Last Updated on September 19, by Chen
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Journal bearings and thrust bearings serve different purposes in mechanical systems. Journal bearings primarily support radial loads (perpendicular to the axis of rotation) and are ideal for rotary motion systems, providing support to rotating shafts while reducing friction. They can handle higher speeds but require more maintenance. Thrust bearings, on the other hand, are designed to absorb axial loads (along the axis of rotation), making them suitable for applications like elevators or wind turbines. Thrust bearings offer longer service life but are limited by speed restrictions. The choice between the two depends on the specific load direction, speed requirements, and maintenance considerations of the application.
Now that you know a bit about each type of bearing, let’s take a closer look at their individual qualities and compare them side-by-side!
Journal bearings have been used in a variety of applications, from automotive parts to heavy-duty industrial machines. Despite the fact that they are not as commonly found as thrust bearings, journal bearings can be just as effective at reducing friction and wear on rotating components. Let’s take a closer look at the characteristics of journal bearing design, construction, applications, and maintenance.
A key feature of journal bearings is their design; typically made from high-grade steel or other durable materials such as bronze alloys, these devices provide optimal support for turning axles while minimizing friction between them and the surrounding environment. When it comes to construction, there are three main types of journal bearing; split type (which separates into two pieces), sleeve type (designed with grooves around its circumference) and solid type (where one piece fits over the shaft). Each has its own advantages depending on the application demands.
In terms of usage scenarios, Journal Bearings are ideal for slow-speed operations such as pumps and compressors where lubrication systems cannot be installed due to space constraints or environmental concerns. Their low cost also makes them suitable for use in less critical settings like household appliances where longevity is not an issue. In addition, they require minimal maintenance compared to other forms of bearing technology which reduces downtime and repair costs associated with more complex assemblies.
To ensure maximum efficiency however regular inspections should still be conducted so any signs of wear can be identified before damage occurs. This includes checking for loose screws, damaged surfaces and worn seals all factors which could impede performance if left unchecked. With proper care and attention these issues can easily be resolved while allowing users to benefit from smooth operation without compromising safety standards. By understanding the different characteristics associated with journal bearing design we can better appreciate their role in reducing friction on rotational machinery and increase overall productivity across many industries. Moving on let’s now consider how thrust bearings compare in this regard…
Thrust bearings have a different construction, materials, and geometry than journal bearings. They are designed to handle axial loads, whereas journal bearings carry radial loads. In terms of thrust bearing construction, they typically consist of two identical rings with grooves that contain ball or roller elements between them. The balls or rollers allow the inner ring to rotate on its axis relative to the outer ring while carrying heavy loads in one direction.
The material used for thrust bearings is usually steel or an alloy suitable for high temperatures and wear resistance. Special coatings can also be applied to reduce friction and increase service life. Furthermore, the geometry of these components must provide adequate strength and stiffness to handle the load-carrying requirements placed on it by the application.
When considering characteristics that differentiate thrust from journal bearings, such as rigidity, speed capability, start/stop performance, temperature range limitations and lubrication needs; thrust bearings offer higher rigidity due to their inherently stiff design which enables them to maintain form even under heavier loading conditions compared to journal bearings. Additionally, they often require less frequent maintenance because they operate at lower speeds than most other forms of bearings. This makes them ideal for applications where there is limited access for servicing or replacement parts availability is restricted.
In comparison to journal bearings then, thrust bearings possess unique advantages when used in specific operations requiring axial forces only along a single axis. These include better load-carrying capacity over longer periods of time without significant degradation in performance due to heat build-up or fatigue resulting from shock-loads experienced during operation.
Journal bearings bring a number of advantages to a variety of applications. They are known for their high efficiency, superior performance and low cost. Journal bearings also provide excellent load capacity and can operate in both radial and thrust directions.
The main advantage of journal bearings is that they require less maintenance than other types of bearing designs. This makes them the ideal choice for places where frequent lubrication or servicing may not be possible. Their design helps reduce friction between moving parts which results in smoother operation and longer life spans when compared with other types of bearings. Additionally, these bearings have an adjustable clearance so they can be used to accommodate different levels of wear.
