EP4357042A1 - Bending machine with automatic correction of the position of the sheet metal - Google Patents

Abstract

A round bending machine for round bending a bending section of an object comprises a controller and a device for determining an actual distance of a bending point from a reference point of the round bending machine, wherein the controller is configured to correct the control parameters for conveying the object based on a deviation between the expected and actual distance of the bending point from the reference point.

Description

The invention relates to a bending machine for round bending, also called round rolling, of a sheet metal, in particular a bending machine according to the preamble of claim 1.

Bending machines with at least three rollers or rolls for bending sheet metal or other bendable objects are known from the prior art, with a sheet metal being mentioned below as a representative of other objects to be bent. A sheet metal can have a thickness of typically more than 3 mm and in particular more than 50 mm.

Typically, the sheet metal to be bent is fed into the bending machine from one side. The position of the rollers is adjusted for a bending process so that they exert a force on the sheet metal and bend it accordingly. At least one roller of such a bending machine is motor-driven so that the driven roller feeds the sheet metal through the rollers of the bending machine. The sheet metal is continuously bent as it is fed through the appropriately adjusted rollers.

One challenge when bending a sheet metal is to precisely achieve the desired bending radius and to maintain the start and end points of the sheet metal section to be bent.

Bending machines with three or more rollers are known from the state of the art, which have sensors for tracking or controlling parameters of the bending machine during a bending process. EP477752 describes a bending machine with sensors for determining the position of each roller so that the geometry of the rollers can be determined and corrected. The EP1 644 140 describes a bending machine with sensors for determining the bending radius after a bending process so that the geometry of the rollers can be adjusted or corrected can be. The WO2009/101649 describes a bending machine for bending an elongated workpiece, which has sensors for determining a bending radius at a point on the workpiece that is close to the point on the workpiece that is currently to be bent.

In order to achieve a precise bend, in addition to maintaining the desired bending radius as precisely as possible, it is also necessary to maintain the length of the section of a sheet to be bent, whereby the length of the section to be bent must be measured along the neutral fiber of the sheet.

The position of the rollers relative to each other and the rotation of the driven roller are entered into the control system of the bending machine before the bending process. In bending machines with at least one motor-driven roller, the problem is to convey the sheet metal precisely so that the actual length of the transported neutral fiber of the sheet metal corresponds to the set length and the beginning and end of a section of sheet metal to be bent are reached as precisely as possible.

The conveying of the sheet metal through the bending machine is subject to errors, such as slippage between the driven roller and the sheet metal and compression of the sheet metal on the inside of the radius due to bending, so that the length of the actually conveyed distance deviates from the set length of the conveyance in practice, even if the slippage and/or shortening on the inside of the radius of the sheet metal between the driven roller and the surface of the sheet metal as well as the geometric and material properties are taken into account when determining the control parameters to be entered.

This problem is solved by a bending machine according to claim 1 and a corresponding bending method.

Fig. 1

eine schematische Darstellung der Walzen einer Biegemaschine mit vier Walzen sowie ein zu biegendes Blech;

Fig. 2

eine schematische Darstellung der Position des Blechs in einer Startposition zu Beginn des Biegevorgangs;

Fig. 3

eine schematische Darstellung einer Position des Blechs zur Korrektur der Steuerparameter;

Fig. 4

eine schematische Darstellung einer Position des Blechs, wobei der erste Biegepunkt an der Oberwalze anliegt;

Fig. 5

eine schematische Darstellung einer Position des Blechs zur Korrektur der Steuerparameter;

Fig. 6

eine schematische Darstellung einer Position des Blechs, wobei der Biegevorgang für einen vorgesehenen Biegeabschnitt beendet ist.

The invention is described in more detail below using an embodiment shown in the figures. They show:

Fig.1

a schematic representation of the rollers of a bending machine with four rollers and a sheet of metal to be bent;

Fig.2

a schematic representation of the position of the sheet in a starting position at the beginning of the bending process;

Fig.3

a schematic representation of a position of the sheet for correcting the control parameters;

Fig.4

a schematic representation of a position of the sheet, with the first bending point resting on the top roller;

Fig.5

a schematic representation of a position of the sheet for correcting the control parameters;

Fig.6

a schematic representation of a position of the sheet metal where the bending process for a given bending section is completed.

