Method for automatically placing blanks in a strip and for calculating related scrap ratios

Abstract

A method for a computerized layout of two blanks to be cut out in a strip extending in the longitudinal direction, including the step of determining the inner dimensions of each blank in the longitudinal direction, the step of determining the distance between the left side of blank A and the right side of blank B in the longitudinal direction and, if the blanks overlap, the reverse distance, and the step of estimating the pitch between two adjacent blanks A and B and between two adjacent blanks B and A. A method for computerized scrap ratio calculation using the blank layout method, and a method for computerized calculation of the material cost of a blanking operation using the scrap ratio calculation.

Description

Technical Field

[0001] The present invention relates to the manufacture of blanks, and more particularly to the manufacture of blanks cut from a rectangular planar strip of material generally extending in a longitudinal direction.

Background Art

[0002] In many material manufacturing processes for materials that are generally planar, the continuous nature of the manufacturing process suggests that the final manufactured product is generally in the form of a long strip extending in a longitudinal direction. This applies, for example, to the production of flat sheet metals such as flat steel products or flat aluminum products. This also applies to the pulp and paper industry, or when manufacturing fabrics and textiles. The strips mentioned above are often adjusted in the form of coiling the strip into a coil shape in order to efficiently store or transfer the strip.

[0003] One common approach to using the material in subsequent deformation processes is to cut out a shape having a predetermined contour from the strip. For example, a metal blank can be cut out in the case of a metal strip, or fabric or textile can be cut out in the fashion industry. In the case of a metal strip, this operation is called blanking, and the resulting product is called a metal blank, that is, a generally planar metal piece having a predetermined contour suitable for use in subsequent deformation processes. This operation can be performed, for example, by punching, water jet cutting, oxy cutting, or laser cutting.

[0004] Hereinafter, the term "blank" is used for simplicity, but as will be readily understood, the application field of the present invention is not limited to metal materials only.

[0005] The material remaining in the strip after blank cutting is designated as scrap. Scrap is the waste material of the blanking process and should be kept to a minimum in order to optimize productivity, minimize environmental impact, and minimize the cost of the blanking operation. In the case of environmental impact, the production process for manufacturing the raw material strip itself has an environmental footprint, such as CO2 emissions. By minimizing scrap and thus maximizing the overall output of the industrial process, the environmental impact can be kept as low as possible.

[0006] In the present invention, the term cost generally refers to, for example, environmental cost, productivity cost, or economic cost.

[0007] In the present invention, the configuration is as follows: a strip from which two blanks are cut, each blank having a predetermined contour, each having a fixed orientation in the longitudinal direction, and having a given offset amount from each other in the transverse direction. The arrangement of the two blanks relative to each other in the longitudinal direction will determine a pattern, and this pattern will be repeated as long as the strip extends in the longitudinal direction. The fact that the orientation of the blank is fixed can be an industrial constraint due to anisotropic properties inherited from, for example, the rolling process in the case of metal materials such as steel or aluminum; this can also be linked to other considerations such as patterns in the textile industry, for example.

Summary of the Invention

Problems to be Solved by the Invention

[0008] The object of the present invention is to provide an automated method for arranging the given blanks in a strip and calculating the subsequent scrap ratio with an optimal material usage configuration. The scrap ratio is defined as the ratio between the scrap generated by the blanking process and the total amount of strip material used.

[0009] Another object of the present invention is to provide an automated method for calculating blank costs associated with the use of materials in a blanking operation. **Means for Solving the Problems**

[0010] By providing an optimized computer-implemented method for placing blanks, calculating scrap ratios, and calculating material costs, the present invention enables the cost of the blanking process to be efficiently designed and evaluated. Further, the automation of said operations enables them to be used in subsequent optimization routines. For example, said operations can be used in subsequent routines to find the best combination with respect to the orientation of the blank and the lateral offset amount in order to minimize overall scrap.

[0011] The object of the present invention is achieved by providing a method for computerized placement of two blanks in a strip according to claim 1, optionally with the features of claims 2 to 4, by providing a computerized scrap ratio calculation method according to claim 5, and by providing a computerized blank calculation method according to claim 6, optionally with the features of claim 7. The object of the present invention is further achieved by providing a computer program according to claim 8 and a computer-readable storage medium according to claim 9.

