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The challenges associated with stereolithography-based ceramic additive manufacturing using high solid loading pastes are related to the printability of ultrathin layers and complex green bodies without auxiliary support structures directly underneath. In order to develop the strategy of conformal contactless support during additive manufacturing, the printability of alumina ceramic paste with a variety of solid loading, along with mechanical properties of the sintered parts fabricated by stereolithography process was investigated. A combination of scanning electron microscopy, micro-computed tomography scans and three-point bending tests were practiced systematically. The rheological behavior of ceramic paste was regulated distinctly by solid loading. As the solid loading increased, the degree of shrinkage decreased and the relative density increased for the sintered part. The sintered sample from 52 vol% ceramic paste presented the highest flexural strength with well densified microstructure. The research results promote property optimization of ceramic components fabricated by stereolithography method through material compositions and printability of ceramic paste, which simultaneously contributes to perfect support strategy for ceramic additive manufacturing.

Complete removal of uncured ceramic paste from the surface of a green body with complex profiles fabricated by stereolithography-based additive manufacturing is critical to the ultimate achievement of the designed 3D part with high definition and ideal surface roughness. The present work provided a novel cleaning strategy for the design of cleaning agents on the basis of competitive absorption of viscosity-reducing dispersants on the surface of ceramic particles within viscoelastic pastes. In combination with cleaning agent design and auxiliary cleaning equipment, distinct dispersants were selected to enhance the flowability of the uncured paste during the ultrasonic cleaning and spraying processes. The morphology and reconstruction characteristics of specific structures illustrated the advantages and disadvantages of the two cleaning methods. The cleaning effect for small holes by ultrasonic cleaning was superior, but the structural damage of the green body was more serious. After spray cleaning, the surface roughness was lower with less damage to the green body, and there was less residual paste after cleaning. The results demonstrated that the selection of a cleaning strategy was beneficial to posttreatment of stereolithography-fabricated ceramic green bodies, achieving subsequent superior surface quality and accuracy of the internal feature size.

Missing position-error-signal sampling data in hard disk drives (HDDs) results in their servo systems having irregular sampling rates. Due to the natural periodicity of HDDs, which is related to the disk rotation, HDD servo systems with missing samples can be modeled as linear periodically time-varying (LPTV) systems. Based on previous H∞control synthesis results for general LPTV systems developed by some of the authors, an optimal H∞track-following control algorithm for HDD servo systems with missing samples is proposed. A simulation and implementation study, which has been carried out on a set of hard disk drives, demonstrates that the proposed control synthesis algorithm is able to handle missing samples and can be used to achieve the robust performance of a desired error rejection function for disturbance attenuation. Implementation results on multiple real hard disk drives validate the predicted robust performance.