Mean Time Between Failures (MTBF) became a very frequently used value describing reliability of
components, assemblies, and systems. MTBF was originallyintroduced and used mainlyin conjunction with
electronic components, and systems. The definition and application ofthe MTBFformechanical components
is not broadly available, used, or recognized. There is no clear standard which would describe how to
determine forinstancethe MTBFofagearbox. On the otherhand, more and more customers and consultants
are requesting an MTBF number from the manufacturer for mechanical devices, such as a gearbox.
Electronic components of modern drive–trains generally consist of an electronic controller and electronic
drive, motor and gearbox. The drive /controller manufacturer normally has an MTBF value, so do meanwhile
some motor manufacturers supply MTBF values for their product. In the field ofgears it is difficult to obtain an
MTBF from the manufacturer due to the lack of applicable, generally recognized definitions and standards.
The paper shall evaluate, compare and suggest ways in determining a gearbox MTBF based on the already
established, proven, design, calculation standards and test methods used in the gear design.