[0012] Next, the present invention will be described in detail and shown by way of example without introducing any constraints while referring to the accompanying drawings. **Brief Description of the Drawings**

[0013]

Figure 1

Figure 2A

Figure 2B

Figure 3A

Figure 3B

Figure 4

Figure 5A

Figure 5B

Figure 6A

Figure 6B

Figure 7A

Figure 7B

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0014] Referring to FIG. 1, in the present invention, the longitudinal direction refers to the main direction in which the strip 1 extends, and the transverse direction refers to the direction perpendicular to the longitudinal direction in the plane. Further, the strip 1 extends over a limited width between two parallel edges 2 and 3 in the transverse direction Y and extends over a width W in said direction.

[0015] The strip 1 has an upper side and a bottom side, also referred to as the upper surface and the bottom surface respectively. All the attached figures are two-dimensional top views and only the upper side is visible. The distance between the upper surface and the bottom surface is specified as the thickness of the strip. The thickness can be measured, for example, using a micrometer, with the micrometer spindle and anvil placed on the upper surface and the bottom surface.

[0016] In the following description and claims, the terms longitudinal and horizontal have the same meaning, and the terms transverse and vertical have the same meaning. The terms "left" and "right" are used in the following description and claims, and these refer to relative positions that are further rearward and further along the longitudinal direction, i.e., along the direction marked by the "L" arrow in FIG. 1 respectively. The terms "upward" (and "above", "higher than", etc.), "downward" (and "below", "lower than", etc.) are used in the following description and claims, and these mean relative positions that are further rearward and further along the transverse direction, i.e., along the direction marked by the "T" arrow in FIG. 1 respectively.

[0017] Referring to FIG. 1, a first blank A having a first contour and a second blank B having a second contour are cut from the strip 1.

[0018] The blank B is offset transversely from the blank A by a transverse offset amount dy, and the transverse offset amount dy is defined as the difference in the transverse rise between the lowermost points in the transverse direction of the blank contour B and the blank contour A.

[0019] The first object of the present invention is to determine, in an automated manner, how to arrange blanks A and B in strip 1 in order to use the minimum possible amount of material. This applies when the first set of blank A and blank B touches the next set of blank A and blank B at at least one point without overlap. And then the resulting pattern is repeated along the longitudinal direction. There are potentially several other ways to arrange blanks A and B to optimize the use of material. Each of these configurations is equivalent with respect to the use of material. The present invention aims to disclose only one such possible configuration.

[0020] The elements missing for arranging blanks A and B are the pitch Δ1 between the left end of blank A and the left end of the adjacent B blank in the longitudinal direction, and the pitch Δ2 between the left end of blank B and the left end of the adjacent A blank in the longitudinal direction. When the said pitch is determined, it becomes possible to arrange the blanks in the strip, and then, as will be further explained, it also becomes possible to calculate the scrap ratio and the material cost of the blanking.

[0021] The pitches Δ1 and Δ2 take into account the shapes and inner dimensions of A and B along the longitudinal direction, as well as the mutual relationship between blank A and B in the longitudinal direction.

[0022] To optimize the calculation time, the inventors have developed a method that involves only the inner distances between the vertices and edges of each single blank A and blank B in the longitudinal direction, and only the mutual relationship between blank A and blank B in the longitudinal direction at the points of the width where any vertex of blank A and blank B is located.

[0023] Since the number of vertices of each blank is discrete and generally very limited, the method of the present invention enables the scrap ratio to be calculated very quickly.

[0024] Referring to FIGS. 2A and 2B, an X, Y coordinate system is used to identify the positions of the vertices and the contours of blanks A and B. The X-axis is parallel to the strip longitudinal direction, while the Y-axis is parallel to the strip transverse direction. Conventionally, blank A is arranged within the coordinate system such that the leftmost point of blank A is located at X = 0 and the lowermost point of blank A is located at Y = 0. Blank B is arranged such that the leftmost point of blank B is located at X = 0 and the lowermost point of blank B is located at Y = dy.

