Mixed Reality-Enhanced Intuitive Teleoperation with Hybrid Virtual Fixtures for Intelligent Robotic Welding

This paper presents an integrated scheme based on a mixed reality (MR) and haptic feedback approach for intuitive and immersive teleoperation of robotic welding systems. By incorporating MR technology, the user is fully immersed in a virtual operating space augmented by real-time visual feedback from the robot working space. The proposed robotic tele-welding system features imitative motion mapping from the user’s hand movements to the welding robot motions, and it enables the spatial velocity-based control of the robot tool center point (TCP). The proposed mixed reality virtual fixture (MRVF) integration approach implements hybrid haptic constraints to guide the operator’s hand movements following the conical guidance to effectively align the welding torch for welding and constrain the welding operation within a collision-free area. Onsite welding and tele-welding experiments identify the operational differences between professional and unskilled welders and demonstrate the effectiveness of the proposed MRVF tele-welding framework for novice welders. The MRVF-integrated visual/haptic tele-welding scheme reduced the torch alignment times by 56% and 60% compared to the MRnoVF and baseline cases, with minimized cognitive workload and optimal usability. The MRVF scheme effectively stabilized welders’ hand movements and eliminated undesirable collisions while generating smooth welds.

Recognition of Manual Welding Positions from Depth Hole Image Remotely Sensed by RGB-D Camera

The proportion of welding work in total man-hours required for shipbuilding processes has been perceived to be significant, and welding man-hours are greatly affected by working posture. Continuous research has been conducted to identify the posture in welding by utilizing the relationship between man-hours and working posture. However, the results that reflect the effect of the welding posture on man-hours are not available. Although studies on posture recognition based on depth image analysis are being positively reviewed, welding operation has difficulties in image interpretation because an external obstacle caused by arcs exists. Therefore, any obstacle element must be removed in advance. This study proposes a method to acquire work postures using a low-cost RGB-D camera and recognize the welding position through image analysis. It removes obstacles that appear as depth holes in the depth image and restores the removed part to the desired state. The welder’s body joints are extracted, and a convolution neural network is used to determine the corresponding welding position. The restored image showed significantly improved recognition accuracy. The proposed method acquires, analyzes, and automates the recognition of welding positions in real-time. It can be applied to all areas where image interpretation is difficult due to obstacles.

Optimization and Prediction of Melting Efficiency of Mild Steel Weldment, Using Genetic Algorithm

Melting efficiency which indicates how much of the heat deposited by the welding operation is used to produce melting is one of the most important parameters considered in Tungsten Inert Gas (TIG) welding when assessing the performance of welds. In the field of welding, a good melting efficiency results in the development of a dense weld pool. This study is conducted to optimize and predict the melting efficiency of mild steel weldment, using Genetic Algorithm. Genetic Algorithm (GA), which is an optimization method that mimics the evolution process and operates on the basis of the theory of natural selection and evolution was used to analyse the results. The result shows that a combination of current 239.03A, voltage 29.87V, welding speed 56.59mm/s, welding time 79.15 sec, feed rate 130mm/s, will produce optimal melting efficiency of 44.72. Keywords: Melting Efficiency, Mild Steel Weldment, Genetic Algorithm, Optimization and Prediction.

Investigation of friction stir spot welding of high density polyethylene and polypropylene sheets

In this study, two different polymer materials were used. In the joints made with friction stir spot welding, firstly (PP/PP and HDPE/HDPE) and then different materials (PP/HDPE, HDPE/PP) joining processes were carried. The influence of the tool rotational speed and the stirring time on joint formation and weld strength were determined. The temperature of the liquid welding materials varies according to the materials to be combined. High weld strengths were obtained at the friction stir spot welding of similar plastic sheets. The highest weld strengths were obtained in PP-PP welds. Low weld strengths were obtained at the friction stir spot welding of dissimilar plastic sheets because of immiscible and incompatible blends formed during the welding operation. The lowest weld strengths were obtained in PP-HDPE welds. The chemical composition and the phase morphology of the blends, the mechanical scission occurrence and the welding residual stresses determine the strength of the welds.

Methodology for Human Robot Interface in Arc Welding Operation - An Industry Case study

Welding is a significant industrial application that has been implemented since the early 18th century. The introduction of welding robots in the 19th century resulted in drastic improvements in the field of welding like improving the accuracy of welding, quality of the weld, etc., However, there is no literature which briefs the industry methodology to interface HMI with the industrial robots. In this paper, MOTOMAN AR1440 Industrial Welding Robot is interfaced with the Human Machine Interface (HMI) panel to improve the communication between the machine and the operator. This improves the safety and handling of the robot. The robot trajectory is taught using a teach pendant and the HMI panel is designed to control the robot. The robot and the HMI panel are interfaced via Ethernet communication. Thus, the main objective of this paper is to brief an industry methodology to interface an AR1440 robot with an HMI panel for arc welding application thereby, improving the communication between the machine and the worker.

