Resins are used in casting for low-volume production, props, in the medical industry, and more. It requires molds, which are filled with liquid resin and hardens inside polymerizing. Some resins are easy to use and compatible with silicone or DIY molds, so even hobbyists can use them without special tooling to produce parts. The liquid nature of resin material also allows mixing it with additives for improving its properties and easier removal of molds.
Resins aren’t commonly used in CNC machining since they require a solid material to work with. Hardened resins like ABS, epoxy, Nylons and others can be machined as they are already plastics. However, on the market, there are some rare CNC machines that can combine paste extrusion of resins with milling operations. Resins, in this case, are typically used as coating for other materials and they can be placed and then machined with the same CNC machine in one go.