Square plansifter

The invention provides a square plansifter. The square plansifter comprises a sifter body, two feeding frames, two sliding detection mechanisms, a plurality of composite pressing mechanisms and a controller. A driving box is arranged in the middle of the screen body, screen boxes are arranged on the two sides of the driving box, and stacked screen lattices are arranged in the screen boxes. The two feeding frames are located over the two rows of screening boxes correspondingly. The two sliding detection mechanisms are connected with the feeding frame and used for detecting the vertical distance between each sliding detection mechanism and the top wall of the screen body. The multiple composite pressing mechanisms are correspondingly arranged on the top walls of the screen boxes respectively and each provided with four abutting output ends, and the four abutting output ends are provided with pressure sensors and correspondingly abut against the corners of the top-layer screen lattices respectively. And the cont