Welding Guns Research Articles

Narrow gap welding seam deflection correction study based on passive vision

PurposeThe purpose of this study is to establish a method for accurately extracting torch and seam features. This will improve the quality of narrow gap welding. An adaptive deflection correction system based on passive light vision sensors was designed using the Halcon software from MVtec Germany as a platform.Design/methodology/approachThis paper proposes an adaptive correction system for welding guns and seams divided into image calibration and feature extraction. In the image calibration method, the field of view distortion because of the position of the camera is resolved using image calibration techniques. In the feature extraction method, clear features of the weld gun and weld seam are accurately extracted after processing using algorithms such as impact filtering, subpixel (XLD), Gaussian Laplacian and sense region for the weld gun and weld seam. The gun and weld seam centers are accurately fitted using least squares. After calculating the deviation values, the error values are monitored, and error correction is achieved by programmable logic controller (PLC) control. Finally, experimental verification and analysis of the tracking errors are carried out.FindingsThe results show that the system achieves great results in dealing with camera aberrations. Weld gun features can be effectively and accurately identified. The difference between a scratch and a weld is effectively distinguished. The system accurately detects the center features of the torch and weld and controls the correction error to within 0.3mm.Originality/valueAn adaptive correction system based on a passive light vision sensor is designed which corrects the field-of-view distortion caused by the camera’s position deviation. Differences in features between scratches and welds are distinguished, and image features are effectively extracted. The final system weld error is controlled to 0.3 mm.

Benchmark for welding gun fault prediction with multivariate time series data

In the automotive industry, machinery failures of the resistance spot welding (RSW) guns would interrupt the manufacturing lines and cause unplanned downtime, potentially resulting in a significant loss of production and reliability. Predicting the machinery failures of the RSW gun can provide more scientific strategies for predictive maintenance and decision-making. However, fault prediction of RSW guns has become increasingly challenging due to their complex behavior and data variability. In this paper, we created a benchmark dataset and proposed welding gun fault prediction benchmarks to aid in the development of machine learning approaches toward welding gun fault prediction. The dataset was collected at the Body-Shop (BS) of BMW Brilliance Automotive Ltd. from different components of hundreds of RSW guns to capture the patterns and trends before welding errors with historical data. Then we provide state-of-the-art machine learning (ML) benchmarks on time series forecasting methods in a welding gun fault prediction use case. This study will provide insights for time series forecasting while enabling ML researchers to contribute towards the fault prediction of the RSW guns.

Controlling deformation and residual stresses in a TIG joint for Invar steel molds

Invar steel is used to produce molds for composite materials for its thermal expansion coefficient similarity to those materials. These molds show wear resistance, provide good dimensional accuracy of produced parts, and they are produced with tungsten inert gas (TIG) welding. In this study, welding deformation and residual stress optimization of an Invar steel TIG welded butt joint were studied experimentally and numerically. Results show that deformation can be controlled effectively with the appropriate welding sequence from both sides to the middle of the joint when compared to sequential welding. When double welding guns are used to weld concurrently from both ends along the same welding path in segmental welding, deformation developed is minimum, while deformation increases significantly at the weld segmental area. When segmental bidirectional welding is used, deformation is slightly increased, but the highest deformation area can be avoided compared to segmental unidirectional welding, and residual stresses can be improved. The equivalent stresses were reduced following heat treatment, and especially stress concentration in the weld, with optimal values reached for heat treatment at 420 °C.

Incipient Wear Detection of Welding Gun Secondary Circuit by Virtual Resistance Sensor Using Mahalanobis Distance

Wear of the secondary of the welding gun, caused by mechanical fatigue or due to a bad parameterization of the welding points, causes an increase in quality problems such as non-existent welds or a reduced weld nugget size. In addition to quality problems, this defect causes production stoppages that affect the final cost of the manufactured part. Different studies have focused on evaluating the importance of different welding parameters, such as current, in the final quality of the welding nugget. However, few studies have focused on preventing weld command parameters from degrading or changing. This investigation seeks to determine the wear of the secondary circuit to avoid variability in the current supplied to the welding point caused by this defect and the increase in circuit resistance, especially in industrial environments. In this work, a virtual sensor is developed to estimate the resistance of the welding arm based on previous research, which has shown the possibility of detecting secondary wear by analysing the duty cycle of the power circuit. From the data of the virtual sensor, an anomaly detection method based on the Mahalanobis distance is developed. Finally, an integral system for detecting secondary wear of welding guns in real production lines is presented. This system establishes performance thresholds based on the analysis of the Mahalanobis distance distribution, allowing monitoring of the secondary circuit wear condition after each welding cycle. The results obtained show how the system can detect incipient wear in welding guns, regardless of which part of the secondary the wear occurs, improving decision-making and reducing quality problems.

