Method and program for calculating magnetic attraction force

Abstract

The present invention calculates magnetic attraction force to a mold in a short time in a magnetic clamping device. In the table data, the attraction surface of a magnetic clamp device 10 is divided into unit regions in a matrix shape, and each of the unit regions is specified as one cell in matrix coordinates. In the cell at the position corresponding to the magnetic pad, a predetermined numerical value other than "0" is set, and the other cells have "0" or are left blank. A matrix coordinate calculation unit 120 obtains matrix coordinates of cells corresponding to vertices located at diagonal positions of a mold 2a when the representative position of the mold 2a is positioned at a representative position on a platen 3 side. A tabulation unit 130 sums up the numerical values set in the cells in the range surrounded by the rectangles designated by the obtained matrix coordinates.

Description

Magnetic Adsorption Force Calculation Method and Its Calculation Program 【0001】 The present invention relates to a method for calculating the magnetic adsorption force when attaching a mold to a magnetic clamp device and its calculation program. 【0002】 As a device for attaching a mold to an injection molding machine, a magnetic clamp device that utilizes magnetic adsorption force is known. For example, the magnetic clamp device disclosed in Patent Document 1 mounts a plate body made of a magnetic material on the platen of the injection molding machine and fixes the mold by magnetic adsorption force. A plurality of magnetic pads are provided on the plate body. Each magnetic pad has a magnet (e.g., neodymium magnet) with non-invertible polarity provided around the magnetic pole and a magnet (e.g., alnico magnet) with invertible polarity arranged on the back side of the magnetic pole. By controlling the magnetic polarity of the alnico magnet with a coil, it is possible to switch between a magnetic circuit closed within the plate body and a magnetic circuit passing through the mold. 【0003】 As a method for positioning the mold at a predetermined position on the platen, a locater ring method, a positioning block method, etc. are used. In the positioning method by the locater ring method, a protrusion called a locater ring is provided near the center of the back of the mold, and the locater ring is inserted into a hole provided in the fixed-side platen, thereby positioning the attachment to the fixed-side platen. Also, in the positioning block method, a tapered positioning protrusion engages with a positioning notch on the mold side and a positioning protrusion on the platen side so that the tapered positioning protrusion follows the tapered shape due to the weight of the mold, eliminating lateral displacement. When the placement surface on the mold side contacts the mold receiving surface, the positioning in the height direction is completed. 【0004】 Japanese Patent Publication No. 2005-515080, Japanese Patent No. 4235495 【0005】 The back surface of the mold adsorbed by the magnetic clamp device is generally rectangular, but the longitudinal and lateral sizes vary depending on the mold. On the other hand, on the adsorption surface of the magnetic clamp device side, the magnetic pads are discretely arranged, and not necessarily all the magnetic pads contact the back surface of the mold. They may contact, not contact, or partially contact. 【0006】 While the magnetic attraction force on a particular mold can be measured when it is actually attached to a magnetic clamping device, it is also necessary to predict in advance how much magnetic attraction force will be exerted. If the measured value is significantly lower than the predicted value, the surface condition of the back of the mold can be inspected and examined. 【0007】 One method for predicting magnetic attraction force is to determine the contact area between the back of the mold and the magnetic pad, and then multiply this area by the magnetic attraction force per unit area. This method is only an approximation because it does not take into account the magnetic flux that wraps around the magnetic pad from space, but it is a useful method for simply determining magnetic attraction force. 【0008】 However, when determining the area in contact between the back of the mold and the magnetic pad, complex area calculations, such as calculating the area of ​​a sector using trigonometric functions, are essential in areas where the magnetic pad is circular or elliptical and partially overlaps with the back of the mold. In the processing unit of the magnetic clamping device, this calculation process can take several seconds to tens of seconds, causing user dissatisfaction with the responsiveness. 