Roundness (object)

As a non-circular refers to the art geometric shapes and cross sections that differ from the circle or a circular motion periodically. The deviations can be caused intentionally ( eg for a non-circular planetary gear ), but can also be caused by wear and friction set.

As a noun, the term is used for the non-circular closed curve, which - as can be seen in the sketch next to - all of the same diameter, the radii of curvature, however, are greater than half the diameter. A non-circularity can be used like a wheel, but rises and falls its axis of rotation during rolling periodically. It is used in specific areas of engineering, but also for some toys, such as the millipede to follow suit.

Planned deviations from roundness have, inter alia, some special planetary gear when a regular order of a movement, a periodic share is to be imposed. Thus, in a non-circular tooth gear, the ring gear be implemented as a run-out, run to the inside three smaller non-circular gears. Also metallic small parts such as piston rings or washers are often made out of round defined. Thus, the piston rings of gasoline engines are only pressed when installed in the circular form.

Unwanted runouts occur for example due to wear of parts of an internal combustion engine - which manifests itself as well as faults in the ignition and uneven running noticeable - or at the wheels of rail vehicles. If the deviations from the circular shape such wheels are correspondingly large, so they do not just rumble through noticeable, but may increase rapidly by the induced vibrations.

There are separate cylindrical grinding machines, which are also suitable for grinding non-circular workpieces.