[0025] The blank contours of A and B are represented respectively by vertices A1, A2, A3, A4, and B1, B2, B3 joined by straight edges. Each vertex A i is identified by its coordinates (XA i , YA i ), and each vertex B i is identified by its coordinates (XB i , YB i ).

[0026] For clarity, the blanks A and B in the figures have simple shapes with long straight edges. However, the method is applicable to any two-dimensional contour. In the case of a contour with a curved edge, the curved edge is approximated by a series of smaller continuous straight segments, thereby defining a set of vertices to connect the edges.

[0027] Thus, in the general case, blank A is represented by its set of p vertices {A1,..., A P}, and blank B is represented by its set of q vertices {B1,..., B q}, where p and q are integers greater than or equal to 3.

[0028] To determine Δ1 and Δ2, it is necessary to first calculate the maximum dimensions dAA and dBB in the longitudinal direction of blanks A and B respectively, and the maximum longitudinal offset amounts dAB and dBA from blank A to blank B and from blank B to blank A when the blanks overlap (see FIGS. 3A and 3B).

[0029] This is done by performing the following steps: - For each vertex A i calculate the distance dA i A defined as the difference between the maximum X value taken by the contour of blank A and the minimum X value taken by the contour of blank A at the Y value of vertex A i A, and calculate the maximum internal lateral distance dAA defined as the maximum value of all dA i A. - For each vertex B i calculate the distance dB i B defined as the difference between the maximum X value taken by the contour of blank B and the minimum X value taken by the contour of blank B at the Y value of vertex B i B, and calculate the maximum internal lateral distance dBB defined as the maximum value of all dB i B.

[0030] For example, in the simple case of FIG. 2A, dA2A and dA4A are equal to 0, while dA3A and dA1A have equal values, so dAA = dA3A = dA1A.

[0031] Blanks A and B in FIGS. 2A and 2B are of simple shapes for clarity, but in the case of more complex shapes such as blank U depicted in FIG. 4, for example, there may also be cases where a straight line parallel to the X-axis intersects the contour several times, such as in the cases of U1 and U2. In this case, as depicted in FIG. 4, the segments corresponding to dU1U and dU2U may intersect the blank contour in order to extend from a point further to the left of the contour to the rightmost point. To show another possible configuration, in the case of dU5U, the segment does not have vertex U5 as one of its endpoints, because U5 is between the leftmost and rightmost points of the contour at its Y value.

[0032] Next, the longitudinal offset amounts dAB and dBA are calculated by applying the following method: - For each vertex A located at a Y value at which there is at least one point of the contour of blank B, i at the Y value of vertex A, i as the difference between the maximum X value taken by the contour of blank B and the minimum X value taken by the contour of blank A, and at the Y value of vertex A, i as the difference between the maximum X value taken by the contour of blank A and the minimum X value taken by the contour of blank B, respectively defined directional distances dA i B and dBA i are calculated. - For each vertex B located at a Y value at which there is at least one point of the contour of blank A, i at the Y value of vertex B, i as the difference between the maximum X value taken by the contour of blank B and the minimum X value taken by the contour of blank A, and at the Y value of vertex B, i as the difference between the maximum X value taken by the contour of blank A and the minimum X value taken by the contour of blank B, respectively defined directional distances dAB i and dB i A are calculated. - Calculate the directional distance dAB defined as the maximum value of all the values of dA i B and dAB I , and all the values of dB iA and dBA I Calculate the directed distance dBA defined as the maximum value of the value of I .

[0033] Value dA i B and dAB i In the case of FIG. 3A representing the directed vector corresponding to i , for example, dAB is equal to dAB2.

[0034] Value dB i A and dBA i In the case of FIG. 3B representing the directed vector corresponding to i , dBA is equal to dBA3.