In addition to being reliable and durable, journal bearings offer good vibration dampening characteristics due to its ability to evenly distribute loads over larger contact areas on the shafts surface. Due to this feature, journal bearing systems run quieter than many other bearing designs making them suitable for use in environments where noise control is important such as medical facilities or music studios.
Overall, journal bearing systems offer several benefits that make them worth considering for many applications. With their reliability, durability, reduced maintenance requirements and good vibration dampening qualities, it’s no wonder why these bearings are so popular in many industries today.
Although journal bearings provide numerous benefits, thrust bearings offer their own advantages in the power transmission and load capacity categories. To illustrate this concept, consider a factory that manufactures large pieces of machinery with powerful rotating components. The necessary precision and speed require strong support from a bearing system capable of dealing with high loads while minimizing vibration. Thrust bearings are an ideal solution because they can handle both axial and radial loads while also providing dampening against fluctuations caused by external forces.
Thrust bearings operate differently than journal bearings but still provide superior power handling capabilities as well as increased safety for delicate systems like those found in factories or other industrial settings. They use cross-axis contact rather than single point contact to reduce friction between surfaces, resulting in improved energy efficiency and less wear on the parts over time. Additionally, because thrust bearings have fewer moving parts than most journal bearing designs, maintenance costs tend to be lower too.
In terms of specific applications, thrust bearings are often utilized when extreme dynamic loading is needed such as during heavy acceleration or deceleration cycles. They also come in various types depending on the needs of each individual situation including tapered roller type which work particularly well for higher speeds and cylindrical type which works best for heavier loads at slower rates of rotation. In any case, whether it’s rapid acceleration or extended periods under heavy load conditions, thrust bearings will always ensure maximum performance without sacrificing reliability or accuracy along the way.
From these examples, it’s clear that thrust bearings offer many unique benefits over traditional journal bearing designs. Whether you need to manage vibrations due to external forces or accommodate a wide range of speeds and weights within your system design; trust bearings are sure to meet all requirements while helping to minimize overall cost throughout the lifetime of your equipment. Now we’ll discuss some important design considerations when choosing between different types of journalbearings for optimal performance.
Design considerations for journal bearings vary according to the application. When selecting a bearing, each element of design must be considered carefully. These elements include size, load capacity, material and lubrication requirements.
When it comes to sizing, journal bearing diameter should always exceed shaft diameter by at least 10%. This prevents contact between them during operation which can cause wear or other problems. The distance between the shaft centerline and housing wall should also be greater than 1/10th of the bearing’s diameter. Furthermore, proper clearances must be maintained throughout operation in order to ensure optimum performance from the bearing.
Load capacity is another important consideration when selecting a journal bearing. It is essential that the selected bearing can support the required loads without any issues such as excessive friction or premature failure due to high temperatures. Additionally, materials used for both components – shaft and bearing – need to match in terms of hardness and strength so that they don’t experience mismatched wear over time. Lastly, adequate lubrication needs to be provided for long term reliability of these types of bearings.
With all these factors taken into account, appropriate selection criteria can be determined for any given application involving journal bearings. An experienced engineer or technical specialist will have an understanding of how each element impacts the overall performance and durability of these components in order to make informed decisions about their use. Armed with this knowledge, companies can confidently move forward with confidence in their choice of journal bearing designs for various applications ensuring reliable operations for years to come.
The design considerations for thrust bearings are often quite different from those of journal bearings. When designing a thrust bearing, the first thing to consider is its load capacity. This will determine if it can handle the expected loads that need to be supported and how much space is needed for installation. The construction of the thrust bearing should also be considered when selecting the right type of bearing, as some materials may not be suitable for certain applications.
When choosing a lubricant for a thrust bearing, there are several factors to consider such as temperature range, viscosity and compatibility with other components in the system. It’s important to select an appropriate lubricant that will reduce friction while providing adequate protection against wear and corrosion. In addition, regular maintenance checks should be performed on all thrust bearing equipment to ensure proper functioning and safety.
