A Theoretical Analysis of Cereal Seed Screening in a String Sieve

The conditions of the screening process in a fixed string sieve designed by the author have been formulated. The string sieve was designed for separating seeds of 5 cereal species (wheat, rye, barley, oats and triticale). The width of the separating groove was set at 1 mm at the beginning of the screen and 5 mm at the end of the screen. It has been assumed that seeds have a spheroidal shape and that their motion is initiated by positioning the string sieve at an appropriate angle. The results of a theoretical analysis revealed that at the given parameters of a string sieve, the above angle is determined only by the thickness and width of separated seeds. The sieve’s angle of inclination should be set at 45° to propel seeds into motion and at 50° to ensure the continuity of the screening process. Such a large setting angle is not recommended because it increases the sieve’s height and deteriorates the quality of the separation process. The problem can be solved by setting the separator bucket into motion and separating seeds at a small inclination angle of the string sieve.