Abstract
Additive manufacturing (AM) processes allow complex geometries to be produced with enhanced functionality, but technological challenges still have to be dealt with, in terms of surface finish and achieved tolerances. Among the consolidated powder-bed fusion processes, electron beam melting (EBM), which allows almost stress-free parts to be manufactured with a high productivity and minimum use of support structures, suffers from a poor surface quality. Thus, finishing processes have to be performed. The same geometrical complexity, which is considered one of the benefits of AM, becomes an issue when finishing is applied, in particular when internal features are present. Unconventional isotropic superfinishing processes could be a solution to this problem since they can generate a low surface roughness on complex geometries. However, the performance characteristics, with regard to the environmental sustainability and economic aspects, need to be evaluated since they are key factors that must be considered for decision-support tools when selecting a finishing process. The technological feasibility of the isotropic superfinishing (ISF) process, applied to Ti-6Al-4V parts produced by electron beam melting, is investigated in this paper by considering the dimensional and geometrical deviations induced by the finishing treatment, and from observations of the surface morphology. A significant reduction in surface roughness, Sa, to around 4 μm, has been observed on the most irregular surfaces, although the original shape is maintained. Environmental sustainability has been analyzed for all the manufacturing steps, from powder production to part fabrication, to the finishing process, and both the cumulative energy demand and material waste have been accounted for. The economic impact of the whole manufacturing chain has been evaluated, and the advantages of the ISF process are pointed out.
Highlights
It is generally considered that production is moving toward mass customization, and additive manufacturing (AM) technologies may be the key to satisfying both the customization and productivity demands
Once the technological feasibility of the electron beam melting (EBM) + isotropic superfinishing (ISF) integrated manufacturing approach had been verified, the results of the cradle-to-gate environmental and economic assessment are given in Sections 3.2 and 3.3, respectively
The asbuilt parts were smaller than the nominal ones, since the scaling factors used to compensate for temperature shrinkage were not considered in the building preparation
Summary
It is generally considered that production is moving toward mass customization, and additive manufacturing (AM) technologies may be the key to satisfying both the customization and productivity demands. L-PBF parts may include intricate internal channels and present the lowest roughness and best accuracy, but they are distinguished by high thermal gradients generated during the manufacturing process. High residual stresses which limit the materials that can be processed are developed and the need for support structures and the adoption of specific design rules increases. EB-PBF parts are almost stress-free, the productivity is higher than that of L-PBF, but the surface quality is poorer, and the high temperatures reached during the process (which cause the unmelted powder to form a partially sintered powder cake) limit the geometry of inlets, due to the difficulty of removing the internal powder. DED processes were the first technologies to be introduced onto the market, and they are excellent for repairing high-value parts; the surface finish is very rough and tolerances are large.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
