EP1136146B1 - Method for bending sheets and machine for carrying out this method - Google Patents

Abstract

The method forms angled sections with sides (15,16) at a relative bending angle ( beta ) to each other, using forming die (8) and forming plate (10). During initial component processing, a reference position for a control feeler (18) is defined, with a component angle corresponding to the size of the bending angle. During further processing, and during working movement of die and plate, the feeler is placed on at least one of the component legs of the angle thus formed, and moved with the associated leg. The working movement of die and plate is stopped, when position detection determines that the control feeler is in its defined reference position.

Description

The invention relates to a method for creating workpiece angles, especially of sheet metal angles, with two under one Bending angle of mutually extending workpiece legs, wherein a forming die and a forming die assigned to it with a work movement with a bevel of the work to be machined Workpiece are moved relative to each other and at an initial Workpiece machining a workpiece angle with the Target size of the bending angle is created. The invention relates further a machine for performing the described Procedure, with a forming stamp and one this associated forming die, the forming die and the forming die by means of a controllable drive with a Working movement while folding the workpiece to be machined are movable relative to each other.

As is known, occurs when bending workpieces with elastic Properties, such as when folding sheet metal, in addition to the desired plastic also an undesirable elastic Workpiece deformation. Resulting from the elastic deformation after the relief of the workpiece in question from the Forming tool a springing open during the previous Bending process created workpiece angle and associated with it an increase in the from the legs of the workpiece angle on End of working movement of forming stamp and forming die included bending angle. Bending workpieces with This results in a bending angle of a predetermined target size difficult.

A consideration of the phenomenon described above generic method and a corresponding generic Machine are known from EP-B-0 637 371. In the case of The state of the art is first by way of a test bend the penetration depth of a forming die on an associated one Forming die measured, where the result of the Bending process results in a workpiece angle, the bending angle has the target size. The penetration depth of the forming die determined in this way is stored in a machine control. at subsequent workpiece machining then becomes the current one Size of the penetration depth of the forming die on the forming die continuously measured and the working movement of forming stamp and the forming die ends as soon as the previous one in penetration depth stored in the machine control is measured. Accordingly, the previously known machine requires, among other things. a device for measuring the current penetration depth of the forming die on the forming die and a device for comparison the measured instantaneous with that in the machine control stored penetration depth.

A bending method and a bending device are known from US-A-4,489,586 known, in the case of which the postponement of a Push button opposite a punch or the displacement two buttons opposite a punch or the displacement two buttons measured relative to each other and thus obtained Measured values with a bending angle setpoint or one of these representative setpoint are compared.

NL-A-8 105 266 discloses for a bending method and a bending device, that amount of displacement of a sensor to be calculated against an associated bending punch, at the Are the bending angles on the machined workpiece assumes its setpoint. The amount of the relative shift determined in this way of feeler and bending stamp is used in the following Workpiece processing used in two ways. On the one hand are the relative displacements that result during workpiece machining of the sensor with respect to the bending punch continuously measured and with the previously determined reference value compared. If the measured value and the reference value match the machine is switched off. Alternatively, the sensor is in accordance with NL-A-8 105 266 before starting to work with the previously calculated as a reference value compared to the Bending stamp fixed on this. Comes with the following Workpiece machining the workpiece concerned with the preset If the sensor is in contact, the machine is stopped.

The invention lies on the basis of the described prior art based on the task, a method and a machine to create workpiece angles to create it allows workpieces to be cut easily and with high precision To shape workpiece angles, the bending angle of which is the target size has.

The procedural object is achieved by the invention Claim 1, the device-related task by the Invention according to claim 5 solved.

Accordingly, the method according to the invention is directly position-controlled from. A workpiece angle with the nominal size of the There is a bending angle and the working movement of the forming stamp and the forming die is terminated as soon as by pure position detection it is determined that the control button is its as takes such a predetermined reference position. Except for one made during the initial workpiece machining Angle measurement to check the during this workpiece processing created workpiece angle on the presence of a bending angle with the target size, is required in the case of the invention high-precision reproduction of the bending angle with the target size basically none complicating the procedure and accuracy bending angle reproduction may be negative influencing measurement.

Accordingly, the machine according to the invention allows simple Averaging a very accurate bend angle reproduction.

