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tecnica 92 Gennaio/Febbraio 2020 Automazione e Strumentazione OIL & GAS tured in an additive way are suitable for fast repairing in the event of damage. Technology Briefing 3D printing is a ‘family’ of technologies characterised by the suc- cessive addition of layers of material, one after the other; in this sense, it is logically the opposite of subtractive technologies (e.g. CNC machines) and an alternative to moulding technologies. The characteristics of 3D printing are potential geometric liberation of the parts; time/cost efficiency in the case of single pieces or small runs; and added value to the product (topological optimisation). All these factors create a competitive advantage for the company. Generally speaking, the definition of ‘3D printing’ gathers many different technologies, which differ substantially for the initial state and type of construction material (solid, liquids, powders etc.; paper, plaster, plastics, metals etc.). Each solution has advantages and disadvantages; it is therefore important to identify the needs that are to be satisfied. Technol- ogies could be classified in this way: (1) ‘personal’ for hobby applications; (2) professional for prototyping applications; (3) industrial technologies for production applications. There is an inverse trade-off between the ease/economy solution and the quality obtained. The production segment of 3D printing technologies is the one with the greatest market increase; in particular, metal printing demand for components is growing rapidly. The most consolidated and widespread is ‘powder bed melt- ing’ or ‘direct laser sintering on metal’, identified by the S.L.M. (Selective Laser Melting) acronym. The process consists of a source of energy (laser or other beams) moving selectively on a layer (10-100 microns) of a special metal powder and solidifying it. One roll lays the layers of powders on the worktop, one after the other; in the vacuum chamber there are also inert gases, such as argon or nitrogen, to guarantee the purity of the powered mate- rials. The desired geometry - as per CAD file - is finally solidified together with the appropriate construction supports, which will be removed in a later stage. The process also involves an up/down temperature ramp, required to achieve the change of state of the material from powder to solid. The final results, for aesthetics and mechanical performance, are very similar, or even better, than components manufactured with traditional technologies. Generally, this solution offers high quality construction in terms of precision, smoothness and density of the parts, and it is being applied also for the most demanding solution (process complexity, management costs). Furthermore, SLM technology offers the possibility to adapt to post-processing operations such as milling, turning, heat treat- ments and other aesthetic and protective treatments, and for this reason it was adopted to print the valve component described in this paper. Market leader brands in this arena are currently number 5-6, but several minor brands already exist and new-comers are arriving. After choosing the additive manufacturing technology and the printer brand, it is necessary to choose the specific machine model. Each of the 3D printer models differs from each other in relation to many factors, including the material choice and the size of the working area, which is related to the dimensions of the final part. The same machine can print many materials, and a wide selection of materials is available on the market: steels (stainless steel, pre- cipitation hardening), aluminium, titanium, cobalt chrome, and nickel alloys. For purely indicative purposes, this technology can be used for many possible applications: unique, fully functional metal parts, readily available, hard or impossible to do with other tra- ditional technologies. Therefore, several solutions are already on the market, in the field of mechanical engineering, aero- space, medical and dental, automotive and racing and oil and gas; it is also in use for parts intended for tooling, prototypes, and final components. Case Study In order to test and validate additive manufacturing technology for typical Oil & Gas components, Xsight by Saipem (a Saipem Divi- sion) established a collaboration with IMI Orton, a manufacturer of critical butterfly valves, and CMF Marelli, a 3D printing dis- tributor in Italy, with the target to analyse the gap with the tradi- tional manufacturing approach and to ease the production of spare parts for End User warehouse optimization. The selected component was an 8’’ disc ANSI Cl. 150 triple eccentric metal to metal seated valve with anti-cavitation trim in Inconel 625 (see figure). The choice fell on this item considering the complexity of shape, material, size, and the time necessary to manufacture it with tradi- tional technologies. Workflow During this collaboration, Xsight shared its Plant and Process know-how, and CMF Marelli its know-how relevant to additive manufacturing, including the selection of the 3D Printer and IMI Orton the valve know-how. Starting from the disc drawing (Step file) shared by IMI Orton, the main project phases are: Re-Design; Purchas- ing of Inconel 625 Powders; Printing & Milling; Shipping; Assembling and Testing & Validation. It is remarkable to note that printing time was 37 machine hours without any post heat treatment. The conventional lead time for the casting would have been approximately 6-8 weeks. Testing Phase The disc was then received by CMF Marelli, and prior to its assembling relevant inspections were conducted; hardness and material weight were in accordance with Alloy 625 requirements. PMI was performed to verify compliance with Alloy 625. Quotes were, in general, according to the drawing of the compo- nent, even if it was nevertheless necessary to re-machine some parts to achieve the required tolerances The disc was then assembled into the valve, and final testing was conducted. After valve assembly, the final tests were executed. Test pres-