Method for manufacturing a slotted tube

Abstract

The present invention relates to a method for manufacturing a slotted tube (1) from a metal flat (2), particularly a sheet metal, wherein the flat is progressively shaped along the circumferential direction of the slotted tube (1) to be produced by means of at least one bending tool (3) and at least one external bottom tool (4) through a plurality of separate bending steps; wherein, a plurality of positions of each bending step and a plurality of insertion depths of the bending tool (3) are first pre-calculated, and then the metal flat (2) is progressively shaped into the slotted tube (1) based on the pre-calculation, wherein, after each of the plurality of bending steps, a target-actual value comparison of the distance between the two edges (6a, 6b) of the metal flat (2) and / or between one of the two edges (6a) of the metal flat (2) and the axial centerline (7) is performed at at least one position arranged along the longitudinal extension of the metal flat (2), and, in case of deviation, a correction value is determined for subsequent bending steps by means of a correction algorithm, and the insertion depth of the bending tool (3) is then adjusted with the correction value.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing slotted tubes by forming metal flats, particularly sheet metal, by progressively forming the flats along the circumferential direction of the slotted tube to be produced through multiple separate bending steps using at least one bending tool and at least one external bottom tool; the invention also relates to slotted tubes (Schlitzrohr) manufactured by the method according to the invention. Background Technology

[0002] Thick-walled pipes, such as those used in piping applications, are typically manufactured by progressively shaping flat stock into what is known as slotted pipe. For this purpose, the flat stock is first shaped into a slotted pipe, also called a pipe semi-finished product, along its entire length, and then welded by introducing longitudinal weld seams.

[0003] Flat bars are typically formed in two steps. The first step creates a semi-finished product with a polygonal profile. Then, in the second step, an expander is used to achieve a nearly circular cross-sectional profile. However, for thick-walled tubes, there is a risk of overloading the expander tool at this stage.

[0004] With the aid of a bending tool and two supports or bottom tools, for example in the form of a lower beam, the flat material is partially formed in the first forming step described above, and the final desired shape of the workpiece is achieved through a series of such forming operations.

[0005] This forming process is typically based on empirical values ​​and mathematical considerations. Because the corresponding metal flats exhibit locally varying strengths and thus correspondingly different forming characteristics, the industrial manufacturing of such slotted tubes is an extremely complex process due to various interfering variables, such as variations in sheet thickness and batch variations.

[0006] Therefore, there remains a desire in the industry to automate this complex molding process in order to produce tube cross-sections with the desired profile, preferably with the smallest possible deviation from the roundness of the cross-section, and with the desired shape along the entire length.

[0007] For example, an apparatus and method for forming flat material into slotted tubes or tube semi-finished products are known from patent document DE 10 2011 009 660 A1. The apparatus includes at least one internal forming tool and at least one external forming tool. The internal forming tool is used to progressively form the flat material at least stepwise in the circumferential direction of the cross-section of the slotted tube or tube semi-finished product to be produced. The external forming tool is used to form the flat material from the outside. At least one light source and at least one receiver for measuring at least the inner contour of the slotted tube or tube semi-finished product are connected to at least one internal forming tool. By continuously tracking the results of contour measurements at each forming step, this apparatus enables efficient process management and controlled forming of starting material into slotted tubes with defined contours or shapes, allowing for faster and more accurate compensation of deviations and significantly more reliable and precise manufacturing of formed sheet metal structures. However, this type of adjustment presupposes knowledge of the current tube contour detected by an optical measurement system. This optical measurement system must be complexly integrated into the corresponding tool.

[0008] Furthermore, Chinese patent application CN 110102607 A discloses a method for manufacturing slotted tubes according to the so-called JCO process. In this method, a sequence of bending steps is determined for the tube, wherein each individual step in a plurality of bending steps is repeated multiple times, starting from a “safe” indentation depth, until a pre-calculated distance is reached from the center of the step to a point near the edge, or until a pre-calculated radius is displayed by a measuring bridge used. All subsequent slotted tubes are then manufactured based on this sequence. Summary of the Invention

[0009] Therefore, the object of the present invention is to provide an improved method for manufacturing slotted tubes compared with the prior art, and in particular to provide a method for manufacturing slotted tubes that allows adjustment throughout the circumference.