Preferred variants of the method according to the invention are in dependent claims 2 to 4, preferred types the machine according to the invention in the dependent claims 6 to 14.

Allow the measures specified in claims 2 and 6 a definition of the reference position of the control button in a particularly simple way. The characteristic features of dependent claims 3, 7 and 8 are also in the interest of a simple process of the invention Method or a simple structure of the invention Machine provided. The characteristic features of the claims 4, 9 and 14 serve as far as possible procedural or device automation.

Claims 11 and 12 describe types of the invention Machine, in the case of which a highly accurate reproduction of the workpiece bending angle with target size using proven functionally reliable components can be realized.

Due to the characterizing features of claims 10 and 13 finally the machine in question is enabled Workpiece angles optionally with different bending angles Create target size and / or changes regarding The spring-back properties of the machined workpieces must be taken into account.

Fig. 1

eine Gesamtansicht einer Maschine zum Erstellen von Werkstückwinkeln in Form einer Gesenkbiegepresse mit einem Umformstempel, einer Umformmatrize sowie einer ersten Vorrichtung zur Reproduktion von Biegewinkeln mit Sollgröße,

Fign. 2 und 3

schematisierte Schnittdarstellungen zu der Biegewinkel-Reproduktionsvorrichtung gemäß Fig. 1 mit der Schnittebene II/III in Fig. 1,

Fign. 4 und 5

Schnittdarstellungen entsprechend den Fign. 2 und 3 zu einer zweiten Vorrichtung zur Reproduktion von Biegewinkeln mit Sollgröße und

Fig. 6

den umformstempelseitigen Teil der Biegewinkel-Reproduktionsvorrichtung gemäß den Fign. 4 und 5 in der Ansicht in Richtung des Pfeils VI in Fig. 5.

The invention is explained in more detail below on the basis of schematic representations of exemplary embodiments. Show it:

Fig. 1

1 shows an overall view of a machine for creating workpiece angles in the form of a die bending press with a forming die, a forming die and a first device for the reproduction of bending angles with a desired size,

FIGS. 2 and 3

1 with the sectional plane II / III in FIG. 1,

FIGS. 4 and 5

Sectional representations according to FIGS. 2 and 3 to a second device for the reproduction of bending angles with nominal size and

Fig. 6

the part of the bending angle reproducing device on the forming die side according to FIGS. 4 and 5 in the view in the direction of arrow VI in FIG. 5.

1, a press brake 1 comprises a machine frame with two stands 2, 3. Between stands 2, 3 is a top beam 4 in a illustrated by a double arrow 5 Direction can be raised and lowered. The upper cheek 4 passes at its lower end into a press beam 6, the extends across the entire machine front. For lifting and Lowering the upper cheek 4 serve hydraulic press cylinders 7, which attack on the press beam 6. In an undercut Longitudinal groove of the press beam 6 is an upper tool in the form of a ledge-like forming stamp 8 held in downwards a forming edge 9 ends. The forming die 8 acts with a formed as a forming die 10 lower tool together. The Forming die 10 is on a table 11 of the die bending press 1 mounted and points on the forming die 8 facing Side on a V-shaped groove 12.

A machine control 23 is accommodated in a control panel 13, among others the press cylinder 7 and thus the drive for the relative movement of the forming die 8 and the forming die 10 controls.

The press brake 1 is used to fold a workpiece 14, in the present case a sheet of metal. In the initial state it is Workpiece 14 in Fig. 1 with solid lines, in the folded Condition, i.e. as workpiece angle, shown in dashed lines. On the workpiece 14 bent to a workpiece angle two workpiece legs 15, 16 at a bending angle β to each other. A hint on the stamping side can be seen in FIG. 1 Part 17 of a device for the reproduction of Bending angles with target size.