High temperatures can cause significant damage to a thrust bearing over time so it is important to monitor operating temperatures regularly and take action when necessary. Cooling systems may need to be installed or upgraded in order to maintain acceptable levels of operation which can help extend the life span of any thrust bearing system significantly. With these design considerations in mind, you’ll have more confidence about installing effective trust bearings into your system.
Journal bearings are an essential component of many machines, and proper maintenance is key to their longevity. Maintenance for journal bearings includes lubrication, inspection, temperature control, and wear monitoring.
With proper care, journal bearings can provide reliable service for years while reducing downtime due to unexpected mechanical failures. Next we’ll discuss how to maintain thrust bearings effectively
Maintaining a thrust bearing is like taking care of an engine: it needs regular maintenance to keep running smoothly. When it comes to thrusting bearing maintenance, there are certain requirements that must be met in order to ensure its long-term performance and reliability. This includes following a specific maintenance schedule, performing regular inspections, and using the right tips for proper lubrication and cleanliness.
To start, having a regularly scheduled thrust bearing maintenance plan is essential for keeping the bearing’s performance at peak levels. Inspections should take place after every few months or so and more often for bearings used in high-temperature environments. During these inspections, check for any signs of wear or damage such as cracks, chips, corrosion, etc., which can indicate poor lubricant quality or incorrect installation procedures. In addition, make sure that all bolts and other components are securely tightened according to manufacturer specifications.
When it comes to lubrication and cleaning, use only recommended products approved by the manufacturer as an improper application could lead to serious problems with your thrust bearing’s operation. It’s also important to periodically replace seals or other parts if they have become worn out over time due to exposure to extreme temperatures or contaminants. Finally, perform preventative measures before installing new bearings apply grease on the outer surfaces and inspect each part closely prior to installation since even minor defects can cause major issues down the line.
By following these steps carefully during routine maintenance checks and adhering strictly to manufacturer instructions when replacing components or applying lubricants/cleaners, you will help extend the life of your thrust bearing while minimizing downtime caused by unexpected breakdowns or malfunctions.
When it comes to cost comparison between journal and thrust bearings, the long-term cost of both is relatively similar. However, installation costs can vary significantly depending on which type of bearing you choose. Journal bearings tend to be more expensive initially due to their complex design, but this complexity also means that they require less maintenance over time and have a longer lifespan than most thrust bearings. Thrust bearings are generally cheaper upfront because of their simpler build, but they typically need to be replaced sooner than journal bearings due to wear and tear from regular use.
It’s important to factor in the total cost difference when deciding which type of bearing to purchase for your application. If you’re looking for something with minimal initial investment yet still reliable performance, then a thrust bearing might be right for you; however, if you prioritize durability and longevity above all else, then a journal bearing may better suit your needs.
The selection process should take into account not only the price tag but also how each type performs under different conditions and applications. It’s essential to weigh up these pros and cons before settling on either option so that you end up making an informed decision that best suits your project requirements. With careful consideration of both cost factors as well as performance criteria, you can ensure that whichever choice you make will meet your goals while staying within budget. Moving forward we’ll look at some advantages and disadvantages associated with each type of bearing.
When it comes to choosing between a journal bearing and a thrust bearing, there are several factors that must be taken into consideration. From advantages to disadvantages, the decision can be tricky. So, what’s the difference? Let’s take a closer look at both types of bearings and their respective pros and cons.
Journal bearings provide superior performance in terms of low friction when used for slow-speed applications such as motors and pumps. Additionally, they have a relatively high load capacity with minimal maintenance required. On the other hand, these bearings do require lubrication or some kind of oil film in order to prevent metal-to-metal contact from occurring during operation which adds additional cost over time.
Thrust bearings on the other hand offer excellent wear resistance and are well-suited for higher-speed applications including automotive transmissions and engines. They also enable greater efficiency due to their ability to work without lubrication since metal-to-metal contact is avoided through the use of a rolling element interface. However, thrust bearings tend to generate more heat than journal bearings so cooling systems may need to be utilized in certain applications because overheating can lead to premature failure.
