Due to structural factors, material unevenness and manufacturing installation errors, all the actual rotors’ shaft are more or less deviated from its axis of rotation. The micro-mass quality of the centrifugal inertial force system is not a balance force system, that is, the rotor is not balanced. In particular, agricultural machinery, such as combine harvesters, threshers, straw crushers, fans are the rotors that more by the stamping parts and profiles welded or assembled from the geometric size too. The overall stiffness is small, rough manufacturing and inorganic processing processes. There is a large axis bending, shaft misalignment, uneven material, high-speed rotation. The rotor deflection and internal stress is very large, so that the machine produces a strong vibration and noise, aggravate bearing wear can cause welding, structural fatigue fracture malfunction. This is the current poor quality of agricultural machinery, short life, low reliability, and even cause an important reason for the production accident. Balance is a process in the manufacturing, commissioning and maintenance of rotating machinery. It is by changing the mass distribution of the rotor, that is, in the appropriate place on the rotor plus (or minus) some of the quality to reduce the rotor deflection, reduce the machine vibration and bearing support force. At present, the dynamic balance of agricultural machinery widely used rigid rotor low-speed compensation balance technology, which is a flexible agricultural machinery rotor, the working speed cannot achieve the expected balance accuracy requirements. The rotor is divided into rigid rotor and flexible rotor. In the balancing technique, when the working speed is much lower than the first critical speed of the rotor, the unbalanced centrifugal force causes the deformation of the rotor to be small and negligible, which is called a rigid rotor. The rotor speed closer or higher than the first critical speed, is also known as the flexible rotor.

At the working speed, the balancing counterweight is carried out within the entire speed range. The weight should not only the minimizing the reaction force at the bearing be made, but also the rotor is subjected to the minimum bending torque, that is, the rotor has the least deflection. Considering the agricultural machine rotor eccentricity is relatively large, in the low and medium speed coarse can balance large eccentricity. The working speed of precision balance to achieve can improve balance accuracy, the rotor deflection and bearing dynamic reaction to a minimum, and then retest. Low speed can be set to work speed of 5O%, 80% of the speed is the medium, high speed is the rotor working speed.

Recently, the dynamic balancing machine is complicated, and the quality of the operation is relatively high. Especially for the dynamic balance of the flexible rotor, the speed regulation, the adjustment of the amplifier, the selection of the counterweight plane and the optimization of the counterweight are more complicated. Technical force is relatively weak, so the application of dynamic balancing machine is limited. Automatic dynamic balancing machine to give full play to the advantages of computer computing and automatic control, the complex technical operation by the computer automatically. Its main features are as follows:
1. dynamic balance of high precision. As the signal program-controlled amplification, A/D conversion can be optimal. Dynamic balance achievable residual unbalance can be minimum 1 g · mm · kg.
2. Balanced rotor deflection is minimal. The distribution of unbalanced amounts in the axial direction is determined and optimized by the computer, giving the optimal counterweight for each counterweight plane, reducing the flexibility of the flexible rotor.
3. The dynamic balance recognition process is fully automated. Including the automatic adjustment of speed, program-controlled amplification, overload protection, automatic shutdown and other functions, just press the start button, the rest by the computer control automatically.
4. Display interface intuitive. There are pattern displaying dynamic balance process and dynamic balance results, as well as online help function.

A New Thinking to Dynamically Balance Flexible Rotor