Method for determining a pipe position, method for extruding a pipe and extrusion path

Abstract

The invention relates to a method for determining the pipe position of an extruded pipe (5) in an extruder section (1), comprising the following steps: - Applying a mark in or on a pipe wall of a pipe (5) after the pipe has been issued and before the pipe (5) has been fed to a calibration device (6), wherein the marking is applied at a first circumferential position of the tube (5) by means of a marking device (18), - after the tube (5) passes through the calibration device (6) the tube (5) is measured by a measuring device (10), e.g. an X-ray measuring device, detecting the mark (20) , and outputting a measurement signal (S1), - Detection of the mark (20) in the measurement signal (S1) and determination of a second circumferential position of the mark (20) on or in the pipe wall, - Comparison of the first circumferential position with the second circumferential position and determination of a rotation angle between the circumferential positions. The measurement of the marking can be carried out in particular by the measuring device intended for wall thickness measurement.

Description

[0001] The invention relates to a method for determining a pipe position, a method for extruding a pipe using this method, and an extrusion line.

[0002] In the extrusion of pipes and hoses, particularly those made of plastic, rubber, or composite materials such as aluminum composite pipes, a bulk material is melted in an extruder and extruded into a pipe or hose. The extruded pipe or hose then passes through an extrusion die equipped with an adjustment device—usually in the form of circumferential centering screws—that centers the pipe and sets it to the desired diameter. Afterward, the pipe is calibrated in a calibration and cooling unit using a calibration sleeve and a vacuum tank, and subsequently cooled, for example, in one or more cooling units.Furthermore, after calibration, the pipe or hose is generally measured, in particular for geometric properties such as wall thickness, outer and inner diameter, ovality and eccentricity, as well as for any errors and irregularities, whereby the measurement is carried out in a measuring device, e.g. using ultrasound, X-ray or radar.

[0003] The measurement is generally taken several meters away from the extruder. During this distance, the still-hot, malleable tube or hose can twist, which generally makes it impossible to accurately correlate the circumferential positions between the measurements of the measuring device and an adjustment mechanism of the extruder die. This renders the adjustment and fine-tuning unreliable; therefore, when changes are made to the settings of the extruder die via the adjustment mechanism, e.g., adjusting screws, it is generally necessary to wait for the tube to be transported back to the measuring device in order to determine the effect of the adjustment.

[0004] DE 10 2016 205 137 B4 discloses a method for producing a two- or three-dimensionally bent part from a cut-to-length tubular or rod-shaped workpiece using a numerically controlled device. In this process, the workpiece is brought into a target rotational position with respect to its longitudinal center axis by means of a mark on its circumferential surface before a bending operation and is then bent. For this purpose, an end section of the workpiece is clamped in a clamping device of the bending machine, the clamping device being rotatable about an axis of rotation and movable parallel to the axis of rotation by means of a rotary unit.Accordingly, a method for an automatic alignment operation is provided in which the marking is detected by means of a camera system and rotational position information is determined from at least one measurement image of the camera system in order to control the rotation unit depending on the determined rotational position information for rotating the clamped workpiece.

[0005] DE 10 2021 111 868 A1 describes a cutting and measuring device for an extrusion line for the production of profile sections, in particular pipe sections, with a slide that is adjustable on a guide device along a transport direction. A clamping device for clamping a profile guided along the transport direction is provided on the slide, and the slide with the clamping device engaged is adjustable along the transport direction. Furthermore, a frame rotatable in the circumferential direction about an axis of symmetry is provided on the slide. A cutting device is also mounted on the frame and rotatable with the frame in the circumferential direction about the axis of symmetry for cutting profile sections from a mounted profile.

[0006] The invention is therefore based on the objective of creating a method for determining a pipe position that enables or improves the compensation of pipe irregularities.

[0007] This problem is solved by a method according to claim 1. Furthermore, a method for extruding a tube and an extrusion section are provided. The methods according to the invention can be carried out, in particular, with the extrusion section according to the invention. The tube position is determined, in particular, by an angle of rotation and / or a circumferential position.

[0008] According to the invention, a clear assignment of the circumferential positions recorded at the measuring point to the extrusion tool with the centering screws arranged there is thus possible. This is advantageous because the settings for pipe centering are made directly on the tool.

[0009] The invention aims to enable a clear orientation of the tube along the extrusion path, so that the measurements of the measuring device can be traced back to the position on the tool or on the setting device. For this purpose, the invention provides for a marking to be applied or formed on the tube after extrusion and before it is fed to the calibration and cooling device, which can subsequently be detected by the measuring device.

[0010] Thus, the pipe is marked by a marking device with a mark that is formed in or on the pipe at a first circumferential position, e.g., applied. Subsequently, the pipe with the mark passes through the calibration and cooling device to the measuring device. In the measuring device, the pipe is measured for the relevant pipe properties in the usual manner. According to the invention, it is recognized that the measuring device can also detect the mark and determine a second circumferential position of the mark. Thus, a relative adjustment, in particular a rotation angle of the pipe, can be determined by comparing the first circumferential position of the mark on the marking device and the second circumferential position of the mark in the measuring device. Thus, the pipe properties and / or irregularities determined in the measuring device, e.g.,An eccentricity and / or wall thickness irregularity can be directly assigned to the respective circumferential position in the marking device. Since the marking device is located close to or directly adjacent to the adjustment device, the first circumferential position can also be assumed to be directly on the adjustment tool.

