Abstract
Powder bed additive manufacturing allows for the production of fully customizable parts and is of great interest for industrial applications. However, the repeatability of the parts and the uniformity of the mechanical properties are still an issue. More specifically, the physical mechanism of the spreading process of the powders, which significantly affects the characteristics of the final part, is not completely understood. In powder bed fusion technologies, the spreading is performed by a device, typically a roller or a blade, that collects the powders from the feedstock and successively deposits them in a layer of several dozens of microns that is then processed with a laser beam. In this work, an experimental approach is developed and employed to study the powder spreading process and analyze in detail the motion of the powders from the accumulation zone to the deposition stage. The presented experiments are carried out on a home-made device that reproduces the spreading process and enables the measurement of the characteristics of the powder bed. Furthermore, the correlation with the process parameters, e.g., the speed of the spreading device, is also investigated. These results can be used to obtain useful insights on the optimal window for the process parameters.
Highlights
In the latest years Laser Powder Bed Fusion (LPBF) has affirmed as the go to additive technology for the production of parts for critical applications in fields such as the aerospace and biotech industry [1]
In the author's opinion the reason for the dependence can be found in Spreading of Powders in Powder Bed Additive Manufacturing: an Experimental Approach the ratio between the layer thickness and the powder's maximum dimension
In this work an experimental approach for the characterization of the powder bed deposited in laser powder bed fusion (LPBF) technologies was presented and used to investigate the influence of the process parameters on said characteristics
Summary
In the latest years Laser Powder Bed Fusion (LPBF) has affirmed as the go to additive technology for the production of parts for critical applications in fields such as the aerospace and biotech industry [1]. It enables the production of fully customizable parts with respect to both the geometrical features and the mechanical properties. A powder bed with uneven characteristics (e.g., packing factor, powder size distribution, effective layer thickness) throughout its area makes it impossible to select the optimal value of the laser parameters (i.e., hatch spacing, power and so on) for the entirety of the printing chamber. A deeper understanding of the influence of the spreading parameters (i.e., recoating device's speed, layer thickness, the total quantity of powder to be spread for each layer) on the state of the powder bed can lead to a proper selection of the parameters in order to attain overall better characteristics of the finished part
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