LOADING METHOD FOR A MACHINE TOOL

Description

[0001] The invention relates to a loading method for a machine tool, in particular for a bending machine.

[0002] Machine tools usually have a machine frame in which work equipment is arranged that can apply a machining force to a workpiece in order to form it. In order to enable the application of force to be tailored to the workpiece, the work equipment usually has tool holders in which specifically designed machining tools can be inserted or arranged. To carry out the individual machining steps, it is necessary to exchange the machining tools or to change their position. This is usually done by unlocking the tool holder so that the machining tools arranged therein can be manipulated. In a bending machine, the tool holder is straight and extends over the entire length of the press beam. If the machining tools need to be reconfigured manually, the machine operator must grasp each individual machining tool and remove or insert it from the tool holder.in the tool holder. This is easily possible with small tools for machining light materials, such as thin sheet metal, but with tools for machining heavy components, it requires considerable effort or is no longer possible manually.

[0003] Systems and devices are known in which processing tools (hereinafter referred to as bending tools) are gripped and removed or moved from the front or from the interior of the bending machine by means of a gripper. However, this requires a manipulation robot, which may perform manipulation actions in the front area of ​​the machine, while ensuring that no persons are endangered by the manipulation actions. It is also known to push a package of inserted bending tools from the tool holder onto a receiving device arranged laterally along the length of the press beam by means of an ejection device, after which this receiving device is moved into a parking position or into a tool storage area.

[0004] However, such systems are usually characterized by great complexity and usually require major modifications or additions to the machine.

[0005] A further possibility is disclosed in EP 2946846 A1, which presents a tool changing device for a forming press with a tool magazine and a transfer device for transferring the forming tools from the tool magazine to the forming press. The transfer device comprises a drivable push chain. The transfer device further comprises a cable-connected electromagnet for coupling the forming tools.

[0006] There are also changing devices which are based on the fact that the machining tools used are usually made of metal and can therefore be held in place by a magnet. For this purpose, a small holding carriage is moved along the tool holder towards the machining tool. Thanks to the magnet arranged in the holding carriage, it remains attached to the machining tool and can pull the tool along the tool holder or change its position. When an end position is reached, the magnetic holding force is released, causing the machining tool and holding carriage to separate from each other. The disadvantage of this, however, is that the acting magnetic field causes residual magnetism to build up in the metallic object, particularly in the machining tool and also in the changing carriage. This can lead to machining tools sticking to one another and making it difficult or impossible to separate.Furthermore, metallic deposits, such as those that occur when machining metal workpieces, can build up on the machining tools and the change slide. It can also happen that the magnetized machining tools attract a light sheet of metal being machined, which can change the alignment of the workpiece relative to the machine tool and thus result in incorrect machining of the workpiece.

[0007] The object of the invention is to provide a method and a compact device which enables the manipulation of metallic machining tools in a machine tool, wherein the manipulation actions have no effect on the intended use of the machining tools in the machine tool or on the changing device.

[0008] This object is achieved by a method according to the claims.

[0009] In particular, the object of the invention is achieved by a loading method for a machine tool, in particular for a bending machine. The machine tool comprises a tool transfer device, a tool holder, and a tool rest. The tool holder and the tool rest are connected via a guideway, and the tool transfer device is arranged to be movable along the guideway. Machining tools, in particular bending tools, are arranged in the tool holder and / or in the tool rest. Furthermore, the tool transfer device has a magnetic holding device. In one step, the tool transfer device is moved to a machining tool, which machining tool is arranged in a receiving position in the tool holder or in the tool rest.The machining tool is then picked up and held by a magnetic holding device of the tool transfer device, and the picked-up machining tool is moved along the guideway to a release position in the tool rest or tool holder. There, the machining tool is released by removing the magnetic holding force. The magnetic holding device has an electromagnet with an electronic control device, and when the magnetic holding force is removed, the control device performs demagnetization.

[0010] This design advantageously ensures that no residual magnetism remains in the machining tool due to the magnetic mounting and holder. Any residual magnetism that may exist is also reduced or eliminated. This prevents disruption to the workflow caused by metallic (dirt) particles or by light metal parts being machined adhering to the machining tool due to residual magnetism.

