Method and device for producing tubes, wires, profiles and similar elongate material by means of a drawing device

Abstract

The invention relates to a method for producing tubes, wires, profiles and similar elongate material by means of a drawing device (1), in which, during the drawing process, vibration emissions at a material strand and / or at the drawing device (1) are detected and evaluated in order to identify faults such as grooving and chatter marks, the vibration emissions being subjected continuously to a spectral analysis in such a way that the presence or absence of emissions that are increasing and decreasing over time and / or of pulse-like emissions is identified, and the drawing speed is altered in response thereto.

Description

[0001] Method and device for producing pipes, wires, profiles and similar long material by means of a drawing device

[0002] Field of the invention

[0003] The invention relates to a method and a device for producing pipes, wires, profiles and similar long material according to the preamble of claim 1 and 6 respectively.

[0004] Background of the invention

[0005] One manufacturing process for the production of tubes, wires, profiles, and similar long materials is drawing. In this form of tensile-compression forming, a strand of material, usually made of metal, is drawn through a drawing die. The material strand thus takes on the shape of the opening of the drawing die on the outside and is generally longer and thinner. If the material strand is a hollow body such as a tube, a mandrel can interact with the drawing die to form a gap, particularly an annular gap. Depending on the material, tool, wear, lubricant, and process parameters, a so-called chattering can occur during drawing. Resonant vibrations occur and lead to damage in the form of chatter marks on the material strand or to the strand itself being torn off.

[0006] In order to detect and avoid chattering during pipe drawing, it is known, for example from EP 0 780 171 A1, to detect vibrations of the drawing system pipe-dome-drawing machine by means of structure-borne sound sensors and to monitor the vibration amplitude for exceeding a limit value or by means of a fuzzy logic system in order to reduce the drawing speed in order to avoid chattering.

[0007] The disadvantage here is that high amplitudes not caused by chatter can lead to a misguided reduction in the drawing speed. Furthermore, chatter can only be reliably detected once it has already occurred. As a result, the known method only achieves a suboptimal material throughput.

[0008] Other defects in pipe drawing, especially drawing marks, cannot be detected using the known method.

[0009] The same problem arises when pulling through wires, profiles and the like.

[0010] Summary of the invention

[0011] Based on this, the invention is based on the object of creating a method and a device for producing pipes, wires, profiles, and similar long materials according to the preamble of claims 1 and 6, respectively, with which defects such as chatter and drawing marks can be reliably eliminated while ensuring a high material throughput. This object is achieved according to the features of claims 1 and 6, respectively.

[0012] Accordingly, a method is created for drawing pipes, wires, profiles and similar material strands by means of a drawing device, in which vibration emissions are recorded and evaluated during the drawing process on the material strand and / or on the drawing device in order to detect defects such as drawing marks and chatter marks, wherein the vibration emissions are continuously subjected to a spectral analysis in such a way that the occurrence or absence of, in particular, frequency-selective emissions which increase and decrease over time and / or in particular frequency-selective, pulse-like emissions is detected, and that the drawing speed is changed in response thereto.

[0013] Spectral analysis allows the detection of signal patterns that signal the onset of chatter several hundred milliseconds in advance. Chatter can be prevented more reliably than with prior art analysis based on vibration amplitude. The same applies to broadband, pulse-like emissions typical of drawing marks. These, too, can be detected using the spectral analysis according to the invention before they become too energy-intensive and leave traces on the material strand.

[0014] The drawing speed is conveniently reduced if such emissions are detected by spectral analysis, and can be increased if they are absent. Adaptive control of the drawing speed based on this ensures that the highest possible drawing speed is always used.

[0015] The evaluation can be carried out on the basis of the multidimensional pattern recognition developed by the applicant, as known, for example, from EP 2 359 106 A2, which is hereby incorporated in its entirety by reference.

