Study On Storey Dynamic Control Of Laser 3D Deposition Process Based On PMAC

The purpose of this study is to implement the dynamic control of single-storey height by adding hight detection devices in the existing three-dimensional laser processing systems. In order to overcome the rough topography of the forming parts and eliminate the phenomenon of jagged edge, we must make every storey have the same amount of defocus.In other words,we should ensure consistency between single-storey height-Δh and Z axis single-upgrade–ΔZ.In this paper,the present situation of closed-loop control technology on laser processing was summarized,especially the dynamic control of single-storey height.Two feasible schemes were proposed based on the analysis of single-storey height dynamic control of laser 3D deposition system.By comparing different schemes, the scheme with two computers,a master and a slave one,based on laser displacement sensor was adopted.As master computer,IPC is responsible for the opening of serial communication,building the communication with PMAC,data receiving and processing, the real-time adjustments of Z-axis as well as some auxiliary functions; SCM system as slave computer is responsible for A/D conversion and transferring data to IPC;Laser displacement sensor accomplished displacement parameter sampling as control variable detecting device.IPC and SCM comunicated by RS232.The adopted scheme took full advantage of the IPC powerful processing and computational capabilities and realized the advantage of programming easily,which implemented the integrating control by IPC.Three-dimensional laser prototyping process is a complex physical metallurgy process with the result of multi-parameter effects.the paper accomplished the displacement sampling by laser displacement sensor and overcome the difficulties of powder sputtering, plasma cloud and smoke transpiration above the measure point, Especially,under high-temperature, general displacement sensor can not accurately sample signal.The displacement measurement devices fulfill the task excellently.The project determine Z- axis movements by comparing the measured value with a given value.The follow-up comparison experiments indicated that:The movement of laser nozzle is within±0.3mm,in other words,the change height of single- storey is within±0.3mm; the shape quality and the geometrical accuracy by using storey height dynamic control was better than that of no use of storey height dynamic control.Forming parts has a smooth surface both inside and outside,also does not appear jagged. It effectively improves the stability of laser 3D deposition process and the quality of deposition parts.