Fiber Lasers: Enhancing the manufacturing process

TECHNICAL DIGEST Fiber Lasers: Enhancing the manufacturing process SPONSORED BY: With their robustness, high electrical efficiency, and ease of use, high-power fiber lasers have earned an important position in the materials-processing arena by performing welding, cutting, brazing, cladding, and other operations to high standards. This tech digest provides examples of recent technological improvements to two different fiber-laser manufacturing processes. 3 Fiber laser improves cladding and additive manufacturing 11 Fiber laser cutting heads detect slugs 17 Fiber Laser Welding Cuts Costs and Improves Results Reprinted with revisions to format from INDUSTRIAL LASER SOLUTIONS. Copyright 2017 by PennWell Corporation

Originally published March 16, 2016 Fiber laser improves cladding and additive manufacturing Automated process is immune to damage from back-reflections FRANK GÄBLER CLADDING IS A WELL-ESTABLISHED PROCESS for improving the wear and corrosion resistance of metal parts. While traditional arc welding and laser-based methods are economically viable processes that deliver excellent results, there is a risk of carbide grain formation during the cladding process, which can compromise the mechanical strength and lifetime of the cladding. This article reviews a new automated, laser-based process that avoids grain formation, and explores how the process has been enabled by a new generation of fiber lasers that are immune to back-reflections. Traditional laser cladding characteristics The methods and benefits of laser cladding have been described in this magazine several times in the past [1, 2]. Briefly, the cladding material is introduced onto the part surface in powder or wire form, and the laser is used to selectively melt this material, as well as the substrate, to a very small depth in order to fuse the two. Laser cladding delivers several advantages over arc welding and thermal spraying methods. Specifically, precise, limited application of heat results in minimal or no heat distortion in the part, eliminating the need for subsequent post-process machining. Laser cladding also produces very little mixing between the deposited and substrate materials (dilution), and yields a strong, truly metallurgic bond between the clad layer and substrate. 3 However, several researchers have noted that the rapid material cooling that occurs during laser cladding sometimes produces bonding defects and some

Fiber laser improves cladding and additive manufacturing porosity in the clad layer, and can lead to the formation of grains or other heterogeneous microstructures [3-6]. The specific nature of these structures is highly dependent upon the exact laser processing parameters and cladding materials employed, and have been observed to include cracks, pores, and a variety of columnar and banded grain structures. Each of these structures can limit the lifetime and effectiveness of the cladding. For example, cladding cracks offer sites for corrosion to occur, and may even provide a path through the clad layer to the substrate itself. Grains or other microstructures affect the mechanical properties of the clad layer, and have proven in some cases to reduce clad tensile strength. Optimized cladding The effect of various process parameters such as laser power, laser beam scanning speed and material feed rate, and the precise recipe of cladding material have been studied and characterized in some detail. By properly controlling these factors, the formation of undesirable clad microstructures can be minimized or eliminated in a deterministic manner. Specifically, it is possible to create a system for high-performance cladding by accurately modeling the cladding process, optimizing the materials employed, and then carefully controlling the cladding process to replicate the calculated results. Köthener Spezialdichtungen GmbH (KSD; Kleinwülknitz, Germany) has developed such a system, which they call the Rapid Laser Materials Manufacturing system (R:LM2). The system consists of three main functional elements, namely a material mix system, a mini-melt oven, and a deposition control system (FIGURE 1). The material mix system includes several different cladding powders as well as a computer equipped with material simulation software. The mini-melt oven includes a fiber laser and a sealed process chamber containing focusing optics, a powder delivery nozzle, a motion system, a pyrometer, and a process monitoring camera. The deposition control system has a computer running CAD/CAM software and finite element method (FEM) simulation software. 4 The R:LM2 exploits the fact that a large variety of different claddings can be created by combining a limited set of metal powders. To choose the right set for a given application, the customer s requirements in terms of desired clad

