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WO2000041837A1 - Procede de detection d'erreurs dans les traitements au laser - Google Patents

Procede de detection d'erreurs dans les traitements au laser Download PDF

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Publication number
WO2000041837A1
WO2000041837A1 PCT/CA2000/000026 CA0000026W WO0041837A1 WO 2000041837 A1 WO2000041837 A1 WO 2000041837A1 CA 0000026 W CA0000026 W CA 0000026W WO 0041837 A1 WO0041837 A1 WO 0041837A1
Authority
WO
WIPO (PCT)
Prior art keywords
emissions
samples
emission
coefficient
laser
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.)
Ceased
Application number
PCT/CA2000/000026
Other languages
English (en)
Inventor
Hongping Gu
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.)
ArcelorMittal Tailored Blanks Americas Ltd
Original Assignee
Powerlasers Ltd
Cosma Powerlasers Ltd
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 Powerlasers Ltd, Cosma Powerlasers Ltd filed Critical Powerlasers Ltd
Priority to AU20874/00A priority Critical patent/AU2087400A/en
Priority to CA002323802A priority patent/CA2323802A1/fr
Publication of WO2000041837A1 publication Critical patent/WO2000041837A1/fr
Anticipated expiration legal-status Critical
Ceased 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
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/03—Observing, e.g. monitoring, the workpiece
    • B23K26/032—Observing, e.g. monitoring, the workpiece using optical means
    • 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
    • B23K2101/00—Articles made by soldering, welding or cutting
    • B23K2101/18—Sheet panels
    • B23K2101/185—Tailored blanks

