Foreign object detection in press die

Abstract

To specify a position of a foreign object on a die by providing simple sensor devices at at least four corners of the die to measure a distance between upper and lower dies or loads and calculating a difference between measurement values of the sensors.SOLUTION: In a press die foreign object detection method according to the invention, sensors are respectively attached to stroke ends disposed at at least four corners of a die in a press device. Then, distances between the respective sensors and a stripper plate in a press stroke are measured to calculate a difference between a total of measurement values of sensors disposed at the front side and a total of measurement values of sensors disposed at the back side and a difference between a total of measurement values of the sensors disposed at the left side and a total of measurement values of the sensors disposed at the right side, thereby specifyng a position of a foreign object on the die.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for detecting foreign matter on a press die in a simple manner. [Background technology]

[0002] Press machines are widely used to form metal sheets and other materials. In press machines, an upper die set and upper mold are attached to a slide, and a lower die set and lower mold are attached to a bolster. The slide moves up and down to form the metal sheet placed between the upper and lower molds. When molds are used for such press forming for a long period of time, they can become worn or become unable to form properly due to slugs or other issues. The challenge was to quickly detect such abnormalities.

[0003] Patent Document 1 discloses a slug-lift detection device for a press machine used to punch out fine patterns such as lead frames. The device includes a circuit that detects slug lift before and after the stripper packing plate impacts the workpiece and calculates the displacement gradient immediately before the bottom dead center position from the displacement of the stripper packing plate; a memory circuit that stores values ​​for each of several consecutive shots of the press die; a standard deviation calculation circuit and reference value input circuit that calculate a standard deviation from the values ​​in the memory circuit and set it as a set value; a gradient comparison circuit and stop circuit that compare the set value with the displacement gradient using the reference value based on the standard deviation; and a stop circuit that determines slug lift as slug lift and stops the press machine when the gradient comparison circuit detects slug lift and stops the press machine. This technology uses a displacement sensor to measure the distance between the upper and lower dies and compares it to a normal value to detect slug lift. However, when the die is large, it is difficult to determine the location of the foreign object on the die.

[0004] Patent Document 2 discloses a slag lift detection device that includes a displacement sensor that detects the gap between the stripper and the die, a control unit that receives the output of the displacement sensor as an input, a data storage means that stores the output of the displacement sensor during multiple press operations under normal conditions, an allowable level determination means that determines, from the stored displacement data, an allowable level for each displacement sensor under conditions in which slag lift does not occur, a monitoring range determination means that determines the range of monitoring data from when the stripper presses the workpiece to when the punch begins to process the workpiece, and an abnormality confirmation means that detects whether the output from each displacement sensor during actual operation is within the monitoring data range but below the allowable level. This technology uses displacement sensors located at the four corners of the die to detect slag lift, which is considered to be more accurate than Patent Document 1, but it still cannot identify the location of the foreign object on the die. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 8-229620 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-79699 Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above-mentioned problems, an object of the present invention is to identify the location of a foreign object on a mold by attaching a simple sensor device to at least four corners of the mold to measure the distance or load between the upper and lower molds and calculating the difference in the sensor measurement values. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the method for detecting foreign matter in a press die according to the present invention is characterized in that a sensor is attached to each of the stroke ends located at at least four corners of the die in a press apparatus, the distance between each sensor and the stripper plate during the press stroke is measured, and the position of the foreign matter on the die is identified by calculating the difference between the total measurement values ​​of the sensors located on the front side and the total measurement values ​​of the sensors located on the rear side, and the difference between the total measurement values ​​of the sensors located on the left side and the total measurement values ​​of the sensors located on the right side.

[0008] Another method of the present invention is characterized in that a sensor is attached to each of the stroke ends located at at least four corners of a die in a press apparatus, the load received by each sensor through the stripper plate during the press stroke is measured, and the position of the foreign matter on the die is identified by calculating the difference between the total measurement values ​​of the sensors located on the front side and the total measurement values ​​of the sensors located on the back side, and the difference between the total measurement values ​​of the sensors located on the left side and the total measurement values ​​of the sensors located on the right side. [Effects of the Invention]

[0009] The press die foreign object detection method of the present invention attaches a displacement sensor or load sensor to each stroke end of the die, measures the distance or load, and then calculates the difference between the left-right and front-back values ​​to identify the location of the foreign object on the die. It is also possible to detect die wear by comparing the measured values ​​with those in a normal state. Furthermore, because sensors are placed at at least four corners of the die, it is also possible to check the accuracy (flatness, parallelism) of the die and the accuracy (parallelism) of the press device slide. Because the stroke ends are easily attached and detached, sensors can be easily replaced and attached to the desired press device. [Brief explanation of the drawings]