Fiber laser improves cladding and additive manufacturing FIGURE 1. Block diagram of the main functional elements of the KSD Rapid Laser Materials Manufacturing system. mechanical and chemical (e.g., corrosion resistance) characteristics are input to the system. Then, the material simulation program uses phase diagrams to calculate the optimum combination of available clad materials that address the performance requirements. 5 The FEM simulation software in the deposition control system then takes this recipe and determines the cladding parameters, including powder feed rate, laser power, gas composition, and process temperature necessary to achieve optimum results. Within the sealed process chamber, the metal powder is sprayed onto the workpiece through a nozzle and then melted by the laser. The exact shape of the clad area is defined by the movement of the nozzle and laser beam, which is controlled by the CAD/CAM software in the deposition control system. The

Fiber laser improves cladding and additive manufacturing deposition control system monitors the size and location of clad area with the process camera, as well as the process temperature using the pyrometer, and adjusts the parameters as necessary to achieve the desired results. The R:LM2 also closely controls the gas atmosphere within the process chamber. This is critical to delivering homogenous and reproducible cladding. Clads produced by the R:LM2 exhibit dramatically finer carbide grain structure than traditional laser clads. These coatings are free of pores or cracks, and can reach hardness levels of 68 HRC. In addition, the system also offers the potential to significantly reduce cladding cost because the most common traditional cladding materials, including nickel alloys, tungsten carbides, and Inconels, are all expensive. But the sophisticated modeling and precision deposition capabilities of the R:LM2 enable it to achieve the same results, in terms of clad corrosion and wear resistance, using combinations of less costly ferrous alloys. Plus, the system substantially reduces cycle times for fabricating complex parts. Fiber laser considerations Fiber lasers are a good match for the requirements of the R:LM2 process because they offer the necessary high power output (around 800W) and near-infrared (NIR) wavelengths, but with lower cost of operation and much longer service intervals than other laser types, such as flash lamp-pumped Nd:YAG. With first-generation fiber lasers based on single-emitter laser diode pumps, all the numerous pump components are typically fused together to maximize stability. While this approach is generally robust, it is particularly susceptible to damage by back-reflections from the target material. Thus, some type of optical isolator must be used when processing reflective metals, such as copper and brass. Also, the use of fused components (sometimes including the final delivery fiber) means these lasers are not field-serviceable. So, if any components are even slightly damaged, the entire laser must be shipped back to the factory and replaced. 6 Coherent s novel modular approach to fiber laser design is based on the use of diode laser bars, rather than single emitters, as the pump sources. The light from these pump bars is introduced into the gain fiber using a beam combiner consisting of discrete optical elements. This same beam combiner collimates the output from the gain fiber, and other optics efficiently couple this into the final delivery fiber.

Fiber laser improves cladding and additive manufacturing FIGURE 2. The use of free-space optics for coupling in pump light and extracting laser light yields a fiber laser that is immune to damage from back-reflections and can be easily field-serviced. The geometry of the beam combiner prevents back-reflections from reaching the pump diode laser bars. Together with the absence of damage-prone splices, this makes this design immune to damage from back-reflections (FIGURE 2). The modular approach also allows both field serviceability and flexibility because it enables the end user to exchange the delivery fiber in a matter of minutes. Moreover, the other modular components, such as the pump diode bar and even the gain fiber, can all be field-replaced if necessary. After having reliability problems using a traditional architecture fiber laser, KSD switched to the HighLight 1000FL 1kW fiber laser from Coherent. This eliminated the operating difficulties they had experienced in their process because of backreflections. Applications 7 Currently, KSD GmbH is employing the R:LM2 process in the production cladding of gaskets for industrial faucets, and for the bearing surfaces of races in sliding rings or rotary feedthroughs (FIGURE 3). Such sealing components are used in rotary pumps, immersion pumps, or screw feeders. The gaskets used in safety or control fittings have to withstand extreme forces, such as cavitation pitting or

