Development And Technology Research Of Premelt Nozzle FDM Molding Equipment

3D printing technology originated in the 1980 s,also known as add-on manufacturing or rapid prototyping technology.Based on the digital model file,it uses discrete materials(wire,powder,liquid,sheet,plate,etc.)to produce arbitrary complex shape entity layer by layer.This technology has the characteristics of short production cycle and low cost.According to the forming process,3D printing can be divided into fused deposition molding(FDM),stereo light curing forming(SLA),selective laser sintering forming(SLS),laminated solid manufacturing(LOM)and so on.Among them,FDM technology has the advantages of high material utilization,low cost and simple operation,so it has the most extensive application.Due to the forming characteristics of FDM,the mechanical properties of the formed specimens are anisotropic: the mechanical strength along the scanning direction of the specimens is much higher than the interlaminar bond strength perpendicular to the forming direction.In the actual industrial application,the force situation of parts is complex and changeable,so it needs to be balanced in all directions.Therefore,improving the overall mechanical properties of formed parts is the key problem of FDM technology in practical industrial applications.Firstly,according to the principle of FDM polymer forming,the forming process of interlayer pre-melting was proposed,and the pre-melting sprinkler device was designed with thermal simulation to achieve the control of interlayer pre-melting temperature.The effect of the pre-melting temperature of the printing layer on the interlayer bonding and mechanical properties of PLA vertical printing parts during FDM printing process was investigated by means of experiment and comparison of the samples with the reference of PLA horizontal printing parts.The results show that with the increase of pre-melting temperature,the maximum tensile strength of PLA vertical printed specimens increases first and then decreases.The maximum tensile strength of PLA vertical printed specimens reaches the maximum when the preheated sheet temperature is 80 C.The average tensile strength of PLA vertical printed specimens reaches 89.1% of that of horizontal printed specimens,while the mechanical properties of PLA vertical printed specimens without preheating only reach 66.9% of that of horizontal printed specimens.Secondly,through independent factor test,the effect of traditional heat treatment process on the mechanical properties of vertical printed specimens is compared horizontally.The experimental data show that the interlaminar pre-melting process is superior to the traditional heat treatment process in improving the interlaminar bonding force of PLA printed parts.Finally,combined with experimental data and process exploration,the FDM forming equipment integrated with pre-melting nozzle was developed.Design and optimize the pre-melting device,equipment to achieve global pre-melting temperature control;develop and design follow-up collector to achieve the concentration of pre-melting temperature and high temperature area,reduce heat loss and maintain the stability of pre-melting temperature;design and develop closed thermal insulation chamber,construct the isolation of temperature area,reduce the internal working temperature and heat conduction of room temperature environment,achieve the appropriate man-machine interaction environment temperature.Build equipment heat dissipation device,hardware system,complete the design and construction of the whole machine,the global pre-melting temperature can reach up to 200 degrees Celsius,the equipment can be adapted to the printing market can see most engineering plastic.