Overall, when comparing journal vs thrust bearing options each type has its own set of distinct benefits as well as potential drawbacks depending on intended application requirements making selection an important factor when deciding which will best suit your needs.
Journal bearings and thrust bearings are two different types of bearing assemblies used in various applications. When selecting a bearing, it is important to consider the selection criteria that best suits your application’s requirements. In order to make an informed decision about which type of bearing should be utilized, there are several factors to take into consideration when comparing journal and thrust bearings.
The first factor to consider when evaluating a bearing comparison between journal and thrust types is load capacity. Journal bearings typically provide higher radial loads than comparable thrust bearings, while providing lower axial loads. Therefore, if high axial loads are required for the application, then a thrust bearing would be more suitable than its journal counterpart. Additionally, journal bearings tend to have longer service life due to their lubricated design whereas thrust bearings may require additional maintenance over time as they experience abrasion from the contact surfaces with rotation relative motion.
Another factor to keep in mind when choosing between these two types of bearing assemblies is operating speed. Generally speaking, journal bearings can handle greater speeds since they use oil or grease lubrication; however, some applications may require special designs that allow higher speeds for both types of bearing systems depending on the system parameters such as temperature range and environmental conditions. Furthermore, size availability must also be taken into account when making a final selection between these two types of bearings because certain sizes and configurations may not exist for one type but could be available for another type of assembly.
Considering all these elements together will help you determine which type of bearing assembly works better for your specific needs so you can choose wisely based on relevant information rather than assumptions or guesses. The next section discusses common misconceptions about both types of Bearings Selection Criteria which can further guide your decision-making process..
When it comes to bearings, there are many misconceptions about the journal and thrust bearing types. Some assume that a journal bearing is only used for radial loads, while others believe all thrust bearings can withstand high-speed applications. However, these myths don’t hold true when selecting between the two options.
First off, a journal bearing is not limited to handling only radial loads; some designs can be used in both axial and radial directions. Furthermore, with proper lubrication and maintenance, they can work well in higher-speed applications too. On the other hand, although some thrust bearings may have lower load capacities compared to the equivalents of other designs, this does not mean they cannot handle high speeds—some specific models are designed specifically for such tasks.
Misunderstandings also exist regarding the differences between each type’s ability to reduce friction or vibration levels. While journal bearings do tend to provide better performance than their counterparts in terms of low noise production and vibration dampening capabilities, this doesn’t necessarily mean that thrust bearings lack these features altogether – depending on the design type you choose, certain styles offer similar benefits as those found with journal bearing selections.
It’s easy to see why people might get confused by the nuances between journal vs thrust bearings; however, understanding how each works best under different conditions will help make an informed decision that fits your needs perfectly.
In conclusion, it’s important to understand the differences between journal bearings and thrust bearings before making a decision about which one is best for your application. Both types of bearing have their own pros and cons, so careful consideration should be given when deciding which one will work best for you. Journal bearings are often more cost-effective than thrust bearings and can provide smoother operation in many applications. On the other hand, thrust bearings require less maintenance due to their design and can handle higher levels of axial load with ease. Ultimately, choosing between the two depends on what your individual needs are.
When selecting either type of bearing, there are several factors that should be taken into account: cost, environment, speed requirements, size constraints, etc. Additionally, it’s crucial to dispel any common misconceptions regarding both types – something that this article has aimed to help readers do! By doing a thorough research and considering all available options carefully, customers can make an informed choice that meets their specific needs while also staying within budget.
The formal technical definition of a bearing is a machine element that:
A simpler definition can be found in the name “bearing” itself: a supporting structure designed to “bear” stress or load within a given design.
While the prototypical use case for bearings is an axle rotating in a shaft, they can be engineered to facilitate many different desired ranges of motion. Linear bearings, for instance (see below), allow for linear rather than rotational motion, with the bearing element moving along a rail or rod.