【0009】 To solve these problems, the object of the present invention is to provide a magnetic attraction force calculation method and a calculation program that can calculate the magnetic attraction force to a mold in a short amount of time. 【0010】To achieve the above objective, the present invention provides a method for calculating magnetic attraction force when a rectangular mold is attached to a platen fitted with a magnetic clamp device, wherein the attraction surface of the magnetic clamp device is divided into unit regions in a matrix, and each unit region is identified as one cell by matrix coordinates in table data, wherein a predetermined numerical value other than "0" is set in the cell corresponding to the position of the magnetic pad, and "0" is entered or the cell is left blank in the other cells, the matrix coordinates corresponding to the representative position of the table data are kept as representative matrix coordinates, the matrix coordinates of the cells corresponding to the diagonal vertices of the mold are obtained from the representative matrix coordinates when the representative position of the mold is positioned at the representative position on the platen side, and the magnetic attraction force is calculated by summing the numerical values ​​entered in the cells within the range specified by the obtained matrix coordinates. 【0011】 Furthermore, the present invention is a calculation program for calculating the magnetic attraction force when a rectangular mold is attached to a platen fitted with a magnetic clamp device, and is characterized by having a matrix data in which the attraction surface of the magnetic clamp device is divided into unit regions in a matrix, and each unit region is identified as one cell by matrix coordinates, wherein a predetermined numerical value other than "0" is set in the cell corresponding to the position of the magnetic pad, and "0" is entered or left blank in the other cells, and the matrix coordinates corresponding to the representative position of the table data are held as representative matrix coordinates, and a matrix coordinate calculation unit that finds the matrix coordinates of the cells corresponding to the diagonal positions of the mold when the representative position of the mold is positioned at the representative position on the platen side, and a spreadsheet calculation unit that sums the numerical values ​​entered in the cells within the range specified by the obtained matrix coordinates. 【0012】According to the present invention, the magnetic clamping surface is divided into unit regions, and each unit region is represented as a single cell in the table data. A predetermined value other than "0" is set in the cell corresponding to the magnetic pad, and "0" (or null) is set in the other cells. The values ​​entered in the cells within the range enclosed by the rectangle specified by the matrix coordinates at the diagonal positions are summed, and the magnetic attraction force can be calculated based on this value. Since this calculation does not require complex area calculations, the magnetic attraction force can be determined in a short time even with a processing device with low computing power. 【0013】 Figure 1 shows the process of setting up a mold on an injection molding machine; Figure 1A shows the injection molding machine and the mold, and Figure 1B shows the suspended mold. Figure 2 shows a magnetic clamping device attached to the fixed platen. Figure 3 is a diagram illustrating an example of magnetic pad data set in the processing device; Figure 3A shows an example magnetic clamping device, and Figure 3B shows the magnetic pad data. Figure 4 is a diagram illustrating the schematic configuration of the processing device. Figure 5 is a diagram illustrating the processing; Figure 5A shows the mold, and Figure 5B shows the mold schematically overlaid on the table data. Figure 6 shows the surface of the mold to be attached. Figure 7 shows the mold-side worksheet. 【0014】 [Example 1] Figure 1 shows the process of setting up a mold 2 in an injection molding machine 1. In Figure 1A, the injection molding machine 1 has a fixed platen 3 and a movable platen 4. The movable platen 4 is guided by a bar 5 and can move relative to the fixed platen 3. Magnetic clamping devices 10 and 20 are attached to the fixed platen 3 and the movable platen 4, respectively. The magnetic clamping devices 10 and 20 are controlled by a processing unit 30. The processing unit 30 exchanges necessary information with the injection molding machine 1. The processing unit 30 is a computer with control software and spreadsheet software installed. 