Study Of Size Detection And Control Of Molten Pool During Laser Cladding

Rapid prototyping by laser cladding is a kind of additive manufacturing technology that has developed rapidly in the past 40 years.It is a combination of laser cladding and rapid prototyping.Rapid prototyping is different from the traditional manufacturing methods.It is a bottom-up,layer-by-layer manufacturing process by adding material to the model.This technique has been used in various fields,such as auto industry,aerospace,etc.In laser cladding process,the quality of the cladding is affected by the processing parameters.Experiments shown that the temperature distribution and size of the molten pool,which will affect the quality of final parts,will change under different processing parameters.This make it possible to control the quality of parts by modifying the processing parameters according to the states of the molten pool.Because of the characteristics of high temperature,high brightness,small size,etc.The detection of molten pool is relatively difficulty.This paper designed a dual-color CCD coaxial molten pool monitor device and a PID based control system which can detect the exact position of the molten pool and obtain a clear and complete image of molten pool surface,and make a close-loop controlling of the width of the molten pool.The accuracy of the detection device was verified by numerical simulations and experimental measurements using infrared thermometer.In order to quickly and effectively obtain the molten pool area information and control it,the paper used image algorithms such as threshold segmentation,edge detection and minimum circumscribed rectangle to obtain the size information of the molten pool quickly and accurately,and designed a closed-loop control software for controlling the molten pool size through adjusting the laser power.The experimental results show that the CCD coaxial shooting method and the molten pool width closed-loop control system effectively solve the problems of edge protrusion,bending depression and uneven width of the thin-walled workpiece under laser reciprocating scanning.Using this system can improve the forming quality of the piece.