[0011] A further development involves applying an alternating electrical current with a decreasing signal amplitude to the electromagnet when the holding force is released. For example, the alternating current, which is by definition free of DC components, can have a sinusoidal waveform. However, other signal shapes are also conceivable.

[0012] According to a further development, it is also provided that the magnetic holding device, in particular the electromagnet, additionally comprises a permanent magnet, wherein, when the holding force is removed, the electromagnet is subjected to an electrical alternating signal with a DC component and a decreasing signal amplitude by the control device. The advantage of this design is that the energy required to control the electromagnet is reduced, since a permanent magnetic field is always available, onto which the magnetic field of the electromagnet is superimposed. To cancel the magnetic field, the control signal must therefore have a DC component, which generates a magnetic field that is equal to the strength of the permanent magnet but has the opposite field direction. Thus, the two field components cancel each other out, and the resulting field is zero. A sinusoidal alternating current can also be used as the signal waveform.

[0013] The decreasing signal amplitude according to the two further developments will preferably decrease according to an exponential function, e.g., according to exp(-x). This achieves a very rapid reduction of a major portion of residual magnetism. By selecting the frequency of the alternating signal and the demagnetization duration, a very effective reduction of an existing magnetic field can be achieved.

[0014] When the machining tool is picked up, the control device sends an electrical pick-up and hold signal to the electromagnet.

[0015] The control device switches the strength of the pick-up and hold signal between a first signal strength when the machining tool is picked up and a second signal strength when the machining tool is held. For example, it can be advantageous to pick up small and therefore lightweight machining tools with a low magnetic holding force to prevent a neighboring machining tool from also being attracted by the magnetic force. To save energy, the magnetic force can be reduced, for example, during movement along the guideway.

[0016] However, it is also possible to increase the magnetic force during movement to ensure secure holding at high driving speeds.

[0017] In this regard, according to a first alternative, it is advantageous that the second signal strength of the pick-up and hold signal is switched off when the machining tool is held. For example, if the machining tool is pushed by the transfer device, no magnetic force, or only a very small one, may be required to securely hold the machining tool in position. This, in turn, can reduce energy consumption and shorten the time the magnetic holding force acts on the machining tool, which in turn leads to lower residual magnetism.

[0018] An advantageous further development or alternative is to reduce the second signal strength of the pick-up and hold signal before reaching the release position. When approaching the pick-up or release position of small and therefore lightweight machining tools, it is advantageous to reduce the magnetic force before reaching the target position to prevent unwanted attraction of already positioned machining tools.

[0019] According to a further development, it is provided that an identification feature of the machining tool is read out by a detection means connected to the control device, and from this, tool characteristics are extracted by the control device, in particular a tool shape, a tool weight and / or a tool length. The characteristics can, for example, be stored directly in the identification feature. It is also possible for the identification feature to only contain a reference which has a connection to an entry in a characteristic data table. This table can be arranged in the transfer device, in particular in the control device. However, it is also possible for the table to be stored in a data processing system which is connected to the control device for data purposes, for example via a wireless data connection.

[0020] A further advantageous development consists in that, based on the extracted tool shape, the tool weight, and / or the tool length, the control device reads the first and / or second signal strength from a stored parameter table. The minimum magnetic force required to reliably pick up and hold the machining tool, as well as the maximum magnetic force to prevent a neighboring machining tool from also being picked up, depend significantly on the tool weight, the tool length, and the tool shape. Depending on this, different frictional resistances will arise between the tool holder and the tool, which directly influence the minimum required magnetic force. With this development, the appropriate magnetic holding force can be used for each individual machining tool.

[0021] According to a further development, the recording and hold signal is provided by the control device as a PWM (pulse width modulation) signal or as a PPM (pulse pause modulation) signal. Details of these signals are not listed here, as they are known to a person skilled in the art.

[0022] A further development consists in the tool transfer device having an electrical energy storage device connected to the control device and a charging contact connected to the energy storage device. After the tool transfer device has moved along the guideway into a parking position, the charging contact of the tool transfer device is connected to a charging connection in the waiting position. This development advantageously makes it possible to recharge the energy storage device of the tool transfer device during loading breaks, so that sufficient energy is available for the next loading process to pick up and hold, and in particular, to demagnetize, the machining tools.The presence of an energy storage device has the particular advantage that no energy supply cable is required, which allows for freer movement of the tool transfer device along the guideway.