[0011] Thus, according to the invention, a correct assignment of the circumferential positions is made possible, which allows the adjusting device, in particular adjusting screws on the extrusion tool, to be appropriately controlled.

[0012] Therefore, when determining, for example, an eccentricity, it is no longer necessary to first make an adjustment to the extrusion die and then wait for the pipe to pass several meters after the adjustment to reach the measuring device in order to determine the effects of the correction. Pipe eccentricity refers specifically to the unevenness of a pipe's wall thickness along its circumference. It is, in particular, a measure of how much the pipe wall deviates from ideal circular uniformity.

[0013] According to the invention, the determined eccentricity and irregularity can thus be directly assigned to the respective angular position of the tube on the tool and the appropriate compensation can be carried out.

[0014] The method according to the invention can be carried out with minimal effort; in principle, only the application of the marker and the supplementary evaluation of the measurement signal from the measuring device are required. The measuring device already provided for wall thickness measurement can therefore be used, so that only a software update for evaluating the measurement signals in the relevant control unit is necessary. Thus, the invention is retrofittable and applicable inline.

[0015] According to one embodiment, the marking can be applied to an outer surface of the pipe or the pipe wall, which can therefore be done quickly and easily.

[0016] Furthermore, the marking can also be applied to the pipe wall, e.g., by mechanical insertion, such as by scoring or piercing the marking, so that it is embedded in the pipe wall itself. This has the advantage that the marking is less likely to be affected or wiped away when passing through the calibration and cooling unit and, if applicable, other cooling units and sliding seals.

[0017] Furthermore, the marking can also be formed on the inner surface of the pipe, e.g. with a suitable extrusion tool, thereby achieving a secure placement.

[0018] The marking can be applied by the user, for example, simply by hand with a brush or syringe, which then serves as the marking device. Alternatively, the user can operate a more complex marking device. The marking device can also be controlled by the control unit, allowing the control unit to automatically create the marking, measure it, and then evaluate and determine the angle of rotation. The control unit can also repeat this automatic marking and evaluation process.

[0019] The determined circumferential position and / or the angle of rotation can subsequently be displayed, particularly in a display device, e.g., along with the recorded measurement signals from the measuring device and / or the determined pipe properties and irregularities. Thus, the user can, for example, see a marker at the corresponding determined circumferential position in the available measurement signal, which already displays other pipe properties such as wall thickness and diameter. This allows the user to directly correlate the displayed marker with the actual tool setting, ensuring that the determined wall thickness values ​​also correlate directly with the adjustment devices on the tool.

[0020] According to an advantageous embodiment, the control device or an operating terminal connected to the control device provides a switch from a measuring mode to a detection and alignment mode in order to first search specifically for the marking and to determine and display the circumferential position or the angle of rotation without influencing a measurement, so that the proper measurement of the pipe properties can subsequently be carried out again in a measuring mode.

[0021] The marking material can be a metal or a metal-containing material. For example, it could be conductive silver or conductive paste, which is liquid and can therefore be applied directly to the outer surface. Alternatively, a metal powder, such as a heavy metal powder like tungsten, bismuth, or silver, can be applied, for example, in a solvent or a suitable, fast-drying carrier solution. A heavy metal powder provides reliable identification in the X-ray measurement signal. A metal strip can also be applied. Further examples are described below in the section on embodiments.

[0022] According to the invention, a method for extrusion is further provided in which the tube is extruded and ejected, subsequently marked, calibrated, and measured in the measuring device. The invention may provide that the control unit automatically actuates the adjustment device to compensate for the detected irregularity and / or to modify the tube properties. Thus, an autonomous method, particularly a closed-loop control method, is created that enables automatic correction.

[0023] A wall thickness measuring device, specifically designed as an X-ray measuring device, radar measuring device, or ultrasonic measuring device, can be used as the measuring device. In this case, a marking is designed or applied in such a way that it can be detected by the respective measuring device and subsequently recognized in the measurement signal.

[0024] According to an advantageous embodiment, an X-ray measuring device is used, in particular with several measuring axes, e.g., two or three measuring axes, which thus enables, firstly, a reliable circumferential measurement, in particular a complete measurement of the pipe, and secondly, a determination of the circumferential position of the marking from the measurement signals. It is shown that, in particular, a reliable, especially trigonometric, determination of the position of the marking is possible from measurement signals from two or more measuring axes.

[0025] According to a further embodiment, a radar measuring device is used, which in particular enables a comprehensive wall thickness measurement. A radar measuring device is also understood to be, in particular, a terahertz measuring device; the frequency range of the emitted and detected radar radiation extends in particular from 10 GHz to 10 THZ, especially as frequency-modulated and / or pulsed radar radiation.

