the flowchart of FIG. 1 and the conceptual diagram related to the coordinate system of FIG. 2. Hereinafter, it is assumed that two product parts are arranged including two workpieces, In FIG. 2, the coordinate system is shown in two dimensions for easy understanding.

In the flowchart of FIG. 1, teaching steps K1 to K3 are performed on the teaching work W set on a predetermined tool.
1) In step K1, for each of the two product parts C (C1, C2), the position and orientation of the 3D sensor are determined so as to measure a plurality of designated points selected to define the S coordinate, Calculate the three-dimensional coordinate value of the specified point. The designated point does not have to be a feature point and may not be three points, as will be described in the coordinate system definition method described later.
2) In step K2, based on the measured three-dimensional coordinate values of a plurality of designated points, two S coordinates (hereinafter referred to as “teaching S1 coordinates” and “teaching S2 coordinates”) are obtained for every two product parts by a robot controller or the like. ) Is defined. The definition method will be described later. The measurement data of the designated point is stored as the teaching S coordinate data.
3) In step K3, the working path of the runner cutting torch is taught for each of the product parts C1 and C2, and the teaching point position and orientation data T (T1, T2) are stored in the teaching S1 coordinates and teaching S2 coordinates. .

The regeneration process is indicated by K4 to K6 in FIG. 1, and is performed on the actual work Wa to be cut into runners set in a predetermined tool. The actual workpiece Wa has two product parts Ca (Ca1, Ca2) as in the teaching workpiece.
4) In step K4, the 3D sensor is sequentially positioned at the same position and posture as when the designated point of the product part C (C1, C2) of the teaching work W is measured, and each product part Ca (Ca1) of the actual work Wa , Ca2), the three-dimensional coordinate value of the designated point for defining the actual S coordinate is measured.
5) In step K5, based on the measured three-dimensional coordinate values of the plurality of designated points, two S coordinates (actual S1 coordinate, actual S2 coordinate) for each of two product parts of the actual workpiece Wa by a robot controller or the like. ) Is defined. Usually, the product part of the actual work Wa is often different in position and inclination from the product part of the teaching work W. As shown in FIG. 2, the actual S1 coordinate in the product part Ca1 is different from the teaching S1 coordinate in position and inclination. Etc. will be different. The same applies to the product portion Ca2.
6) In step K6, for the product portion Ca1, based on the deviation between the teaching S1 coordinate and the actual S1 coordinate, the teaching point data T1 of the runner cutting torch stored in the teaching S1 coordinate is corrected, and in the actual S1 coordinate The teaching point position data is Ta1. The same applies to the product portion Ca2. When the torch is moved for cutting, the teaching point data Ta (Ta1, Ta2) in the actual S coordinate (actual S1 coordinate, actual S2 coordinate) is converted into robot coordinate system data, and the position of the robot is controlled. This conversion method is known as described in Patent Document 1 and will not be described.

Next, a method for defining a coordinate system in the present invention will be described in detail.
As described above, the coordinate system is defined based on the coordinate data of the designated point measured by the 3D sensor. As the designated point, the hole center point, the centroid point, the end point, the intersection point, the arc center point, and the like are taken. be able to. Among the designated points, for example, the center point of the circular hole portion formed in the plane and the centroid point of the projecting plane portion are uniquely defined points and will be described as feature points hereinafter. On the other hand, there are innumerable end points and intersections at the edges and ridges where two surfaces intersect, and arc center points at the center of a cylindrical part having a predetermined length in a predetermined direction of the part. However, if a plurality of points along the predetermined direction are measured and their coordinate values are subjected to, for example, linear interpolation processing, a direction reference line can be defined. This direction reference line is uniquely defined in direction, and can be used to define a coordinate system. That is, the designated point can be used to define a coordinate system.

