2008-05-12 - ABB has developed a software tool, VIrtualArc, that provides programmers and process engineers with a rapid, yet detailed, evaluation of a weld. The reduced need for test runs cuts costs while optimizing productivity and quality.
A human welder draws on experience and intuition in choosing the correct welding technique and settings, but a robot welder must be instructed in every detail of the procedure. Despite the availability of considerable theoretical knowledge, a series of test runs is often required to determine the correct settings. Such runs waste test materials and block robots that could otherwise be involved in revenue-generating activity. The costs and time involved mean that the number of test scenarios must be limited and the optimum setting can easily be missed. ABB has developed VirtualArc®, a software tool that enables programmers and process engineers to reliably determine the result of a weld. It permits a rapid, yet detailed, evaluation of various scenarios, reducing the need for and cost of numerous test runs while optimizing productivity and quality.
For many years, welding using the MIG/MAG process has been considered something of a “black” art. Most people know that welding is the process of joining two metal parts together, but very few understand the parameters involved and their bearing on the result. This ambiguity confuses experts as well as ordinary people. It is said that when 10 welding engineers or welders are asked how a given task should be approached, 10 different parameter settings are suggested – all of them achieving the same result.
The MIG/MAG process is very complex. To fully understand the theory behind it requires in-depth knowledge of arc physics, fluid dynamics, material science, arc-electrode interaction and more. Few people in the world have this knowledge, and of those that do, it is unlikely that any have any practical, hands-on welding experience. But many very skilled welders in the industry perform perfect welds without any special knowledge of arc physics and the science behind it. Their choices are guided by a feeling for the process itself. Unfortunately, with retirement, the number of such highly skilled welders will most certainly decrease, making it increasingly difficult for the welding industry to be successful.
Welding equipment suppliers must combine the science behind the MIG/MAG process with practical expertise. Welding must evolve from today’s black art to a modern fully controllable manufacturing process. The welding industry itself is interested in raising cost-efficiency by using simulation tools as much as possible for production optimization and planning. ABB has taken up the challenge of serving robot arc-welding customers by fulfilling these criteria.
ABB has developed a unique simulation tool, VirtualArc®, to meet the arc welding requirements of customers. VirtualArc® offers robot programmers, operators and welding engineers an expert system that provides in-depth analysis of the arc welding process, leading to improvements in process control, final welding quality and productivity.
The simulation tool incorporates state-of-the-art technology, facilitating prediction of the dominant phenomena in the weld. Implementation time and costs for automated processes are saved. The robust software package offers a user-friendly interface, which helps minimize process implementation time and reduces the costs of automated arc welding.
The technology behind the VirtualArc® software is based on the combination of arc physics, a self-consistent two-dimensional wire-arc work piece simulation tool, practical experience with arc welding and experimental results. The software consists of modules that are strongly inter-connected with the entire process system, including power source characteristics and connecting cables. Weld profile and quality predications are obtained using Bayesian neural network technology. Predictions from arc simulations and heat and mass transfer to the work piece are used as input to the neural network to predict weld quality and profile as well as defects.
VirtualArc® consists of modules with input pages with which the user enters data on the system parameters, the application and the weld process. The first page asks for information on the weld power source, gun, cables and wire feed system. The second asks for the materials, plate thickness, joint configuration, gap, weld geometry and weld class (B, C or D). The third asks for details of the wire and gas specifications and whether a short arc, spray arc or rapid arc will be employed. Armed with this data, the software then undertakes a pre-weld analysis using a Bayesian neural network tool. A further page graphically displays the predictions from the analysis of the weld parameters, the weld profile and the required or default speeds and torch angles. The user can inspect time graphs of current and voltage and a cross section of the weld. The latter shows the depth of weld penetration and profile, enabling the user to assess the quality and, knowing the speed, estimate the productivity of the process. Entering the relevant data takes only a few minutes. The analysis is completed in seconds.
VirtualArc® enables significant time-saving by eliminating the need for live weld test runs and the subsequent sectioning of the weld for inspection. In addition to costing time, such live test runs consume components and materials and remove valuable robots from the production
process. VirtualArc® also allows rapid appraisal of “what if” scenarios. In just a few seconds, the effect of different weld speeds and torch angles can be evaluated, making it easier to find
ways of improving productivity and/or weld quality. In addition, there are cost and investment pages that enable the user to accurately and rapidly determine expenditure and justify the application before welding is undertaken. Whenever software replaces testing, the validity of the results is in question. Comparison of VirtualArc® predictions with test welding data shows that the simulated weld profile is extremely close to its real weld counterpart.
Featuring an easy-to-use software interface, VirtualArc® can be operated from a single PC or laptop. It provides users with efficient offline welding process tuning that predicts a wide range of results, including weld shape and penetration, weld quality and possible welding defects. Predicting such results brings substantial benefits, including shorter implementation time, optimized welding productivity and quality and well-documented welding procedures. In turn these considerations contribute to lower production costs. As well as saving time and money through better production, VirtualArc® is also an efficient training tool for robot operators, programmers and production/welding engineers and an excellent platform for retrieving and storing arc welding process information for future developments. VirtualArc® is also useful for comparing different weld procedures in cost per meter of weld.
RobotStudio is used to define and create robot programs offline without requiring any real robots to be diverted from their productive activities, and VirtualArc® is used to evaluate and set welding parameters. Both tools eliminate risk and shorten the production time for new programs while maintaining plant productivity.
Program offline with RobotStudio
ABB’s RobotStudio software is a tool for simulating the movement of robot arms. Traditionally, robot programming is performed by manually moving the arm of a real production robot through a series of reference positions, which are then recorded. This implies a production break for the robot – a costly and inefficient use of a valuable asset.
RobotStudio offers an alternative by allowing the program to be created on a virtual robot – one that exists only as a model inside the computer. This robot has exactly the same spatial and dynamic properties as the real robot and is controlled by the same program. RobotStudio models the robot in a virtual 3D environment so that potential collisions or spatial constraints can be recognized. This prevents unpleasant surprises or damage on the real production line later.
RobotStudio can also be used to compare alternative setups or to train staff. By reducing programming costs and downtime for production lines, the software helps customers achieve higher utilization and productivity on their production lines.