Flaw grinding order determination method

Abstract

To provide a flaw grinding order determination method capable of sequentially and efficiently grinding a plurality of various flaws including a rectangular flaw.SOLUTION: This flaw grinding order determination method for determining an order of grinding and removing a plurality of flaws generated on the surface of a material to be machined classifies flaw types into linear and / or rectangular flaws, moves a grinding tool from one end to the other end for the linear flaw and moves the grinding tool from one end to the other end for the rectangular flaw, then moves the grinding tool toward the other of parallel sides on a diagonal line, and moves the grinding tool from one end to the other end along the other of the diagonal lines as constraints, and determines the flaw grinding order so as to shorten a grinding distance or grinding time most by an integer schedule method.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a defect grinding order determination method for determining an efficient order for grinding away a plurality of defects occurring on the surface of a workpiece. [Background technology]

[0002] In the manufacturing process, scratches can occur on the surface of workpieces such as steel billets, and in automated processes, the scratches are ground away using a grinder supported by a robot or the like. In this case, if many scratches occur, the time (or distance) required to grind away the scratches varies greatly depending on the order in which the grinder is moved, so it is necessary to grind away the scratches in an order that is efficient.

[0003] Therefore, Patent Document 1 discloses a method of preparing a group of neural models whose number is at least the square of the number of defects, and determining the grinding sequence of the defects based on the output of these neural models. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 7-182302 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the above-mentioned conventional defect grinding sequence determination method does not mention grinding of rectangular defects, and there is a problem that the amount of calculation becomes enormous if calculations are performed assuming that the rectangular defects are linear defects.

[0006] Therefore, the present invention is devised to solve such problems, and has an object to provide a defect grinding sequence determination method that enables a variety of multiple defects, including rectangular defects, to be ground sequentially and efficiently. [Means for solving the problem]

[0007] In order to achieve this objective, the first invention is a grinding sequence determination method for determining the order in which to grind away multiple defects that have occurred on the surface of a workpiece, in which the types of defects are classified into linear defects and / or rectangular defects, and the constraints are that for linear defects, the grinding tool is moved from one end to the other end, and for rectangular defects, the grinding tool is moved from one end to the other along one of the parallel sides of the rectangular defect, then moved diagonally toward the other parallel side, and then moved from one end to the other along the other parallel side, and the grinding sequence of the defects is determined by integer programming so as to minimize the grinding distance or grinding time.

[0008] According to the first invention, the grinding sequence can be efficiently determined for rectangular defects as well as linear defects.

[0009] In the second invention, circular or irregular defects are approximated as the rectangular defects having a size that contacts the outer periphery of the circular or irregular defects.

[0010] According to the second invention, it is possible to determine an efficient grinding sequence for a variety of defects, not limited to linear defects and rectangular defects.

[0011] In the third invention, defects that are ground multiple times are placed on different layers for each grinding round, and the grinding order of the defects is determined for each layer, and the grinding paths corresponding to the grinding orders determined for layers other than layer 1 are incorporated into the grinding paths corresponding to the grinding order determined for layer 1.

[0012] According to the third aspect of the present invention, since the grinding order is determined for each layer, even when there is a defect that requires multiple grinding operations, the grinding order can be determined simply and efficiently.

[0013] In the fourth invention, when a length of contact between a plurality of adjacent rectangular defects is equal to or greater than a predetermined threshold, these rectangular defects are integrated into a single new rectangular defect that is the smallest size that encompasses these rectangular defects.