Joining of ultra-high-strength steels using resistance element welding on conventional resistance spot welding guns

Single-step joining of dissimilar material combinations between ultra-high-strength steels and high-strength aluminium alloys with sufficient mechanical joint properties by using conventional resistance spot welding equipment has not been reported yet. In this research paper, a novel single-step joining technology, so-called self-penetrating resistance element welding, is introduced. First, the motivation for this novel joining technology, the state of the art in joining, and the process characteristics are presented. In the results section, the welding rivet geometry is first determined using forming simulations and validated by head tensile tests. Followed by the description of the welding process and its characteristics, the mechanical joint properties are reported. The results show that a numerically optimised welding rivet geometry can guarantee sufficient joint strength. By this welding rivet geometry, a thermally assisted penetration of aluminium and therefore welding to steel is possible with and without adhesive. Furthermore, it is shown that the welding process can be designed by means of simulations. Finally, the shear tensile tests prove that an overall sufficient joint strength is ensured.

Joining of Thermoplastic Composites with Metals Using Resistance Element Welding

Joining is a key enabler for a successful application of thermoplastic composites (TPC) in future multi-material systems. To use joining technologies, such as resistance welding for composite-metal joints, auxiliary joining elements (weld inserts) can be integrated into the composite and used as an interface. The authors pursue the approach of embedding metal weld inserts in TPC during compression moulding without fibre damage. The technology is based on the concept of moulding holes by a pin and simultaneously placing the weld insert in the moulded hole. Subsequently, the composite component can be joined with metal structures using conventional spot welding guns. For this purpose, two different types of weld inserts were embedded in glass fibre reinforced polypropylene sheets and then welded to steel sheets. A simulation of the welding process determined suitable welding parameters. The quality of the joints was analysed by microsections before and after the welding process. In addition, the joint strength was evaluated by chisel tests as well as single-lap shear tests for the different weld insert designs. It could be shown that high-quality joints can be achieved by using the innovative technology and that the load-bearing capacity is significantly influenced by the weld inserts head design.

SUITABLE PRODUCTION TOOLS SELECTION WITH THE USE OF EVOLUTIONARY ALGORITHMS

This paper deals with the use of a production equipment simulation in the design of production systems, more specifically the welding equipment in the automotive industry. Based on the simulation results, a matrix, which defines the possibility of using given manufacturing tools (in this case welding guns are considered) to connect the plates using the electrical resistance spot welding process, is created. This matrix generates a set of several numbers of solutions depending on other parameters, such as the lowest price, the lowest number of used welding guns, etc. The goal is to solve this task. The solution is presented using mathematical programming. Specifically, the method of genetic evolutionary algorithms is being used. The Solver software is used to optimize the selection of the welding guns’ combination. The Solver is an add-on in MS Excel. The case study shows 15 welding points weldment on which the availability of 20 types of welding guns was simulated. The result is an ideal combination of 2 types of guns for the lowest price.

Mitigation Solutions for the Magnetic Field Produced by MFDC Spot Welding Guns

Among the different welding technologies, portable welding guns are one of the most critical devices in relation to human exposure to electromagnetic fields. This paper focuses on medium frequency (MF) direct current guns proposing two actions aimed to the mitigation of the magnetic field generated during the welding process. The first action consists in the adoption of a passive shield for the on-board MF transformer. The analysis points out that the transformer alone produces a magnetic field that can exceed the prescribed limits. Therefore, a suitable mitigation system is identified. The second action aims to mitigate the predominant magnetic field that is generated by the electrodes of the welding gun. The analysis of the field waveforms shows that the rise time of the welding current pulse is the main parameter affecting the exposure index. The effect of the increase of the rise time is investigated through experimental and numerical analyses. The results prove that a small increase of the rise time causes a significant reduction of the exposure level. It is noteworthy that the two mitigation actions can be adopted on both existing and newly developed welding guns as they do not require any structural modification of the welding device.

How Safe Are Spot Welding Guns to Use?: An Analysis of Occupational Exposure to Their Magnetic Field

This article evaluates the exposure of workers to the magnetic field produced by several resistance spot welding (RSW) guns, taking into account both ac and medium-frequency dc (MF dc) technologies. First, magnetic field measurements were performed in the laboratory. The results made it possible to define a safety area where exposure limits were not exceeded. Dosimetric assessments were also performed in line with the current regulatory framework. The analysis showed that the exposure limit values were not exceeded, even when the operator was outside the previously defined safety area.