Definitions

  • the present invention relates to laser processing.
  • the quality of the laser processing depends on the consistency of the component being processed as well as the consistent application of the laser beam.
  • Welding with a continuous wave CO laser is a well-established method for joining sheet metals in industry. Millions of tailored blanks are welded every year in the automotive industry. In production, the edges to be joined are usually prepared by a shear machine and the prepared sheets are transferred from the shear machine to the welding cell. It is inevitable that damage to the cutting edges will occur. Furthermore, cases of mismatch of the welding sheets will happen in a production environment. As a result, the laser-welded seams are not always perfect. Ripples, pinholes and large concavities in the welds can occur and detection of these defects in real time is desirable for quality control.
  • Optical emissions from the welding site contain significant information about the efficacy of the welding process.
  • the emissions from the weld site are monitored and characteristics of the emissions used to control the laser processing.
  • the characteristics of an image may be monitored and used to derive inputs to a fuzzy logic control.
  • Such an arrangement provides good control over the laser processing and allows adjustments to be made as the processing progresses.
  • the present invention monitors at least one signal obtained from the weld zone over a predetermined period. A set of samples is taken and an average obtained for each signal over this period. Fluctuations of samples from the average are monitored and compared to the average to obtain a coefficient indicative of the changes in the laser processing. Changes in the coefficient may then be used to monitor the laser processing either by controlling the parameters or by indicating potential flaws.
  • Figure 1 is a schematic representation of a laser welding process.
  • Figure 2 is a view on the line 2-2 of figure 1.
  • Figure 3 is a view on the line 3-3 of figure 2.
  • Figure 4 is a view in the direction of arrow a of figure 1.
  • Figure 5 is a representative signal obtained for UV emissions from the apparatus of figure 1.
  • Figure 6 is a representative signal obtained for IR emissions from the apparatus of figure 1.
  • Figures 7 - 12 are traces obtained from processing the traces represented in figures 5 and 6 for a series of tests performed with the apparatus of figure 1.
  • a laser processing apparatus 10 includes a laser 12 that propagates a beam 14 to impinge upon a work piece 16.
  • the work piece 16 may be one of a variety of forms but in the examples illustrated comprises a pair of sheet metal components 18, 20 ( Figure 4) abutting along respective edges 22, 24 to be welded to one another. It will however be appreciated that the work piece 16 may be a single sheet of material to be cut by laser beam 14 or may be a component to be surface treated by the laser beam 14.
  • An optical monitoring assembly 26 includes an optical head 28 secured to the laser 12 by means of an arm 30.
  • the optical head 28 includes a housing 32 containing optical elements 34 that may be relatively adjustable to provide a variable focus for the monitoring assembly 26.
  • Optical fibers 36 are secured to the housing 32 and extend to respective photo diodes
  • optical fibers 36 are provided and arranged in quadrature within the housing 32 and each will be associated with a respective photodiode 38a, 38b, 38c, 38d. It will be appreciated however that more or less optic fibers may be utilized depending upon the mode of control to be implemented as will be described in further detail below.
  • Each of the photodiodes 38 provides an output signal 40 connected to a control 42.
  • Control 42 may operate in one or more of a plurality of modes to extract a control signal for laser 12.
  • the control signal 44 may be used to control the movement to the laser 12 relative to the work piece 16 or the operation of the laser 12 as it moves over the work piece.
  • the laser 12 is moveable along mutually perpendicular axes x, y, z relative to the work piece 16 to permit the beam 14 to follow the desired path.
  • the beam 14 impinges on the surfaces of components 18, 20 and produces a weld pool 50.
  • the beam 14 moves along in a direction parallel to the edges 22, 24 it progressively melts the edges which then solidify to weld the two components 18, 20 to one another.
  • Control of the beam 14 is provided by the monitoring assembly 26 in conjunction with the control 42.
  • the optical head 28 focuses the fibers 36 to respective discreet locations (indicated as 37a,37b,37c,37d) adjacent to or within the weld pool 50.
  • one of the fibers 36a is focused in advance of the pool 50 at 37a and another, 36b, focused behind the pool 50 at 37b.
  • the two other fibers 36c and 36d respectively are focused on opposite sides of the pool 50 at 37c and 37d respectively.
  • the respective photodiodes 38 will therefore receive information from the plume, the pool itself and regions surrounding the weld pool and may use that information to provide control signals to the control 42.
  • the information received will relate to the intensity of the emissions at the pool 50 and this information may be refined by providing appropriate filters to select specific wave lengths of radiation for transmission to the photodiode 38 or by selecting a photodiode with specific response characteristics.
  • the control signals 40 are used to monitor the efficacy of the laser processing. As can be seen in figures 5 and 6 two different signals are extracted from the detected emissions, namely a UN signal indicated (x) and an IR signal indicated (y).
  • the signals received from a pair of fibers are used to provide respective signals.
  • a signal received from the plume would typically have a stable UV content and a signal from the pool would have a stable IR content.
  • stable signals can be obtained for each selected parameter.
  • a single fiber may be used for monitoring both parameters but in this case it is advantageous to time shift(s) the sampling intervals for each parameter so that separate events are monitored. Where two fibers are used a time shift is not necessary although may be incorporated if desired.
  • x 0 and y 0 are the mean values of these two set of data such that
  • ⁇ c — ⁇ — + r —-a
  • ⁇ , ⁇ and ⁇ indicate the deviation of individual samples from the average of the whole set of samples to provide the coefficient ⁇ . The greater the deviation and more prolonged the deviation, the greater the value of ⁇ .
  • the correlation coefficient ⁇ is close to 1. If the absolute values of the measured emissions vary progressively, as may be expected with a satisfactory weld process, the values of Ax, and ⁇ y, would vary only slightly relative to the mean x ⁇ yo- Accordingly, the coefficient ⁇ would remain close to 1. However, when disturbance occurs, large spikes or an extremely low signal would be detected. Some of the ⁇ x.or Ay, become large, so that ⁇ and y could be a large value compared to x 0 and y ⁇ In this event, the value, ⁇ and ⁇ are significant and therefore the value of the coefficient drops considerably. Larger disturbances or significant transient conditions, therefore, cause a bigger drop in ⁇ value. In this way, ⁇ can be used to indicate various weld faults, from surface roughness or ripples to pinholes and a failed weld.
  • a third sample was arranged with a gap at each end of the seam as shown schematically in figure 9a.
  • the coefficient ⁇ has a low value as the weld is unstable but attains values greater than 0.9 in the zone where the sheets abut.
  • the coefficient ⁇ again reduces to values of 0.6 to 0.8.
  • pinholes were replicated by filing nicks in the edge at specific locations.
  • the location of the pinholes is clearly identifiable on the trace of figure 10(b) by the reduction of the value of the coefficient ⁇ to as low as 0.4. Between the pinholes, a stable weld is attained.
  • the value of the coefficient ⁇ may be used in a number of ways. Firstly, a value of ⁇ below a certain value may be used as a flag to indicate that a welded component may need further inspection. Because the signal is correlated to time, the position of the potential flaw may be located on the component and a visual inspection made. If the flaw is acceptable or occurs in an area of the component that may subsequently be removed then the component could be used. Otherwise the component is rejected. Alternatively, the value of coefficient ⁇ may be utilized as an error signal in a closed loop control for laser 12. It will be noted that the tests above were conducted under constant weld parameters. The value of the coefficient may be used to control the speed of the weld head along the seam so that as, for example, the gap widens, the speed reduces to maintain a satisfactory weld.
  • the value of the coefficient ⁇ may be used as an input to a fuzzy logic control, as exemplified in the above US patent with an appropriate rule set developed on the basis of observed characteristics.
  • correlation coefficient ⁇ By using correlation coefficient ⁇ to describe the welds, a simple and effective indication of weld quality is obtained. Furthermore, the description of coefficient ⁇ is universal and is not affected by different systems parameters such as laser power on achievable welding speed. It is also not affected by the gain of the signal detection device. As a further advantage no precise optical alignment is required for the detecting system.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Mechanical Engineering (AREA)
  • Laser Beam Processing (AREA)