[0023] A further development provides that the tool transfer device has a position sensor connected to the control device, which determines the position of the tool transfer device along the guideway and transmits the reaching of the pick-up position and / or the reaching of the release position to the control device. This development allows the control device to adjust the magnetic holding force along the path along the guideway in order to save energy on the one hand and to reduce the possibility of a magnetic field building up in the machining tool on the other.

[0024] Another advantageous development is that demagnetization is performed before reaching the dispensing position, particularly immediately before reaching the dispensing position. Since demagnetization requires some time, and since a magnetic holding force is still present at the beginning of demagnetization, demagnetization can be initiated as early as the last section of the path along the guideway, thus reducing the waiting time at the dispensing position until demagnetization is completed.

[0025] A tool transfer device for the loading process is also specified. This device comprises an outer housing, a guide device for receiving the transfer device in a guideway, and a magnetic holding device arranged at a front end of the housing. The magnetic holding device has an electromagnet, and a control device is also provided, which is designed to supply the electromagnet with an electrical demagnetization signal, which demagnetization signal is an alternating signal with a decaying amplitude.

[0026] A further development is that the outer housing has a power and / or data interface, which allows for a compact design of the transfer device. When designed as a power interface, the electromagnet or the control device can be powered by an external power supply. When designed as a data interface, the control device can also be externally located, or more selective control of the electromagnet is possible.

[0027] A further development now involves a rechargeable energy storage device within the housing, which is connected to a charging contact on the outside of the housing. This ensures that charging is possible without having to open the housing to access the energy storage device.

[0028] According to a further development, a connection device for a manipulator is also provided at a rear end of the housing. The tool transfer device in question can be part of a tool management device that, for example, serves multiple processing machines or machining stations. Here, there can be a central and universal manipulator that can be connected to the specific tool transfer device via the connection device.

[0029] A further development consists in the guide device having a drive configured to move the transfer device along the guideway. This allows for the realization of an independent tool transfer device that can independently perform tool manipulation while moving along the guideway.

[0030] According to a further development, the control device further comprises a table in which tool characteristics and associated parameters of a tool pick-up and holding signal are stored. By reading the table entries, the control device can obtain the parameters for generating the magnetic holding force in order to be able to reliably hold the machining tool, in particular the minimum holding force required for the tool weight or tool size and / or tool shape.

[0031] Another possible embodiment involves arranging a second electromagnet in a section of the guideway that is supplied with an alternating current of constant amplitude. As the transfer device moves past the second electromagnet, the transfer device becomes demagnetized, as the passing movement results in a decreasing amplitude of the magnetic force curve. For this purpose, the second electromagnet can be switched on by a machine control system precisely when the transfer device, in particular the front end of the housing, is located at the position of the second electromagnet.

[0032] For a better understanding of the invention, it is explained in more detail using the following figures.

[0033] They show in a highly simplified, schematic representation: Fig. 1 shows a block diagram of a tool transfer device; Fig. 2 shows a system comprising a machine tool, transfer device, and tool storage; Fig. 3 shows various possible operating modes of the tool transfer device; Fig. 4 shows another possible embodiment of the tool transfer device.

[0034] Fig. 1shows a tool transfer device 1 for use in the present loading method. The tool transfer device 1 has an outer housing 2, a guide device 3 for receiving the transfer device 1 in a guide track 4, and a magnetic holding device 5 arranged at a front end of the housing 2. The holding device 5 further has an electromagnet 6, which is connected to a control device 7, which is designed to supply the electromagnet 6 with an electrical demagnetization signal. Furthermore, a rechargeable energy storage device 8 is provided in the housing 2, which is connected to a charging contact 9 provided on an outer side of the housing. Furthermore, a connection device 10 for a manipulator is provided on the housing, in particular at a rear end and opposite the holding device 5.

