• Proceedings of the KWS Conference
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• 2006.05a
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• pp.304-306
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• 2006

Positioning the workpiece accurately and preventing the weld distortion, tack welding is often performed before main welding in the construction of welded structures. The weld bead size of the tack weld is determined according to the workpiece thickness, weld length, weld joint type etc. However, this tack weld deteriorates the final weld bead profile, so that the grinding process is usually adopted for the uniform weld bead profile. In this study, an experimental method for the selection of optimal welding condition was proposed in the fillet weld which was done over the tack weld. This method uses the response surface analysis in which the leg length and the reinforcement height of weld bead were chosen as the quality variables of weld bead profile. The overall desirability function, which was combined desirability function for the two quality variables, was used as the objective function for getting the optimal welding condition. From the result, it was revealed that a uniform weld bead can be obtained by adopting the optimal welding condition which was determined according to the method proposed.

• Journal of Welding and Joining
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• v.24 no.5
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• pp.29-36
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• 2006

In this study, an experimental method for the selection of optimal welding condition was proposed in the fillet weld which was done over the tack weld. This method used the response surface analysis in which the leg length and the reinforcement height were chosen as the quality variables of the weld bead profile. The overall desirability function, which was combined desirability function fur the two quality variables, was employed as the objective function for getting the optimal welding condition. In the experiments, the target values of the leg length and the reinforcement height are 6m and zero respectively for the horizontal fillet weld of 10mm thickness mild steel. The optimal welding conditions could predict the weld bead profile(leg length and reinforcement height) as 6.00mm and 0.19mm without tack weld and 6.00mm and 0.48mm with tack weld. from a series of welding test, it was revealed that a uniform weld bead can be obtained by adopting the optimal welding condition which was determined according to the method proposed.

• Journal of Welding and Joining
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• v.23 no.4
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• pp.73-80
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• 2005

Arc blow being occurred by Electro-Magnetic force(EMF) during the electric arc welding prevents the formation of a sound weldment. In this study, the effects of arc position, groove size, tack weld and base plate on the EMF in a butt-joint welding of mild steel plate are analyzed by a computer simulation based on the finite element method. The EMF can be numerically identified to be caused by a difference of the magnetic flux-density between ahead of and behind the arc in case that the workpiece locates asymmetrically around the uc. When there exists an air gap of groove ahead of the arc in the welding direction, the similar magnetic force has been producted regardless of the arc position and the gap size. The tack weld alleviates the magnetic force to about one fourth at the finish end of the workpiece. The magnetic force can be also significantly reduced with the base plate to about one fifth at the start end of the workpiece containing a tack weld.

• Journal of the Korean Professional Engineers Association
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• v.33 no.5
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• pp.59-64
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• 2000

This improvement case to be introduced of all welders, welding operator, tack welders and welding inspector for reducing of welding defect rate and good quality.

• Proceedings of the KWS Conference
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• 2000.10a
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• pp.40-42
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• 2000

This paper presents a new method of segmenting a one-dimensional signal into a set of features of type(line, Vee-groove, Lap-joint and etc.), A set of requirements for the segmentation process result from the application area, which in this case are laser welding, GMAW(Gas Metal Arc Welding), SAW(Submerged Arc Welding) and high speed tack welding. The algorithm is able to detect an exact welding position in the presence of noise and missing data, yet is reasonably economical to implement

• Journal of the Society of Naval Architects of Korea
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• v.49 no.1
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• pp.87-92
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• 2012

Alignment of the main plates during the tack welding is essential to block assembly since most of the curved blocks and outfitting parts are assembled on the jigs and fixtures. Tact welding of main plates is the initial process of the curved hull block assembly. Due to the heavy weight of the main plates it is difficult to locate the plate on the accurate position of the jig and fixtures before welding. The conventional masonry process requires much time and manual work in order to achieve the accurate alignment. This labour-intensive process results in relatively high errors and correction works. Due to their larger dimensions and heavier weights, these hull blocks are not ergonomically desirable and, therefore, various mechanical devices such as hydraulic balancers or hydraulic jigs are used for the plate alignment. In this study, the position-sensing scheme implemented by sensors is presented in order to align the main plates on the accurate position during the hull block assembly. Integrating the Infrared photo sensors and micro processor unit, a small scaled prototype of the position-sensing module is developed to determine the alignment of main plates.

• Proceedings of the Korea Society for Simulation Conference
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• 2003.11a
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• pp.185-192
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• 2003

Digital Manufacturing-based production could be very effective in shipbuilding in order to save costs and time, to increase safety for workers, and to prevent bottleneck processes in advance. Digital shipbuilding system, a simulation-based production tool, is being developed to achieve such aspects in Korea. To simulate material flow in a subassembly line at a shipyard, the product, process and resources was modeled for the subassembly process which consisted of several sub-processes such as tack welding, piece alignment, tack welding, and robot welding processes. The analysis and modeling were carried out by using the UML(Unified Modeling Language), an object-oriented modeling method as well as IDEF(Integration DEFinition), a functional modeling tool. Initially, the characteristics of the shop resources were analyzed using the shipyard data, and the layout of the subassembly line was designed with the resources. The production process modeling of the subassembly lines was performed using the discrete event simulation method. Using the constructed resource and process model, the productivity and efficiency of the line were investigated. The number of workers and the variations In the resource performance such as that of a new welding robot were examined to simulate the changes in productivity. The bottleneck process floated according to the performance of the new resources. The proposed model was viewed three-dimensionally in a digital environment so that interferences among objects and space allocations for the resources could be easily investigated

• Proceedings of the KWS Conference
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• 2003.11a
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• pp.150-152
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• 2003

This simulation was carried out to estimate the process time and to improve the operation efficiency. The subassembly process consists of piece arrangement, tack welding, robot welding, manual welding and the robot welding of them was the focus of the simulation. Robot welding stage was analyzed by UML and IDEFø method, and then it was represented as the three-dimensional model(simulator) based on the analysis. The output of this simulation was the cycle time for one day's work. The cycle time for the different torch and the different piece arrangement was investigated by the 3-dimensional simulation.

• Proceedings of the KWS Conference
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• v.43
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• pp.289-291
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• 2004

The purpose of this study is to identify the effects of the length of tack weldment on the rotational distortion at the one side SA butt weldment using experiment. The maximum rotational distortion at the end of the SA weldment decrease with an increase in the length of tack weld length, while the maximum rate of the distortion increases. This result indicates that the increase of the length of the tack weldment at the one-side SA butt weldment does not prevent the hot cracks.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1998.10a
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• pp.539-544
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• 1998

Generally, welding gap is a serious factor of a falling-off in weld quality among various kind of weld defect. Welding gap is created between two work piece in GMAW(Gas Metal Arc Welding) of horizontal fillet weld because surface of workpiece is not flat by cutting process. In these days, there were many attempts to detect welding gap. though we prevalently use the vision sensor or arc sensor in welding process, it is difficult to detect welding gap for improvement of welding quality. But we have a trouble to find relationship between welding gap and many welding parameters due to non-linearity of welding process. As mentioned about the various difficult problem, we can detect welding gap precisely using neural networks which are able to model non-linear function. Also, this paper was proposed real-time monitoring of weld bead shape to find effect of welding gap and to estimate weld quality. Monitoring of weld bead shape examined the correlation of welding parameters with bead eometry using learning ability of neural networks. Finally, the developed system, welding gap detecting system and bead shape monitoring system, is expected to the successful capability of automation of welding process by result of simulation.