The disc pulper was introduced in Ceylon shortly before the huge outbreak of leaf rust that permanently destroyed the nation’s arabica coffee production, in just one generation. The disc pulper was an important innovation because it was lightweight and could be easily transported to remote areas. Rather than abrading the coffee pulp with a horizontal rolling pin, in the style of a drum pulper, the cherry are pushed against a rotating disc that has a surface like a cheese grater. The disc spins at approximately 120 rpm. Machines come with multiple discs to increase their production capacity; a single disc is capable of pulping approx 1 tonne of cherry per hour.
Discs are usually made of cast iron. In the video below, you can see a triple-disc pulper in action in Burrundi. The pulp is separated from the parchment coffee by slipping between a small gap between the separating plate and the disc. From here it is sent to the fermentation phase. Small cherries may slip through with the pulp so to avoid this potential wastage, a repasser is used. A repasser is usually just a small drum pulper which is calibrated to have the pulping bar and the separator plate closer to the spinning drum.
In this video from green coffee importer, Nordic Approach, you can see a triple disk pulper in action at the Buziraguhindwa washing station in Burundi.