| Constrained surface exposure molding can complete the production of one level of parts at a time,thereby greatly improving the molding efficiency.At the same time,this technology has the characteristics of high material utilization rate,high molding accuracy and simple equipment structure,etc.,and has become the key development direction of light curing molding.The main problem of the process is that the separation force of the cured layer is too large when the self-constrained substrate peels off during the molding process,which is easy to cause peeling failure,which limits the production,printing speed and reliability of the process of large-section parts.Aiming at the problem of excessive separation force,this thesis proposes to use the intrinsic lyophobic characteristic PDMS film with microstructure array as the constrained substrate to reduce the separation force during the separation process,and the rule that the separation force of the solidified layer is affected by the microstructure characteristics based on the cohesion model Numerical simulations were carried out,and PDMS films with different microstructural feature arrays were prepared,and the theoretical research conclusions and the scheme of the paper were verified by printing experiments.The main work and conclusions are as follows:(1)A test platform including a light source projection system,a mechanical structure system,a control system and a separation force measurement system was built,and the separation force under different contact shapes of the solidified layer-substrate interface such as circles,squares,and triangles was tested and measured Based on the method proposed in this paper to estimate the bilinear cohesive constitutive parameters,the cohesive constitutive parameters of the PDMS film with microstructure array as the constrained substrate were determined.(2)Using the ABAQUS finite element analysis software,the bilinear cohesive constitutive model was used to numerically simulate the separation process of the cured layer from the substrate,and explored the different microstructure characteristics(shape,area ratio,height)to the separation process influences.The results show that the peak adhesion force decreases with the increase of the thickness of the PDMS film;compared with the smooth release film,the PDMS film with a microstructure array can significantly reduce the adhesion force;of the three microstructure shapes,the triangular microstructure has the most Excellent anti-adhesion effect;the area ratio of the microstructure array has a significant effect on the adhesion force.The adhesion force increases with the increase of the area ratio,and the height of the microstructure has little effect on the adhesion force.(3)Using photolithography+ICP etching method to prepare silicon molds with different microstructure array features,through micro-molding process and surface treatment to prepare a liquid-repellent PDMS film with different microstructure array features,and its surface The lyophobic properties and light transmittance were characterized.Using the prepared microstructure array PDMS film as a constrained substrate,a 3D printing test was carried out,and the separation force of the cured layer from the substrate was measured.The results showed that when the microstructure shape was triangular,the area was 20 ?m2,the spacing was 15 ?m,and the height was at 10?m,it has the best effect of reducing the separation force. |
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