Study On Optimization Of Powder Feeding System In Laser Manufacturing Technology

Powder feeding system is a key component of the laser manufacturing system,of which,powder feeder and powder feeding nozzle are considered as the core and key links of the whole powder feeding system.The two parts are required to complete the quantitative output and accurate delivery of powder,which play an important effect on the quality and efficiency of laser manufacturing.In this paper,it regards the fluidized bed based powder feeder and the broadband powder feeding nozzle as the main research objects after analyzing the current research situation of the powder feeding system,in order to perform optimization and improvement on the powder feeding system of laser manufacturing.The fluidized bed based powder feeder has unique advantages compared with other mechanical powder feeders,and it also has wide application and promotional value in laser manufacturing field.However,the fluidized bed based powder feeder also has the disadvantage of insufficient reliability,so in this paper,current-flow electrical proportional valve is used to replace the original voltage-pressure proportional valve for regulating the feeding rate.Based on the analysis of the structure and principle of the fluidized bed based powder feeder,it starts from two key structures,namely the feeding hole and overflow outlet.Besides,corresponding optimized experiment is also designed to obtain a better diameter of feeding hole and opening parameters of overflow outlet.Under the optimized structural parameters,the current-flow proportional valve is used to carry out the powder feeding test on the fluidized bed based powder feeder.The results show that: when the input current value is between 60 mA to 70 mA,the rate of powder feeding is between 4.7g / min to 24 g / min;and there is a good linear relationship between the input current and the rate of powder feeding;in addition,the standard deviation coefficient of the feed rate fluctuation is less than 5%,indicating that the valve has an excellent stability concerning powder feeding rate control on the fluidized bed based powder feeder.The broadband powder feeding nozzle is one of the key technologies used in laser broadband cladding.Currently,the broadband powder feeding nozzle has the flaws of large powder output divergence and the low effective utilization rate.In this paper,according to the gas-solid two-phase flow theory,it analyzes that the following two aspects have caused the powder divergence: firstly,the powder is subject to the turbulence of carrier gas in the process of powder transporting;secondly,powder is subject to the turbulent diffusion effect of carrier gas when the powder outputs from the outlet.In order to solve the above problems,two improved nozzles are designed in this paper: one is a nozzle with double-side rectified protection gas,its principle is to reduce the turbulence intensity of outlet carrier gas by adding rectifying gas;the other one is gas leaking nozzle with window shape,its principle is to reduce the disturbance effect of carrier gas on the powder by removing carrier gas.In the following,the FLUENT software is adopted to conduct numerical simulation on the structure of above two kinds of nozzles,respectively.By analyzing the simulation results,a kind of gas leaking nozzle structure with lower side rectifying gas is designed.The structure removes the carrier gas,but also adds lower side rectifying gas to rectify the output powder beam.In the end,the powder feeding test and the laser cladding experiment are carried out on the nozzle body.The results show that: the gas leaking nozzle structure with lower side rectifying gas can effectively improve the convergence of the output powder.Compared with the conventional structure,the powder effective utilization rate has increased from less than 50% to 76%,and the desired design goal has been achieved.