[0010] According to the present invention, this objective is achieved by the method according to the present invention.

[0011] According to the method for manufacturing slotted tubes from metal flats, particularly sheet metal, the flats are progressively shaped along the circumferential direction of the slotted tube to be produced by means of at least one bending tool and at least one bottom tool located on the outside through multiple separate bending steps; wherein, multiple positions of each bending step and multiple insertion depths of the bending tool are first calculated in advance, and then the metal flats are progressively shaped into slotted tubes based on the pre-calculation.

[0012] The method is characterized in that, after each of the multiple bending steps, a target-actual value comparison of the distance between the two edges of the metal flat and / or between one of the two edges of the metal flat and the axial centerline is performed at at least one location arranged along the longitudinal extension of the metal flat, and, in the event of a deviation, a correction value is determined for subsequent bending steps using a correction algorithm, and the insertion depth of the bending tool is then adjusted with the correction value.

[0013] According to the method of the invention, instead of probing the entire inner contour or a portion thereof as is customary in the prior art, the state of the edges of the metal flat sheet during the process of shaping it into a slotted tube is progressively controlled by determining the edge distance between the two edges of the metal flat sheet and / or the distance between one of the two edges of the metal flat sheet and the axial centerline after each of the multiple bending steps. For this purpose, laser sensor elements with a laser source and a laser detector can be advantageously used, and / or computer-supported cameras can be used, which perform distance measurements through a suitable evaluation procedure. Additionally and / or alternatively, the edge distance between the two edges and / or the distance between one of the two edges of the metal flat sheet and the axial centerline can be determined ultrasonically after each of the multiple bending steps. Target distance values ​​for the entire shaping process can be determined by pre-calculating multiple positions for each bending step and the corresponding required insertion depth. Based on these target positions and the subsequently determined actual positions, correction values ​​can be determined for subsequent bending steps using a correction algorithm when deviations occur, so that the required insertion depth of the bending tool can then be adjusted with this correction value. Another advantage of the method according to the invention is that corrections can be performed after the first bending step performed with the bending tool, thus advancing the process by one step compared to methods known in the prior art. In summary, this enables incremental, real-time adjustments that ensure exceptionally high profile fidelity across the entire circumferential direction. This high profile fidelity has a particularly favorable effect on ellipticity, which can be maintained within a very narrow parameter window due to continuous process adjustments.

[0014] Since contour fidelity can now be achieved across the entire circumference of the slotted tube, the expander tool can be loaded more evenly, especially in cases where the wall thickness of the thick-walled tube is at least 6.0 mm, preferably at least 15.0 mm, more preferably at least 20.0 mm or more, thereby reducing the risk of expander tool overload.

[0015] Furthermore, due to the high profile fidelity across the entire circumference, there is no need to repeat individual bending steps. Therefore, it is advantageous to specify that each of the multiple bending steps is performed only once. This enables particularly high production cycles in manufacturing.

[0016] Further advantageous embodiments of the invention are presented below. Features listed separately below can be combined with each other in a technically meaningful manner and can define other embodiments of the invention. Furthermore, the features given below are further described and explained in the specification, wherein further preferred embodiments of the invention are shown.

[0017] In the context of this invention, the term "edge" is understood as the end face of a metal flat that extends along the longitudinal extension of the metal flat.

[0018] At least one edge, preferably two edges, of the metal flat sheet can in principle be constructed as straight edges, meaning that an "edge" is understood as an end face constructed perpendicular to one of the two sides of the metal flat sheet. Thus, such an edge has two edge points that can be detected by a sensor.

[0019] However, in an advantageous variant embodiment, at least one edge, more preferably two edges, of the metal flat has a geometry optimized for subsequent welding processes, comprising two, three, or n sub-end faces, wherein two adjacent sub-end faces enclose an angle. Thus, the edge formed in this way has at least three, four, or n edge points that can be detected by sensors to determine the distance between the two edges of the metal flat and / or between one of the two edges of the metal flat and the axial centerline. Which edge points are considered relative to each other can then be progressively changed based on the accessibility or identifiability of the edge points by the laser sensor and / or computer-supported camera unit.