Fig.1 shows schematically the rollers of a bending machine 1 with four rollers 3 - 6 for rolling an originally planar sheet 2. The bending machine comprises an upper roller 3 and a lower roller 4 typically arranged vertically below it as well as a first side roller 5 and a second side roller 6. The holders of the rollers as well as drives and a control system are not shown.

In the embodiment described here, only the upper roller 3 is motor-driven, the direction of rotation of the upper roller 3 being indicated by the arrow 3a. In alternative embodiments, more than one roller can be driven to convey the sheet 2 to be bent. The geometry of the rollers in relation to one another can be changed. The rollers can be arranged in such a way that they exert a force on the sheet 2 to bend the sheet 2 and the pressure force of the upper roller 3 exerts a sufficiently large force on the sheet 2 so that when the upper roller 3 rotates, the sheet is conveyed in the transport direction 2a, i.e. from right to left in the figure shown. The lower roller 4 rotates in the direction of rotation 4a and the side rollers 5 and 6 each rotate accordingly.

The bending machine 1 further comprises a control system not shown in the figures, which controls, among other things, the geometric arrangement of the rollers relative to one another and the rotation of the driven roller.

In this embodiment, the sheet metal 2 is to be bent using the bending machine 1. The thickness center 2b of the sheet metal 2 is referred to here as the neutral fiber; in the literature it is also referred to as the zero line. When the sheet metal 2 is bent into a curve, the sheet metal material is compressed on the inside of the neutral fiber 2b and stretched on the outside of the neutral fiber 2b. The area of the neutral fiber 2b of a homogeneous sheet metal typically retains the original length as it was before the bend.

If a sheet of metal is to be bent into a certain curve, the bending radius and the target rotation are determined in the conventional way before the bending process begins, whereby the target rotation is the distance of the sheet 2 along the neutral fiber that is to be conveyed by the motor-driven roller. It is known, for example, that the surface area of the sheet 2 on the inside of the bend is reduced by bending into a smaller radius because the sheet 2 is compressed there. The corresponding parameters of the bending machine for bending the sheet 2 into a curve are entered into the control system of the bending machine accordingly. Based on the entered parameters, the machine determines, among other things, the rotation of the driven roller that conveys the sheet through the rollers.

The sheet 2 can have a length and a width of several meters each and a thickness of several millimeters, in particular more than 3 millimeters and more than 50 millimeters.

In the embodiment described here, the originally planar sheet 2 is to be bent into a curve with a constant radius in the bending section between a first bending point x = 100 to the second bending point at x = 1000, whereby the sheet 2 is bent as it is conveyed through the rollers of the bending machine 1. A bending point is the beginning or the end of a section of the sheet that is to be bent into the constant radius, whereby the bending point lies on the neutral axis. The section in the conveying direction 2a in front of the first bending point at x1 = 100, i.e. the section x0 = 0 to x1 = 100, as well as the section behind the second bending point, here x2 = 1000 to x3 = 1100, are not bent in the embodiment described here.

In a further development of the machine, a further section to be bent can be connected to the first bending section. The exact adherence to the start and end of the further section to be bent is achieved by an analogous procedure when conveying sheet metal 2.

In practice, it has been shown that the length of the sheet actually conveyed by the driven roller differs from the length set in the machine control system. This is caused by various effects such as slippage between the driven roller and the sheet.

According to the present invention, the control of the bending machine is corrected during a bending operation so that the actual conveyed distance of the sheet metal has a small deviation between the length set in the machine parameters and the actual conveyed distance.

