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Choosing the most appropriate type of coupling to use in servo applications can be confusing. This article examines the pros and cons of the various technologies.

Selecting a coupling for a servo application can be a complex process. It involves many different performance factors, including: torque, shaft misalignment, stiffness, rpm, space requirements, and others, that all must be satisfied for the coupling to work properly. Before selecting a coupling, it is helpful to know the specifics of these issues for the application for which the coupling is to be used. Many different types of servo couplings exist with their own individual strong and weak points. This article is designed to introduce end users to the different types of couplings available for servo applications. It also helps the user select the proper coupling for their application by highlighting the factors that should be considered in the decision making process and how they relate to the different product offerings available.

Check out our Servo Coupling Comparison Guide for a performance breakdown of every Ruland servo coupling.

Beam Couplings

Beam couplings are manufactured from a single piece of material, usually aluminum, and utilize a system of spiral cuts to accommodate misalignment and transmit torque. They generally have good performance characteristics and are an economical choice. For many applications, beam couplings are a good place to start. The single piece design allows the coupling to transmit torque with zero backlash and no maintenance required.

Beam couplings are a good general purpose choice.

Two basic variations on this theme exist: a single beam style and a multiple beam style. The single beam style has one long continuous cut that usually consists of multiple complete rotations. This results in a coupling that is very flexible and yields light bearing loads. It is able to accommodate all types of misalignment, but works best with angular misalignment and axial motion. Parallel misalignment capabilities are reduced because the single beam is required to bend in two different directions at the same time, creating larger stresses in the coupling that could cause premature failure.

Although the long single beam allows the coupling to bend easily under misalignment conditions, it has the same affect on the rigidity of the coupling under torsional loads. The relatively large amount of windup under torsional loads adversely affects the accuracy of the coupling and reduces its overall performance.

Single beam couplings are an economical option that are best utilized in lower torque applications, especially in connections to encoders and other light instrumentation.
Multiple beam couplings, which usually consist of 2 or 3 overlapping beams, attack the problem of low torsional rigidity.

The use of multiple beams allows for the beams to be shorter without sacrificing much of the misalignment capabilities. The shorter beams make the coupling stiffer torsionally and overlapping them so the beams work in parallel increases the allowable maximum torque. This makes them suitable for use in light duty applications with connections such as a servo to a leadscrew. This increase in performance does not come without penalty: bearing loads are increased by a sizeable amount over the single beam variety but, in most cases, remain low enough to protect bearings effectively. Some manufacturers take the multiple beam concept to another level, also. Instead a single set of multiple cuts,  two sets of multiple cuts are utilized. The use of multiple sets of cuts gives the coupling additional flexibility and misalignment capability.

It also adds a dimension to the misalignment capability of this type of coupling by more readily accepting parallel misalignment. In constrast to couplings with one beam or a single set of beams, under parallel misalignment, one set of beams bends in one direction and the second set bends in the other direction making the coupling more adaptable to this type of misalignment.

Most commonly, aluminum versions of these couplings are used. However, several manufacturers offer designs available in stainless steel also. The use of stainless steel, in addition to corrosion protection, also increases the torque capacity and stiffness of the coupling to sometimes double that of aluminum parts of the same design. The increase in torque and stiffness is off-set by a dramatic increase in mass and inertia.

Often times the negative affects will outweigh the positives and force the user to look for another type of coupling. In applications using smaller motors, a large percentage of the motor&#;s torque is used to overcome the inertia of the coupling, seriously reducing the performance of the system.

Oldham Couplings

The oldham coupling is a three piece coupling comprised of two hubs and a center member . The center disk, which is usually made of a plastic or, less commonly, a metallic material, is the torque transmitting element. Torque transmission is accomplished by mating slots in the center disk, located on opposite sides of the disk and oriented 90 degrees apart, with drive tenons on the hubs. The slots of the disk fit on the tenons of the hub with a slight press fit. This press fit allows the coupling to operate with zero backlash.