[0020] This method is applicable to a particularly wide range of products. Thus, the metal flats advantageously have a width of 0.2 m to 10 m, more preferably 0.8 m to 8 m, most preferably 1.0 m to 6.0 m, and a thickness of 5.0 mm to 100 mm, more preferably 6.0 mm to 50 mm.

[0021] In the context of this invention, the term "width" is understood as the radial extension of the metal flat strip, formed along the slotted tube to be produced through multiple bending steps.

[0022] In a preferred variant embodiment, a target-to-actual value comparison of the distance between the two edges of the metal flat and / or between one of the two edges of the metal flat and the axial centerline is performed at at least two, more preferably at least three, or even more preferably more locations arranged along the longitudinal extension of the metal flat, so that the axial length of the slotted tube to be produced can be independently adjusted segmentally.

[0023] Advantageously, the measured values ​​of the actual distances between the two edges of the metal flat and / or between one of the two edges of the metal flat and the axial centerline are transmitted to the control unit, which then performs a target-to-actual distance comparison and, in the event of a deviation, determines a correction value for subsequent bending steps using a correction algorithm. Thus, the control unit controls and adjusts the metal flat to be formed into a slotted tube in a fully automated manner.

[0024] Particularly advantageously, the measurement of the actual distance between the two edges and / or between one of the two edges and the axial centerline is performed by a laser sensor device and / or a computer-supported camera unit that is particularly preferably signal-connected to the control unit.

[0025] On the other hand, the present invention also relates to a slotted tube manufactured by the method according to the present invention. Attached Figure Description

[0026] The invention and its technical environment are further explained below with reference to the accompanying drawings and embodiments. It should be noted that the invention is not limited to the illustrated embodiments. In particular, unless explicitly stated otherwise, certain aspects of the facts explained in the drawings and / or examples may be extracted and combined with other components and knowledge in this specification and / or the drawings. It should be particularly noted that the drawings or examples, and especially the dimensions shown, are merely illustrative. The same reference numerals denote the same objects, and therefore explanations from other drawings may be used as supplementary information where necessary. Wherein:

[0027] Figure 1 a to Figure 1 h illustrates the various working steps in the forming process for manufacturing slotted tubes;

[0028] Figure 2 The measurement principle according to the invention in the first variant embodiment is shown;

[0029] Figure 3 The measurement principle according to the invention in the second variant embodiment is shown;

[0030] Figure 4 a to Figure 4 c shows the geometric results for a plate with a pre-given wall thickness and a pre-given yield strength under ideal preconditions, based on the assumption that these wall thicknesses and yield strengths are constants; and

[0031] Figure 5 a to Figure 5 c shows the results of the first practical example. Detailed Implementation

[0032] refer to Figure 1 a to Figure 1h, the basic principle of manufacturing a slotted tube 1 from a metal flat 2 is shown by means of eight separate working steps, more specifically bending steps. Here, the metal flat 2 is gradually shaped along the circumferential direction of the slotted tube 1 to be produced by means of at least one bending tool 3 and two external bottom tools through multiple separate bending steps.

[0033] In step a), the flat metal 2 has pre-formed edge regions 5a and 5b. These edge regions 5a and 5b are typically pre-formed using a forming press (not shown). As shown in step b), the forming process begins by inserting the metal flat metal 2 between two supports 4a and 4b of a bottom tool 4 and a bending tool 3, which includes a rod 3a and a bending die 3b. The bending tool 3 can move in a stroke between the two supports 4a and 4b substantially perpendicular to the flat metal 2. The flat metal 2 is then partially formed under the combined action of the supports 4a and 4b and the bending die 3b. In working steps a) to d), the first side of the flat metal 2 is formed into a slotted tube cross-section, while steps e) to h) show the right side of the flat metal 2 being progressively formed into a slotted tube. Both forming processes are typically performed as a series of multiple partial forming steps from the side edges 5a and 5b inwards.

[0034] Figure 2 A modified implementation of the measurement principle is shown. As can be seen from the diagram, in... Figure 1 After each bending step in the bending process shown, a measurement is performed by the laser sensor 8 to determine the actual distance between the two edges 6a, 6b of the metal flat 2 and / or between one of the two edges 6a of the metal flat 2 and the axial centerline 7. Here, the laser sensor 8 detects the detectable edge points 9a, 9b of the corresponding edges 6a, 6b.

