What is the key chemical difference between standard SLA resin and castable SLA resin?

The key chemical difference between standard SLA (Stereolithography) resin and castable SLA resin lies in the inclusion of specific components in the castable resin formulation that facilitate clean burnout during the investment casting process. Standard SLA resins are typically designed for high detail and strength but leave behind a significant amount of ash and residue when burned, making them unsuitable for investment casting. Castable resins, on the other hand, contain a higher percentage of wax-like or volatile components and a lower percentage of inorganic fillers. This composition allows the resin to melt away cleanly at relatively low temperatures, leaving minimal ash and residue in the mold. The reduced ash content is crucial because any remaining ash can contaminate the molten metal during casting, leading to defects and weakening the final product. Therefore, castable resins are specifically formulated to decompose cleanly, ensuring successful investment casting, whereas standard resins prioritize other properties like strength and detail without considering burnout characteristics.