EP0041970A1 - Procede et appareil de soudage a l'arc - Google Patents

Procede et appareil de soudage a l'arc

Info

Publication number
EP0041970A1
EP0041970A1 EP80902358A EP80902358A EP0041970A1 EP 0041970 A1 EP0041970 A1 EP 0041970A1 EP 80902358 A EP80902358 A EP 80902358A EP 80902358 A EP80902358 A EP 80902358A EP 0041970 A1 EP0041970 A1 EP 0041970A1
Authority
EP
European Patent Office
Prior art keywords
welding
weaving
electrode
sound
arc
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP80902358A
Other languages
German (de)
English (en)
Inventor
Ole Molaug
Kjell Olavus Kverneland
Dag G. Kjosavik
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
TRALLFA NILS UNDERHAUG AS
Original Assignee
TRALLFA NILS UNDERHAUG AS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by TRALLFA NILS UNDERHAUG AS filed Critical TRALLFA NILS UNDERHAUG AS
Publication of EP0041970A1 publication Critical patent/EP0041970A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K9/00—Arc welding or cutting
    • B23K9/095—Monitoring or automatic control of welding parameters
    • B23K9/0956—Monitoring or automatic control of welding parameters using sensing means, e.g. optical
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K9/00—Arc welding or cutting
    • B23K9/12—Automatic feeding or moving of electrodes or work for spot or seam welding or cutting
    • B23K9/127—Means for tracking lines during arc welding or cutting

