Rofin, partners of Laser Resources , outline the uses of laser technology in welding, cutting tubes and profiles and marking of tubes.
Laser welding – quick and reliable
The advantages of laser joining have been known since years in Esta Rohr company in Siegen, Germany.They have been producing meters and meters of longitudinal seam welded, stainless steel pipes with different diameters per 3 shifts operation with a 4,5 kW CO2 Slab laser and the Profile Welding System (PWS) from the laser producer Rofin in Hamburg.
Compared to the classical TIG-welding, the round laser is three times as fast. For example, while welding tubes with the dimension of 18x1 mm with the conventional TIG-machine with 5.5 m/min; compared to that the laser machine can do 16 m/min, whereas it is not the power of the laser that restrains the speed, but the integrated annealing unit. But it is also important that all usual stainless steels, no matter if austenitic or ferritic, can be welded correctly. In the meanwhile we especially manufacture the ferritic chrome steels by laser welding.
Besides the known austenitic materials, ferritic steels like 1,4509, 1,4520 or even 1,4521 are currently rediscovered, as they are an economical and at the same time technically feasible alternative in many application areas due to their low costs at equal corrosion resistance. When manufacturing stainless steel tubes out of these materials, the laser can use its process advantages by the possibility of an exact controlling of the inserted energy input per unit length.
The laser also offers advantages when it comes to availability. The contact-free working CO2 Slab laser is head and shoulders above the TIG-welding with its electrodes that have to be replaced regularly, which causes an inevitable compulsory break of the machines; the laser makes an availability of almost 100% possible.
Besides ESTA, more than twenty new companies worldwide have decided in favour of ROFINs CO2 Slab lasers combined with the Profile Welding System for the manufacturing of stainless steel tubes. With its integrated gap recognition the PWS sensor technology adjusts even the smallest meanderings of the welding position and therefore optimal welding results are possible - even under difficult conditions. The laser system does not only score as to speed but also to resistance. Laser weld seams are clearly more resilient when post-formed than conventionally created weld seams, providing advantage when tubes are transformed afterwards.
Laser cutting - through thick and thin
Not only at welding, but also at cutting tubes and profiles, lasers can play off their speed and precision. When methods like drilling, milling, sawing or die cutting meet their limits, laser cuttings opens up new possibilities. While with conventional methods enormous mechanical powers act upon the work piece, the laser works contact-free and highly flexible. By simple changes of the programme even complex outlines can be cut without any exchange of tools. The thermal load on the work piece is minimal as well so that even µm-exact tubes, for example used for syringes or medical implants, so called stents, can be welded easily. ROFIN's StarCut Tube cuts such stents precisely, accurately and efficiently in less than a minute.
Alessandro Falconeri, founder and owner of the Italian company Dimensione Laser, says that Rofin’s Slab laser technology is often used in tube welding machines of the Profile Welding Systems. The slab lasers work without gas circulation and that makes them compact and low in maintenance. This results in highest availability and minimal gas consumption.
Laser marking – permanent and captive
With its flexibility the laser also scores at the permanent marking of tubes for quality control. In the automotive industry as well as in other tube processing areas, a more and more advanced tracking opportunity with media resistant and captive markings is required. Rofin's marking experts in Bergkichen, Germany, have developed a concept where the laser marks the tube while passing, without stopping at the marking station. In addition to article numbers, production dates and times, bar code or datamatrix code, even ascending or descending serial numbers can be applied firm and reliable. Minor impurities like leavings of oils or similar fluids on the tube surface are negligible.
CO2 Slab laser: Non-stop cutting and welding
In diffusion cooled CO2 Slab lasers, available with up to 8 kW, between two extensive electrodes a high frequency gas exchange takes place. The low distance between the electrodes make an intensive heat flow through the directly water-cooled electrodes possible (diffusion cooling) so that a comparatively high power density is reached. The resonator is built out of rotary parabolic formed mirrors and allows the out coupling of a well-focusable laser beam. In external, reflective beam forming components the raw beam is formed into an axially symmetric beam with an almost perfect beam quality of K > 0.9.
Thanks to the patented construction, Rofin’s CO2 Slab lasers are costumer-orientated and low in maintenance. The laser e. g. does not need any turbines, as there is no gas circulation. The gas bottle is integrated in the laser head so that you can do without an external gas supply. The beam that is created in the resonator is out coupled by a diamond window, which makes the use of transmissive optics dispensable. Solely water-cooled mirrors act as reflective optics that is robust and wear-free.