TPT November 2008

C utting, S awing & P rofiling T echnology

Lasers in tube manufacture – a well-rounded process

Steel tubes are used to produce a vast array of products including water pipelines, steel furniture, machine frames and even the fine tubes of less than 200µm in diameter used within the medical device industry. Thousands of miles of pipeline, tube and profiles are formed, welded, cut and marked every day. In many cases, the machines used for this diverse range of applications have lasers at the heart of the process. Rofin, Germany, produces a complete range of laser sources and solutions, for use in an increasing number of applications. The advantages of laser welding are well known to Esta Rohr, a manufacturing company in Siegen, Germany. Esta Rohr produces longitudinal seam welded, stainless steel pipes on a 3-shift operation, using a 4.5kW CO 2 slab laser integrated within a Rofin profile welding system (PWS). “ The benefits for us are obvious ,” commented Mr Sven Pitzer, technical manager of Esta Rohr. “ Compared to 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/min. By comparison the laser achieves 16m/min, and it is not the power of the laser which restricts the speed, but the subsequent in-line annealing unit. ” Another important factor for Esta Rohr is the capability of the profile welding system to weld both austentitic and ferritic stainless steels. In addition to the range of austenitic

materials, ferritic steels such as 1,4509, 1,4520 or even 1,4521 are currently being used. These steels are often more economical, but still offer a technically feasible alternative in many application areas due to their equal corrosion resistance. When manufacturing stainless steel tubes, the process benefits of the laser allow precise control of the laser parameters and therefore the energy used to create the weld, along the full length of the tube. The laser also offers distinct advantages when it comes to system availability: the contact-free CO 2 slab laser system has an availability of almost 100 per cent, unlike the traditional TIG-welding process with its electrodes which have to be replaced regularly, causing inevitable breaks in production. In addition to Esta, more than twenty other companies worldwide have opted for Rofin’s CO 2 slab lasers combined with the profile welding system for the manufacture of stainless steel tubes. With its integrated gap recognition, the PWS sensor technology adjusts for the smallest deviation of the weld seam position, providing optimum welding results even under difficult conditions. Rofin states that laser weld seams are more resilient than conventionally created weld seams, which is a distinct advantage when tubes are to be formed and manipulated following the welding process. 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

 Laser welding of tubes using the Rofin profile welding system

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Traditional methods of cutting and machining tubes generate mechanical loads which can induce stresses into the materials and parts

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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, however, 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.

 (Below) Medical stent production using Rofin’s StarCut tube system; and (below right) a close-up view of a stent

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N ovember 2008

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