Novel methods for online high-accuracy quality control of laser welded blanks and tubes

Wildmann, D.; Halschka, Martin; Schwarz, Joachim

doi:10.2351/1.5059509

Cited by 3 publications

(2 citation statements)

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“…Abel observed bead surface using CCD camera, and detected weld defects such as porosity and undercut by image processing (5). Wildmann determined the weld quality using CCD camera in tailored blank welding (6). In Wildmann's studies, reliability of inspection quality was limited by resolution of the CCD in the image processing method and it needed much Title of Publication (to be inserted by the publisher) time for image data processing.…”

Section: Introductionmentioning

confidence: 99%

On-Line Penetration Depth Measurement System Using Infrared Temperature Sensing on Co<sub>2</sub> Laser Welding

Lee

Kim

2004

KEM

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Laser beam for welding has small spot size and high energy density. Laser beam welding process has some advantage such as high production speed, good weld quality, and low heat distortion. On the contrary, laser beam welding causes some problem from its inherent characteristics. The laser beam should be arranged exactly at weld line and focal length should be controlled at limited range. Small stray of welding conditions causes severe problems of welding quality. Even if the welding conditions are optimum range, unwanted results cause from the distortion of welding heat input. Therefore, on-line welding quality monitoring is needed for laser welding in automobile and other industry.This study investigated the feasibility of penetration depth measurement using infrared temperature sensing from the weld surface. The profile of the weld surface temperature was measured using photo detector array. Thermal radiation from the weld surface was focused to photodiode array via optical lens. Infrared temperature measurement system was calibrated using electrical resistance heating of steel sheet. Test results indicated that output signal of the photodiode increased exponentially with the increase of temperature of the sample. Surface temperature behind the weld pool was matched with penetration depth and bead width. From the results, the monitoring device of surface temperature using infrared detector array was applicable for real time penetration depth control.

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Section: Introductionmentioning

confidence: 99%

On-Line Penetration Depth Measurement System Using Infrared Temperature Sensing on Co<sub>2</sub> Laser Welding

Lee

Kim

2004

KEM

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“…Several types of sensor have been developed to monitor the welding process, among which the photodiode sensor (PS) has been extensively used for process sensing and control [5][6][7][8][9][10][11][12]. Some researchers have also demonstrated the optimization and closed-loop control of focal point position [13][14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Double closed-loop control of the focal point position in laser beam welding

Zhang

Chen

Jiang

et al. 2003

Meas. Sci. Technol.

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Focal point position control is significant in deep penetration laser beam welding because it is apt to change during welding due to some fluctuating factors, such as the non-planar workpiece, welding distortion and thermal focusing. This work describes the design of a double closed-loop control of the focal point position for CO2 laser beam welding. A photodiode sensor (PS) and a plasma charge sensor (PCS) are simultaneously utilized to detect the optical emission and plasma charge current in welding. It is found that the PCS signal could be used to control the nozzle–workpiece distance based on the decrease of PCS signal intensity with increasing nozzle–workpiece distance. The PS signal could be used to control the focal point position by using PS signal variation with focal point position. Therefore, a system for double closed-loop controlling the focal point position has been set up, using the PCS signal to control the nozzle–workpiece distance and the PS signal to control the focal point position. The experimental results with a non-planar workpiece show that the double closed-loop control of the focal point position not only automatically follows the contours of the workpiece surface, but also controls the focal point position constant by compensating the effect of thermal focusing.

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Machine vision – The powerful tool for quality assurance of laser welding and brazing

Halschka¹,

Schwarz²,

Wildmann³

et al. 2003

International Congress on Applications of Lasers &Amp; Electro-Optics

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Novel methods for online high-accuracy quality control of laser welded blanks and tubes

Cited by 3 publications

References 0 publications

On-Line Penetration Depth Measurement System Using Infrared Temperature Sensing on Co<sub>2</sub> Laser Welding

On-Line Penetration Depth Measurement System Using Infrared Temperature Sensing on Co<sub>2</sub> Laser Welding

Double closed-loop control of the focal point position in laser beam welding

Machine vision – The powerful tool for quality assurance of laser welding and brazing

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