Bending method and bending machine for performing the bending method

Abstract

A method of bending a metal product (2) is described, comprising at least the steps of: a) performing a relative movement between a bending head (3) having at least one bending group (5) and the metal product (2), and b) bending the metal product (2) by actuating the bending group (4). During step b) at least a first actuating device actuates the bending group (4) according to a respective movement trajectory (u(t)), and during step a) at least a second actuating device actuates the relative movement between the bending head (3) and the metal product (2) according to a respective movement trajectory (u). The method further comprises a preparation step during which the respective initial movement trajectory of the first actuating device and / or the respective initial movement trajectory of the second actuating device are modified for obtaining the respective movement trajectory (u(t)) according to a first parameter (a) and a second parameter (b).

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to Italian patent application No. 102020000032258, filed on December 23, 2020, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] This invention relates to a method for bending metal articles, particularly elongated metal articles, and even more particularly metal wires or tubes, to obtain articles with a defined bend. In particular, this invention relates to a method for bending metal articles that reduces vibrations in the metal articles that may occur during the method itself.

[0004] Advantageously, the present invention also relates to a bending machine for bending metal articles, particularly a wire bending machine or a tube bending machine. Background Technology

[0005] A bending machine is known for bending metal wires or bending metal tubes.

[0006] Such a machine is configured to perform a series of bending operations to obtain bent wires or bent tubes, respectively.

[0007] It is also known that these machines include at least one bending head and an actuating device, the bending head having one or more bending groups for bending, and the actuating device for relative movement between the bending head and the wire or tube.

[0008] The actuation device allows for relative positioning of the wire or tube with at least one bending group, enabling the bending group to bend accordingly.

[0009] It is known that the actuating device can be configured to move and / or rotate the bending head and / or the traveling wire or tube along the travel path.

[0010] A typical bending assembly includes a turntable and an actuator. The turntable has one or more engagement elements, each configured to contact a wire or tube. The actuator is coupled to the turntable and configured to rotate and translate the turntable about and along an axis used for bending the wire or tube.

[0011] During bending, the corresponding actuator executes a corresponding defined motion profile, such that at least one engaging element bends a portion of the wire or tube relative to another portion of the same wire or tube.

[0012] Typically, each filament or tube undergoes a series of bends to obtain the desired bend of the filament or the desired bend of the tube.

[0013] It is also known that, in order to obtain each bend, it is necessary to control the actuator according to a respective movement trajectory and it is also necessary to apply a sequence of respective movement trajectories in combination with a modification of the relative position between the bending head and the wire or tube.

[0014] It has been observed that oscillations of the wire or tube can be generated during the method, which sometimes cause unwanted deformations of the wire or tube and / or collisions of the wire or tube with parts of the bending machine.

[0015] In order to avoid these problems, the operator must manually modify the specific bending method, which consists of steps of bending and steps of modifying the relative position between the bending head and the wire or tube. On the one hand, this modification requires a lot of time, on the other hand, the modification and its success depend on the experience and expertise of the specific operator.

[0016] Furthermore, it should be considered that the application of this modification not only requires a high level of experience of the operator, but also a high basic qualification. In countries where there is a shortage of skilled workers, these aspects can be problematic. Furthermore, in the case of a high turnover of operators, defects can occur.

[0017] Furthermore, US-A-201 1 192204 proposes to reduce oscillations due to the generation of compensating movements.

[0018] In an alternative, DE-A-102014206622 describes the use of simulations, which require a lot of computing resources, for optimizing the bending of an article to be bent.

[0019] Therefore, there is a need in the industry to further improve the bending method and / or the bending machine, which would allow to solve at least one of the known defects.

[0020] In particular, there is a need in the industry for a bending method and / or for a bending machine, which allows to reduce the oscillations of the wire or tube in an automated manner. SUMMARY

[0021] The present invention achieves the above-mentioned objects, since it relates to a method of bending a metal article as defined in the independent claim. Alternative preferred embodiments are protected in the respective dependent claims.