[0035] When calculating dAA, dBB, dAB, and dBA, it becomes possible to calculate Δ1 and Δ2 by the following method: - Δ1 = dBA, - When dAB + dBA ≧ dAA + dAB and dAB + dBA ≧ dBB, Δ2 = dBA - When dAB + dBA < dAA and dAA ≧ dBB, Δ2 = dAA - dBA - When dAB + dBA < dBB and dBB > dAA, Δ2 = dBB - dBA.

[0036] Knowing Δ1 and Δ2, place the first blank A on the strip, place the first blank B using the vertical offset amount of dy and the longitudinal offset amount of Δ1 compared to the first blank A, align it horizontally with the first blank A, and use the longitudinal offset amount of Δ2 towards the first blank B to place the next blank A. By repeating the pattern along strip 1 as long as strip 1 extends longitudinally, blanks A and B can be placed on strip 1.

[0037] The inventors have discovered that this method makes it possible to efficiently automate the optimal arrangement of blanks A and B.

[0038] Figures 5A, 6A, and 7A are examples of the determination of dAA, dBB, dAB, and dBA for more complex shapes. In each figure, the upper left shows how dBB is determined (only the maximum dB i B is drawn for clarity), the lower left shows how dAA is determined, the upper right shows how dAB and dBA are determined, and the table in the lower right shows the values of dAA, dBB, dAB, and dBA, and the individual dA i A, dB i B / dAB i dB i A / dBA i are summarized. For example, in the configuration of Figure 6A, dAB is negative because all individual dA i B / dABi are negative (there are no points of contour A to the left of blank B within the range of Y values of the mutual relationship between overlapping blanks A and B). In this case, dAB is actually the dA i B / dAB i with the smallest absolute value of all individual dA i B / dAB i which corresponds to the maximum value of dA i B / dAB i . The table in the lower right summarizes all dAA values, dBB values, dAB values, and dBA values, and details the calculation steps for determining the pitches Δ1 and Δ2.

[0039] Figures 6C, 7C, and 8C depict implementations of a computerized placement method using the previously calculated pitches Δ1 and Δ2.

[0040] Knowing Δ1 and Δ2, the following formula:

Equation

[0041] To calculate the blank costs Cost_blank of A and B, which are defined as the material costs of blanks A and B, taking into account the material cost, scrap ratio, and scrap cost if a scrap buyback market is available, the following additional information is required: · The strip thickness t defined above as the distance between the upper and lower sides of the strip, t is expressed in, for example, mm, · The material cost per unit of mass Cost_material, expressed in, for example, currency / ton, · The cost per unit mass of scrap Cost_Scrap, expressed in, for example, currency / ton, in cases where scrap material can be bought back, such as in the steel industry where scrap is remelted, · The material density ρ defined as the ratio between the mass and volume of the material, ρ is usually expressed in kg / m 3 and is represented in.

[0042] Cost_blank is given by the following formula: M_Section = ρ * t * W * (Δ1 + Δ2) Cost_blank = Cost_material * M_Section - Cost_Scrap * %Scrap * M_Section and can be automatically calculated using this formula.

[0043] In certain embodiments, the material cost Cost_material depends on the width W of the strip. In fact, it is provided in the form of a database Cost_database containing a set of n elements (Width_range i , Cost_material i ), where n is an integer greater than or equal to 2, i ranges from 1 to n, and where Width_range i is a width range having a minimum strip width value and a maximum strip width value, and Cost_material i is the material cost per unit of mass when the width W of the strip is within Width_range i .

[0044] Variable costs that follow the strip width can occur when the industrial cost for producing the strip actually depends on the width. For example, when an increase in width is associated with a decrease in productivity, the industrial cost can increase with the width. For example, when a material with a large width can only be produced with certain industrial equipment, thereby entailing higher logistics costs, the material cost can increase with the width.

[0045] In certain embodiments, the width W of the coil takes into account a width tolerance W_tol, usually expressed in mm. This further affects the value W of the width used to calculate the scrap cost and the blanking cost. The width tolerance corresponds, for example, to the accuracy that the strip production line can achieve with respect to the width. In order to ensure that blanks A and B fit into the strip even when the width of the produced strip is at the lower end of the width tolerance spectrum, it is necessary to target a strip width W that at least corresponds to the minimum width required to fit blanks A and B into the strip, by adding the width tolerance W_tol. This configuration is shown in FIG. 8, where a margin of W_tol / 2 is left on either side of strip 1.