[0026] The marker can, in particular, cause shadowing or shielding, and / or reflection of the radar radiation, which can be directly detected in the radar measurement signal. With a comprehensive survey using multiple measurement axes, the position can be directly assigned to the respective radar measuring device or measurement axis. With a rotating measuring device, the position of the marker can be recognized as the respective position of the rotating radar measuring device. For a radar measuring device, a lighter metal, e.g., aluminum, can also be used as the marker, for example, as an adhesive aluminum foil.

[0027] In an ultrasonic measuring device, a marking can be applied that can be clearly identified in the ultrasonic measurement signal, e.g. by absorption or suitable reflection of the ultrasonic waves.

[0028] According to an advantageous embodiment, the conveying speed of the pipe can also be determined. The conveying speed is generally set by a take-off mechanism, e.g., at the end of the extrusion line. However, the rollers or tracks of the take-off mechanism generally operate with slippage, so the exact conveying speed is unknown. The conveying speed, in turn, allows the material cross-section and thus the wall thickness to be adjusted. The conveying speed can be determined with relatively little effort, as this only requires the marking time, the detection time of the marking in the measuring device, and the distance between the marking device and the measuring device. According to an advantageous embodiment, the control device can also adjust the take-off mechanism based on the determined conveying speed, particularly as a closed-loop control system.

[0029] The extrusion line according to the invention advantageously has the following structure in the conveying direction: extruder, extrusion tool, marking device, calibration device, optionally one or more cooling devices, measuring device that measures the pipe as well as detecting the marking, take-off, followed by, for example, a device, e.g., a saw, for cutting the pipe to length.

[0030] The invention is explained in more detail below with reference to the accompanying drawings, which illustrate several embodiments. The drawings show: Fig. 1 an extrusion section according to one embodiment; Fig. 2 a representation of a pipe cross-section on a display device with markings and eccentricity; Fig. 3 a three-axis X-ray measuring device for measuring a pipe; Fig. 4 X-ray measurement diagrams of the three-axis X-ray measuring device during the measurement of a marked pipe; Fig. 5 a radar measuring device with measurement diagram for measuring a pipe and for detecting the marking of a pipe: Fig. 6. An ultrasonic measuring device with a measurement diagram for measuring a pipe and for detecting the marking of a pipe; Fig. 7 a flowchart of an extrusion process according to the invention with a measuring method according to the invention.

[0031] Fig. Figure 1 shows an extrusion line 1 with an extruder 2, which has a feed hopper 2a, an extruder screw 2b, and an extrusion die 4. The extruder receives a bulk material 14, generally a thermoplastic material, e.g., PP or PE, in granular or powder form, via its feed hopper 2a. This material is melted, conveyed through the extruder screw 2b into the extrusion die 4, and forced through an annular opening and exited as a tube 5, which is initially still hot and malleable. The tube 5 is pulled by a vent 12 located at the end of the extrusion line 1 through a calibration device 6, which, in particular, also cools the tube, optionally a downstream cooling device, and through a measuring device 10. The calibration device 6 has a calibration nozzle 7 and a vacuum chamber 8 and can extend over a distance of, for example, 10 m in the conveying direction.

[0032] The extrusion tool 4 is adjustable, e.g., by means of an adjustment device 15 provided on the circumference of the calibration sleeve 7, e.g., with adjusting screws 115, by which the diameter of the tube 5 can be adjusted and eccentricities and out-of-roundness can also be compensated. Furthermore, the calibration sleeve 7 can also be adjusted accordingly.

[0033] The measuring device 10 serves to measure the pipe 5 and outputs measurement signals S1, whereby in particular the wall thickness d of the pipe wall 5a of the pipe 5, an outer diameter Da and an inner diameter Di are continuously measured, especially also completely in the circumferential direction around the pipe 5, i.e. as a full-circumference measurement. Irregularities, defects and inclusions in or on the pipe wall 5a can be detected by the measuring device 10; furthermore, a refractive index n of the material of the pipe wall 5a can advantageously also be determined by a prior calibration measurement with an empty extrusion section 1.

[0034] A central control unit 16 receives the measurement signal S1 from the measuring device 10 and advantageously outputs a setting signal S2 to the extrusion tool 4 and, for example, a control signal S3 to the take-up device 12.

[0035] The tube 5 ejected from the extrusion die 4 is initially molten and plastically deformable. During subsequent calibration, cooling, and transport, the tube 5 can therefore rotate, particularly around its own axis A, so that the circumferential positions when measuring the tube 5 in the measuring device 10 do not correspond to the circumferential positions in the extrusion die 4.

[0036] Fig. Figure 2 shows, by way of example, an eccentricity 22, in which an interior space 21-1 or 21-2 of the tube 5 is offset relative to the tube axis A or axis of symmetry, and thus the wall thickness d is uneven in the circumferential direction. If, therefore, an inaccurate shape is detected on the finished tube 5 in the measuring device 10, e.g., an eccentricity 22 or, for example, a wall thickness d that is too large or too small in places, the determined circumferential position must be assigned to a circumferential position in the extrusion die 4, which is generally difficult. Fig. 2 is in the measuring device 10, e.g., the one in Fig. The eccentricity shown in 2 with a solid line is determined with respect to the interior space 21-2. However, it is first the in Fig. 2. The position of the interior space 21.1 at the extrusion tool 4, shown with a dashed line, is unknown.