[0022] The present invention also achieves the above-mentioned objects, since it relates to a machine according to claim 15. BRIEF DESCRIPTION OF DRAWINGS

[0023] Further features and advantages of the present invention will become apparent from the following detailed description, provided by way of non-limiting example, with reference to the drawings, in which:

[0024] - Figure 1 A bending machine is schematically and partially shown, wherein parts have been removed for clarity;

[0025] - Figure 2 An enlarged isometric view showing details of the bending machine in Figure 1 ;

[0026] - Figure 3 A model of a damped harmonic oscillator is schematically shown;

[0027] - Figure 4 A time course of oscillation of the wire is shown;

[0028] - Figure 5 An initial trajectory of motion and a modified trajectory of motion according to the present application are shown; and

[0029] - Figure 6 Some steps of the method according to the present application are schematically shown. DETAILED DESCRIPTION

[0030] In Figure 1 , 1 generally indicates a (automatic) bending machine for bending a metal product, in particular an elongated metal product (along an axis), more in particular a wire 2 or a metal tube.

[0031] According to some non-limiting embodiments, the metal product can have a cross-section of circular, oval, rectangular, square, elliptical or any other shape.

[0032] According to some non-limiting embodiments, the metal product can be hollow or solid.

[0033] According to some non-limiting embodiments, the metal product comprises at least one metallic material. According to some non-limiting variations, the metal product can also comprise at least one non-metallic material, such as a composite material or a plastic material.

[0034] In the following, reference is made to the bending of a wire 2 without any purpose of limitation.

[0035] However, the following description also applies to the bending of other metal products, such as metal tubes.

[0036] Moreover, in the following, the bending machine 1 for bending a wire 2 is described in detail without any purpose of limitation. However, the following description can also apply to a bending machine 1 for bending a metal product, such as a metal tube.

[0037] With particular reference to Figure 1 and Figure 2 , the bending machine 1 comprises at least:

[0038] - a control unit configured to control the operation of the bending machine 1 itself;

[0039] - a bending head 3, which is operatively connected, in particular, to the control unit and is configured to bend the wire 2, in particular at the bending station; and

[0040] - an actuation device, which is operatively connected, in particular, to the control unit and is configured to control and / or perform the relative motion between the bending head 3 and the wire 2.

[0041] In greater detail, the bending head 3 comprises one or more bending groups 4, in the specific case shown two bending groups 4, each configured to selectively bend the wire 2. In other words, each bending group 4 is configured to perform a bending step for bending the wire 2.

[0042] In greater detail, each bending group 4 can comprise at least:

[0043] - a respective turntable 5, which is insertable, in particular movably, into a respective housing seat of the bending head 3;

[0044] - one or more engagement elements 6, which are integral with the respective turntable 5; and

[0045] - first actuation means (known per se but not shown), which are operatively connected, in particular, to the control unit and are coupled to the respective turntable 5, and are configured to actuate the angular motion and / or the translation of the turntable 5 about or along the respective axis, respectively.

[0046] Furthermore, the control unit is configured to control each first actuation means so as to determine the bending operation by means of the angular motion and / or the translation of the turntable 5 and, consequently, the relative displacement of the engagement elements 6.

[0047] In this specific case, each first actuation means comprises at least one (electric) motor to determine and / or actuate the angular motion of the respective turntable 5 and / or a linear actuator, for example a pneumatic actuator, to determine the translation of the respective turntable 5.

[0048] In greater detail, the actuation device can be configured to advance the wire 2, in particular along an advancement path towards the bending station, and / or to move and / or rotate the bending head 3, in particular about at least three axes.

[0049] In greater detail, the actuation device can be provided with a plurality of second actuation means, each configured to determine the advancement of the wire 2 along the advancement path and / or the movement and / or rotation of the bending head 3.

[0050] Preferably, the first plurality of second actuation means is configured to determine at least partially the movement and / or rotation of the bending head 3.