Abstract

Selon cette invention, les erreurs susceptibles d'être commises lors de traitements au laser, tels que la soudure, de composants, peuvent être identifiées par détermination d'une moyenne à partir d'un ensemble d'échantillons et par suivi de l'écart à la moyenne à l'intérieur de cet ensemble. Un coefficient représentatif des écarts d'un ensemble moyen de conditions est élaboré. Ce coefficient permet de contrôler plus d'un paramètre, en général les émissions IR et UV provenant du traitement au laser.
PCT/CA2000/000026 1999-01-14 2000-01-14 Procede de detection d'erreurs dans les traitements au laser Ceased WO2000041837A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU20874/00A AU2087400A (en) 1999-01-14 2000-01-14 Method for laser processing fault detection
CA002323802A CA2323802A1 (fr) 1999-01-14 2000-01-14 Algorithme de filtration inverse pour la detection de defauts du soudage au laser

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US11590299P 1999-01-14 1999-01-14
US60/115,902 1999-01-14

Publications (1)

Publication Number Publication Date
WO2000041837A1 true WO2000041837A1 (fr) 2000-07-20

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CA2000/000026 Ceased WO2000041837A1 (fr) 1999-01-14 2000-01-14 Procede de detection d'erreurs dans les traitements au laser

Country Status (3)

Country Link
AU (1) AU2087400A (fr)
CA (1) CA2323802A1 (fr)
WO (1) WO2000041837A1 (fr)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002002268A1 (fr) * 2000-07-06 2002-01-10 Aerospatiale Matra Ccr Procede de detection et d'identification de defauts dans un cordon de soudure realise par faisceau laser
EP1238744A1 (fr) * 2001-02-23 2002-09-11 Nissan Motor Co., Ltd. Méthode et appareil de contrôle de la qualité du soudage d' un joint soudé par laser
EP1361015A1 (fr) * 2002-05-07 2003-11-12 C.R.F. Società Consortile per Azioni Méthode et appareil de contrôle de la qualité du soudage d' un joint soudé par laser, en particulier pour un joint soudé par laser entre des ébauches coupées sur mesure
EP1371443A1 (fr) * 2002-06-14 2003-12-17 C.R.F. Società Consortile per Azioni Dispositif et méthode pour contrôler des soudures laser et pour indiquer la qualité de ces soudures
WO2004087362A3 (fr) * 2003-03-31 2005-04-14 Hypertherm Inc Architecture de commande centralisee pour un systeme de traitement de materiaux au laser
US7186947B2 (en) 2003-03-31 2007-03-06 Hypertherm, Inc. Process monitor for laser and plasma materials processing of materials
RU2368931C2 (ru) * 2004-01-13 2009-09-27 К.Р.Ф. Сочиета Консортиле Пер Ациони Способ для управления качеством промышленных процессов, в частности лазерных сварочных процессов
US7595894B2 (en) 2006-06-02 2009-09-29 General Electric Company Profilometry apparatus and method of operation
RU2395828C2 (ru) * 2004-12-30 2010-07-27 К.Р.Ф. Сочиета Консортиле Пер Ациони Модуль со средством первичного измерительного преобразователя для контроля промышленных процессов

