30
Remanufacturing and Advanced Machining
Acidic electrolytes are advantageous as the reaction products remain dissolved in
the solution because the hydroxide ions produced at the cathode are neutralized by
a high hydrogen ion (H + ) concentration. This allows to decrease the inter-electrode
gap, as it does not get clogged with solid reaction products. Minimization of sludge
also reduces the probability of sparks.
Alkaline electrolytes, such as sodium hydroxide (NaOH), are generally avoided as
these can promote the formation of a passive film on the workpiece and, thus, require
a larger inter-electrode gap. Potassium hydroxide (KOH) is preferable in some metal
systems or in machining of tungsten carbide (WC).
Non-aqueous electrolytes are beneficial for passivating metals as they eliminate
oxygen sources that form passive films. However, conductivities of nonaqueous electrolytes are low (Leese and Ivanov, 2016).
Flow rates of electrolytes are usually in the range of 10–50 liter per minute (lpm)
(Jain and Pathak, 2017). A proper flow rate and circulation of an electrolyte in the
gap regulate temperature and remove products of the electrochemical reaction (e.g.,
hydrogen and metallic ions), thus regulating the process. Joule heating increases
MRR due to higher anodic dissolution kinetics and greater conductivity of the electrolyte. In turn, the release of hydrogen at the electrode decreases MRR because it
dilutes the electrolyte concentration and diminishes its capacity to act as a current
carrier. Metal ions from reaction products also hamper MRR if they are not properly
washed away from the workpiece surface (Ribeiro et al., 2013).
Various kinematic solutions of the ECM find their areas of application (Koryagin
et al., 2000):
1. Methods where electrodes do not move
(a) Calibration
(b) Contouring
(c) Deburring
(d) Edge rounding
(e) Marking
2. With the translational motion of an electrode
(a) Copying
(b) Piercing of holes
(c) Broaching
(d) Calibration
(e) Sharpening
3. With the rotational motion of a cathode
(a) Processing of flat and shaped surfaces
(b) Segmentation
(c) Circular notching
4. With a rotating anode
(a) Processing of shaped surfaces (external and internal)
(b) Grooving (straight and spiral)
(c) Segmentation
Remanufacturing and Advanced Machining
Acidic electrolytes are advantageous as the reaction products remain dissolved in
the solution because the hydroxide ions produced at the cathode are neutralized by
a high hydrogen ion (H + ) concentration. This allows to decrease the inter-electrode
gap, as it does not get clogged with solid reaction products. Minimization of sludge
also reduces the probability of sparks.
Alkaline electrolytes, such as sodium hydroxide (NaOH), are generally avoided as
these can promote the formation of a passive film on the workpiece and, thus, require
a larger inter-electrode gap. Potassium hydroxide (KOH) is preferable in some metal
systems or in machining of tungsten carbide (WC).
Non-aqueous electrolytes are beneficial for passivating metals as they eliminate
oxygen sources that form passive films. However, conductivities of nonaqueous electrolytes are low (Leese and Ivanov, 2016).
Flow rates of electrolytes are usually in the range of 10–50 liter per minute (lpm)
(Jain and Pathak, 2017). A proper flow rate and circulation of an electrolyte in the
gap regulate temperature and remove products of the electrochemical reaction (e.g.,
hydrogen and metallic ions), thus regulating the process. Joule heating increases
MRR due to higher anodic dissolution kinetics and greater conductivity of the electrolyte. In turn, the release of hydrogen at the electrode decreases MRR because it
dilutes the electrolyte concentration and diminishes its capacity to act as a current
carrier. Metal ions from reaction products also hamper MRR if they are not properly
washed away from the workpiece surface (Ribeiro et al., 2013).
Various kinematic solutions of the ECM find their areas of application (Koryagin
et al., 2000):
1. Methods where electrodes do not move
(a) Calibration
(b) Contouring
(c) Deburring
(d) Edge rounding
(e) Marking
2. With the translational motion of an electrode
(a) Copying
(b) Piercing of holes
(c) Broaching
(d) Calibration
(e) Sharpening
3. With the rotational motion of a cathode
(a) Processing of flat and shaped surfaces
(b) Segmentation
(c) Circular notching
4. With a rotating anode
(a) Processing of shaped surfaces (external and internal)
(b) Grooving (straight and spiral)
(c) Segmentation