the increasingly perfected science of machining … · the increasingly perfected science of...
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April 2015 | AdvancedManufacturing.org 89
Composites maChining
The Increasingly Perfected Science of Machining Composites
A 1965 Shelby Cobra 427
shown at the Detroit Auto Show
was additively manufactured on a
Cincinnati BAAMCI machine by
DOE’s Oak Ridge National Laboratory
(ORNL), one of seven founding members
of the Institute for Advanced Composites
Manufacturing Innovation. The Detroit IACMI
branch will get $70 million to develop a robust
supply chain to improve materials, handling, and
machining properties for automotive composites.
Jim Lorincz
Senior Editor
As use of composites matures in
aerospace, how to machine the
advanced materials grows up too,
with advanced tooling solutions
and tested approaches
Thanks to the aerospace industries and large quality-
intensive programs such as the Airbus 380 and Boeing
787, the business of machining composites has moved
into the mainstream of the manufacturing industry.
There’s a bevy of tools, specialty tools and know-how about how
to machine composites today, which helps make the complex
materials ripe for expansion into other areas of industry.
The auto industry is the next big growth area for the light-
weighting, strength, and design flexibility that composites offer.
BMW’s Vision Future Luxury concept car introduced last year
showcased how “subtractive modeling” could be used to design
interior structure components with carbon fiber reinforced plastic
(CFRP) and structural load-bearing layers of aluminum and deco-
rative and functional wood and fabric—milled down to reduce
total weight.
More car and truck components made with composites, and
a fully developed supply chain to support them, are on the way.
When the Strati 3D-printable car rolled out of IMTS 2014 last
Photo courtesy Cincinnati Inc.
90 AdvancedManufacturing.org | April 2015
September, it represented 44 hours of additive manufacturing
on Cincinnati Inc.’s BAAMCI (Big Area Additive Manufacturing
Machine) and a full day of subtractive milling by Local Motors
Inc. (Phoenix, AZ) of the ABS plastic/carbon fiber composite
on a CNC router. Local Motors says 24 hours of AM is a realiz-
able goal.
At the Detroit Auto Show, ORNL, one of seven founding
members of the Institute for Advanced Composites Manufac-
turing Innovation (IACMI), showcased
a 3D-printed 1965 Shelby Cobra 427.
$70 million of the Institute’s $259 mil-
lion public-partnership of 122 member
companies will fund IACMI’s Detroit
branch to develop a robust, risk-free
supply chain for advanced compos-
ite materials—to improve materials,
handling, and machining properties for
automotive applications.
Automotive Chases Lightweighting
Promise of Composites
According to Randy Von Moll,
technical sales director, Fives Cincinnati
(Hebron, KY), automotive manufactur-
ers are following the lead of the aero-
space industry exploring the potential
of composites to reduce weight and
increase fuel efficiency. “We may see
the main chassis of the car being built
from composites one day in the future.
The hood is a good example of a part
that weighs a lot and can benefit from
lightweighting,” said Von Moll.
“Automakers are striving to manu-
facture composite parts to net shape.
They can get pretty close to net shape,
but virtually every part that is built
from composites needs some form of
machining to finish it. There are only a
couple of parts in composites that I can
cite that can be made all the way to net
shape. Usually there’s a certain amount
of excess material, around the periph-
ery of the part in aerospace because of
the way that the composite part is built
up that it always has to have a pro-
file trim done on it and typically holes
drilled,” said Von Moll.
“For the larger aircraft parts, our
re-engineered PMT [precision, mill, trim]
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Composites maChining
92 AdvancedManufacturing.org | April 2015
traveling gantry-type machine can extend the X axis for a large single part or be set
up in multiple work zones with light-curtain dividers or physical barriers between
zones. All of the new aircraft designs are getting designed more accurately to
minimize or eliminate the hand fitting that has historically taken place during the
aircraft manufacturing process. The aircraft producers want to build airplanes more
like the car builders build cars and pull them together on a moving line and they’re
making a lot of progress toward that. Today virtually all the newer Boeing models
are built on moving lines,” said Von Moll.