Definitions

  • the present invention is based on acoustic detection rather than the conventional optical technique which usually is employed in this field.
  • the welding arc must necessarily emit sound, and this may according to the invention be achieved in two ways.
  • the sound emitted from the welding arc and picked up by the microphone is produced by setting the arc current and voltage at such values that the materi ⁇ al transfer from the welding electrode to the workpiece takes place drop by drop, thus producing a short noise pulse at each drop * transfer.
  • the required acoustic power is, however, supplied from outside to the arc. as the sound emitted from the welding arc and picked up by the microphone is produced by superimposing an A.C. signal of a given fre ⁇ quency on the welding current .
  • the detected variations of the sound which is picked up by the microphone may of course be utilised for various pur ⁇ poses, e.g. the mapping of an arc movement pattern, statist ⁇ ics, metalurgical investigations, etc, but according to the invention the sound variations are preferably utilised for producing a control signal for controlling the movement of the welding electrode.
  • the present invention relates to a method in arc welding with movable electrode for detecting the movement of the welding arc with respect to a given location, and an apparatus for performing this method.
  • automatic arc welding means In automatic arc welding means must be provided for detecting the movement of the arc with respect to the welding area and furnishing a control device with the necessary information for the intended guidance of the welding electrode. It is previously and generally known to use photoelectrical devices, such as arrays of photo cells or a television camera for this purpose. Such engagement is, however, often expensive and complex, and the derived visual information often requires extensive data processing to be useful for the control of the weld electrode.
  • the invention concerns a method in arc welding with movable electrode for detecting the movement of the weldi arc with respect to a given location, including the gener inventive feature that a microphone is placed at the give location and adapted to pick up sound emitted from the welding arc, variations of the picked up sound being dete ed as a representation of the movement of said arc with respect to the microphone.
  • a control signal is formed corresponding to the detected sound variations during each complete weaving period, and a possible unsymmetry of this signal with respect to the weaving motion is registered as representing an un- symmetric weaving of the electrode with respect to the welding joint and utilised for such control of the elec ⁇ trode movement that the registered unsymmetry is abolished.
  • the invention also includes apparatus for performing the methods indicated above and comprising according to the invention a microphone disposed st the given location and operative to pick up sound emitted from the welding arc, detection means being connected with the microphone and operatively adapted for detecting variations of the picked up sound as a representation of the movement of the arc with respect to the microphone.
  • the detection means may be adapted to form a control signal on the basis of detected variations of frequentness or mean value of emitted noise pulses in the course of each complete weaving period.
  • control signals for both the electrode guid ⁇ ance along the welding joint and the electrode height level above the joint may be formed on the basis of arranged short circuit intervals on each side of the welding joint.
  • the detection means of the apparatus When superimposing an A.C. signal on the welding current the detection means of the apparatus according to the invention is preferably adapted to detect the phase difference between the A.C. signal superimposed on the welding current and the corresponding sound picked up by the microphone during the weaving of the electrode across the welding joint, and to produce a control signal in accordance with the variation of this phase difference in the course of a complete weaving period.
  • Figure 1 illustrates schematically the fundamental operative principle of the present invention.
  • Figures 2 and 3 are recorder diagrams showing electrode weaving,detected arc noise and welding current
  • Figure 4 shows in principle a circuit for integration of superimposed arc noise and electrode weaving
  • Figures 5 and 6 are recorder diagrams of the same type as shown in Figures 2 and 3, but also showing integrated noise signals,
  • Figure 7 illustrates schematically the principle of super ⁇ imposing an A.C. signal on the welding current and picking up the corresponding sound from the welding arc by a microphone
  • Figure 8 shows a block diagram of equipment for measuring the distance between a microphone and a sound emitting welding arc
  • Figure 9 is a recorder diagram showing detected variations of the distance between welding arc and microphone during a manually performed welding operation.
  • Fig. 1 The fundamental working principle of the present invention is schematically illustrated in Fig. 1.
  • This figure shows the nozzle U of a welding gun with an electrode E in two different working positions with respect to a welding joint F.
  • a microphone M is mounted in the nozzle to pick up sound emitted from the welding arc B of the electrode E, the variations of the picked up sounds being detected as representing the movement of the arc with respect to the microphone.
  • the emitted sound from the welding arc B may either be self-generated welding noise or a sound signal provided by superimposing an A.C. signal on the welding current.
  • the welding arc is shown at one edge of the welding joint F and in the center of the joint, respectively.
  • the present method according to the invention is particularly well suited for automatically guiding a welding electrode along a welding joint, while the electrode at the same time is weaving back and forth across the joint.
  • the welding noise is most intense when the arc welding is performed with moderate values of welding current and vol ⁇ tage (short arc welding) , as the material transfer through the welding arc in this case takes place in the form of discrete drops. Then a strong noise pulse is emitted for each drop transfer', and these pulses are picked up by the microphone and detected as electrical intensity pulses after rectifying the signal. On the basis of the received noise pulses a control signal is then formed corresponding to the detected sound level variations in the course of each complete weaving period. A possible unsymmetry of this signal with respect to the weaving motion is then registered as representing an unsymmetric weaving of the electrode across the joint, and then utilised for controlling the movement of the electrode in such a way that the regist ⁇ ered unsymmetry is abolished.
  • control signal e.g. the frequentness or mean value of the formed noise pulses may be detected in the course of the weaving of the electrode across the welding joint, and the variation of this detected value during each complete weaving period is utilised as the required control signal.
  • Fig. 2 illustrates the conditions with symmetric weaving of the welding electrode across the joint. The cessations of the noise signals are then situated symmetrically with respect to the weaving patt- * ern..
  • Fig. 3.the prevailing conditions are shown in the case the weaving of the electrode is laterally displaced to the right-hand side of the welding joint, and it will appear from the diagrams of this figure that the cessations of the noise signals are clearly displaced towards the right-hand side of the weaving pattern.