Fiber laser improves cladding and additive manufacturing FIGURE 3. Slide rings clad with an iron manganese chromium (FeMnCr)-based austenitic hard alloy using the R:LM2 system. fluid flow wear. They are operated in temperatures ranging from -255 to 650 C, and are utilized with abrasive media at stroke rates of >100,000 per year. The bearing race surfaces need to operate at a travel rates of 400,000 km/year in conjunction with highly viscous media having abrasive or adhesive properties. To date, the clads produced using the R:LM2 process from entirely ferrous alloys have proven effective in these applications. KSD is also developing applications for laser additive manufacturing of three dimensional parts using R:LM2 technology. Typically, the process starts with the deposition of a relatively thin (600μm) layer of material in several strips on the wall of the part. Then, the seams between these strips are filled in a second pass. 8

Fiber laser improves cladding and additive manufacturing The powder utilization in this process is 70 80%, and the final part dimensional accuracy is in the 0.2 0.3mm range. This dimensional accuracy is a factor of about 10 lower than with traditional powder bed methods, but like selective laser melting final part dimensions can be rapidly obtained with mechanical post-processing. In this case, the unique advantage of the R:LM2 method is that a variety of materials can be processed and be deposited with high flexibility using the material mix computer. In conclusion, a new, automated system for laser cladding simplifies the process and makes it more economical by enabling it to use less costly, ferrous alloys. Together with a fiber laser source that is immune to back-reflection damage and is also easier to service, this should help to make laser cladding and laser additive manufacturing accessible to a broader audience. REFERENCES 1. V. Malin and S. Woods, Efficient high-power diode laser cladding, Industrial Laser Solutions (Aug. 2009). 2. K. Parker, Higher output power and customized beam shapes substantially improve heat treating and cladding, Industrial Laser Solutions (Jul/Aug. 2012). 3. S. Zhou, Y. Huang, X. Zeng, and Q. Hu, Mat. Sci. Eng. A-Struct., 480, 1 2, 564 572 (May 2008). 4. V. Ocelík, I. Furár, and J. De Hosson, Acta Mater., 58, 20, 6763 6772 (Dec. 2010). 5. L. Parimia, G. Ravi, D. Clark, and M. Attallah, Mater. Charact., 89, 102 111 (Mar. 2014). 6. T. Abioye, D. McCartney, and A. Clare, J. Mater. Process. Tech., 217, 232 240 (Mar. 2015). FRANK GÄBLER (frank.gaebler@coherent.com) is director of marketing at Coherent, Santa Clara, CA, www.coherent.com. 9

Originally published September 14, 2016 Fiber laser cutting heads detect slugs Process could eliminate need for postcutting detection equipment TOM KUGLER THE USE OF FIBER-DELIVERED LASERS and robots is a natural combination for flexible, low-cost, three-dimensional (3D) cutting for production applications in many industries, with automotive systems leading this trend. In automotive manufacturing, production volumes requiring flexible tooling, along with the use of very strong and hard materials such as boron steels and high-strength steels, make lasers a natural choice for cutting solutions. For these reasons, robotic laser cutting applications have grown since the early 1990s. Using better trepanning robots, modern solid-state lasers, and more complex fixtures and control systems, as well as new robotic cutting heads, have all aided this growth. The challenge One process issue that requires attention is the challenge of slug detection. A slug is the material inside a cut feature that normally drops away during the process, such as the disk that falls away when a circular hole is laser-cut. Retained slugs can be related to many issues, including a bad cutting process, an incomplete cut because of thickness changes, a contaminated surface, poor gas flow, damaged optics, or poor focus position. Other contributors to the problem include material thickness changes from lot to lot, unintended changes to the cutting program relating to speed or power, and that thicker materials sometimes have a cut slug that rotates and becomes jammed in the hole. 11

