Vision and spectroscopic sensing for joint tracing in narrow gap laser butt welding

Nilsen, Morgan; Sikström, Fredrik; Christiansson, Anna-Karin; Ancona, Antonio

doi:10.1016/j.optlastec.2017.05.011

Cited by 22 publications

(6 citation statements)

References 22 publications

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“…The recommended cooling time t8/5 for the steel is from 5 to 15 seconds according to the manufacturer [4]. The steel has a typical carbon equivalent (CEV) of 0.58 which is associated with challenging weldability.…”

Section: Methodsmentioning

confidence: 99%

“…However, basic arc welding methods such as gas metal arc welding (GMAW) is the welding method that is usually used in the industry due the equipment being cheap to obtain and the seam tolerances being less restrictive to those of laser based welding technologies. [4] This means that achieving lower heat input in the welding process is usually done by using multiple weld passes, because lowering parameters such as current or voltage or increasing the weld speed decreases material deposition rate which in turn leads to multiple weld passes being required to fill the weld seam.…”

Section: Introductionmentioning

confidence: 99%

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Effect of forced cooling after welding on CGHAZ mechanical properties of a martensitic steel

2018

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The effects of forced cooling, meaning forced cooling rate and forced cooling finish temperature, on the tensile and impact toughness properties of simulated weld coarse-grained heat affected zones have been studied for a commercial grade martensitic steel with a yield strength of 960 MPa. The simulations were done by using a Gleeble 3800 to give forced cooling finish temperatures of 500, 400, 300, 200 and 100 °C and forced cooling rates of 50 and 15 °C/s. For the steel studied, strength significantly increased with no significant negative effects on impact toughness when the steel was cooled rapidly to 200 or 100 °C at 15 °C/s. The results indicate that it may be possible to improve welding productivity and mechanical properties of the steel by using forced cooling down to 100 ∘ C to reduce waiting time between weld passes.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of forced cooling after welding on CGHAZ mechanical properties of a martensitic steel

2018

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“…The only critical situation is then if the offset starts exactly at the tack weld, and this is considered relatively unlikely. Also, as suggested in [21], a second sensor system based on spectrometer data that is not sensitive to tack welds could be used in addition to the camera to robustify the tracking. The system can successfully estimate the joint position with an error less than 0.56 mm except for this specific situation.…”

Section: Performancementioning

confidence: 99%

Robust vision-based joint tracking for laser welding of curved closed-square-butt joints

Nilsen

Sikström

Christiansson

et al. 2018

Int J Adv Manuf Technol

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Robotized laser beam welding of closed-square-butt joints is sensitive to how the focused laser beam is positioned in relation to the joint, and existing joint tracking systems tend to fail in detecting the joint when the gap and misalignment between the work pieces are close to zero. A camera-based system is presented based on a high dynamic range camera operating with LED illumination at a specific wavelength and a matching optical filter. An image processing algorithm based on the Hough transform extracts the joint position from the camera images, and the joint position is then estimated using a Kalman filter. The filter handles situations, when the joint is not detectable in the image, e.g., when tack welds cover the joint. Surface scratches, which can be misinterpreted as being the joint, are handled by a joint curve prediction model based on known information about the nominal path defined by the robot program. The performance of the proposed system has been evaluated off line with image data obtained during several welding experiments.

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“…Then, an adaptive Kalman filter and Elman neural network were used to improve the accuracy [ 11 ]. Nilsen et al estimated the offset of the joint relative to the torch in laser welding by the image of the keyhole and the spectrum of the plasma sprayed from the keyhole, respectively, and combined these two methods to construct a composite sensing system [ 12 ]. Shah et al used an auxiliary light source to illuminate the workpiece.…”

Section: Introductionmentioning

confidence: 99%

A Vision Based Detection Method for Narrow Butt Joints and a Robotic Seam Tracking System

Xue

Chang

Peng

et al. 2019

Sensors

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Automatic joint detection is of vital importance for the teaching of robots before welding and the seam tracking during welding. For narrow butt joints, the traditional structured light method may be ineffective, and many existing detection methods designed for narrow butt joints can only detect their 2D position. However, for butt joints with narrow gaps and 3D trajectories, their 3D position and orientation of the workpiece surface are required. In this paper, a vision based detection method for narrow butt joints is proposed. A crosshair laser is projected onto the workpiece surface and an auxiliary light source is used to illuminate the workpiece surface continuously. Then, images with an appropriate grayscale distribution are grabbed with the auto exposure function of the camera. The 3D position of the joint and the normal vector of the workpiece surface are calculated by the combination of the 2D and 3D information in the images. In addition, the detection method is applied in a robotic seam tracking system for GTAW (gas tungsten arc welding). Different filtering methods are used to smooth the detection results, and compared with the moving average method, the Kalman filter can reduce the dithering of the robot and improve the tracking accuracy significantly.

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Vision and spectroscopic sensing for joint tracing in narrow gap laser butt welding

Cited by 22 publications

References 22 publications

Effect of forced cooling after welding on CGHAZ mechanical properties of a martensitic steel

Effect of forced cooling after welding on CGHAZ mechanical properties of a martensitic steel

Robust vision-based joint tracking for laser welding of curved closed-square-butt joints

A Vision Based Detection Method for Narrow Butt Joints and a Robotic Seam Tracking System

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