[0051] Even more preferably, the second plurality of second actuation devices can be configured to at least partially determine the travel of the wire 2.

[0052] According to the non-limiting embodiment shown, the actuation device includes a first set of traveling wheels 7 and a second set of traveling wheels 8 arranged one after another. In particular, each traveling wheel 7 faces a corresponding traveling wheel 8, such that the traveling wheels 7 and 8 act on opposite sides of the wire 2.

[0053] Specifically, the first and second groups are arranged upstream of the bend head 3 along the travel path.

[0054] More specifically, the travel wheels 7 and 8 are coupled to one or more second actuating devices and are configured to cooperate therebetween along at least a portion of the travel wire 2 of the travel path.

[0055] Furthermore, the bending machine 1, particularly the bending head 3, may include a cutting unit configured as a cutting wire 2.

[0056] Special Reference Figure 1 The bending machine 1 may also include a storage device 9 containing (unbent) wire 2. In particular, the actuating device is configured to move the wire 2 from the storage device 9 toward the bending head 3 and / or the bending station.

[0057] More specifically, the storage device 9 is configured to contain filament 2 in the form of a roll.

[0058] More specifically, the storage device 9 includes a support 10 for carrying the filament 2 in the form of a roll, and in particular, the support 10 is designed to allow the filament 2, which is arranged in a roll, to unroll.

[0059] Special Reference Figure 1 The bending machine 1 may also include a human-machine interface 11, which is configured to enable the operator to send instructions to the bending machine 1, in particular to the control unit, and / or to receive information from the bending machine 1.

[0060] In use, bending machine 1 bends wire 2 to obtain (defined) bent wire 2'.

[0061] The bending method includes at least the following steps:

[0062] a) Perform the relative movement between the bending head 3 and the wire 2; and

[0063] b) Bending wire 2.

[0064] Furthermore, the method may also include one or more repeating steps, during which steps a) and b) are repeated. In particular, the execution of the repeating steps results in a sequence of steps a) and b) to obtain the desired curved filament 2'.

[0065] Preferably, the method further includes at least one cutting step in which wire 2 is cut. In particular, the cutting step may be performed before or after steps a) and b).

[0066] More specifically, during the execution of step a), at least one of the bending groups 4 is positioned relative to the wire 2 such that at least one of the engaging elements 6 is positioned adjacent to and / or in contact with the wire 2. Subsequently, during step b) and as explained in detail below, the corresponding engaging element 6 is moved to obtain the corresponding bend in the wire 2.

[0067] More specifically, during each step b), the first (free) portion 15 of the wire 2 is bent relative to the second portion 16 of the wire 2 by actuating the corresponding bending assembly 4, particularly the corresponding turntable 5 (see...). Figure 2 For example, during the execution of the corresponding step b), the second part 16 remains stationary. In particular, during each step b), an angle defined between the first part 15 and the second part 16 is obtained. More specifically, the defined angle can vary between one step b) and the next step (and is determined by the shape of the desired curved wire 2').

[0068] More specifically, during step a), at least one second actuation device actuates the relative movement between the bending head 3 and the wire 2 according to the corresponding motion trajectory.

[0069] According to some non-limiting embodiments, during step a), a plurality of second actuation devices may also be actuated to actuate the relative movement between the bending head 3 and the wire 2, each second actuation device being actuated according to a corresponding motion trajectory.

[0070] For example, one or more second actuating devices, particularly a first plurality of second actuating devices, can move and / or rotate the bending head 3.

[0071] Optionally and / or additionally, one or more second actuating devices, particularly a second plurality of second actuating devices, may travel the wire 2.

[0072] Furthermore, during step b), at least one of the first actuating devices (in particular the corresponding motor) actuates the corresponding bending group 4, in particular the corresponding turntable 5, according to the corresponding motion trajectory, for performing the corresponding bending of the wire 2.

