ANALYSIS: AEROSPACE


high-carbon steels, dissimilar materials, or crack-sensitive materials.


An enhanced spike shape is


good for welding copper alloys and other reflective materials with a high conductivity, where there’s an initial high peak to couple into the material. Once the initial spike of energy starts melting the surface then absorption increases about 20 times, so the rest of the laser pulse energy can be much lower, Naeem explained. The spike is in the order of 0.5 to 5ms in duration.


Another beam shape is spike


removed, which is useful for low penetration welds that require good cosmetic appearance. Ramp-up shape, which slowly increases the intensity in the welding pulse, is useful for materials with low melting points or low reflectivity.


Allen said during his ILAS


“The fatigue life of welded joints was found to be an order of magnitude longer than riveted joints”


presentation: ‘You do need to think about the process before and while you are applying laser welding: how you do it and whether it’s economical to apply, and the performance is satisfactory.’ In the Oliver project Queen’s


University Belfast carried out offline simulation and cost modelling of the processes, to make sure the fixtures were compatible with the welding equipment and the laser could


access the areas it needed to access. The laser joining process was developed by TWI using IPG Photonics equipment, and the Manufacturing Technology Centre (MTC) designed fixtures and carried out non-destructive testing. Along with welding thin sheets, the group at TWI investigated joining thicker (4-6mm) pieces of titanium with titanium metal matrix composites (MMC). This meant a strut structure could be fabricated that would weigh significantly less than if the strut was made entirely out of titanium, Allen said. The aerospace firms


wanted to use near-net-shape manufacturing and assembly methods to cut down on the weight of these cylindrical struts. The Oliver project demonstrated that this can be achieved using laser welding.


Furthermore, the low heat input of laser welding meant carbon- fibre reinforced Ti-MMCs could be incorporated in these assemblies, which, again, leads to weight savings. A final demonstrator


produced as part of the project were wing leading edge structures. These are also made from sheets of titanium, but the maximum width of the sheet is limited which, in turn, limits the maximum length of leading edge structure. The project developed high-quality laser butt welding procedures, which, with minimal additional processing, are then suitable for air flow surfaces. Naeem, in his talk,


commented that Prima Power Laserdyne is now looking to develop pulse shapes that will improve laser welding of additive manufactured components, including those made from titanium alloys. l


PRIMUS AEROSPACE INVESTS IN TITANIUM ADDITIVE MANUFACTURING


Primus Aerospace, a contract manufacturing partner to aerospace, defence & space OEMs, has joined additive manufacturing (AM) firm Velo3D’s partner network by investing in a Ti6Al4V Sapphire metal AM system. This is the first titanium-


dedicated metal 3D printer from Velo3D that will be used solely for aerospace & defence applications. Primus has identified the system as a solution for many applications it currently serves in the production of cube satellites, hypersonics and turbine engines. The company is a top-tier supplier for the leading defence primes and the majority of aerospace OEMs, including Lockheed, Boeing, Northrop Grumman, General Dynamics, and Raytheon. Equipped with two 1kW


lasers and capable of printing 60cm3


of material per hour, the


Ti6Al4V Sapphire can print low angles and overhangs down to zero degrees, as well as large diameters and inner tubes up to 100mm without the need for supports. This not only reduces the need for post-processing,


but also overcomes the ‘45 degree rule’ for conventional AM, which recommends supports for any surface less than 45 degrees. This increases the wide range of designs that can already be developed with additive technology. The system offers a cylindrical 315mm diameter build chamber, available in 400mm and 1,000mm high configurations. In-situ metrology sensors are used to enable visibility into the quality of every layer of the build.


The partnership with Velo3D will enable Primus Aerospace to deliver unique design freedom and high-quality AM services to its customers. Using the new manufacturing solution, Primus is looking to unlock powerful design and manufacturing capabilities that will enable the realisation of previously unattainable geometries and optimised solutions as well as the exploration of novel aerospace applications. ‘Primus is proud to be a leader in this manufacturing category,’ said Gary Vaillancourt, vice president of engineering and technical


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Engineers examine a titanium fuel tank printed with no internal supports. Such tanks/pressure vessels are designed for use in aerospace and defence applications


sales. ‘Our customers require maximum performance of their aerospace-related systems and, together with Velo3D, we can redefine what is possible in manufacturing through advanced AM technology.’ ‘Primus Aerospace is an


excellent partner for us with their customer focus, commitment to innovation, and adoption of leading-edge technology,’ added Benny Buller, founder and CEO of Velo3D. ‘Our capabilities will help them deliver to engineers


and supply chain managers the part designs they want, not the limited part geometries that other commodity-AM suppliers say they can have. The synergies between our two companies will support developers of new products to optimise their designs without compromise or restraint.’ Primus Aerospace has now


taken delivery of the titanium Sapphire System and will begin offering titanium printing at its facility located in Golden, Colorado.


SUMMER 2021 LASER SYSTEMS EUROPE 15


Velo3D


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