# High-Speed Alumina Stereolithography
## 1 Introduction  
In recent years, sustainability has become a significant concern in the manufacturing industry. Additive manufacturing describes a group of processes that fabricate 3D parts by the layer-wise joining of material from 3D model data [1]. In general, additive manufacturing (AM) technologies have many environmental benefits over conventional manufacturing, that have further driven innovation in the field. By using additive techniques, material waste can be reduced, new and smart materials can be used, and parts can be manufactured on demand [2]. Another key benefit of additive manufacturing is the incredible geometric freedom that enables cost-effective fabrication of complex parts, whilst avoiding expensive tooling [3]. Furthermore, computational analysis methods can be used to reduce the steps required for part optimization, from part design to process parameter optimization, reducing the cost and environmental impact of process development. Despite the benefits, there are still many factors that limit the widespread uptake of additive manufacturing in existing industry production lines. Some examples of barriers to AM include the limited catalog of AM optimized materials, material costs, and poor suitability for large production volumes. To appeal to industry, AM methods must provide fast and accurate part fabrication to compete with conventional manufacturing capabilities. This research presents the high speed fabrication of alumina parts by stereolithography, utilizing computational analysis methods to reduce the steps required for process optimization. Ceramic processing by AM is gaining popularity in research and industry for the fabrication of complex parts with high thermal resistance, corrosion resistance, and high hardness, for various applications such as biomedical implants, electronics, and structural parts [4, 5, 6, 7]. However, the fabrication of ceramic parts by additive manufacturing facesmany challenges. Generally, these materials are characterized by very high melting points and low ductility, making processing from the molten state prohibitively difficult. Heat treatments must be carefully controlled to prevent formation of cracks and pores due to poor thermal durability, and the hard and brittle sintered ceramic parts are difficult and expensive to machine [8]. Consequently, powder processing has been a popular route for research and development of ceramic AM, particularly by lithography-based fabrication. Stereolithography is a vat photopolymerization AM method that fabricates parts layer-by-layer through selective curing of a photosensitive resin. In ceramic stereolithography, fine ceramic particles are dispersed in a liquid photopolymer, e.g., acrylate or epoxy monomers, to form a photosensitive, thixotropic slurry. A UV laser scans single layer cross sections of 3D model data (Computer Aided Design, CAD) to selectively cure the slurry. As the slurry is cured, the solidified photopolymer joins the ceramic particles and forms the designed geometry into a \"green\" part. The green part is thermally post-processed to remove the polymer matrix and sinter the part to a dense ceramic component. In recent years, ceramic processing by stereolithography has been reported using a 355 nm UV laser with a 50 um spot size under conditions of 50-350 mW, and a maximum scan speed of 3000 mm/s for alumina [9], and 2000 mm/s for Yttria Stabilised Zirconia (YSZ) [10]. [PERSON] et al. reported stereolithographic processing of Zirconia-Toughened Alumina (ZTA) to form a complex dentoid part with a high density close to 100%, and the results of mechanical testing were comparable to ZTA parts shaped by conventional methods [11]. ZTA processing has also been described using a similar stereolithography technique as described in this work [12]. Ceramic stereolithography was carried out using a laser power of 400 mW and a scan speed of 4000 mm/s to create specimens for mechanical testing.