Study on machinability of additively manufactured and conventional titanium alloys in micro-milling process

Capability of Additive Manufacturing (AM) technology in the production of complex parts with high flexibility has led to the growing interest in their application as an alternative for conventional manufacturing processes. Despite the outstanding benefits of the AM process, due to their poor surface quality, the precision parts produced by this method generally need to be machined, ground, or polished. This paper addresses the machinability of AM Ti6Al4V titanium alloy parts in the micro-milling process with a specific focus on cutting forces, specific cutting energy, burr formation, and surface quality. Additive parts were produced by Electron Beam Melting (EBM) technique and were compared with the extruded Ti6Al4V parts in the micro-milling process. No significant difference could be observed in the cutting forces of both materials at chip thicknesses between 7.4 and 37.3 μm, despite the higher hardness of the EBM Ti6Al4V compared to the extruded Ti6Al4V. However, micro-milling of the EBM parts produced finer surfaces. Cutting forces and specific cutting energies of EBM parts were less than those of extruded parts at minimal chip thicknesses (lower than 7.4 μm). Continuous wavy-type burrs were formed in micro-milling of the EBM Ti6Al4V and were larger than those of extruded Ti6Al4V.     

Development of models for additively manufactured actuators using compliant Wren mechanism

Compliant Wren mechanisms (CWM) constitute specific compliant structures of particular interest. Derived from Wren mechanisms, they can exhibit a large variety of motions, from quasi translation to quasi rotation. In this paper, the development of models for the analysis and synthesis of CWM is considered. A kinematic model is introduced first to assess all possible motions when used as an actuator. Then the static model and stress expressions are derived to help their design. These derivations are achieved for two types of geometries, corresponding to the geometries of interest. CWM are filigree structures, whose manufacturing is difficult to consider without additive manufacturing. A specific work on their production using selective laser melting (SLM) is then achieved to ensure the reliability of their production. As a proof of concept, a pneumatically actuated component is then developed and tested. It is composed of two CWM of different geometries. It offers the possibility to obtain translation and rotation using a single pressure input. The developed models are investigated using finite element models and experiments using additively manufactured structures.     

Material jetting additive manufacturing: An experimental study using designed metrological benchmarks

Additive manufacturing (AM) technique allows the creation of parts with a high degree of design complexity by building three-dimensional (3D) parts layer-by-layer. Many of the current restrictions of design for manufacturing (DFM) as well as design for assembly (DFA) are no longer applicable for AM due to the lack of needs for tooling. Instead, it is critical to establish the manufacturing limits and design guidelines to achieve optimal production outcomes. This can be achieved through manipulation of process parameters.The purpose of this paper is to establish a systematic methodology for investigating the process capability of material jetting AM techniques by using specially designed benchmark artifacts. In this study, three customized benchmarks were designed to characterize and establish the process capability of material jetting AM techniques. Each of the benchmarks was designed for different purposes. Using a benchmark, metrological studies were conducted to determine the effect of process parameters on the dimensional accuracy of fabricated part. The design limitations on special features such as thin walls and assembly-free parts fabricated using different build orientations were also evaluated.