[0016] It is particularly advantageous to divide vibration emissions into low- and high-emission frequency ranges and to perform detection in the low-emission range. This can be based on an amplitude threshold in the spectrum or the vibration intensity, e.g., as a percentage of the maximum over time. The amplitude threshold for a low emission can be, for example, 1%, 2%, 3%, 5%, 7%, 10%, 15%, 20%, 25%, 30%, 35% and the time course considered can be 0.1s, 0.2s, 0.3s, 0.4s, 0.5s, 1s, 2s, 3s, 5s, 7s, 10s, 15s, 20s, 25s, 30s, 50s, 1min, 2min, 3min, 5min, 10min or variably coupled to the variation of the vibration intensity in such a way that with increasing variation of the vibration emissions the threshold increases and with decreasing variation of the vibration emissions the threshold decreases.

[0017] The invention further provides a drawing device for drawing pipes, wires, profiles and similar material strands according to the method according to the invention, with a sensor for detecting vibrations that arise during drawing on the material strand and / or on the drawing device, and an evaluation device coupled to the sensor for evaluating the detected vibrations for the purpose of detecting defects such as drawing marks and chatter marks, wherein the evaluation device is designed to continuously subject vibration emissions to a spectral analysis in such a way that the occurrence or absence of emissions that rise and fall over time and / or pulse-like emissions is detected, and is designed to control or regulate the drawing speed in response to the detection.

[0018] Further features and embodiments of the invention will become apparent from the following description with reference to the accompanying drawings.

[0019] Character description

[0020] Fig. 1A illustrates a pipe pulling device in longitudinal section.

[0021] Fig. 1B is a perspective view of a portion of a pipe pulling device. Fig. 1C illustrates a pipe pulling device with a fixed mandrel in longitudinal section.

[0022] Fig. 1D illustrates a pipe pulling device with a moving rod in longitudinal section.

[0023] Fig. 1E illustrates a pipe pulling device with a flying mandrel in longitudinal section.

[0024] Fig. 2A illustrates the vibration spectrum of an almost complete tube drawing process.

[0025] Fig. 2B shows a section of Fig. 2A.

[0026] Fig. 2C illustrates the vibration spectrum during normal, chatter-free operation.

[0027] Fig. 2D is a section of Fig. 2A immediately before chattering begins.

[0028] Fig. 2E shows individual vibration patterns from Fig. 2D.

[0029] Fig. 2F shows an oscillation from Fig. 2E.

[0030] Fig. 3 illustrates the spectrum for an adaptive control of the pulling speed.

[0031] Fig. 4 illustrates cumulative chatter pulses.

[0032] Description of the embodiments

[0033] The drawing device 1 for drawing pipes, for example, schematically illustrated in Fig. 1A, comprises a drawing trough 2, through which a pipe 3 is drawn in the direction of arrow 4 to reduce the outer diameter and pipe thickness, as well as a sensor 5 for detecting vibration emissions, which is arranged here, for example, on the drawing trough 2 and coupled to an evaluation device 6, e.g., a computer. The drawing trough 2 shown as an example has an opening 7, which is designed rotationally symmetrically about the central axis 8 and tapers from an inlet diameter to an effective diameter. As it is pulled through the drawing trough 2, the pipe 3 undergoes tensile compression deformation to a desired target diameter. When dimensioning the effective diameter, it must be taken into account that the pipe 3 can spring back on the outlet side of the taper depending on the degree of springback of the material and can thus become larger than the effective diameter of the drawing trough 2.For practical purposes, the diameter of the pull-hole 2 widens again slightly on the output side.

[0034] The pulling device 1 can have several pulling holes 2, see Fig. 1B. Three pulling holes 2a, 2b, 2c are illustrated by way of example, through which pipes can be pulled simultaneously. A sensor 5a, illustrated here with a cable stub, is assigned to at least one pulling hole 2a. Conveniently, each pulling hole 2a, 2b, 2c is assigned a sensor 5a, 5b, 5c. Preferably, the sensor 5 is coupled to the pulling hole 2 or to an element firmly connected thereto.

