Category Archive: Balancing

Benefits of Unbalance Budget Analysis for Rotors

Benefits of Unbalance Budget Analysis for Rotors

While rotor balancing can sometimes be treated as an afterthought within the aerospace industry, rotor unbalance has a significant impact on overall machine performance, durability, and quality. When designing any rotating part, engineers must pay careful attention to the unbalance correction strategy. To optimize rotor design for improved performance, Andreas Buschbeck et al. from SCHENCK developed the Unbalance Budget Analysis method.

The unbalance budget summarizes all reasons for the unbalance based on the given tolerance limits in the part drawings. Here, we’ll go over the key characteristics of rotor unbalance, as well as Buschbeck’s thoughts on why performing unbalance budget analysis is so crucial and how it’s accomplished.

Characteristics of Rotor Unbalance

Rotor unbalance can fall into three primary categories:

  • Intrinsic unbalance: A type of unbalance that results from variations in manufacturing tolerances or other factors relating to manufacturing technique.
  • Unbalance due to runout: An unbalance that comes from geometric variations in the shaft surfaces, particularly the mounting surfaces.
  • Unbalance due to fit clearance: This type of unbalance is due to fit clearance and is related to geometric variations in the assembly. For example, assembly misalignment can occur due to variations in the mating interface.

Within all of these categories, there are many physical considerations that can result in unbalance. Controlling the level of unbalance in a rotating part requires a thorough definition of its reference features to which all shape and form tolerances can be compared.

For instance, misalignment is a common cause of rotor unbalance. To define the acceptable level of misalignment a rotor can have, engineers must control the combined effect of geometric tolerances, including:

  • Concentricity
  • Coaxiality
  • Roundness
  • Lateral and radial runouts

Reasons to Perform Unbalance Budget Analysis

Rotor design requires an estimation of future unbalance correction which has to be applied for upcoming unbalances caused by geometric features and tolerance limits. This estimation helps to determine additional rotor features that allow the unbalance correction.

Difficulties often arise when using design software that fails to account for unbalance or does not have the ability to achieve a balanced state for each rotor design. To overcome this challenge, a quantitative analysis method can be used to review the sensitivity of the abovementioned factors and correlate them to the rotor unbalance level. Based on the results of this analysis, it’s possible to understand which rotor features have the biggest impact on unbalance and correct them.

A well-engineered rotor balancing strategy lowers costs and improves the manufacturing process by streamlining workflow. Additionally, it helps to determine which parts must be precision-machined to avoid unbalance and which can adhere to more rough geometric tolerance limits.

Performing Unbalance Budget Analysis

Several factors go into performing an unbalance budget analysis. First, an estimation and calculation of both initial and assembly unbalance must be performed for all relevant single components. This involves:

  • Estimating based on past experience with similar rotors
  • Determining the empirical value of manufacturing
  • Analyzing the drawing tolerances

Many factors influence unbalance in single parts and assemblies, and these must also be considered. Engineers will review:

  • Manufacturing tolerances
  • Mass tolerances
  • Fitting tolerances and eccentricity respectively failure of concentricity
  • Coaxiality
  • Curvature and misalignment respectively axial run-out
  • Product of inertia of the single components around their center of gravity
  • Assembly of sub-components

The final step is to consider any other potential cause of unbalance and then make a statistical summation of all of these factors and their significance. The summation should discuss both static unbalance and moment unbalance, as well as effects in the unbalance planes.

Unbalance Budget Analysis: Required Data

Unbalance Budget Analysis: Optimizing Rotor Design for Manufacturing Performance

In the final analysis, there are many types of information that should be presented. This includes the measurement results (if available), all relevant part masses and densities, a description of the preliminary unbalance correction, and the distance between the bearings. In addition, 2D detail drawings with all geometric tolerances of all relevant rotating parts should be included. Finally, the analysis should feature 3D models of all relevant rotating parts as an assembly in either STEP or Parasolid (*.x_t) format.

For a more in-depth look at performing an unbalance budget analysis, download our eBook, “Unbalance Budget Analysis: Optimizing Rotor Design for Manufacturing Performance.”

