Method for monitoring the removal of sheet metal waste from a sheet metal working tool and device for this purpose

Abstract

Method for monitoring the removal of sheet metal waste from a sheet metal working tool (1), wherein the sheet metal waste is produced by trimming and / or punching a sheet metal part (5) that has been heated at least section by section beforehand and comprises at least one sheet metal waste piece (6) and / or sheet metal waste fragment (7), which is removed from the sheet metal working tool (1) by means of part-specific accessories, and wherein, after removal of the processed sheet metal part (5) and the at least one sheet metal waste piece (6) and / or sheet metal waste fragment (7) from the sheet metal working tool (1), a temperature distribution in the sheet metal working area of ​​the sheet metal working tool (1) is thermographically recorded and the resulting thermal image (8) is evaluated and assessed with regard to any sheet metal waste piece(s) (6) and / or sheet metal waste fragment(s) (7) remaining in the sheet metal working tool (1).

Description

[0001] The invention relates to a method for monitoring the removal of sheet metal waste from a sheet metal processing tool according to the combination of features of claim 1 of the invention. According to claim 9 of the invention, the same further relates to a device for carrying out said method.

[0002] DE 10 2012 002 468 A1 describes a sheet metal processing tool for cutting a shaped sheet metal part, comprising an upper tool part and a lower tool part. The shaped sheet metal part to be cut is arranged between the upper and lower tool parts and is cut by closing the tool parts. During cutting, at least one piece of sheet metal waste is created, which is first lifted by a rocker device of the sheet metal processing tool and then moved away from the cutting location by sliding due to gravity. EP 2 583 769 B1 describes a device and a method for hot forming / press hardening and cutting and / or punching a sheet metal material with automated removal of the sheet metal waste. Essentially, the sheet metal waste part, which has a temperature of up to 650°C, is moved to a defined transfer position after trimming and / or punching, from which it can be reliably picked up by a gripper and removed from the tool.Notwithstanding the measures described above for removing said sheet metal waste, it cannot be ruled out that, in particular, sheet metal waste fragments, i.e., small and / or minute pieces of waste resulting from trimming, or resulting contamination, may remain in sensitive areas of the sheet metal processing tool, particularly in the molds of the upper and / or lower tool sections, or may be transported into said areas by the automation of the sheet metal processing tool, thus adversely affecting the quality of the subsequently formed sheet metal part and / or leading to damage to the sheet metal processing tool. Such small and / or minute pieces of waste arise, for example, from insufficient trimming and / or entrainment. This is where the invention described below comes into play.

[0003] EP 1 060 830 A1 discloses a device and method for hot forming (in particular press hardening) and cutting sheet metal. The device consists of a tool with two tool parts, between which the heated sheet metal is formed. After forming, the sheet metal is trimmed and / or punched while still warm using a cutting device. The sheet metal waste can be removed automatically. A movable gripper removes the warm sheet metal waste pieces after they have been placed in a defined position within or next to the tool.

[0004] DE 102011 116 715 A1 describes a device and method for the thermographic examination of functional surfaces on forming tools. A channel with a window is integrated into the tool. The heat radiation from the functional surface is guided through the channel to a temperature measuring device, such as a thermal camera. This allows for a quick and easy determination of the temperature distribution during the forming process.

[0005] The object of the invention is to provide a method for monitoring the removal of sheet metal waste from a sheet metal processing tool, by means of which the adverse effects of the above-described circumstance can be prevented or at least significantly reduced. Furthermore, the object of the invention is to provide a suitable device for carrying out said method.

