iglidur® Frequently Asked Questions

How is an iglidur® plain bearing fixed in place in a bearing housing?

The iglidur® plain bearings are designed in such a way that they can be pressed into a housing (with an H7 tolerance) with the nominal size of the bearing outer diameter and are then secured by the press-fit. This is achieved by the so-called press-in excess, i.e. the outside diameter of the bearing is, depending on the nominal size, about 0.1 to 0.25 mm larger than the housing in the non-pressed state. The inner diameter also reaches its final dimensions and tolerances only when pressed in.

Why are there so many different iglidur® materials?

The variety of iglidur® materials has evolved over the past almost three decades from a wide variety of customer requirements. The development of a good plain bearing material often has something to do with squaring the circle. If an improvement is made in one particular direction, this usually happens at the expense of another specification. – Most technical applications can be covered by the five standard materials iglidur® G, J, X, W300 and M250.But when it comes to very specific or demanding applications, exhausting the last technical reserves or the last price-performance optimisation for high volume, the other iglidur® materials are becoming increasingly important. Moreover, the limits of use of non-lubricated plain bearings have shifted further in the last few years due to new iglidur® materials.

How can I find the right iglidur® material?

With a little application data, it is possible to make a preliminary selection with the help of the iglidur® product finder or to calculate the service life with the iglidur® service life calculator. The large variety of materials is quickly culled, leaving behind only the suitable materials.

The iglidur® expert tells me that iglidur® W300 and iglidur® J are the most durable materials.Which one should I choose?

Both iglidur® J and iglidur® W300 belong to the most wear-resistant all-round bearings in the iglidur® range. If the service life is comparable and sufficient in both cases, the boundary parameters should decide the selection of the application: iglidur® J is ideal for wet areas due to low moisture absorption and good media resistance, and iglidur® W300 offers more temperature reserves.

Why do iglidur® plain bearings not need any lubrication?

Due to the special structure of iglidur® materials, which are usually composed of a thermoplastic matrix, fibre reinforcements and so-called solid lubricants. The good wear and friction properties of the matrix or base material are additionally enhanced by the solid lubricants. During operation, there are always enough particles of solid lubricant on the surface of the bearing. Additional lubrication from the outside with grease or oil is usually not required or not useful. Video regarding the question

When I measure the iglidur® plain bearings, I find them to be considerably larger than indicated in the catalogue.Why is this?

iglidur® plain bearings are press-fit bearings for housings with a standard H7 hole. This press-fitting of the bearings fixes the bearings in place in the housing, and the final inner diameter of the plain bearings is not arrived at until the bearing has been press-fitted.The bearing size is checked when the bearing has been mounted in a hole with the minimum specified dimensions. If the bearings are measured before they are press-fitted, the outer diameter and the inner diameter are greater than when the bearings have been mounted, the difference being the so-called interference.
In spite of careful manufacturing and assembly of the bearings, differences and questions regarding the recommended installation heights and tolerances can result. Possible reasons for this are as follows:

Plain bearing cross section with measuring planes

The position of measurement planes

Bore is not properly chamfered - the bearing scrapes off on the outside.

A centering pin is used to enlarge the bearings' inside when it is pressed in.

The bore does not correspond to the H7 tolerance.

The housing is made of a soft material that gets enlarged by the bearing when pressed in.

The shaft is not H-tolerant.

The measuring doesn't take place within the measuring lines.

Pin gage measurement of iglidur® plain bearings

I only need a few plain bearings. So the price is not decisive for me.Which iglidur® bearing is the best one?

Unfortunately, there is no such thing as "the best iglidur® plain bearing". The bearing with the highest price is not always the longest lasting one in all applications. But the best iglidur® plain bearing for your application does exist.
It is important to always choose your bearing in relation to the application in which it is to be used. The more that is known about the application, the more precisely is it possible to choose the bearing that makes most sense in technical and economic terms.For this purpose, our iglidur® product finder and our iglidur® service life calculator are available online. If you do not have the opportunity or time to use these tools, simply give us your application data and we will do the rest.

Is the colour of an iglidur® bearing freely selectable?