Identification of the space posture of arc welding guns with rotational arc sensors in GMAW

In order to improve welding quality and welding efficiency of the rectangular fillet weld in the shipbuilding industry, it is necessary to identify the space posture of the arc welding gun accurately. The mathematical model of the space posture of the arc welding gun has been established, and the space posture can be determined by four variables. Within a certain range, the mathematical model about the relationship between the welding current and the wire extension has been established in GMAW, and the height deviation that the arc welding gun is relative to fillet weld can be calculated by this mathematical model. In order to accurately calculate the horizontal deviation and the inclination angle, the main analysis method has been studied. By using the designed algorithm, the rectangular fillet weld tracking experiment and the tensile experiment have been done in the laboratory and shipyard. Experimental results showed that the robot could identify the space posture of the arc welding gun accurately, and track rectangular fillet welds with high accuracy and good reliability.

IMPLEMENTATION OF ANALYTIC HIERARCHY PROCESS (AHP) AS A DECISION SUPPORT TOOL FOR SELECTION OF ROBOT FOR SPOT WELDING OPERATION

Flexible production lines are most essential for any lean manufacturing system for cost effectiveness. Automobile industry is extensively making use of lean manufacturing philosophy where reduction of waste is paramount importance without sacrificing the quality. Production of an automobile consists of number of phases in which fabrication of body by portable spot welding guns using robots is a significant stage. Robotic Spot welding operation is accomplished to manufacture the body of the automobile, because of its inherent accuracy and repeatability. Robot is a programmable machine which offers flexibility to switch over from one type of model of automobile to another type of model swiftly. But selection of an appropriate robot for the desired task to be accomplished is a crucial decision to be taken. Many factors are to be considered before arriving at an apt decision. Thescenario of this sort may be considered as multi-criteria decisionmaking (MCDM) problem. Though many techniques are available to solve problems of this type, Analytic Hierarchy Process (AHP) has been selected, because of its strong mathematical basis. In the present paper AHP is implemented to address this MCDM problem which acts as a decision support tool to select an appropriate robot for spot welding operation.

A technique for designing systems of electronic heating of cathodes of welding electron guns

A complex method for analyzing the processes in the systems of indirect cathode heating for electron- beam welding guns is proposed. The necessity of considering the electron-beam formation process in a cathode assembly with predetermined geometric characteristics is justified for calculating the distribution of the heat-flux density over the main-cathode surface. The typical distribution of the heat-flux density over the surface of the main cathode, which is heated via electron bombardment using a spiral wire heater, is analyzed. A method for calculating the temperature distribution over the structural elements of a typical cathode assembly is described, and the calculation results are analyzed. The influence of the nonuniformity of the electronbeam- current density distribution over the heated surface of the main cathode and the heat dissipation on the temperature and emission-current-density distributions on the working surface of the main cathode is considered. The advantages of the proposed method in comparison with existing idealized mathematical models and its suitability for solving problems of designing various electron guns are demonstrated.

A Simplified Procedure for the Exposure to the Magnetic Field Produced by Resistance Spot Welding Guns

This paper describes a simplified but effective methodology for the assessment of the human exposure to the magnetic field generated by resistance spot welding guns. The procedure makes it possible to compute the induced electric field in time domain as required by the standardized methodology for the assessment of pulsed magnetic fields (i.e., the weighted peak method). In this paper, we show that the proposed procedure provides results in accordance with a rigorous approach, allowing a huge reduction in the computational burden and, consequently, a significant speedup.

Assembling Variation Analysis Based on Power Balance Method for Sheet Metal Parts

Sheet metal parts are widely used in auto body and airplane body. As the method of influence coefficient cannot accurately analyze the relationship between part deviations and assembly variations, this paper proposes a new variation analysis model based on a method of power balance for sheet metal parts. The simple metal planes are loaded to fixtures according to the principle of “4-2-1”; and then variety of part deviations is analyzed during assembly process. The analysis shows that the welding guns do same work during welding process. Based on the above, this work establishes sensitive coefficient matrices between part deviations and assembly variations. Finally, two Z-shape sheet metal parts illustrate the assembling variation analysis process and the results indicate the accuracy of the method of power balance.

