The paper presents the analysis of oat grain mass separation in the innovative rotary cleaning device of rotary conical sieve-based construction. The cleaning process combines the sieving operation on the conical sieves and pneumatic separation. The cleaning device facilitates the separation of the treated mixture into four fractions. The analysis of oat grain mass separation has confirmed its usability as stationary grain cleaner. The presented cleaning device is a genuine example of the CAD system applicability for creating novel equipmen