Unfortunately no, the colour is usually determined by the respective material composition or there are often only individual dyes that are suitable for a material and at the same time do not adversely affect the tribological specifications. The wear behaviour depends on the composition of the material (the dye being a part of it) and adding a new dye often increases wear many times over. Each iglidur® material has its own particular colour although some materials look almost identical.

How is an iglidur® plain bearing installed?

iglidur® plain bearings are press-fit bearings. The inner diameter adjusts itself only after the bearing has been press-fitted in the H7 housing hole with the recommended tolerance. The press-fit dimension can be in excess of up to 2% of the inner diameter. This ensures the secure press-fitting of the bearings. Axial or radial movements in the housing are reliably avoided.
The hole in the housing should be made with the recommended tolerance (H7) for all bearings and be smooth, flat and chamfered. The bearing should be press-fitted using a flat press. The use of centring or calibrating pins can cause damage to the bearings and lead to greater clearance.

Force-fitting of an iglidur® plain bearing

What are the recommendation regarding the gluing of iglidur® plain bearings?

In standard cases, we have very good experiences with superglues (e.g. Loctite 401). Materials that are difficult to bond, such as iglidur® J, 2-component systems (e.g. Loctite 406 + Primer 770), gives significantly better results. For applications with elevated temperatures, we have good experience with epoxy resin systems (e.g. Hysol).
In addition, whatever superglue is used, it is important that the workpieces are cleaned thoroughly and are free of grease. This can be done with professional cleaning agents, e.g., but also with simple fast-acting grease removers. Roughening the contact surfaces also enhances adhesion.In general, gluing should only be used as a supplementary measure and should not completely replace the press-fit.

Why is an iglidur® polymer bearing environmentally friendly?

1.1 igus®' iglidur® N54 plastic bushings are made out of 54 percent raw, renewable materials.

In the words of Kermit the Frog, “It a’int easy being green." And while he might be just a Muppet, Kermit has a point – these days, many companies are working hard to reduce their carbon footprint on the environment. However, becoming a more environmentally friendly operation does not happen overnight. It is usually a culmination of changes that take place over time, in a number of different areas. So, as a design engineer, what small change can you make to help this cause? While it might sound insignificant, using dry-running plastic bushings can significantly decrease any negative effects on the environment.

Here are four reasons to use environmentally friendly plastic bushings:

1. Plastic bushings do not require lubrication, which keeps the environment cleaner.It is estimated that one billion gallons of industrial lubricants are consumed annually in the United States and about 40 percent of that is released into the environment. Due to continual advances in tribologically-optimized plastic bushing technology, igus® is able to supply metal bushing alternatives more in line with environmental considerations for an increasing number of applications. Unlike metal or bronze bearings that require messy lubrication, every igidur® plastic bushing uses solid lubricants embedded inside millions of tiny chambers that cannot be pressed out. This means the bushings do not require any oil or grease and so no contaminants are released into the environment.

2. Plastic bushings are extremely lightweight, which helps reduce fuel consumption and carbon dioxide output. The reduced weight leads to lower masses and subsequently lower energy consumption.

3. The high chemical resistance of plastic bushings is another positive ecological aspect. Metals often have to be coated using an environmentally unfriendly, high-energy zinc galvanizing bath to achieve this effect.

4. Less energy is required to produce a plastic bushing compared to a metal bearing. For example, the energy from 15 litres of crude oil is necessary to produce 1 litre aluminium and the energy from 11 litre crude oil is necessary to produce 1 litre of steel. In comparison, it only takes 1 litre crude oil to create 1 litre of plastic and we expect this value to fall even further based on continuing breakthroughs in the field of vegetable-oil based plastics.

The heavier a material is, the more energy it needs to stay in motion.

What influence does the iglidur® polymer bearing have on the selection of the shaft?

1. Cost factors

Range of iglidur® plastic bearings

Reducing costs is an important factor for most companies. 'The ability to use low-cost shaft materials depends on the bearings chose.

