Investigating the melt pool properties and thermal effects of multi-laser diode area melting

Diode area melting (DAM) is a new additive manufacturing process that utilises customised architectural arrays of low-power laser diode emitters for high-speed parallel processing of metallic feedstock. The laser diodes operate at shorter laser wavelengths (808 nm) than conventional SLM fibre lasers (1064 nm) theoretically enabling more efficient energy absorption for specific materials. This investigation presents the first work investigating the melt pool properties and thermal effects of the multi-laser DAM process, modelling generated melt pools the unique thermal profiles created along a powder bed during processing. Using this approach process, optimisation can be improved by analysing this thermal temperature distribution, targeting processing conditions that induce full melting for variable powder layer thicknesses. In this work, the developed thermal model simulates the DAM processing of 316L stainless steel and is validated with experimental trials. The simulation indicates that multi-laser DAM methodology can reduce residual stress formation compared to the single point laser scanning methods used during selective laser melting

Tailoring the thermal conductivity of the powder bed in Electron Beam Melting (EBM) Additive Manufacturing

Metallic powder bed additive manufacturing is capable of producing complex, functional parts by repeatedly depositing thin layers of powder particles atop of each other whilst selectively melting the corresponding part cross-section into each layer. A weakness with this approach arises when melting overhanging features, which have no prior melted material directly beneath them. This is due to the lower thermal conductivity of the powder relative to solid material, which as a result leads to an accumulation of heat and thus distortion. The Electron Beam Melting (EBM) process alleviates this to some extent as the powder must first be sintered (by the beam itself) before it is melted, which results in the added benefit of increasing the thermal conductivity. This study thus sought to investigate to what extent the thermal conductivity of local regions in a titanium Ti-6Al-4V powder bed could be varied by imparting more energy from the beam. Thermal diffusivity and density measurements were taken of the resulting sintered samples, which ranged from being loosely to very well consolidated. It was found that the calculated thermal conductivity at two temperatures, 40 and 730 °C, was more than doubled over the range of input energies explored

New applications of rapid prototyping and rapid manufacturing (RP/RM) technologies for space instrumentation

In the frame of a research project, CRIF, KUL and CSL have investigated the possibility to use rapid prototyping and rapid manufacturing (RP/RM) techniques during space instrument development. Rapid prototyping and rapid manufacturing terms gather several techniques with the common baseline that parts are built layer by layer, starting from a CAD model. These techniques imply powder, paste or liquid and are applicable to polymers, ceramics and metals. In a first step, the major advantages of these techniques have been presented to Belgian industries implied in the space sector and, as a result of the discussions, development goals for the project have been identified. Several types of use have also been pointed, from demonstration mock-up to real space hardware. In parallel to technical developments, several case studies and tests have been performed. The case studies have shown that the rapid manufacturing allows complex geometries to be created. A drastic decrease of the number of separate parts and bolted junctions ease the predictability of the mechanical and thermal behaviour and limit the risk of imperfect junction. As a result of the project, a guidelines document has been issued to give as much information as possible on how to perform a space instrument design using the advantages of RP/RM techniques

Academic entrepreneurship and institutional change in historical perspective

none4siThis article provides a historical perspective on academic entrepreneurship and its role in institutional change, and serves as an introduction to a special issue devoted to the subject. Unlike approaches that define academic entrepreneurship narrowly as the commercialization of academic research, we argue that historical research and reasoning justify a broader conceptualization focused on the pursuit of future forms of value in academic knowledge production, application, and transmission. Understood in this way, academic entrepreneurship has long been a significant driver of institutional change, not only within the academic world but also in shaping the organization of markets and states. The article develops this argument in three major sections. First, it draws out themes implicit within the historiography of science and technology that highlight the role of entrepreneurship in reshaping academia and its relationship to society. Second, it establishes conceptual foundations for more explicitly examining the processes by which academic entrepreneurship acted as a driver of institutional change. Finally, it synthesizes the findings of the articles in the special issue pertaining to these entrepreneurial processes. The article concludes by arguing for the role of history in rethinking academic entrepreneurship in our own time, and by outlining directions for further research.openWadhwani, R. Daniel*; Galvez-Behar, Gabriel; Mercelis, Joris; Guagnini, AnnaWadhwani, R. Daniel*; Galvez-Behar, Gabriel; Mercelis, Joris; Guagnini, Ann