The transmission system is the key component of extruder. Our NE, SE series twin screw extruder used most advanced transmission structure at present of the world's, because the force structure of output shaft is the most reasonable form of bilateral gear symmetrically drive, that is to say, weak shaft (output shaft2) is limited by design space, and the gear is symmetrically driven by two gears of up and down, thus the radial force of bearing and gear  Fr1 and Fr2 will offset each other to zero, so that the bearing on this output shaft doesn’t bear any radial forces, and the gear is only drived by the torsion force of Ft1 and Ft2 which are pure torque output, thus the drive of two sets gear doubled output torque，so that the theory of wear for the bearing of output shaft2 is zero during use, then greatly improve the carrying capacity and durable life of the gear-box.