An Error-Correcting Code-Based Robust Watermarking Scheme for Stereolithographic Files

Stereolithographic(STL)files have been extensively used in rapid prototyping industries as well as many other fields as watermarking algorithms to secure intellectual property and protect three-dimensional models from theft.However,to the best of our knowledge,few studies have looked at how watermarking can resist attacks that involve vertex-reordering.Here,we present a lossless and robust watermarking scheme for STL files to protect against vertexreordering attacks.Specifically,we designed a novel error-correcting code(ECC)that can correct the error of any one-bit in a bitstream by inserting several check digits.In addition,ECC is designed to make use of redundant information according to the characteristics of STL files,which introduces further robustness for defense against attacks.No modifications are made to the geometric information of the three-dimensional model,which respects the requirements of a highprecision model.The experimental results show that the proposed watermarking scheme can survive numerous kinds of attack,including rotation,scaling and translation(RST),facet reordering,and vertex-reordering attacks.

Quantitative characterization of defects in stereolithographic additive manufactured ceramic using X-ray computed tomography

Ceramics have been widely fabricated by additive manufacturing(AM).Compared to conventional technologies,the strength of additive manufactured ceramic is relatively low owing to the formation of defects during manufacturing process.These defects have significant effects on the microstructure and mechanical properties of additive manufactured ceramics.However,systematic research on defects,including defect geometrical features,quantitative statistics,and formation mechanism,as well as the intrinsic relationship with mechanical properties,need to be studied in depth.In this work,Al2 O3 ceramics were prepared from photosensitive slurries with different solid loadings by using stereolithographic(SL)additive manufacturing.The defects,including their sizes and distributions,in both green and sintered bodies were investigated by using scanning electron microscopy(SEM)and X-ray computed tomography(X-CT).Geometrical features and quantitative statistics of the defects were evaluated and discussed to reveal their formation mechanism.Moreover,the intrinsic relationship between defects and mechanical properties of the additive manufactured ceramic was revealed.This study can give some fundamental understanding of the defects in additive manufactured ceramics.

Recent advances in the stereolithographic three-dimensional printing of ceramic cores: Challenges and prospects

The increasing demand for geometrically complex structures—specifically, higher-inlet-temperature turbine blades for the fifth-generation or other high-generation machines of advanced fighter aircrafts—hasmade the development of more complex double-walled three-layer hollow-cavity structures a necessity.However, this requires the preparation of complex ceramic cores and advanced, integrated technologies.Stereolithographic three-dimensional printing (SLA-3DP) technology, with digital control upon materialmorphology, composition, and structure, is a high integration and versatile technique that is superior tothe traditional manufacturing techniques for ceramic cores, including gel casting, injection molding, andhot pressing. The latent capacity of this technique is contingent on the progress of processing routesthat significantly reduce the distortion and defect formation in response to the elimination of the reactedorganic monomer phase during photo-curing. Despite the tremendous progress in the field, multiple challenges remain, such as the preparation of high-solid-content and low-viscosity suspensions, SLA-3DP oflarge double-walled ceramic cores with complex structures, and process optimization and sinter strengthening for the fabrication of ceramic cores. These challenges have prevented the broader applications andreduced the impact of the SLA-3DP technology. This review discusses cutting-edge research on the crucialfactors governing this production method. Specifically, we outline the existing challenges within the fieldand provide our perspective on the upcoming research work and progress.