[0006] The stated object is therefore initially achieved by a method for monitoring the removal of sheet metal waste from a sheet metal processing tool, wherein the sheet metal waste is produced by trimming and / or punching a sheet metal part that has been heated at least in sections beforehand and comprises at least one piece of sheet metal waste and / or sheet metal waste fragment that is removed from the sheet metal processing tool by means of part-specific accessories, and wherein after removal of the processed sheet metal part and the at least one piece of sheet metal waste and / or sheet metal waste fragment from the sheet metal processing tool, a temperature distribution in the sheet metal processing area of ​​the sheet metal processing tool is thermographically recorded and the resulting thermal image is evaluated and assessed with regard to any piece(s) of sheet metal waste and / or sheet metal waste fragment(s) remaining in the sheet metal processing tool.

[0007] The method according to the invention enables reliable detection of any remaining sheet metal waste pieces and / or sheet metal waste fragments in the sheet metal processing tool, to which a suitable response can then be made, for example by preventing or stopping the loading of the sheet metal processing tool with a new sheet metal part to be processed and cleaning the sheet metal processing tool of said remaining sheet metal waste pieces and / or sheet metal waste fragments. A sheet is understood to be a flat finished metal rolled product, a sheet metal blank, or a formed sheet metal part that undergoes at least one sheet metal processing step, in particular by trimming and / or punching. Essentially, temperature differences between the remaining trimming residue in the form of said sheet metal waste pieces and / or sheet metal waste fragments and the tool are detected.

[0008] The subclaims describe preferred developments or embodiments of the invention.

[0009] A preferred and particularly simple, functionally reliable, and automated development of the method according to the invention results from the fact that the resulting thermal image is compared with a reference thermal image of the sheet metal processing area of ​​the sheet metal processing tool without any sheet metal waste piece and / or sheet metal waste fragment, wherein the occurrence of a deviation or a trend of a deviation from the reference thermal image is used to assess the thermal image. In this context, it proves particularly expedient for the resulting thermal image to be computer-aided and evaluated with the aid of thermography software. The said method can be used particularly advantageously when using a forming tool with sheet metal trimming and / or sheet metal perforation for hot or semi-hot forming of the sheet metal part, since particularly easily detectable heat differences occur here.The working temperature during hot forming is above the recrystallization temperature, for pure iron above 450°C. This causes recrystallization during forming, which counteracts the hardening of the sheet metal material in question. In contrast, during semi-hot forming, the sheet metal workpiece is heated to a temperature below the aforementioned recrystallization temperature, thus combining the advantages of hot forming—namely, easier formability and greater formability—with the advantages of cold forming—namely, hardening and greater precision. It is self-evident to the skilled person that, in this case as well, the temperature of the sheet metal to be processed must be selected so that any pieces of sheet metal waste and / or fragments remaining in the tool can be detected by creating a sufficiently high temperature difference between the pieces and the tool.A further advantageous development of the method according to the invention results from the fact that a cooled forming tool is used as the sheet metal working tool, wherein the forming tool is not cooled in the area of ​​the potential sheet metal waste of the sheet metal part. As a result, a particularly high and therefore very easily detectable temperature difference can be achieved between any sheet metal waste pieces and / or sheet metal waste fragments remaining in the tool and the tool. The method according to the invention can also be used on a sheet metal working tool in the form of a forming tool with sheet metal trimming and / or sheet metal perforation for cold forming the sheet metal part, wherein at least the potential areas of the sheet metal waste of the sheet metal part are heated beforehand. This means:Any sheet metal waste pieces and / or fragments that may be created or remain in the tool have a higher temperature than the tool, which results in the required temperature difference for detection. A conventional thermographic camera has proven particularly advantageous for thermographic recording of the temperature distribution in tests. This can, for example, be equipped with a thermal sensor in the form of a so-called microbolometer detector for detecting infrared radiation above 5 µm wavelength. Alternatively, a thermographic camera in the form of an NIR camera (NIR = near infrared) for detecting infrared radiation from 780 nm to 3 µm wavelength can be used.

[0010] The invention also relates to a device with a thermographic camera for carrying out the above-described method according to the invention.

