Method for producing open-seam pipes

Abstract

A method for producing open-seam pipes from flat metal products, in particular sheet metal, includes a plurality of individual bending steps using at least one bending tool and at least one externally located lower tool. A plurality of positions of individual bending steps and the insertion depth of the bending tool are calculated in advance. Based thereon the flat metal product is then shaped step-by-step to form the open-seam pipe. After each of the bending steps, a target/actual comparison of the distance between two edges and/or between one of the two edges and the axial center line of the flat metal product is carried out. In case of a deviation, a correction value for the subsequent bending step is determined using a correction algorithm so as then to adapt the insertion depth for the bending tool.

Claims

1. A method for producing an open-seam pipe (1) from a flat metal product (2) with a bending tool (3) and at least one externally located lower tool (4), the method comprising: calculating, in advance, a plurality of positions of individual bending steps and an insertion depth of the bending tool (3); bending the flat metal product (2) step-by-step to form the open-seam pipe (1) based on the advance calculation by bringing together two longitudinal edges (6a, 6b) of the flat metal product (2); carrying out, after each of the individual bending steps, a target/actual comparison of a distance between the two longitudinal edges (6a, 6b) at at least one position arranged along a longitudinal extent of the flat metal product (2) and/or between one of the two longitudinal edges (6a) and an axial center line (7) of the flat metal product (2); and determining, in an event of a deviation, a correction value for a subsequent bending step using a correction algorithm and adapting the insertion depth for the bending tool (3), wherein at least one of the two longitudinal edges (6a, 6b) comprises at least three edge points (9a, 9b) on a basis of which the target/actual comparison of the distance is carried out, and wherein the at least three edge points (9a, 9b) are spaced apart across a thickness of the at least one of the two longitudinal edges (6a, 6b).

2. The method according to claim 1, wherein the at least one of the two longitudinal edges (6a, 6b) has at least four edge points (9a, 9b) on a basis of which the target/actual comparison of the distance is carried out.

3. The method according to claim 1, wherein the at least one of the two longitudinal edges (6a, 6b) has more than four edge points (9a, 9b) on a basis of which the target/actual comparison of the distance is carried out.

4. The method according to claim 1, wherein the target/actual comparison of the distance is performed at at least two positions arranged along the longitudinal extent of the flat metal product (2) between the two longitudinal edges (6a, 6b) and/or between one of the two longitudinal edges (6a) and the axial center line (7) of the flat metal product (2).

5. The method according to claim 1, wherein the target/actual comparison of the distance is performed at at least three positions arranged along the longitudinal extent of the flat metal product (2) between the two longitudinal edges (6a, 6b) and/or between one of the two longitudinal edges (6a) and the axial center line (7) of the flat metal product (2).

6. The method according to claim 1, wherein the target/actual comparison of the distance is performed at more than three positions arranged along the longitudinal extent of the flat metal product (2) between the two longitudinal edges (6a, 6b) and/or between one of the two longitudinal edges (6a) and the axial center line (7) of the flat metal product (2).

7. The method according to claim 1, wherein measurement results of actual distances between the two longitudinal edges (6a, 6b) and/or between one of the two longitudinal edges (6a) and the axial center line (7) of the flat metal product (2) are transmitted to a control unit, which then carries out the target/actual comparison of the distance and, in the event of the deviation, determines the correction value for the subsequent bending step using the correction algorithm, by which the control unit controls and regulates a fully automatic bending of the flat metal product into the open-seam pipe (1).

8. The method according to claim 1, wherein the actual distance between the two longitudinal edges (6a, 6b) and/or one of the two longitudinal edges (6a) and the axial center line (7) is measured by a laser sensor system (8) and/or a computer-assisted camera.

9. The method according to claim 1, wherein each of the plurality of bending steps is carried out only one time.

10. The method according to claim 1, wherein the flat metal product (2) has a width of 0.2 to 10 m and a thickness of 6.0 to 100 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1a to 1h show an illustration of individual working steps in a shaping process for producing an open-seam pipe,

(2) FIG. 2 shows the measuring principle in a first embodiment,

(3) FIG. 3 shows the measuring principle in a second embodiment,

(4) FIGS. 4a to 4c show geometric results under ideal conditions for a sheet with a given wall thickness and a given yield strength under the assumption that these are constant, and

(5) FIGS. 5a to 5c show results from a first practical example.

DETAILED DESCRIPTION

(6) With reference to FIGS. 1a to 1h, the basic principle for producing an open-seam pipe 1 from a flat metal product 2 is shown on the basis of eight individual working or bending steps. The flat metal product 2 is shaped in a step-by-step manner in the circumferential direction of the open-seam pipe 1 being created by a plurality of individual bending steps using at least one bending tool 3 and two external lower tools 4.

