The rice milling machine mainly removes the bran layer by grinding and cutting the rice grains by intensive sand grains on the emery roll or sand mortar. The roller has a high linear speed of about 10~16 meters per second. The pressure in the whitening chamber is low, the grain surface is rough, but the broken rice is less.
There are two kinds of commonly used vertical sand mortar mills and horizontal sand roller mills. The roller of vertical sand mortar mill is a truncated cone sand mortar with large surface and small bottom. It has no gluten and groove on the surface, and can rotate or reverse. The clearance between sand mortar and its outer cone can be adjusted by the movement of the sand shaft. The adjustable rubber rice knife is installed equidistant from the whitening room to reduce the rice flow speed and increase the speed difference between the rice grain and the sand mortar. The degree of whitening can be increased by adjusting the rice knife.
The white rice flows out of the bottom of the whitening chamber and the rice bran passes through the sieve hole. The roller of the horizontal sand roller rice mill equipment is cylindrical and the inlet end has a propeller screw. The surface of sand roller is usually inclined, spiral or both. The section of the milling groove is serrated, V or semicircle. The rice sieve is cylindrical and has a rectangular or semi-circular section of steel rice knife.