Balancing has been an important function in industries that produce or utilize rotating machinery and equipment. The reason for balancing rotating equipment is because most materials and manufacturing processes are inherently flawed to some degree. It is extremely difficult to achieve a perfectly balanced product using conventional manufacturing techniques and companies spend considerable efforts to measure and correct imbalances in their products and equipment.
When a rotating component contains an imbalance, it implies that the rotational axis does not coincide with the center of mass of the object; depending on the operational speed, mass and frequency response of the component, vibration is likely to occur. The force that causes vibration due to mass imbalance is directly proportional to the square of the rotational speed, and therefore balancing becomes critical with machinery operating at higher rotational speeds.
There are three major forms of imbalance that are observed in rotating components:
- Static imbalance – occurs when the axis for the center of mass is parallel and offset from the center of rotation
- Coupled Imbalance – occurs when the axis of the center of mass intersects with but is not parallel to the axis of rotation
- Dynamic Imbalance – occurs when the axis of the center of mass does not intersect with and is not parallel to the axis of rotation
Modern balancing machines can measure the various forms of imbalance mentioned above. Rotating components that have a relatively large diameter compared to their width only require single plane balancing, whereas components that have a small diameter relative to the width have to be balanced in two planes.