Torch Position Research Articles

Sensor-based measurement system for welding torch position

Sensor-based measurement system for welding torch position

Monitoring Welding Torch Position and Posture Using Reversed Electrode Images – Part II, Experimental and Analysis for the REI-TPA Model

This paper is a sequel to the previous paper. In the previous research (Ref. 1), a REI-TPA model was established to quantitively relate reversed electrode images (REIs) to welding torch position and attitude (TPA). In this research, the REI-TPA model was validated with bead-on-plate welding experiments on S304 stainless steel plates. The contours of the REI and electrode as well as the weld pool geometry were extracted from the image with a developed, robust algorithm, and the arc length was calculated with welding voltage. The offset distance and deflection angle of the welding torch relative to the correct position and attitude were calculated by inputting the extracted parameters into the REI-TPA model. The computational result was compared to the experimental data. The result showed that the model is correct and the monitoring of the welding torch with the REI-TPA model is available. The REITPA model can be applied to real-time control of TPA, which is a supplement to the application of the weld passive visual image and an extension of multiinformation acquisition and processing methods in the welding process.

An approach to robot welding path autonomous planning of the intersection weldment based on 3D visual perception

To improve the accuracy, an approach to robot welding path planning of the intersection weldment based on 3D visual perception is proposed. It adopts the two-stage location scheme of “global 3D reconstruction + local scanning correction”. First, this paper proposes an improved K-means clustering method based on the geometric features of workpiece point-cloud, to achieve accurate and fast point-cloud segmentation. Second, the intersection parameters of workpiece can be quickly calculated by the proposed parameter identification method. Third, this paper plans the scanning path of laser scanner according to the identified parameters, and puts forward an algorithm of weld path points recognition combined with the actual weldments state. Then, the pose of robot welding torch is obtained by using spline fitting algorithm and welding torch attitude estimation algorithm. Finally, the experiments show the path planning error is about 0.3 mm, which has increased a lot than the published methods.

Monitoring Welding Torch Position and Posture Using Reversed Electrode Images – Part I: Establishment of the REI-TPA Model

Sensing, modeling, and control are the key technologies of intelligent welding manufacturing. The position and attitude of the welding torch relative to the weld seam affects the quality of the produced weld directly, which is the basis of control and offline programming of the welding robot. Based on the existing research of reversed electrode image (REI) on monitoring of weld pool surface and penetration state, this work focused on the application of REI on monitoring of welding torch position and attitude (TPA). In this paper, a REI-TPA model was established to quantitively relate REI to TPA by considering the surface of the weld pool as a spherical mirror. With the REI-TPA model, the offset distance and deflection angle of the welding torch relative to the correct position and attitude can be calculated. The calculation is based on the measurement of the relative distance between the tip of REI and the electrode in a passive visual image of the weld pool, arc length, and weld pool geometry. This model can be applied to the real-time control of TPA, which is a supplement to the application of welding passive visual image and an extension to multi-information acquisition and processing methods in the robotic welding process.

Welding motion synchronization of tank with variable curvature section based on discrete planning method of welding torch posture

Welding motion synchronization of tank with variable curvature section based on discrete planning method of welding torch posture

Comparative study between TIG-MIG hybrid and MIG welding of 1.4462 duplex steel joints

Duplex steels are used for applications that require high strength and ductility combined with good corrosion resistance. An economical welding technology to handle these steels is achieved by combining the MIG and TIG arc processes. The aim is to improve welding speed and quality by utilizing a TIG-MIG hybrid welding process to join 1.4462 duplex steel with a thickness of 2 mm. The interaction between the two arcs, caused by the blowing effect, is an enormous challenge that can be counteracted with a defined torch position and current modulation. For this purpose, a variation of the MIG (pulsed and AC pulsed arc) and TIG process (AC and pulsed DC) took place. The influence of electrical parameters on process stability and material transfer was investigated. For analysis, an evaluation of high-speed recordings (5000 frames per second) and synchronized measured current/voltage curves (200 kHz) is carried out. Based on a number of selected specimens, a welding procedure test according to ISO 15614-1 is performed to determine the welding seam quality. The test includes the characterization by tensile and hardness testing and macroscopic and microscopic examination. Additionally, the specimens are examined according to ISO 5817.