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5486677A (en) * 1991-02-26 1996-01-23 Fraunhofer-Gesellschaft Zur Forderung Der Angewandten Forschung E.V. Method of and apparatus for machining workpieces with a laser beam
US5517420A (en) * 1993-10-22 1996-05-14 Powerlasers Ltd. Method and apparatus for real-time control of laser processing of materials
US5651903A (en) * 1995-10-12 1997-07-29 Trw Inc. Method and apparatus for evaluating laser welding

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5486677A (en) * 1991-02-26 1996-01-23 Fraunhofer-Gesellschaft Zur Forderung Der Angewandten Forschung E.V. Method of and apparatus for machining workpieces with a laser beam
US5517420A (en) * 1993-10-22 1996-05-14 Powerlasers Ltd. Method and apparatus for real-time control of laser processing of materials
US5651903A (en) * 1995-10-12 1997-07-29 Trw Inc. Method and apparatus for evaluating laser welding

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6947802B2 (en) 2000-04-10 2005-09-20 Hypertherm, Inc. Centralized control architecture for a laser materials processing system
FR2811427A1 (fr) * 2000-07-06 2002-01-11 Aerospatiale Matra Ccr Procede de detection et d'identification de defauts dans un cordon de soudure realise par faisceau laser
WO2002002268A1 (fr) * 2000-07-06 2002-01-10 Aerospatiale Matra Ccr Procede de detection et d'identification de defauts dans un cordon de soudure realise par faisceau laser
US6937329B2 (en) 2000-07-06 2005-08-30 Aerospatiale Matra Ccr Method for detecting and identifying defects in a laser beam weld seam
EP1238744A1 (fr) * 2001-02-23 2002-09-11 Nissan Motor Co., Ltd. Méthode et appareil de contrôle de la qualité du soudage d' un joint soudé par laser
US6710283B2 (en) 2001-02-23 2004-03-23 Nissan Motor Co., Ltd. Laser weld quality monitoring method and system
EP1361015A1 (fr) * 2002-05-07 2003-11-12 C.R.F. Società Consortile per Azioni Méthode et appareil de contrôle de la qualité du soudage d' un joint soudé par laser, en particulier pour un joint soudé par laser entre des ébauches coupées sur mesure
EP1371443A1 (fr) * 2002-06-14 2003-12-17 C.R.F. Società Consortile per Azioni Dispositif et méthode pour contrôler des soudures laser et pour indiquer la qualité de ces soudures
WO2004087362A3 (fr) * 2003-03-31 2005-04-14 Hypertherm Inc Architecture de commande centralisee pour un systeme de traitement de materiaux au laser
JP2006521933A (ja) * 2003-03-31 2006-09-28 ハイパーサーム インコーポレイテッド レーザ材料加工システムのための集中制御アーキテクチャ
US7186947B2 (en) 2003-03-31 2007-03-06 Hypertherm, Inc. Process monitor for laser and plasma materials processing of materials
CN100471610C (zh) * 2003-03-31 2009-03-25 人工发热机有限公司 激光材料加工系统的集中控制结构
RU2368931C2 (ru) * 2004-01-13 2009-09-27 К.Р.Ф. Сочиета Консортиле Пер Ациони Способ для управления качеством промышленных процессов, в частности лазерных сварочных процессов
RU2395828C2 (ru) * 2004-12-30 2010-07-27 К.Р.Ф. Сочиета Консортиле Пер Ациони Модуль со средством первичного измерительного преобразователя для контроля промышленных процессов
US7595894B2 (en) 2006-06-02 2009-09-29 General Electric Company Profilometry apparatus and method of operation

Also Published As

Publication number Publication date
CA2323802A1 (fr) 2000-07-20
AU2087400A (en) 2000-08-01

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