The actual design of the part performing this function can vary widely. Suitable materials for bearings include everything from wood to brass to advanced polymers. Some bearing designs rely on frequent lubrication, while others operate in environments where they can almost never be lubricated (like space). Corrosion-resistant bearings are designed to resist degradation while remaining submerged for long periods of time, while high-temperature bearings need to operate under the extreme conditions of steel manufacturing plants.
Today, bearings are highly engineered components built for highly specific applications, environmental hazards, maintenance requirements, and price-points.
In the prototypical case of a rotational bearing, the “journal” is the part of the shaft which contacts the bearing surface. In the simplest possible case, a bearing is not a discrete device: the journal simply slides over the bearing surface, enduring any friction, heat, and wear generated. While usable in less demanding contexts, bearing designs that do little to reduce friction will create unacceptable magnitudes of heat and wear when used at the speeds and conditions required by demanding modern applications in fields like industrial manufacturing, aerospace, and automotive.
A huge imperative in bearing design, therefore, is reducing friction to improve the bearing’s performance characteristics and lifespan.
Several additional features can be added to reduce friction, first lubrication. Traditionally, this was done by the initial and periodic injection of grease or oil. Today, some self-lubricating bearings embed advanced lubricants into the bearing materials themselves (see Self-Lubricating Bearings, below) reducing manual lubrication needs. Other designs utilize low-friction materials that don’t require lubrication at all under the right operating conditions.
A second option is the addition of a rolling design element to reduce friction while preserving desired load-bearing characteristics. Bearing designs can be usefully divided into two high-level categories based on this addition.
You will notice that many industry sources refer to sleeve/journal bearings as “plain” rather than “plane,” as we refer to them at TriStar.
We think this distinction helps highlight the fact “plain” bearings are by no means relegated to simple or low-load bearing applications.
The “Plane bearing” term focuses on the geometric properties of the bearings rather than the mechanical complexity of the underlying mechanism. Low-friction, self-lubricating plastics mean that the presence of rolling elements is no longer a hard-guide to a bearing’s potential applications.
You can think of a plane bearing as a bearing in its simplest form: any non-rolling element that is incorporated where two surfaces rub together is a plane bearing. Common types of bearings include sleeve bearings and flange bearings (see below for more on both).
“Journal Bearing,” “Sleeve Bearing,” and “Bushing” are all roughly equivalent terms that are used by different industries to describe the same basic bearing design concept.
A sleeve bearing is the simplest design of plane bearing, consisting of a smooth sleeve that is fitted between an axle and bore. Typically, some sort of liquid or particulate lubricant will sit between the journal and axle.
A “bushing” is a closely related classification that can sometimes risk introducing confusion.
The formal definition of a bushing is a thin sleeve or tube which constrains relative motion. But how is this different from a sleeve bearing? It isn’t, necessarily. Some industries simply use the term “bushing” as a quirk of history. In general, we find that a bushing will always refer to a single-component sleeve.
Sleeve bearings are a versatile component employed in just about every sort of design imaginable. Just a few examples include:
This design adds a “flange,” or protruding rim, as a locating mechanism which holds the attached sleeve in place. This flange is attached to a mounting surface that runs perpendicular to the bearing shaft. This additional support is critical in applications with high speeds, heavy loads, or extensive vibration/movement.
In its simplest form, you can think of a thrust bearing as simply a washer. Formally, a thrust bearing provides a bearing for forces that act axially to the shaft. A prototypical example is a propeller shaft on aircraft.
Like other bearing types, thrust bearings can employ a rolling element, with balls or rollers supported inside a ring. Low-friction plastics offer analogous benefits to those they offer in linear or rotational applications: the right materials can withstand axial force with reduced need for lubrication.
Contact us to discuss your requirements of Journal Thrust Plain Bearings. Our experienced sales team can help you identify the options that best suit your needs.
A linear-motion bearing (sometimes called a “linear slide”) provides free motion along a defined path.