[0035] Figure 3 Another variant of the measurement principle is shown. Unlike the first variant, each of the edges 6a, 6b of the metal flat has multiple sub-end faces 10a, 10b. As can be seen from the figure, two adjacent sub-end faces 10a, 10b form a corner and correspondingly form edge points 9a, 9b, which the laser sensor 8 can detect to determine the actual distance between the two edges 6a, 6b of the metal flat 2 and / or between one of the two edges 6a of the metal flat 2 and the axial centerline 7.

[0036] Example

[0037] Comparison example:

[0038] To manufacture a slotted tube with an outer diameter of 813 mm, a wall thickness of 12.7 mm, and a length of 10 m, a metal sheet with dimensions (length × width × height) of 10000 mm × 2554 mm × 12.7 mm and a yield strength of 600 MPa was prepared. A general-purpose bending die with a radius of 120 mm was used as the bending die.

[0039] The number of bending steps and the corresponding insertion depth were pre-calculated based on the material dimensions, yield strength, radius of the bending die used, radius of the bottom tool, bottom tool distance, and elastic modulus parameters. Figure 4 a). Seventeen bending steps were determined for a slit tube with a target slit width of 200.3 mm.

[0040] The edge region is then formed in a conventional manner using a forming press. The sheet metal is then passed between a bending tool and a bottom tool with two supports, and bending steps 1 through 17 are performed as calculated. Because the sheet metal is not ideal in this region in terms of material thickness and yield strength, as assumed in the pre-calculation, the entire forming process in the comparative example resulted in a seam width deviation exceeding 3%.

[0041] Example according to the present invention:

[0042] Unlike the comparative example, after the first bending step performed based on a pre-calculated insertion depth of 18 mm (see... Figure 5 a) A comparison of the target and actual distance values ​​has been performed. To this end, a laser sensor is used to determine the distance between the two edge points 9a and 9b, and additionally, the distance between edge point 9a and the centerline 7. Figure 2 and Figure 3 As shown. The determined distance is compared with the previously calculated target distance, and then a correction algorithm is used to determine the correction value for the subsequent second bending step (see...). Figure 5 a). Then adjust the insertion depth of the second bending step using this correction value, such as Figure 5 As shown in a. Perform subsequent bending steps 3 through 17 in the same manner.

[0043] Table 1 below shows the results of comparative examples and examples according to the present invention against the background of theoretical calculations. From Table 1, it can be clearly seen that the method according to the present invention has a positive effect on the profile of the slotted tube.

[0044] Table 1:

[0045]

[0046] List of reference numerals

[0047] 1. Slit pipe

[0048] 2 Flat bar

[0049] 3. Bending tool

[0050] 3a Bar section

[0051] 3b Bending die

[0052] 4 Bottom Tools

[0053] 4a support

[0054] 4b support

[0055] 5a Edge region

[0056] 5b Edge region

[0057] 6a edge

[0058] 6b edge

[0059] 7. Centerline

[0060] 8. Laser sensor devices

[0061] 9a Edge point

[0062] 9b edge point

[0063] 10a Sub-end

[0064] 10b Sub-face.

Claims

1. A method for manufacturing a slotted tube (1) from a metal flat (2), the method comprising progressively shaping the flat in the circumferential direction of the slotted tube (1) to be produced by means of at least one bending tool (3) and at least one external bottom tool (4) through a plurality of separate bending steps; wherein, First, multiple positions for each bending step and multiple insertion depths of the bending tool (3) are pre-calculated. Then, based on the pre-calculation, the metal flat (2) is gradually shaped into the slotted tube (1) by bringing the two longitudinal edges (6a, 6b) of the metal flat (2) together. After each bending step in the multiple bending steps, a target-actual value comparison of the distance between the two longitudinal edges (6a, 6b) of the metal flat (2) and / or between one of the two longitudinal edges (6a) of the metal flat (2) and the axial centerline (7) is performed at at least one position along the longitudinal extension of the metal flat (2). If a deviation occurs, a correction value is determined for the subsequent bending step using a correction algorithm. The insertion depth of the bending tool (3) is then adjusted with this correction value. Its features are, At least one of the two longitudinal edges (6a, 6b) has at least three edge points (9a, 9b) by means of which a target-to-actual distance comparison is performed, wherein the at least three edge points (9a, 9b) are spaced apart from each other on the thickness of at least one of the two longitudinal edges (6a, 6b).