“There is a wide variety of tooling for different types of material that is being
cut. Compresson-type cutters featuring both left-hand and right-hand helixes have
been developed to machine laminated stacks of material without delamination. A
lot of machining that is done of composites also involves other materials. It isn’t
unusual for us to supply a solution for a composite material that has carbon fiber,
Kevlar, usually a nonmetallic honeycomb core or foam, a copper mesh for lightning
strikes, a titanium sheet in there for additional design purposes. It would be more
unusual for us to have just a uniform material type. The sandwich structures are
getting more complex,” said Von Moll.
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Composites maChining
At IMTS 2014, the Strati car was additively manufactured in 44 hours by Local Motors
using an ABS plastic/carbon fiber composite on a Cincinnati BAAMCI machine. A
full day of subtractive milling was performed before final assembly. Local Motors
has targeted 24 hours as 3D printing time required for the Strati in the future.
Phot
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94 AdvancedManufacturing.org | April 2015
Machining CFRPs Not Like Cutting Metal
According to Don Graham, Seco Tools Inc. (Troy,
MI), carbon fiber reinforced plastics (CFRP) are
machined by a series of brittle fractures in which the
cutting action shatters the abrasive hard carbon fibers
producing powder or brush-type chips. “Machining
optimization of composite materials in drilling has to
resolve problems of fiber pullout, uncut fibers and
delamination, especially in exiting the material by
addressing issues resulting from dull edges, improper
prep, feed rates that are too aggressive, and wrong
drill angles. For milling applications, fiber pull out,
uncut fibers, delamination, chatter/vibration, and torn
fibers benefit from some combination of replacing dull
cutters, remedying prep, reducing aggressive feed
rates, changing too high helix angles, improving cutter
angle of attack and better fixturing,” said Graham.
“Tools can fall into one of two categories,” said
Graham. “End mills with a double helix—both a left and
right-handed helix—for cutting action
use a guillotine action and are particu-
larly useful for honeycomb materials
and fiber reinforced materials as well.
The idea is that you shear the fibers,
not fray, split, or delaminate them,” said
Graham. Seco Tools’ Jabro JPD and
JC end mills were developed specifi-
cally for composite materials. The JPD
group of solid carbide end mills features
brazed polycrystalline diamond plates
with through-coolant channels for chip
and dust evacuation and are available in
square, ballnose, and compression-type
end mills. The JC group includes the
875 solid carbide router with a special
edge treatment and diamond coating.
For drilling CFRP materials, Seco
Tools offers drills with two different ge-
ometries: C1 geometry has an optimized
drill point for carbon fiber and in stacked
titanium/carbon fiber or aluminum/
carbon fiber when exit is in the carbon
fiber. The diamond-coated drill has a
double chamfer and two different angles
for exiting on the carbon fiber without
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Composites maChining
PCD-veined series 85 geometry cutting tools are monolithic in structure
and can be ground with various geometries and features that were once
difficult to achieve in the past using conventional brazing methods.
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April 2015 | AdvancedManufacturing.org 95
splintering and delamination. C2 geometry is used for stacks
entered on carbon fiber and exited on titanium or aluminum,
controlling chips so that the metal chips don’t roughen the
carbon-fiber surface. C1 and C2 drills are coated with a CVD
Dura coating.
Many Industries Are
Affected by Composites
When it comes to composites,
everybody thinks of aerospace first, ac-
cording to Adrian von Rohr, KOMET of
America Inc. (Schaumburg, IL). “That is
completely wrong. If you look around
composites are becoming more and
more interesting for applications where
a heavier material component made
from steel or cast iron can be replaced
with a composite that requires less
energy to move the object. Also, com-
posites allow extreme positive features
and physical hardness and toughness
to be designed into components. In the
automotive industry, weight reduction
of composites results in fuel efficiency.
BMW, for example, has launched a
car that is completely made out of
composites, except for the engine and
drive train. It’s not a prototype, and
BMW has a manufacturing line for that
car,” said von Rohr.
Fiber reinforced plastics (FRP) are
durable, but also lightweight, reducing
loads, drag, and energy consumption.
However, composite materials present
their own special machining challenges.
They are brittle, and the glass fibers
within them are particularly abrasive.
The glass sections of FRP require
particularly sturdy drills and tools, while
the plastic pockets need to be ma-
chined with care. “KOMET’s portfolio of
tools includes drills, mills, and routers
for opening holes up, milling slots, and
cleaning trimming and drilling to get to
the final shape. These tools are used
both on manual and CNC machine
tools. “The real challenge is to match the tooling solution
with the right coating, tool geometry and tool body for the
composite application based on the information that the
customer supplies to us,” said von Rohr.
