38 humps, 1 stroke, 3.5 seconds: Welding saw chain swords in rapid traverse - Electro-pneumatic welding drive for high welding quality
Husqvarna is one of the leading manufacturers of power tools for forestry, gardening and landscaping. Chainsaws have been an integral part of the product portfolio since 1959 and are widely recognised for their quality. In order to optimise the production of guide bars and saw chain swords, DALEX developed an automated special gantry welding system in DC design. It joins the individual parts of the guide bar with 38 welding projections in one stroke in just 3.5 seconds!
Felling, limbing, sawing, cutting firewood, pruning trees and more - with its easy-to-use, reliable and robust chainsaws, Husqvarna offers professionals and amateurs alike excellent tools for their forestry and gardening work. To ensure that the chainsaws deliver what Husqvarna promises, high-quality components are the be-all and end-all. One example is the guide bars, also known as saw chain guide bars. They play a decisive role in the functionality of chainsaws and ensure precise guidance of the saw chain while minimising friction. This makes them the crucial link for efficiently transferring the engine's power to the wood via the chain. The drive links of the chain run over the circumferential groove of the bar. However, as some might suspect, the groove is not milled into the bar, but is created by welding two outer plates to a smaller central plate. Husqvarna brought DALEX on board to complete this welding task economically and automatically.
"The task was to automatically join the three-layer guide rails with nominal lengths between 10 and 24 inches using projection welding. On the one hand, short cycle times were required to ensure high productivity. And secondly, with such a crucial component, the quality of the welded joint must of course be of the highest standard so that the three layers of sheet metal are firmly and securely joined together," says Christoph Desch, Sales Manager at DALEX Automation & Welding GmbH, describing the requirements. "In order for the systems to deliver such top performance, they must be precisely customised to the respective requirements. That's why our technical sales experts provided close support and advice for the Husqvarna project right from the start. In close dialogue with Husqvarna, we developed a tailor-made solution." The result is an automated, very large special gantry welding system in DC design, which was perfectly integrated into the workflow at Husqvarna in collaboration with a Swedish special machine manufacturer.
In seconds and with high quality
The automated projection welding system was designed with the electro-pneumatic drive developed by DALEX via air actuators with a maximum force of 250 kN at 6 bar. An on-site handling robot inserts the stacked guide rails into the appropriate mould for the different lengths in the welding system. "The large DC welding machine is designed for high outputs with a very long duty cycle. It welds the 38 projections to join the three sheets into a three-layer guide rail in a single stroke - in just 3.5 seconds, including raising and lowering the tools. The entire automated process, including feeding the individual parts, is completed in around 5 seconds," says Christoph Desch enthusiastically. After welding, the finished components are removed by a robot and thermally post-treated in a hardening furnace for stabilisation.
To guarantee a consistently high quality of the welded joint, DALEX uses the electro-pneumatic welding drive (EPS) developed in-house. Christoph Desch explains: "A good indicator of the welding quality in resistance welding is the force level during the current flow. The more evenly the force is applied during welding, the better the parts join. Thanks to the excellent repositioning behaviour - with practically no time delay - our EPS drive enables an almost constant and effective welding force to be achieved throughout the entire weld. In addition, the welding electrodes can be precisely adjusted and placed on the workpiece gently and without impact. These fast and dynamic properties guarantee excellent welding quality." The EPS also scores points for its low energy consumption, low noise levels and reduced wear.
Put through its paces
In order to rule out errors from the outset, determine optimum process parameters and ensure transferability to production, DALEX carried out test welds under realistic conditions at its in-house technology centre in advance - as the perfect complement to the welding technology consultation. The welding experts also put the entire system through its paces again before it was transported to Sweden and finally commissioned on site to ensure that everything worked reliably.
With the T-Center, DALEX is excellently equipped for such early tests, as it has access to welding guns connected ready for operation as well as spot, projection and roller seam welding machines in AC, medium frequency and KE technology. Thanks to various welding control systems from well-known manufacturers, the experts can demonstrate the differences and select the best system and the right machine configuration for the task. They are also able to create improvised welding tools in order to achieve optimum welding results with these auxiliary welding tools.
DALEX uses special measurement technology to analyse the systems and welding processes. This allows faults to be identified and rectified quickly and easily, particularly in fully and semi-automated processes. Modern high-frequency video systems, for example, are used for diagnosis, commissioning and function monitoring of the sometimes extremely fast movement sequences in the complex systems. This enables DALEX to determine downtimes in motion sequences and thus reduce cycle times. "We can also metallographically analyse and verify the quality of the welded joints using state-of-the-art measuring and micrograph technology," adds Christoph Desch.
Conclusion
The automated customised gantry welding system from DALEX allows Husqvarna to manufacture its guide rails for its chainsaws with the highest quality and efficiency. With this project, DALEX has once again impressively demonstrated its expertise not only in welding technology, but also in automation solutions and process optimisation. The customised system will undoubtedly contribute to the continued
Photo 1: The automated special gantry welding system in DC design for the automated production of three-layer Husqvarna guide bars or saw chain swords in various lengths.
Photo 2: The system is designed as a portal welding system in three-phase direct current technology with an electro-pneumatic drive developed by DALEX via air actuators, max. force 250 kN at 6 bar.
Photo 3: An on-site handling robot inserts the stacked guide rails into the appropriate tool for the different lengths in the welding system.
Photo 4: The welding of 38 welding projections takes place in one stroke, and the 3 sheets are joined to form a three-layer guide rail in 3.5 seconds.
Photo 5: After welding, thermal post-treatment takes place in a hardening furnace for stabilisation. (Above: hardened saw chain bar, below: unhardened).
Photos: DALEX Automation & Welding GmbH