Erfan Vahedi - Department of Mechanical Engineering of Bio-systems, Agriculture and Natural Resources Campus, Razi University, Kermanshah, Iran
Hekmat Rabbani - Department of Mechanical Engineering of Bio-systems, Agriculture and Natural Resources Campus, Razi University, Kermanshah, Iran
Payam Faramarzi - Department of Mechanical Engineering of Bio-systems, Karaj Agriculture and Natural Resources Campus, Tehran University, Karaj, Iran

Considering the increasing population of the world and the lack of human food sources, it is very important to pay more attention to fodder plants that can indirectly supply human food. By using choppers, a large amount of fodder can be transported and prepared for anaerobic fermentation of fodder.  In this research, a control mechanism has been proposed to change the angle of the knives on the cutting drum with a tangent plane on the circumference of the drum in order to change the distance between the knives and the fixed knife and change the length of the pieces. The mechanism was analyzed in SAM software, and then the three-dimensional model of different blade angle states was designed and analyzed in CATIA V۵ R۲۱ software. According to the obtained data, although the Von Mises stresses occur at the minimum angle of ۲۲ degrees and the maximum Von Mises stress occurs at an angle of ۱۶.۵ degrees, there is no significant difference in the amount of stresses. Therefore, this mechanism can be recommended for all the mentioned situations (angles). For ۱۶۰۰rpm rotational speed and ۶۰۸۳ N/m line force density the occurred Von Mises stress in ۲۲ degree angle is lower than zero degree angle.

Chopper, Cutting energy, Cutting length change, Chopping cylinder, Mechanism