Parchment is first screened of foreign material, before passing over a rotating metal disk, which uses friction to separate the parchment from the green coffee. Parchment is then pulled out of the machine by a vacuum, while the green coffee is channeled out of the machine.
To be graded for size, green coffee passes over a series of layered screens, each containing different sized perforations. The largest screen is positioned on top, and allows beans to fall through as they vibrate forward, while the smaller beans pass onto their respective size screens. Each size bean is channeled into separate chutes, where each will continue processing for density and color.
Green coffee is graded for density to determine the integrity of the bean. It is loaded into a long metal surface, positioned at a five to ten degree slope, and fixed with small grooves that allow air to pass through. As coffee is vibrated forward, less dense beans gravitate down the slope, while the densest beans gravitate up the slope.
The final step in green coffee grading, is to screen out any off color beans. The color sorter uses high scan cameras to reject impurities as the coffee passes through the machine. After completing this process, the coffee is clean, and ready for export.