Contact Test Devices for Balancing Services

Performing a rotor unbalance budget analysis not only results in better-performing parts but can also reduce manufacturing costs. Gain a more in-depth understanding of this process by reaching out to our team with any questions. To get started improving the quality of your rotating parts, request a quote today.

What Is Rotor Balancing and Why Is It Essential?

Rotors in rotor balance machineRotors are a critical component used to convert electric or electromagnetic energy into rotational motion. For rotors to operate reliably, they must maintain even weight distribution across the rotational axis. Too much weight on one side creates uneven mass distribution known as “unbalance”.

Rotating parts in any mechanical assembly can become unbalanced. Uneven weight distribution of a rotating component causes the part’s rotational center to be out of alignment with the geometric axis. When unbalance occurs, the operational efficiency and safety of the system in which the rotor operates are compromised. Rotor balancing can help to prevent issues caused by unbalance, reducing noise and vibration and extending the life of your system.

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What Are the Various Rotor Groups?

Rotors are grouped into two categories: rigid and flexible. Rigid rotors can be balanced at lower speeds, as long as there is sufficient centrifugal force to detect the unbalance. Flexible rotors, on the other hand, deflect outward from the rotational axis, and the center of rotation moves away from the rotational axis as the speed increases. Unlike rigid rotors, flexible rotors must be balanced in stages, starting with lower speeds and slowly working up to operating speed.

Why Is Rotor Balancing Essential?

High levels of vibration caused by unbalance can cause equipment to operate less reliably, which results in increased energy usage, decreased operational efficiency, and reduced equipment service life. The force exerted by the dynamic load from an unbalanced rotor will cause wear to the rotor itself, the bearings and mountings holding it in place, and the machine’s structural support. Although the severity of the dynamic load varies depending on the degree of unbalance and the rotation speed, any unbalance can cause problems.

Silver rotor balancing machine in operation

Vibration from an unbalanced rotor creates excessive noise and resonance, which will ultimately compromise the structural integrity of the equipment that supports the rotor assembly. The damage caused by unbalance is especially apparent in bearings, suspension equipment, support housing, and the equipment foundation. These components are typically exposed to the highest level of stress caused by the excess dynamic load due to unbalance. With ongoing exposure, these components will be more likely to suffer premature wear.

In addition, the high vibration caused by unbalance can loosen fasteners such as screws, nuts, and bolts, rendering the structure less stable. Pipes, electrical cables, wiring, electrical connections, and switches can also be negatively affected. With extended exposure to high levels of vibration, even nearby equipment and structures can be compromised, creating the potential for greater damage and injury.

What Are the Various Types of Unbalance?

When balancing your rotor, it is critical to understand the different types of unbalance. There are three types of unbalance, including:

  1. Static Unbalance: This type of unbalance occurs when the mass axis is displaced parallel to the shaft axis. Static unbalance is corrected only in one axial plane.
  2. Couple Unbalance: Couple unbalance occurs when the mass axis intersects with the running axis. This type of unbalance is typically corrected in two axial planes.
  3. Dynamic Unbalance: Dynamic unbalance is typically a combination of static and couple unbalance and occurs when the mass axis does not intersect with the rotational axis. This can usually be repaired by correcting the balance along two axial planes.

Contact Test Devices by SCHENCK

Rotor balancing being performed by machine on white backgroundAt Test Devices by SCHENCK, we are dedicated to providing our customers with expert balancing solutions for rotating and oscillating equipment in a wide range of applications and industries. With more than 50 years of experience, we have the knowledge, equipment, and skill necessary to provide superior balancing services for everything from modular drills to industrial crankshafts and wind power turbines. We are skilled in servicing equipment of all sizes, from miniature dental motors of only a few ounces to 400-ton steam turbine rotors.

Our expertise extends to dynamic balancing, static balancing, couple balancing, and much more. With an international team of over 900 experts, we work tirelessly to design, research, develop, and produce actionable balancing solutions for customers in the automotive, aerospace, electrical, and mechanical engineering industries. In addition, we offer maintenance services and quality control testing to ensure that your rotor equipment is operating within applicable industry standards and regulatory guidelines.