Fiber laser cutting heads detect slugs Detection of a slug can help eliminate poor processing parameters, but it is also vital because a retained slug can cause problems down the line in quality control, manufacturing, or even life of the component or end product. Slugs that fall during the laser cutting process are handled as recycled scrap and there are specific steps in the laser cutting process when slugs are removed. For flat sheet metal components, the slugs fall free during cutting to a scrap conveyor or receptacle. However, with tubing or other closed parts, the slugs are removed by strategically tilting the component at specific orientations above the scrap handling hardware to fall out by gravity. In other instances, slugs may be lightly retained, easily falling out during further assembly or when the required component is placed into the hole. However, if they are solidly retained, that assembly step will fail and can cause damage to components. In the case where slugs fall out during later assembly steps, they now become loose debris that could interfere with other processes or become a nuisance rattle when trapped inside the closed structure of a completed component. Recently, a Tier One automotive supplier of automated systems contacted Laser Mechanisms (Novi, MI) for a slug detection solution that would have minimum cost and cycle-time implications. The tool 12 Robots provide a special environment for laser cutting heads. In comparison to two-dimensional systems, the robotic cutting head needs to be lightweight but also very robust to deal with the occasional collision with the part, or tooling when errors are made in programming or operation. Often, the cutting head employs a crash-protection link between the robot and the cutting head to deal with collisions with the part or tooling, or the hazard of snagging the cutting head umbilical (including the fiber-optic cable), and damaging the fiber or other conduits. Robotic heads must also be compact not just for weight savings, but also because they are manipulated near tooling and the other surfaces of the 3D parts they process. Just like other cutting heads, robotic cutting heads must allow for different collimator and focus lens combinations for the material being cut, 20

Fiber laser cutting heads detect slugs FIGURE 1. A working clearance envelope comparison of straight and right-angle robotic heads. bar coaxial gas pressure, and have all the alignment capability for tip centering and focus position adjustment. 13 FIGURE 1 depicts straight and right-angle robotic cutting heads. Straight versions are easy to integrate with systems that process both left- and right-hand parts on automobiles, but the straight versions have more access issues. While the head is not that long, the fiber connector and ~100 200mm minimum bend radius of the fiber itself requires a larger work envelope of 600 700mm above the surface. By employing a right-angle design, the fiber-optic cable and the rest of the umbilical

Fiber laser cutting heads detect slugs connections can easily be directed down the robot arm, minimizing the working envelope to no more than ~ 275mm. Laser Mechanisms FiberCut line of robotic cutting heads incorporate all of these features and more to optimize the robotic cutting process. Specific to the head is its low-moving-mass, self-contained z-axis for capacitive height sensing of surface contours. If the entire head moved on a z-axis, then this action would shake the robot and create inaccurate cuts. FiberCut only moves the lower section, containing the focus lens and gas nozzle, which results in a moving mass of only about 15% of the head s total weight and moves that mass at over 1g acceleration rates without shaking the robot s arm. With a laser power rating exceeding 4kW, these processing heads can handle all robotic applications in materials up to and over 6mm, and from mild steel to aluminum alloys. The method Dedicated slug detection stations add cost and complexity, use valuable floor space, and have slow total cycle times. Off-line detection tools also require that the part be loaded into a different fixture in an area where the hole cannot be recut if a retained slug is found. Laser Mechanisms solution to this issue uses the robotic cutting head itself to test for slug retention. If found, it can immediately re-cut the feature while still fixtured in the robotic cutting cell. The patent-pending method employs special optical detection hardware installed into the robotic cutting head and software added to the head controller. It was found that if a slug is still in position, a short sensing pulse of light sent onto the area where the slug is suspected will return different signals if the slug is there or not. If the slug is detected, then the system can log the data and re-cut that feature immediately. 14 FIGURES 2 and 3 show the signals returned from the sensors, with and without the slug dropping out of the feature. Note the variation at the end of the signal. The long duration signal is the laser cutting process, while the short signal just after is the slug detection signal. The high spike indicates the presence of a slug, and the low-intensity signal shows that there is no slug present.

