The submerged-arc welding process is nothing new in itself – it is an established technique for achieving high quality welded seams during production of large components. What makes the system developed by Richter in conjunction with NUM special is the combination of various machine components available on the market and their perfect interaction based on a CNC and a specially developed application. This results in consistently high welded seam quality far beyond the quality achieved by normal methods.
Together with the wire and powder feed, the welding head of a submerged-arc welding system was fitted on a horizontally moving cantilever arm that can be swivelled in all directions and adjusted vertically. This means that the welding head can be positioned at any point above the welding table. The cantilever arm also incorporates the system’s control unit consisting of an FS152 monitor with function keys, a seat and a joystick. All commands and settings for the system, from set-up to work processing, are carried out using this joystick. Within the production process, this provides not only flexibility but also considerable ergonomic advantages; the welder can operate the machine wearing gloves, and the complex controls of the machine have been simplified to the extent that a new welder can operate it and work independently within the space of just a few hours. The simple controls and the connected controller have been developed carefully by technicians from Richter and NUM on site and perfected based on various practical tests. The commands given by the joystick are converted into movement by the Flexium CNC by means of 6 axes.
The workpiece to be machined is placed on a large 60-tonne rotary tilting table below the cantilever arm. As the name suggests, the table can turn endlessly, and can also be tilted to up to 45°, which allows welding of seams that are not horizontal. A further advantage of the swivelling cantilevered arm is that it can be pushed entirely to one side. This means that large components whose dimensions exceed that of the turntable can be welded.
Previously, submerged-arc welding systems normally welded V- or X-shaped seams that were always straight lines. Until now, the welding of contours always needed to be done by hand using other welding methods (MAG), which meant considerably more time and effort was involved, not least to avoid fluctuations in quality (formation of blowholes). This new submerged-arc welding system now allows contours to be welded automatically. This represents a real time saving with no compromise on quality. “Overall, the submerged-arc welding system developed here means that an increase in production performance in the region of 25 to 30% is altogether reasonable,” explains Dirk Kunig, Head of Electronics at Richter AG and developer of this system.
Nearly every day, the work preparation and welding monitoring departments of Richter AG find new applications for this system which would previously have been inconceivable. “There has been a real quantum leap in terms of performance and quality,” confirms Dirk Kunig.
The complex control of the system is handled by a Flexium 68 CNC unit from NUM, but this is not noticed by the user. The standard NUM HMI to operate the plant, which was supplied with the system, has been very much simplified by means of an application developed specially for this machine. It is controlled using a single joystick. The welder can use this joystick to map the welded seam to be created during the teaching process and at the same time read in the teach points.
At a later date, there are plans for the flame cutting system we reported extensively on in the last issue of NUMinfo to transfer the teach points to the submerged-arc welding system digitally, thus completely obviating the need for manual loading by the welders. This would save even more time. As can be seen on the monitor, the menu items are arranged so that they can be selected using the joystick. The arrangement of the bottom buttons and colours on the monitor corresponds to the arrangement of the buttons on the joystick, which can be used to switch between different menu items or levels.
In the background, the CNC governs the position of the welding head producing the welded seam, while a second CNC channel controls the wire advance and rotational movement of the powder-coating unit, so that it always precedes the course of the welded seam. Even components made of different materials, such as thick steel sheets and heavy cast components, can be welded perfectly, without errors and with the required level of precision. Such large-scale components made of different materials are required for massive digger arms in the mining sector.
With this new submerged-arc welding system, Richter Maschinenfabrik AG, in close cooperation with NUM, has taken a major step towards improved quality for welded seams, faster and more time-saving welding and significant reduction of production costs for submerged-arc welding. Once more, it has been shown that if two companies share their know-how in order to create something new, it is possible to successfully exceed expectations.