[0014] According to the fourth aspect of the present invention, the number of rectangular defects can be reduced, and the grinding order can be determined simply and efficiently. Effect of the Invention

[0015] As described above, according to the defect grinding order determination method of the present invention, a variety of defects including rectangular defects can be efficiently ground in sequence. [Brief description of the drawings]

[0016] [Figure 1] FIG. 13 is a schematic plan view illustrating approximation to a rectangular flaw. [Diagram 2] FIG. 2 is a schematic plan view showing the coordinate positions of linear scratches and rectangular scratches. [Diagram 3] FIG. 4 is a schematic plan view showing a grinding path for a rectangular flaw. [Figure 4] FIG. 2 is a conceptual perspective view showing the layer classification of scratches. [Diagram 5] FIG. 1 is a conceptual plan view showing grouping of defects. [Figure 6] FIG. 1 is a conceptual plan view showing grouping of defects. [Figure 7] 13 is a graph showing the relationship between a threshold value and a flaw area. [Figure 8] FIG. 1 is a conceptual plan view showing constraints on linear defects. [Figure 9] FIG. 13 is a conceptual plan view showing constraints for a rectangular flaw. [Figure 10] FIG. 13 is a conceptual plan view showing the grinding sequence of a non-circular circuit and a circular circuit. [Figure 11] FIG. 13 is a conceptual plan view showing a defect grinding sequence determined by incorporating a circular path into a non-circular path. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] It should be noted that the embodiment described below is merely an example, and various design improvements made by those skilled in the art without departing from the gist of the present invention are also included in the scope of the present invention. It should be noted that all of the procedures described below can be automated by a computer.

[0018] (Target defects) The defects that are targeted by the defect grinding sequence determination method of the present invention are linear defects and rectangular defects, but circular (including point-like) defects and irregular defects can be treated as rectangular defects of a size that touches the outer periphery of these defects, as shown in Figures 1(1) and (2), making it possible to target defects of virtually all shapes that occur on the surface of the workpiece.

[0019] Here, a linear defect has two end points, P1 (x1, y1) and P2 (x2, y2), as shown in FIG. 2(1), and a rectangular defect has three vertices, P1 (x1, y2), P2 (x2, y2), P3 (x2, y1), and P4 (x1, y1), as shown in FIG. 2(2).

[0020] In addition, in practice, the grinding of rectangular flaws is performed by reciprocating the path of a grinding tool such as a grinder while shifting it parallel to the width direction of the flaw as shown in Fig. 3(1), but in carrying out the method of the present invention, the grinding path is determined as shown in Fig. 3(2) by moving the tool from one end to the other along one of the parallel sides of the rectangular flaw, then moving diagonally toward the other side, and then moving from one end to the other along the other side, because this does not affect the determination of the grinding sequence.

[0021] (layer classification) However, in the case of deep scratches, multiple grindings are required to remove them. For example, as shown in Table 1, rectangular flaw 1 requires only one grinding, whereas rectangular flaws 2 and 3 require two and three grindings, respectively. The number of combinations of grinding orders when performing six grindings in total is huge, 6!=720. Therefore, as a layer model as shown in Table 2 and Figure 4, the scratches 1, 2, and 3 to be ground in the first grinding are classified into layer 1, the scratches 2 and 3 to be ground in the second grinding are classified into layer 2, and the scratch 3 to be ground in the third grinding is classified into layer 3, and the combinations of grinding orders are calculated for each layer 1, 2, and 3. This drastically reduces the number of combinations of grinding orders to a maximum of 3!=6, and greatly reduces the effort required to determine the grinding order, which will be described later. In this case, the scratches are not limited to rectangular scratches, but may be linear scratches.

[0022] [Table 1] JPEG2025072857000001.jpg56159

[0023] [Table 2] JPEG2025072857000002.jpg74156

[0024] (grouping) Furthermore, in this embodiment, when adjacent rectangular defects are present, these are grouped together as a single rectangular defect to reduce the number of defects, thereby reducing the number of combinations of grinding orders and further reducing the effort required for determining the grinding order.

[0025] Grouping is performed as follows: As shown in Fig. 5, when rectangular defects 1 and 2, whose opposing sides have lengths L1 and L2, respectively, are in contact with each other at a length L3, if Γ calculated by the following formula (1) is equal to or greater than a threshold value Γth, the two rectangular defects 1 and 2 are combined into the smallest new rectangular defect 1 that encompasses them, as shown in Fig. 6. This reduces the number of rectangular defects.

