Study On On-line Monitoring Of Robotized PAAM Process And Effect Of Interlayer Temperature On Bead Characteristics

Plasma arc additive manufacturing has unique advantages in rapid prototyping of dense metal structure because of the higher forming efficiency and density,and the forming precision and quality are two important factors affecting its development.For the above reasons,in this work an automatic interlayer temperature measuring and controlling system comprising software and hardware was developed to monitor the current,voltage,interlayer temperature and control the interlayer temperature during the plasma arc additive manufacturing(PAAM).And the impact of the interlayer temperature and the character of the parameters during deposition were investigated according to the deposited stainless straight wall.Firstly,a hardware of the measurement and control system consisted of current and voltage sensing module,infrared temperature sensing module,data acquisition card.conditioning circuit and control circuit was designed,developed and calibrated.A circuit protection module which can isolate the high voltage during deposition was designed to prevent the destruction of the components of the circuit.The measurement of interlayer temperature used the infrared sensing technology to detect the temperature information in real-time by the way of non-contact measurement and the controlling of interlayer temperature was achieved by means of designing the controlling method and circuit of interlayer temperature.Then the monitoring software designed two units of the data acquisition interface and data query interface was developed based on LabVIEW.The acquisition interface achieved the function of setting of the process card,parameters display,data analysis,data statistics,temperature feedback and data storage by the data analysis subroutine vi,state judgment subroutine vi.data statistics subroutine module and storage subroutine module.And the query interface achieved the function of data query,playback and statistics based on historical data query and the data processing subroutine.Afterwards this work carried out a series of stainless steel deposited straight wall experiment taking interlayer temperature as single variable based on self-developed plasma arc additive manufacturing system.What is more,a data measuring and controlling system designed by ourselves was adopted to measure and control the deposition process.Five sets of deposited straight wall whose interlayer temperature respectively was 60?.150?.250?.350?and a non-controlled temperature were got in the experiment which verified the stability and accuracy of the system.The experiment also researched the character of parameters.The rasearch drew the conclusion that the electric current in the deposition was stable,volta ge presented the increasing trend in the one-way deposition and gave a stable performance in the round-trip deposition for removing the difference of height and the cooling speed of deposition decreased with the increase of layers.At last,this work investigated the impact rule of interlayer temperature in PAAM.According to the research,keeping interlayer temperature the same has obvious effect on the molding surface and the uniformity of size,however no obvious controlling effect on stiffiness and grain size,and with the increase of interlayer temperature,the appearance of the forming surface becomes poor,the width of the layers increases,the grain size increases too,the microhardness and forming efficiency of the deposited layer decrease.When the interlayer temperature is 60 ?.the forming is the best but efficiency and when the interlayer temperature rises to 150,the forming quality is still good and the efficiency will improve a lot.So when other conditions keep the same,150 ? is the most appropriate interlayer temperature.