What is the difference between hard bearing and soft bearing balancing machines?

Hard bearing and soft bearing balancing machines are two types of equipment used for dynamic balancing of rotating machinery, such as turbines, fans, and motors. The main difference between these two types lies in the way they measure and correct the unbalance in the rotating components.

1. Hard Bearing Balancing Machines:
   Hard bearing balancing machines, also known as rigid bearing or rigid rotor balancing machines, are designed to handle relatively small and lightweight rotors. The key features of hard bearing machines include:

• Construction: Hard bearing machines have rigid supports, often made of steel or cast iron, on which the rotor is mounted. The supports are relatively stiff and provide a stable base for measurement and correction.
• Measurement: The unbalance of the rotor is measured by sensors (such as accelerometers or proximity probes) located on the supports. These sensors detect vibrations caused by the unbalance and provide feedback to the balancing machine.
• Correction: Typically, hard bearing machines use manual correction methods. The operator adds or removes weight from specific locations on the rotor using trial weights until the unbalance is reduced to an acceptable level.

2. Soft Bearing Balancing Machines:
   Soft bearing balancing machines, also known as flexible bearing or flexible rotor balancing machines, are designed to handle larger and heavier rotors. The main characteristics of soft bearing machines are:

• Construction: Soft bearing machines have flexible supports, often made of air or oil film bearings, on which the rotor is mounted. These flexible supports allow the rotor to move freely, minimizing any constraints imposed by the balancing machine.
• Measurement: Soft bearing machines employ high-precision sensors (such as laser displacement sensors) to measure the displacement of the rotor caused by unbalance. These sensors provide accurate data on the amplitude and phase of the unbalance.
• Correction: Soft bearing machines use automatic correction methods. Typically, they have built-in mechanisms to add or remove weight from the rotor dynamically. This can be achieved through drilling, milling, welding, or other automated processes, based on the gathered measurement data.

In summary, hard bearing balancing machines are suitable for smaller and lighter rotors and employ manual correction methods. On the other hand, soft bearing balancing machines are designed for larger and heavier rotors, offer more precise measurement capabilities, and utilize automated correction mechanisms. The choice between the two types depends on the specific requirements of the balancing task and the characteristics of the rotating machinery being balanced.