[0026] JPEG2025072857000003.jpg33153

[0027] When this grouping results in a new rectangular defect 1, the defect area increases by (S1+S2), and the grinding distance increases accordingly. Therefore, it is necessary to select the threshold value Γth appropriately so that the grinding distance does not become excessively long. That is, as shown in an example in Figure 7, the defect area of ​​the new rectangular defect 1 increases as the threshold value Γth decreases from 1 to 0, because even slight contact will result in grouping. Therefore, the threshold value Γth (arrow in Figure 7) is selected before the defect area increases sharply.

[0028] (Integer Programming) The optimal order for grinding the linear and rectangular defects on each layer obtained through the above preparations is calculated using integer programming. This calculation involves finding a combination that minimizes the objective function J shown in the following formula (2) by successively changing the combination under the following constraints. In the formula, costij is the distance (time) from point i to point j, and dij is a variable that takes the value 1 if there is movement from point i to point j, and 0 if there is no movement.

[0029] JPEG2025072857000004.jpg24150

[0030] Table 3 is a list of constraints for minimizing the value of the above objective function J. The left column of Table 1 is a formula showing the constraints, and the right column is a description showing the meaning of the formula in the left column. Figure 8 illustrates constraint 6, and Figure 9 illustrates constraint 7.

[0031] [Table 3] JPEG2025072857000005.jpg215158

[0032] Figure 10 shows the grinding sequence for rectangular defects that minimizes the value of the objective function J under the above constraints for defects 1, 2, and 3 classified in layer 1 and defects 2 and 3 classified in layer 2 described above. The numbers in parentheses in the figure indicate the grinding sequence and correspond to i and j in Table 1. The grinding sequence on layer 1 is a non-circular route with a start point and an end point given, while the grinding sequence on layer 2 is a circular route.

[0033] (2-opt method) Next, the 2-opt method, which is a method of iterative improvement, is used to incorporate the circular path of layer 2 into the non-circular path of layer 1. The 2-opt method is originally a method of calculating the value of the objective function J when two edges of the circular path are selected and swapped, and if this value becomes smaller, the swapping is performed, and if it does not become smaller, the swapping is performed, and this is repeated to minimize the objective function J. In this embodiment, this method is applied to the path connecting each rectangular flaw, and two paths a and b are selected and swapped as shown in FIG. 11, thereby incorporating the circular path of layer 2 into the non-circular path of layer 1 and completing the determination of the flaw grinding sequence. Note that, when there is layer 3 as described above or when there are more layers, the 2-opt method is similarly used to incorporate each circular path of layer 3 or more into the non-circular path of layer 1.

Claims

1. A method for determining a grinding sequence for determining the order in which multiple defects occurring on the surface of a workpiece are ground away, the method classifying the types of defects into linear defects and / or rectangular defects, and determining the order in which defects are ground away using integer programming to minimize the grinding distance or time by setting constraints as follows: for linear defects, the grinding tool is moved from one end to the other end, and for rectangular defects, the grinding tool is moved from one end to the other along one of the parallel sides of the rectangular defect, then moved diagonally toward the other parallel side, and then moved from one end to the other along the other parallel side.

2. 2. The defect grinding sequence determining method according to claim 1, wherein circular or irregular defects are approximated as the rectangular defects having a size tangent to their outer peripheries.

3. A method for determining a defect grinding order as described in claim 1, in which defects to be ground multiple times are placed on different layers for each grinding round, a defect grinding order is determined for each layer, and a grinding path corresponding to the grinding order determined for a layer other than layer 1 is incorporated into a grinding path corresponding to the grinding order determined for layer 1.

4. 2. The method for determining a defect grinding sequence according to claim 1, wherein, when a length of contact between adjacent rectangular defects is equal to or greater than a predetermined threshold, the rectangular defects are integrated into a single new rectangular defect that is the smallest possible size that encompasses the rectangular defects.

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