Arsenii Rak, Pavel Kondrashev

Introduction. The influence of the system that generates the flow of gas-powder mixture in the area of focus of laser radiation on the quality and performance of laser surfacing and the Rapid Prototyping technology has been cited by many authors [1]. Obviously, when implementing the Rapid Prototyping process, in the scheme of powder injection into the laser focus spot, it is most expedient to use the scheme when the powder mixture is fed coaxially to the axis of focused laser radiation. This is explained by the fact that in the ordinary laser surfacing, on the surface of the workpiece, the focused laser beam moves in a constant law, covering a predetermined area. This allows you to install the powder delivery system at a predetermined angle by applying a powder jet to a predetermined location [1]; When implementing Rapid Prototyping technology, the focused laser beam moves along any predefined trajectory, realizing a vector processing scheme or a combination of plane and vector processing simultaneously. That is, to implement the process requires a powder delivery system or equipped with an additional multi-coordinate actuator (with control system), which significantly complicates the design. Or to ensure a stable (independent of the direction of motion focused radiation) flow of powder into the treatment area in the form of a circle (spot), due to a simple design solution [1]. Usually simple engineering dependencies are used to calculate coaxial nozzles [2, 3], which do not allow, for example, to determine the distribution of the powder concentration in the treatment zone, its interaction with the shielding gas, and others. For this reason, numerical modeling of the process of handling a powder mixture that is fed into the area of focus of laser radiation allows to create optimal designs of nozzles is an urgent task. The modeling of the process of handling the powder mixture, which is fed into the area of focus of laser radiation through coaxial nozzles (which have different designs) was performed using the Euler model. Subsequently, for various designs of the nozzles involved in the calculations, experimental studies were carried out (using a gas pipeline through-pass dispenser) fixing (using a digital camera) a gas powder jet that was matched to the obtained one by numerical simulation.

Conclusions

-it is established that numerical simulation of the process of transport of powder particles in the gas stream allows to design coaxial nozzles and to determine in advance the treatment schemes, under any law of movement of the focused beam;

-changing the geometry of the nozzle angles is a very effective factor in influencing the spatial distribution of the powder flow, namely, changes in the focal plane of the powder concentration and the shape of the flow caustic;