Oldham couplings have high parallel misalignment capability.

Over time it should be noted that the sliding of the disk over the tenons will create wear to the point the coupling will cease to be zero backlash.The disks, however, are inexpensive items that are easily replaced and a new insert will restore the couplings original performance

In operation, the center element slides on the tenon of the hub to accommodate misalignment. Because the only resistance to misalignment is the frictional force between the hub and disk, oldham couplings have bearing loads that do not increase as misalignment increases. Unlike other types of couplings, there are not any bending members which act as springs, causing bearing loads to increase as the shafts become further misaligned.

However, these ratings can be surpassed at the expense of coupling life. The ability to choose different disk materials is an advantage of this type of coupling. Several manufacturers offer choices of material to meet application needs.  Generally. one material is best used zero backlash,  high torsional stiffness and torque are required, and another material for applications that have less precise positioning requirements, do not require zero backlash, and can benefit from a coupling that can absorb some vibration and reduce noise. Nonmetallic inserts are also electrically isolating and can act as a mechanical fuse. hen the plastic insert fails, it breaks cleanly and does not allow any transmission of power, preventing other damage from occurring to more expensive machinery components. The area this design is particularly well suited is handling relatively large amounts of parallel misalignment (from .025" to .100" or more depending on coupling size). Coupling manufacturers generally provide smaller misalignment ratings that allow users to obtain maximum life.

Zero Backlash Jaw Couplings

There are two general types of jaw couplings: the conventional straight jaw couplings and curved jaw zero backlash jaw couplings. Conventional straight jaw couplings are not typically well suited to servo applications accuracy of torque transmission is required.

Zero backlash jaw couplings are a variation on the same theme, but the differences in design make them well suited to servo applications.The curved jaws help to reduce deformation of the spider, limiting the effects of centrifugal forces during high speed operation.

Jaw couplings are the best for shock absorption.

Zero backlash jaw couplings consist of two metallic hubs and an elastomer insert , which is commonly referred to in the industry as a &#;spider".The spider is a multiple lobed insert that fits between the drive jaws on the coupling hubs with a jaw from each hub fitted alternately between the lobes of the spider. As in the oldham coupling, there is a press fit between the jaws and the spider that allow the coupling to remain zero backlash. In contrast to the oldham coupling, the torque disk is in shear under torsional loads, the jaw coupling&#;s spider operates in compression.

When using a zero backlash jaw coupling the user must be careful not to exceed the manufacturer&#;s rating for maximum torque with zero backlash which can be significantly below the physical limitations of the spider. If this occurs, the spider can be compressed so that there is no longer a preload and backlash will occur,  possibly without the user noticing until a problem occurs.

Jaw couplings are well balanced and are able to handle high RPM applications very well ( manufacturers rate speeds up to 40,000 RPM ), but are not able to handle very large amounts of misalignment, especially axial motion. Large amounts of parallel and angular misalignment cause bearing loads that are higher than most other types of servo couplings. Another factor that the user must be aware of is the situation when a jaw coupling fails. If a spider fails, the coupling will not disengage. The jaws from the two hubs will mate similar to teeth on two gears and continue to transmit torque with metal to metal contact which, depending on the application, may be desirable, or could cause problems in the overall system the coupling is installed. An advantage of the jaw coupling is the ability to mix and match spiders based on the application. Manufacturers of zero backlash jaw couplings offer multiple materials with different hardnesses and temperature capabilities that allow the user to choose exactly the insert that meets the application&#;s performance criteria.

Disc Couplings

Disc couplings are torsionally rigid with high misalignment capability.

Disc couplings are comprised of, at a minimum, two hubs and a thin metallic or composite disc that is the torque transmitting element. The disc is fastened to the hubs usually with a tight fitting pin that does not allow any play or backlash between the disc and hubs. Some manufacturers offer disc couplings with two discs separated by a rigid center member and attached to a hub at each end.