(7) In step a), the flat product 2 is shown with edge regions 5a, 5b already pre-shaped. The edge regions 5a, 5b are usually shaped in advance using a shaping press not shown. As step b) shows, the shaping process starts by threading the flat metal product 2 between two counter bearings 4a, 4b of the lower tool 4 and the bending tool 3, which comprises a shank 3a and a bending punch 3b. The bending tool 3 can be displaced stroke-by-stroke in a substantially perpendicular manner to the flat product 2 between the two counter bearings 4a, 4b. In the interaction of the counter bearings 4a, 4b along with the bending punch 3b, the introduction of local shaping into the flat product 2 then takes place. While in the working steps a) to d), the shaping of the first side of the flat product 2 into an open-seam pipe cross-section takes place, in steps e) to h), the step-by-step shaping of the right side of the flat product 2 to form the open-seam pipe 1 is illustrated. Both shaping processes are usually carried out as a sequence of a plurality of local shaping steps from the side edges 5a, 5b inwards.

(8) FIG. 2 shows a variant of the measuring principle. As can be seen from the illustration, after each of the bending steps carried out, as shown in FIG. 1, a measurement is made via a laser sensor system 8 to determine the actual distance between the two edges 6a, 6b and/or between one of the two edges 6a and the axial center line 7 of the flat metal product 2. Thereby, the laser sensor system 8 detects a detectable edge point 9a, 9b of the respective edge 6a, 6b.

(9) FIG. 3 shows a further variant of the measuring principle. In contrast to the first embodiment, each of the edges 6a, 6b of the flat metal product has a plurality of partial end faces 10a, 10b. As can be seen from the illustration, two mutually adjacent partial end faces 10a, 10b each enclose an angle and each form an edge point 9a, 9b, which can be detected by the laser sensor system 8 in order to determine the actual distance between two edges 6a, 6b and/or between one of the two edges 6a and the axial center line 7 of the flat metal product 2.

EXAMPLES

Comparative Example

(10) To produce an open-seam pipe with an outer diameter of 813 mm, a wall thickness of 12.7 mm and a length of 10 m, a sheet with the dimensions (LWH) 10000255412.7 mm, which had a yield strength of 600 MPa, was provided. A universal bending punch with a radius of 120 mm was used as the bending punch.

(11) On the basis of the dimensions, the yield strength of the material, the radius of the bending punch used along with the lower tools, the lower tool distance and the E-modulus parameters, the number of individual bending steps and the corresponding insertion depths (FIG. 4a) were calculated in advance. For an open-seam pipe with a target slit width of 200.3 mm, 17 bending steps were determined.

(12) Then, the edge regions were firstly formed using a shaping press in the conventional manner. The sheet was then threaded between the bending tool and the lower tool with two counter bearings, whereupon the individual bending steps 1 to 17 were carried out as calculated (FIG. 3a). Since the sheet is not ideal over the area in terms of material thickness and in terms of its yield strength, as assumed in the advance calculation, the entire shaping process in the comparative example resulted in a deviation of more than 3% in the slit width.

Example

(13) In contrast to the comparative example, a target/actual comparison of the distance was already carried out after the first bending step, which was carried out on the basis of the insertion depth calculated in advance of 18 mm (see FIG. 5a). For this purpose, the distance between the two edge points 9a, 9b and additionally between the edge point 9a and the center line 7 was determined using the laser sensor system, as shown in FIGS. 2 and 3. The determined distances were compared with the previously calculated target distances, whereupon a correction value for the subsequent second bending step was determined using a correction algorithm (see FIG. 5a). The insertion depth of the second bending step was then adjusted by the correction value, as shown in FIG. 5a. The subsequent bending steps 3 to 17 were carried out in the same manner.

(14) Table 1 below shows the results from the comparative example and the example in accordance with the disclosure against the background of the theoretically calculated values. As can be seen from Table 1, the positive influence of the method in accordance with the disclosure on the contour of the open-seam pipe can be clearly seen.

(15) TABLE-US-00001 TABLE 1 Comparative Calculated example Example Slit width 200.3 207.2 201 Distance 1 861 888 866 Distance 2 861 833 853

LIST OF REFERENCE SIGNS

(16) 1 Open-seam pipe 2 Flat product 3 Bending tool 3a Shank 3b Bending punch 4 Lower tool 4a Counter bearing 4b Counter bearing 5a Edge region 5b Edge region 6a Edge 6b Edge 7 Center line 8 Laser sensor system 9a Edge point 9b Edge point 10a Partial end faces 10b Partial end faces