From Cutting Tool Engineering Magazine May 2008
It’s all about perspective. Steve Cotton,
owner of Micro Precision Parts
Manufacturing Ltd., got his start as a
watchmaker, so his definition of “large”
parts fits what many shops consider
small. “If we are working outside of a 1"
to 2" parameter, it’s a big part for us,” he
said. Typically, parts are so small that 50
of them can be placed on a penny. Making
small parts is not simply a case of
dealing with smaller dimensions. All the
elements of the machining system “have
to work together,” Cotton said.
 The Vancouver, B.C., shop handles
production orders for as many as 30,000
pieces annually, but also machines single-
digit runs of custom parts and replacements
for obsolete items. Examples
of the tiny, precise components the shop
produces include miniature gears and
gearboxes for the robotic industry and
lens drive gears for cameras.
Cotton founded his shop in 2004,
focusing on making parts for watches,
especially gears. “We started servicing
old clocks and vintage watches,” he said.
“Half of them you can’t get parts for anymore.
I investigated CNC machining to
make some of the obsolete parts.”
He bought a benchtop CNC lathe
and used it for a year. “Even though it
was automatic to a certain point,” Cotton
said, “it was still labor intensive.”
To reduce tool change time and labor,
he contacted Thomas Skinner & Son
Ltd., a 104-year-old industrial distributor
in Richmond, B.C., seeking advice
on acquiring a CNC machine with an
automatic toolchanger.
After visiting Micro Precision,
Thomas Skinner Sales Representative
Roy Hankonen said, “You really have to
think small when you think of Cotton’s
shop. He has a ¾"-dia. cutter he uses as
a facemill.”
With Hankonen’s assistance, Cotton
chose an OM-2A Office Mill from
Haas Automation Inc., Oxnard, Calif.
Engineered for high-volume production
and rapid prototyping of small parts,
the VMC is small enough
to fit through a 36" door
but still provides the accuracy
and reliability of larger
units. It has a 12"×10"×20"
work envelope and a 20-
pocket ATC.
Cotton was immediately
pleased with the machine.
He said: “Once we set it
up with the toolchanger, a
gear that took me about 45
minutes on our first machine
dropped off the Haas
every 8 minutes. But what I
didn’t realize was the scope
of these machines is huge.
We’ve cut medical-grade titanium
and ceramics ranging
from alumina, silicon boron and
cubic boron nitride to extremely hard
silicon nitride.”
Cotton was also impressed with the
machine’s accuracy. For example, inspection
on a coordinate measuring
machine of a run of ceramic medical
parts showed the shop consistently met
tolerances tighter than ±10µm.
A Renishaw laser tool probe added
to the machine further boosted consistency.
“It sets every tool to the same
standard,” he said. “If you are hand setting
a tool, you can be a hundredth out
on your height, diameter and width.”
He uses the tool probe to adjust offsets
as tools wear to minimize scrap and to
assure that replacement tools cut identically.
When grinding a ceramic part,
“we put 20 tools in the carousel, tell
the machine to run for 1 hour and then
change the tool. The new tool has been
‘lasered’ as being the right size.”
Cotton also acquired a 200,000-rpm
NSK pneumatic spindle to mount in
the standard OM-2A spindle and spin
tools as small as 0.016" in diameter fast
enough to cut efficiently.
Regarding the machine’s accuracy
when processing the small parts, Haas
said the OM-2A is not simply a smaller
version of a larger machine. As an example
of the unit’s specialized engineering
features, Haas product manager Dave
Hayes said the pitch of the OM-2A lead
screw is 5mm, the finest of any Haas
product. The resulting 0.0000061"
resolution is finer than the minimum
input available from the machine control,
Hayes noted, ultimately enhancing
positioning and accuracy.
Cotton added that issues such as
tool wear and tool deflection are much
greater concerns when making his tighttolerance
parts. “For us,” he said, “when
we get a part with a tolerance that is
0.002" to 0.003", we just love it,” because
it is so simple by comparison.
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