Machine Elements / Tribology


Tribological systems are technical structures whose function is associated with contact processes between interacting surfaces in relative motion. These contact processes are generally summarized as friction and wear behavior, and are dependent on numerous factors, e. g. material, surface topography, environmental conditions and load collectives. Friction and wear are, therefore, resulting criteria of a tribological system. Examples are to be found wherever interfaces move relative to each other, e. g. in sliding rails, gears, bearings and couplings. For a successful component design, the interaction with other system components must be considered.

Injection molding allows for the use of the multi-component technology and thus the functionally appropriate use of materials according to the local requirements. Thus, for example, a fibre-reinforced material in the inner body can be used to improve the mechanical properties, and a tribologically modified material of a sliding surface can be used in order to reduce sliding friction and wear.

Furthermore, the inner properties of a part can be influenced by the processing parameters. This is of especially great importance for micro-components. Process-structure-property interrelations are investigated to increase, for example, the wear resistance of micro-gears by using a defined variothermal tool temperature control technology.

left: 2 component gear (mechanically reinforced inner part; thin walled, friction-modified external part)
middle: 2 component bearing (thermally conductive inner part; mechanically reinforced outer part)
right: Assembly-injection-molded friction clutches (small parts by EJOT)

Thermographic analysis of running plastic gears

For a reasonable and efficient use of plastic machine elements, it is essential to understand the tribological properties of the plastics that are used. Studies on the tribological behavior of polymers are quickly and inexpensively carried out in model systems at the LKT. In such systems, a comparison of materials and material combinations is easily possible, but the transfer of the observed behavior between model and part is likely to be problematic since tribological properties are system-based properties. To determine specific design characteristics (thermal, mechanical, wear-related failure), different test benches for part testing are available. To examine and illustrate the relationships between material, surface topography, environmental conditions, load collectives and tribological properties, tribological tests can be carried out and supplemented by further analysis methods (microscopy, thermal analysis, static and dynamic tests).


Dipl.-Ing. Bernhard Gierl