[0011] The invention is explained in more detail below using an exemplary embodiment schematically illustrated in the drawings. However, it is not limited to this embodiment, but encompasses all embodiments defined by the patent claims. They show: Fig. 1 extremely schematic sectional view of a sheet metal working tool equipped with a sheet metal part which is to be formed and trimmed, Fig. 2 the sheet metal working tool Fig. 1 after sheet metal processing, Fig. 3 the sheet metal working tool Fig. 1 and Fig. 2 after removal of the machined sheet metal part and resulting sheet metal waste pieces and / or sheet metal waste fragments, with a thermographic camera for carrying out the method according to the invention, and Fig. 4 shows very schematically the contours of a sheet metal waste fragment detected by the thermographic camera and identified for evaluation in a resulting thermographic image.

[0012] Fig. Figure 1 initially shows a sheet metal processing tool 1, which, according to this exemplary embodiment, comprises a forming tool 2 with an upper tool 2a having an upper shape 3a and a lower tool 2b having a lower shape 3b. The forming tool 2 is designed for simultaneous trimming in that, according to this exemplary embodiment, the upper tool 2a is assigned a rotating upper blade 4a, which corresponds to a likewise rotating lower blade 4b assigned to the lower tool 2b.

[0013] The sheet metal processing tool 1 is equipped with a sheet metal part 5, in this case a sheet metal blank, arranged between the upper and lower tools 2a, 2b. The sheet metal part 5 is formed by hot forming and is therefore heated above the recrystallization temperature of the metal used for the sheet metal part 5. In this case, the forming tool 2 has cooling means (not shown in the drawing), in particular cooling channels through which a cooling medium flows. As shown in Fig. 1, the upper and lower tools 2a, 2b have already moved so far towards each other that the upper and lower blades 4a, 4b are supported on the sheet metal part 5.

[0014] Are in accordance with Fig. 2 As the upper tool 2a and the lower tool 2b move further toward each other, the outer contour of the sheet metal part 5 is trimmed by means of the upper and lower blades 4a, 4b. At the same time, the trimmed sheet metal part 5 undergoes a forming process into a shaped sheet metal part and a cooling process.

[0015] The sheet metal waste pieces 6 separated from the edge area of ​​the sheet metal part 5 are removed from the forming tool 2 after removal of the formed and trimmed sheet metal part 5 using part-specific accessories (not shown in the drawing), such as suction devices, clamping grippers, and / or the like, and removed accordingly. If sheet metal waste fragments 7 (see Fig. 4) as small and / or tiny pieces of waste, which arise, for example, from insufficient trimming and / or entrainment, these are also removed using the part-specific accessories in accordance with an optimal process control.

[0016] Irrespective of this, as already explained in the introduction, it cannot be ruled out that in particular sheet metal waste fragments 7, i.e. small and / or very small parts of the sheet metal waste resulting from the trimming or the resulting contamination, may nevertheless remain in sensitive areas of the sheet metal processing tool 1 or forming tool 2 with trimming, in particular in the shapes 3a, 3b of the upper and / or lower tool 2a, 2b, or may be brought into said areas by the automation of the sheet metal processing tool 1 and thus adversely affect in particular the quality of any subsequently formed sheet metal part 5 and / or lead to damage to the sheet metal processing tool 1.

[0017] In order to prevent this disadvantageous circumstance, after removal of the machined sheet metal part 5 and the said sheet metal waste pieces 6 and / or sheet metal waste fragments 7 from the sheet metal processing tool 1 or forming tool 2 with trimming, it is provided that a temperature distribution in the sheet metal processing area of ​​the sheet metal processing tool 1 is recorded thermographically and the resulting thermal image 8 is evaluated and assessed with regard to any sheet metal waste pieces 6 and / or sheet metal waste fragments 7 remaining in the sheet metal processing tool 1 (cf. Fig. 3).