Efficient Spot Welding Sequence Simulation in Compliant Variation Simulation

Geometric variation is one of the sources of quality issues in a product. Spot welding is an operation that impacts the final geometric variation of a sheet metal assembly considerably. Evaluating the outcome of the assembly, considering the existing geometrical variation between the components can be achieved using the Method of Influence Coefficients (MIC), based on the Finite Element Method (FEM). The sequence, with which the spot welding operation is performed, influences the final geometric deformations of the assembly. Finding the optimal sequence that results in the minimum geometric deformation is a combinatorial problem that is experimentally and computationally expensive. For an assembly with N number of welds, there are N! possible sequences to perform the spot welding operation. Traditionally, spot welding optimization strategies have been to simulate the geometric variation of the spot-welded assembly after the assembly has been positioned in an inspection fixture, using an appropriate measure of variation. In this approach, the calculation of deformation after springback is one of the most time-consuming steps. In this paper, the cause of variation in the deformations after the springback, between different sequences is identified. The relative displacements of the weld points in the assembly fixture, when welded in a sequence, is the source of such behavior. Capturing these displacements leads to large time savings during sequence optimization. Moreover, this approach is independent of the inspection fixture. The relative weld displacements have been evaluated on two sheet metal assemblies. The sequence optimization problem has been solved for the two assemblies using this approach. The optimal sequence, the corresponding final assembly deformations, and the time-consumption have been compared to the traditional approach. The results show a significant correlation between the weld relative displacements in the assembly fixture, and the assembly deformation in the inspection fixture. Considering the relative weld displacement makes each assembly evaluation less time-consuming, and thereby, sequence optimization time can be reduced up to 30%, compared to the traditional approach.

Welding Operation Technique of Welding Electrode Arc Welding Overhead Welding Test Board

Welding electrode arc welding, upside welding, single side welding, double side forming welding operation technology is the most difficult welding process in manual arc welding operation. It is an operation technology that senior welding operators must master, and it reflects the technical level of the welding welder. . In this paper, the welding operation essentials and operation skills of backing welding, filling welding and cover welding are studied for the welding operation of the back welding test board, which creates a theoretical basis for the improvement of the welding operator's operation skills.

Ertical Butt Welding Technology of Q355g Small Diameter Pipe TIG

In this paper, according to the requirements of welder's technical qualification specification, combined with the practice training topic of TIG vertical butt welding, we have repeatedly trained the operation process of TIG vertical butt welding of q355g steel pipe with specification of Φ 60 х 5,And we adopt the following process measures in the welding process: before welding, we make V-shaped tooling by combining with the workpiece ; when welding, we choose reasonable process parameters; at the same time, we pay more attention to the welding operation skills of backing and cover layer. Therefore, we have achieved satisfactory weld quality, and the relevant experience has been popularized in the teaching process of the school to obtain good evaluation.

Investigation of CGHAZ During Single and Multi Pass Submerged Arc Welding of High Strength Steel

Owing to its fine structure and high strength to weight ratio, high strength low alloy (HSLA) steel, API X80, is most preferred grade for application in oil and gas pipeline fabrication. Coarse grain heat affected zone (CGHAZ) formed during fabrication of pipelines using high heat input welding operation like submerged arc welding (SAW) is the crucial area for failure during the application of welded structure. Large detrimental changes occur in mechanical behavior and microstructural characteristics of HAZ due to thermal cycles of the welding operation. In this study, CGHAZ built during first-pass of SAW and when it gets reheated during second-pass as well as third-pass is investigated at each stage for mechanical properties (impact toughness and hardness) as well as microstructural changes. Peak temperature of CGHAZ is determined using upper critical temperature limit of steel. For identifying the lower and upper critical temperature for this steel, dilatometry tests were performed and values were found in well agreement with theoretically determined ones. Comparative analysis of mechanical properties as well as microstructure in simulated HAZ with parent material is also discussed. It is found that subsequent reheating of CGHAZ (formed during first-pass of welding) because of second and third-pass of welding has beneficial effect. Work of this study will guide the engineers to put the limit on heat input in terms of number of passes during welding of such high strength pipeline steels.