The difference between the two variations is quite similar to the difference between the single beam style coupling and the multiple beam coupling consisting of two sets of cuts.The single disc coupling is not very adept at accommodating parallel misalignment due to the complex bending of the disc that would be required.The two disc style allows each disc to bend in opposite directions to harness the parallel off-set.

The properties of this type of coupling are similar to that of bellows couplings. In fact the way the couplings transmit torque in general is very similar. The discs are very thin, allowing them to bend easily under misalignment loading which allows the coupling to accept large amounts of misalignment (up to 5 degrees) with some of the lowest bearing loads available in a servo coupling. Torsionally, the discs are very stiff. The disc coupling has stiffness ratings slightly lower than that of bellows couplings. A downside to these couplings is that they are very delicate and prone to damage if misused or installed improperly. Special care must be taken to insure that the misalignment is within the ratings of the coupling for proper operation.

Bellows Couplings

The bellows coupling is an assembly of two hubs and a thin walled metallic bellows. The assembly is created in most cases by either welding the hubs to the bellows or by using an adhesive of some variety. Although other materials can be and are used, the two most common materials for the bellows are stainless steel and nickel.

Nickel bellows are manufactured using an electrodeposition method. This method involves machining a solid mandrel in the shape of the finished bellows. The nickel is electrodeposited onto the mandrel and the mandrel is then chemically dissolved, leaving behind the finished bellows. This method allows the manufacturer to precisely control the wall thickness of the bellows and also allows for thinner walls than other methods of bellows forming. The thinner walls give the coupling greater sensitively and responsiveness making them ideally suited for extremely precise small instrumentation applications. However, the thinner wall also reduce the torque capacity of the bellows putting a limiton useful applications.

Bellows coupling are the most torsionally rigid.

Stainless steel bellows are stronger than nickel versions and are usually manufactured with a process called hydroforming. A thin walled tube is placed into a machine and hydraulic pressure is used to form the convolutions of the bellows around specialized tooling. The characteristics of bellows make them an ideal method for transmitting torque in motion control applications. The uniform thin walls of the bellows allow it to bend easily under loads caused by the three basic types of misalignment between shafts (angular, parallel, axial motion). Generally bellows allow for up to 1-2 degrees of angular misalignment and .010" - .020" of parallel misalignment and axial motion.

The thin, uniform walls result in low bearing loads that remain constant at all points of rotation, without the damaging cyclical high and low loading points found in some other types of couplings. All of this is accomplished while remaining rigid under torsional loads. Torsional rigidity is a key factor in determining the accuracy of the coupling. The stiffer the coupling, the more accurately motion is translated from the motor to the driven component. In the area of servo couplings, bellows type couplings are some of the stiffest available, making them ideal in high performance applications that require a high degree of accuracy and repeatability. Some manufacturers offer bellows couplings with stainless steel hubs, which can be useful in applications corrosion resistance is important. The mass of stainless steel hubs does reduce some of the benefit of this type of coupling. The use of aluminum hubs with a bellows results in a coupling with very low inertia, a feature that is very important in today&#;s highly responsive systems. Some manufacturers of bellows coupling balance their couplings as a standard offering making them well suited for higher rpm applications (10,000 RPM ) as well.

Rigid Couplings

Rigid coupling are very precise and requires no misalignment.

As the name implies, rigid couplings are torsionally rigid couplings with virtually zero windup under torque loads, but they are also rigid under loads caused by misalignment. If any misalignment is present in the system the forces will cause the shafts, bearings or coupling to fail prematurely. This also means that the couplings cannot be run at extremely high rpm&#;s since they cannot compensate for any thermal changes in the shafts that can be caused by heat buildup from high speed use. This also means that the couplings cannot be run at extremely high rpm&#;s since they cannot compensate for any thermal changes in the shafts that can be caused by heat buildup from high speed use. However, in situations misalignment can be tightly controlled rigid couplings offer excellent performance characteristics in servo applications.