This linear motion contrasts with the rotational motion of the prototypical bearing design described earlier in the article. Like a rotational bearing, a linear bearing can be extremely simple--like a wooden desk drawer resting on a wooden slide track. But more complex linear bearing designs allow for less friction, faster motion, and more precise control over range-of-motion.
Examples of linear bearings include everything from desk-drawer slides to seismic shock absorbers that help protect buildings from earthquakes.
In the most common arrangement, a bearing travels along a square rail- or round rod- guide.
A rail provides a track which a linear bearing moves along. The shape and design of this rail may vary depending on how loads will be borne in the intended application. As with, for instance, a curving train track, this rail does not need to be in a straight line.
The rail-mounted bearing mechanism is known as a “carriage” or “block.” The point of contact between the carriage and the rail is known as the “race.”
As with a rotational bearing, friction is generated between these two parts. This friction can either be dissipated with some combination rolling elements, lubrication, and low friction/self-lubricating plastic sleeves.
In general, all the bearing design elements we explore in this article apply to linear bearings as well, including seals, lubrication, and self-lubrication options.
For instance, an oil-infused bronze sleeve is one common low-load design; a simple example is a slide-out track for a drawer. More demanding applications begin necessitating more complex mechanisms. Some linear bearing designs even incorporate a wiper mechanism in front of the bearing to clear dirt and debris from the rail and limit contamination.
Linear bearing applications are as broad as those of rotational bearings. They range from simple furniture drawers up to rollercoasters and high-performance machine tools that require extremely precise motion-regulation.
In this design, a small rib-like structure protrudes from the bearing, fitting in with a corresponding notch/indentation in the rail. This flange guides the bearings along the rail while limiting contact points.
As with other bearing designs, linear bearings can be sealed off using metal or rubber. This practice reduces contamination and prevents lubrication leakage: see Sealed Bearings, below.
Sealed bearings have lubrication injected during the manufacturing process and are then sealed off. They are designed to both:
The seal is not necessarily permanent. Many bearings, for instance, employ a rubber seal that can be readily removed for maintenance (lubrication/cleaning) as necessary.
Like the journal itself, the bearing seal material needs to be carefully calibrated to pressure, temperature, and service life requirements. Selecting the proper seal material and design will maximize seal-life.
Generally, sealed bearings are used in conditions where either frequent re-lubrication is impractical, or dust/dirt contamination is a prime consideration.
The main advantage of open bearing designs is cost and ease of access for maintenance.
If frequent maintenance is planned, the additional costs of a sealed design may not be worthwhile.
In other environments, however, like those full of particulate matter from a manufacturing operation, employing seals (or self-lubricating bearings ) may be a virtual necessity.
Metal-sealed bearings are typically the cheapest sealed bearing options but are harder to access for maintenance.
Rubber-sealed bearings are typically more expensive than metal-sealed but can be more easily opened for re-lubrication. They cannot operate in particularly high temperatures, however.
As with bearings themselves, plastic polymers (PTFE in particular) are opening new frontiers for seals with superior performance characteristics.
Polymer seals, for instance, can stand up to more heat than rubber seals while offering improved corrosion- and chemical resistance compared to metal seals (this is important in any application where harsh cleaning chemicals risk damaging the quality of the seal, affecting its performance and lifespan).
In order to know how to choose plastic bearings, it’s important to first understand how they can fail. While the underlying function is always similar, different bearing types proliferate because different applications and operating environments place very different stresses on bearings.
Bearings fail prematurely due to damage from common issues like inadequate lubrication, particulate or corrosive contamination, overload, and improper installation. Bearing failure causes can vary widely depending on the material used and the operational environment.
Meanwhile, the operational and cost implications of bearing failure/maintenance/replacement can vary widely between applications. For a piece of manufacturing equipment that must be stopped daily for an inspection, for instance, frequent lubrication or occasional bearing replacement may be a non-issue. In these situations, the added cost of more advanced bearing solutions may offer few advantages. But applications at the other extreme (like bearings for satellites) may need to succeed in conditions where they will never be maintained.
