Development of Metal-Cylinder Husker Rice Mill for Long-Grain Rice

This study was conducted to improve the metal-cylinder husker rice mill for long-grain rice which consisted of the cylinder husker, retention screen, polishing blades and adjustable polishing latch. The length of cylinder husker from the first 60 cm resembled a spiral shape with 23.20 degrees of helix for charging paddy grains into the milling part. The remaining length was a straight ridge for discharging the milled rice. From the field test, appropriate conditions included rectangular holes with 1x15 mm (w x l), a fully opened feeding chute, attached polishing blades, adjustable polishing latch level 3 and the cylinder husker rotational speed of 1,272 rpm. To improve the cylinder husker from metal to Nitrile rubber (85 Shore A), the influence of cylinder husker rotational speeds (1,200, 1,272, 1,400 and 1,527 rpm) was compared using metal-cylinder huskers. Milling conditions for the tests were comprised of retention screen with rectangular holes, fully opened feeding chute, attached polishing blades and adjustable polishing latch level 3. Results showed that the cylinder husker rotational speed of 1,272 rpm was suitable for both cylinder husker types, producing the highest head rice yield of 37.36% paddy weight from the rubber-cylinder husker while milling capacity was approximately 3.5 times lower. In the long run test at this speed, use of rubber-cylinder husker resulted in a head rice yield of 37.40%, broken rice of 28.31% and coarse bran of 34.28% while milling capacity was 30.45 kg/h, and milling efficiency was 65.72%.