Study Of Powder Feeding System For Laser Cladding

Laser cladding is a technology of depositing material. Through the process,a powdered or wire feedstock material is melted, and in order to coat part of a substrate or fabricate a near-net shape part laser was used. It is a combined technology of laser, mechanics and electronics. It has broad prospects for development.To improve the stability of powder feeding rate and3D laser remanufacturing, this paper researched the powder flow based on gas-solid two phases flow theory. On this basis, a capacitive measurement system and a photoelectric measurement system were designed. The resolution of each measurement system through the experiment and theoretical was compared. At last, according to calibrating experiment and unstable experiment, a strategy of powder feeding rate control system was designed. This paper researched coaxial powder feeding model, and used COMSOL Multi-physics to simulate the nozzle of feeder, than got the distribution condition of gas.There are some conclusions through experiments and simulation:(1)According to the experiments’results, resolution of photoelectric measurement system was0.1g/min, meanwhile capacitive measurement system’s resolution was5g/min. Then analyzed the reason of different resolutions:in the same situation, the variation of metal powders’mass concentration is significantly greater than the variation of powders’ volume concentration. And capacitive measurement system measured the changes in volume fraction which changed little, as well as photoelectric measurement system measured the concentration which changed more greatly. Therefore photoelectric measurement system has higher resolution. And the powder conveying control system which based on the photoelectric sensor has high feeding precision.(2)After gas spurted from nozzle, it didn’t converge entirely along the direction of the nozzle angle, but more tended to flow to the lateral. The existence of substrate and cladding layer changed the gas flow converge state. The closer from the gas vent the less influence between cladding layer and gas flow. Gas flow velocity field within the scope of distribution in space which influenced by the cladding layer is not symmetrical, or uniform. Above the cladding layer the gas flow was smaller.This paper introduces the design of photoelectric powder concentration measurement system. It can provide reliable experimental methods of precise control and feeding quality testing for the powder feeding system. In addition, numerical simulation provided references to laser focal length and the distance parameters between nozzle and workpiece. And it also provides technical foundation to optimize coupling temperature field, stress field, the parameters of nozzle, and more accurate simulation.