That is, in the present invention, even if three feature points are not obtained, the product coordinate system is defined by the following four methods by defining a direction reference line from other designated points. Thereby, the kind which can apply automatic runner cutting can be expanded.
A1: By three feature points (the same method as Patent Document 1)
A2: one feature point, and A3: one feature point by a one-direction reference line uniquely defined based on a plurality of designated points along the direction of the member having directionality, and the feature point Uniquely defined normal line passing through and another characteristic point A4: One plane defined based on a plurality of designated points on the planar member, and uniquely defined on the plane By two points projected from two direction reference lines

  The present invention examines the properties of the product portion for each target workpiece, and designates the designated points including the feature points required for selecting any one of the coordinate system definition methods A1 to A4 on the product portion. It is important to select with. Hereinafter, a method for defining a coordinate system in accordance with the properties of the target product part will be described with reference to the flowchart shown in FIG.

  In step S1, it is examined whether or not the product part can measure the feature point P with a 3D sensor. If it can be measured, it moves to step S2, and if it cannot, it moves to step S10. The feature point can be measured only if the product part has a hole formed in a stable flat surface or a protrusion having a stable flat surface regardless of the shape. By irradiating with light, the center of the hole or the centroid of the projection plane can be calculated.

  In step S2, it is examined whether there are three feature points P at three-dimensionally different positions. If there are three feature points, the process proceeds to step S3. If there are only one or two feature points, the process proceeds to step S4. Step S3 is a case where the coordinate system can be defined by the method of A1, and as shown in FIG. 4, for example, one feature point P1 is set as the origin, and the direction connecting the feature point P1 and the other second feature point P2 is set. A known method such as the X-axis, the plane formed by the line drawn from the other third feature point P3 to the X-axis and the X-axis is the XY plane, and the direction passing through the origin and orthogonal to the XY plane is the Z-axis. Thus, the product coordinate system can be defined. The three points are preferably as far away as possible, and if they are close to each other, it is better to move to step S4.

  Step 4 examines whether or not a direction reference line that does not include the origin can be uniquely defined when one feature point is the origin. If it can be defined, the process proceeds to step S5, and if not, the process proceeds to step 6. In order to be able to define the direction reference line, it suffices if there is a portion showing a stable directionality. For example, as shown in FIG. 5, if there is a flange F1 having a straight edge portion, the edge portion is selected. A plurality of edges in a straight line direction are designated as designated points Q (n), the coordinate values of each edge Q (n) are measured by, for example, edge measurement by a 3D sensor, and an approximate straight line Xu is calculated by linear interpolation. Can be done.

  Step 5 is a case where the coordinate system can be defined by the method A2. In FIG. 5, one feature point P1 is the origin, the axis drawn from the feature point P1 in the direction of the direction reference line Xu is the X axis, and the feature point The work coordinate system can be defined with the line segment direction lowered from P1 to the direction reference line Xu as the Y-axis direction.

  In step 6, it is examined whether or not a normal passing through one feature point can be uniquely defined. If it can be defined, the process proceeds to step S7, and if not, the process proceeds to step 8. In order to be able to define uniquely, it is sufficient that the periphery of the feature point is a plane having a stable predetermined width, and the normal can be defined based on the inclination of the plane measured by the 3D sensor.

  Step 7 is a case where the coordinate system can be defined by the method of A3. As shown in FIG. 6A, for example, one feature point P1 is the origin, and a method of passing through the feature point P1 perpendicular to the origin peripheral plane. Let line U be the X axis. Here, when there is another feature point, the coordinate system can be defined by setting the plane formed by the line segment drawn from the feature point P2 to the X axis and the X axis as the XY plane. If the product part has only one feature point P1, the above method cannot be used. However, if the product part contains two or more workpieces and the relative displacement between the product parts is small, as shown in FIG. , Using the other product part having a small relative displacement to the product part, and the line segment direction lowered from the feature point P2 of this product part to the normal line U (X axis) passing through the feature point P1 of the product part Can be defined as a Y-axis and a plane formed by the X-axis as an XY plane. If one workpiece is included, go to Step 8.

