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Balance Bearings 101

Balance Bearings 101

Need a balancing machine with precision and less maintenance? We can help!

The Industrial Revolution birthed the use of rotating shafts in engines, turbines, pumps, and beyond to perform mass production replacing manual labor. Coincident with this, the first known patent for a balance machine was issued to a Canadian named H. Martinson as the need for compensation from vibration is recognized.

Over the following 100+ years, his idea was refined and expanded upon as a result of the explosion of growth in the understanding of rotordynamics theory, technology, along with the lessons learned in practical application. Regardless of application, a key component of balancing is the bearing on which the shaft is supported and turned.

Bearing designs in those days were limited, but today you have choices. Here, we’ll explore how the choice of bearings for your balancing machine can improve your results and ultimately the proper and efficient operation of a rotating shaft.

Balancing Basics

balancing bearingBalancing is essentially a calibration to compensate for the imperfect nature of a rotating component. Generally, it is either impossible or cost prohibitive to manufacture ‘true’ rotors. Instead, a calibration can be performed to compensate for the vibration errors induced by the imperfection of the machined rotors. An unbalanced rotating body will produce forces on its bearings and transmit them throughout its structure and into the foundations. If the component is not properly balanced, unintended forces are created on the operational bearings and supporting structures. This inhibits proper operation, potentially causing damage to the equipment itself or other supporting structures.

There are typically three standard balancing machines:

  • Static
  • Hard-bearing
  • Soft-bearing

Static balance machines balance in stands and do not require spinning up. They only correct for static or single-plane unbalance with sensitivity suitable enough for grinding wheels.

Despite the name, the difference between hard and soft-bearing balance machines is found in the suspension and not from the bearings used. Hard-bearings utilize rigid support structures and have low sensitivity, whereas soft-bearing machines have flexible supports and higher sensitivity.

Sensors are attached to the assembly to measure the unbalanced forces. Following electronic computations, weights are added or the product is modified (drilled/sharpened) in an attempt to improve the distribution of mass. The quality of balance required is critical to understand and can vary based on the intended application. Higher precision typically translates into more time and money in balancing operations.

Five Challenges of Traditional Balance Machines

As with any calibration equipment, the effects and limitations of the equipment itself also needs to be factored into the analysis. If not, the results can be skewed or out of balance forces become masked by calibration equipment errors. Traditional balancing machines employ roller bearings to rotate the shaft. However, the roller bearings themselves inherently present additional challenges to balancing operations.

1. Imperfections of Roller Bearings

Just as the balancing artifact is subject to manufacturing imperfections, so are the roller bearings used to rotate it. While trying to determine the error of the balancing artifact, roller bearings can end up introducing yet additional error to the balancing process.

2. Additional Vibration Unwanted Motion

The unique and imperfect nature of each roller bearing has a cumulative effect on error as they all work together to rotate a shaft. This creates asynchronous motion which can be challenging to characterize, creating additional work to isolate the error source. Given the imperfection in manufacturing, the roller bearings will also all ‘wear’ differently, which will contribute to the challenges of determining the asynchronous motion.

3. Wear

balancing bearingThe purpose of balancing is to remove or minimize out of balance forces that cause damage or minimize machine and component life. But to achieve this, these same forces are experienced by the roller bearings in balance operations until proper balance is achieved. Wear of the roller bearings is inevitable given the friction resulting as the bearings roll/spin the balance artifact during the calibration. Over time this will translate into a need for new bearings for the balance machine.

4. Maintenance

The inherent use of roller bearings drives downtime to perform the necessary oil/lubrication to continue balance operations. Despite the oil/lubrication, though, wear still occurs requiring downtime (and its associated cost) to replace the worn roller bearing. Additionally, when a new artifact is to be balanced, downtime is often required to remove and replace the existing roller bearings to adjust to the journal size of the new balance artifact.