  • a further improvement of the procedure according to the invention for utilisation of the self-generated noise of the electrode for the formation of a control signal to be applied for correctly guiding the movement of the welding electrode may be achieved by superimposing the weaving pattern on the noise signal received through the microphone after suitable rectification and smoothing of the latter signal, and subsequently integrating the resulting signal.
  • a circuit for performing such signal processing steps is shown in Fig. 4.
  • the rectified and smoothed noise signal is supplied to an electronic phase-reversal switch
  • the output signal of this amplifier is thus constituted by the noise signal with superimposed weaving pattern.
  • This output signal is integrated in an integrator I, which in Figure 4 is shown to consist of a resistor R and a condenser Cl'.
  • the signal emitted from the integrator I is a triangular wave form, which is displaced to one side or the other with laterally displaced weaving.
  • Figs. 5 and 6 which in addition to the plotted weaving signal also show both the rectified and smoothed noise signal and the integration signal produced by the integrator I.
  • Fig. 5 the plotted diagrams illustrate the case when the weaving motion of the welding electrode is symmetric with respect to the welding joint
  • Fig. 6 shows the corresponding diagrams when the weaving motion is laterally, displaced to the left with respect to the joint.
  • the indicated displacement of the integration signal in the latter case may be utilised as a suitable control signal for guiding the weaving electrode correctly along the welding joint.
  • the material transfer from the welding wire to the workpiece takes place in the form of an approximately continuous flow, and then no discrete noise pulses will be emitted from the welding arc, as in the previous case with material transfer drop by drop.
  • the welding arc is much less noisy than in short arc welding, as described above.
  • Fig. 7 is schematically indicated that current from a welding machine A, having a transformer T and a rectifier __, is supplied to a welding gun and producing an electric arc B between the electrode E of the welding gun and a workpiece K. It is also schematically shown that a microphone M is mounted in connection with the welding gun, e.g. as shown in Fig. 1. According to the invention an A.C. signal is supplied from a signal generator G through a condenser C2 to the conductor carrying the welding current, and this signal is then super-
  • the frequency of the A.C. signal is in practice selected so high, that the internal inductance of the welding machine effectively blocks a propagation of such signal into the machine A.
  • welding arcs When supplied with such an A.C. signal of suitable frequency and amplitude, welding arcs have proved to be able to emit sounds corresponding to the supplied signal and capable of being picked up by the microphone M.
  • the sound signal picked up by the micorphone is de ⁇ livered in the form of a corresponding electric signal to a phase detector D, which also receives the A.C. Signal pro ⁇ pokerd by the signal generator G.
  • the phase detector D is opetatively adapted to compare the phase of the two received signals and register the phase difference between them as a measure of the distance of the welding arc from the micro ⁇ phone. This is based on the recognition that the phase difference or time delay between the supplied A.C. signal from the signal generator G and the corresponding sound signal received by the microphone in fact represents the propagation time of the sound in air between the welding arc and the microphone.
  • Suitable equipment for measuring the distance between the sound-emitting arc and the microphone is in principle shown in Fig. 8.
  • the electric signal supplied by the microphone M is amplified and filtered in a unit 81 comprising a preamplifier and a band pass filter.
  • the signal prosessed in this manner is transferred to a fur- _ ther unit 82 comprising a further band pass filter and an amplifier adapted to provide an approximately constant out ⁇ put signal independently of the input signal level within a large dynamic signal range.
  • the approximately constant output signal from the unit 82 is converted to rectangular pulses in a converter unit 83, which delivers its output signal to a phase detector unit 84.
  • This unit receives the original A.C. signal from the signal generator G. The phase detection takes place by allowing the original A.C.
  • the detector unit in the form of rectangular pulses, respective ⁇ ly to start and stop a counter.
  • the counted value of this counter is then a measure of the time delay or phase devi ⁇ ation between the two signals and is converted in conventional manner to an analogue voltage level, which may be supplied to a recorder for plotting or registration.
  • the A.C. signal which is superimposed on the welding current and thus the emitted sound from the arc should have a frequency of approximately 18 kHz.
  • the emitted sound is inconvenient to the welding operator and with higher frequencies the wavelength of the sound diminishes to such extent that the dinstance variations that may be measured without counting the number of waves, would be too small in practice.
  • a frequency of 18 kHz corresponds to a wavelength of
  • a distance variation of 1.6 cm corresponds to a phase difference of 360 . It has been found suitable to super ⁇ impose a rectangular waveform on the welding current, as the processing of a signal of this type is easier than the processing of a sinus signal.
  • the sound signal which is picked up by the microphone is, however, approximately sinusoidal. This waveform is maintained throughout the amplifiers and band pass filters, but is converted to rectan ⁇ gular pulses in the converter unit 83 prior to the phase detection in the unit 84.
  • Fig. 9 shows a recorder diagram obtained by means of the equipment shown in Figs. 7 and 8 during a welding test. In this test the welding gun was moved by hand and the detected variations of the protruding length of the elect rode is continusously plotted in the diagram. In addition the means distance from the nozzle of the welding " gun to the workpiece was intentionally increased during the test, and both types of distance variations are clearly indicated in Fig. 9. - *
  • the welding parameters in this test was set to such values that typical continuous material transfer from the welding electrode to the workpiece was obtained. It is, however, in principle no impediments to the use of the present method also with short arc welding. This would, however, require more signal processing, as the microphone signal in this case would contain more background noise and the emitted discrete frequency sound probably would not be continuous, as the signal circuit would be broken a short time interval after each drop release.
  • the electrode pro ⁇ trusion may suitably be measured in both extreme lateral positions of the weaving motion. If then the protruded elec ⁇ trode lengths are equal on both sides, this indicates that -the electrode is weaving symmetrically across the joints. How ⁇ ever, in case the electrode protrusion is greater on one side than on the other, the lateral position of the electrode is corrected in the direction of the greater protrusion.
  • the height from the workpiece to the welding gun is detected by measuring the mean electrode protrusion over several weaving periods. This measurement may suitably be utilised for height level regulation of the welding gun.
  • the difference of electrode protrusion between the center line of the weaving pattern and the extreme electrode positions will change with filling of the welding joint.
  • This feature may be utilised for a regulation of the joint filling by retarding the welding wire feed when the pro ⁇ trusion difference exceeds a oredetermined value.

