Systematic Compounding of Ceramic Pastes in Stereolithographic Additive Manufacturing.

Soshu Kirihara

doi:10.3390/ma14227090

Abstract

In this paper, stereolithographic additive manufacturing of ceramic dental crowns is discussed and reviewed. The accuracy of parts in ceramic processing were optimized through smart computer-aided design, manufacturing, and evaluation. Then, viscous acrylic resin, including alumina particles, were successfully compounded. The closed packing of alumina particles in acrylic pastes was virtually simulated using the distinct element method. Multimodal distributions of particle diameters were systematically optimized at an 80% volume fraction, and an ultraviolet laser beam was scanned sterically. Fine spots were continuously joined by photochemical polymerization. The optical intensity distributions from focal spots were spatially simulated using the ray tracing method. Consequently, the lithographic conditions of the curing depths and dimensional tolerances were experimentally measured and effectively improved, where solid objects were freely processed by layer stacking and interlayer bonding. The composite precursors were dewaxed and sintered along effective heat treatment patterns. The results show that linear shrinkages were reduced as the particle volume fractions were increased. Anisotropic deformations in the horizontal and vertical directions were recursively resolved along numerical feedback for graphical design. Accordingly, dense microstructures without microcracks or pores were obtained. The mechanical properties were measured as practical levels for dental applications.

Highlights

Stereolithographic additive manufacturing (STL-AM) has been performed to create industrial components of alloys and compounds [1,2,3,4]
The laser beams were adjusted to a spot diameter of 50 μm, and intensity distributions were visualized on vertical cross sections
The coagulated particles are remained in the scanning electron microscopy (SEM) view of Figure 6c

Summary

Introduction

Stereolithographic additive manufacturing (STL-AM) has been performed to create industrial components of alloys and compounds [1,2,3,4]. Periodically arranged patterns with dielectric constants for electromagnetic wave modulations, ordered porous electrodes of solid electrolytes for effective energy generation, graded lattice scaffold distributions of biological ceramics for artificial metabolism promotions, and diagonally connected supports in bulky alloys for component weight reductions were precisely fabricated [9]. Considering the rapid fabrication of biological implants, ceramic dental crowns can be successfully processed by using computer aided design and manufacturing (CAD/CAM) [11]. Crown precursors can be sintered into fine ceramic components with mechanical properties that satisfy the practical strengths required by dental bridges. Our research group has attempted to process alumina dental crowns by STL-AM using viscous resin pastes with dense particle dispersions [14]. Comparative investigations between virtual simulations of particle dispersions and real compounding of paste materials were discussed and reviewed along with the smart processing of alumina dental crowns with fine ceramic microstructures. Laser drawing parameters and layer lamination procedures were chosen as the experimental conditions in the STL-AM

Slurry Preparation and Stereolithography Setting

Process Optimization and Component Evaluation

Results and Discussion

Conclusions