Although in the past many people wouldn&#;t consider using this type of coupling in a servo application, recently smaller sized rigid couplings, especially in aluminum, are increasingly being used in motion control applications due to their high torque capacity, stiffness, and zero backlash.

In conclusion

Choosing the proper servo coupling for an application is a critical part of total system design and greatly affects its overall performance capabilities. For this reason, considering the coupling early in the design process and aligning the coupling performance attributes with the functionality goals of the system can eliminate many problems that typically occur in motion control applications. Each of the couplings discussed have their own individual characteristics that make them ideal for many different uses. A single type of coupling, however, cannot be applied to every application in the field. This leads to the wide variety of couplings currently available and gives the design engineer the ability to select the best possible coupling to maximize system performance and durability

10 Requirements You Must Check Before Purchasing a Servo Gearbox

In the bustling world of food and beverage manufacturing, the efficiency and precision of your operations are paramount. Every drop of beverage filled, every pastry baked, and every packaging sealed are processes where even the slightest discrepancy can impact product quality and, subsequently, brand reputation. Central to ensuring these operations run seamlessly is the unsung hero of the manufacturing floor: the Servo Gearmotor. Its pivotal role in driving machinery often goes unnoticed, but its selection? That can make all the difference between a smooth production line and unexpected downtimes. 

With its stringent safety standards and relentless production schedules, the food and beverage industry demands gearmotors that are robust and tailored to the specific requirements of individual processes. Selecting the right gearmotor can seem like a daunting task, given the myriad of technical parameters and environmental considerations involved. However, the decision becomes markedly simpler with a structured approach and a clear understanding of what's at stake. 

This guide aims to illuminate the intricacies of Servo gearbox selection, offering insights explicitly tailored to the unique challenges and needs of the food and beverage industry. Whether you're setting up a new production line, upgrading existing machinery, or simply aiming to optimize operations, this guide will equip you with the knowledge needed to make an informed choice&#;a choice that aligns with your production goals, ensures efficiency, and, most importantly, stands the test of time in the demanding world of food and beverage manufacturing. Let's embark on this journey of understanding and decision-making together. 

Why Servo Gearmotors in Food & Beverage Manufacturing?

1. Precision: The food and beverage industry necessitates exact measurements, especially when dealing with ingredient mixing or product filling. A minor inconsistency can compromise the product's quality. Servo gear motors offer unparalleled precision in terms of speed and position, ensuring consistent outputs batch after batch. 

2. Flexibility: Different processes within the industry require varying speeds and torque. Servo gearmotors can adapt swiftly, accommodating different operations without the need for mechanical adjustments or complete system overhauls. 

3. Efficiency: In an environment where machinery often operates continuously, energy consumption becomes a significant concern. Servo gearmotors are renowned for their energy efficiency, ensuring that operations are not only consistent but also cost-effective. 

4. Compact Design: With space often at a premium in manufacturing plants, the combined design of the servo gearmotor ensures that it occupies minimal space without compromising on its capabilities. 

In the Context of Food & Beverage Production 

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Consider a bottling plant. The bottles must be filled to a precise level, capped accurately, and labeled in exact positions. A servo gear motor's precision ensures that each bottle is uniformly filled, reducing wastage. Its flexibility means that the same production line can adjust to different bottle sizes or fill levels with minimal intervention. Its efficiency ensures that the plant can run for extended periods without incurring exorbitant energy costs. And its compact nature means integrating it into existing systems or setting up new ones becomes a hassle-free experience. 

In essence, while it might seem like just another component in the vast machinery landscape, the servo gearmotor's role is pivotal. As we delve deeper into the intricacies of selection criteria in the following sections, it's essential to remember the fundamental value this component brings to the table. 

Key Factors in Servo Gearmotor Selection

Selecting the right servo gearmotor is not just about matching specifications from a catalog. It's about understanding the unique demands of your food and beverage operations and ensuring that the gearmotor can meet these requirements day in, day out. Let's dissect the critical parameters you should consider. 