【0015】In the drawing, an injection unit 7 having a hopper 6 for inserting raw material is positioned to the right of the fixed platen 3, and an injection nozzle 8 is attached to the injection unit 7. The injection nozzle 8 injects the raw material into the mold 2 through a hole made in the fixed platen 3. 【0016】 Figure 1B shows a suspended mold 2. The mold 2 is suspended with the fixed mold 2a and the movable mold 2b facing each other. Suspension rings 9a and 9b are provided at one location each on the diagonal lines between the fixed mold 2a and the movable mold 2b. In this embodiment, a positioning method using locating rings is applied, and a locating ring 2c is attached to the mold 2a at the center of the back surface of the mold 2a. 【0017】 Figure 2 shows the suction surface of the magnetic clamp device 10 attached to the fixed platen 3. The magnetic clamp device 10 will be described below. 【0018】 The magnetic clamping surface of the magnetic clamping device 10 exposes the circular pad surfaces of multiple magnetic pads 11 and the surrounding surface of the plate body 13. The plate body 13 is made of a magnetic material. The magnetic clamping surface of the magnetic clamping device 10 is provided with a reference hole 12 into which the locating ring 2c is pressed. The reference hole 12 communicates with a hole on the fixed-side platen 3 through which the injection nozzle 8 passes toward the mold 2a (if the magnetic clamping device 10 is not attached to the fixed-side platen 3, the locating ring 2c is pressed into this hole). 【0019】 Next, a method for calculating the magnetic attraction force when attaching the mold 2a to the magnetic clamping device 10, and a program for calculating that force, will be described. In this invention, spreadsheet software is used. As a spreadsheet software, for example, Microsoft Excel (registered trademark) is well known. The spreadsheet software used in this embodiment is not limited to Microsoft's spreadsheet software, but since its human interface is well known, for the sake of explanation, the notation of that human interface will be used in the explanation. 【0020】According to the company's spreadsheet software, table data is represented in row / column format, with row identifiers (A, B, ...) in the first row and column identifiers (1, 2, ...) in the leftmost column. For each cell in the table data, the matrix coordinates can be specified by a combination of row and column identifiers, such as "A3" or "E5". The software also provides a SUM function that sums the numbers entered in a selected range. The SUM function can be written as "=SUM(A1:A100)" or "=SUM(A1,A2...)". When written as "=SUM(A1:A100)", a rectangle is specified with matrix coordinates A1 and A100 as diagonal positions, and the numbers entered in the cells within this rectangle are summed. 【0021】 Figure 3 illustrates an example of tabular data held in the processing unit 30. The suction surface of the illustrated magnetic clamp device 10 (Figure 3A) is rectangular in shape with an outer dimension of 1 m x 1 m, and four magnetic pads 11 are arranged therein. A reference hole 12 into which a locating ring 2c is pressed is provided at the central position (500 mm x 500 mm). Note that the suction surface of a real magnetic clamp device is not necessarily a perfect rectangle, but it is sufficient to virtually assume a rectangle that encloses all the molds to which it is intended to be attached. The tabular data corresponding to the suction surface of such a magnetic clamp device 10 can be represented as tabular data with 1000 rows x 1000 columns (see Figure 3B). In this tabular data, the magnetic clamp device 10 is divided into 1 mm x 1 mm unit areas in a matrix, and each unit area corresponds to one cell and is identified by matrix coordinates. The matrix coordinates of the cell corresponding to the upper left unit area of ​​the magnetic clamp device 10 are A1 (position 0 mm vertically, 0 mm horizontally), and the matrix coordinates of the cell corresponding to the lower right unit area are ALL1000 (position 1000 mm vertically, 1000 mm horizontally). 【0022】The position of the reference hole 12 into which the locating ring 2c is pressed is defined as the representative position on the fixed platen 3 side, and the representative matrix coordinates of the cell corresponding to this representative position are set to SF500 (the central matrix coordinates, 500 mm vertically and 500 mm horizontally). On the other hand, the representative position on the mold 2a side is the position of the locating ring 2c. 【0023】 In this type of tabular data, the cell corresponding to the coordinate position of the magnetic pad 11 is filled with the number "1", while the other cells are filled with the number "0" or left blank "null". In the diagram, only "1" is entered to avoid complexity. 