iglidur® Frequently Asked Questions

How is a iglidur® plain bearing fixed in a bearing holder?

The iglidur® plain bearings are designed so that they can be pressed into an H7-tolerated mount with the nominal dimension of the bearing outer diameter and are then fixed in place by the press fit. This is achieved by the so-called press-fit interference, i.e. the outer diameter of the bearing is approx. 0.1-0.25 mm larger than the mounting when not press-fitted, depending on the nominal dimension. The inner diameter also only reaches its final dimensions and tolerances 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 range of customer requirements. The development of a good plain bearing material often has something to do with squaring the circle. If you optimise in a certain direction, you usually do so at the expense of another specification. - With the five standard materials iglidur® G, J, X, W300 and M250, the majority of applications can be technically covered.
However, when it comes to very special or demanding applications, the exhaustion of the last technical reserves or the final price-performance optimisation for high volume, the other iglidur® materials are becoming increasingly important. In recent years, new iglidur® materials have also pushed the application limits of dry-running plain bearings even further.

How do I find the right iglidur® material?

With just a few application data, a preselection is already possible via the iglidur® product finder or a service life calculation with the iglidur® service life calculator. The large variety of materials is quickly reduced and the suitable materials remain.

**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 are among the most wear-resistant all-round bearings in the iglidur® programme. If the service life is comparable and sufficient in both cases, the marginal parameters of the application should determine the choice: iglidur® J is predestined for wet areas due to its low moisture absorption and good media resistance, iglidur® W300 offers more temperature reserves.

Why can iglidur® bearings manage without lubrication?

Due to the special structure of the iglidur® materials, which are generally composed of a thermoplastic matrix, fibre reinforcements and so-called solid lubricants. The already good wear and friction properties of the matrix or base material are further optimised by the solid lubricants. Sufficient solid lubricant particles are always present on the bearing surface during operation. Additional external lubrication with grease or oil is generally not necessary or not advisable. Video on the question

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

Unfortunately, there is no such thing as "the best iglidur® bearing". Even the most expensive bearing is not the most durable in every application. But there is the best iglidur® bearing for your application.
It is important to always make the bearing selection depending on the application. The more you know about the application, the more precisely you can select the most technically and economically sensible bearing.
Our iglidur® product finder and our iglidur® service life calculator are available online for this purpose. If you don't have the opportunity or leisure to familiarise yourself with these tools, simply give us your application data and we will do the rest.

Is the colour of a iglidur® plain 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 negatively affect the tribological specification. Above all, the wear behaviour depends on the material composition (which also includes the colourant) and a new colour additive often increases the wear many times over. This means that every iglidur® material has a specific colour, although some materials look almost identical.

What recommendations are there for bonding iglidur® plain bearings?

In standard cases, we have had very good experiences with instant adhesives (e.g. Loctite 401). With materials that are difficult to bond, such as iglidur® J, significantly better results are achieved with 2-component systems (e.g. Loctite 406 + Primer 770). We have had good experiences with epoxy resin systems (e.g. Hysol) for applications with increased temperatures.
Furthermore, it is important for every bonded joint that the workpieces are thoroughly cleaned and free of grease. This can be done with professional cleaners, for example, but also with simple quick degreasers. Roughening the contact surfaces also supports the bonding effect.
In general, bonding can only have a supporting effect and cannot completely replace the press fit.

Why is an iglidur® polymer bearing environmentally friendly?

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

Hard chrome-plated shafts, for example, are very hard but also smooth. The wear of iglidur®plastic plain bearings is usually lower on average with this type of shaft than with other shaft types. However, due to the low surface roughness, a stick-slip effect can occur in some cases. The various stainless steels are preferably used in wet areas and in food processing, while hard-coated aluminium is suitable for applications with a rather low load and the need to reduce weight. The best coefficient of friction is also achieved here in conjunction with iglidur® J.

How does a plug gauge measurement work?

1.1 igus® uses a plug gauge test, also known as a "go/no-go test", to ensure that our bearings meet the specifications and function properly after installation.

First, the bearings are pressed into a test fixture. It is important to ensure that the bearings are installed without damage. A bevelled edge is recommended for this - ideally 25-30 degrees. It is also advisable to use a press with a flat press to press in the bearing. This is the most efficient installation method. It also ensures the integrity of the bearing. If you use a hammer, for example, the bearing can tilt during installation.

1.2 igus® recommends using a press to install a plain bearing.

After the bearing has been installed, the actual plug gauge test is carried out. A "Go" means that the bolt falls through the bearing under its own weight, while a "No-Go" means that the bolt does not fall through the bearing or remains stuck. As a rule, the plug gauges are graduated to 0.01 mm, so that it is possible to determine very precisely from which dimension the respective plug gauge hangs.