For example, ball bearings require very hard (60HRC or above) and smooth shafting. Bronze bearings are similar: the shafting must be harder than the bronze material being used. Because of these requirements, shafting choices are limited. A less expensive shafting material may not be suitable for the application.
Plastic bushings offer a few more options because they can run on many different shafts. The igus® iglidur® plain bearings are available in a wide range of materials:
Thus you can combine the lowest-priced shaft with the iglidur® bearing material which is most suitable for the application and/or the required service life. Bearing and shaft need to last only so long as the service life of the entire machine/device. - Why select an expensive shaft and/or an expensive bearing that outlast the machine?

2. Aspects of wear

Erosion damage due to a shaft being too smooth.

Aside from the cost factors, there are a number of other things to consider when designing shafting into a bearing system. Many things can affect the performance of the bearings used if they are not taken into consideration. If the shaft is too rough, wear can become a problem. Extremely rough shafting can act like a file and separate small particles of the bearing's surface during movement. When there is a large difference between static and dynamic friction, alongside adhesion between mating surfaces, stick-slip— characterized by a loud squeaking noise—can become a problem.

Another important consideration is how hard and soft particles can damage bearings and shafts. If particles get in between a bearing and its mating surface, both can suffer from increased wear. Dirt, dust and paper fibers are just some elements that can cause problems. Bearings with self-lubrication through embedded solid lubricants are more long-lasting in dirt, because there is neither fat nor oil at the bearing position. This means that dirt particles are neither drawn in nor stick to the shaft and the bearing (as can be observed for instance in a well-greased bicycle chain). - This also enables the use of less expensive shafts, even in dirty applications. There are numerous shaft materials on the market, and each of them reacts differently to the wear of a bearing. This includes among others aluminum, case hardening steel, stainless steel and chrome-plated steel. In the end the application conditions and the requirements of service life decide on the shaft to be used. When selecting a suitable iglidur® plain bearing, any standard shaft type can be basically used.

Wear tests with aluminum shafts

Hard chromed shafts, for example, are very hard, but also smooth. The wear of iglidur® plastic plain bearings is on average less in this type of shaft than in other shaft types. A stick-slip effect can occur in individual cases due to the low surface roughness. Various stainless steels are preferred for use in wet areas and in food processing, while hard-coated aluminum is suitable for applications with rather less load and a necessity for low weight. The best coefficients of friction are achieved here in connection with iglidur® J.

How is a pin-gauge measurement carried out?

1.1 Among other things, igus® ensures through a gage inspection, also called "go/no go test", that our bearings comply with the specifications and work properly after installation.

First, the bearings are pressed into a test housing. Here, take care that the bearings are mounted without damage. For that we recommend a chamfer at the insert – ideally 25-30 degrees. Moreover a press with a level punch is recommended for pressing in the bearings. This is the most efficient installation method. It is extremely important for preserving the integrity of the bearing. For example, if you use a hammer, the installation of the bearing might be uneven.

1.2 igus® recommends using an press to press-fit a plain bearing during installation.

The installation of the bearing is followed by the actual gage inspection. Specifically, a "go" signifies the pin falling through the bearing under its own weight, while a "no-go" occurs when the pin does not fall through the bearing, or "sticks". Usually the gages are graded in 0.01 mm steps, so it can be determined very accurately from which size each gage hangs.

A gage test is the quality check with the highest possible accuracy, because the pin acts like a shaft in a real application and reproduces the narrowest diameter of the bearing. It is usually this aspect that is decisive for the application. Gage inspections are particularly suitable for plastic bearings, as the irrelevant "unevenness" of the bearing due to injection molding is not taken into account. An ideal gliding surface develops later in operation, during the run-in period, when the unevenness of the bearing and the shaft smoothen.
While there are other tests that can be used to quality-check a bearing, inaccuracies can arise when applying these methods to plastic bearings. In particular, the use of a caliper should be avoided. Calipers, depending on the level of accuracy, are generally acceptable for only hurried quality checks. The measurement can become faulty depending on the pressure applied by the gage on the measuring point. For this reason, a gage test is much more reliable.

Depending on accessibility, the described test can also be directly carried out on the serial component (and not in a specifically made test housing).

What makes a self-lubricating polymer plain bearing so special?

A homogenously structured plain bearing with predictable properties made of a high-performance plastic.

