The separation and pre-grading units of the SG-series are so-called "incomplete machines", which designed for installation in other machines and equipment. Depending on the application the so-called "SG units" can be integrated as pre-assembled module into an already existing processing line, to be used for soil cleaning and/or pre-grading. The soft, wear-resistant polyurethane (PU) spiral rollers achieve lowest impact on the crop and an effective separating performance. The maintenance-free direct drives of the PU spiral rollers, with their infinitely variable speed adjustment, enable a perfect adaptation to all operating conditions and requirements. This drive concept provides the basis for the centrifugal cleaning system, called Turbo Clean, whereby adhering soil is loosened from the PU spiral rollers at maximum speed.