[0035] Fig. 2shows a processing system 11 in which the loading process in question is carried out using a tool transfer device 1. The processing system 11 comprises a machine tool 12, in particular a bending machine, and a tool rest 13, which are connected to one another via a guideway 4, wherein the tool transfer device 1 is arranged to be movable along this guideway 4.

[0036] The machine tool 12 has a machine frame 14, which has a vertically movable press beam 15 and a fixed machine table 16. Further technical details of the machine tool 12, in particular a bending press, will not be discussed further here, as this does not contribute to the present loading method or the tool transfer device.

[0037] The present loading method is designed to move machining tools between a receiving and a delivery position. This is understood in particular to mean moving tools from a tool rest 13, as the receiving position, to the machine tool 12 as the delivery position, and, equivalently, moving tools from the machine tool 12 as the receiving position to the tool rest 13 as the delivery position. The latter situation is in Fig. 2 shown.

[0038] The machine table 16 has a tool holder 17 in which processing tools 18, in particular bending tools, are arranged. The press beam 15 also has a tool holder 17 in which processing tools 18 are also arranged.

[0039] In the tool holder 17, machining tools 18 are arranged at several machining positions 19, wherein the types can differ so that different machining operations can be carried out at the individual machining positions 19. To set up these machining positions 19, the machining tools 18 must now be removed from the tool holder 17 and placed in a tool rest 13 or, conversely, removed from the tool rest 13 and placed in the tool holder 17. For this purpose, the guideway 4 is arranged in the longitudinal direction of the tool holder 17 and thus forms a connection between the machine tool 12 and the tool rest 13. The tool transfer device 1 is movably arranged in this guideway, wherein it is moved in the guideway 4 by means of a manipulator arranged on the connecting device 10.It is also possible for the tool transfer device 1 to have drive means to enable it to move automatically along the guideway 4. Since the specific design is not relevant for the further discussion, it will not be discussed further here. Those skilled in the art are familiar with ways in which a tool transfer device can be moved along a guideway.

[0040] Since the energy storage device 8 of the tool transfer device 1 is preferably designed to be rechargeable for operating the control device 7 and the electromagnet of the holding device 5, it is provided that the tool transfer device 1 is moved to a waiting position during loading breaks, so that the charging contact 9 of the tool transfer device 1 is connected to a charging port 30 at the waiting position. Thus, the energy storage device 8 is automatically recharged during loading breaks.

[0041] Fig. 1shows the situation in which the tool transfer device 1 has picked up a machining tool 18 from the machining position 19. For this purpose, the tool transfer device 1 was brought to the pick-up position in the immediate vicinity of the arranged machining tool, and the magnetic holding device 5 was activated by the control device 7, thus creating a magnetic holding force between the transfer device 1 and the machining tool 18. In order to remove the bending tool from the tool holder 17, the latter must be unlocked or released by a machine control system. With the magnetic holding device 5 activated, the tool transfer device 1 moves the machining tool 18 along the guideway 4 to the delivery position, which in this case is the tool storage area 13.

[0042] The Fig. 3now shows various variants in which a machining tool 18 is picked up at a pick-up position 20 and moved along the guideway 4 to a delivery position 21, where it is delivered. The upper diagram shows the magnetic holding force 22, and the lower diagram shows the control current 23 with which the electromagnet of the tool transfer device is operated by the control device.

[0043] Fig. 3ashows the mounting of a small machining tool 18, where "small" means that the machining tool 18 is lightweight and, above all, short in the direction of the guideway 4. With such short tools, it is possible that when a large current is applied to the magnetic holding device 5, and a strong magnetic field is generated as a result, the bending tool to be mounted becomes magnetized, and a second bending tool arranged downstream is also held. Thus, there is a risk that, instead of the one tool to be mounted, two or possibly additional bending tools will undesirably stick to the magnetic holding device 5 of the tool transfer device 1.To prevent this, according to the illustrated embodiment, the electromagnet in a section 24 is supplied with a lower control current 23, thus generating a correspondingly lower magnetic holding force 22. As soon as the tool has been picked up and moved a certain distance away from the remaining arranged machining tools 18, the electromagnet of the holding device 5 is supplied with a higher control current 23 by the control device of the tool transfer device 1, which also increases the magnetic holding force 22. This means that the picked up tool is held well and firmly, thus enabling higher movement speeds along the guideway 4.

