Research Of An UV Cured Support Material And Forming Process For Three Dimensional Printing

Three Dimensional Printing(3DP) is a new technology for Rapid Prototyping(RP)industry, which works by building parts in layers, is a progress used for the building upof three dimensional printing models from a CAD model. Thus, Three DimensionalPrinting system has many advantages, such as low cost, short period, easy modification,dimensional stability and so on.Ultraviolet(UV) 3DP bases on droplet jetting and ultraviolet curing. UV 3DP has notonly advantages of droplet jetting, but also of advantages of ultraviolet curing. Its formingaccuracy is the highest among all the methods of 3DP, and the efficiency of forming isgreatly increased because of fast forming. So UV 3DP has a vast range of applications forthe new product development. The forming materials for UV 3DP are divided intobuilding material(BM) and support material(SM). The model is produced from a buildingmaterial, the support material is dispensed in locations where building material is absent,holding the liquid building material in place until being cured. At the conclusion of themodel production, the support material is to be disposed without spoiling the model.In this paper, an UV curable support material pre-polymer for three dimensionalprinting was prepared based on the synergistic effect between PEO-PPO-PEO tri-blockcopolymer(F127) and polyethylene glycol 400 di-acrylate(SR344).Firstly, the jetting conditions of pre-polymer were discussed. The effect of variouscomponents and temperature on viscosity and surface tension was studied, then jettingprogress of support material pre-polymer were recorded by Dixtimat Material Printer2800, the effect of bubble on jetting was investigated, and the various factors on pHvalue, volatilizing rate and conductivity were studied. The experimental results indicatethat when viscosity is 8～12cps, surface tension is 25～40n/m, pH is 7～8.5, salt content islower than 0.5%, the pre-polymer could be jetted out from the print-head. Secondly, the curing mechanism of support material was studied. The gel propertiesof support material, gel thermodynamic of support material, self heating in photo-curingreaction and based on the synergistic effect between F127 and SR344 were investigated.The IR spectra of compounds F127, SR344 and the final curing product of supportmaterial were reported. The result shows that SR344 was grafted to the F127.In the same time, the effects of various components and conditions of formingtechnology on jetting stability and curing rate were discussed, which can providereferences for selecting and optimizing 3DP's material mixtures and process parameter.Lastly, the property of UV curable support material for three dimensional printing,forming precision and removed conditions of SM were investigated. The effects ofvarious components and conditions of forming technology on mechanical properties,water absorption, Solubility, shrinkage and surface morphology of support materials werestudied. The contact angle for pre-polymer on building material and support materialwere test, and the spreading coefficients were figured out, respectively. Then the contactsurface profile of support material to building material was investigated by SEM. Theresult shows that the forming precision of building model was improved; furthermore,the support material could be removed easily from building model without spoiling themodel.