Influence of process parameters on bead geometry and its effect on mechanical properties of CMT welding of automotive grade steel and aluminium alloy using aluminium based filler wire

This investigation aims to examine the effectiveness of torch position, welding-brazing parameters on the embedded bead profile and load carrying potential of the brazed joint of zinc coated DP600 steel and Al 5052 joined by cold metal transfer (CMT) technique. The base metals were joined at different torch position (−0.6, 0 and 0.6 mm) in lap joint position using Al-based filler wire. At different wire feed rate (WFR) 3, 4 and 5 m/min changes in bead shape and its geometry were observed. The various modes of failure were classified based on effective bonding length (LH–LV) and LH/θ ratio. The best combination of welding-brazing parameters at which the maximum load bearing capacity of 4.1 kN and enhanced bead properties was achieved at 0.6 mm torch position and WFR 5 m/min. The intermetallic compound layers formed during the process affect the tensile properties of weld-brazed joint. The possible intermetallics and the presence of major elements in intermetallic layer were analyzed by energy-dispersive X-ray spectroscopic analysis. Furthermore, in this investigation, it was also observed that the thickness of IMC layer increases with the increasing WFR and heat input up to a critical value of 10 µm.

A novel welding path generation method for robotic multi-layer multi-pass welding based on weld seam feature point

Traditional “teach and playback” mode limits the efficiency and adaptability of robotic multi-layer multi-pass (MLMP) welding. The tracking solely based on the seam points may result in an unstable welding process with bad filling quality. In this paper, a novel welding path generation method for MLMP weld based on seam feature points is proposed. The 3D weld reconstruction is realized during the welding torch round-trip movement in the MLMP welding process. The FPLDN network is proposed to detect the seam feature points for each welding pass. To achieve accurate key direction vector estimation, an adaptive weighted PCA-based normal estimation method and an improved RANSAC method are used for weld segmentation and fitting. Then, the welding torch position and posture can be estimated in the nearest neighbor of seam feature points with further smoothing and interpolating. In the experiment, this method showed better performance in precision and stability than traditional methods with the root mean square error (RMSE) less than 0.771 mm.

Improved whole rock low detection limit gold analysis by LA-ICP-MS utilizing pressed-powder-pellets

Analysis of Au in geological materials has been proven useful for understanding geological processes related to the formation of various Au-rich ore deposits. However, the Au concentration in the related source rocks is extremely low (∼<1 ng g−1) and the methodologies allowing analysis at sub-ng g−1 levels are time-consuming, costly and generally involve the handling of hazardous chemicals. Here we present an improved method for low Au concentration analysis by laser-ablation inductively-coupled-plasma mass-spectrometry (LA-ICP-MS) of pressed-powder-pellets (PPP). Fine instrumental tuning for key parameters such as ICP-MS sample gas flow, torch position, RF power, laser frequency, ablation style and laser gas flow allows increasing the Au sensitivity while keeping oxide production low. The latter is critical when analyzing low Au concentrations as the ICP-MS analysis can be impaired by 181Ta16O and 180Hf16O1H interferences. Reducing oxide production and quantifying interferences by analyses of matrix-matched Ta- and Hf-doped pellets, allow for efficient corrections. The method improves the method limit of detection with values as low as 0.10–0.05 ng g−1 Au and routine analysis of reference materials shows that Au analysis by PPP-LA-ICP-MS is reliable. This contribution highlights that the PPP-LA-ICP-MS method is suitable for investigating Au distribution and behavior in Au-depleted rocks.

Development of in-process welding torch position control system using AI technology

Development of in-process welding torch position control system using AI technology

A novel seam extraction and path planning method for robotic welding of medium-thickness plate structural parts based on 3D vision

Currently, the robotic welding of medium-thickness plate structural parts has become a common welding application. With the rapid development of automation technology and robotics, the traditional teaching-playback mode and the off-line programming mode cannot meet the automation demand of welding robots. To realize automatic seam extraction and path planning for robotic welding of medium-thickness plate structural parts without programming and teaching, we use three models of medium-thickness plate structural parts as the research objects to propose a novel seam extraction and path planning method for robotic welding of medium-thickness plate structural parts based on 3D vision. Firstly, a set of improved RANSAC multiplanes fitting algorithms is proposed to accurately obtain the position of the intersection lines between the intersecting planes of the point cloud model. On this basis, we combine the geometric features of three models to propose the specific welding seam extraction methods respectively. Then, according to the spatial structure of the welding seams and the welding process, we carry out the welding path planning. Finally, a welding pose planning method based on the dihedral structure is proposed. Experiment results show that the proposed method can well realize the welding seam extraction, welding path and posture planning of medium-thickness plate structural parts without programming and teaching. • We propose specific welding seam extraction methods for different models. • We propose a welding path planning method according to the spatial structure of the welding seams and the welding process. • A welding posture planning method based on the dihedral structure is proposed to realize the automatic planning of welding torch posture. • We use real experimental data to evaluate the performance of the proposed method and compare it with the existing method to illustrate its effectiveness.