[0046] In certain embodiments, when arranging blanks A and B in the strip, and thus also when calculating the scrap ratio and the blanking cost, a blanking tolerance Blank_tol, usually expressed in mm, is taken into account. The blanking tolerance corresponds to the accuracy of the tool used to cut the blanks in the strip. In order to ensure that there is no overlap between the blanks when cutting the blanks from the strip, the distance between two adjacent blanks should not be less than 2*Blank_tol (in practice, each blank is cut with an accuracy of Blank_tol, and the risk of overlap can be completely avoided only by taking into account the blanking tolerance of each individual blank and providing the distance between two adjacent blanks). This is also shown in FIG. 8.

[0047] In a particular embodiment as shown in FIG. 9, in the above-described methods for calculating Δ1 and Δ2, and in the related methods for determining the blank layout, scrap ratio, and blank cost, the blanking tolerance is taken into account, which is done by first geometrically enlarging blanks A and B by an amount of Blank_tol before applying the blank layout method. The enlarged blank contours of A and B take into account the calculation of Δ1 and Δ2, but it should be noted that when calculating the scrap ratio %Scrap, Area_A and Area_B in the formula are the areas of the non-enlarged blank contours. In reality, the material usage in the strip continues to be a direct function of the areas Area_A and Area_B and not a direct function of the area of the enlarged blank contours.

[0048] In a particular embodiment as depicted in FIGS. 5A - B, 6A - B, and 7A - B, the above-described method is applied to a configuration such that after rotating blank B about an axis perpendicular to the upper surface of the strip, blank B has exactly the same contour as blank A. This is a very common case where, in fact, there is only one blank shape cut from strip 1.

[0049] In a particular embodiment, the above-described method is applied to a configuration such that after rotating blank B about an axis perpendicular to the upper surface of the strip, blank B has a mirror-image contour of blank A. This is, for example, a common case in the automotive industry where many parts exist on both sides of the vehicle as right-side and left-side parts, which are generally mirror images of each other.

Claims

1. A computer-implemented method for arranging blank A and blank B in a planar strip (1) having a rectangular shape and extending generally in the longitudinal direction L and over a limited width in the transverse direction T, wherein the lowest point of blank B is offset horizontally by an offset amount dy compared to the lowest point of blank A, the method comprising: providing an X, Y coordinate system parallel to L and T, wherein blank A is arranged within the X, Y coordinate system such that the leftmost point of blank A is located at X = 0 and the lowest point of blank A is located at Y = 0, and blank B is arranged such that the leftmost point of blank B is located at X = 0 and the lowest point of blank B is located at Y = dy; Providing a numerical representation of the contours of blank A and blank B consisting of a discrete set of vertices {A １ ,..., A Ｐ} and {B １ ,..., B ｑ} in the X, Y coordinate system, where p and q are integers greater than or equal to 3 and the vertices are joined by straight edges, For each vertex A ｉ at the Y value of vertex A ｉ a distance dA is defined as the difference between the maximum X value taken by the contour of blank A and the minimum X value taken by the contour of blank A ｉ Calculate dA for all ｉ Step of calculating the maximum internal lateral distance dAA defined as the maximum value of all dA For each vertex B ｉ , at the Y value of vertex B ｉ , a distance dB ｉ B is defined as the difference between the maximum X value taken by the contour of blank B and the minimum X value taken by the contour of blank B, and calculate dB ｉ B, and calculating a maximum internal horizontal distance dB B defined as the maximum value of all dB Each vertex A located at a Y value where at least one point of the contour of the blank B exists ｉ For the vertex A ｉ at the Y value of the vertex A, as the difference between the maximum X value taken by the contour of the blank B and the minimum X value taken by the contour of the blank A, and ｉ at the Y value of the vertex A, the directed distances dAB ｉ and dBA ｉ are calculated Each vertex B located at a Y value where at least one point of the contour of blank A exists ｉ For vertex B ｉ at the Y value of vertex B, as the difference between the maximum X value taken by the contour of blank B and the minimum X value taken by the contour of blank A, and ｉ at the Y value of vertex B, as the difference between the maximum X value taken by the contour of blank A and the minimum X value taken by the contour of blank B, respectively defined directional distances dAB ｉ and dB ｉ A step of calculating A All dA ｉ B and dAB Ｉ Calculating the directed distance dAB defined as the maximum value of the values of B and dAB, and all dB ｉ A and dBA Ｉ Calculating the directed distance dBA defined as the maximum value of the values of A and dBA Δ １ is defined as the longitudinal pitch between the left end of the A blank and the left end of the adjacent B blank to the right thereof, and Δ １ setting Δ to the value dBA; Δ ２ is defined as the pitch between the left end of the B blank and the left end of the adjacent A blank on its right, and when dAB + dBA ≧ dAA and dAB + dBA ≧ dBB, Δ ２ is set to dBA, and when dAB + dBA < dAA and dAA ≧ dBB, Δ ２ is set to dAA - dBA, and when dAB + dBA < dBB and dBB > dAA, Δ ２ is set to dBB - dBA; A first blank A is placed in the strip, and a lateral offset amount of dy and Δ １ 1. Position the first blank B with a longitudinal offset of Δ 1.0 so as to be laterally aligned with the first blank A and toward the first blank B. ２ and repeating the pattern along strip 1 as far as it extends in the longitudinal direction. A method consisting of the above steps.