1) Torque Requirements 

• The Power Behind Operations: At its core, torque is the rotational force exerted by the motor. In the context of food and beverage manufacturing, it can be the difference between smoothly kneading a thick dough and the machinery stalling mid-process. 

• Continuous vs. Peak Torque: Continuous torque is what your motor will use during regular operations. However, during sudden load changes, like when starting a mixer full of ingredients, the motor might momentarily require more power&#;this is where peak torque comes in. Balancing these two ensures smooth operations without overburdening the motor. 

• Determining Torque Needs: One must consider the heaviest load the gearmotor will encounter. Will it be stirring a vat of viscous liquid? Driving a conveyor belt laden with goods? Each task will have its own torque demands. 

2) Speed Requirements 

• Versatility in Motion: Different stages in food processing might require different speeds. The ability of a servo gearmotor to adapt to these changes is essential. For instance, a bottling line might fill bottles at one speed but cap them at another. 

• Understanding RPM: The Revolutions Per Minute (RPM) denotes how fast the motor turns. While high RPMs can be useful for tasks like filling, lower RPMs, offering more torque, might be essential for operations like mixing. 

• Variable Speed Operations: This is especially vital if your production line handles diverse products. A motor that can seamlessly transition between speeds ensures minimal downtime during changeovers. 

3) Backlash Considerations 

• The Precision Detail: Backlash refers to the slight movement or "play" in the motor when changing direction. In processes requiring high precision, like accurate positioning of labels, minimal backlash is crucial. 

• Reduced Wear and Tear: A servo gearmotor with minimal backlash not only ensures precision but reduces wear and tear, ensuring a longer operational life. 

4) Gear Ratio 

• Balancing Act: The gear ratio affects how motor speed is translated into output speed of the shaft. It's a balance between speed and torque. A high gear ratio might give more torque but at a reduced speed, and vice versa. 

• Tailoring to Task: The right ratio ensures the motor operates within its optimal range, neither too fast, risking wear, nor too slow, compromising efficiency. 

As we continue to delve deeper into the other factors, remember that every production line is unique. While these guidelines provide a solid foundation, always consider the specific demands of your operations and how they might vary over time. Upfront investment in understanding these nuances ensures long-term operational excellence. 

5) Durability and Lifespan 

• Endurance in Adverse Conditions: The food and beverage manufacturing environment can be tough. From splashes of hot liquids to acidic spills or even the everyday wear and tear from continuous operations, a gearmotor faces numerous challenges. Durability isn't just a perk&#;it's a necessity. 

• Material Matters: Stainless steel gearmotors, for instance, offer excellent resistance to corrosion, making them ideal for areas exposed to frequent washdowns or acidic ingredients. On the other hand, certain high-strength alloys might be better suited for applications demanding higher torques. 

• Maintenance Implications: A durable gearmotor might have a higher upfront cost but consider the long-term savings. Fewer breakdowns mean reduced downtimes and maintenance costs, contributing to a lower total cost of ownership. 

6) Efficiency Metrics 

• Economic and Environmental Concerns: Energy-efficient gearmotors not only reduce operational costs but also contribute to a smaller carbon footprint&#;a critical consideration in today's environmentally-conscious world. 

• Heat Dissipation: An efficient gearmotor typically generates less heat. Excessive heat can compromise lubricants, leading to increased wear and potential failure. Especially in the food and beverage industry, where hygiene is paramount, reduced heat also minimizes the risk of food products getting spoiled due to elevated temperatures near the machinery. 

• Optimized Operations: Efficiency isn't just about electricity consumption. It's also about how effectively the motor translates that energy into movement, ensuring operations are smooth and consistent. 

7) Size and Weight Constraints 

• Space-Efficient Designs: In crowded manufacturing facilities, space is at a premium. Compact gearmotors that don't compromise on power can be invaluable, allowing for more efficient layouts or even the addition of more machinery if required. 