[0018] If remaining sheet metal waste pieces 6 and / or sheet metal waste fragments 7 are detected in the sheet metal processing tool 1, in this case in the forming tool 2 with trimming, in particular in the area of ​​the upper and / or lower tool 2a, 2b thereof, a suitable response can be made, for example by preventing or stopping the loading of the sheet metal processing tool 1 with a new sheet metal part 5 to be processed and by cleaning the sheet metal processing tool 1 of said remaining sheet metal waste pieces 6 and / or sheet metal waste fragments 7. This advantageous measure results from the knowledge that the remaining sheet metal waste pieces 6 and / or sheet metal waste fragments 7 have a higher temperature than the sheet metal processing tool 1 or forming tool 2 with trimming.

[0019] Fig. 4 shows, in a highly schematic manner, the contours or outlines of a sheet metal waste fragment 7 detected by the thermographic camera and identified for evaluation in a resulting thermographic image or thermal image 8. In general, however, with a thermographic image, the said sheet metal waste fragment 7 is identified by a bright area against a dark background (not shown graphically), so that the contours or outlines are very clearly visible to the observer. The said bright area therefore corresponds to an area that is warmer or hotter than the surroundings. It has proven particularly advantageous if, during the process, a temperature difference of ≥ 25°C between the sheet metal processing tool 1 and the sheet metal waste piece 6 and / or sheet metal waste fragment 7 is ensured and the forming tool 2 is not cooled in the area of ​​the potential sheet metal waste.

[0020] Via a signal 9 to a computer-aided control unit 10 (CPU) of the sheet metal processing tool 1, which in turn generates a control signal 11 to the sheet metal processing tool 1, the loading of the tool with a new sheet metal part 5 to be formed and trimmed can be stopped, thus preventing poor-quality processing of this sheet metal part 5 and / or damage to the sheet metal processing tool 1. According to this exemplary embodiment, a thermographic camera 12 is used for thermographic recording of the said temperature distribution (see FIG. Fig. 3). This can, for example, be equipped with a thermal sensor in the form of a so-called microbolometer detector for detecting infrared radiation above 5 µm wavelength. Alternatively, a thermographic camera 12 in the form of an NIR camera (NIR = near infrared) can be used to detect infrared radiation from 780 nm to 3 µm wavelength.

[0021] It has also proven advantageous if the resulting thermal image 8 is compared with a reference thermal image of the sheet metal processing area of ​​the sheet metal processing tool 1 without any sheet metal waste piece 6 and / or sheet metal waste fragment 7, wherein the occurrence of a deviation or a trend of a deviation from the reference thermal image is used to assess the thermal image 8. In this context, it has proven particularly expedient for the resulting thermal image 8 to be computer-aided and evaluated with the aid of thermography software integrated into the control unit 10 of the sheet metal processing tool 1, and for the control unit 10 of the sheet metal processing tool 1 to automatically generate a corresponding control signal 11 or stop signal upon detection of a load.

[0022] The embodiment described above is essentially based on edge trimming of the sheet metal part 5. Naturally, the invention encompasses any trimming, including perforation (not shown in the drawing). In this case, it is advisable to exclude cooling of the forming tool 2 in this area to ensure the necessary temperature difference for detection.

[0023] Furthermore, the invention also encompasses a sheet metal part 5 which is semi-hot formed according to the invention. Semi-hot forming means that the sheet metal workpiece or sheet metal part 5 is heated to a temperature below said recrystallization temperature, thereby combining the advantages of hot forming, namely easier formability and greater formability, with the advantages of cold forming, namely hardening and greater precision. In this case, in order to carry out the method according to the invention, it is of course necessary to ensure that the temperature of the sheet metal part 5 to be processed is such that it enables thermographic detection of sheet metal waste pieces 6 and / or sheet metal waste fragments 7 remaining in the sheet metal processing tool 1.