Some engineers hesitate to use plastic bearings in their designs. Maybe they have trusted metal and bronze bearings for years or they simply don't think plastics can handle the tough applications or environments. Plastic bearings, however, can endure extreme temperatures, heavy loads and high speeds. However, it's important to understand both the advantages and disadvantages of the options available. Self-lubricating polymer bearings contain solid lubricants which are embedded in minute particles in the homogenous material. In operation these solid lubricants reduce the coefficient of friction. They cannot be washed off like fat or oil and due to the homogenous structure they are distributed over the entire wall thickness of the bearing. Unlike in a layered structure the entire wall thickness of the bearing is available as a wear zone with almost identical glide properties.

Most iglidur® materials moreover contain strengthening materials which increase compressive strengths. This helps to withstand high forces and edge loads.
Due to this structure iglidur® plain bearings can be used in a wide range of shaft types - depending on the load even on the so-called soft shafts. A cost-optimized combination can thus always be found.
iglidur® bearings made of high-performance plastics should not be compared to bearings made of any standard plastic. You can precisely calculate the service life of iglidur® plastic bearings based on the specific application parameters. igus® offers you an expert system – a special database into which loads, rotary speeds, temperatures as well as further application parameters are entered. Based on the test data, the system then determines a suitable plastic bearing and its estimated service life.

Composite bearings consist of different layers. The soft gliding layer can be easily damaged by foreign particles or improper handling.

iglidur® plastic bushings constitute the step from a simple plastic bushing to a tested, compared and available machine component. The essential advantages combined:

1. No inconvenient lubricants: self-lubricating bearings contain solid lubricants. They lower the coefficients of friction and are insensitive to dirt, dust and other pollutants.

2. Freedom from maintenance: Plastic bearings can replace bronze, metal coated and injection molded bearings in almost any application area. Their resistance to dirt, dust and chemicals make plastic bearings a 'fit-and-forget' solution.

3. Cost savings: Plastic bushings can reduce costs up to 25%. They feature high wear resistance, a low coefficient of friction and can replace more costly alternatives in a variety of applications.

4. Consistently low coefficient of friction and wear: Due to their structure, plastic bearings guarantee a consistently low coefficient of friction and wear throughout their lifetime. Compared to metallic composite bearings, whose gliding layer can be damaged for instance by dirt, plastic bearings often last longer.

5. Absolute corrosion resistance and high chemical resistance: Plastic bearings cannot rust and are resistant to many ambient media.

What is the technical core competence of igus® concerning polymer bearings?

Every year the igus® engineers develop more than 100 new material compounds

In the course of years the igus® material developers have developed hundreds of material compounds, out of which almost 40 have been entered in the polymer plain bearing catalog. In principle, the setup is mostly the same:

1. Basic polymers which predetermine the basic tribological, mechanical, thermic and chemical properties of the bearing

2. Fibers and filling materials which provide the bearings with a high mechanical load capacity

3. Solid lubricants that significantly optimize wear and friction

igus® is continually developing new polymer blends for every application scenario and conducts more than 10,000 tests in its laboratory every year. Unlike most other bearings manufacturers, igus® focuses exclusively on high-performance plastics and therefore is able to economically process them into plain bearings through injection molding. These polymer plain bearings are used in a wide range of industries, among others: Agriculture, medicine, automotive industry, packaging, aviation, sports equipment, mechanical engineering, etc. In addition, igus® compiles its test results into a comprehensive database. After each polymer blend is tested, the results are added into the data pool for a unique lifetime calculation program: The Expert System, which allows you to enter your application’s maximum loads, speeds, temperatures, and shaft and housing materials in order to calculate the best plastic bearing and its expected lifetime.

Which factors influence the wear of a plain bearing?

1: Wear test during oscillating movement of an iglidur® plastic plain bearing from igus®.

Influencing factors:

Selection of the shaft: Different shaft materials are recommended for different plain bearings. Each shaft-bearing combination has different wear results.

Load: increasing radial loads or surface pressure also raises the wear of the plain bearings. Some plain bearings are designed for low load, others for high load.

Speed and type of movement: With increasing speed, the wear also increases. In addition, the movement type (oscillating, rotating or linear) has a decisive influence on the wear rate.