[0037] Thus, without further measures, an adjustment or change in the extrusion tool 4 can only be determined subsequently after the passage of the distance B between a first longitudinal position A18 on the extrusion tool 4 and the second longitudinal position A10 on the measuring device 10, i.e. with a time delay and corresponding material waste.

[0038] According to the invention, a mark 20 is applied to the tube 5, which can subsequently be detected in the measuring device 10. The mark 20 is applied to the tube 5 by a marking device 18, which can either be actuated by the user or controlled by the central control unit 16 via a marking signal S4. The marking device 18 is located in the first longitudinal position A18 (path position) between the extrusion die 4 and the calibration and cooling unit 6. Advantageously, the mark 20 is designed in a standardized or defined manner to ensure its unambiguous detection in the measuring device 10.

[0039] The marking 20 is applied, in particular, as an additional material. The marking 20 can be metallic or contain a metal. For example, the marking 20 can be liquid or pasty, i.e., non-solid, such as conductive silver, conductive paste, or a metal powder suspended in a solvent. Furthermore, the marking 20 can also be applied or introduced as a powder or solid, e.g., as a metal sphere. The material of the marking 20 and / or the dimensions of the marking 20 are advantageously adapted to the respective measuring method of the measuring device 10.

[0040] Examples of materials marked 20, which can be readily detected using X-ray measurement techniques, include heavy metals; these are, for example: Tungsten powder, e.g. 2-5 µm and / or 4-5 g, Bismuth or barium sulfate powder, e.g. 4-6 g, where the metal powders are applied, for example, in a solvent such as ethanol, which evaporates quickly or dries quickly and does not attack the material of the pipe wall 5a.

[0041] Furthermore, the metal powder can be incorporated as a paste in a resin, e.g., acrylic resin, with this mixture in turn dissolved in, for example, ethanol. A dispersing agent can be added for better distribution. Additionally, color pigments such as carbon black or iron oxide can be incorporated to improve visibility in daylight.

[0042] The marking 20 can be applied to the outer surface 5b of the tube wall 5a, or within the tube wall 5a, or on an inner surface 5c of the tube wall 5a. It is advantageous to apply the marking to the tube wall 5a, for example by scoring or injecting it through the outer surface 5b into the tube wall 5a, to prevent smudging or wear in the subsequent calibration sleeve 7 and, if applicable, the sliding seals of a subsequent cooling device. Thus, the marking device 18 can, for example, include an injection needle or a knife for scoring; furthermore, it can press a liquid or solid metal body, such as a metal ball, into the still molten tube wall 5a.

[0043] Thus, the marking device 18 is provided in the first longitudinal position A18 of the extrusion section 1; accordingly, the measuring device 10 is provided at the second longitudinal position A10 (second section position) of the extrusion section 1, which is spaced apart by the distance B in the extrusion direction F.

[0044] Fig. Figure 2 shows a cross-section of the pipe 5, which can also be displayed to the user, for example, on a display device 17 connected to the control device 16. The marking 20 is placed at a first circumferential position P1 on the pipe 5, which can be located, for example, at the top of the pipe cross-section, but also at another angular position relative to the vertical. The highest point of the pipe cross-section of the pipe wall 5a, i.e., the intersection of the outer surface 5b with the vertical, can also be uniquely determined in a subsequent measurement in the measuring device 10. This first circumferential position P1, or the angular position of the first circumferential position P1, serves as a reference point for determining a rotation angle alpha.

[0045] The pipe 5 is measured accordingly on the measuring device 10, and the circumferential position P2 of the marking 20 is determined. Furthermore, the first circumferential position P1 can be uniquely determined as a reference point in the measuring device 10, e.g., in this example shown, as the vertical or upper or highest point. Thus, in Fig. 2. A rotation angle alpha of – measured clockwise – e.g., 20°, exists between the first circumferential position P1 and the measured second circumferential position P2. Thus, the tube 5 has rotated 20° counterclockwise, possibly completing one or more further full 360° rotations that are not detected in the measurement and are also irrelevant for the evaluation. According to the invention, it is recognized that the relative position is relevant here, even without knowledge of the exact number and direction of rotation.

[0046] In Fig. Figure 2 additionally shows an eccentricity 22 in the right-hand area of ​​the pipe wall, which can be detected and evaluated by the measuring device and assigned to the corresponding circumferential position in the marking device 18 by the measuring principle according to the invention. Since the marking device 18 is arranged close to the adjusting device 15 of the extrusion tool 4 in the conveying direction F, the circumferential position in the marking device can also be assigned to the adjusting device.