The bending machine 1 comprises a device, here an optical system, in particular with at least one camera 7, for determining the actual distance of a bending point from a reference point of the bending machine 1. The reference point of the bending machine is one that has a known distance to the roller, here the top roller 3, around which the bending is to take place. In one embodiment, the reference point can be the point on the top roller that rests on the sheet 2 and at which the top roller 3 thus applies the force to convey the sheet onto the sheet. The device is connected to the control of the bending machine 1 and is set up to recognize a bending point or a marking that can be detected by the device 7. The camera 7 is connected to the control of the bending machine. The control is configured and set up to determine the distance of a bending point of the sheet 2 from a reference point. Based on the distance, the control of the bending machine determines the actual position of a bending point relative to a predetermined, i.e. a previously calculated and thus expected distance value.

In the embodiment described here, the first bending point 2c at x1 = 100 is applied to the narrow side of the sheet 2 as an optical marking that can be recognized by the optical system, in the present embodiment by the camera 7. An optical marking can be applied, for example, in a color contrast to the sheet, for example as a colored symbol or as a line of predefined width perpendicular to the neutral fiber 2b.

In the following, the method steps of a bending process according to the invention are described in more detail.

As a first step, see Fig.2 , the sheet metal 2 to be bent is placed in the bending machine 1 so that the sheet metal 2 is in the starting position for an upcoming bending process. The bending machine saves this position as a reference position for the subsequent conveying of the sheet metal 2. The corresponding position of the upper roller 3 can be saved as "0". The reference edge x0 = 0 of the sheet metal is located here at the point of the upper roller 3 driven here, at which the sheet metal 2 is bent into the curve during round bending.

Starting from the starting position, the sheet metal 2 is conveyed in the direction 2a by the rotation of the driven roller 3 by a predetermined distance. The control of the bending machine 1 controls the rotation of the driven roller in such a way that the sheet metal is conveyed by a distance that is smaller than the distance to the first bending point, but is large enough that the marking of the bending point comes into the area captured by the camera 7 and the distance actually conveyed can be determined. In one embodiment, this distance is the distance until the first bending point touches the upper roller minus a predefined distance, the expected distance, for example 1/5 of the diameter of the upper roller 3.

The length of the predefined distance is the expected distance of a bending point (2c, 2d) from a reference point of the bending machine, here the point of contact of the sheet 2 with the upper roller 3, wherein the expected distance is selected such that the next expected bending point 2c, 2d or its marking is reliably detected by the camera 7 and thus the actual distance of the bending point 2c, 2d from the point of contact with the upper roller 3 can be determined.

In practice, it has been found that when conveying the sheet metal 2, the calculated control parameters are adhered to exactly, but the sheet metal 2 is not actually conveyed exactly, for example due to slippage between the upper roller 3 driven here and the sheet metal 2. The actual position of the sheet metal 2 in the bending machine 1 therefore deviates from the previously calculated and expected position, or the actual distance of a bending point 2c, 2d after conveying deviates from the corresponding expected distance.

To correct the position of sheet 2 in the control system with regard to the conveyance of the sheet, it is first conveyed as far as possible, see Figure 3 that the marked bending point 2c has an expected distance 9 to the point of contact with the top roller 3. The predefined and expected distance 9 is typically in the conveying direction 2a shortly before the point of contact of the sheet with the top roller 3, at which the sheet is actually bent. The expected distance can be, for example, 1/5 of the diameter of the top roller 3.

Fig.3 shows a position of the sheet metal in the bending machine 1 after the sheet metal 2 has been conveyed according to the originally entered control parameters so far that the next bending point in the conveying direction 2a or the marking of the bending point, here 2c, is recorded by the camera 7. The bending machine 1 has thus conveyed the sheet metal 2 according to the entered distance, ie the distance to the next bending point 2c minus the predetermined distance 9. In the following numerical example, this predetermined distance 9 has the length 50.

The control of the bending machine 2 receives the captured images from the camera, evaluates them and determines the actual position of the bending point 2c, i.e. the distance of the bending point from the reference point, and thus the deviation of the actually conveyed sheet metal distance from the previously calculated and expected distance.