[0035] The tube 3 can also be supported from the inside by an internal tool, which is suitable for coupling the sensor 5 in addition to the drawing rod 2 or instead of the drawing rod 2. For example, a mandrel 9 can be provided which is attached to a dome rod 10, see Fig. 1C. During the drawing process, the tube 2 is then drawn through an annular gap formed between the drawing rod 2 and the mandrel 9 and takes on the size of the drawing rod 2 in its outer diameter and the size of the mandrel 9 in its inner diameter, plus any springback. In this case, the sensor 5 can be coupled to the dome rod 10. The same applies when using a rotating rod 11, see Fig. 1D, which is pushed through the tube instead of the dome 7 and is gripped by a drawing tool via a cylindrical head extension 12 which extends through the pointed end 13 of the tube 2. The sensor 5 can be coupled to the moving rod 11.However, if a floating internal tool is provided, e.g. the floating mandrel 9 in Fig. 1E, this is not suitable for coupling the sensor 5. The sensor 5 is then coupled to the draw bar 2 or an element firmly connected thereto.

[0036] Although Fig. 1 illustrates a wire drawing device for the purpose of illustration, according to the invention the drawing device 1 is suitable for drawing pipes, wire, profiles or other material strands and can have further components for this purpose, such as an internal tool or a drawing device.

[0037] Sensor 2 is preferably a structure-borne sound sensor, e.g., a piezo sensor. Other types of sensors can also be used, as long as they can detect vibrations in the frequency range of interest.

[0038] The sensor 2 is coupled to the draw tube 2, the tube 3, an internal tool, or to a part vibration-coupled to the draw tube 2, the tube 3, and / or the internal tool in such a way that it can detect vibrations of the tube 3 and / or the draw tube 2 and / or the internal tool. In the simplest case, the sensor is screwed in place.

[0039] During the drawing process, vibrations arise on the tube 3 and on the drawing device 1, in particular on the outer tool drawing tube 2 or on the inner tool, which are picked up by the sensor 5. For this purpose, the sensor 5 is designed such that it can detect frequencies between a lower limit and an upper limit. Ideally, the lower limit is 0 and the upper limit is ∞, so that the entire spectrum of interest can be recorded. In practice, an upper limit of at least 50 MHz, preferably at least 100 MHz, is appropriate. Frequencies below 90 kHz or 40 kHz are preferably attenuated or cut off in practice because they contain no usable information, so an appropriate lower limit is appropriate, but can also be 50 kHz, 100 kHz, 500 kHz or 1 MHz. The actual frequency range of the sensor 5 should be selected based on the material to be drawn and the drawing speed.The frequency range between approximately 180 kHz and 400 kHz has proven to be particularly informative.

[0040] According to the invention, the vibrations detected by sensor 5 during the machining of workpiece 3 are subjected to a spectral analysis, e.g., in the form of a frequency-time analysis. For this purpose, the detected vibration spectrum can be temporarily stored in the evaluation device 6, which is preferably a computer with a corresponding interface and suitable storage media.

[0041] In the evaluation device 6, the frequency-time analysis can be carried out in such a way that the vibration spectrum is displayed graphically and / or analyzed numerically during or after the recording.

[0042] The evaluation can be carried out three-dimensionally with the coordinates time, frequency and amplitude (or maximum amplitude or intensity or the like) as illustrated in Fig. 2.

[0043] Fig. 2A shows the vibration spectrum of an almost complete pipe pulling process. A broadband, high-intensity chatter signal section with a limited duration, extending across almost the entire recorded frequency range, is visible, beginning at approximately second 7.

[0044] The chatter is announced by broadband up- and down-wave emissions a few hundred milliseconds in advance, see Fig. 2B. Successive emission lines show increasing intensity. They can be identified by pattern recognition and differ significantly from the emissions during normal, chatter-free operation, see Fig. 2C. Fig. 2D is a section of Fig. 2A immediately before the chatter onset, showing periodic up-waves. Individual oscillation patterns are shown in Fig. 2E. One oscillation is shown in Fig. 2F.

