Ignat'ev UDC 621.762 A vibrating powder feeder that makes it possible to deposit powder in a laser sintering zone in a continuous flow or in discrete portions has been developed. The dependence of the rate of flow of the powder on the rate of the vibrations, the parameters of the construction of the feeder, and the properties of the powder is investigated. The possibility of regulating the process of deposition of the powder is considered.Selective laser sintering is one of the most promising types of rapid prototyping technologies [1C6]. An important aspect of laser sintering processes is that powder is fed into the zone affected by the laser effect [7], since the features of the deposition and the properties of the powder layers exert a direct influence on the conditions of subsequent sintering of the powders and, as a consequence, on the structure of the multilayer article.The creation of contact between adjacent layers (sintering of layers to each other) becomes possible provided that H/h > 1, where h is the thickness of the deposited powder layer and H is the depth of the laser sintering zone [2], With increasing value of the ratio H/h (that is, with increasing H or decreasing h), the strength of the contact grows, and the structure becomes more homogeneous. The depth of the laser sintering zone H increases with increasing radiation power density Q and duration of treatment t. Any increase in Q or t is limited due to the potential for uncontrolled development of the Bolling process, which leads to complete fusion of the powder [6]. Therefore, decreasing h is more preferable. Decreasing h to the minimally possible values (ideally, deposition of monolayers of particles) is especially desirable if finely dispersed powders are employed. However, due to the functional features of the powder delivery systems that are traditionally employed for selective laser sintering, the potential for decreasing h is also rather limited. As a rule, the design of these systems is based on scrapers, rotating rollers, or gap hoppers [7]. To deposit thin layers it is necessary to create a small gap between the lower elements of the systems that directly form the layer and the platform (or previously deposited layer), a result that it is not always possible to achieve in practice due to the insufficiently high precision with which the systems function. Moreover, as a result of mechanical interaction of the lower elements of the systems with the powder layer thus formed, shift effects often arise that prevent the formation of a layer of the same thickness.The use of systems that permit deposition of finely dispersed powder in a continuous flow or in strictly controlled portions by remote means (the powder is fed from a feeding system that does not have any direct contact with the layer being formed) proves to be more efficient. For these purposes hopper-type powder feeders situated at some distance above the platform (or previously deposited layer) to enable the particles that are exiting the hopper to freely fall under the action of...
Ignat'ev UDC 621.762 A vibrating powder feeder that makes it possible to deposit powder in a laser sintering zone in a continuous flow or in discrete portions has been developed. The dependence of the rate of flow of the powder on the rate of the vibrations, the parameters of the construction of the feeder, and the properties of the powder is investigated. The possibility of regulating the process of deposition of the powder is considered.
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