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Micro
End Mills
l .002" to .125" Cutter Diameter
l Decimal & Fractional Sizes
l Long Shank & Long Reach
l Stub Flute & Metric Mills
l AlTiN & Diamond Coating
l Orders received by 5:00 PM
eastern time ship same day
Made
In USA
MicroEndMill.com
Your on-line source
for carbide micro end mills
sales@microendmill.com
TEL 781-582-0101 • FAX 781-582-0202
14 | MAY/JUNE 2012 | MICROmanufacturing
MICROmachining
according to Hurst, the company offers
its NanoCAM 3D programming and
analysis software as a machine option.
Matthias Reck, chief technology
officer for machine builder Datron AG,
Mühltal, Germany, concurred that end
users need to apply a single-crystal, or
monolithic, diamond tool to impart
the finest finishes when, for instance,
cutting aluminum. PCD tools, on the
other hand, have bonds between the
crystals that increase the roughness
of a machined surface. “For Plexiglass,
however, you can work with diamond
tools, polished single-flute tools or
CVD thick-film, diamond-coated tools
and get a perfect surface,” he said.
Reck added that it’s important for a
machine control to provide smoothing
functions, such as B-splines, to impart
smooth surfaces and eliminate surface
errors when changing cutting speeds.
To meet the stringent surface-finish
requirements of micromanufacturers,
Datron recently introduced the
C5 5-axis simultaneous milling
machine, which has a spindle speed
up to 48,000 rpm. The rotary swivel
axis, driven by dynamic torque motors,
reportedly ensures reproducibility
while maintaining high process
reliability.
The milling machine has linear
glass scales that provide a high level
of precision and eliminate thermal
effects, such as backlash and other
drive errors, according to Reck. And
to avoid having a change in the spindle
temperature negatively impact the
workpiece surface, a spindle should
have a tempering device that controls
temperature to better than ±0.1° C, he
added.
Makino’s Bradford agreed that sharp
temperature fluctuations during the
machining process are detrimental to
surface finish, especially if it occurs over
a short period. “If a total change of 5° F
happens over 2 to 3 days, that’s actually
not a significant issue,” he said.
It’s important to establish an error,
or tolerance, budget for surface finish
when micromachining, Bradford
emphasized. That enables a user to
determine if a machine has the basic
requirements to meet the finish
specification before beginning the job.
For example, if the machine has a
positioning repeatability of ±50nm,
the best surface finish it can impart
is 100nm, based on the high- and
low-positioning factors. And if the
cutting tool has an edge roughness of
30nm, the best surface roughness it can
generate is 30nm, so the error budget
increases to 130nm. Moreover, any
thermal growth in the spindle should
also be considered.
“If you’re trying to machine to a
surface roughness of 100nm, it is
ideal to have your machine provide
a repeatable positioning accuracy of
one-half to one-third that level—or
better,” Bradford said.
Hurst pointed out that surface
finish will only be as good as the
spindle’s size-of-error motion. “We’ve
determined that 50nm is what we can