[0024] The method according to the invention can also be used on a sheet metal processing tool 1 in the form of a forming tool 2 with sheet metal trimming and / or sheet metal perforation for cold forming the sheet metal part 5, in that the potential areas of the sheet metal waste of the sheet metal part 5 are heated beforehand. This means that any sheet metal waste pieces 6 and / or sheet metal waste fragments 7 that are created and remain in the sheet metal processing tool 1 then have a higher temperature than the sheet metal processing tool 1, resulting in the required temperature difference for detection.

[0025] If no forming of the sheet metal part 5, be it a blank or an already formed sheet metal part 5, but merely trimming thereof is desired, it may also be advantageous in this case to detect any sheet metal waste pieces 6 and / or sheet metal waste fragments 7 remaining in the sheet metal processing tool 1 using the method according to the invention and subsequently dispose of them, which is accordingly also covered by the invention. In this case, the sheet metal part 5 to be processed or trimmed must be heated to a temperature that is detectable according to the method, for example ≥ 25°C of the tool temperature to be recorded. This measure can, for example, prevent damage to the sheet metal processing tool 1 (not shown in the drawing). List of reference symbols 1 sheet metal working tool 2 forming tool 2a Upper tool 2b Lower tool 3a upper form 3b lower form 4a Upper blade 4b Lower blade 5 sheet metal part 6 sheet metal waste pieces 7 Sheet metal waste fragment 8 Thermal image 9 Signal 10 Control and regulation unit 11 Control signal 12 thermal imaging cameras

Claims

[1] Method for monitoring the removal of sheet metal waste from a sheet metal processing tool (1), wherein the sheet metal waste is produced by trimming and / or punching a sheet metal part (5) which has been heated at least in sections beforehand and comprises at least one sheet metal waste piece (6) and / or sheet metal waste fragment (7) which is removed from the sheet metal processing tool (1) by means of part-specific accessories, and wherein after removal of the processed sheet metal part (5) and the at least one sheet metal waste piece (6) and / or sheet metal waste fragment (7) from the sheet metal processing tool (1), a temperature distribution in the sheet metal processing area of the sheet metal processing tool (1) is recorded thermographically and the resulting thermal image (8) is evaluated and assessed with regard to any sheet metal waste piece(s) (6) and / or sheet metal waste fragment(s) (7) remaining in the sheet metal processing tool (1). [2] Method according to claim 1, characterized bythat the resulting thermal image (8) is compared with a reference thermal image of the sheet metal processing area of the sheet metal processing tool (1) without any sheet metal waste piece (6) and / or sheet metal waste fragment (7), wherein an occurrence of a deviation from the reference thermal image is used to assess the thermal image (8). [3] Method according to claim 1 or 2, characterized by that the resulting thermal image (8) is evaluated and assessed using computer-aided thermography software. [4] Method according to one of claims 1 to 3, characterized by that a forming tool (2) with sheet metal trimming and / or sheet metal perforation is used as the sheet metal processing tool (1) for hot or semi-hot forming of the sheet metal part (5). [5] Method according to claim 4, characterized bythat a cooled forming tool (2) is used as the sheet metal processing tool (1), wherein the forming tool (2) is not cooled in the area of the potential sheet metal waste of the sheet metal part (5). [6] Method according to one of claims 1 to 3, characterized by that a forming tool (2) with sheet metal trimming and / or sheet metal perforation is used as the sheet metal processing tool (1) for cold forming the sheet metal part (5), wherein at least the potential areas of the sheet metal waste of the sheet metal part (5) are heated beforehand. [7] Method according to one of claims 1 to 6, characterized by that a thermographic camera (12) is used for thermographic recording of the temperature distribution. [8] Method according to claim 7, characterized bythat a thermographic camera (12) with a thermal sensor in the form of a microbolometer detector for detecting infrared radiation above 5 µm wavelength or a thermographic camera (12) in the form of an NIR camera for detecting infrared radiation from 780 nm to 3 µm wavelength is used. [9] Device with a thermographic camera (12) for carrying out the method according to one of claims 1 to 8.

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