【0024】 Figure 4 shows the schematic configuration of the processing unit 30. The processing unit 30 receives mold data. For the sake of explanation, the mold is assumed to have a vertical length of 500 mm and a horizontal length of 500 mm, as shown in Figure 5A, and the position of the locating ring 2c is set to the center position where the diagonals intersect. 【0025】 The matrix coordinate calculation unit 120 calculates the matrix coordinates (IP250, ADV750) of the cells corresponding to the vertices of the upper left corner and lower right corner of the mold 2a (vertices located diagonally opposite each other), based on the input mold data, when the central position of the locating ring 2c is aligned with the cell of the representative matrix coordinate SF500 of the position of the reference hole 12. The calculations required for this calculation are simple arithmetic operations. 【0026】 Figure 5B schematically shows the mold 2a shown in Figure 5A superimposed on the spreadsheet data. The mold 2a is indicated by a dashed line. The spreadsheet unit 130 calculates the sum of the cells entered in the range enclosed by the matrix coordinates at the diagonal positions obtained (see Figure 5B) = SUM(IP250:ADV750). Since "1" is entered in each cell corresponding to the magnetic pad 11, the sum is a value corresponding to the overlapping area of ​​the magnetic pad 11 and the mold 2a. 【0027】The magnetic attraction force conversion unit 140 converts the obtained total into magnetic attraction force. If the magnetic attraction force per unit area is defined, the total magnetic attraction force can be obtained by multiplication. Alternatively, the magnetic attraction force values ​​corresponding to the obtained total may be stored in memory as a correspondence table in advance, and the corresponding magnetic attraction force can be retrieved based on the total result and displayed on the display of the processing unit 30. Since it only involves retrieving data, the result can be obtained slightly faster than calculation. The degree of approximation of the obtained magnetic attraction force changes depending on the size of the unit area, but the accuracy of the outer shape of the mold 2a is not very high, and a sufficiently reliable value can be obtained even at 1 mm x 1 mm. 【0028】 In this embodiment, "1" was set for each cell at the coordinate position corresponding to the magnetic pad 11, and "0" (or null) was set for the other cells. However, other predetermined numerical values ​​other than "0" may be set for each cell at the coordinate position corresponding to the magnetic pad 11. For example, the value of the magnetic attraction force per unit may be set. In that case, processing by the magnetic attraction force conversion unit 140 is unnecessary. Also, in this case, the value of the magnetic attraction force per unit at the periphery of the magnetic pad 11 and the value of the magnetic attraction force per unit at the center of the magnetic pad 11 do not have to be the same. This makes it possible to handle cases where it is known that there are differences in magnetic flux density depending on the location. 【0029】 In this embodiment, the magnetic clamping surface of the magnetic clamping device 10 is divided into unit regions, and each unit region is represented as a single cell in the table data. A predetermined value other than "0" is set in the cell corresponding to the magnetic pad 11, and "0" (or null) is set in the other cells. The values ​​entered in the cells within the range enclosed by the rectangle specified by the matrix coordinates at the diagonal positions are summed up, and the magnetic attraction force can be calculated based on this value. Since this calculation does not require complex area calculations, the magnetic attraction force can be determined in a short time even with a processing device 30 that has low computing power. 【0030】[Example 2] Depending on the mold owned by the customer, there may be irregularities in the outer shape and defects such as holes on the surface of the mold to be attached. If these defects coincide with the position of the magnetic pad 11, errors will occur in the method of Example 1. Example 2, which will be described below, is effective when the outer shape of the mold is irregular (for example, the area 41 shown by the dashed line) and cannot be considered rectangular, or when there are defects such as holes (for example, the area 42) on the surface of the mold to be attached (hereinafter collectively referred to as "defects"). 