We are committed to providing superior rotor balancing services to our customers around the world. To learn more, contact us today.

Figure 1,  A Rigid Test Rotor mounted on a Schenck Hard Bearing Balancing Machine.



How To Avoid Major Causes of Unbalanced Parts

Person working on rotor balance machineryUnbalanced components can lead to electrical motor failures that necessitate costly investigation, repairs, or replacement. The easiest way to avoid this is to properly balance the rotor during the manufacturing stage.

Unbalance happens when a rotating component’s center of mass, or inertia axis, becomes unaligned with its center of rotation, or geometric axis. It causes the rotating component to exert dynamic load on its supports, shaft, and connected structures. Here, we will discuss some common causes of unbalance and how to correct them as well as why it’s important to have balanced parts.

What Causes the Unbalance of Parts to Occur?

In general, all cases of unbalance result from the uneven distribution of mass around a rotation axis. However, this unevenness can be caused by various factors, including the buildup of contaminants, assembly errors, dimensional and mass deviation in the parts, deformation of the parts, and normal wear of moving parts. Other factors that might contribute to unbalance include some unintended change caused by maintenance repairs, replacing a part, or incorrect placement of a part.

Since unbalance is a leading cause of premature failure in a rotating machine, it’s important to take the necessary steps to correct or prevent it.

How Do We Correct Unbalanced Parts?

To avoid further damage, balance correction must be carefully planned and performed. Two ways to correct unbalanced parts include material removal and material addition. Which method we use depends on the cause of the unbalance and the design of the parts.

Material Removal

The material removal method relies on abrasion, milling, or drilling processes. With the abrasion process, air-powered sanding or manual grinding tools are used to remove material; however, milling and drilling offer enhanced control. Material removal tooling must be able to remove the right amount of material from the correct place and to the proper depth without damaging nearby parts. At Test Devices, we use specially designed and calibrated milling equipment to remove material while maintaining high levels of precision and a superior finish.

Material Addition

Material addition methods solve unbalance by adding various correction features on the rotor, such as blades, inserts, washers, or screws. In some cases, we may weld material to the rotor or add epoxy coatings.

Why Is It So Crucial to Have Balanced Parts?

Small individual rotor balancing machineUnresolved balance issues can lead to serious consequences for you and your client, ranging from quality issues, significant schedule setbacks. Unbalance can lead to higher vibration and noise levels in machines, affecting their overall efficiency and quality.

When left undetected, unbalanced rotors can lead to high maintenance and repair costs. In an extreme scenario, an unbalanced part from your facility could end up in a live field environment, where part failure can have disastrous consequences.

Balancing Services from Test Devices

Avoiding and correcting unbalance is crucial in preventing premature part failure in electrical motors. At Test Devices, we have provided high-quality balancing services for over 40 years. We are AS9100/ISO9001 certified, and our balancing services support a wide range of industry standards. To learn more about our balancing capabilities, contact us today.

Industrial Applications of Spin-Testing and Balancing

Precision testing of high-speed, high-performance motors and rotors is of paramount importance in today’s aerospace, automotive, and defense industries. 

Spin testing is performed to validate the design, durability, balance, and structural integrity of the motor. The material and structural behavior of the rotor, which ties to the efficiency of a machine, is of major import across the many varied applications of electric motor technology, ranging from UAVs and UAMs to hybrid and electric vehicles. Industries that depend on high-speed rotating machinery rely heavily on test results to accurately predict how their technology will perform in real-world situations. 

Applications of Spin-Testing

spin-testing Proof and overspeed testing are standard for manufacturers of rotating equipment and turbomachinery. Simply put, overspeed testing validates the rotor integrity against the speed of the rotor to a rate far greater than what the component will encounter  in its operation. For example, FAA certification of aircraft turbines disk mandates overspeed testing before the engines can be used in aircraft. 

