The Rotobar gin works on the same principle as the roller gin. It has a rotating instead of oscillating beater bar, and is expected to give higher amount of lint per hour. The rotary knife vibrates less due to rotary motion and is more efficient than the reciprocating knife, which wasted time during backstroke. Ginning rate and carryover (unginned seed cotton that accompanies the seed) increase with feed rate. The main components of rotary knife roller gin stand include the stationary knife, rotary knife and ginning roller. The ginning roller is the most important and expensive component in the roller gin stand. Roller covering material is made from 13 layers of plain woven cotton fabrics cemented together with rubber compound.
Rotary-knife roller gin stands separate fibre from seed by frictional forces between a moving (roller) and fixed (stationary knife) surface.
Three frictional forces exist while roller ginning cotton:
(i) roller-to- stationary knife
(ii) roller-to-fibre and
(iii) stationary knife- to-fibre.
During normal ginning, the roller-to-fibre force is greater than the stationary knife- to-fibre force; therefore, the fibre sticks to the roller surface and slips to the stationary knife surface. Also, greater the force between the stationary knife and ginning roller, the greater the frictional pulling force between the fibre and ginning roller.
Cotton is ginned at the rate the cotton fibres (adhered to the roller surface) slip under the stationary knife. Overfeeding or feeding in bunches causes fibre and seed to entangle with each other and ginning performance gets adversely affected.
This Technology is mainly used for ginning of Pima cotton in the USA and other
black seed cottons in other countries of the world however this technology is having disadvantages in the fuzzy seed cottons where unginned cotton going with seed and seed cuts are observed due to inherent technological reasons. Therefore this could not find much place in the other countries where the cotton is hand picked and clean but Rotobar does not give better results on medium or short staple cotton.
Posted in: Textile Ginning