For some years, the demand has been for ever more accurate and precise engineering components manufactured on machine tools. Most conventional turning and machining centres are working at the limit of their process capabilities, typically Cpk 1.66. This has meant that in order to produce components of not only high dimensional accuracy but coupled to ultra-fine surface finishes, then a somewhat different approach has to be used in not only machine tool design, but in the method chosen to manufacture such parts. Therefore these CNC machines must have not only their structural parts redesigned and manufactured from thermally stable and low vibration materials, their bearing design and relative positioning needs to be considered along with techniques to ensure linear axis positioning control and geometry orientation of slideways. Often this entails "active" software correction - once having "error-mapped" the machines volumetric envelope. This and other factors, such as thermal monitoring of bearings and coolant, together with refrigerated spindle drives are essential. In many cases not only must be the ambient temperature be strictly controlled but also that of the working environment.
In order to achieve superior machined finishes and dimensional control on ultra-precise components, conventional tool grinding techniques for the generation and forming of cutting tools is not applicable, as ground tools can superimpose irregularities on the part's surface, as well as those reproduced by the influence and passage of the tool across the surface leaving cusps - which are a function of the feedrate & tool nose geometry.
This paper will discuss these factors when attempting to manufacture components of extreme dimensional accuracy and surface finish, and establish techniques to ensure that such important factors are not overlooked when ultra-precision is the goal.