2. The method according to claim 1, wherein, At least one longitudinal edge (6a, 6b) has at least four edge points (9a, 9b), by means of which a target-to-actual comparison of the distance between the two longitudinal edges (6a, 6b) of the metal flat (2) and / or between one of the two longitudinal edges (6a) of the metal flat (2) and the axial centerline (7) is performed at at least one location along the longitudinal extension of the metal flat (2).

3. The method according to claim 2, wherein, At least one longitudinal edge (6a, 6b) has more than four edge points (9a, 9b), by means of which a target-to-actual comparison of the distance between the two longitudinal edges (6a, 6b) of the metal flat (2) and / or between one of the two longitudinal edges (6a) of the metal flat (2) and the axial centerline (7) is performed at at least one location along the longitudinal extension of the metal flat (2).

4. The method according to claim 1, wherein, At at least two locations along the longitudinal extension of the metal flat (2), a target-to-actual value comparison of the distance between the two longitudinal edges (6a, 6b) of the metal flat (2) and / or between one of the two longitudinal edges (6a) of the metal flat (2) and the axial centerline (7) is performed.

5. The method according to claim 4, wherein, At least three locations along the longitudinal extension of the metal flat (2) are used to perform a target-to-actual comparison of the distance between the two longitudinal edges (6a, 6b) of the metal flat (2) and / or between one of the two longitudinal edges (6a) of the metal flat (2) and the axial centerline (7).

6. The method according to claim 5, wherein, A target-to-actual comparison of the distance between the two longitudinal edges (6a, 6b) of the metal flat (2) and / or between one of the two longitudinal edges (6a) of the metal flat (2) and the axial centerline (7) is performed at more than three locations along the longitudinal extension of the metal flat (2).

7. The method according to claim 2, wherein, At at least two locations along the longitudinal extension of the metal flat (2), a target-to-actual value comparison of the distance between the two longitudinal edges (6a, 6b) of the metal flat (2) and / or between one of the two longitudinal edges (6a) of the metal flat (2) and the axial centerline (7) is performed.

8. The method according to claim 7, wherein, At least three locations along the longitudinal extension of the metal flat (2) are used to perform a target-to-actual comparison of the distance between the two longitudinal edges (6a, 6b) of the metal flat (2) and / or between one of the two longitudinal edges (6a) of the metal flat (2) and the axial centerline (7).

9. The method according to claim 8, wherein, A target-to-actual comparison of the distance between the two longitudinal edges (6a, 6b) of the metal flat (2) and / or between one of the two longitudinal edges (6a) of the metal flat (2) and the axial centerline (7) is performed at more than three locations along the longitudinal extension of the metal flat (2).

10. The method according to any one of claims 1 to 9, wherein, The measurement results of the actual distance between the two longitudinal edges (6a, 6b) of the metal flat (2) and / or between one of the two longitudinal edges (6a) of the metal flat (2) and the axial centerline (7) are transmitted to the control unit. The control unit then performs a target value-actual value comparison of the distance and determines a correction value for the subsequent bending step by means of the correction algorithm if a deviation occurs. Thus, the control unit controls and adjusts the metal flat to be formed into the slotted tube (1) in a fully automatic manner.

11. The method according to any one of claims 1 to 9, wherein, The measurement of the actual distance between the two longitudinal edges (6a, 6b) and / or between one of the two longitudinal edges (6a) and the axial centerline (7) is performed by a laser sensor (8) and / or a computer-supported camera.

12. The method according to claim 11, wherein, The laser sensor (8) and / or the camera are signal-connected to the control unit.

13. The method according to any one of claims 1 to 9, wherein, Each of the multiple bending steps is performed only once.

14. The method according to any one of claims 1 to 9, wherein, The metal flat (2) has a width of 0.2 m to 10 m and a thickness of 6.0 mm to 100 mm.

15. The method according to any one of claims 1 to 9, wherein, The metal flat material (2) is a sheet material.

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