[0073] More specifically, each motion trajectory (of the first or second actuation device) describes the time progression of the control parameters of the corresponding first or second actuation device as a function of time. In particular, each motion trajectory defines at least an acceleration step and a deceleration step.

[0074] For example, such asFigure 5 As shown, the motion trajectory (see dashed line) of the corresponding motor of the corresponding first actuation device can describe the angular position of the motor as a function of time. Therefore, in this case, the motion trajectory describes the angular position of the corresponding turntable 5 and / or the corresponding engagement element 6 as a function of time.

[0075] It should be noted that during step b), the corresponding motion trajectory actuated by the corresponding first actuation device may be different from other motion trajectories, especially in order to obtain the corresponding desired angle between the first part 15 and the second part 16.

[0076] Preferably, during steps a) and b), the control unit controls the corresponding motion trajectories of the first and second actuators.

[0077] like Figure 2 As shown, during this method, especially after step a) and / or step b), oscillations of the filament 2, particularly the oscillations of the first part 15, can be generated.

[0078] As described below, in order to reduce the oscillation of wire 2 (especially the first part 15), at least some motion trajectories are determined in preparation step c), particularly those motion trajectories describing the actuation of the first actuating device (especially the corresponding motor (and the corresponding turntable 5)) (see...). Figure 6 ).

[0079] More specifically, during step c), at least one corresponding initial motion trajectory (of the first actuation device and / or the second actuation device) is modified, for example, see Figure 5 The solid line in the diagram is used to obtain the corresponding motion trajectory based on the first parameter a and the second parameter b. Figure 5 (dashed line in the middle), where: the first parameter a depends on the oscillation frequency ω of the damped harmonic oscillator, which models and / or describes the oscillation of the wire 2 caused by the application of the corresponding motion trajectory of the corresponding first actuation device or the corresponding second actuation device; and the second parameter b depends on the damping ξ of the oscillation of the damped harmonic oscillator.

[0080] Special Reference Figure 3 The damped harmonic oscillator enables the determination and / or description of the oscillation y(t) of the filament 2 caused by the corresponding motion trajectory u(t), particularly the application of the first part 15, after performing the relevant step a) or step b).

[0081] More specifically, a harmonic oscillator is described by a corresponding mass M, a spring with a spring constant K, and a damper with a damping constant D.

[0082] For example, in step b), the applied model stipulates that once the corresponding bending group 4, especially the corresponding turntable 5, and even more specifically, the corresponding bending element 6 loses contact with the wire 2, the oscillation y(t) of the wire 2 (especially the first part 15) is equivalent to the free motion of the mass M in the mass-spring-damper system, which is generated by moving the mass M away from its equilibrium position.

[0083] More specifically, the transfer function G(s) = Y(s) / U(s) in the Laplace domain links the oscillation y(t) with the trajectory u(t) (where Y(s) corresponds to the oscillation y(t) in the Laplace domain, and U(s) corresponds to the trajectory u(t) in the Laplace domain), where:

[0084] G(s)=Y(s) / U(s)=((2*ξ*s / ω)+1) / ((s 2 / ω 2 )+(2*ζ*s / ω)+1), where s is a Laplace variable (i.e. a complex variable).

[0085] Furthermore, the oscillation frequency ω is proportional to √(K / M), and the damping ξ is proportional to D / (2*√(M*K)).

[0086] However, the values ​​of mass M, spring constant K, and damping constant D are difficult to determine from the geometry and mechanical properties of wire 2, especially from the geometry and mechanical properties of the first part 15, and from the properties of the material connected to wire 2.

[0087] Preferably, the first parameter a is proportional to, and in particular equal to, the reciprocal of the square of the oscillation frequency ω; and the second parameter b is proportional to the damping ξ, and also proportional to the reciprocal of the oscillation frequency ω.

[0088] Therefore: a = 1 / ω 2 b=(2*ξ) / ω.