There are myriad tests that may be relevant based on the specific type of rotor application. For example, rotors fabricated from a new materials or constitute a radically new designs are subjected to more rigorous testing to certify for relevant regulatory standards and operational safety requirements, as well as gather as much data as possible about the effectiveness of the new technology. In this case, Test Devices could help conducting advanced spin testing to design and implement the test, and measure the critical data to evaluate the performance of the part. 

At Test Devices, we possess a broad variety of spin testing capabilities suitable for various testing scenario, including:

  • Proof spin and overspeed testing for compliance
  • Rotor strength and material evaluation via burst test (with high-speed imaging)
  • Rotor durability and fatigue evaluation via LCF testing
  • Heated and thermal gradient test to capture the accurate material conditions
  • Rotor growth and profile mapping – Capture the material behavior under CF load


Proper balancing is an essential step to ensure the reliable operation of any type of rotor. Even a small unbalance can result in problems ranging from unexpected rotor wear to catastrophic equipment failure. 

balancing-services-test-devicesUnbalance is inherent in any real-life rotors. Even the minute variation within the manufacturing tolerances, and uneven distribution of material properties about the axis of rotation could cause the bias in the distribution of the CF load in a rotor that results in undesirable vibration. 

In some cases, involving high-speed rotors, more complex scenario must be considered. Unexpected deformation of rotor due to the emergence of plasticity or shift in the internal structure of a rotor (e.g. winding settling in the motor armature) could result in an unintended unbalance. In such a scenario, the combination of both spin testing and balancing plays a critical role in identifying and resolving potential problems in the rotor.

As such, proper balancing is a critical step to the successful function of rotating components. An unbalanced condition can be very hazardous and may result in severe damage to machinery, threaten the safety of equipment operators, and drive up costs due to redesigns.

Spin testing and balancing plays a critical role in ensuring the safe and reliable operation of the final component, ensuring its integrity and reliability – optimizing the performance and extending the machine’s useful life. 

Advanced Spin Testing Services from Test Devices

Test Devices has more than 40 years of experience in advanced spin testing practices. Our state-of-the-art equipment and highly trained staff of engineers and technicians offer innovative solutions to the challenges facing designers and manufacturers of rotating components.

We can help you optimize your designs and accelerate your development and production process by providing you with all the relevant test data that you need.

Contact Us today for more information about our spin testing services or to discuss your design with one of our experts.

Expanding Capacity – Balancing Services

Rotating components such as jet engine disks and high-speed motor armatures must be balanced well to warrant a good performance and overall longevity of machines. Balancing machines pinpoint the exact amount and the location of unbalance in rotating components. Once these areas are identified, skilled technicians correct the unbalance level by either removing material in heavy areas through drilling, milling, or other processes or by adding mass (weld or bolt additional material onto areas that are too light).

Unbalance resulting from eccentricities between the center of the rotor’s gravity and the axis of rotation causes the heavier side of the rotor to exert more centrifugal load. The unbalance in the rotor often directly impact the levels of noise, vibration, wear, and leads to significant reduction in service life of the equipment. In some applications, unbalanced rotors are even considered to be a safety hazard if machine failure can result in personal injury or property damage.

New Updates for TDI’s Balancing Machines

For the past four decades, Test Devices Inc. (TDI) has provided customers with an extensive range of rotor engineering services, including diagnosing and resolving various balancing issues. In an effort to meet growing consumer demand and reinforce our commitment to providing the most accurate rotor balancing services, we’ve expanded our balancing capabilities by acquiring a new HM 20 Schenck Horizontal Balancing Machine.

This state-of-the-art machine represents the latest in rotor balancing technology. One of the main benefits of the HM 20 is its hard-mounted bearing design, which ensures rapid changeovers between rotors. This feature allows us to handle significantly higher volumes of balancing jobs without compromising the quality and repeatability of the work, and increasing the efficiency of our operational capabilities.

Additionally, the HM 20’s modular design makes it easy to modify the setup for a wide range of components by using various purpose made attachments. These features increase the versatility of the balancing machine and allow us to meet the unique demands of customers regardless of industry or application.

