Machining vibrations

In machining, vibrations, also called chatter, are the relative movements between the workpiece and the cutting tool. The vibrations result in waves on the machined surface. This affects typical machining processes, such as turning, milling and drilling, and atypical machining processes, such as grinding.

A chatter mark is an irregular surface flaw left by a wheel that is out of true (off-center) in grinding,^[1] or regular marks left when turning a long piece on a lathe, due to machining vibrations.

As early as 1907, Frederick W. Taylor described machining vibrations as the most obscure and delicate of all the problems facing the machinist, an observation still true today, as shown in many publications on machining.

The explanation of the machine tool regenerative chatter was made by Tobias. S. A. and W. Fishwick in 1958,^[2] by modeling the feedback loop between the metal cutting process and the machine tool structure, and came with the stability lobes diagram. The structure stiffness, damping ratio and the machining process damping factor, are the main parameters that defines the limit where the machining process vibration is prone to enlarge with time.

Mathematical models make it possible to simulate machining vibration quite accurately, but in practice it is always difficult to avoid vibrations.