According to FIGS. 2 and 3 comprises the one integrated in the forming die 8 Part 17 of the device for the reproduction of bending angles β with setpoint a control button 18 and a reference button 19. The control button 18 and the reference button 19 are guided on the forming die 8 in the direction of the double arrow 5 and movable in this direction relative to each other. The Reference button 19 is part of a device 20 for definition a reference position of the control button 18 and in this function connected to a switching element 21 one Switching device 22. The switching element 21 is opposite the reference button 19 in the direction of the double arrow 5, i.e. in Direction of the relative mobility of control button 18 and reference button 19, adjustable. Both the control button 18 and the reference button 19 is based on two points on the Workpiece 14, the support of the reference button 19th between the contact points of the control button 18. The Set the support of the control button 18 and the reference button 19 lie symmetrically on both sides of that plane, by the forming edge 9 of the forming die 8 and the in the figures 2 and 3 dash-dotted axis of the relative movement spanned by control button 18 and reference button 19 becomes. The arrangement described would be functional in principle, even if the control button 18 and / or the Reference button 19 only at one point on the Place workpiece 14 on top. The switching device 22 is with the Machine control 23, in detail with the drive control for the relative movement of the forming die 8 and the forming die 10 in connection.

For creating workpiece angles with constant accuracy The specified target size of the bending angle β is initially at an initial workpiece machining a reference position defined for the control button 18. For this purpose, a Workpiece 14 in a conventional manner by relative movement of Forming punch 8 and forming die 10 with a bending angle β the nominal size.

The conditions at the beginning of the initial workpiece machining are illustrated in Fig. 2. The stamp 8 is Accumulated on the top of the still undeformed workpiece 14. The control button 18 and the reference button 19 are located on both sides of the forming die 8 at a distance from its forming edge 9 on the top of the workpiece 14.

Based on the relationships according to FIG. 2, the forming stamp 8 and the forming die 10 with their working movement moved relative to each other while folding the workpiece 14. As usual, the workpiece 14 initially becomes slight over arch. At the end of the working movement of forming stamps 8 and Forming die 10 has the folded, still from stamping 8 and forming die 10 loaded workpiece 14 accordingly a bending angle β, the size of which is smaller than the target size. The extent of the overbend is chosen so that the size of the bending angle β on the folded workpiece 14 after its relief from the forming die 8 and the forming die 10 and the associated elastic return movement the workpiece leg 15, 16 corresponds to the target size.

3 shows the forming die 8 and the forming die 10, like this the folded workpiece 14 at the end of that working movement act on the basis of which there is a workpiece angle with the target size of the bending angle β results. The control button 18 and the reference button 19 are still on both sides of the forming die 8 on the workpiece 14 or on the Workpiece legs 15, 16 on. Under the effect of the stamp 8 and the forming die 10 are the control buttons 18 and the reference button 19 via the workpiece legs 15, 16 from it 2 according to FIG. 2 on the forming die 8 upwards and thereby also been shifted relative to each other. At the end of the labor movement of forming die 8 and forming die 10 takes the control button 18 a completely compared to the reference button 19 certain position, namely the position according to FIG. 3. at this position of the control button 18 relative to the reference button 19 results on the workpiece 14 after its relief a bending angle from the forming die 8 and the forming die 10 β with the target size. This from the control button 18 opposite the position taken by the reference button 19 is as Reference position of the control button 18 defined. The definition takes place by means of the switching element 21 of the switching device 22, which is in the direction of the relative movement of control buttons 18 and Reference button 19 is moved to a position in which it is touched by the control button 18. This will make the reference position of the control button 18 is a switching state of the Touching the switching element 21 switchable switching device 22 assigned to a termination via the machine control 23 the working movement of the forming die 8 and the forming die 10 causes. The control button 18 with the switching element touching it 21 is also shown in FIG. 3.

For workpiece machining that follows the initial workpiece machining the working movement of forming stamp 8 and forming die 10 each ended as soon as the control button 18 its defined in the initial workpiece machining Takes reference position. The switching element 21 serves as Position detector for detecting the reference position of the control button 18. The created workpiece angles have a bending angle β exactly with the target size, provided that the processed Workpieces 14 have a substantially identical springback behavior after the relief of the forming die 8 and forming die 10 show. Such a uniformity of the Springback behavior can be assumed, for example in the case of workpieces from the same batch, in the case of Workpieces, for example, in their thickness or - in Case of sheets - largely match in their rolling direction.

Are workpieces with workpieces that are initially folded edit changed springback properties or should the workpiece angle be changed with a bending angle β Setpoint size is created for the control button 18 to define a new reference position. this happens also as part of an initial workpiece machining, in which the switching element 21 of the switching device 22 compared to its previously occupied position in Direction of the relative movement of control button 18 and reference button 19 is to be adjusted.

A second type of device for the reproduction of bending angles with nominal size for use on a press brake 1 according to FIG. 1 is the FIGS. 4 to 6.