The sectional view of the rollers, right in Fig.3 , shows the distance 9 calculated in the control and thus expected, i.e. the distance 9 of the bending point 2c expected according to the control parameters and the actual position of the sheet 2, ie the actual distance 10 of the bending point 2c from the contact point 8 of the sheet 2 with the upper roller 3, whereby the actual distance 10 of the bending point 2c of the sheet deviates from the expected distance 9.

In an exemplary embodiment, the first bending point x1 = 100 from the left edge of the sheet. The calculated and therefore expected distance 9 of the bending point is 50 from the contact point 8 of the upper roller 3 with the sheet 2, i.e. the sheet 2 was conveyed by the distance (x1 - 50) = 100 - 50 from the upper roller 3 according to the control parameters. The bending point 2c should therefore be expected to have a distance of 50 from the contact point 8 with the upper roller 3.

The actual distance 10 of the bending point 2c from the contact point 8 of the sheet 2 with the top roller 3 is determined by the device for determining the distance based on an image from the camera 7. To do this, the device's camera 7 captures the marking of the bending point 2c and supplies the corresponding data to the control system. Based on this data, the control system determines that the actual distance of the bending point from the contact point with the top roller 3 is, for example, 48. Based on the actual value determined, the control system corrects the parameter for the subsequent conveying so that the further conveying of the sheet is based on the corrected control parameters. Since in this numerical example the actual distance of the bending point 2c is not 50, as expected, but actually 48, as determined with the camera, the value of the distance already conveyed in the bending machine control system is adjusted accordingly to 52.

It should be noted that the further conveying of the sheet 2, for example conveying the sheet until the bending point 2c is on the top roller 3, is also subject to errors. However, the incorrectly conveyed distance is smaller than without the correction of the control parameter described above, so that the error in conveying the sheet is reduced and the bending point of the sheet is maintained more precisely.

In a further developed embodiment, the control determines the slip during the conveying of the sheet 2 from the calculated conveying distance and the determined deviation and takes this into account when calculating the further conveying of the sheet 2 in order to further minimize a deviation during the conveying of the sheet 2.

Fig.4 shows the position of the sheet metal 2 in the bending machine 1 after the sheet metal has been conveyed according to the corrected control parameters so far that the bending point 2c is at the point of contact with the upper roller 3. As the sheet metal 2 is conveyed further, the rollers of the bending machine 1 cause the sheet metal 2 to be bent round. The sheet metal is further conveyed by the driven roller, here the upper roller 3, according to the entered control parameters.

Fig.5 shows schematically the rollers of the sheet metal bending machine 1 and the sheet metal 2. According to the entered control parameters, the sheet metal 2 is to be bent in the section x1 = 100 to x2 = 1000, whereby the sheet metal 2 is in turn conveyed to an expected distance 9.

As described above with regard to the actual position of the sheet 2 and the first bending point 2c, the sheet 2 was conveyed over a distance which is the length of the bending section minus an expected distance 9, so that the next bending point 2d also has an expected distance 9 to the point of contact 8 of the sheet with the top roller 3. The expected distance 9 can be individual for a distance, but such that a bending point 2c, 2d or a marking thereof lies in the area that can be detected by a camera 7. The expected distance for the second conveying can thus be smaller than the expected distance as a percentage of the conveyed distance. In one embodiment, the slip between the sheet 2 and the driven top roller 3 can be determined based on previous conveying of the sheet and thus the value of an expected distance of an upcoming conveying process can be calculated from the deviation between the expected and actual distance, so that the deviation from the expected distance becomes smaller.

The actual position of the sheet metal 2 can also deviate from the expected position in the vertical direction during bending, typically if the actual properties of the sheet metal 2 deviate from the expected/assumed properties. Accordingly, the actual position of the bending point 2c, 2d or its marking also deviates from an expected position in the vertical direction. In this case, the determined position of the bending point is adjusted to the expected sheet metal shape. projected, whereby the projection is defined by the shortest path to the expected sheet shape and is thus perpendicular to the expected sheet shape. If the projection of a bending point in the direction of the neutral fiber lies outside the sheet, i.e. the sheet is too short, the neutral fiber is extrapolated accordingly for the calculation of the distance 9.