Differentiating our services, our balancing operation offers:

  • Accuracy & Precision: We address a wide selection of balance testing needs, including unbalance tolerances below ISO G2.5 specifications. We’ve developed distinct processes to ensure accuracy and repeatability of our balancing work, including studies and analytical method for asymmetric rotors.
  • The Facility: Our balancing machines are carefully set up, calibrated and maintained by experts so that they are properly calibrated and dynamically isolated. We have also set up a dedicated area to efficiently perform the various tasks involved in balancing work. We offer comprehensive options for balance correction methods ranging from simple dremel to precision CNC machining.
  • Quality: We offer full inspection services ranging from CMM dimensional checks, visual checks and manual measurement by experts. We follow AS9100 Aerospace Standards. All of our work is recorded and fully traceable. We also comply to various requirements to serve ITAR works.
  • Handling: We understand the importance of proper handling and protection of the critical features of customers’ parts. Our engineers will work with you to fully capture your handling requirements in the balancing operation. Our team can support your needs in design and provision of protective gears.
  • Engineering Support: In addition to balance correction services, Test Devices (and our parent company, Schenck) offers advanced technical support in designing customized balance toolings, fixtures, as well as offering engineering consultation on planning balancing processes and designing balancing features for your rotors. Dealing with balancing as an “afterthought” often results in an expensive problem.

Balancing Services at TDI

At Test Devices Inc., we offer a broad range of timely and cost-effective balancing services for virtually any size of rotor. Our advanced equipment (including the newly acquired HM 20 Schenck Horizontal Balancing Machine) will balance the most intricate and complex parts in the aerospace industry.

Our services also include the design and manufacture of customized balance tooling to help produce unique and precisely balanced components.

Our staff consists of highly qualified and experienced industry experts, engineers, technicians, and consultants who provide rotor balancing solutions in hundreds of challenging applications for world-renowned clients. We partner with Schenck, the experts in balancing, to combine their advanced technology and knowledge base with in-depth expertise and software support. We also work closely with our customers, analyzing each specific case to determine the best balancing methods and strategies.

  • Selection of a machine with the proper sensitivity for the component and balance requirement
  • Creation of robust controlled processes for production work to ensure repeatability from lot to lot
  • Accuracy improved by ensuring consistency of the setup (ie. Little details) and rotor specific calibration
  • Repeatability by using “master” rotors to ensure part specific configuration/calibration is correct and consistent
  • In-house true engineering capability to design of component-specific balance tooling that considers dimensions, tolerances and centerline error
  • Drawing upon our Schenck expert balancing colleagues to address unusually complex balancing requirements
  • Selection of appropriate material removal methods (milling/grinding) to address customer requirements
  • Utilizing trained balance personnel

The Balancing Experts

Proper balancing of rotors and other rotating components is essential to ensuring the efficiency, longevity, and safety of your machinery and equipment. Furthermore, a good balancing reduces your equipment’s maintenance requirements, eliminating the down time and costs associated with frequent repairs and part replacement.

Although it’s relatively simple to diagnose an unbalanced part, careful selection of a balancing service provider is crucial to guarantee optimal results. At Test Devices Inc., our technical staff have seen it all and are willing to assist you with your balancing needs.

If you would like to learn more about the risks of improper balancing and how you can avoid them, download our comprehensive eBook, Balancing 101, or contact our team today.

Balancing 101 eBook

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Test Devices 2018 Year in Review

2018 has been a banner year for Test Devices, with expansions in both our facilities and our services, allowing us to better serve our customers as a “dependable partner” and a convenient “one stop shop”. Some of our new and expanded service offerings include in-house machining, eDrive spin testing, and expanded balancing capabilities – thanks to the acquisition of a new Schenck balancing machine.

Facility Updates 

Test Devices’ latest facility upgrade brought significant improvements to our shipping and receiving departments and upgrades to our climate-controlled precision inspection room, which includes the expansion of our Quality Inspection team and the acquisition of a new larger CMM (coordinate measuring machine).

The redesigned facility layout, added floor space, and new equipment allowed us to streamline our workflow and enables us to work more efficiently than ever before. The new shipping and receiving departments are now located to the front of the building with an expanded floor space, and optimally equipped handling areas with additional cranes and staged operations. This new layout minimizes unnecessary movement, creates easier access and an unobstructed flow of materials.