[0047] The user can switch from a measurement mode M1 to a detection and alignment mode M2 ​​at an operating terminal 19 connected to the control unit 16 by entering a switching signal S5, in order to first search specifically for the marker 20 and to determine and display the circumferential positions P1 and P2 or the rotation angle alpha without influencing the pipe measurement, so that the proper measurement of the pipe properties can subsequently be carried out again in a measurement mode M1.

[0048] The measuring device 10 can perform the measurement of the pipe 5 using different measuring principles. It can be configured as, for example, an X-ray measuring device 10a, a radar measuring device 10b, and / or an ultrasonic measuring device 10c, with the precise measurement being carried out according to the different embodiments.

[0049] Fig. 3, Fig. Figure 4 shows the embodiment of an X-ray measuring device 10a. According to Fig. 3. The X-ray measuring device 10a can be designed, in particular, as a three-axis device, i.e., with three X-ray measuring axes 34, shown here as measuring axes 34a, 34b, 34c, wherein each X-ray measuring axis 34 has an X-ray source 35 and an X-ray detector 36. The three X-ray measuring axes 34 are offset by 120° in the measuring plane to enable a complete measurement of the pipe 5.

[0050] Thus, in each X-ray measurement axis 34, the X-ray source 35 emits X-ray radiation 38, corresponding to a set aperture in the X-ray source 35, at an output angle in the measurement plane perpendicular to the tube axis A through the tube 5, so that the X-ray radiation 38 transmitted through the tube 5 is measured by the X-ray detector 36.

[0051] In Fig. Figure 4 shows typical X-ray measurement diagrams 23a, 23b, 23c of the three X-ray measurement axes 34, i.e., 34a, 34b, 34c, as a superimposed overall measurement diagram 23 during the measurement of a pipe 5 with a pipe wall 5a, where the intensity I is plotted against a channel number x or the measurement direction. Thus, each X-ray measurement diagram 23a, 23b, 23c shows an intensity profile with a baseline 40-1 outside the pipe 5, to which a flanking region 40-2 adjoins towards the center with steeply increasing absorption, since the X-ray radiation 38 first detects the outer surface 5b and subsequently increasingly larger areas of the pipe wall 5a. This results in a clear drop in intensity in the flanking region 40-2 towards a minimum value 40-3 at the point just before the pipe interior is detected. When traversing the inside of the pipe, the following results in Fig. 4, starting from the minimum value 40-3 to the right, a typical middle signal range 40-4 with slightly increasing intensity, since the X-ray radiation 38 passes through the tube wall 5a more perpendicularly here, until in the middle of the tube, i.e. when the tube axis A is detected, the measurement diagram is subsequently traversed symmetrically back, as directly from Fig. 4 is evident.

[0052] From the intensity profile of the measurement signal I(x), geometric properties of the pipe 5 or the pipe wall 5a, as well as irregularities such as an eccentricity 22, can be determined and assigned to the positions of the pipe wall by trigonometric determination from the three pipe measurement axes 34. Furthermore, the circumferential position of the mark 20 can be determined. The mark 20 in or on the pipe wall 5a is detected by each of the X-ray detectors 36 of the three X-ray measurement axes 34a, 34b, 34c in a different measurement channel or at a different measurement position x. The three measurement axes thus enable a unique assignment and determination of the circumferential position P2.

[0053] The marker 20 absorbs the X-ray radiation 38, especially when formed with a metal, and can therefore be recognized as a distinct or complete shielding peak 120a, 120b, 120c in the measurement diagram. Thus, the marker 20 in Fig. 4 in the first X-ray measurement diagram 23a of the first X-ray measurement axis 34a in a right-hand area near the minimum value 40-3, in the second X-ray measurement diagram 23b in the middle signal area 40-4, and in the third X-ray measurement diagram 23c near the left-hand minimum value 40-3. From this, the circumferential position P2 of the marking 20 on the pipe wall 5a can be determined, in particular trigonometrically.

[0054] Fig. Figure 5 shows a radar measuring device 10b as a further embodiment of the measuring device 10. The radar measuring device 10b is advantageously again multi-axis, i.e., with several angularly offset radar measuring axes, e.g., ten measuring axes, as in Fig. The line 5 is indicated by several radar transceivers 45. The multiple radar measurement axes thus enable a comprehensive survey; alternatively, one or more radar measurement axes, each with a radar transceiver 45, can rotate around the tube 5. Fig. Figure 5 shows one of the radar measuring axes with a radar transceiver 45 and a reflector 49 provided behind the tube 5. The radar measuring device 10b performs a distance measurement, e.g. with frequency modulation, e.g. FMCW, wherein the radar radiation 138 emitted by the radar transceiver 45 and received after reflection can e.g. be in the frequency range from 10 GHz to 10 THz.

[0055] In Fig. Figure 5 shows two radar measurement diagrams 123a and 123b below the radar measuring device 10. The upper radar measurement diagram 123a shows a proper measurement with partial reflection peaks P-t1, P-t2, P-t3, and P-t4 at the outer surface 5b and inner surface 5c of the pipe, as well as a total reflection peak TP at the reflector 49. From the distance between the partial reflection peaks P-t1, P-t2, P-t3, and P-t4, the geometric properties such as wall thickness d, outer diameter Da, and inner diameter Di can be fully determined, especially if the speed of light c in the material of the pipe wall 5a is known, whereby a calibration measurement can be performed without the pipe 5. Thus, the radar measuring device 10b can also detect an irregularity such as the one shown in Figure 5. Fig. 2 shown eccentricity 22 or irregularities in the wall thickness d can be detected.