【0031】 In Example 1, when the representative position of the mold is positioned at the representative position on the platen side, the matrix coordinates of the cells corresponding to the diagonal vertices of the mold are obtained from the representative matrix coordinates, and the numerical values ​​entered in the cells within the range specified by the obtained matrix coordinates are summed. In Example 2, however, other functions of spreadsheet software are used. 【0032】 In Example 2, the table data created in Example 1 is referred to as the clamp-side table. Furthermore, for the mold 10 side, the surface to be attracted is divided into unit areas of the same size as the platen side, and a mold-side table is prepared in which each unit area is represented as a single cell. Then, numerical values, characters, or formatting are assigned to the cells corresponding to missing data in the mold-side table, and the magnetic attraction force is determined by performing a predetermined process using the clamp-side table and the mold-side table. For the sake of explanation, the following explanation will use the worksheet function of spreadsheet software, with the mold-side table provided on the mold-side worksheet and the clamp-side table on the clamp-side worksheet. It goes without saying that the mold-side table and the clamp-side table may also be calculated in separate areas within the same worksheet. 【0033】In Example 2, there are several forms of predetermined processing for the clamp-side worksheet and the mold-side worksheet, each of which will be explained using Figure 7. Note that the clamp-side worksheet 44 is the same as the table data in Example 1, so its explanation will be omitted. In the following example, the mold-side worksheet 45 is arranged so that the center position of the locating ring 2c and the position of the reference hole 12 overlap on the clamp-side worksheet 44. The mold-side worktable and the clamp-side worktable do not need to be the same size as long as there is a corresponding relationship between each cell. In the mold-side worksheet 45, cells corresponding to areas where there is no metal to be attracted are marked with "*". If the mold-side worktable and the clamp-side worktable are the same size on the worksheet, "*" will be entered over a wide area 43 of the outer shape of the mold 10 on the mold-side worksheet 45. Cells corresponding to areas with metal or the locating ring 2c are marked with "0" or null. In addition, a results worksheet 46 for obtaining the results is prepared as needed for the calculation. A predetermined numerical value other than "0" is set in the cell corresponding to the magnetic pad, which in this case will be x (numerical data). 【0034】 [Example 2-1] Form in which a numerical value is inserted into a cell In this form, "-x" is entered into the "*" cell in the mold-side worksheet 45 in Figure 7. 【0035】The information of the same cell positions in the mold-side worksheet 45 and the clamp-side worksheet 44 is added together. This can be calculated by adding (or subtracting x) the mold hole portion "-x" from the magnetic pole portion 1. Then, the result is output to the result worksheet 46, displaying "0" if the value is 0 or less. More specifically, this calculation is performed by setting "=IF(cell position in mold-side worksheet + cell position in clamp-side worksheet) <= x, 0, cell position in mold-side worksheet + cell position in clamp-side worksheet)" in each cell of the result worksheet 46, so that if the added value is 0 or less, "0" is displayed, and otherwise the original value is displayed. Alternatively, it can be displayed as null. In this case, set "=IF(cell position in mold-side worksheet + cell position in clamp-side worksheet) <= x, "", cell position in mold-side worksheet + cell position in clamp-side worksheet)" in each cell of the result worksheet. 【0036】 The magnetic attraction force can be determined by calculating the sum in the results worksheet 46 either within the range of the mold 10 (a rectangular area specified by the matrix coordinates of cells corresponding to the diagonal vertices of the mold 10, similar to Example 1) or over the entire results worksheet 46. 【0037】 [Example 2-2] Form in which text is inserted into a cell This form differs from Example 2-1 in that a "string" (for example, "a") is entered into the "*" cell in the mold-side worksheet 45 in Figure 7. 【0038】 When a string (for example, "a") is added to a number, spreadsheet software cannot perform the calculation and returns an error value (#VALUE!). This can be used to generate an error, and based on that result, the cell can be made to appear as "0". For example, you can set "=IFERROR(cell position in mold-side worksheet + cell position in clamp-side worksheet), 0)" in a cell in the results worksheet 46. By calculating the sum in the results worksheet 46 for the range of mold 10, or for the entire mold, the magnetic attraction force can be determined. "=IFERROR(cell position in mold-side worksheet + cell position in clamp-side worksheet), "")" can also be used. 