1 Introduction
1.1 Fundamentals
Electrochemical micromachining is a non-conventional
manufacturing process used as an alternative to conventional
mechanical machining and non-conventional manufacturing
processes for electrically conductive materials.
Electrochemical machining (ECM) is based on the process
of electrolysis. It is very popular for material volume
removal and shaping the anode using DC current by using
complex-shaped cathode electrodes. The anode
(workpiece) and the cathode (tool-electrode) are both submerged
in a constantly renewed electrolytic solution and a
voltage is applied. The resulting current passes through the
system and a chemical reaction takes place. Anodic dissolution
occurs, material is removed and the workpiece is
shaped according to the features of the cathode [1]. This
machining process uses non-toxic electrolytes such as a
sodium nitrate (NaNO3) and sodium chloride (NaCl) aqueous
solutions [2].
Recent developments in this area aim at the use of much
smaller electrodes with a smaller inter-electrode gap size for
machining complex features. This requires improving severely
the resolution of the anodic dissolution and respectively the
achieved accuracy. These developments led to the appearance
of a new area of ECM machining technology defined as
‘Pulsed Electrochemical Machining’ (PECM) [3–5]. PECM
uses voltage pulses instead of continuous voltage enabling a
better feature resolution [4].
This new technology can nowadays be applied at a
micrometre scale and is called ‘Pulse Electrochemical
Micromachining’ (also referred to as μECM, μPECM,
EMM, PECMM, PEMM) [6–9]. In most papers, the frequency
and the pulse duration are respectively much higher and
much shorter than in initial PECM