Study On Superslippery Surface Preparation And Its Application In Constrained Dlp Continuous Forming Process

The development trend of 3D printing technology from rapid prototyping to direct manufacturing of functional parts puts forward higher requirements for molding speed.The forming efficiency of the constrained Digital Light Procession(DLP)can meet the requirement of efficiency in direct manufacturing of functional parts.However,the adhesive force between the cured layer and the constrained substrate is too large,which leads to the failure of the cured layer in repeated peeling.Aiming at the interface adhesion problem between substrate and solidified layer,this paper proposes a method to reduce adhesion force by using ultra-slippery surface,and studies the law and mechanism of influence of ultra-slippery surface preparation technology and microscopic characteristics of substrate on light transmittance and adhesion force.The main work and research conclusions include:(1)Considering the requirements of the substrate for light transmittance and support stiffness,quartz glass was selected as the substrate material,and the ultra-slippery surface was prepared based on quartz glass wet etching and surface treatment.By contrast test,sodium acetate and sodium bicarbonate were selected as etch agents,and the law of the influence of process parameters such as temperature and etch time on the morphology of glass surf-ace was studied.The formation mechanism of the morphology was analyzed based on the results of the hydrothermal reaction kinetics of glass,and the optimal temperature(160℃)and time(16 h)parameters for the surface morphology of quartz were obtained.In order to solve the problem of insufficient bonding force between glass substrate and lubricating oil,a suitable silane coupling agent is used to treat the surface of the substrate,and the bonding force between lubricating oil and substrate is enhanced by the hydrolysis and similarity compatibility of silane coupling agent.(2)The finite Difference Time domain software Finite Difference Time Domainmethod(FDTD)was used to numerically simulate the law of the influence of the microscopic characteristics of the substrate on the light transmittance.Combined with the experimental measurement of the light transmittance,the influence of various factors on the light intensity distribution and the light transmittance of the forming area was studied.The results show that the light intensity distribution in the curing molding area is affected by the depth,area ratio and pore size,and thus the curing dimensional precision and uniformity.The influence on the light intensity distribution uniformity can be reduced by reducing the size of the pores,increasing the area ratio or the lubricating liquid with the same refractive index as the substrate.The light transmittance of the sample before and after surface treatment,at different etching temperatures and at different etching times was studied.The results showed that the light transmittance of the sample was decreased after hydrophobic treatment,while the light transmittance was significantly improved after the injection of lubricant because the difference of refractive index of the material was reduced.The transmittance decreases with the increase of reaction temperature and time.(3)A test bench was built to obtain the parameters required for numerical simulation.The evolution process of adhesive force during the stripping of the solidified layer from the super-slippery substrate and Polydimethylsiloxane(PDMS)film substrate was experimentally measured.The cohesive force model parameters were obtained according to the adhesive contact theory and bilinear cohesion model fitting.On this basis,a simulation model was established to study the effects of different microscopic parameters(pore size,hole depth and area ratio)on the adhesion of the superslippery surface.The results show that the micropore area ratio significantly affects the adhesive force during separation,and the extreme value of adhesive force has an approximate positive relationship with the area ratio.The pore size will affect the peak of adhesive force in different degree.The pore depth has an effect on the peak time of adhesion force,and the separation time increases with the increase of pore depth.Small pore size,large pore depth and large area ratio are conducive to reducing the adhesion between the cured layer and the constrained substrate during separation.