JP7526474B2 - Die life sensor - Google Patents

Description

The present invention relates to a sensor capable of detecting the end of life of a die used in press forming such as forging, drawing, and punching.

There are presses as devices for forming metal materials and the like by processing such as forging, drawing, and punching. In these presses, dies are used to form metals and the like. For example, in forging devices, the die tool maintenance cycle, such as checking the accuracy of dies and re-polishing, is determined based on the experience accumulated at the processing site, and the maintenance timing is generally often managed by the number of processing shots. In forging processing, which has a high processing load, tool damage such as cracking and chipping may occur. The timing of damage varies from a few shots to hundreds of thousands of shots. In a progressive die including multiple pressing processes in one die set, if tool damage occurs and processing is continued as it is, it will have a large impact on other processes, so it is necessary to stop processing immediately when tool damage is detected. It is difficult to predict how durable a tool actually is and how long it will last until it breaks, and there is a need to develop a method that can predict or detect the lifespan in a simple manner.

For example, Patent Document 1 discloses a die wear amount prediction device that includes a mechanical load calculation means for calculating a mechanical load, which is an aggressive element for the die, a thermal degradation strength calculation means for calculating a thermal degradation strength due to repeated application of high temperatures, which is a strength degradation element for the die, and a wear amount calculation means for calculating a predicted wear amount by calculating a wear amount calculation formula, which is a function of the calculated mechanical load and the calculated thermal degradation strength. This device requires a computer to perform complex calculations, which makes it expensive.

Patent Document 2 discloses a life management device for forging parts, comprising a life management main body and a forging number display which is detachably attached to the main body and displays the number of forgings of forging parts such as forging dies, die sets, and forging tools in a forging machine, the life management main body having a display plate which clearly indicates the names of the forging parts and their predicted lives, an attachment section for the forging number display which is provided corresponding to the predicted lives of the forging parts, and a receiving circuit which receives a forging operation detection signal during the forging operation of the forging machine, while the forging number display has a forging number display section which displays the forging number, an attachment means for attaching the forging number display to the attachment section of the life management main body, a counting circuit which is connected to the receiving circuit when the forging number display is attached to the life management main body, and which automatically adds and inputs the forging number to the display section when a forging operation detection signal is input to the receiving circuit, and an attachment means for removing the forging number display from the life management main body and detachably attaching it to forging parts such as forging dies, die sets, and forging tools. This device has a complex structure and also manages the die life basically by counting the number of forgings, so that it is difficult to use in cases where the die life cannot necessarily be predicted by the number of shots, such as in forging devices.

JP 2002-321032 A Utility Model Registration No. 3137672

In view of the above-mentioned problems, the present invention has an objective of providing a mold life sensor that can reliably detect damage to a mold using simple electrical information by attaching a simple sensor to the mold.

In order to solve the above problems, the die life sensor of the present invention is characterized in that it comprises a conductive band portion formed around a hollow portion of a die used for metal press molding and protected by a non-conductor portion , a conductor wire drawn out from both ends of the conductor band portion, and an electrical characteristic measuring means connected to the conductor wire .

It is preferable that a plurality of the conductor band portions are arranged such that the lead-out portions of the conductor wires are shifted from one another.

In the mold life sensor according to the present invention, a conductive band portion insulated from the mold body is formed around the cavity of the mold, and electrical characteristic values such as the resistance value of this conductive band portion are measured. When the mold is damaged, the conductive band is cut or damaged, causing a change in the characteristic value, so that damage to the mold can be detected. The conductive band portion requires a slight distance between both ends to pull out the conductor. Therefore, if the conductive band portion is a single unit, there is a risk that the mold cannot be detected if it is damaged at this part. Therefore, it is possible to form the conductive band in a single stroke with some parts overlapping each other to cover the entire periphery of the cavity, and it is also possible to arrange multiple conductive band portions with a slight shift in the pull-out parts. This makes it possible to detect damage regardless of where it occurs around the mold cavity.

A preferred embodiment of the present invention will be described below based on the examples. FIG. 1 shows a schematic cross-sectional view of an example of a forging die according to the present invention. (a) is a schematic view before processing, and (b) is a schematic view during processing. In (a), a die plate 11 is placed on a backing plate 30, and a die 10 having a cavity 12 hollowed out in a shape for forging is fitted in the center of the die plate 11. A sensor unit 20 is formed around the side of the die 10 over almost the entire circumference. A counter 31 is placed at the bottom of the cavity 12, and a workpiece 40 is placed on the counter 31. A punch 1 is placed above the cavity 12. (b) shows the state when the punch 1 descends. The punch 1 descends into the cavity 12 of the die 10, and the workpiece 40 is formed along the clearance formed between the punch 1 and the die 10. The punch 1 descends to the bottom dead center and then ascends again. At this time, the counter 31 also rises with some delay, and the formed workpiece 40 is discharged from the cavity 12 .