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Mechanical Engineering (AREA)
  • Arc Welding In General (AREA)
  • Butt Welding And Welding Of Specific Article (AREA)

Abstract

Procede et appareil de soudage a l'arc avec une electrode mobile (E) pour detecter le mouvement de l'arc de soudage (B) par rapport a une position donnee utilisant un microphone (M) place a ladite position donnee pour capter les sons emis par l'arc de soudage (B) de maniere a detecter les variations des sons captes representant le mouvement de l'arc par rapport au microphone (M). Les sons emis par l'arc de soudage (B) et captes par le microphone (M) sont soit des bruits de soudage produits par le procede de soudage lui-meme ou des sons de frequence discrets generes dans l'arc de soudage (B) par superposition d'un signal alternatif sur le courant de soudage. Les variations detectees des sons captes par le microphone (M) sont de preference utilises pour produire un signal de commande pour commander le mouvement de l'electrode de soudage (E) en particulier lorsque l'electrode est concue pour effectuer un mouvement de tissage en travers du joint de soudage (S).
EP80902358A 1979-12-06 1980-12-05 Procede et appareil de soudage a l'arc Withdrawn EP0041970A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NO793978 1979-12-06
NO793978A NO145299C (no) 1979-12-06 1979-12-06 Fremgangsmaate og anordning ved lysbuesveising.

Publications (1)

Publication Number Publication Date
EP0041970A1 true EP0041970A1 (fr) 1981-12-23

Family

ID=19885200

Family Applications (1)

Application Number Title Priority Date Filing Date
EP80902358A Withdrawn EP0041970A1 (fr) 1979-12-06 1980-12-05 Procede et appareil de soudage a l'arc

Country Status (3)

Country Link
EP (1) EP0041970A1 (fr)
NO (1) NO145299C (fr)
WO (1) WO1981001676A1 (fr)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3435829A1 (de) * 1984-09-28 1986-04-10 Siemens AG, 1000 Berlin und 8000 München Sensor fuer die ueberwachung bei der herstellung von schweissnaehten
JP2828985B2 (ja) * 1988-03-18 1998-11-25 株式会社日立製作所 アーク長検出装置，アーク長検出方法，トーチ高さ制御装置，トーチ高さ制御方法，自動溶接装置並びに自動溶接方法
CN102764927B (zh) * 2012-07-03 2014-10-22 广东技术师范学院 一种基于电弧声声谱样本熵的弧焊过程稳定性定量评价方法
CN109623113A (zh) * 2019-01-15 2019-04-16 南昌航空大学 一种基于双耳效应的焊缝位置检测方法及装置
CN114160921B (zh) * 2021-11-22 2023-04-28 湖北文理学院 焊接机器人的焊接控制方法、控制装置及焊接机器人
CN115781094B (zh) * 2022-11-29 2024-08-16 天津工业大学 一种焊缝偏差检测方法及装置

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1919034A1 (de) * 1969-04-15 1970-10-22 Erdmann Jesnitzer Dr Ing Habil Vorrichtung zur Kontrolle von Elektroschweissverfahren
GB1492311A (en) * 1975-03-06 1977-11-16 Atomic Energy Authority Uk Electric arc-welding processes and apparatus therefor
US4350868A (en) * 1975-07-14 1982-09-21 Matsushita Electric Industrial Co., Ltd. Follow-up control apparatus for controlling the movement of a welding weaving device
US4151395A (en) * 1976-07-06 1979-04-24 CRC-Crose, International, Inc. Method and apparatus for electric arc and analogous welding under precision control

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO8101676A1 *

Also Published As

Publication number Publication date
WO1981001676A1 (fr) 1981-06-25
NO145299C (no) 1982-02-24
NO145299B (no) 1981-11-16
NO793978L (no) 1981-06-10

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Legal Events

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PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

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Effective date: 19820209

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Inventor name: KJOSAVIK, DAG G.

Inventor name: KVERNELAND, KJELL OLAVUS

Inventor name: MOLAUG, OLE