Microscale Testing and Characterization Techniques for Benchmarking Crystal. . .
101
Fig. 2 Image of wire EDM
machined René 88
microsample with gage
dimensions of 500 × 500 μm
dielectric fluid, usually deionized water. The charged wire is then guided along
a programmed path to cut the desired shape, acting as one electrode while the
workpiece acts as a second electrode [65, 66].
Due to the nature of the wire EDM, there are limits to the level of quality that
can be achieved in sample machining. However, there are multiple ways to improve
the quality of samples. The typical EDM cutting process can cause significant
surface roughness and damage in the form of a recast layer because of the melting,
vaporization, and resolidification of material that occurs. The main parameters that
can be adjusted for EDM are the cutting speed, power, and water flow. The wire
EDM system used in this study was built by Fanuc Robocut. In initial setup, the
user selects a material type and the thickness of object being cut, and the machine
provides suggested machine parameters. Although these parameters cut the material
well at the macroscale, the surface quality is rarely suitable for microtensile samples.
In some cases, if a foil of material being machined is too thin, the machine may not
be able to recommend a setting at all or will give an incorrect setting. Figure 2 shows
an image of the dogbone sample geometry machined using a wire EDM operating
with optimized settings to minimize sample surface roughness. These optimized
settings included using multiple passes, starting with a rough cutting pass, followed
by a finer cutting pass using less voltage, as well as minimization of water flow to
reduce sample vibration during cutting.
As a machine typically used for larger parts, there are drawbacks to the wire
EDM as a tool for manufacturing microtensile samples. Samples have to be
101
Fig. 2 Image of wire EDM
machined René 88
microsample with gage
dimensions of 500 × 500 μm
dielectric fluid, usually deionized water. The charged wire is then guided along
a programmed path to cut the desired shape, acting as one electrode while the
workpiece acts as a second electrode [65, 66].
Due to the nature of the wire EDM, there are limits to the level of quality that
can be achieved in sample machining. However, there are multiple ways to improve
the quality of samples. The typical EDM cutting process can cause significant
surface roughness and damage in the form of a recast layer because of the melting,
vaporization, and resolidification of material that occurs. The main parameters that
can be adjusted for EDM are the cutting speed, power, and water flow. The wire
EDM system used in this study was built by Fanuc Robocut. In initial setup, the
user selects a material type and the thickness of object being cut, and the machine
provides suggested machine parameters. Although these parameters cut the material
well at the macroscale, the surface quality is rarely suitable for microtensile samples.
In some cases, if a foil of material being machined is too thin, the machine may not
be able to recommend a setting at all or will give an incorrect setting. Figure 2 shows
an image of the dogbone sample geometry machined using a wire EDM operating
with optimized settings to minimize sample surface roughness. These optimized
settings included using multiple passes, starting with a rough cutting pass, followed
by a finer cutting pass using less voltage, as well as minimization of water flow to
reduce sample vibration during cutting.
As a machine typically used for larger parts, there are drawbacks to the wire
EDM as a tool for manufacturing microtensile samples. Samples have to be