Fiber laser cutting heads detect slugs FIGURE 2. The low level of the short optical signal at the end of the cut indicates that no slug is detected. 15 FIGURE 3. The high level of the short optical signal indicates that a slug is present.

Fiber laser cutting heads detect slugs Most slug retention issues are related to the slug hanging up at the cut s start/ stop point. In this instance, the check can be performed very quickly after the robot has completed the cut path by moving directly onto the area where the slug might be and performing the quick test. It is estimated that this check can be accomplished in only a few hundred milliseconds and isolated to areas on the part with known problem features that the end customer wants to inspect. The slug detection hardware is safely installed into the robotic cutting head and uses signals in the existing control cable, so no extra wires are required. Because the optical path inside the cutting head must be clear for processing, it is also open for slug detection without interference from other processes or the dirty environment of a laser cutting cell. Available as an optional feature, these slug-detection robotic heads can monitor system performance and part quality, and potentially eliminate the need for postcutting detection equipment. ACKNOWLEDGEMENT FiberCut is a registered trademark of Laser Mechanisms. TOM KUGLER (tkugler@lasermech.com) is fiber systems manager at Laser Mechanisms, Novi, MI; www.lasermech.com. 16

Coherent Whitepaper September 22, 2017 Fiber Laser Welding Cuts Costs and Improves Results Lasers have been employed in a variety of welding applications for many years. And, as laser technology further develops and diversifies, its uses in welding continue to expand. This article provides an overview of high power lasers in keyhole welding. It then examines the characteristics and advantages of fiber laser sources for welding from Coherent Rofin, in particular, and reviews a specific application that has benefitted from these lasers. Traditional Welding Overview Most traditional (non-laser) welding techniques currently in use are variations of arc welding. In these methods, two pieces of metal are first brought into contact or close physical proximity. The edges of the pieces may have been shaped to facilitate their joining. A high voltage is established between an electrode and the contact region, creating an arc which melts the material (or, in some cases an additional filler material or the electrode itself). The melted material fills any gap between the workpieces, or overlays them, and then solidifies to join the parts. The primary advantage of most arc welding methods is their relatively low cost, particularly in terms of the capital equipment expenditure. Furthermore, arc welding techniques are well understood and widely employed, and standards for producing and testing them are well established, so there s not much of a learning curve in bringing these processes on line. The major disadvantages of arc welding mostly derive from subjecting parts to high heat. This can result in microstructures in the melted material that yield poor strength in the weld joint, and a relatively large heat affected zone in the material adjacent to the weld. Additionally, the parameters of the arc are influenced by the local electric field, and can therefore not be set independently. Laser Keyhole Welding Most laser welding techniques can be classified into two basic categories, keyhole and conduction mode welding. Both of these welding modes are capable of being performed autogenously, that is, without filler metal, as well as with filler, if so desired. Keyhole, or deep penetration welding, is commonly encountered when welding thicker materials at high laser powers. In keyhole welding, the laser is focused so as to achieve a very high power density at the work piece. At the focus of the laser beam, the metal actually vaporizes, opening up a blind hole (the keyhole) within the molten metal pool. Vapor pressure holds back the surrounding molten metal and keeps this hole open during the process. The laser power is mainly absorbed at the vapor melt boundary and the keyhole walls. The focused laser beam and the keyhole continuously move along the welding path. At the front of the keyhole, new material is molten, and at the back, it resolidifies to become the welded joint. www.coherent.com tech.sales@coherent.com 800-527-3786 408-764-4983