In a forming die cooperating with a forming die 110 108, a control button 118 is integrated both as a reference button and as such as part of one Device 120 is used to define a reference position. On a guide pin 124 connected to the forming die 108 is the control and reference button 118 in the direction of a double arrow 105 slidably guided relative to the forming die 108. In addition, the control and reference button 118 is on the side deflectable in the direction of a double arrow 125.

At its end remote from the forming die 110 is the Control and reference button 118 provided with an LED bracket 126. The LED bracket 126 carries a light source 127 that from Light units in the form of LEDs 127/1, 127/2, 127/3, 127/4, 127/5 is composed. The latter follow in the direction of the double arrow 105 on top of each other and can be switched on and off separately.

The light source 127 is assigned a PSD (position sensitive Detector) 128 trained optical sensor, which in turn is attached to a PSD bracket 129. The PSD bracket 129 again by means of a clamping plate 130 and a clamping screw 131 held clamped on the forming die 108. Accordingly The double arrow 105 also illustrates the direction the relative mobility of light source 127 and PSD 128. The latter is connected to the machine control via a control line 23 of the press brake 1 and there with the drive control for the relative movement of the forming die 108 and the forming die 110 connected.

Also in the case of the device according to FIGS. 4 to 6 is first a reference position of the control button, in this case of the control and reference button 118. To this Purpose is based on an initial workpiece machining 4 from the initially flat Workpiece 14 is a workpiece angle with a bending angle β Shaped size. During the work movement in question the forming die 108 and the forming die 110 are supported Control and reference button 118 on workpiece legs 115, 116 the created workpiece angle. From the workpiece legs 115, 116 the control and reference button 118 during the Forming process from its initial position according to FIG. 4 compared the forming die 108 in the upward direction of the double arrow 105 postponed.

5 shows the control and reference button 118 at the initial Workpiece processing at the end of the work movement of forming die 108 and forming die 110, in which on the one of the forming die 108 and the forming die 110 relieved workpiece angle results in a bending angle β of the target size. The LED 127/4 is the active surface of the PSD 128 across from. The reference position of the control and reference button 118 defined by LED 127/4. This Like the PSD 128, it also forms a switching element a switching device 122.

Because of its deflectability in the direction of the double arrow 125 the control and reference button 118 is also able to on both workpiece legs 115, 116 of the created workpiece angle support if - differently than shown in Fig. 5 - Its axis of movement indicated by dash-dotted lines in FIG. 4 for example, due to a lateral tilt of the Workpiece angle does not coincide with its bisector. The one with such a compensatory movement in the direction the double arrow 125 associated displacement of the control and reference button 118 in the direction of the double arrow 105 is both in the initial as well as in subsequent workpiece machining negligible.

At the initial workpiece machining described above LED 127/4 is switched on following workpiece machining. It gets below from its starting position of the PSD 128 at the level of the PSD 128, the tax and Reference button 118 its previously defined reference position on. The light emitted by the LED 127/4 hits the active area of the PSD 128 and generates a photo stream, due to whose the machine control 23 in one the working movement of forming die 108 and forming die 110 Senses is driven. The light source 127 and the PSD 128 consequently serve as a position detector for detecting the reference position of the control and reference button 118.

The reference position of the. Defined by the LED 127/4 Control and reference button 118 can at least when editing of workpieces from the same batch, i.e. of Workpieces with identical springback behavior are retained become. There is then always a workpiece angle, the Bending angle β has exactly the target size. Because of the proportionate wide lateral distance between the points of the support of the control and reference button 118 on the workpiece 14 of its bending line is suitable for the control and reference button 118 especially for use cases where To create workpiece angles with relatively small bending angles are.

Should workpieces with changed springback behavior machined are and / or should be workpiece angles with a larger one or smaller bend angles are created accordingly changed reference position of the control and reference button 118 to be defined. The hiring can the reference position of the control and reference button 118 done that now with an initial workpiece machining no longer the LED 127/4 as before, but rather one of the other LEDs 127/1, 127/2, 127/3, 127/5 the PSD 128 is assigned. Additionally or alternatively, the PSD 128 by correspondingly moving the PSD bracket 129 in the direction of the double arrow 105 are shifted. For this purpose it is only to loosen the clamping screw 131 and after moving of the PSD bracket 129 again. That way can also before an initial workpiece machining a mutual rough adjustment of the light source 127 as well as the PSD 128.

