The Study On Laser Rapid Prototyping Powder Feeding System’s Key Technology

Laser metallic rapid prototyping technology, based on laser rapid prototyping(RP) and laser cladding technique and combined with mixes mechanism precision transmission, numerical control technique, computer technique,laser technique, materials science and sense technology, and many other subjects, is becoming high-precision and enviromental technique recent years. Laser rapid prototyping technology has been payed high attention by home and abroad scholars from the very beginning since its unique advantage. At present, it has become a hot issue in the field of laser processing. High energy laser beam can melt metal surface partially and form a weld pool, at the same time, the metal material was sent sideways or coaxially into the pool and form metallurgical bonding with substrate metal. Laser metallic rapid prototyping technology is three dimensional laser cladding technology under the control of computer in essence. Powder feeding system is the key of laser rapid prototyping technique, which include synchronous powder feeder,nozzle for Laser coaxial feed powder, powder mixer and powder segregator. Existing powder feeding system has some problems such as unstable and asymmetical feeding, poor powder convergence, low powder utilization ratio and temperature distortion on nozzle after long time work, etc. Therefore, it has important significance to design and improve powder feeding system.The present powder feeder has some disadvantages such as difficult to feed fine powde. To solve this problem, a new scraper suction feeder is designed based on the theory of Gas-Solid Two-Phase Flow.The process of designing coaxial powder feeding is as follows. Firstly,multiple feeding access structural parameters are planned.Combining the characteristic of Gas-Solid Two-Phase Flow of powder flow field of coaxial feeding powder, the powder flow field was simulated by FLUENT software. Based on the analysed results, the preferred plan is selected finally. Secendly, the nozzle cooling system is designed, and then the cooling effect of nozzle is analysed by FLUENT software. Thirdly, the structure of powder mixer and powder segregator are designed based on finite element analysis and Gas-Solid Two-phase Flow theory. Finally, the flow field of powder feeding nozzle is simulated by FLUENT software under different powder feeding parameters and different powder physical property and then the flow field of feeding mixed power is also analyzed under the same conditions.To determine the feeding stability, scope of application of powder feeder, and powder convergence of nozzle of coaxial feeding powder, pneumatic powder feeding experiment is made and analysed.At last, laser metallic rapid prototyping system is set up by the designed powder feeding system and other existing equipments. And then an experiment is carried out for wear-resistant titanium-based functionally graded materials on this system. The macroscopic and microscopic morphology of the sample got from this experiment are observed and analyzed and the powder utilization ratio is calculated.