[0056] The lower radar measurement diagram 123b shows a measurement in which the marker 20 on the outer surface 5b of the front wall area is detected. The metallic marker 20 reflects the radar radiation 138, so that instead of the first partial reflection peak P-t1, a total reflection peak is detected, without further partial reflection peaks P-t2, P-t3, P-t4 and the rear total reflection peak TP occurring. In other cases, the marker 20 may reflect the radar radiation 138 laterally without the partial reflection peaks P-t1, P-t2, P-t3 and P-t4 and the total reflection peak TP occurring. Thus, the marker 20 can be clearly detected.

[0057] Fig. Figure 6 schematically shows a further embodiment of an ultrasonic measuring device 10c with several ultrasonic transducers 55 positioned circumferentially around the pipe 5. Each of the ultrasonic transducers 55 emits ultrasonic waves 58, which reach the pipe 5 through, for example, water as a coupling medium, so that reflections at interfaces can be detected accordingly, in accordance with the radar measuring device 10b. Fig. 6. For this purpose, see in Fig. 6 in turn, accordingly Fig. Figure 5, shown above, is a measurement of the signal strength S of a properly functioning pipe 5, with a first peak P-t1 at time t1 when the sound waves enter the outer wall 5b and a subsequent second peak P-t2 at time t2 when the sound waves strike the inner wall 5c of the pipe 5. In the lower measurement diagram, the ultrasonic transducer 55 detects the mark 20 on the outer surface 5b, so that only a strong reflection occurs at time t1.

[0058] According to Fig. Thus, the respective measuring device 10 outputs a measuring signal S1 to the control unit 16. The first circumferential position P1 at the first longitudinal position A18, where the mark 20 was set, is stored in the control unit 16, or the central control unit 16 itself has controlled the marking device 18 for this purpose by means of the marking signal S4. Therefore, the control unit 16 can, according to Fig. 2. Determine the rotation angle alpha and display it on the display device 17. This allows a user to adjust the setting device 15 of the extrusion tool 4 accordingly.

[0059] Furthermore, according to an advantageous embodiment, the control device 16 can also itself control the adjusting device 15 on the extrusion tool 4 by means of the adjusting signal S2, such that the appropriate adjustment is made. For this purpose, the control device 16 evaluates the measuring signals S1 and determines, for example, the position or angular position and extent of the eccentricity 22, or the control device 16 creates an ideal pipe pattern and compares it with the determined pipe pattern according to Fig. 2, to determine the setting values ​​of the setting device 15.

[0060] Furthermore, the control unit 16 can determine the pipe travel time T-5 and thus the conveying speed v from the time difference between the application of the mark 20, particularly when the marking device 18 is activated via the marking signal S4 or by user input, and the measurement time of the mark 20 on the pipe 5 in the measuring device 10, i.e., in particular as the quotient of the distance B between A10 and A18 and the pipe travel time T-5. Knowing the conveying speed v is advantageous for controlling the discharge 12, since the wall thickness d can be adjusted by the conveying speed v.

[0061] Thus, according to the invention, a conventional measurement of the pipe 5 can be carried out in the extrusion section 1 with regard to geometric properties such as wall thickness d, outer diameter Da and inner diameter Di, as well as errors and irregularities, and furthermore, a determination of the rotation angle α and a compensation of irregularities as well as a determination of the conveying speed v and adjustment of the take-off 12 can be combined.