[0089] Based on the definitions of the first parameter a and the second parameter b, the transfer function G(s) in the Laplace domain of the damped harmonic oscillator that links the motion trajectory u(t) with the oscillation y(t) can be obtained as: G(s) = (b*s+1) / (a*s) 2 +b*s+1).

[0090] It should be noted that the first parameter a and the second parameter b can vary during each step a) and / or each step b). In other words, the mass M, the spring constant K, and the damping coefficient D are not constant, but can vary between each step a) and / or each step b).

[0091] Preferably, during step c), the first parameter a and the second parameter b are read from memory 17 (see...). Figure 6 In particular, memory 17 is part of bending machine 1, and even more specifically, memory 17 is part of control unit. Specifically, memory 17 contains multiple sets of corresponding first parameters a and multiple sets of corresponding second parameters b, each set being attributable to one or more corresponding steps a) and / or b).

[0092] Furthermore, the method may include an initialization step d), during which one or more initial motion trajectories are determined (see initialization step d). Figure 5 (The solid lines in the diagram), in particular each initial motion trajectory is connected to the corresponding first actuation device and / or the corresponding second actuation device, as a function of the desired bending of the wire 2'.

[0093] More specifically, during step d), steps a) and b) and their order are also determined.

[0094] More specifically, the initial motion trajectory and / or the order of steps a) and b) are determined, for example, by the control unit as a function of the desired bending of the wire 2'. For example, according to some non-limiting embodiments, the initial motion trajectory and / or the order of steps a) and b) can be determined, for example, by the control unit as a function of the desired bending of the wire 2' and by a software system and / or by a human-machine interface 11. For example, the software system may be based on computer-aided design software (CAD) and / or computer-aided manufacturing software (CAM) and / or a distributed computer system for monitoring and supervision (also known as SCADA).

[0095] According to some non-limiting variations, during step d), the operator may, for example, control and / or modify the initial motion trajectory and / or the order of steps a) and b) via human-machine interface 11.

[0096] It should be noted that even if the initial motion trajectory results in the determined bending of the wire 2', the initial motion trajectory is not optimized, taking into account the possible oscillations y(t) of the wire 2 (especially the first part 15), which can occur during the method.

[0097] For example, in Figure 4 In the diagram, the stress-induced oscillation of wire 2, based on the initial motion trajectory of the corresponding first actuation device (particularly the corresponding motor), is shown as a solid line, while the stress-induced oscillation based on the motion trajectory obtained by modifying the initial motion trajectory is shown as a dashed line. It can be seen that the application of the motion trajectory significantly reduces the oscillation y(t).

[0098] Therefore, by modifying the initial motion trajectory according to the corresponding first parameter a and the corresponding second parameter b, the oscillations linked to the corresponding step a) or the corresponding step b) can be reduced.

[0099] According to some non-limiting embodiments, it is not necessary to modify all the initial motion trajectories, but only some of them. In particular, it has been observed that the critical value linked to the stress-induced oscillation from the second actuator is less than the critical value linked to the stress-induced oscillation from the first actuator.

[0100] More specifically, according to some non-limiting embodiments, only some or all of the initial motion trajectory associated with the first actuation device according to the corresponding first parameter a and the corresponding parameter b are modified, and in particular, the motion trajectory associated with the second actuation device is not modified.

[0101] Preferably, especially for reference Figure 6 During step c), each motion trajectory is calculated by the calculation group 18 of the bending machine 1 (particularly the control unit) according to the corresponding first parameter a and the corresponding second parameter b. In particular, the calculation group 18 can be arranged locally and / or remotely.

[0102] More specifically, according to a possible embodiment, during step c), each initial motion trajectory (to be modified) is filtered, particularly by computation group 18, wherein the transfer function F(s) expressed in the Laplace domain is compared with (a*s) 2 The motion trajectory u(t) is determined by a ratio of +b*s+1). Specifically, F(s) is the transfer function, whose modulus and step diagram over the frequency range of interest are equal to (a*s) / (t). 2 The modulus and steps of +b*s+1).