The actual distance 10 of the sheet 2 from the point of contact with the top roller and thus the actual length already conveyed is determined by means of the camera 7 as soon as the sheet has been conveyed by the distance to the expected distance 9. Based on the determined actual distance 9, at least the value of the distance of the bending point 2d from the point of contact with the top roller 3 stored in the bending machine 1 is corrected by the determined deviation from the expected distance value.

As mentioned above, the slip between the top roller 3 and the sheet 2, which can be determined from the determined deviation, can be taken into account for the conveying of the sheet 2.

Subsequently, the sheet 2 is conveyed further in the same direction 2a based on the corrected value until the entire section to be bent is bent, i.e. the bending point 2d is in contact with the top roller 3, see Fig.6 .

The beginning and end of the section of sheet 2 to be bent to a specified radius, i.e. from x1 = 100 to x2 = 1000, were more precisely maintained in this way.

List of reference symbols

1

Bending machine

2

sheet

2a

Transport direction of the sheet

2 B

neutral fiber of the sheet

2c

first bending point of the sheet

2d

second bending point of the sheet

3

Top roller

3a

Arrow

4

Lower roller

5

first side roller

6

second side roller

7

Camera of a device for determining the distance between a bending point of the sheet and a reference point of the bending machine

8th

Point of contact of the sheet 2 with the top roller 3, reference point

9

Expected distance of the bending point to the contact point of the top roller 3 with the sheet 2/reference point

10

actual distance of the bending point to the reference point

Claims (11)

Round bending machine (1) for round bending a bending section of an object (2) with - at least three rollers (3 - 6), one of the rollers being motor-driven, and - a control for controlling the drive of the motor-driven roller (3) of the round bending machine (1) and - a device (7) for determining an actual distance of a bending point (2c, 2d) of the object (2) to a reference point of the round bending machine (1), the distance being determined along the neutral fiber (2b) of the object (2), and - wherein the control is arranged to correct the control of the motor-driven roller (3) based on the actual distance. Round bending machine (1) according to claim 1, wherein the device (7) for determining the actual distance of a bending point (2c, 2d) of the object (2) comprises a system for optically determining the bending point (2c, 2d). Round bending machine (1) according to claim 2, wherein the device for optically determining the bending point (2c, 2d) is arranged to recognize an optical marking on the object (2) and to determine the actual distance to the reference point of the round bending machine (1). Round bending machine (1) according to one of the preceding claims, wherein it is designed to convey the object (2) to an expected distance of a bending point (2c, 2d) from the reference point, to determine the actual distance of the bending point (2c, 2d) from the reference point and to correct parameters of the control based on the difference between the expected and actually determined distance. A round bending machine (1) according to claim 4, further configured to convey the article (2) until it reaches the bending section based on corrected parameters of the control system. A round bending machine (1) according to any one of the preceding claims, wherein the controller is configured to determine the slippage when conveying the object (2) based on the difference between the expected and actual distance. Round bending machine (1) according to claim 6, wherein the control is arranged to take the slip into account when determining further conveying of the object 2. A round bending machine (1) according to any one of the preceding claims, wherein the object is a sheet metal. Round bending machine (1) according to claim 8, wherein the sheet has a thickness of more than 3 mm and in particular more than 50 mm. Method for round bending a bending section of an object (2) with a round bending machine (1), comprising the steps: - conveying the object (2) to an expected distance of a bending point (2c, 2d) of the object (2) from a reference point (8) of the bending machine (1), and - determining the actual distance of the bending point (2c) from the reference point (8) of the bending machine (1), and - changing at least one control parameter of the bending machine (1) based on the difference between the expected and the determined actual distance of the bending point (2c, 2d) from the reference point (8), and - further conveying the object (2) until the entire length of the bending section is reached based on the at least one changed control parameter. Method according to claim 10, wherein determining the actual distance of the bending point (2c, 2d) from the reference point (8) comprises optically detecting a Marking the bending point with a camera (7) and the camera (7) transmits data to a control of the bending machine.

Images