We have also expanded our equipment build area and relocated it to a new section of our facility. This move allowed for a more efficient staging of equipment builds and assembly operations capable of preparing three to four machines simultaneously.

Semi-Finish Machining

As of June, Test Devices now offers in-house semi-finish machining services for aerospace turbine disks. For over a decade, TDI has served leading jet engine OEMs who require forging pre-spinning services—a vital part of producing nascent engine disks that offer the highest performance. While a seemingly simple process, this service is deeply specialized, demanding the highest knowledge and skill level to produce a seamless operation. This newly added machining capability will vertically integrate operational steps and allow TDI to offer more expeditious and higher quality services. By the end of 2018, TDI is on track to ship over 100 semi-finished forgings.

Expanding Aerospace Grade Balancing Services

In 2018, Test Devices grew our balancing capabilities by acquiring a new HM 20 Schenck Horizontal Balancing Machine to support the growing demand for these operations. This high precision, state-of-the-art machine allows TDI to service a broader range of customers with varying rotor balancing needs.

Among the primary benefits of the HM 20 is its hard-mounted bearing design, ensuring rapid changeovers between rotors, which allows Test Devices handle significantly higher volumes of balancing jobs and increase the efficiency of our operational capabilities. The HM 20’s modular design also allows it to be easily modified.

Growth in eDrive Spin Testing Systems

The successful completion of an increasing number of proof and burst tests and 130,000 LCF cycles in 2018 attests to the growing demand for eDrive testing.

We are continuing to enhance our testing and engineering offerings to support eDrive customers in 2018, including advanced rotor growth mapping, high-resolution, high-speed video imaging, expedited fatigue, LCF tests (with RT-CDS and growth mapping), heated spin tests, unbalance budgeting and rotor design engineering support.

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2019 and Beyond

Test Devices Inc. continues to build our services and capabilities in 2019 and we look forward to offering better services for new and existing clients in the aerospace, automotive, and other highly technical industries. We will keep leading the industry by offering the latest services and technology.

To learn how our spin testing, balancing, and other services can help your R&D efforts, prototyping, or manufacturing operation, contact us or request a quote.

TDI Expanding Balancing Services with New Schenck Machine

For the past four decades, Test Devices Inc. has provided our customers with an extensive range of rotational services, including balancing troubleshooting, diagnostics, and calibration. In an effort to meet growing consumer demands and reinforce our commitment to providing the best and most accurate rotor balancing services, we are expanding our balancing capabilities by acquiring a new HM 20 Schenck Horizontal Balancing Machine to support our existing fleet of equipment.

This state-of-the-art machine represents the latest in rotor balancing technology. One of the main benefits of the HM 20 is its hard mounted bearing design, which ensures rapid changeovers between rotors. This feature gives us the ability to handle significantly higher volumes of balancing jobs and increase the efficiency of our operational capabilities.

Additionally, the HM 20 is easily modifiable due to its modular design. A wide range of components and attachments can be added to the unit, increasing its flexibility and allowing us to meet the unique demands of customers regardless of industry or application.

Why Balancing Matters

Rotor balancing is essential to ensure the even distribution of mass in rotating components. Unbalance due to eccentricities between the center of gravity of the rotor and the axis of rotation causes the heavier side of the rotor to exert more centrifugal load. The unbalance in the rotor ultimately leads to excessive noise, vibration, wear, and significantly reduced service life. In some applications, unbalanced rotors are even considered to be a safety hazard if machinery failure can result in personal injury or property damage.

Balancing Services at TDI

At Test Devices Inc., we offer a broad range of timely and cost-effective balancing of virtually any size rotor. Our advanced equipment (including our newly acquired HM 20 Schenck Horizontal Balancing Machine) is capable of providing balancing services for the most complex parts the aerospace industry.

Our services also include the design and manufacture of customized balance tooling for the production of unique and precisely balanced components.