[0044] The action of the magnetic holding force 22 on the picked-up machining tool 18, as well as on the magnetic holding device 5, results in a build-up of residual magnetism. Without appropriate countermeasures, this residual magnetism would increase with each picking and holding process to such an extent that the tool and the holding device would have permanently magnetic properties, thus making reliable picking and unloading no longer possible. In particular, it may then happen that the machining tools 18 adhere to one another so strongly that they can no longer be separated from one another without additional mechanical separation assistance. Therefore, the loading method according to the invention provides for a demagnetization process to be carried out at the unloading position 21. This demagnetization process consists, for example, in the electromagnet of the magnetic holding device 5 being subjected to an alternating current 25 with decreasing amplitude.The decrease in amplitude will preferably follow an exp(-x) curve. At the end of the demagnetization process, any residual magnetic field in the tool or holding fixture will be eliminated or at least significantly reduced.

[0045] Fig. 3b shows a situation in which a small machining tool 18 is picked up at the pick-up position 20 and moved to the delivery position 21, wherein further machining tools 18 are already arranged at the delivery position 21. In order to prevent an existing bending tool at the delivery position 21 from being attracted to the bending tool picked up by the tool transfer device 1 by means of a magnetic holding force, it is also provided that in a section 24 before reaching the delivery position 21, the current is reduced by the control current 23 and thus the holding force 22.

[0046] Here too, when the dispensing position is reached, the magnetic holding force 22 is deactivated and demagnetization is carried out by applying an alternating current 25 to the electromagnet of the holding device 5.

[0047] Since in this case the machining tool 18 is pushed by the tool transfer device 1 along the guideway 4, according to a further embodiment it is also possible that already after the machining tool 18 has been picked up at the pick-up position 20, the magnetic holding force 22 is deactivated and the demagnetization is carried out and then the tool only rests on the tool transfer device 1 and is pushed by it to the delivery position 21.

[0048] In Fig. 4Further possible embodiments are shown. For example, a detection means 26 can be provided on the tool transfer device 1, which is connected to the control device 7 and which is designed to read out an identification feature 27 of the machining tool 18. From the read-out identification feature 27, the control device 7 can extract tool characteristics, in particular a tool shape, a tool weight and / or a tool length. In the control device 7, a table 28 can be provided, for example, in a storage means, in which table 28, parameters for the signal strength of the electrical control signal for supplying the magnetic holding device 5 are stored, based on the extracted tool weight, the tool size or the tool shape.

[0049] To determine the position of the tool transfer device 1 along the guideway 4, in particular to determine the pick-up or drop-off position, a position sensor 29 can also be provided with the control device 7. This position sensor 29 can, for example, detect or scan a marking arranged on the guideway 4 and determine a position therefrom.

[0050] The position sensor 29 can also be designed as a distance sensor and preferably be arranged at the front end of the housing 2. This allows the transfer device to automatically detect the approach of a tool, so that no additional devices or markings need to be provided on the guideway or the machine tool. The advantage of the present loading method or the present tool transfer device lies in particular in the fact that a simple and compact device enables rapid tool changes, in particular without the use of additional manipulators. Any reaction to the tool or the transfer device caused by the magnetism used can be prevented.

[0051] Finally, it should be noted that in the variously described embodiments, identical parts are provided with identical reference symbols or component designations, whereby the disclosures contained in the entire description can be applied mutatis mutandis to identical parts with identical reference symbols or component designations. Furthermore, the positional information chosen in the description, such as top, bottom, side, etc., refers to the directly described and illustrated figure, and these positional information must be applied mutatis mutandis to the new position in the event of a change in position.

[0052] The embodiments show possible variants, whereby it should be noted at this point that the invention is not limited to the specifically illustrated variants thereof.

[0053] The scope of protection is determined by the claims. However, the description and drawings are to be used to interpret the claims.