A Coherent Whitepaper September 22, 2017 The small size of the keyhole region results in a precise, narrow fusion zone, with a high aspect ratio (depth to width) as compared to arc welding methods. Furthermore, the highly localized application of heat means that bulk of the work piece acts as an effective heat sink so the weld region heats up and cools down rapidly. This minimizes the size of the heat affected zone, and reduces grain growth. Thus, the laser can generally produce stronger joints than arc welding, which is one of its primary benefits. Laser welding also offers greater flexibility than arc welding, since it is compatible with an extremely broad range of materials, including carbon steel, high strength steel, stainless steel, titanium, aluminum, and precious metals. It can also be used to join dissimilar materials, as differences in material melting temperatures and heat conduction are of minor importance in the process. In addition, laser welding delivers significant cost advantages over traditional methods, when all the process steps are considered. In particular, the precise application of heat minimizes distortion in the weld and overall part, thus eliminating the need for post processing in many cases. Plus, the ability to project the laser beam over relatively long distances with essentially no power loss makes it easy to integrate laser welding with other production processes, and lends itself well to integration with manufacturing robotics. Last, but not least, new product configurations with reduced flange sizes can be realized, which is critical for light weight vehicles in the automotive industry. Fiber Lasers for Welding Modern CO2 and fiber lasers easily deliver the beam parameters and power requirements for keyhole welding. Since almost all metals become increasingly absorptive at shorter wavelengths, process efficiency is enhanced at the shorter fiber laser wavelength of ~1 µm, as compared to CO2 laser wavelength of 10.6 µm. Fiber lasers, in particular, match the requirements of keyhole welding extremely well. They typically offer output powers in the range of 500 W to 10 kw, and can readily achieve focused spot sizes in the necessary range between 40 µm and 800 µm, even at relatively large working distances. From a practical standpoint, the use of beam delivery fiber expands integration options and facilitates the use of the laser in the manufacturing environment. Finally, the high reliability, excellent uptime and favorable cost of ownership characteristics of fiber lasers make them an economically viable and attractive choice for production welding applications. There are currently several manufacturers of high power fiber lasers for welding and other materials processing applications. Coherent Rofin fiber lasers, in particular, have been designed to deliver a combination of performance, reliability, ease of integration and cost characteristics that is optimum for welding and other materials processing applications. To understand how this is achieved, it s useful to examine some of the design and construction details of these lasers. The drawing shows the main elements of the fiber laser oscillator employed by Coherent Rofin. The laser resonator is formed by a large mode area (LMA), Yb-doped, double clad optical fiber and fiber Bragg gratings for resonator mirrors. This is pumped from each end by a series of diode laser pump modules, whose outputs are fiber coupled into the gain fiber. www.coherent.com tech.sales@coherent.com 800-527-3786 408-764-4983

A Coherent Whitepaper September 22, 2017 Figure 1: Coherent Rofin fiber laser oscillator schematic, including twelve diode laser pump modules, and 6x1 fiber coupling modules which inject pump light into the gain fiber, and allow efficient extraction of the laser output. Based on this design, one set of pumps and gain fiber can produce output powers of up to 3 kw. The output from up to four of these single mode fiber laser units can then be combined into one multimode fiber to achieve powers of up to 10 kw. Alternately, the Coherent Rofin standard cabinet supports splitting the output from a single fiber laser into four separate fibers through the use of the integrated fiber-to-fiber switches. Thus, this modular construction approach allows Coherent Rofin to offer several options in terms of output power, delivery fiber diameter, and beam parameter product. The benefit is the ability to readily adapt the laser beam characteristics to precisely match the exact requirements of a specific process. Some users have experienced fiber laser damage or process inconsistencies caused by back reflections when processing highly reflective metals, such as copper and brass. Coherent Rofin lasers utilize an optimized power generation and delivery technology, as well as sensors at different positions within the system, to protect laser components from such damage. These safeguards eliminate the problem of back reflections, and allow reliable welding of brass, aluminum and copper without any concern for damaging the laser. Of course, the fiber laser is just one part of the entire welding system, which also includes a beam focusing welding head, as well as control electronics. In addition to fiber lasers, Coherent Rofin also offers beam delivery components which mount into customers machines. These can be fixed optics or complete, integrated scanning solutions, which include control of all relevant laser parameters, to fully optimize the welding process. Moreover, these integrated solutions often feature fast and flexible beam scanning technology which allows rapid beam movement from one welding contour to the next. This increases the productivity of a laser processing system enormously. www.coherent.com tech.sales@coherent.com 800-527-3786 408-764-4983