  The above is a case where even one feature point can be measured, but if it cannot be measured at all, the procedure from step 10 is considered. In step 10, it is examined whether or not the virtual plane M can be uniquely defined. If yes, go to Step 11, otherwise go to Step 8. In order for the virtual plane M to be uniquely defined, it suffices if there is a shape portion that exhibits stable flatness. For example, as shown in FIG. 7, if there is a plate-like surface such as the connection flange F2, two locations are provided. The edge portion that is not on the straight line is selected as a selected portion, at least three or more edges from the edge portion are designated as designated points R (n), edge measurement or R intersection measurement is performed to measure coordinate values, Interpolation may be performed.

  In step 11, it is examined whether or not the two points H1 and H2 projected on the specified virtual plane M are uniquely obtained. If it is obtained, the process proceeds to step 12; otherwise, the process proceeds to step 8. In order to project two points on the virtual plane M, for example, as shown in FIG. 7, at least a cylindrical member K (K1, K2) such as a boss part or a connection pipe part from the connection flange F2 is provided. In the case where two places are stably derived in a predetermined direction, a position apart from the connection flange F2 of the cylindrical portions K1 and K2 is selected, and a plurality of cylindrical center points h1 (n ), H2 (n) are measured as designated points, and an approximate straight line can be calculated by linearly interpolating these cylindrical center points h1 (n) and h2 (n), and the coordinates of the intersection of this approximate straight line and the virtual plane M Are the projection points H1 and H2.

  Step 12 is a case where the coordinates can be defined by the method of A4. For example, one projection point H1 is the origin, the direction reference line connecting the projection point H1 and the other projection point H2 is the X axis, and the projection point H1 is A product coordinate system can be defined with a normal line orthogonal to the virtual plane M as the Y axis and a direction passing through the projection point H1 and orthogonal to the XY plane as the Z axis.

  The coordinate system definition method of A1 to A4 has been described above in the procedure for selecting the coordinate system definition method. If the conditions for the coordinate system definition are not obtained, the process proceeds to step 8. did. In step 8, it is examined whether or not the shape of the product part or the plan can be changed in a part to be processed that is not related to product quality. If a hole or a planar protrusion can be formed in a portion where a feature point can be measured by a 3D sensor, for example, an appropriate weir with little deformation, the coordinate system should be defined by any one of the methods A1 to A4. Is possible.

C, Ca Product part W, Wa Work P (P1, P2, P3) Feature point Q, R Designated point
H projection point
F1, F2 Flange M Virtual plane

Claims (3)

In the method of controlling the position of the cutting torch with the robot system of the teaching reproduction system and cutting the runner of the work, which is a cast product in which one or a plurality of product parts are connected by the design part after mold separation,
In the teaching process, for the teaching work set on the specified tool,
(1) A plurality of designated points selected on the product part are measured with a three-dimensional visual sensor attached to the robot, and a product coordinate system for each product part is defined based on those three-dimensional coordinate values.
(2) Teaching the moving path of the torch for cutting the runner of the product part and storing the teaching data in the product coordinate system;
In the regeneration process, for the actual workpiece to be cut set on the specified tool,
(3) The points on the actual workpiece corresponding to a plurality of designated points selected on the product part of the teaching workpiece are measured with a three-dimensional visual sensor positioned at the same position and posture as in the teaching process, and their tertiary Define the product coordinate system for each product part based on the original coordinate values,
(4) The teaching data of the torch is corrected based on the deviation between the product part coordinate system of the teaching work and the product part coordinate system of the actual work, and the position of the robot is controlled based on the corrected teaching data. How to cut runners in castings. 2. The runner cutting of a cast product according to claim 1, wherein the designated point is not only a point that can be uniquely defined but also a point that can define a line or a surface by calculating a plurality of coordinate values. Method. In the designated point, if a designated point whose three-dimensional coordinate value can be uniquely specified is referred to as a feature point, a coordinate system defined for each product is selected from the following four methods based on the number of the feature points. A runner cutting method for a cast product according to claim 1 or 2, defined as defined above.
A1: By three feature points
A2: One feature point, a uniquely defined one-direction reference line A3: one feature point, a uniquely defined normal passing through the feature point, and another feature point A4 : One plane that is uniquely defined based on a plurality of designated points on the plane, and two points that are uniquely defined on that plane.