[0062] According to the flowchart of Fig.The following steps are therefore provided: After the start in step St0, extrusion takes place in step St1, in which the bulk material 14 is melted and discharged by the extruder 2 through the extrusion die 4 as the initial pipe 5. Subsequently, in step St2, the mark 20 is applied to the pipe 5, then in step St3, calibration and cooling take place in the calibration device 6. In step St4, the measurement is carried out by the measuring device 10, and subsequently, in step St5, pipe properties are determined from the respective measurement diagrams, in particular the inner diameter Di, the outer diameter Da, the wall thickness d of the pipe wall 5a, as well as the identification of the mark 20. Thus, according to step St5, pipe properties are determined, as well as the rotation angle α of the pipe 5 and the conveying speed v.Subsequently, according to an advantageous embodiment in step St6, the adjusting device 15 7 can be controlled via the control signal S2 to compensate for the measured eccentricities 22 or irregularities on the calibration sleeve 7. Furthermore, the trigger 12 can also be controlled accordingly to adjust the wall thickness d by fine-tuning. Reference symbol list 1 extrusion line 2 extruders 2a Feed hopper 2b Extruder screw 4 Extrusion tool 5 pipe 5a Pipe wall 5b Outer surface of the pipe wall 5c Inner surface of the pipe wall 6 Calibration and cooling unit 7 Calibration sleeve 8 Vacuum chamber 10 Measuring device 10a X-ray measuring device 10b Radar measuring device 10c Ultrasonic measuring device 12 deduction 14 Bulk goods 15 Adjustment device 115 adjusting screws of the adjusting device 16 central control unit 17 Display device 18 Marking device 20 Mark 21-1 Interior at the first longitudinal position A18 21-2 Interior at the second longitudinal position A10 22 Eccentricity 23 Overall measurement diagram 23a, 23b, 23c X-ray measurement diagrams 34, 34a, 34b, 34c X-ray measurement axes 35 X-ray source 36 X-ray detector 38 X-rays 40-1 Baseline 40-2 flank area 40-3 minimum value 40-4 medium signal range 45 radar transceivers 49 Reflector 55 Ultrasound transceivers or ultrasound converters 58 ultrasound waves 120a first shielding peak 120b second shielding peak 120c third shielding peak 123a. b Radar measurement diagrams 138 Radar radiation A pipe axis A18 first longitudinal position (first track position) A10 second longitudinal position (second track position) alpha rotation angle d wall thickness Since outer diameter The inner diameter F Conveyor direction P1 first circumferential position of the marking 20 P2 second circumferential position of the marking 20 I Intensity S Signal strength P-t1, P-t2, P-t3, P-t4 partial reflection peaks t1, t2, t3, t4 Measurement times S1 Measurement signal of the measuring device 10 S2 setting signal S2 to the extrusion tool 4 S3 control signal to the trigger 12 S4 marking signal S5 switching signal TP Total Reflection Peak T-5 pipe runtime v Conveyor speed