A Coherent Whitepaper September 22, 2017 Case Study: Laser Welded Towel Radiator Steam radiators for heating towels have become popular at gyms and spas worldwide. A Russian manufacturer of these towel heaters now employs an automated welding system, developed by the Dutch special purpose machine manufacturer Rodomach, which is based on a Coherent Rofin fiber laser. Figure 2: Two models of towel heater, produced by a Russian manufacturer using an automated welding system from Rodomach which is based on a Coherent Rofin fiber laser. Previously, the radiator manufacturer had utilized the traditional TIG (tungsten inert gas) arc welding method by hand in their production. The goal of the radiator manufacturer was to transition all their manufacturing to an automated system. This meant that the process would have to be able to accommodate a variety of different product configurations, including models with round pipes, as well as those having pipes with various other shapes. For all these products, the desired welding depth is 100% of the pipe thickness, and the final assembly must withstand air pressures of 25 bars. Product appearance is also critical in this application, and the manufacturer wanted to achieve a uniform, smooth seam weld, which is attractive and requires no post processing. This is necessary because the final step in their production is electro-polishing, which brings the stainless steel radiators to a mirror finish. In order to develop a laser-based solution for this process, Coherent Rofin ran trials for Rodomach at our Hamburg Applications Laboratory. These proved that the austenitic Cr-Ni-Steel AlSI 304 used by the radiator manufacturer was easy to laser weld. However, standard tooling could not ensure an optimum fit between parts for the entire operation, and a consistent, high quality seam could therefore, not be guaranteed. www.coherent.com tech.sales@coherent.com 800-527-3786 408-764-4983

A Coherent Whitepaper September 22, 2017 Coherent Rofin and Rodomach therefore undertook to design an approach which would clamp the part in a way which enables consistent welding, and also prevents part warping during the process. The particular solution was to replace the traditional, static clamp tooling used for welding with a servo-controlled clamping mechanism having integrated cooling. This method evenly clamps the part at all welding points, while the cooling prevents the joints from warping. The testing also allowed Coherent Rofin personnel to recommend a 2 kw fiber laser (Coherent Rofin FL 020) with a 300 µm delivery fiber, and focusing optics having a focal length of 300 mm, as being optimum for this application. This optical configuration provides a long depth of field, allowing the customer a high degree of process tolerance. The result is reduced scrap and improved productivity. Figure 3: Complete system for automated welding of towel radiators. Rodomach configured the system so that, through the use of a beam switch, a single Coherent Rofin fiber laser can feed two robotic welding stations which alternately process the two sides of the radiator. We pooled the control of the system, the two robots, and the laser on to one terminal, notes Roel Doornebosch, Manager at Rodomach. This simplifies operation for the customer, who had expressed some concern at the outset that the system would be complex to operate due to their stringent quality requirements. The final system we delivered operates at a welding speed of 2 m/min, and provides welds which can withstand 250 bars of steam pressure, which is ten times their original specification. Plus, the weld quality and cosmetics are consistently high. Since they ordered two additional systems after using the first one, I think we can conclude that we successfully met, and even exceeded, their expectations. In conclusion, high power fiber lasers have emerged over the past decade as an ideal tool for a wide range of welding applications. But, successfully deploying a fiber laser in a specific application requires more than just a high quality source. In particular, partnering with a fiber laser company that offers support and expertise in process development and integration, together with a worldwide support infrastructure, is critical not only to getting products to market, but also for long-term success. www.coherent.com tech.sales@coherent.com 800-527-3786 408-764-4983