Method of dynamic balance of machine tool spindle

 

The application and development of high-speed machine tools require the increase of spindle speed. However, in the manufacturing process of machine tool spindle group parts, it is inevitable that the center of gravity will deviate from the center of rotation due to uneven material, asymmetric shape and machining and assembly errors, which will cause vibration and vibration force of the machine tool, noise of the machine tool and heating of the bearing. With the increase of rotating speed, the vibration caused by imbalance becomes more and more intense.

Because the deformation of the spindle assembly of machine tool is very small when it rotates, in order to simplify the calculation, it is regarded as a balancing method of rigid rotor. The rotor is regarded as an absolute rigid body, and it is assumed that the rotating shaft will not be significantly deformed under the action of unbalanced centrifugal force when working. Therefore, under these conditions, many complex unbalanced states of rigid rotors can be simplified as force system imbalance, that is, two dynamic balancing forces equivalent to Ud1 and Ud2 can be added or subtracted on two arbitrarily selected planes to balance them.

The dynamic balance of rigid rotor is generally low-speed dynamic balance, which is generally less than 1/3 of the first critical speed.

Unbalance: The distribution of rotor mass caused by vibration or motion on bearings due to centrifugal force.

Residual imbalance u: the imbalance left after the balance treatment.

Relative unbalance e: the value obtained by dividing the unbalance by the rotor mass, which is equal to the displacement of centrifugal force to the shaft center.

Balance degree g: it is the product of relative imbalance and specified angular velocity.

Balance treatment: the operation of adjusting the mass distribution of the rotor in order to make the vibration and force acting on the bearing synchronous with the rotation speed within the specified limit.

Full key: refers to the key or equivalent key used in the final assembly of the rotating shaft and mating parts with keyways.

Semi-key: it is a key used when the rotating shaft or matching parts with keyways are dynamically balanced separately.

This imbalance is equivalent to the key used in final assembly (imbalance buried in the keyway of rotating shaft or mating parts).

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