5. Thermal Management

Roller bearings may be limited in speed due to friction-induced heat between the bearings and the rotating shaft. This heat degrades the oil viscosity and ultimately impacts the wear of the roller bearings and the reliability of their operations.

You may have been doing balance operations for a long time and come to expect these challenges as just par for the course. But what if there was a bearing solution that eliminated these balancing challenges?

A New Balancing Act

New Way® is pleased to offer an air bearing specifically for balance machines. These balance bearings (and all our products) are built on our foundational Porous Media TechnologyTM. This design utilizes porous carbon material inherent with millions of sub-micron holes, creating a thin yet robust air film across the entire bearing surface. Through the resulting surface-averaging effect, concerns of pressure gradients are resolved, resulting in the ability to provide greater precision on a consistent basis. New Way had its beginnings over 30 years ago with air bearings for the metrology industry, an industry with high-precision at its core.

New Way Balance Bearings utilize a combination of radial air bearings with a unique snap joint. Radial air bearings provide support for rotating, round artifacts at varying speeds using a thin (5µm) layer of air. This thin air layer is amazingly stiff, creating a stable support for a ring, or bearing surface, while allowing for surface speeds of up to 100 meters-per-second.

The snap joint promotes easy removal and replacement of bearing pads, allowing for different sized rotors to be balanced.

New Way also provides “bolt-on” adaptive hardware for implementing air bearings into existing low speed balance machines. An added bonus is that the adaptive hardware accommodates New Way’s gas bearing hardware, which is easily assembled to the adaptive hardware.

Five Ways Air Bearings Improve Balancing Operations

1. Decreased Vibration

Balance bearings utilize air to rotate the balance artifact, so there are no moving parts to impart vibration to the balancing operation. The roundness of the journal (often .0001 of an inch or better) is the only rotating reference surface and so the motion errors will be synchronous and averaged

2. Increased Precision

By removing less possible sources of error, greater precision can be achieved in balancing. The remaining error in the balance operation is synchronous allowing for a clean signal that is exactly the same each revolution, resulting with a finer resolution in balancing. Because there are no moving parts, the axis of rotation is improved creating improved resolution in balancing.

3. Increased Reliability

The absence of moving parts directly improves reliability. Because there is no friction, there is no ongoing wear affecting the reliability of operations, even with high-speed operations. Additionally, the even distribution of air through the Porous Media Technology provides consistent non-contact performance resulting in improved reliability and confidence in balancing operations.

4. Decreased Maintenance

The balance bearings inherent non-contact, frictionless design offers a number of maintenance benefits. There are no burdensome lubrication requirements, nor the concern of high-speed heat generation impacts. While roller bearings are often designed with a crown to avoid edge loading, they are still capable of damaging the rotors. Balance bearings are non-contact removing damage and wear concerns. This robust bearing design provides saving in both downtime and cost of performing maintenance in balancing operations. A decrease in maintenance for a balance machine offers the ability to send a completed balance artifact to its intended operation faster.

5. Improved Operational Flexibility

To further simplify balance machine operations, balance bearing pads are designed to “snap on/snap off.” This feature allows for several varying sizes of bearing pads to be easily switched out, allowing the balance machine operator to easily balance rotors with different journal sizes without having to adjust or plumb air into bearings. This flexible design minimizes cost as it is able to easily accommodate an entire ‘family’ of rotor sizes.

Ready for Harmonious Operations?

At New Way, we know it is sometimes difficult to find the right ‘balance’ between reliable, precise performance and the required maintenance. Whether your application is low-speed or high-speed, a properly balanced component can impact product life as well as safe and functional operation. It naturally follows then that your balancing machine needs to provide reliable operations with precise measurements in as minimal time as necessary.

New Way Balance Bearings provide a unique solution for the harmonious balancing operations you are looking for. If you are ready to improve the results of your balancing act with air bearings, contact us today for a complimentary consultation!

Learn More About the Porous Media Difference