1. Scope

Keywords

Rationale

In recent years, Additive Manufacturing (AM) has become an established manufacturing route alongside casting, forming, machining, joining and surfacing processes. Defined in BS ISO/ASTM 52900:2015 as a process of joining materials to make objects from 3D model data, usually layer upon layer, AM is often cited as offering direct and decentralized production, with reduced dependency on expensive and dedicated tooling. 4.2 While the field of AM has been subject to many technical advancements in the past three decades, the high cost (purchase, operation, maintenance and depreciation) of AM machines and materials present major challenges to AM progression (1). There has been limited ability to replace conventionally made parts economically, particularly large parts. The application of AM has therefore been primarily focused on niche, high-value and technically-demanding parts of small-build volume, where the benefit of greater design freedom offsets the high cost. 4.3 Wire Arc Additive Manufacturing (WAAM) is a directed energy deposition (DED) additive manufacturing technology that is broadening the applicability of AM. Using an electric arc as a fusion source to melt wire feedstock, metallic end-use parts of medium-to-large build volume and low-to-moderate levels of complexity can be cost-efficiently produced. This capability can be attributed to the low cost of wire relative to metal powder used for powder-based AM for many materials, low capital expenditure, and a high deposition rate achievable within a flexible build envelope. Moreover, by lowering the barrier to entry, the non-tangible benefits of AM and DED may be accessible to more cost-sensitive manufacturers for the first time. 4.4 A compromise of the high deposition rate is that an as-built surface can be uneven and within a wide manufacturing tolerance. This means that WAAM is often reliant on post-process finishing to meet dimensional and geometric requirements. However, even with post-processing accounted for, substantial raw material and cost savings have been demonstrated in comparison to CNC machining and forging processes. Besides new part manufacture, as a DED process, WAAM can also be readily applied to feature addition and repair applications. 4.5 Recently, WAAM is becoming increasingly industrialized, with growth in both numbers of end users and equipment suppliers. The aerospace industry, as an early adopter of WAAM, has seen the process mature significantly for production of large titanium alloy aerospace components previously conventionally forged and machined. For example, WAAM parts produced by Norsk Titanium achieved US Federal Aviation Authority certification for production of WAAM parts for the Boeing 787 Dreamliner in 2015 (2). Other applications of WAAM have been demonstrated in space, nuclear, automotive and marine industries, as well as in design, architecture and art. NOTE 1The Military Aviation Authority, UK MASAAG Paper 124 Issue 1 and DNVGL-CG-0197 provide guidance for qualification and certification of WAAM for military and marine applications, respectively. General certification guidance for AM, including recommendations applicable for WAAM is provided in guidance documents by ABS 299 and Lloyds Register. Information on materials, material tolerances, and quality control procedures and processes for the aerospace sector for Wire Fed Plasma Arc DED is provided by SAE AMS 7004, and for Titanium alloy preforms, SAE AMS 7005. 4.6 Despite the growing interest and application, there is limited information to aid prospective users in effective implementation of WAAM. This guide is intended to fulfil this need through providing practical guidance to enable organizations to embrace the technical and economic opportunities associated with WAAM.