[0054] For the sake of clarity, it should finally be pointed out that, in order to better understand the structure, some elements have been shown out of scale and / or enlarged and / or reduced in size. Reference symbol list

[0055] 1Tool transfer device 2Outer housing 3Guide device 4Guide track 5Holding device 6Electromagnet 7Control device 8Energy storage device 9Charging contact 10Connection device 11Machining system 12Machine tool 13Tool rest 14Machine frame 15Press beam 16Machine table 17Tool holder 18Machining tool 19Machining position 20Pick-up position 21Release position 22Holding force 23Control current 24Section 25Alternating current 26Detecting means 27Identification feature 28Table 29Position sensor 30Charging connection

Claims

1. A loading method for a machine tool (12), in particular for a bending machine, having a tool transfer device (1), a tool holder (17) of the machine tool (12), and a tool rack (13), wherein the tool holder (17) and the tool rack (13) are connected via a guide track (4), and the tool-transfer device (1) is arranged so as to be movable along the guide track (4), and wherein machining tools (18), in particular bending tools, are arranged in the tool holder (17) and / or in the tool rack (13), and the tool-transfer device (1) has a magnetic holding device (5), and the magnetic holding device (5) has an electromagnet (6) with an electronic actuation device (7), comprising the steps: • moving the tool-transfer device (1) to a machining tool (18), which is arranged in a pick-up position (20) in the tool holder (17) or in the tool rack (13); • picking up and retaining the machining tool (18) by means of the magnetic holding device (5) of the tool-transfer device (1), wherein when the machining tool (18) is picked up, the electromagnet (6) is subjected to an electrical pick-up and retention signal by the actuation device (7); • moving the picked-up machining tool (18) along the guide track (4) to a deposition position (21) in the tool rack (13) or in the tool holder (17); • depositing the machining tool (18) by deactivation of the magnetic retaining force (22); characterized in that upon deactivation of the magnetic retaining force (22), a demagnetization is performed by the activating device (7), and that the strength of the pick-up and retention signal of the activating device (7) is changed over between a first signal strength for the pick-up of the machining tool (18) and a second signal strength for the retention of the machining tool (18), and that, for the retention of the machining tool (18), the second signal strength of the pick-up and retention signal is disconnected and / or the second signal strength of the pick-up and retention signal is reduced prior to reaching of the deposition position (21).

2. The loading method according to claim 1, characterized in that the electromagnet (6), during deactivation of the retaining force (22) is subjected, by the actuation device (7), to an electrical alternating current (25) having a decreasing signal amplitude.

3. The loading method according to claim 1 or 2, characterized in that the magnetic holding device (5) additionally has a permanent magnet, wherein the electromagnet (6), during deactivation of the retaining force (22), is subjected, by the actuation device (7), to a direct-component-containing electrical alternating signal having a decreasing signal amplitude.

4. The loading method according to one of claims 1 to 3, characterized in that an identification feature (27) of the machining tool (18) is read by a detection means (26) connected to the actuation device (7), and tool-characterizing data, in particular a tool shape, a tool weight and / or a tool length, are extracted from it by the actuation device (7).

5. The loading method according to claim 4, characterized in that, based on the extracted tool weight and / or the tool length, the first and / or the second signal strength is read by the actuation device (7) from a stored parameter table.

6. The loading method according to one of claims 1 to 5, characterized in that the pick-up and retention signal is emitted by the actuation device (7) as a PWM signal or PPM signal.

7. The loading method according to one of claims 1 to 6, characterized in that the tool-transfer device (1) has an electrical energy reservoir (8) connected to the actuation device and a charging contact (9) connected to the energy reservoir (8), wherein, after moving the tool-transfer device (1) along the guide track (4) into a parked position, the charging contact (9) of the tool-transfer device (1) is brought into connection with a charging terminal (30) of the waiting position.

8. The loading method according to one of claims 1 to 7, characterized in that the tool-transfer device (1) has a position sensor (29) connected to the actuation device, which position sensor (29) determines the position of the tool-transfer device (1) along the guide track (4) and communicates a reaching of the pick-up position (20) and / or a reaching of the deposition position (21) to the actuation device.

9. The loading method according to one of claims 1 to 8, characterized in that the demagnetization is performed prior to reaching of the deposition position (21), in particular immediately prior to the reaching of the deposition position (21).