In the sense of a high accuracy of the bending angle reproduction acts both in the case of the device according to FIGS. 2 and 3 and also in the case of the device according to FIGS. 4 to 6 of From the fact that with the position of the stamp 8, 108 different control buttons 18, 118 or with the position of the reference button different from the forming die 8, 108 19, 118 a parameter for defining the time of termination the working movement of forming punch 8, 108 and forming die 10, 110 is used, which is independent of the Conditions directly at the tip of the forming die 8, 108. This is advantageous in that conditions are immediate thereby indefinitely at the tip of the forming die 8, 108 are that when bending workpieces 14 - how illustrated and exaggerated in Fig. 3 - in the area the bevel gives a radius and consequently the "apex" of the bending angle is not clear through the tip of the forming die 8, 108 is definable.

Claims (14)

1. Method for producing angular workpieces, in particular angular sheets, having two workpiece sides (15, 16; 115, 116) which extend at a bending angle (β) relative to each other, a upper forming die (8, 108) and a bottom forming die (10, 110) which is associated therewith being moved relative to each other in a working movement with the workpiece (14) to be processed being bent, and an angular workpiece having the desired size of the bending angle (β) being produced during an initial workpiece processing operation, characterised in that,
   during the initial workpiece processing operation, a reference position is defined as such for at least one control probe (18, 118), in which position there is provided an angular workpiece having the desired size of the bending angle (β), in that,
   during one or more subsequent workpiece processing operations, the control probe (18, 118) is positioned, during the working movement of the upper forming die (8, 108) and the bottom forming die (10, 110), against at least one of the workpiece sides (15, 16; 115, 116) of the angular workpiece(s) which has/have then been produced, and can be moved in the state coupled with the associated workpiece side(s) (15, 16; 115, 116) under the action of the upper forming die (8, 108) and/or the bottom forming die (10, 110), and in that the working movement of the upper forming die (8, 108) and the bottom forming die (10, 110) is ended as soon as it has been established, by position detection, that the control probe (18, 118) assumes the reference position thereof defined during the initial workpiece processing operation.
2. Method according to claim 1, characterised in that, during the initial workpiece processing operation, at least one reference probe (19, 118) is positioned, during the working movement of the upper forming die (8, 108) and the bottom forming die (10, 110), against at least one of the workpiece sides (15, 16; 115, 116) and can be moved in the state coupled with the associated workpiece side(s) (15, 16; 115, 116) under the action of the upper forming die (8, 108) and/or the bottom forming die (10, 110), and in that the reference position of the control probe (18, 118) is defined as such with reference to that position of the reference probe (19, 118) which the reference probe (19, 118) assumes at the end of that working movement of the upper forming die (8, 108) and the bottom forming die (10, 110) which brings about the production of the angular workpiece having the desired size of the bending angle (β).
3. Method according to either of the preceding claims, characterised in that at least one reference probe (118) is used simultaneously as a control probe (118), and the working movement of the upper forming die (108) and the bottom forming die (110) is ended during the workpiece processing operation(s) following the initial workpiece processing operation as soon as the probe which is used simultaneously as a reference probe (118) and control probe (118) assumes the reference position thereof defined during the initial workpiece processing operation.
4. Method according to any one of the preceding claims, characterised in that it is carried out at least partially in a computer-controlled manner.
5. Machine for carrying out the method according to any one of the preceding claims, having a upper forming die (8, 108) and a bottom forming die (10, 110) which is associated therewith, the upper forming die (8, 108) and the bottom forming die (10, 110) being able to be moved relative to each other by means of a controllable drive in a working movement with the workpiece (14) to be processed being bent, characterised by at least one control probe (18, 118) which, at least during the workpiece processing operation(s) following the initial workpiece processing operation, can be positioned, during the working movement of the upper forming die (8, 108) and the bottom forming die (10, 110), against at least one workpiece side (15, 16; 115, 116) of the angular workpiece produced and can be moved in the state coupled with the associated workpiece side(s) (15, 16; 115, 116) under the action of the upper forming die (8, 108) and/or the bottom forming die (10, 110),
   by a device (20, 120) by means of which a reference position can be defined as such for the control probe (18, 118) during the initial workpiece processing operation, in which position there is provided an angular workpiece having the desired size of the bending angle (β) and
