A diamond is a chunk of coal that made good under pressure. - Anon
MANUFACTURING TECHNOLOGY
The industry game changer - 3D Printing or Additive Manufacturing Called disruptive technology 3D printing with metals has exploded onto the world of parts manufacturing. With its key benefits of time and cost savings and real opportunities of never-before-achieved solutions 3D printing is heralded as a significant game-changer.
market cost of metal powders.
Selective Laser Melting (SLM)
A more important advantage of the BeAM machine lies in there being no constrained operational spaces making it highly suitable for working in difficult to reach places for repair work, or building and shaping an oversized part.
The rate of uptake across a number of industry sectors is recorded daily in international press with industry leaders extolling forecast benefits for the design, development and manufacture of aeronautical parts, car parts, and medical implants, and more recently 3D printing is being realized as a secondary contributor to industries such as injection moulding.
An example used by the BeAM company is the repair of critical turbine parts. In 2015 some 800 aeronautical parts were repaired and put back into use under very demanding regulation requirements.
Selective Laser Melting occurs where a multiple laser beams are directed towards a flat bed of metal powder following a program predesigned in CAD. The product or products are constructed in a build chamber containing an inert gas atmosphere with the laser beams making successive passes over the metal powder guided by a 3D CAD program.
To embrace the new technology of additive manufacturing requires an understanding of the techniques used by the currently available laser systems. This article will explain the two key processes of SLM and LMD that use metal powders with examples of each as used in industry. Laser Melted Deposition (LMD) or Direct Energy Deposition (DED) Laser Melted Deposition is a process where the laser energy is transformed into thermal energy through interaction with a stream of metal powder, solidifying it into a dense deposit with an excellent metallurgical bond. The high brightness laser source means the laser spot can be focused right down to micron range resulting in very accurate part building. The example laser system is a BeAM developed by a French laser company BeAM Machines. The powder is injected onto the desired location using a coaxial nozzle, patented as a CLAD nozzle, that guides the powder through a coniform annular gap encircling the laser beam, onto the melt pool. By directing the powder using inert gas very narrow tracks of less than a millimeter can be achieved. The flexibility of the coaxial nozzle provides high efficiency of powder use, an important factor given the current
A measure of this success has occurred where the repaired turbine parts showed a lifecycle six times their original lifecycle enabling the craft to fly 60,000 hours without further repair as against the 10,000 flying hours previously achieved. Where metallurgically bonded surface repairs can outlast original part life the results makes the DED process a very economical proposition. Safran (Snecma), a French aircraft company that has an ‘Open Innovation’ collaborative program, worked with a French laser company BeAM to explore the opportunities offered by the DED process. The outcome announced in June 2015, was the adoption of this technology to Safran’s additive manufacturing department to use in the development of new parts as well as for repairs. The BeAM Machine is designed to effectively perform three different AM processes, namely, reliable direct manufacturing of complex shapes as stand alone products thanks to the 5 axis motion system with a fixed cladding nozzle orientation ; secondly, new features or functions can be added to existing parts; and thirdly repairs of worn out parts. A final consideration is the acquisition of metal powders. Powders provide a greater economic use of raw materials through optimization in nozzle control. LMD uses powdered metal quality already available for other industrial uses and does not require very fine metal or alloy powders. Micron sized powders from 45 to 75 to 125 microns are all usable in the specifically designed nozzle. A full range of metals and alloys are available including stainless steel, tungsten carbide, nickel alloys such as Inconel, and cobalt alloys such as Stellite. Companies who choose to invest in this range of technologies may find powders are supplied by the laser company itself thereby minimizing powder sourcing issues.
Powder is added as the product is built hence the term additive manufacturing. Lose metal powder is a health hazard so SLM laser systems require build chambers to keep the powder confined to a specific area of the machine with handling devises or procedures built-in. Build chamber size can restrict the size of the end product and this can be seen as a limitation, however, the turn-key style solutions offered by SLM Solutions, by way of example, constantly seek to up-grade operations in terms of increasing speed of laser operation and automating metal powder management. Product designs are developed using a 3D CAD program and this allows for desk-top alterations and review well before production actually occurs. Using CAD in pre-production has been shown to keep costs low, to improve on the current product design and even to design complex products never before possible. The model created in the CAD program is broken into ‘layers’ that the SLM laser system uses to define the scanning path of the laser beams. As the machine deposits thin layers of metal powder the laser beams pass over the powder melting it and gradually building the product through the repeated process governed by the geometric information contained in the CAD model. A complete melt provides a density of approximately 100% achieving mechanical properties that can be matched with traditionally manufactured parts. With additive manufacturing, parts must be re-designed, not transitioned from previous processes. The 3D CAD design offers greater options not available to tooling processes, manufacturing complex aesthetic shapes is no longer a problem. 3D CAD design parameters allow the design of very complex structures inside a part.
to be machined together. Now, using SLM technology there is one single part, and, it is five times stronger. Advantages of time to completion are evident, while less joining provides for a stronger end product, a major attraction where parts are used in high stress environments such as aircraft. SLM Solutions now provide powders to their installed base. Popular amongst users is titanium due to the light-weight properties attained in a finished part, an attractive proposition to aeronautics and automotive companies. Stainless steel and hard steels (tool steels) are also in use, an example is building conformal cooling inserts for use in injection moulds to improve mass production outcomes. Choosing the best AM solution The general convenience of additive manufacturing (AM) of metals is already evident. Uptake of system type either LDM or SLM will indicate the direction taken by different industry groups as the most appropriate solution. It is clear AM reduces time and costs from design to manufacture. While constraints exist we are witnessing financial gain, efficiency growth and process improvements that are significant and outweigh some traditional manufacturing processes. Costs of materials and AM technologies remain high but amortized across volume and early market penetration means opportunities will overcome the challenges of start-up. The AM 3D printing industry is relatively young and healthy offering new uses of laser technology while challenging manufacturing processes. European countries and the USA are investing heavily, Australasia needs to keep up with this fast paced game-changer called 3D printing or we could get left behind.
For example the fuel nozzle for aircraft engines manufactured by GE in the USA when using traditional processes comprised 18 separate parts that had
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NZ Manufacturer April 2017
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