A side cross-sectional view of the die 10 equipped with a sensor unit 20 is shown in Fig. 2. The sensor unit 20, which is made of a conductive band 21 surrounded by a non-conductive protective layer 22, is embedded in the side of the die 10. Although not shown in Figs. 1 and 2, the conductive band 21 is formed over almost the entire circumference of the side of the die 10, and conductors are drawn from both ends of the conductive band 21 and connected to an electrical resistance measuring means. The die 10 is generally made of cemented carbide or high-speed steel, which are conductors, so the conductive band 21 is provided with a non-conductive protective layer 22 to insulate it from the tool body.

If the die 10 is damaged during the forging process, the conductive band 12 is cut, and the electrical characteristic value changes, making it possible to detect the damage to the die.

3 shows an embodiment in which the die life sensor according to the present invention is applied to a die for drawing. (a) is a schematic diagram before processing, and (b) is a schematic diagram during processing. The basic component configuration is the same as that of the forging processing in FIG. 1, but in the case of drawing, the counter 31 is placed on the same surface as the surface of the die 10 before processing. The workpiece 40 is placed on the surface of the die 10. In this processing, after the punch 1 descends and contacts the surface of the workpiece 40, the counter 31 also descends in a manner that supports the workpiece 40 to be formed. The workpiece 40 is formed along the clearance formed between the punch 1 and the die 10, as in the case of forging.

FIG. 4 shows an embodiment in which the die life sensor according to the present invention is applied to a die for punching. (a) is a schematic diagram before processing, and (b) is a schematic diagram during processing. The basic component configuration is the same as that of the drawing processing shown in FIG. 3, and the workpiece 40 is placed on the surface of the die 10. The difference is that the backing plate 30 continuing from the die 10 also has a cavity 32, and there is no counter 31. When the punch 1 descends and enters the cavity 12 of the die 10, it cuts out the workpiece 40 and pushes it directly into the cavity 12. After the punch 1 rises, the workpiece 40 is transported and a new surface is placed on the die 10. By repeating this operation, continuous punching is performed.

A perspective view of the die plate 11 and die 10 used in the above embodiment is shown in FIG. 5. The method of forming the sensor unit 20 shown here will be described. The process is shown in FIG. 6. 1) A groove is formed around the side of the die 10 by grinding or the like. The width of the groove is about 2 mm, and the wall surface of the groove is inclined at about 45 degrees. 2) A non-conductive layer is first formed in the groove by thermal spraying, and then a conductor layer is formed. The thickness of each layer is 50 to 100 μm. 3) The conductor layer and the non-conductive layer are removed by grinding to a part slightly below the surface of the groove. 4) A non-conductive layer is formed in the groove again by thermal spraying. 5) Finally, a part of the non-conductive layer is removed by grinding or the like so that the surface of the groove is the same as the surface of the tool body. Ceramics or the like can be used as the non-conductive layer.

In the above embodiment, the sensor unit is described as being single, but the two ends of the sensor unit are slightly separated in order to pull out the conductor from the conductor band. Therefore, if damage to the tool occurs in this area, it may not be possible to detect it. To solve this problem, it is possible to form the conductor band in a single stroke with a part overlapping so as to cover the entire periphery of the cavity, and it is also possible to arrange two rows of sensor units with the conductor pull-out part slightly shifted. With these measures, it becomes possible to detect damage in any part around the tool. In addition, in the above embodiment, the sensor unit is arranged on the side of the mold, but the position does not matter as long as it is around the cavity.

As described above, in the mold life sensor according to the present invention, a conductive band portion insulated from the mold body is formed around the side surface of the mold, and the electrical characteristic value of this conductive band portion is measured, so that damage to the mold can be detected by the change in characteristic value due to the conductive band being cut or damaged when the mold is damaged. The conductive band portion requires a slight distance between both ends to allow the conductor to be drawn out. Therefore, if the conductive band portion is a single unit, there is a risk that damage to the mold cannot be detected if it occurs at this part. Therefore, by arranging multiple conductive band portions with a slight offset, it becomes possible to detect damage regardless of where it occurs in the mold.

1 is a schematic cross-sectional view showing an embodiment of a forging die according to the present invention. FIG. 2 is a cross-sectional view showing details of a sensor provided on a die of the forging die shown in FIG. 1 . 1 is a schematic cross-sectional view showing an embodiment of a drawing die according to the present invention. FIG. 1 is a schematic cross-sectional view showing an embodiment of a punching die according to the present invention. FIG. 1 is a perspective view showing a mold provided with a sensor according to the present invention. 1A to 1C are explanatory diagrams showing a process for manufacturing a sensor using a mold according to the present invention.

Reference Signs List 1 punch 10 die 11 die plate 12 cavity 20 sensor portion 21 conductive band 22 non-conductive protective layer 30 backing plate 31 counter 40 workpiece

Claims (2)

A die life sensor comprising a conductive band portion formed around a hollow portion of a die used in metal press molding and protected by a non-conductive portion, conductive wires drawn out from both ends of the conductive band portion, and an electrical characteristic measuring means connected to the conductive wires . 2. The mold life sensor according to claim 1, wherein the conductive band portion is arranged in a plurality of portions with the lead-out portions of the conductive wires offset from one another.