Our staff of highly qualified and experienced industry experts, engineers, technicians, and consultants have provided rotary and balancing solutions in hundreds of challenging applications for many world-renowned clients. As a partner to Schenck, the experts in balancing, we are able to leverage their advanced technology and knowledge base with specific expertise and software support focused on the requirements most important to the aerospace industry. We also work closely with our customers, analyzing each specific case to determine the best methods and strategies for balancing.

Learn More

Proper balancing of rotors and other rotating components are essential to ensuring the efficiency, longevity, and safety of your machinery or equipment. Furthermore, balancing can have the added benefit of reduced maintenance, which can eliminate the costs associated with frequent repairs and part replacement.

Although the diagnosis of an imbalanced part is relatively simple, careful selection of a balancing service provider is crucial to guarantee optimum results. At Test Devices Inc., our technical staff have seen it all and are willing to assist you with your balancing needs.

Download Our Balancing 101 eBook

If you would like to learn more about the risks of improper balancing and how you can avoid them, download our comprehensive eBook, Balancing 101, or contact our team today.

Keep Your Machinery Performing Optimally: Static and Dynamic Balancing

Rotating machinery is omnipresent in industrial use and seen in different fields all across the spectrum. Rotational systems and components are critical to the overall efficiency of businesses in industries such as aerospace, energy storage, automotive, electronics, and medical devices to name a few.

Not sure what to look for in a balancing provider? Read our ebook below:


As the world continues to turn, industry experts rely more and more on rotating machinery to deliver fast, high-level and reliable results.

These sorts of turbomachinery include pumps, compressors, fans, blowers, bearings, engines, motors, and more. An essential to keeping these machine types in optimal condition is awareness and maintenance of its balance.

Understanding Unbalance

Unbalance is known to be one of the most common sources of failure in rotating components and is caused by an uneven distribution of mass around the axis of rotation.

When a system continues to rotate while unbalanced, it generates periodic forces perpendicular to the axis of rotation resulting in a vibration.

Static and Dynamic Balancing

This vibration becomes noisy and apparent as the severity of the unbalancing increases.

Often, such a defect can be mistaken for a simple machine repair or bearing replacement; however, if noise and vibration continue after repairs then the machine is likely signaling that it needs to be balanced.

If unbalance is detected in a rotational system, a balancing service is required to avoid structural defects and in extreme cases, catastrophic failure.

Imbalanced rotational parts can result in excess wear and tear along with structural cracks that could massively affect long-run costs.

A well-balanced turbomachine extends the bearing life and improves overall usage, quality, and accuracy of the machinery, which can be achieved through balancing services.

Static vs. Dynamic

Balancing services evaluate the components and provide a balance correction on materials like plastics or aerospace alloys. Based the type of machine or part, two balancing options can accurately restructure the assembly: Static and Dynamic.

  • Static Balancing is appropriate when an unbalance occurs at a single axial point on a disk-like rotor. In other words, the center of gravity of the object is on the axis of rotation allowing it to remain stationary with a horizontal axis and no braking force. The heavy point here is typically measured in relation to the component centerline.
  • Dynamic Balancing is appropriate for a dual plane unbalance with significant axial length and multi-rotor assemblies. In such a case, the rotation does not produce any resultant centrifugal force or couple and will rotate without application of an external force. Here, the two or more heavy points act independently on the mass centerline and unbalance must be corrected in two planes.

Balance Correction

Upon identifying the balancing service necessary, balance corrections can be done to bring rotational machines back to optimal performance levels. Balance corrections are mainly performed through material removal or mass addition at appropriate locations.

The most commonly used material removal methods are drilling/milling and abrasive material removal. Drills or milling equipment are used to control depth and arch of material removal.

For abrasive material removal, mass is removed through grinding or air-powered sanding equipment. Contrary to a removal process, a mass addition process can be implemented with epoxy, welding metal strips, or mechanical hardware.

Balancing providers are not all created equal. Read our ebook below to find out what to look for:


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Experts in rotational test systems and services are available to assure your machine’s success. These professionals are equipped with quality tools and systems to work with customer specifications for unparallelled spin testing and balancing services that can deliver results for the machinery’s optimal performance.