Temperature: within certain limits, the temperature hardly has any effect on the bearing wear, but it can also accelerate the wear exponentially. Plastic bearings are suitable for a wide temperature range, depending on the material selection. When the respective maximum application temperature exceeds, however, the wear can increase significantly. For most iglidur® materials, the wear rate increases with increasing temperatures. However, there are also exceptions that reach their minimum wear only at elevated temperatures.

Dirty environment: Dirt and dust can accumulate between shaft and bearing. That causes wear. Self-lubricating plastic bushings offer an advantage here: they do not contain oil, and hence dirt and dust cannot adhere to the shaft and damage the bearing.

Contact with chemicals: Plastic plain bearings are completely corrosion-free and resistant to a variety of chemicals, but certain chemicals can even alter the structural properties of a plain bearing, reducing the hardness of the bearing and increasing wear.

2: Wear tests with different shaft types.

Valid for all these points is: The closer I know my application and the mentioned parameters, the more specific an iglidur® material selection and a service life calculation can be. Choosing the right material is crucial for the service life.

How does bearing wear affect the bearing clearance?

Bearing wear means the erosion of the sliding surface material, i.e. usually in the bearing's inner diameter.

The clearance between bearing and shaft results arithmetically from the tolerances of bearing and shaft.

The real starting clearance at commissioning is the difference between the measured actual inner diameter of the bearing and the measured actual outer diameter of the shaft. A wear on the inner diameter of the bearing leads to an increase in diameter and thus to an enlargement of the clearance.
Since iglidur® plain bearings have no layered structure and thus the entire wall thickness acts as a wear zone, there is no wear limit specified for the bearing. The wear limit is instead determined by the maximum clearance allowed in an application. This can be very different depending on the application and user request. Precision control valves allow only a few hundredths of wear (and thus clearance enlargement). In agricultural applications with shaft diameters larger than 50mm, a clearance of significantly more than one millimetre is often not critical.

When do you use a xiros® polymer ball bearing instead of an iglidur® polymer plain bearing?

In general, it can be said that xiros® polymer ball bearings are preferable to iglidur® plain bearings where rotating movements with velocities above 1.5 metres/second can occur continuously with low loads. The significantly lower coefficient of friction of the polymer ball bearings compared to plain bearings ensures less heat generation and lower wear.

Decisive is above all the inner diameter of the ball bearing. The smaller the inner diameter, the fewer revolutions the bearing has to make per minute, which in turn has a positive effect on heat generation and dissipation. As the diameter of the ball bearing increases, the maximum load capacity increases while the maximum possible speed decreases.For higher load capacity applications, our double row polymer ball bearings are ideal. For applications involving dirt and abrasive materials, we offer xiros® ball bearings with a double shield."

What is meant by the stick-slip effect?

The stick-slip effect or adhesive sliding effect is the backsliding of solid bodies moving against each other. This phenomenon occurs when a body is moved whose static friction is significantly greater than the sliding friction.

Imagine a heavy carton that you want to push over a smooth floor. The carton is heavy, which is why we have to use great force to overcome the static friction - that is, to move the resistance of the carton. The carton slides. Due to the smooth surface and the resulting low sliding friction, the carton is rapidly faster. However, the carton's rapid sliding motion allows us to transfer less force to the carton. Finally, the force acting on the carton is no longer sufficient to overcome its static friction. The carton comes to a standstill, which requires us to apply much force again to overcome it and the process repeats itself. Adherence - releasing - sliding - braking - adherence - releasing ... in reality, this effect is much faster and manifests itself in a stutter. .

This phenomenon can be seen in a wide variety of areas. Wipers stutter over the windscreen of a car. When writing on the blackboard, chalk squeaks if you keep it at the wrong angle. Door hinges squeak. And stringed instruments such as the violin or the cello would not work, because their sounds arise by vibrations caused by stick-slip effect and vibration between the strings and the chords of the bows. .

For tribologically optimised materials, however, this effect is undesirable. The vibrations caused are transmitted to the overall structure and cause noises, which are often perceived as annoying squeaking or creaking. The desired sliding movement becomes an irregular stuttering and increases the wear of the bearings. These effects can be counteracted by minimising the difference between sliding and static friction, by using vibration dampening materials, by improving the rigidity of the overall structure (see pre-loaded bearings) or by separating the involved friction partners (for example by lubrication).