Visual sensing and quality control in plasma MIG welding

By generating a complementary effect of each weld in the welding process, a hybrid welding can improve the welding efficiency while ensuring the welding quality. The combination of plasma arc welding (PAW) with high current density and metal inert gas (MIG) welding utilizing consumable electrodes is available to perform one-pass welding for the thick plate. The plasma torch works for keyhole welding with deep penetration, and the MIG torch works for a build-up welding to form a surface bead. However, due to the complexity and particularity of the two-electrode system, it is still difficult to achieve a high-quality automatic welding. In this study, the authors have observed the weld zone with a complementary metal oxide semiconductor (CMOS) camera, and analyzed the regulation of image features changing with the torch position. Control strategy of the welding torch and image processing to realize the seam tracking and standoff have been proposed. Utilizing a high-speed video camera, system configuration and welding conditions have been determined with the welding images of the arc behavior and droplet transfer. The authors have investigated the corresponding welding conditions when the welding defects occurred. In addition, we have modified the power source with an invertor control and designed a characteristic curve for the power source to stabilize welding conditions and enhance the MIG arc length self-regulation. The performance of welding system for the seam tracking and standoff control is effective in the real-time welding experiment. The power source with an invertor control and the designed characteristic curve can optimize the welding conditions and acquire good welding results. The study has achieved a high-quality welding under the condition of automatic plasma MIG welding.

Seam tracking system based on laser vision and CGAN for robotic multi-layer and multi-pass MAG welding

A robotic seam tracking system based on laser vision and conditional generative adversarial networks (CGAN) was proposed to address the problem of low welding precision for the multi-layer and multi-pass MAG welding process. The seam tracking system consisted of three modules, i.e., laser-vision (LV), server-terminal (ST), and robot-terminal (RT), and the real-time seam tracking for multi-layer and multi-pass welding was realized though the seam feature points extraction, coordinate conversion, deviation calculation and welding torch position correction based on the KUKA robot sensor interface (RSI). Experimental results showed that the proposed restoration and extraction network (REN) based on the CGAN principle could not only restore the seam feature information but also extract the seam feature points accurately. The welding torch could run smoothly in the strong noise environment, and there were no obvious correction marks in the weld appearance. The average correction error was less than 0.6 mm, and the adjustment process of the welding torch position can be completed within 1 s, indicating that the accuracy and speed of the proposed seam tracking system were acceptable.

Development of In-process Welding Torch Position Control System using AI Technology

Development of In-process Welding Torch Position Control System using AI Technology

A novel 8-shape trajectory weaving welding control algorithm with auto-adjust welding torch attitude

A novel 8-shape trajectory weaving welding control algorithm with auto-adjust welding torch attitude

A real-time method for detecting weld deviation of corrugated plate fillet weld by laser vision sensor

In the process of arc welding of the corrugated plate fillet weld, both the modification of weld position and the change of welding torch attitude are required. In general, it is difficult to accurately detect the weld position with the advanced weld detection method, and there is short of real-time in advanced weld detection. In this paper, a unique new sensor and detection method were proposed. The laser vision sensor mainly includes a camera and two circular spot laser light sources. The two laser light sources are separately fixed at two sides of the welding torch clamping piece. The axes of the two laser sources and the axis of the welding torch are parallel and coplanar, and the laser spots on both sides of corrugated plate fillet weld are symmetrically distributed on both sides of welding point. When the welding torch moves horizontally or vertically, the image position of the two laser spots in the video camera will change. Through analysis and calculation, the direction of the welding torch migration was determined, and the offset was calculated to realize the real-time detection of the position of the corrugated plate fillet weld. The experimental results showed that when the welding torch moved ±4.5 mm horizontally or vertically, the detection accuracy of the weld was 0.5 mm.