Reconfigurable fixture locating layout for compliant sheet metal welded assemblies subjected to welding force variations

Reconfigurable sheet metal fixtures are used to assemble sheet metal product families of similar locating layouts. These have to maintain locating and clamping layout fidelity for the entire range of a product family. Locating and clamping regions of a sheet metal part tend to dislocate and distort once subjected to nonequalized resistance spot welding guns. The resulted working regions are different in location and size from the original ones. In this article, Monte Carlo simulations are used by the authors to investigate the expected size and location of the working regions of parts in a sheet metal family subjected to random resistance spot welding forces. In the case study, proposed methodology is applied to an available automobile underbody floor panel family. Resulted working regions after the probabilistic deflection analysis are different from the initial ones both in size and location. The results show that by incorporating the random nonequalized clamping forces, the size of the working regions for fixturing elements is increased. Also, the possibility of designing a fixture that cannot assemble the full range of parts is reduced.

Research on the Application of 3G Robotic Welding Guns to the Welding of Body-in-White Based on Delmia

3G welding gun is a new kind of welding guns which uses servo motor as the driving device. And it is of modularity, simplicity, robustness and high performance and has obvious advantages compared with traditional welding guns. This paper exploited robot payload check program to make comparison of the differences between OBARA welding guns and 3G welding guns. The results verified the advantages of 3G welding guns. A case study to the application of 3G welding guns to the body side was conducted, and Delmia, a 3D platform for robotic simulation and OLP, was used to create the robot welding programs. Finally, the timing chart of welding process by means of 3G welding guns was analyzed.

Resistance Spot Welding Gun System Development Based on C# and Solidworks

In this paper, the type selection of resistance spot welding guns and 3D part drawings library are developed based on the C# programming software and Solidworks environment. It is called rswg-swc software system. The selection method of resistance spot welding guns is analyzed, 3D graphic library about the general parts and series parts of welding gun is established .Utilizing the user interface, input the necessary parameters to choose corresponding product model, product assembly drawings and part drawing are created in Solidworks.

Estimations of compatibility of supercapacitors for use as power sources for resistance welding guns

Supercapacitors offer potential for several kilojoules of energy to be proved in a small package with limited charge voltage (few volts). A preliminary examination of supercapacitors suggests that both the voltages used and retainable energies are well matched for resistance spot welding applications. Utilization of supercapacitors as resistance welding power supplies offers significant weight reduction over conventional (transformer and power supply) approaches, with subsequent economic advantages. In this work, some preliminary analyses have been done to assess the potential for using supercapacitors as resistance welding power supplies. This was done by integrating two separate analyses: one to assess the inductive response of specific weld gun designs and the second to define the current response of supercapacitors matched with that inductance. Results demonstrated potential for achieving desired currents and pulse widths with the proper selection of supercapacitor type and arrangement as well as secondary gun configuration. These analyses were further used to understand implications of system design on overall deliverable current capability. While the results described here only describe potential, some recommendations are made for next steps advancing supercapacitor-based resistance spot weld gun technology.

Assembling Variation Analysis Based on Power Balance Method for Sheet Metal Parts

Sheet metal parts are widely used in auto body and airplane body. As the method of influence coefficient cannot accurately analyze the relationship between part deviations and assembly variations, this paper proposes a new variation analysis model based on a method of power balance for sheet metal parts. The simple metal planes are loaded to fixtures according to the principle of “4-2-1”; and then variety of part deviations is analyzed during assembly process. The analysis shows that the welding guns do same work during welding process. Based on the above, this work establishes sensitive coefficient matrices between part deviations and assembly variations. Finally, two Z-shape sheet metal parts illustrate the assembling variation analysis process and the results indicate the accuracy of the method of power balance.

An examination of electric servo-guns for the resistance spot welding of complex stack-ups

In this program, the capabilities of medium-frequency direct current (MFDC) electric servo resistance welding guns for the welding of complex stack-ups were investigated. Capabilities of interest from these guns include the ability to apply forge forces and currents, as well as the ability to sequence the current and forging profiles. The complex stack-up under study included a 1-mm outside sheet attached to two 2-mm sheets. Work was done using design of experiment (DOE) techniques. The experiment included a range of processing variations deliverable from the MFDC servo-gun, as well as two electrode variations (materials and sizes). Heat balance during resistance welding of this stack-up was found to be dominated by the electrode variations. As electrode variations are not considered a solution for automotive complex stack-up applications, a best practice was defined from the DOE that included similar-sized class 2 electrodes. This best practice included short overall weld times, a moderate forge force, a significant (40 %) increase in current during forging, and a weld time relative to the forging portion of the weld schedule. This yielded nugget penetrations of roughly 50 % into the thin attached sheet. It was noted that, at these penetrations, indentations on both sides of the joint reached 0.45 mm and that process variations could be used to trade off penetrations with overall indentations.