What Is Balancing Machinery?
Balancing machinery is a measuring instrument that measures the rotational vibration of rotating parts.
When rotating parts are machined and assembled, the center of rotation and center of gravity do not necessarily coincide due to errors in machining or misalignment during assembly. Therefore, when used as is, rotational vibration is generated during use. Rotational vibration not only causes discomfort during use but can also lead to machine breakdowns and damage.
Balancing machinery measures the vibration and indicates the amount of disproportion (correction amount) so that the rotational vibration can be kept within the standard value.
Uses of Balancing Machinery
Balancing machinery is used in the manufacture of many rotating products.
A familiar product is an automobile tire. Tires consist of a rubber portion on the outer circumference and a wheel in the center. The center of gravity of each part is misaligned during manufacturing, and the misalignment remains even after they are combined. If the tires are mounted on the vehicle as they are, vibration is generated in the steering wheel and the entire body when driving at high speeds. As a countermeasure, the misalignment is measured by balancing machinery before installation and corrected using weights.
In addition to tires, important parts such as axles, engine crankshafts, and flywheels are always measured for disproportionality.
Principle of Balancing Machinery
In addition to the vibration caused by the misalignment of the center of gravity of the entire rotating body (first-order vibration), vibration (second-order vibration/even force vibration) is caused by the different centers of gravity at both ends of the shaft. Since the even force vibration cannot be measured when the rotating body is stationary, it must be measured by rotating the body.
Measurement of unbalance is performed by attaching both ends of a test object, such as a shaft, to the rotating shaft of balancing machinery. The rotating shaft is equipped with an angle sensor and a displacement sensor to measure how much and at what angle displacement occurs during rotation. By using different displacement sensors at each end, it is possible to measure the displacement of the center of gravity at both ends, which is the cause of the generation of the even force vibration. This is called a two-plane unbalanced measurement.
There are two types of methods for measuring displacement during rotation: hard type and soft type. The hard type has a rotating shaft with high rigidity support, which enables stable measurement even at high rotational speeds. On the other hand, the soft type supports the rotating shaft with a leaf spring, which is less rigid but can detect slight vibrations and enable high-precision measurement.
Due to the characteristics of the vibration that occurs during rotation, care must be taken when selecting a balancing machine to ensure that the resonance point of the balancing machinery does not coincide with the rotational speed to be measured.