[0045] If the pull speed is reduced in response to the detection of such rising and falling emissions, the emission lines disappear and chatter can be avoided, see Fig. 3.

[0046] If no broadband rising and falling emission is detected over a longer period of time, the pulling speed can be increased according to the invention within the framework of any further operating parameters until such emission lines become apparent.

[0047] A possible control loop can be based on cumulative chatter pulses, see Fig. 4.

[0048] The upper curve 14 in Fig. 4 begins at (0,0) and reaches a function value of 29 at reference number 15. It describes cumulative chatter pulses in the frequency range of 200 kHz to 400 kHz, as used here as an example. Each detection of a chatter pulse increases the value by 1.

[0049] In the temporal direction, a gradient analysis of the signal emission in this frequency range is performed. Thus, the cumulative value is reset. If, after the initial occurrence of the periodic emissions that indicate chatter, these periodic emissions cease for a predetermined period, the cumulative value is reset to 0 or by a reset value, e.g., -5.

[0050] If certain threshold values ​​are exceeded, signals can be sent to the machine with which, for example, the speed is adjusted, in particular reduced. If the emissions that indicate rattling then cease, the cumulative value can be reduced or reset as described above and the machine can accelerate. This is illustrated by the lower curve 16 in Fig. 4 with an example of three-stage speed control, which in other embodiments can also be four, five or more than five stages or (quasi-)continuous. The value -3 here denotes the normal speed, the value -2, to which reference numeral 17 is controlled, a speed reduction of 25%, and the value -1, to which reference numeral 18 is controlled, a speed reduction of -50%. At reference numeral 19, the speed can be controlled back to the normal value because no rattling has been detected over a predetermined period of time.The thresholds assigned to the reduction of 25% and 50%, as examples, at reference numbers 17 and 18 (and subsequent regulatory points), respectively, are illustrated by the horizontal lines 20 and 21, respectively; the reduction can be implemented in more than two stages and / or (quasi-)continuously.

[0051] The invention thus provides an adaptive control of the drawing speed, which remains close to the maximum even when the operating parameters (tool wear, lubricant variation, temperature change, etc.) change.

Claims

Claims 1. Method for producing tubes, wires, profiles and the like long material by means of a drawing device (1), in which vibration emissions are detected and evaluated during the drawing process on a strand of material and / or on the drawing device (1) in order to detect defects such as drawing marks and chatter marks, characterized in that the vibration emissions are continuously subjected to a spectral analysis in such a way that the occurrence or absence of rising and falling emissions and / or impulsive emissions over time is detected, and that the drawing speed is changed in response thereto.

2. Method according to claim 1, characterized in that the drawing speed is reduced when the occurrence of the emissions is detected.

3. Method according to claim 1 or 2, characterized in that the drawing speed is increased when the absence of emissions is detected.

4. Method according to one of claims 1 to 3, characterized in that the drawing speed is adaptively controlled.

5. Method according to one of claims 1 to 4, characterized in that the vibration emissions are divided into frequency ranges of low and high emission and the detection takes place in the range of low emissions.

6. Drawing device (1) for drawing tubes (3), wires, profiles and similar strands of material, comprising a sensor (5) for detecting vibrations that occur during drawing on the strand of material and / or on the drawing device (1), and an evaluation device (6) coupled to the sensor (5) for evaluating the detected vibrations in order to detect defects such as drawing marks and chatter marks, characterized in that the evaluation device (6) is designed to continuously subject vibration emissions to a spectral analysis in such a way that the occurrence or absence of fluctuating emissions and / or impulsive emissions over time is detected, and is designed to control or regulate the drawing speed in response to the detection.

7. Drawing device according to claim 6, characterized in that the sensor is coupled to an external tool.

8. Drawing device according to claim 6, characterized in that the sensor is coupled to an internal tool.

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