[0103] Optionally and / or additionally, during step c), an optimization sub-step is performed, particularly by computation group 18, during which the determination is made when considering the Laplace domain G(s) = ((b*s+1) / (a*s) 2 The transfer function G(s) in +b*s+1)) generates the minimum oscillating trajectory u(t).

[0104] Specifically, during the optimization sub-step, the motion trajectory applied is started, and then (by a numerical algorithm executed by computation group 18) the motion trajectory u(t) that results in the minimum oscillation is determined.

[0105] More specifically, during the optimization sub-step, computation group 18 determines the oscillations provided by the damped harmonic oscillator model based on the applied motion trajectory (and as described by the transfer function G(s)), and assigns a cost to the provided oscillations based on the applied motion trajectory. Then, computation group 18 determines the oscillations provided by the damped harmonic oscillator model based on a modified applied motion trajectory, which again determines the oscillations and the corresponding costs. Computation group 18 continues these operations until the motion trajectory u(t) that produces the minimum oscillation is determined.

[0106] Preferably, during the optimization sub-step, at the beginning of each optimization sub-step itself, the transfer function F'(s) expressed in the Laplace domain and (a*s) are taken into account. 2 +b*s+1) is proportional to the motion trajectory obtained by filtering the initial motion trajectory. Specifically, F'(s) is the transfer function whose modulus and step diagram within the frequency range of interest are equal to (a*s) 2 The modulus and steps of +b*s+1).

[0107] According to some non-limiting embodiments, in order to determine each first parameter a and each second parameter b, a corresponding calibration step e is performed.

[0108] More specifically, during step e), at least the following sub-steps are performed:

[0109] -Actuation initial motion trajectory;

[0110] - Monitor the oscillation of wire 2 after the corresponding actuator step, especially the oscillation of the first part 15; and

[0111] - Determine the corresponding first parameter a and the corresponding second parameter b of the damped harmonic oscillator, which describe the oscillation monitored during the corresponding monitoring sub-step.

[0112] In particular, during each determined sub-step, a corresponding first parameter a and a corresponding second parameter b are determined, which minimizes the difference between the corresponding monitored and modeled and / or estimated oscillations.

[0113] More specifically, during a defined sub-step, the damped harmonic oscillator is described and / or modeled and / or estimated according to the transfer function G'(s) in the Laplace domain: G'(s) = (b'*s+1) / (a'*s) 2 +b'*s+1), where a' corresponds to the first parameter to be determined and b' corresponds to the second parameter to be determined.

[0114] Specifically, during the defined sub-steps, determining the first parameter a' and the second parameter b' of the estimated oscillation that have the minimum difference with the corresponding monitored oscillation defines the corresponding first parameter a and the corresponding second parameter b.

[0115] More specifically, during the defined sub-steps, particularly in the sub-steps executed by the calculation group 18 of the bending machine 1, additional steps are performed:

[0116] i) Assume the corresponding value of the first parameter a' and the corresponding value of the second parameter b';

[0117] ii) Calculate the oscillation y'(t) estimated based on the transfer function G'(s) and the corresponding values ​​in the first value a' and the second value b';

[0118] iii) Compare the estimated oscillation y'(t) with the monitored oscillation to determine the error;

[0119] iv) Based on the error obtained during step iii), modify the first parameter a' and the second parameter b'; and

[0120] v) Repeat steps ii) to iv).

[0121] Specifically, if the error determined in step iii) is equal to or greater than the determined threshold, then steps iv) and v) are performed.

[0122] According to some non-limiting embodiments, the bending machine 1 includes a camera for monitoring the oscillations of the wire 2, particularly the first portion 15.

[0123] Preferably, during the monitoring step, the oscillation is monitored by a camera.

[0124] The advantages obtained by examining the characteristics of the bending machine 1 and the method according to the invention are obvious.