   by a switching device (22, 122) which comprises a position detector (21; 127, 128) for detecting the position of the control probe (18, 118) and which, during the workpiece processing operation(s) following the initial workpiece processing operation, can be switched to a switching state which brings about the completion of the working movement of the upper forming die (8, 108) and the bottom forming die (10, 110) as soon as it has been established, by the position detector (21; 127, 128), that the control probe (18, 118) assumes the reference position thereof defined during the initial workpiece processing operation.
6. Machine according to claim 5, characterised in that the device (20, 120) for defining the reference position of the control probe (18, 118) comprises at least one reference probe (19, 118) which, at least during the initial workpiece processing operation, can be positioned, during the working movement of the upper forming die (8, 108) and the bottom forming die (10, 110), against at least one workpiece side (15, 16; 115, 116) of the angular workpiece produced and can be moved in the state coupled with the associated workpiece side(s) (15, 16; 115, 116) under the action of the upper forming die (8, 108) and/or the bottom forming die (10, 110), the reference position of the control probe (18, 118) being able to be defined with reference to that position of the reference probe (19, 118) which the reference probe (19, 118) assumes during the initial workpiece processing operation at the end of that working movement of the upper forming die (8, 108) and the bottom forming die (10, 110) which brings about the production of the angular workpiece having the desired size of the bending angle (β).
7. Machine according to claim 5 or 6, characterised in that the reference position of the control probe (18, 118) can be defined by means of a switching element (21; 127/1, 127/2, 127/3, 127/4, 127/5) of the switching device (22, 122), which switching element can be actuated by means of the control probe (18, 118), which assumes the reference position thereof, with the switching device (22, 122) being moved over into a switching state which brings about the completion of the working movement of the upper forming die (8, 108) and the bottom forming die (10, 110).
8. Machine according to any one of claims 5 to 7, characterised in that at least one reference probe (118) is provided simultaneously as a control probe (118), and in that, during the workpiece processing operation(s) following the initial workpiece processing operation, the switching device (122) can be moved over into a switching state which brings about the completion of the working movement of the upper forming die (108) and the bottom forming die (110) as soon as the probe provided simultaneously as a reference probe (118) and a control probe (118) assumes the reference position thereof defined during the initial workpiece processing operation.
9. Machine according to any one of claims 5 to 8, characterised in that the drive of the upper forming die (8, 108) and/or the bottom forming die (10, 110) can be controlled by means of the switching device (22, 122).
10. Machine according to any one of claims 5 to 9, characterised in that the reference position of the control probe (18, 118) can be defined in a variable manner.
11. Machine according to any one of claims 5 to 10, characterised in that the device (120) for defining the reference position of the control probe (118) and the switching device (122) have at least one common light source (127) and/or at least one common optical sensor (128), the reference position of the control probe (118) being defined by a location as such of the light source (127) and/or the optical sensor (128), and the light source (127) and the optical sensor (128) forming a position detector and/or switching elements of the switching device (22, 122), and the light source (127) and the optical sensor (128) being able to be moved relative to each other in the state coupled with the control probe (118) during the workpiece processing operation(s) following the initial workpiece processing operation.
12. Machine according to any one of claims 5 to 11, characterised in that the light source (127) and/or the optical sensor (128) can be moved in the state coupled with at least one reference probe (118) during the initial workpiece processing operation, and the reference position as such of the control probe (118) is defined by the location as such of the light source (127) and/or the optical sensor (128) at the end of that working movement of the upper forming die (108) and the bottom forming die (110) which brings about the production of the angular workpiece having the desired size of the bending angle (β).
13. Machine according to any one of claims 5 to 12, characterised in that the light source (127) and the optical sensor (128) can be moved relative to each other during the initial workpiece processing operation in order to define the reference position as such of the control probe (118) and/or during the subsequent workpiece processing operation(s), and the light source (127) has a plurality of light units (127/1, 127/2, 127/3, 127/4, 127/5) which are consecutive in the direction of the relative movement mentioned and which can be switched on and off separately, and/or the optical sensor (128) has a plurality of sensor units which are consecutive in the direction of the relative movement mentioned.
14. Machine according to any one of claims 5 to 13, characterised by a computer-supported machine control (23).

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