4.2.1 Hard machining
Final machining (hard machining)
is carried out on fully sintered items that have been brought
as close as possible to the final dimensions through forming,
or through green or white machining. The closest possible
tolerances can be achieved through a final machining procedure
involving material removal.
Tight requirements for dimensional precision and the wide
variety of geometries and surface qualities require the use
of modern machine tools for processing ceramic components.
Due to the high hardness of ceramic materials, diamond tools
(bonded or pastes) are used here almost exclusively.
Figures 65 and 66: Hard machining components:
grinding and lapping
Table 7: Possible finishing processes.
Grinding is of central
importance. A large number of factors affect the grinding
process and the result of the grinding. For this reason, the
appropriate grinding wheel for any particular workpiece is
selected with great care for its grain type and size, the
bonding, and the hardness of the wheel. Extremely flat surfaces
such as for slip rings and sealing surfaces must be lapped
and then polished after grinding.