Additive Manufacturing of Optically Translucent Parts

A lithophane is a translucent image created by varying the plate thickness; the image is observed using a back lit light source. Additive manufacturing makes highly complex lithophane fabrication possible. Optical properties of laser sintered polyamide (PA) 12 translucent additive manufactured parts were analyzed and applied to the lithophane fabrication. Several parameters affecting lithophane manufacturing performance are discussed including brightness and contrast versus plate thickness and grayscale level, surface finish quality and manufacturing orientation. Moreover, other thermoplastic semi-crystalline materials were analyzed for LS optically translucent part production. Plates and lithophanes were built using a different AM platform: stereolithography (SL) with Somos® ProtoGen™ O- XT 18420 white resin. Different optical properties and lithophane performance were observed and compared with PA 12 parts. It was found laser sintered polyamide 12 optical properties varied with light wavelength and reached maximum transmission under green light. When building in the XY plane, thin layer thickness and large maximum plate thickness led to higher contrast and gray scale level. Lithophane quality was largely improved when fabricated in the ZX/ZY plane orientation. Lithophanes made from SL were analyzed but showed lower contrast due to the optical property characteristics of the white resin.