Abstract:
Electrolytic In-Process Dressing (ELID) has attracted a lot of attention in recent years
as it is a promising method of grinding a wide range of materials, including ones that
are difficult to machine, to high quality finishes. The EC funded project Nanogrind
undertook the construction of a high precision grinding machine which will
incorporate an ELID system, applying the technique on a spherical wheel for the
production of components with intricate geometries (e.g. freeforms, aspherics).
In this project, the main objective was to understand the basic features of ELID, such
as the electrochemical properties of the oxide layer and its effect on the final finish of
the produced components (glass, a hard and brittle material was the main focus).
Acoustic emission studies, a promising in-process monitoring tool, verified the
effectiveness of ELID grinding when the contact area between the wheel and
workpiece is increased. Compared to conventional resin bond wheel grinding, ELID
ground components were of higher quality with less damage introduced in them.
ELID current monitoring also gave excellent results when it was correlated to surface
finish achieved across the surface of the testpieces ground.
Electrochemical Impedance Spectroscopy was an innovative technique that was
applied in order to acquire basic information about the metal bond wheel, such as the
charge transfer resistance. Its correlation to the oxide layer thickness gave an
indication of the way corrosion rates change with the presence or not of an oxide film
on the wheel surface.
Finally, sub-surface damage introduced into glass components was evaluated and was
compared to the depths of damage predicted by theoretical models, giving further
insight into the way the overall processing time of a component should be optimised
in order to acquire high quality, damage-free finished components in a time efficient,
cost effective way.