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xiros® Plastic ball bearing design, applications, development and testing

The product range of xiros polymer ball bearings includes a variety of different product options. One common feature for all is that they do not need any additional lubrication. This results in considerable advantages, since in every application it avoids lubricants that pollute the surroundings, or are washed out or corroded by external influences.
In addition there are, depending on the design, other advantages:



Free of metal (by the use of glass and plastic balls)


Chemical resistant


Electrically insulating

FDA compliant

Predictable service life

The last-mentioned predictability of xiros polymer ball bearings is one of the main benefits. Based on the results of many wear tests, the user can reliably calculate the lifetime of the xiros polymer ball bearings and design its application.


The product line of the single-row grooved ball bearings consists of polymer ball bearings based on DIN 625. The self-lubricating and maintenance-free ball bearings comprise four components

A = outer ring

B = inner ring

C = cage

D = balls

xiros structure

Outer- and Inner ring

The suitability of a xiros polymer ball bearing is determined largely by the materials of the two races. These races are made of igus® tribopolymers to maximize service life and minimize coefficients of friction. There are three materials to choose from. They differ in the permissible temperature, chemical resistance and cost. Accurate information can be had from thematerial data

The cage

The material of the ball bearing cage must also match the application. These materials are very different in terms of chemical resistance and temperature. In the scope of delivery of xiros polymer ball bearings, the cages are already perfectly adapted to the materials of the outer and inner rings.

The balls

The materials of the balls differ the most. Glass or plastics are used besides steel. This alone gives a big difference in the masses, which in turn have an impact on smooth running, weight and media resistance. Steel balls (stainless steel) are inexpensive, resistant to chemicals, but have the maximum weight. Glass balls should be selected when it needs to be free of metal. They are also very resistant to chemicals and have an average weight. Polymer balls have significant advantages in weight, mass and quiet running performance. Depending on the plastic, polymer balls have excellent chemical resistance.

Pillow block and flange bearings

The use of xiros polymer ball bearings together with igubal® pillow block and flange bearings gives you greater flexibility while installing the ball bearings The ready-to-install bearing housing makes it easy for users to use these maintenance-free elements. Both flange and pillow block bearings are offered as rigid or pivoting version. The difference here lies in the compensation of misalignment, which is a typical function of the igubal® bearing unit. In the pivoting version, the xiros polymer ball bearings with spherical outer contour are assembled in an appropriate housing. If necessary, the inner bearing can be pivoted in all directions. Possible misalignment of two bearing points lying together can thus be compensated. The rigid version dispenses with this pivoting possibility in favor of lower cost.

Application areas

In contrast to metallic ball bearings, xiros polymer ball bearings manage absolutely without lubrication. For this reason they are suited for a multitude of applications that depend not on extreme rotary speeds or loads, but just on lubricant-free application in contrast to permanently lubricated metallic ball bearings. These areas are for example food, packaging and medical industries, packaging and textile industries, or the chemical industry and cleanroom applications as well as electronics and office technology. Their applications are where freedom from metals and non-magnetic property are required. Here the applications are mainly in medical and measuring technology.

Development and testing

The materials of the races could be further improved through numerous tests. Thereby polymer ball bearings that allow higher speeds, more loads and longer life could be developed. But the development continues: We think that the topic of the polymer ball bearing hasn't been exhausted for a long time yet. With our long years of experience in tribologically optimized plastics and our testing potentials, we believe polymer ball bearings can advance a lot further. Contact us and tell us about your applications where you think you can draw benefits from the polymer ball bearings.

The xiros® plastic ball bearings are tested for service life and wear at the igus® test laboratory. In addition to the actual material comparison tests, these trials also spell out the impacts of external influences such as temperature, humidity or dust.

xiros testing N = 500 rpm, F = 20 N, T = +73 °F
Y = Wear [μm/km]
A = xiros B180
B = alt. Polymer ball bearings I
B = alt. Polymer ball bearings II
D = xiros A500
Figure 01: Wear test at the igus® laboratory
xiros testing N = 500 rpm, F = 20 N, T = +73 °F
Y = Wear [μm/km]
A = xiros B180
B = alt. Polymer ball bearings I
B = alt. Polymer ball bearings II
D = xiros A500
Figure 02: Wear test at the igus® laboratory
xiros testing n = 1.000 rpm, F = 50 N
Y = life time [h]
X = temperature [°F]
A = +73 °F
B = +176 °F
C= +302 °F
Fig. 03: Service life of xiros A500 polymer ball bearings in different ambient temperatures, dry
xiros polymer ball bearings in the igus® laboratory Picture 01: Test stand for xiros® plastic ball bearings in the igus® laboratory
xiros polymer ball bearings in the igus® laboratory Picture 02: Test stand for xiros® plastic ball bearings in the igus® laboratory

The material combinations for bearing rings, balls and cages are tested in the igus® test laboratory by a variety of load and speed trials. Thus, the application-specific selection of the suitable bearing and a service life assessment is possible.


In the scope of the development of the xiros polymer ball bearings, continuous tests are carried out. An extensive amount of wear data are available from the numerous test results, whereby the service life of the bearings can be predicted. Thus, a concrete statement on the service life can be made both in the framework of a new development and in an existing structure.
As soon as the data is entered, the lifetime is calculated and displayed. Here it is important to know that the statement on the service life is based on real experiments conducted and evaluated under controlled conditions and therefore absolutely reliable.