A plug gauge test is the quality check with the greatest possible accuracy because the bolt behaves like a shaft in a real application and reflects the narrowest cross section of the bearing. It is precisely this aspect that is usually decisive for the application. Plug gauge tests are particularly suitable for plastic bearings, as the irrelevant "unevenness" of the bearing caused by injection moulding is not taken into account. Later in operation, during the running-in phase, when the unevenness of the bearing and the shaft is smoothed out, an ideal sliding surface is created.
The quality control of a bearing can also be carried out using other tests; however, inaccuracies can occur when these methods are applied to plastic bearings. In particular, the use of gauges should be avoided. Gauges should generally only be used for cursory quality checks, depending on the degree of accuracy. Depending on the pressure exerted by the gauge on the measuring point, the measurement may be falsified. A plug gauge test is therefore much more reliable.

Depending on accessibility, the described test can also be carried out directly on the series component (i.e. not in a specially manufactured test fixture).

iglidur®® plastic bearings represent the step from a simple plastic bushing to a tested and available machine component with calculable specifications. The main advantages summarised once again:

1. no troublesome lubricants: self-lubricating bearings contain solid lubricants. They reduce the coefficient of friction and are insensitive to dirt, dust and other contaminants.

2. maintenance-free: plastic bearings can replace bronze, metal-coated and injection moulding bearings in almost any application. Their resistance to dirt, dust and chemicals makes plastic bearings a "fit and forget" solution.

3. cost savings: Plastic bushings can reduce costs by up to 25 %. They are characterised by high wear resistance and a low coefficient of friction and can replace more expensive alternatives in a wide range of applications.

4. consistently low coefficient of friction and wear: Due to their design, plastic bearings guarantee a consistently low coefficient of friction and wear over the entire service life. Compared to metallic composite bearings, whose gliding layer can be damaged by dirt, for example, plastic bearings often last longer.

5. Absolutely corrosion-free and highly resistant to chemicals: plastic bearings cannot rust and are resistant to many environmental media.

igus® is constantly developing new polymer blends for every application and carries out almost 10,000 tests in its laboratory every year. Unlike most bearing manufacturers, igus® focuses exclusively on high-performance plastics and is able to process these cost-effectively into plain bearings using injection moulding: Agriculture, medical, automotive, packaging, aerospace, sports equipment, mechanical engineering and many more. In addition, igus® archives the test results in an extensive database. After testing a new polymer compound, the results are added to the data pool where they are available for a unique service life calculation programme: the expert system - where you can enter the maximum load, speed and temperatures of your application as well as shaft and housing materials to determine the best plastic bearing and its expected service life.

What factors influence the wear of a plain bearing?

1: Wear test with oscillating movement of a iglidur®plastic plain bearing from igus®.

Influencing factors:

Shaft selection: Different shaft materials are recommended for different plain bearings. Each shaft-bearing combination has different wear results.

load: As radial loads or surface pressures increase, the wear on the plain bearings also increases. Some plain bearings are designed for low loads, others for high loads.

Speed and type of movement: As the speed increases, so does the wear. The type of movement (oscillating, rotating or linear) also has a significant influence on the wear rate.

Temperature: Within certain limits, temperature has little effect on the wear of a bearing, but it can also accelerate wear exponentially. Plastic bearings are suitable for a wide temperature range, depending on the material selected. However, wear can increase significantly if the maximum application temperature is exceeded. With most iglidur® materials, the wear rate increases with rising temperatures. However, there are also exceptions that only reach their minimum wear at higher temperatures.

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

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

2: Wear tests with different shaft types.

The following applies to all these points: the more precisely I know my application and the parameters addressed, the more specifically a iglidur® material selection and a service life extrapolation can be made. Selecting the right material is crucial for service life.

How does bearing wear affect the bearing clearance?

Bearing wear means material removal on the sliding surface, i.e. usually on the inner diameter of the bearing.

The clearance between the bearing and shaft is calculated from the tolerances of the bearing and shaft.

The actual starting clearance during commissioning is the difference between the measured actual inner diameter of the bearing and the measured actual outer diameter of the shaft. Wear on the bearing inner diameter leads to an increase in diameter and thus to an increase in clearance.
As iglidur® plain bearings do not have a layered structure and therefore the entire wall thickness is available as a wear zone, there is no wear limit specified by the bearing. Instead, the wear limit is determined by the maximum clearance permitted in an application. This can vary greatly depending on the application and user requirements. Precision control valves, for example, only allow a few hundredths of wear (and therefore an increase in play). In agricultural applications with shaft diameters greater than 50 mm, a clearance of significantly more than one millimetre is often uncritical.