[0010] [Figure 1]1A and 1B are diagrams showing the layout of sensors as an embodiment of a method for detecting foreign matter in a press die according to the present invention, where (a) is a plan view of a lower die, and (b) is a partial cross-sectional view of the press die taken along the line AA. [Figure 2] 2 is a partial cross-sectional view showing a main part of the arrangement of the method for detecting foreign matter in a press die shown in FIG. 1. FIG. [Figure 3] 2A and 2B are diagrams showing an example of an experiment for actually identifying the location of a foreign object using the embodiment shown in Fig. 1, where (a) is a plan view of a lower die and (b) is a partial cross-sectional view of a press die. [Figure 4] The data shown here is from an experiment to identify the location of a foreign object using the sensor arrangement shown in Figure 3. (a) shows the measurement value when the foreign object (shim) was located 10 mm from the left edge of the mold, (b) 25 mm, (c) 45 mm, (d) 95 mm, (e) 115 mm, and (f) 130 mm. [Figure 5] A graph for identifying the location of a foreign object from the data shown in FIG. 4 is shown. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present invention will now be described with reference to the drawings. Figure 1 shows the sensor arrangement as an example of a method for detecting foreign matter in a press die according to the present invention. Figure 1(a) shows a plan view of the lower die 4, with normal stroke ends located at at least four corners. These are components that prevent the material being formed from being crushed by the stripper plate. Figure 1(b) shows a cross-sectional view taken along AA in Figure 1(a). A strain (displacement) sensor is attached to each stroke end 6. Figure 2 shows an enlarged view of the main part of Figure 1(b). Sensor 10 is attached to the body of the stroke end 6, with wiring extending to the outside of the press die.

[0012] An example of foreign object detection based on the above configuration will be described. Figure 3(a) shows the same stroke end layout as Figure 1(a), but with the sensors attached to each stroke end clearly distinguishable. Commercially available strain gauges were used as sensors. The sensor at stroke end 6a is designated FL, 6b FR, 6c RR, and 6d RL. Figure 3(b) shows a cross-sectional view of the press die. A shim (1.0 mm x 5 mm x 5 mm) was placed on the lower die 4 as foreign object 30, and the press was operated to measure the values ​​of each sensor. The shim was placed horizontally on a line connecting the midpoint between stroke ends 6a and 6d and the midpoint between stroke ends 6b and 6c in Figure 3(a).

[0013] The amount of strain (ε) measured by a strain gauge is calculated as -ΔL / L (ΔL: deformed length, L: length before force is applied) in the case of compressive strain. Figure 4 shows the actual measured values. Figure 4(a) shows the case where the shim was placed 10 mm from the left end of the lower die 4 in Figure 3(a), while measurements were taken at 25 mm in (b), 45 mm in (c), 95 mm in (d), 115 mm in (e), and 130 mm in (f). The horizontal axis of each figure is the sensor position (FL, FR, RR, RL from the left), and the vertical axis is the amount of strain.

[0014] The position of the foreign object was identified from the measurement values ​​shown in Figure 4. First, the longitudinal position is calculated from the difference between the total strain amount of the two front sensors (FL, FR) and the total strain amount of the two rear sensors (RR, RL). The calculation formula is shown in Equation 1. (Formula 1) TIFF2025182779000002.tif754On the other hand, the left-right position is calculated from the difference between the total strain amount of the two left sensors (FL, RL) and the total strain amount of the two right sensors (FR, RR).The calculation formula is shown in Equation 2. (Formula 2) TIFF2025182779000003.tif755The results of these calculations for each shim position are shown in Figure 5. In Figure 5, the horizontal axis is the distance from the left edge of the lower die, and the vertical axis is the resultant strain calculated using Equations 1 and 2. In this experiment, the shim was placed at the midpoint in the front-to-back direction of the die, so the resultant strain εy in the front-to-back direction was always close to 0. On the other hand, the resultant strain εx in the left-to-right direction was a straight line running from the upper left to the lower right, demonstrating that the position of a foreign object on the die can be identified from these calculations.

[0015] Although a strain gauge is used in the above embodiment, it goes without saying that a load sensor can also be used for similar detection. [Explanation of symbols]

[0016] 1 Upper die set 2 Lower die set 3 Upper mold 4 Lower mold 5 Stripper plate 6 Stroke end 6a Stroke end (FL) 6b Stroke end (FR) 6c Stroke end (RR) 6d Stroke end (RL) 10 sensors 11 Sensor wiring 20 Material to be molded 30 Foreign object (shim)

Claims

1. A method for detecting foreign matter in a press die, characterized by attaching a sensor to each of the stroke ends located at at least four corners of the die in a press apparatus, measuring the distance between each sensor and the stripper plate during the press stroke, and calculating the difference between the total measurement values ​​of the sensors located on the front side and the total measurement values ​​of the sensors located on the back side, and the difference between the total measurement values ​​of the sensors located on the left side and the total measurement values ​​of the sensors located on the right side, thereby identifying the position of the foreign matter on the die.

2. A method for detecting foreign matter in a press die, characterized in that a sensor is attached to each of the stroke ends located at at least four corners of the die in a press apparatus, the load received by each sensor through the stripper plate during the press stroke is measured, and the location of the foreign matter on the die is identified by calculating the difference between the total measurement values ​​of the sensors located on the front side and the total measurement values ​​of the sensors located on the back side, and the difference between the total measurement values ​​of the sensors located on the left side and the total measurement values ​​of the sensors located on the right side.

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