Rapid unseparated rare earth element analyses by isotope dilution multicollector inductively coupled plasma mass spectrometry (ID-MC-ICP-MS)

We present a method for analyzing rare earth elements (REEs) by isotope dilution without separation of individual elements. Utilizing a Nu Plasma 2 multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS) equipped with an Aridus II desolvation nebulizer, sample introduction tuning parameters (torch position, gas flows) were investigated and used to minimize oxide formation (e.g., NdO/Nd <0.05%) and obviate the need to analyze the REEs as separated “cuts.” Ratios for spike isotopes relative to reference in mixed elemental standards containing varying amounts of Ce, Nd, Sm, Eu, Gd, Dy, Er, and Yb were measured accurately within 1% of IUPAC values. La and Lu in the standards deviated more than 2% from expected values due to more pronounced interferences reducing the efficacy of corrections. A USGS (United States Geological Survey) BCR-2 rock standard was also processed with flux fusion, iron coprecipitation and bulk REE separation by a single column pass followed by analysis. The concentrations for Ce, Nd, Sm, Eu, Dy, Er, and Yb fell within 2% of consensus values. A USGS BIR-1A rock standard was also processed in triplicate by hydrofluoric and nitric acid digestion followed by iron coprecipitation and a single ion exchange column pass, yielding rare earth concentrations within 3% of consensus values with 0.3% relative standard deviation (n = 3). This demonstrates the ability to produce high quality REE patterns of comparable quality to traditional methods which require labor and time intensive REE separation, but with sample preparation and analytical times that are comparable to isotope dilution analyses by single-collector ICP-MS.

Experimental study of welding torch positioning parameters influence on overlap joint formation

The article presents the experimental results demonstrating the influence of welding torch positioning parameters on the overlap joint formation. Effect of welding torch tilt angle and its displacement relative to joint and lap joint assembly gap on joint formation quality was evaluated. The general recommendations for choosing the welding torch positioning parameters depending on joint gap size were established.

A novel field box girder welding robot and realization of all-position welding process based on visual servoing

Abstract Box-type steel structure has been widely applied in the field of buildings and bridges because of its unique advantages. However, there are still many problems in field welding that need to be solved. In order to improve the level of automation and intellectualization in field welding of box girder, a new type of on-site all-position welding robot system is developed and designed in this paper. The convenience of on-site installation and debugging of the robot is realized by the scheme of permanent magnet adsorption and straight-arc combined track. The motion matching scheme of bilateral wheel-axle clamping makes the circumferential movement of the robot much smoother and more stable which makes the system with better overall force characteristics and load-carrying capacity. Then, a novel visual sensor based on combined laser structured lights is proposed and designed, which can realize several functions such as groove parameters detection, welding joint tracking and torch posture detection in field welding based on single detection image, so as to effectively improve the flexibility and intelligence of field welding robot. After that, based on the designed visual sensor and welding robot system, a visual servo-control system based on Visual Studio platform is established. Through the effective integration of detection image reading, image processing and calculation, image feature parameters transmission, motion control board call and feedback control signal output, the adjustment and control of welding torch's position and posture based on visual servo-control are realized. Furthermore, based on the kinematics calculation and the welding process requirements of the box girder, the welding process design is planned for the all-position welding of the box steel girder, which solved the technical problem of the rectangular fillet welding in the box steel butt welding (the welding torch position and posture transition control in right-angled corner of girth butt joint). Finally, all-position welding experiments of box steel girder were carried out. The results show that the welding robot based on visual servo-control can realize better control of weld formation in all-position welding of box steel girder.

Robotic seam tracking system based on vision sensing and human-machine interaction for multi-pass MAG welding

Abstract In the seam tracking for the metal active gas (MAG) welding of heavy plate, there are many problems, such as the strong arc light due to the large current, spatter and fumes, the losses of centerline information and complex conditions in groove induced by previous passes, etc. The problems often make the characteristic in the images needed for seam tracking indistinct and make it difficult for industrial robots to correct the deviation of multi-pass welding. Regarding this issue, a robotic seam tracking system based on vision sensing and human-machine interaction for the multi-pass MAG welding was proposed. The groove edges were used as reference to tell the deviation and to control it according to a simple, fast and effective control strategy based on human-machine interaction. The deviation could be judged by comparing the left or right groove edge alternatively with the corresponding specified positioning ruler from the real-time images obtained by industrial camera. The operators could adjust the torch position in real time by the hint on the positioning ruler, which followed the control strategy. The accuracy, response rate and smoothness of the system were verified by reasonable path planning in multi-pass MAG welding. By comparing the deviation correction of robot with the actual deviation of weld seam, the accuracy of system was rated, which had an average error less than 0.5 mm and was acceptable. The comparison between the actual weld height and width after correction and the designed height and width showed that the system worked smoothly and steadily and the system could track the weld in real time.