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96 AdvancedManufacturing.org | April 2015
Full Range of Composite Machining Products
There is major growth in the use of composites in virtually
every industry, including aerospace, automotive, and medi-
cal, according to Jeffrey Stephens, OSG USA Corp. (Glendale
Heights, IL). “We have a number of tools designed specifi-
cally for aircraft production. The EXOPRO AERO BNC router
with our patented ultrafine diamond coating is designed for
trimming carbon fiber and glass cloth. It features a fine nicked
geometry for roughing as well as over-
lapping with finishing. The nick is actually
a flat portion making the tool highly ef-
ficient in producing clean cutting edges
without delamination or leaving fibers
uncut when used on CNC machines.
The CNC router is the workhorse,
capable of plunge and helical interpola-
tion,” said Stephens.
“If you look at our current composite
products, we’ve developed roughing
and finishing routers and drills for CNC
applications that are solutions tailored to
the customer’s requirements. There are
still a lot of applications in aircraft where
the parts are awkward, sometimes the
fixturing isn’t very good. They might use
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Composites maChining
Compression-style end mills with a double
helix (left hand and right hand) like the
Jabro JC845 are particularly useful for
shearing honeycomb materials and fiber-
reinforced composites without fraying,
splitting, and delamination.
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Tool
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See us at AERODEF Booth #233
April 2015 | AdvancedManufacturing.org 99
a vacuum frame or even adhesives to hold the part down and we have to develop
cutting tools that reduce the cutting forces,” said Stephens. “The EXOPRO AERO
HBC router features a diamond-coated herringbone for high-feed CNC applications
that produces excellent surface finish. The EXOPRO AERO drill features diamond
coating for clean entry and exit from the composite material.”
Machining honeycombs is an entirely different matter. “In our original herring-
bone compression router design, we featured a 30° helix. Compression-style rout-
ers compress the laminate together with a left-hand and right-hand helix, leaving a
clean edge on both top and bottom. What we found was that the 30° didn’t work
in all cases, especially for fibers with higher strength. So we developed a 45° helix
with a higher shearing capability for more difficult fibers. For the most difficult to cut
Kevlar honeycombs, we developed a 60° helix that performs like a pair of scissors
to cut the Kevlar very cleanly,” said Stephens.
PCD Veined Drills Feature Unique Solution
Many of the most difficult challenges still originate with aircraft production
generally and with jet engine applications specifically. The latest surge in jet engine
design and production for new aircraft and for retrofit applications will ramp up
demand for machining the toughest of materials, ceramic composites, with the
hardest of materials, diamond.
Sandvik Coromant (Fair Lawn, NJ) has developed its unique solution in a series
of PCD-veined cutting tools for drills, mills, and end mills. “Series 85 geometry
cutting tools provide a real alternative to brazed diamond-tipped tools, especially
for ceramic composites that require the hardest material to drill,” according to Linn
Win, composites product specialist for Sandvik Coromant. “Our PCD-veined series
85 geometry cutting tools are monolithic in structure. That means that they can be
ground with various geometries and features that were once difficult to achieve in
the past using conventional brazing methods,” said Win.
The monolithic PCD-veined tool is formed by slitting a carbide nib in precise
location and configuration in accordance to the customer’s requirements, filling
the carbide nib with diamond powder, and then sintering the tool under high
pressure and high heat. Once the nib is extracted from the pressure and heat
vessel, the diamond has bonded with the carbide as one monolithic structure
leaving no brazing weak points and allowing more options when grinding the
cutters face
geometry. “The
monolithic struc-
ture allows cutters
to be reground
multiple times, so
that tools have
the durability of
diamond as well
as the versatility
of carbide,” said
Win. Buy online today. www.birchwoodtechnologies.com
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Composites maChining
?Cincinnati Inc.513-367-7100 / e-ci.com
Fives Cincinnati859-534-4600 / fivesgroup.com
Komet of America Inc.847-923-8400 / komet.com
OSG USA Corp.800-837-2223 / OSGtool.com
Sandvik Coromant201-794-5000 / sandvik.coromant.com/us
Seco Tools LLC248-528-5200 / secotools.com/us