Careful considerations of bearing material properties (e.g, mechanical, thermal, and electrical limits) is critical to preventing premature bearing failure. Evaluating manufacturer-supplied spec sheets, and utilizing tools like our Bearing PV calculator can help ensure successful outcomes.
We drive into key factors that can cause bearing failure in more detail below.
When thinking about bearing failure it's also worth learning what signs to look for to indicate that a bearing is getting ready to fail.
TriStar engineers have decades of combined experience in evaluating (and preventing!) bearing failure. We encourage you to reach out if you need assistance with your specific applications.
The relative importance of the bearing failure modes discussed above can vary widely depending on where a bearing is employed and how often it can be cost-effectively replaced or accessed for maintenance.
Environmental effects can alter a bearing’s expected lifespan by up to 90%. With this magnitude of environmental lifespan differential, selecting the right bearing for the right environment is instrumental to a design’s ultimate performance and reliability.
A few concise examples below demonstrate how bearings need to be carefully selected to reflect the conditions where they will be expected to operate.
Environments like steel mills, construction sites, and food processing lines include high levels of dust and other matter that can contaminate a bearing. Bearings that operate in these environments need to be sourced with this contamination risk in mind: particulates ranging from food debris to metal shavings become abrasive as they build up over time. This abrasion will affect both bearing seals (letting in more particles and/or water over time) and the bearings themselves.
You can read more about using bearings in dusty environments in our article here.
The dust contamination discussed above becomes worse as more grease accumulates inside a bearing. As lubricants become contaminated, their abilities to dissipate heat and reduce friction are sharply reduced. At best, bearing life is shortened. At worst, this contamination is a recipe for unplanned failures and downtime.
This makes regular cleaning of lubricated bearings essential—a key design concern for bearings that are difficult to access, will be maintained infrequently, or that operate in environments too dirty to be practically cleaned at required intervals.
While self-lubricating bearings may still require some level of lubrication, their reduced lubrication need creates key maintenance advantages for dirty operating environments
Vacuum environments tend to not only introduce maintenance difficulties but unique modes of failure. Plastic bearings, for instance, are often preferred in bearing designs that need to function in vacuums to eliminate lubrication requirements. But plastics need to be carefully selected for vacuum-use: some plastics exhibit out-gassing and particulate-shedding that cannot be easily vented in a vacuum.
Any bearing requiring regular lubrication comes with the risk of lubricant contaminating the surrounding environment. When facing design requirements for clean operation (stemming from ISO standards, government regulations, or client demands for sustainable best practices), leakage effectively becomes a mode of bearing failure. With this risk in mind, self-lubricating plastic bearings offer important advantages for clean operation in these environments.
Evaluating bearing material properties is key to success for any application. A plastic vs metal bearings comparison, for example, reveals that plastic bearings are lighter and more corrosion-resistant, though metal bearings may offer higher load capacities. Each material has benefits and potential downsides to consider.
Wood may not be the first material you think of for bearings, and it is relegated to specialty applications today. But wood bearings provide useful historical context: they illustrate that engineers have been carefully selecting materials to fit bearing performance criteria for much of recorded history.
There is evidence that Phoenician boat builders used wooden bearings for rudders as early as years ago. The right woods are corrosion resistant, allowing them to thrive in submerged applications like rudders or propellers shafts. In the old-world, the ultra-hard wood Lignum Vitae was a popular choice--it’s natural oils provided built-in lubrication while its extreme density helped it hold up under stress. Later, bearing makers would impregnate wooden bearings with animal oils to achieve a similar self-lubricating effect.
Today, composite bearings offer key performance advantages over wood in underwater applications, but wooden bearings were the first example of a bearing material being carefully selected for desirable mechanical bearing properties.
Bronze is a commonly used material that comes in a huge variety of different alloys and compositions--this variety makes bronze a popular choice of bearing material, as a material very close to the precisely desired specification can be sourced. Bronze bearings have strong characteristics for shock, impact, and corrosion resistance.
