Abstract :
[en] Additive manufacturing is feeding great hopes for future developments in fields such as aeronautical, biomedical and rapid tooling industries.
However, limitations are still restricting its use to make prototypes and hampering mass production. In the case of titanium alloy printing (e.g.
Ti6Al4V) with the EBM (Electron Beam Melting) process, the major obstacle to use parts directly after printing is their roughness (Arithmetic
Roughness (Ra) ~25 µm). Even if the parts are better regarding residual stresses than parts coming from other 3D printing processes, the high
roughness decreases their fatigue resistance. A set of parts were manufactured in Ti6Al4V by EBM process. Their characteristics in terms of
dimension (cylindricity and diameter) and surface (Arithmetic Roughness Ra and Total Roughness Rt) were evaluated directly after printing. The
average Rt stands at 96 µm e.g. The parts endorsed then a first chemical etching to remove the peaks and valleys on their surface. The average
Rt decreased at 90 µm e.g. Afterwards, a robotic machining was performed to remove a layer of 400 µm to reach the core material of the part.
The average Rt obtained was 5 µm e.g. Finally, a second chemical etching with the same parameters as the first was done. The average Rt
increased finally to 9 µm e.g. The same set of dimensional and surface measurements were made after each step of the experimental setup. The
succession of operations and measurements allows to compare the influence of conventional machining on the chemical finishing performed on
the parts. Furthermore, the machining emphasizes the apparition of surface defects due to the use of a robot (tessellation). Finally, a Rt degradation
and a surface finish change have been recorded after the second chemical etching. Perspectives can be focused on assessing these last observations
by repeating the experimental setup with more parts.
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