Although rice-polishing machines differ by model, their main structures are generally similar. A typical machine includes a spray-water section, a polishing section, a water-supply system and an air-supply mechanism. The feed and discharge devices are also important parts of the complete machine.
Spray-water section
The spray-water section consists of the nozzle, nozzle cleaner, water mixer, feed screw and mixing roller. When material passes through the flow meter, its flow rate is measured and used to control the amount of water added.
Polishing section
The polishing section is the core of the machine. It is composed of the feed screw, polishing roller, octagonal screen cylinder made from eight rice screens, and the discharge-pressure gate. Polishing rollers can be divided into iron rollers and emery rollers. During design, the linear speed of an emery roller should be higher than that of an iron roller. A typical iron roller operates at about 5 m/s with an average polishing pressure around 0.1 MPa, while an emery roller can operate at about 15 m/s with an average pressure around 0.02 MPa.