【0039】 [Example 2-3] Form utilizing multiplication In this form, the cells marked with "*" in the mold-side worksheet 45 in Figure 7 are filled with "0". All other cells are filled with "1". This method utilizes the fact that multiplying a cell value by "0" always results in "0". More specifically, this calculation is performed by setting "=cell position in mold-side worksheet * cell position in clamp-side worksheet" in each cell of the results worksheet 46. The magnetic attraction force can be determined by calculating the sum in the results worksheet for the range of the mold 10 or for the entire mold. 【0040】 [Example 2-4] Form using cell formatting (data validation) In this form, only text can be entered into the "*" cells in the mold-side worksheet 45 in Figure 7 (i.e., numbers cannot be entered), and "0" or null is entered into all other cells. As a result, the corresponding cells in worksheet 46 are set to (= cell position in clamp-side worksheet + cell position in mold-side worksheet). 【0041】 In this way, in the resulting worksheet 46, the cells corresponding to "*" will display the formula as is, and will not be displayed as numbers. When calculating the total for the entire worksheet or for the range of molds 10, cells that are recognized as text will be excluded from the calculation. 【0042】 [Example 2-5] Form for inserting numerical values ​​into cells In this form, the cell marked "*" in the mold-side worksheet 45 in Figure 7 is entered with "1" or a larger number from the clamp-side worksheet. All other cells are filled with "0" or null. 【0043】 The cells in the clamp-side worksheet 44 and the corresponding cells in the mold-side worksheet 45 are added together. When the position of the cell corresponding to the magnetic pad 11 is added to the cell in the area of ​​the mold 10 where there is no metal to be attracted, the result will be a value greater than 1. Using this, the IF function is used to set all numbers greater than 1 to 0. 【0044】Specifically, in each cell of the result worksheet 46, set "=IF((cell position on the mold side worksheet + cell position on the clamp side worksheet)>x, 0, cell position on the mold side worksheet + cell position on the clamp side worksheet)". Or set "=IF((cell position on the mold side worksheet + cell position on the clamp side worksheet)>=x, "", cell position on the mold side worksheet + cell position on the clamp side worksheet)". By calculating the sum within the range of the mold 10 in the result worksheet 46 or for the entire worksheet, the magnetic adsorption force can be obtained. 【0045】 In the above embodiment, the position of the locate ring 2c was the central position of the mold 2a. However, if it is not at the central position, the processing device 30 needs to obtain the positional relationship between the representative position on the mold side and the diagonal vertex position of the mold from the injection molding machine 1 or other input means. 【0046】 In the above embodiment, the position of the reference hole 12 into which the locate ring 2c is pushed was used as the representative position of the stationary platen 3. However, if there are other positions that can be used for positioning between the mold 2a and the adsorption surface of the magnetic clamp device 10, those positions may be used. Also, in the case of the positioning block method, the positions of the positioning protrusions and the mold receiving surface may be used as the representative positions on the stationary platen side. In this case, the representative position on the mold side is the position of the positioning notch and the placement surface on the mold side, and it is necessary to obtain the positional relationship between the representative position on the mold side and the diagonal vertex position of the mold. By doing so, the matrix coordinates of the cells corresponding to the vertices at the diagonal positions of the mold in the state where the mold is correctly mounted on the positioning protrusions and the mold receiving surface can be obtained. 【0047】1 Injection molding machine 2, 2a, 2b Mold 2c Locating ring 3 Fixed platen 4 Movable platen 5 Bar 6 Hopper 7 Injection unit 8 Injection nozzle 9a, 9b Ring 10, 20 Magnetic clamping device 11 Magnetic pad 12 Reference hole 13 Plate body 20 Magnetic clamping device 30 Processing device 44 Clamp-side worksheet 45 Mold-side worksheet 46 Result worksheet 120 Matrix coordinate calculation unit 130 Spreadsheet unit 140 Magnetic attraction force conversion unit