Claims

Method for determining the position of an extruded tube (5) in an extruder section (1), comprising the following steps: - Applying a mark (20) in or on a tube wall (5a) of a tube (5) after the tube (5) has been ejected from an extrusion die (4) and before the tube (5) has been fed to a calibration device (6) (ST2), wherein the mark (20) is applied at a first circumferential position (P1) of the tube (5) by means of a marking device (18), - after the tube (5) has passed through the calibration device (6), measuring the tube (5) by a measuring device (10) by detecting the mark (20) and outputting a measurement signal (S1) (ST4), - detecting the mark (20) in the measurement signal (S1) and determining a second circumferential position (P2) of the mark (20) on or in the tube wall (5a), - comparing the first circumferential position (P1) with the second circumferential position (P2) and determination of a rotation angle (α) between the circumferential positions (P1, P2). Method according to claim 1, characterized in that the determined rotation angle (α) is displayed in a display device (17), together with one or more of the following features: - one or more determined geometric pipe properties of the pipe (5) - a determined irregularity (22), e.g. eccentricity (22) of the pipe (5), - the first circumferential position (P1) and the second circumferential position (P2). Method according to claim 2, characterized in that the pipe (5) is displayed on the display device (17) with the features of the pipe (5) determined by the measuring device (10) under compensation of the determined rotation angle (alpha). Method according to one of the preceding claims, characterized in that the marking (20) is applied: - to an outer surface (5b) of the tube (5), e.g. by gluing or by applying a material, e.g. a liquid or a viscous material. Method according to one of the preceding claims, characterized in that the marking (20) is applied: - in the pipe wall (5a), e.g. by piercing or forming a slot. Method according to one of the preceding claims, characterized in that the marking (20) is applied: - to an inner surface (5c) of the tube (5), e.g. by means of a mandrel of the extrusion tool (4). Method according to one of the preceding claims, characterized in that one or more of the following materials are applied as a marker (20): - a material that is absorbing and / or reflecting for the measuring method of the measuring device (10), in particular absorbing and / or reflecting for X-rays and / or radar radiation and / or ultrasound waves, - a metal-containing material, e.g. with an X-ray-blocking metal such as bismuth, tungsten, barium or silver, - conductive silver, conductive paste, - a metal powder absorbed in a vaporizable solvent or a resin, - a solid metal body, e.g. metal sphere, preferably together with a dispersing aid and / or with color pigments such as carbon black, iron oxide or titanium dioxide. Method according to one of the preceding claims, characterized in that the measuring device (10) determines one or more of the following pipe properties: at least an outer diameter (Da), at least an inner diameter (Di), at least a wall thickness (d), in particular at several circumferential positions of the pipe (5) and / or completely along the circumference of the pipe (5), an eccentricity (22), ovality, inclusions or defects, a refractive index (n) of the material of the pipe (5), wherein the measuring device (10) is provided in particular between the calibration device (6) and a puller (12) for pulling off the pipe (5). Method according to one of the preceding claims, characterized in that a marking time (T5-18) of the application of the marking (20) to the pipe (5) is determined or stored, and a detection time (T5-10) of the detection of the marking (20) by the measuring device (10) is determined, wherein a conveying speed (v) is determined from the marking time (T5-18), the detection time (T5-10) and a distance (B) between the marking point and the measuring device (10). Method according to one of the preceding claims, characterized in that the following are adjustable: - a measuring mode (M1) for measuring the pipe (5) for pipe properties, in particular for regular measurement during the extrusion process, and - a detection and alignment mode (M2) for applying the marking (20) and / or determining the marking (20) in the measuring signal (S1) and determining the rotation angle (alpha), wherein in particular a switching signal (S5) can be inputted for switching between the measuring mode (M1) and the detection and alignment mode (M2). Method according to one of the preceding claims, characterized in that the measurement is carried out using one or more of the following measuring methods: an X-ray measuring method, a radar measuring method, an ultrasonic measuring method. Method for extruding a tube (5) in which bulk material (14) is fed into an extruder (2) and a tube (5) made of a molten material, e.g. a plastic material or rubber, is extruded and discharged, the tube (5) discharged from the extrusion tool (4) is marked and measured by a method according to one of the preceding claims by determining a rotation angle (alpha) of the tube (5), wherein the tube (5) is calibrated in a calibration device (6) after the marking step (ST2). Method according to claim 12, characterized in that, depending on the determined rotation angle (α), an adjusting device (15), in particular an extrusion tool (4) of the extruder (2), is adjusted with setting values. Method according to claim 13, characterized in that the adjusting device (15) is adjusted for one or more of the following changes: - a compensation of a determined irregularity (22) of the pipe (5), e.g. an eccentricity (22), - an adjustment of a geometric property of the pipe wall (5a), e.g. a wall thickness (d), an outside diameter (Da) and / or an inside diameter (Di). Method according to one of claims 12 to 14, characterized in that a control device (16) automatically determines the setting values ​​from the measurement signals (S1) of the measuring device (10) and automatically controls the setting device (15), in particular as a closed control loop, especially for compensating a detected irregularity (22). Method according to one of claims 12 to 15, characterized in that, in addition to the rotation angle (alpha), a conveying speed (v) of the tube (5) in the extrusion section (1) is determined and, depending on the determined conveying speed (v), a take-off (12) for taking off the tube (5) in the extrusion section (1) is controlled to regulate the conveying speed (v) and / or the wall thickness (d). Computer program comprising computer-readable instructions for performing a method according to any of the preceding claims. Extrusion line (1) for extruding tubes (5), comprising: - an extruder (2) for receiving a bulk material (14) and dispensing an extruded tube (5), - a calibration device (6) for calibrating the dispensed tube (5), - an adjustment device (15) for adjusting an extrusion die (4) of the extruder (2), - a measuring device (10) for measuring the tube (5) and outputting a measurement signal (S1), wherein the measuring device (10) is provided in the conveying direction downstream of the calibration device (6) and is configured to measure a tube property (Da, Di, d), - a pull-off device (12) for dispensing the tube (5) from the calibration device (6) and the measuring device (10), and - a control device (16) for receiving measurement signals (S1) from the measuring device (10), characterized in that a marking device is provided between the extruder (2) and the calibration device (6). (18) is provided for, who is trained,to form or attach a marking (20) in a first circumferential position (P1) in or on the tube (5), wherein the control device (16) is configured to determine a second circumferential position (P2) of the marking (20) in the measuring device (10) from the measuring signal (S1) of the measuring device (10), and wherein the control device (16) is configured to determine a rotation angle (α) of the tube (5) from the first circumferential position (P1) and the second circumferential position (P2). Extrusion section (1) according to claim 18, characterized in that it has a display device (17) and the control device (16) is configured to display the rotation angle (α) and / or the first and second circumferential position (P1, P2) in the display device (17), in particular together with determined pipe properties and / or irregularities (22) of the pipe (5). Extrusion line (1) according to claim 18 or 19, characterized in that the control device (16) is configured to perform one or more of the following steps: - Controlling the adjustment device (15) with control signals (S2) to compensate for a detected irregularity (22), e.g. ovality, and / or to change a pipe property (d, Da, Di) of the pipe (5), - Determining a pipe property (Da, Di, d) and / or an irregularity (22) of the pipe (5) from the measurement signal (S1), - Controlling the adjustment device (15) to compensate for an irregularity or to change a pipe property, in particular as a closed control loop. Extrusion section (1) according to one of claims 18 to 20, characterized in that the adjusting device (15) has one or more adjusting means, e.g. adjusting screws (115), provided circumferentially around the tube (5) or a longitudinal axis (A) of the tube (5), which are preferably adjustable in a direction perpendicular to the tube axis (A). Extrusion section (1) according to one of claims 18 to 21, characterized in that the measuring device (10) is designed as one or more of the following devices: - an X-ray measuring device (10a), in particular with at least two, preferably three angularly offset X-ray measuring axes (34a, 34b, 34c), each with an X-ray source (35) and an X-ray detector (36), for receiving the tube (5) in a measuring chamber between the X-ray source (35) and the X-ray detector (36), - a radar measuring device (10b), in particular with several radar measuring axes, each with a radar transceiver (45) for emitting radar radiation (138) and receiving reflected radar radiation (138), - an ultrasonic measuring device (10c) with several ultrasonic transducers (55) for emitting and receiving ultrasonic waves (58).

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