There are numerous types, but they basically use the same style of cleaning.

Scalpers are used to remove large trash, stems, leaves, and associated chaff prior to basic cleaning.

Raw material is metered onto a flat screen that is set at a slight incline and vibrated mechanically. Trash is removed as the seed fall through the holes in the screen and onto a second screen.

This screen traps the seeds and moves them to a hopper as smaller trash falls through the holes and is sweep away by an air current.

Another style uses a round drum made from a perforated metal screen set at a slight incline.

As the drum rotates, seed fall through the screen and trash remaining in the drum is removed.