Claims

1. A calculation method for calculating the magnetic attraction force when a rectangular mold is attached to a platen fitted with a magnetic clamping device, wherein the attraction surface of the magnetic clamping device is divided into unit regions in a matrix, and each unit region is identified as one cell by matrix coordinates, and the table data is held in which a predetermined value other than "0" is set in the cell corresponding to the position of the magnetic pad, and "0" is entered or the cell is left blank, the matrix coordinates corresponding to the representative position of the table data are held as representative matrix coordinates, and when the representative position of the mold is positioned at the representative position on the platen side, the matrix coordinates of the cell corresponding to the vertex at the diagonal position of the mold are obtained from the representative matrix coordinates, and the magnetic attraction force is calculated by summing the values ​​entered in the cells within the range specified by the obtained matrix coordinates.

2. A calculation program for calculating the magnetic attraction force when a rectangular mold is attached to a platen fitted with a magnetic clamping device, wherein the attraction surface of the magnetic clamping device is divided into unit regions in a matrix, and each unit region is identified as one cell by matrix coordinates, the table data is held in which a predetermined numerical value other than "0" is set in the cell corresponding to the position of the magnetic pad, and "0" is entered or left blank in the other cells, the matrix coordinates corresponding to the representative position of the table data are held as representative matrix coordinates, the matrix coordinate calculation unit finds the matrix coordinates of the cells corresponding to the diagonal positions of the mold when the representative position of the mold is positioned at the representative position on the platen side, and the table calculation unit sums the numerical values ​​entered in the cells within the range specified by the obtained matrix coordinates.

3. A calculation method for calculating the magnetic attraction force when a rectangular mold is attached to a platen fitted with a magnetic clamp device, comprising: a clamp-side table in which the attraction surface of the magnetic clamp device is divided into unit regions in a matrix, with each unit region identified as a single cell by matrix coordinates, wherein a predetermined numerical value x other than "0" is set in the cell corresponding to the magnetic pad, and "0" is entered or the cell is left blank; a mold-side table in which the surface of the mold to be attracted is divided into unit regions in a matrix, with each unit region identified as a single cell by matrix coordinates, wherein a predetermined numerical value, character or format is set in the cell corresponding to the missing cell, and "0" is entered or the cell is left blank; a calculation method for calculating the magnetic attraction force by aligning the representative position of the clamp-side table and the representative position of the mold-side table, performing a predetermined process on the data entered in each cell of the clamp-side table and the mold-side table, and summing the numerical values ​​of the processing results entered in each cell.

4. The calculation method of claim 3, wherein the cell corresponding to the missing part of the mold-side table is entered with the value -x, and the predetermined process is the sum of the data in the corresponding cells of the clamp-side table and the mold-side table.

5. The calculation method of claim 3, wherein a numerical value of 1 or more is entered in the cell at the position corresponding to the defect in the mold-side table, and the predetermined process is the sum of the data in the corresponding cells of the clamp-side table and the mold-side table, which is added to the predetermined numerical value, and cells that result in a numerical value greater than the predetermined numerical value are treated as "0" or null when the sum is performed.

6. The calculation method of claim 3, wherein a string is entered in the cell corresponding to the missing position in the mold-side table, the predetermined process is the sum of the data in the corresponding cells of the clamp-side table and the mold-side table, an error is caused by the addition of a numerical value and a string, and the cells in which the error occurs are treated as "0" or null when performing the sum.

7. The calculation method of claim 3, wherein the format of the cell corresponding to the missing value in the mold-side table is set so that the data to be entered is treated as a string, the predetermined process is the sum of the data in the corresponding cells of the clamp-side table and the mold-side table, an error is caused by the addition of a numerical value and a string, and the cell in which the error occurred is treated as "0" or null when performing the sum.

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