When is a xiros® polymer ball bearing used instead of an iglidur® polymer plain bearing?

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

The inner diameter of the ball bearing is particularly important. The smaller the inner diameter, the fewer revolutions the bearing has to perform per minute, which in turn has a positive effect on heat generation and dissipation. If the diameter of the ball bearing increases, the maximum load capacity increases, while the maximum possible speed decreases.

Our double-row polymer ball bearings are suitable for applications with higher load capacities. For applications involving dirt and abrasive materials, we offer xiros® ball bearings with a cover disc."

What is the stick-slip effect?

The stick-slip effect refers to the jerky sliding 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 cardboard box that you want to push across a smooth floor. The box is heavy, which is why we have to exert a lot of force to overcome the static friction - i.e. the resistance of the box to move. The cardboard slides. Due to the smooth surface and the resulting low sliding friction, the carton quickly speeds up. However, the rapid sliding movement of the cardboard means that we can transfer less force to the cardboard. Eventually, the force acting on the carton is no longer sufficient to overcome its static friction. The carton comes to a standstill, which means we have to apply a lot of force again to overcome it and the process repeats itself. Sticking - releasing - sliding - braking - sticking - releasing... in reality, this effect happens much faster and manifests itself in a stutter. .

This phenomenon occurs in a wide variety of areas. Windscreen wipers stutter across the windscreen of a car. Chalk squeaks when you write on a sheet of paper if you hold it at the wrong angle. Door hinges squeak. And stringed instruments such as the violin or cello would not work, because their sounds are caused by vibrations and oscillations between the strings and the tendons of the sag.

With tribologically optimised materials, however, this effect is undesirable. The vibrations caused are transferred to the overall construction and cause noises that are often perceived as annoying squeaking or creaking. The desired sliding movement becomes an irregular stuttering and increases wear on the bearing. These effects can be counteracted by minimising the difference between sliding and static friction, using vibration-damping materials, improving the rigidity of the overall structure (see preloaded bearing) or separating the friction partners involved (e.g. by lubrication)

1. force > Static friction
The force (arrow 1) overcomes the static friction (arrow 2). The carton starts to move.

2nd force = static friction
The static friction becomes sliding friction (arrow 2) and the carton slides quickly.

3rd force < Sliding friction
The force (arrow 1) is not sufficient to overcome the sliding friction (arrow 2).

4. force < static friction
The sliding friction becomes static friction. The force is not sufficient, the box stops.

Are iglidur® plain bearings resistant to chemicals?

Contact with chemicals is often a particular challenge for plain bearings. For example, disinfectants or cleaning agents are used in the food industry or the bearings come into contact with coolants. iglidur® Materials are tested for their resistance in conjunction with a variety of chemicals. They can therefore be used in contact with chemicals, disinfectants or cleaning agents. The iglidur® materials of the "H family" (iglidur® H1, H370 etc.) and iglidur® X are considered to be particularly resistant to chemicals.

What is a plain bearing?

In mechanical engineering, the term plain bearing refers to components that decouple surfaces that move relative to each other. This protects these surfaces from wear-related damage and reduces the coefficient of friction and thus the energy required for movement, as well as heat generation.

When are plain bearings used?

Plain bearings are used wherever friction and wear on surfaces that are subject to movement need to be reduced. The fields of application range from the mounting of bridges that expand under the influence of temperature, to the moving elements of an office chair, to the pinhead-sized plain bearing in electric toothbrushes. 
In general, plain bearings are particularly suitable for applications in which the combination of load or surface pressure and intensity of movement is not too high. This is referred to as the pv value, which is the product of surface pressure in N/mm² and speed in m/s. The maximum permissible pv value is specified by the manufacturer for most plain bearings. If this is exceeded due to the application conditions, the plain bearing is unsuitable for these conditions. 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 with very high PV values.

What does a plain bearing do?

Plain bearings decouple moving parts from each other to protect their surfaces from wear and to reduce the friction between them. Due to the lower coefficient of friction, the force required for the movement and therefore the energy can be reduced.

Which is better plain or ball bearing?

Plain bearings and ball bearings are each based on different functional principles and therefore have different specifications. These specifications make them more or less suitable for different applications. Plain bearings are one-piece components that consist of one or more materials and are designed to reduce friction either through integrated solid lubricants or additionally applied lubrication. They are particularly suitable for applications where 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 relative movement of the adjacent components. The advantage of ball bearings is their precision, as they can be designed to be almost clearance-free, as well as their particularly low rolling resistance. Similar to the sliding friction coefficient of plain bearings, this helps to make applications particularly smooth-running. However, plain bearings also require significantly more installation space. They are heavier, often more expensive and require special protection against dirt ingress and loss of lubricant.