[0125] In particular, this method automatically and significantly reduces the oscillation of the wire 2, especially the first part 15. Therefore, it reduces the risk of undesirable deformation of the wire 2 due to oscillation and / or contact between the wire 2 and the bending machine 1.

[0126] Another advantage is that no operator intervention is required to reduce oscillations.

[0127] Finally, it is clear that modifications and variations can be made to the bending machine 1 and the bending method described and shown herein without departing from the scope of protection defined by the claims.

[0128] According to some embodiments not shown, the bending machine 1 includes at least two bending heads 3.

[0129] Alternatively or alternatively, the actuation device is configured to place the wire 2 in the working position, and during steps a) and b), the wire 2 itself does not move, but only the bending head 3 moves.

[0130] Alternatively or additionally, the storage device 9 may be configured to accommodate metal articles from the segments, particularly metal wires or tubes from the segments. According to these embodiments (not shown), the actuation device may include a displacement unit for automatically loading and / or unloading metal articles from the segments. Alternatively or additionally, manual loading and / or unloading of metal articles from the segments is possible.

Claims

1. A method for bending a metal article (2) along a longitudinal axis to obtain a defined bent article, comprising at least the following steps: a) Performing relative movement between the bending head (3) having at least one bending group (4) and the metal article (2); and b) Bending the metal article (2) by actuation of the bending assembly (4); in, During step b), at least the first actuating device actuates the bending group (4) according to the corresponding motion trajectory u(t) to perform the corresponding bending of the metal article (2); During step a), at least the second actuation device actuates the relative motion between the bending head (3) and the metal product (2) according to the corresponding motion trajectory u(t); The method is characterized in that it further includes a preparation step c), during which the corresponding initial motion trajectory of the first actuating device and / or the corresponding initial motion trajectory of the second actuating device are modified to obtain the corresponding motion trajectory u(t). During step c), the initial motion trajectory is modified according to the first parameter a and the second parameter b. Wherein, the first parameter a depends on the oscillation frequency ω of the damped harmonic oscillator, which models and / or describes the oscillation of the metal article (2) caused by the application of the corresponding motion trajectory u(t) of the corresponding first actuation device or the corresponding second actuation device, and the second parameter b depends on the damping ξ of the oscillation of the damped harmonic oscillator.

2. The method according to claim 1, wherein, The metal product (2) is a long and thin metal product.

3. The method according to claim 1, wherein, The metal product (2) is a metal wire or a metal tube.

4. The method of claim 1, comprising one or more repeated steps, wherein steps a) and b) are repeated during the repeated steps. in, During step c), multiple corresponding initial motion trajectories of the first actuation device and / or the second actuation device are modified according to the corresponding first parameter a and the corresponding second parameter b to obtain the corresponding motion trajectory u(t).

5. The method according to claim 1 or 4, wherein, During step c), the first parameter a and the second parameter b are read from the memory (17).

6. The method of claim 1, further comprising an initialization step, during which one or more initial motion trajectories are determined based on the desired bent metal article.

7. The method of claim 1, further comprising a calibration step, during which the first parameter a and the second parameter b are determined; in, During the calibration step, the following sub-steps are performed: - Actuate the initial motion trajectory; - Monitor the oscillation y(t) of the metal article (2) after the actuation sub-step; and - Determine the first parameter a and the second parameter b of the damped harmonic oscillator, which are capable of describing the monitored oscillations during the corresponding monitoring sub-steps.

8. The method according to claim 7, wherein, During the determination sub-step, the monitored oscillation is modeled and / or estimated based on a damped harmonic oscillator, which is transmitted through the Laplace domain G'(s) = (b' s+1) / (a' s 2 +b' The transfer function G'(s) in (s+1) is used to represent this, where s is a Laplace variable; Here, a' corresponds to the first parameter to be determined, and b' corresponds to the second parameter to be determined.