Bronze bearings do require lubrication both at installation and during operation, which can make them a poor choice for designs that are difficult to access for frequent maintenance. This limitation is why replacing bronze bearings with a self-lubricating option (see below) offers an attractive proposition for many companies.
A common traditional choice for industrial applications, steel bearings can handle extremely high loads and high rpms. Stainless steel bearings offer improved corrosion resistance compared to other steel grades, but potential drawbacks still include relatively high weight and high noise.
Another common traditional choice, cast iron bearings have a sufficiently low friction coefficient to be employed on a steel shaft. Cast iron glazes over time which helps reduce wear.
For bearings, PTFE is not only useful as a structural material but as a lubricating medium for self-lubricating bearings (more on this below).
Useful properties include low friction coefficient, corrosion resistance, low electrical conductivity, hydrophobia, and a broad range of tolerable temperatures.
So, which of these plastics is best? As with the other bearing selection parameters discussed in this article, it all depends on the application. In fact, these plastics can be blended with one another, or with non-plastic materials, to generate the desired characteristics in terms of performance, maintenance needs, and cost.
For a detailed look at the properties of different plastic polymer offerings from TriStar, explore our materials database here.
Self-lubricating plastic materials provide low-maintenance bearing options, eliminating the need for regular lubrication and reducing downtime.
These bearings have a lubricant like PTFE, graphite, or silicon integrated with the rubbing surface of the bearing itself. As moving parts rub together, this lubricant dynamically disperses over time.
Self-lubricating plastic polymer bearings utilize two different mechanisms to transfer lubrication media:
For more on how self-lubricating polymers work, check our our expanded blog post on the subject.
Employing one of these designs is important in applications where frequent re-lubrication is impractical or unduly costly, in extremely high-friction environments, or in environments where traditional liquid lubricants represent too great a risk for contamination/leakage.
Because inadequate lubrication is the number-one cause of bearing failure, ending the need for lubrication not only simplifies maintenance but dramatically reduces premature wear that accumulates during inevitable maintenance intervals. Grease and other lubricants also exacerbate contamination issues by helping dust and dirt stick in the bearing mechanism, another long-term wear-driver that self-lubricating options eliminate.
TriStar is the exclusive North American distributor of Rulon, a family of PTFE-based plastics purpose-built for the functional requirements of demanding applications like bearings. Like other plastics, it is available in a wide variety of formulations (in fact, over 300).
For a deeper look at Rulon and some key formulation options, please see our white paper:
More advanced approaches to metal bearing design allow for self-lubricating capabilities while retaining some of metal’s desirable structural characteristics.
TriStar’s TriSteel™, for instance, consists of a special polymer lining with a metal backing. The liner is impregnated into a sintered porous bronze inter-layer. Both materials can be precisely specified depending on the application. This design takes advantage of steel (zinc/copper-plated or stainless) for structural and mechanical support while utilizing a polymer liner for improved wear characteristics and self-lubrication.
Learn more about TriSteel on our product webpage or view the brochure.
Composite bearings are made from a combination of materials, such as fiber-reinforced resin or plastic. The composite material can be combined with PTFE to create a lightweight, self-lubricating design.
Composite bearings offer dramatic weight advantages compared to metal-based bearings. Read about some other benefits of composite bearings here. The composite itself can be customized to meet specific application requirements. A composite liner can be applied on a metal-backing for added strength.
TriStar’s CJ composites are a great example of a composite bearing solution. This design utilizes multiple layers. The innermost layer consists of a synthetic fiber/PTFE layer. The second layer consists of epoxy coated high-angle glass filaments. The outermost layer consists of epoxy coated low-angle glass filaments.
This construction allows for a bearing that is lightweight, high-strength, and fatigue-resistant, often an ideal choice for non-lubricated high-load/low-speed applications. CJ bearings provide excellent resistance to impact and shock loads. They are also capable of withstanding a high degree of shaft misalignment: the composite wall acts like a spring and the thicker the wall section of the bearing the greater the deflection for a given load.
For more information on CJ Composite bearings view our CJ web page or check out the brochure.
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