1. Force > static friction
The force (vector 1) overcomes the static friction (vector 2). The cardboard box starts to move.

2. Force = static friction
Static friction is transformed into dynamic friction (vector 2) and the cardboard box glides rapidly.

3. Force < dynamic friction
The force (vector 1) is insufficient to overcome the dynamic friction (vector 2).

4. Force < static friction
Dynamic friction is transformed into static friction. The force is insufficient and the cardboard box come to rest.

Are iglidur® plain bearings compliant with RoHS, and what is RoHS anyway?

The key word "RoHS" is based on EU guideline 2002/95/EU ("RoHS 1") which was replaced on 3 January 2013 by EU guideline 2011/65/EU ("RoHS 2").
The guideline regulates the restriction of undesirable ingredients in electrical and electronic equipment placed on the EU market. RoHS stands for "Restriction of (the use of certain) Hazardous Substances".
Since many materials and products cannot be technically completely eliminated, concrete limits have been defined.Affected are the substances commonly used in electronics such as lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBB) and diphenyl ethers (PBDE). Application examples include the use of lead during soldering or as part of composite metal bearings and the use of PBB as a flame retardant. These substances also occur in numerous metallic alloys.As you can see by taking a look at the substances and also from these application examples, these substances do not play any role in thermoplastic compounds such as our iglidur® materials. Thus, the ingredients of our iglidur® materials meet the requirements of guideline 2011/65/EU (RoHS 2). We are happy to send corresponding explicit confirmations upon request.

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Are iglidur® plain bearings resistant to chemicals?

Contact with chemicals is often a particularly difficult challenge for plain bearings. For instance, the food industry uses disinfectants or cleaners, or the bearings come into contact with coolant. iglidur® materials are tested for resistance to a large number of chemicals. So that they can be used in applications in which they come into contact with disinfectants, cleaners or other chemicals. iglidur® materials from the "H range" (iglidur® H1, H370, etc.) and iglidur® X are considered particularly resistant to chemicals.

What are plain bearings?

In mechanical engineering, the term plain bearing is understood to mean components that decouple surfaces that move relative to one another. In this way, these surfaces are protected against wear-related damage and the coefficient of friction and thus the energy required for movement, as well as the generation of heat, are reduced.

When do you use plain bearings?

Plain bearings are used wherever the friction and wear of surfaces that are exposed to movement is to be reduced. The fields of application range from the bearing of bridges, which expand under the action of temperature and the movable elements of an office chair, to pinhead-sized plain bearings in electric toothbrushes.
In general, plain bearings are particularly suitable for applications in which the combination of load respectively surface pressure and movement intensity is not too high. We speak of the so-called PV value, which is the product of surface pressure in N/mm² and the velocity in m/s. The maximum permissible PV value is specified by the manufacturer for most plain bearings. If this is exceeded by the application conditions, the plain bearing is unsuitable for them. In this case, either additional cooling or the use of a ball bearing must be considered. However, with sufficient cooling or reduction of friction through lubrication, plain bearings can also be used in case of very high PV values.

What does a plain bearing do?

Plain bearings decouple moving parts from one another in order to protect their surfaces from wear and reduce friction between them. As a result of the lower coefficient of friction, the force required for the movement and thus the energy can be reduced.

Which is better, plain or ball bearing?

Plain and ball bearings are each based on different operating principles and therefore have different specifications. These specifications make their suitability for different applications better or worse. Plain bearings are one-piece components that consist of one or more materials and are intended to reduce friction either through integrated solid lubricants or additional lubrication. They are particularly suitable for applications in which a cost-effective and space-saving solution is required, and where the combination of load and speed is not too high. Ball bearings consist of rings between which several balls or rollers are mounted. These rotate around the inner ring of the ball bearing and thus enable the adjacent components to move relative to each other. The advantage of ball bearings is precision, as they can be designed virtually clearance-free, as well as their particularly low rolling resistance. Similar to the plain bearings' coefficient of sliding friction, this contributes to very smooth applications. However, plain bearings also require significantly more installation space for this. They are heavier, often more expensive and must be specially protected against dirt ingress and loss of lubricant.

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