The advantages of laser welding are well known to Esta Rohr, a company based in Siegen, Germany that produces longitudinal seam welded, stainless steel pipes using a 4.5kW CO2 Slab laser integrated within a Rofin profile welding system (PWS). Esta Rohr technical manager, Sven Pitzer takes up the story.
“The benefits for us are obvious. Compared with the traditional TIG-welding process, the laser is three times as fast. For example, we were welding tubes with dimensions of 18mm x 1mm with the conventional TIG-machine at 5.5m per minute. By comparison, the laser achieves 16m per minute, and it is not the power of the laser that restricts the speed, but the subsequent in line annealing unit”.
Another important factor is the PWS’ capability of welding both austenitic and ferritic stainless steels. When manufacturing stainless steel tubes, the process benefits of the laser allow precise control of parameters and therefore the energy used to create the weld along the full length of the tube.
Esta Rohr is not only convinced by the process benefits of laser welding. The laser also offers distinct advantages when it comes to system availability. Traditional TIG-welding requires regular electrode replacement, which inevitably introduces production delays. On the other hand, the laser alternative offers almost 100% availability.
With its integrated gap recognition, the PWS sensor technology adjusts for even the smallest deviation of the weld seam position, and optimum welding results are possible even under difficult conditions. The laser system not only scores in terms of speed, but also on the strength and durability of the welded seam. Laser welded seams are more resilient than conventionally created weld seams - a distinct advantage when tubes are to be formed and manipulated following welding.
Laser cutting - through thick and thin
The benefits of speed and precision are also apparent in the laser cutting and profiling of tubes. In instances where traditional methods such as drilling, milling, sawing or die cutting reach their limits, laser cutting opens up new possibilities.
All of the traditional methods of cutting and machining tubes generate mechanical loads, which, in turn can induce stresses into the materials and parts being processed. Laser cutting on the other hand is a contact free and highly flexible process. Simple programme changes enable different parts and profiles to be produced without the need to perform any tool changing operations.
The thermal load on components which are cut using lasers is also minimal as demonstrated by Rofin's StarCut Tube system, which is used to manufacture miniature, intricate components such as 200µm diameter medical stents precisely and accurately in under 60 seconds per stent.
However, the laser cutting process is not restricted to such small and thin section parts. Large parts, too, can be cut reliably and quickly by laser, whether it is a simple web cut or very complex notch and contour cut. Moreover, thanks to the excellent quality of laser cut edges, there is often little or no further work required on the part, thus reducing component production times.
Alessandro Falconeri, founder and owner of the Italian company, Dimensione Laser, has now been reaping the benefits of laser processing for more than ten years. The company has a total of five tube cutting systems installed, each of which uses a Rofin CO2 Slab laser. The systems are used to produce a large variety of different parts, many of which are low volume items, which benefit from the flexibility of laser welding. Often only a simple program change is needed to move from one product to another. Low maintenance and efficient operation aside, Mr Falconeri believes the success of his laser welding systems lies in their ability to produce a wide variety of parts and component geometries economically, even in very low volumes.
Laser marking
Steel tubes often require marking for quality control purposes and to enable part traceability. In these instances it is essential that the mark is permanent, clear and applied in the shortest time. Rofin has developed a concept which enables tubes to be marked ‘on the fly’, and once integrated within the tube production line, this system can be used to mark part numbers, production dates and times, bar codes, data-matrix codes and even successive serial numbers. Laser marking is unaffected by surface impurities such as the thin film of oil that may be present following tube forming.
So, whether the task is welding, cutting or marking - even of the smallest micron-precision device, lasers offer reliability, flexibility and operational economies.