• Stability Concerns: While compactness is essential, one must also consider the gearmotor's weight. A gearmotor that's too light might not offer the stability needed, especially in high-torque applications, leading to vibrations or even shifts in positioning. 

• Integration with Existing Systems: Especially when upgrading or replacing gearmotors, size and weight play a pivotal role in ensuring the new unit can fit seamlessly into the existing infrastructure without necessitating significant overhauls. 

Choosing a gearmotor isn't a mere technical exercise&#;it's a strategic decision. The right choice enhances operational flow, reduces downtimes, and ensures the quality of the end product. As we venture further into the nuances of selection, keep in mind the overarching goal: optimized, uninterrupted, and efficient production. 

8) Mounting Configuration 

• Foundational Stability: The way a servo gearmotor is mounted directly impacts its performance and longevity. The right mounting ensures the motor remains stable, reduces vibrations, and optimizes power transmission. 

• Types of Mountings: 

• Flange Mounting: Often used for direct drives where the motor is coupled directly to the machinery. Its design facilitates precise alignment, ensuring optimal power transfer and reduced wear. 

• Foot Mounting: This traditional method, using bolted feet, provides a robust base, especially for heavier motors or those exposed to significant loads. 

• Face Mounting: Ideal for compact spaces, this mounting type allows the motor to be attached directly to the machinery's face or side. 

• Torque Arm Mounting: Particularly used when the motor experiences significant axial or radial loads, this method stabilizes the motor, ensuring consistent performance. 

• Alignment and Precision: Improper alignment can lead to premature wear, inefficiencies, and even system failures. Ensure the mounting configuration chosen aligns perfectly with the operational machinery to guarantee seamless operations. 

9) Environmental Conditions 

• Withstanding the Elements: Food and beverage manufacturing plants can vary significantly in their environmental conditions. From cold storage areas to hot baking zones, the servo gearmotor must be able to function optimally across diverse environments. 

• Protection from Contaminants: Flour dust in a bakery, mist in a beverage bottling area, or even the oils in a fryer zone can impede gearmotor performance. Choose units with appropriate sealing and protective measures to prevent ingress of such contaminants. 

• Temperature Fluctuations: Motors designed for high-temperature environments should dissipate heat effectively, ensuring they don't overheat. Conversely, those in colder areas should be able to start and operate without issues even at lower temperatures. 

• Washdowns and Cleanings: In the food and beverage industry, regular cleaning is a necessity. Gearmotors should be resistant to frequent washdowns, ensuring neither water nor cleaning agents compromise their functionality. 

10) Budget and Cost Implications 

• Initial Investment vs. Long-Term Gains: While it's tempting to opt for a cheaper gearmotor upfront, consider the long-term implications. A slightly pricier, high-quality motor might offer better efficiency, durability, and reduced maintenance costs, translating to savings in the long run. 

• Total Cost of Ownership: Beyond the purchase price, consider factors like installation costs, energy consumption, potential downtimes, and maintenance expenses. An all-encompassing view of costs ensures a well-informed decision. 

• Warranty and Support: A good warranty can be indicative of a manufacturer's confidence in their product. Additionally, manufacturers that offer robust post-sales support can be invaluable in the event of unforeseen issues. 

The complexity of selecting the right servo gearmotor is undeniable. However, with a methodical approach, focusing on each of these critical factors, one can ensure a choice that bolsters the manufacturing process, ensuring consistency, quality, and efficiency. 

The food and beverage manufacturing sector demands precision, efficiency, and reliability. Making the right choice in servo gearboxes is an investment in the very essence of your operations. 
 

Throughout this blog, we've walked you through the facets of gearmotor selection. But beyond the technicalities, the choice also depends on a partner who brings innovation, quality, and support to the table. Sumitomo Drive Technologies does just that with our Planetary, Inline, and Right-Angle Servo gearbox options: The Cyclo Servo, Servo Bevel BuddyBox 4, and Servo Hyponic.

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