Two Ways Improper Balancing Can Affect Your Profits

Unbalance is a naturally occurring, and expected phenomenon with all rotating components. It can occur suddenly, or build up over time, and is caused by any number of factors.  Distortions due to stress, uneven thermal distribution, or deposit build-up on the part are a few of the most common causes for unbalance in rotating machinery. Every rotating part will need to be balanced at some point within its lifespan, and it’s vital that the unbalance correction is performed properly.

If you are unfamiliar with the balancing process, there is the possibility that your service provider can incorrectly “correct” the unbalance in your rotating component. This will occur when balance tooling and set-up are not properly developed, or the service provider’s personnel is not fully knowledgeable about the balance process required for the particular rotating component. An improperly balanced part (or batch of parts) can lead to severe consequences to your bottom line.

Delays & Missed Deadlines

As with all manufacturing processes, project schedules are extraordinarily sensitive. However, balancing services for the manufacturing industry usually occur at the very end of the component’s build process, right before delivery to the customer.

If improper balancing occurs and is detected, there’s a high possibility that the delays will directly affect your client’s revenue for the month. So not only will you be paying for the rebalancing, but you run the risk of losing future contracts with your customer. However, the more realistic possibility is that the incorrect balancing is not caught in time, and the rotating components are shipped directly to your customer (which leads to the next potential hit to your bottom line).

Non-Conformance & Part Failures

When improper balancing occurs, it is close to impossible to detect immediately. This means that there is a high probability that non-conforming parts are entering the field. In a best case scenario, the unbalance is detected by your client when assembled into the final product, but before full product launch. You will not only incur the costs of transporting parts back and forth and the second round of balance correction, but you will also incur the metaphoric cost of lost faith from your client. It is also possible that the initial improper unbalance correction will be so severe that the parts will need to be scrapped – a catastrophic scenario for any profit margin. In the worst case scenario, total part failure will occur in the field as a result of an improperly balanced part. The costs of part failure in the field can be ruinous.

The key to avoiding profit loss and potential part failures due to unbalance in your rotating components is in understanding what a good balance provider looks like and fully understanding the process.

For more information on Test Devices Inc’s balancing services, please feel free to request a quote or contact us with any specific questions.

Three Major Ways Your Manufactured Rotating Component Can Become Unbalanced

Unbalance in your rotating component is simply defined as the unequal distribution of weight along your rotor. It is a tricky problem that can sneak up on you unexpectedly. But with the proper knowledge, you can keep an eye out for the major causes of unbalance, and be prepared to address them quickly.

Distortion from Stress

Distortion can occur as a direct result of the manufacturing process and is often the result of a part “adjusting” to relieve stress. Manufacturing processes such as drawing, forging, pressing, etc. will yield internal stresses on parts. If stress relief is not built into the manufacturing process, the rotor will eventually distort to adjust to that residual, internal stress.

Thermal Distortion 

Change in temperature or uneven temperature distribution can also cause major distortions on a rotating part.  Most metals have the capacity to expand when exposed to heat, so when components operate within environments with elevated temperatures, there is the inherent possibility of expansion. If the heat exposure doesn’t happen uniformly over the entire part, certain sections will expand and distortion will occur.

Thermal distortion is a common and natural occurrence with machines that are exposed to (or operate within) elevated temperatures, so components within machines like motors, compressors, turbines,  etc should be regularly evaluated for unbalance.

Deposits & Oil Buildup

If a rotating component is involved in any sort of material handling, it is almost inevitable that buildups of deposits will occur. Minerals (like lime), dirt or dust will begin to build up on rotating parts, cause an initial uneven distribution of weight, and vibrations will begin to occur.

Rotating components that are exposed to oil (ie: lubricated compressors) are also highly susceptible to distortion. Oil has the ability to seep deep into components if left unchecked, and the liquid will accumulate until the buildup causes unbalance, vibrations, and sometimes part failure.

(In the case of deposits and build-up, distortion CAN be avoided before unbalance occurs, if there is a stringent maintenance routine and/or inspection process implemented.)

For more information on the balancing services that Test Devices Inc. provides check our Balancing Services Page or contact us directly.

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