2. The method according to claim 1, further comprising an initial step of providing a blanking tolerance Blank_tol, the method further comprising, as a first step, geometrically expanding blanks A and B by an amount of Blank_tol and then applying the method of claim 1 to the resulting expanded blank contours of blanks A and B.

3. The method according to claim 1 or 2, wherein after rotating blank B about an axis perpendicular to the upper surface of strip 1, blank B has exactly the same contour as blank A.

4. The method according to claim 1 or 2, wherein after rotating blank B about an axis perpendicular to the upper surface of the strip, blank B has a mirror image contour of blank A.

5. A method for computerized calculation of a scrap ratio %Scrap defined as the ratio between scrap generated by a blanking process for cutting blanks A and B from strip 1 and the total amount of strip material used, where blank A and blank B each have a surface area Area_A and Area_A, strip 1 extends in the lateral direction over a width W, Δ １ and Δ ２ is the pitch calculated according to any one of claims 1 to 4, and %Scrap is given by the following formula 【Number 1】 A method for computerized calculation of a scrap ratio %Scrap calculated according to the following.

6. A method for computerized calculation of a blank cost Cost_blank defined as the material cost of blanks A and B taking into account the cost of the material from which the strip is made, the scrap ratio, and the cost of the scrap, where t is the strip thickness defined as the distance between the upper and lower sides of strip 1, Cost_material is the cost of the material per unit mass, Cost_Scrap is the cost of the scrap per unit mass, ρ is the material density defined as the ratio between the mass and volume of the material, and Cost_blank is given by the following formula M_Section = ρ * t * W * (Δ １ + Δ ２ ) Cost_blank = Cost_material * M_Section - Cost_scrap * %Scrap * M_Section A method for computerized calculation of the blank cost Cost_blank calculated using the above formula. Claim 7 Taking into account the variable material cost Cost_material per unit mass according to the width of the strip, Cost_material is provided in the form of a database Cost_database containing a set of n elements (Width_range ｉ , Cost_material ｉ ), where n is an integer greater than or equal to 2, i ranges from 1 to n, Width_range ｉ is a width range having a minimum strip width value and a maximum strip width value, and Cost_materia ｉ is the material cost per unit of mass when the width W of the strip is included within Width_range ｉ . A method for computerized calculation of the blank cost Cost_blank according to claim 6 Claim 8 A computer program comprising instructions that cause a computer to execute the method according to any one of claims 1 to 7 when the program is executed by the computer. Claim 9 A computer-readable storage medium that, when executed by a computer, contains instructions that cause the computer to execute the method according to any one of claims 1 to 7.

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