What Is the Best Method for Correcting Unbalance?

The best compensation method for correcting unbalance in a rotor depends on the amount of unbalance, the part's geometry, and its operational requirements. There are two main methods: adding weight and removing weight. When dealing with a minor unbalance, removing a small amount of material from the part can be a more practical solution. Methods like drilling, milling, or grinding are typically used for this. These techniques are generally ideal for small and delicate parts because they allow for precise, millimeter-level adjustments to eliminate unwanted vibration. However, it is crucial not to damage the part's physical integrity during these operations or cause structural weakness. Excessive material removal can compromise the part's strength.

On the other hand, if there is a significant rotor unbalance or if removing material is not feasible, adding weight is the safest and most effective method. In this approach, a weight, calculated by the machine, is added directly opposite the point of unbalance. This weight is usually secured to the part by welding or mechanical fasteners (screws, rivets, etc.). The weight addition method directly corrects the unbalance by shifting the part's center of gravity and avoids unnecessarily weakening the part. At MBS Balance, with our machinery and expertise supporting both methods, we guide you in determining the most appropriate and safe compensation method for your part. Choosing the right method ensures not only the success of the balancing process but also the reliability and longevity of the part.

What is decisive in method selection is the precision and repeatability of the correction and the structural integrity of the part. In the material-removal method, the mass to be removed is calculated from the hole diameter, depth, and material density. Making the correction at the largest possible radius allows less material to be removed for the same unbalance (since U = m × r). Because sharp-cornered, deep holes can create stress concentration, they must be positioned carefully on parts operating under fatigue load.

In the weight-addition method, the safety of the attachment is critical: because welding carries a risk of cracking in materials such as cast iron, bolted or riveted weights may be preferred; on high-speed rotors, it is essential that the weight be secured so it cannot be dislodged by centrifugal force. In series production, automatic drilling/milling units make the correction repeatable. MBS Balance determines the safest compensation method according to the part's material, speed, and tolerance profile and, when necessary, offers automatic correction stations.