9. The method according to claim 8, wherein, During the determination of sub-steps, the following further steps are performed: i) Assume the value of the first parameter a' to be determined and the value of the second parameter b' to be determined; ii) Calculate the estimated oscillation y'(t) based on the transfer function G'(s) and the values ​​of the first parameter a' and the second parameter b' to be determined; iii) The estimated oscillation y'(t) is compared with the monitored oscillation to determine the error; iv) Modify the first parameter a' and the second parameter b' to be determined based on the error obtained during step iii); and v) Repeat steps i) to iv).

10. The method according to claim 7, wherein, During the monitoring sub-step, the oscillation is monitored via a camera.

11. The method according to claim 1, wherein, The first parameter a is proportional to the reciprocal of the square of the oscillation frequency ω, and the second parameter is proportional to the damping ξ, and also to the reciprocal of the oscillation frequency ω.

12. The method according to claim 11, wherein, The first parameter a is equal to the reciprocal of the square of the oscillation frequency ω.

13. The method according to claim 1, wherein, The damped harmonic oscillator is described by mass M, spring constant K, and damping factor D; Wherein, the oscillation frequency ω and Proportional; and wherein the damping ξ is proportional to; Proportional.

14. The method according to claim 1, wherein, The Laplace transfer function of the damped harmonic oscillator, which links the motion trajectory to the oscillation, is: G(s) = (b s+1) / (a s 2 +b (s+1), where s is a Laplace variable; and a corresponds to the first parameter, and b corresponds to the second parameter.

15. The method according to claim 1, wherein, During step c), the initial trajectory is filtered using a transfer function F(s) expressed in the Laplace domain, the transfer function F(s) being related to (a) s 2 +b The parameters are proportional to s+1) to determine the trajectory u(t), where s is a Laplace variable, and a corresponds to the first parameter and b corresponds to the second parameter.

16. The method according to claim 1, wherein, During step c), an optimization sub-step is performed, during which the relationship between the Laplace domain and (b) is determined. s+1) / (a s 2 +b The trajectory u(t) generates minimum oscillations when the transfer function is proportional to s+1), where s is a Laplace variable; And 'a' corresponds to the first parameter, and 'b' corresponds to the second parameter.

17. The method according to claim 16, wherein, During the optimization sub-step, at the beginning of the optimization sub-step itself, taking into account the transfer function F'(s) and (a) expressed in the Laplace domain... s 2 +b The motion trajectory obtained by filtering the initial motion trajectory is proportional to s+1), where s is a Laplace variable, and a corresponds to the first parameter and b corresponds to the second parameter.

18. A bending machine (1) for bending metal articles (2), comprising: - Control unit, which is configured to control the operation of the bending machine (1) itself; - A bending head (3), the bending head (3) having at least one bending assembly (4), the bending assembly (4) being configured to bend the metal article (2); and - An actuating device configured to control and / or perform relative movement between the bending head (3) and the metal article (2); The bending group (4) includes at least a first actuation device configured to actuate the bending group (4) according to a corresponding motion trajectory u(t) to perform a corresponding bending of the metal product (2); The actuation device includes at least a second actuation device configured to actuate the relative motion between the bending head (3) and the metal product (2) according to a corresponding motion trajectory u(t); The bending machine (1) is characterized in that it is configured to perform a preparation step, during which the corresponding initial motion trajectory of the first actuating device and / or the corresponding initial motion trajectory of the second actuating device are modified to obtain the corresponding motion trajectory u(t). The bending machine (1) is configured to modify the initial motion trajectory according to the first parameter a and the second parameter b; Wherein, the first parameter a depends on the oscillation frequency ω of the damped harmonic oscillator, which models and / or describes the oscillation of the metal article (2) caused by the application of the corresponding motion trajectory u(t) of the corresponding first actuation device or the corresponding second actuation device, and the second parameter b depends on the damping ξ of the oscillation of the damped harmonic oscillator.

19. The bending machine (1) according to claim 18, wherein, The metal product (2) is a long and thin metal product.

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