[ILLUSTRATION OMITTED]
Castings aren't always aesthetically pleasing, but when they
are, it's worth taking a closer look. The 2008 Casting of the Year
(pictured) is one of the beautiful ones. But the other eight prize
winners in the 2008 AFS/ECS Casting Competition are all beautiful in
their own way, whether they exhibit the benefits of the casting process,
show marketability or simply satisfy their customers' needs
impeccably.
The oil tank shown fits on a Harley Davidson motorcycle; other
industries that benefitted from this year's award winners were
material handling, agriculture, energy production, military, heavy truck
and automotive. It was those customers who were the real winners.
Casting of the Year
[ILLUSTRATION OMITTED]
Harley-Davidson Oil Tank Carley Foundry Inc., Blaine, Minnesota
Material: A356-T6 aluminum.
Process: Semi-permanent mold.
Weight: 9.25 lbs.
Dimensions: 14 x 10 x 8 in.
Application: Oil reservoir and style item.
Converted From: Plastic.
* The design beat out a plastic oil tank initially conceived by the
customer, as well as a multi-piece fabrication.
* By casting in oil circulation tubes, the metalcaster helped make
the oil reservoir more efficient and reduced the number of components in
the assembly.
* Using a unique surface finishing technique and subcontracted
machining and painting, the metalcaster delivered a complete part to the
customer.
Harley and Carley Team Up for Design Tag
Harley-Davidson's Softail family of motorcycles aren't
made out of plastic.
When Ron Hurth and the rest of the design team for the world-renown
motorcycle designer remembered that fact, the door was opened for a
metalcaster to design the oil tank for the new Harley Rocker motorcycle.
"[The oil tank] started out as a plastic inner tank with a
cosmetic outer shield, but they couldn't make it look good enough
for the Softail standard, which incorporates metal for most
components," Hurth said. "The thing about Harley is that a lot
of the stylists still want to stick with metal, so they didn't like
the way the plastic looked."
Plus, the plastic tank would have required considerable one-time
tooling costs, and doubts remained about its ability to withstand the
high heats it would be exposed to on the body of the motorcycle.
Pouring A356 aluminum into semi-permanent molds, Carley Foundry
Inc.. Blaine, Minn., offered a solution to the majority of the problems
presented by the plastic design, as well as a fabrication proposed
immediately thereafter. The solution led them to the 2008 AFS Metal
Casting of the Year award.
"What [semi-permanent mold] does, basically, is combine all
the features of both the other tanks," Hurth said. "You get
heat resistance, the look of metal and a cost reduction from not having
to assemble the internal parts. Everything is cast and machined into one
piece, so it consolidated everything."
A Pretty Piece
The Harley Rocker motorcycle has several kinds of visible metal
pieces. Some provide the brawn--the drive-train and structural
supports--and others offer the beauty.
At first, Harley designers thought the oil tank could be lumped in
with the stronger group, the parts that need only to be shot blasted to
achieve the desired surface finish. After all, the oil tank is a mission
critical part and hardly just a nice looking piece of jewelry. But
because of its location and visibility, it later became clear that the
oil tank would complement the other more decorative pieces nicely.
"We knew it had to be cosmetic and pressure tight," said
Randy Oehrlein, Carley's vice president of engineering. "It
had to be pretty, but a more effective part."
The metalcaster couldn't just blast the casting in the
traditional manner and expect to achieve the fine surface finish it
desired. To solve the problem, Carley employs a variant of a vibratory
deburring process, which makes the critical cosmetic casting surfaces as
smooth as the paneling on a luxury automobile.
Carley then subcontracts several different painting processes to
give the smooth casting its color and sheen. For black, blue, pearl and
red bikes, a wet spray is employed. Powder coat dresses up satin
stainless bikes.
[ILLUSTRATION OMITTED]
"We are responsible for the part as the Tier One
supplier," Oehrlein said. "Even though we don't do
machining and painting in-house, we were responsible for finding the
sources. The multi-step manufacture of the assembly is controlled by
Carley straight to the bike."
More Than Pretty
The Harley Rocker's oil tank had to do more than just look
good. The success of the bike's circulatory system depended on an
effective part. "To build such a part, Harley and Carley engaged in
a vigorous game of design tag.
However, the team played a game of tag that is more familiar in the
world of wrestling than in the schoolyard. The object is to tag your
partner when you need help, rather than to make them "it." And
when the metal casting your team is working on wins Casting of the Year,
you've defeated the other tag-team wrestlers.
Once the initial plastic design was rejected in-house by Harley
engineers, they next considered a multi-piece assembly that involved an
upper and lower die casting and a separate manifold. The design also
required the use of gaskets. However, concerns remained that the
assembly would leak--the oil level would reach above the split line
between the two castings--and cost too much due to its elevated level of
complexity.
[ILLUSTRATION OMITTED]
That's when Carley was first tagged in. "When they first
asked us to take a look, it was almost like a challenge was thrown
out," Oehrlein said.
Initially, the metalcaster proposed a one-piece aluminum design
with a core opening at its top. To achieve the oil passageways needed
within the casting, internal machining and threaded component assembly
would occur through the cored opening. This assembly also necessitated
internal bosses, creating a large isolated mass of aluminum. Keeping in
mind the manufacturing issues and noting the way an oil tank works, the
team soon threw that idea out of the ring.
[ILLUSTRATION OMITTED]
Improving Circulation
The Rocker's oil tank operates essentially like a heart,
drawing oil in and then resupplying it to the test of the
motorcycles" vital parts. In the initial design presented by
Carley, though, the off entering the tank was circulated in only a small
section of the component before being redistributed.
Because of the limited size of the cored hole in that design, the
oil channels could only be built in a small, pre-determined area.
"It was kind of like building a ship in a bottle,"
Oehrlein said.
This created two problems for the motorcycle producer--considerable
wasted space existed within the tank, and the hot oil built heat as it
circulated in a closed loop. With the tank located close to the
motorcycle operator's leg, that heat would have posed an
operational danger.
Fortunately, Carley tagged back in with the ability to cast the oil
circulation tubes directly into the component. This reduced the isolated
mass as well as solidification time in the remaining mass. With the
space constraints of the core print opening eliminated, the tubes were
constructed to span the length of the tank, and the oil could be
circulated through off from the engine now gets pumped into a location
away from the rider's leg, wraps around a corner and leaves from
the other side.
Through another series of tagging in and out, Harley and Carley
tackled numerous castability issues. They created ribs and bosses to
retain the oil circulation tubes, added a riser to increase the feed and
heat mass, added a cooling fin to enhance directional solidification,
thickened certain design elements to aid in metal flow and feeding, and
designed a waffle pattern on the component to increase surface area and
enhance solidification.
"They selected us and said, 'we have the best tentative
mousetrap, now let's work this down until everyone's
happy,'" Oehrlein said.
Best-In-Class
[ILLUSTRATIONS OMITTED]
Material Handling Steering/Linkage Assembly
Piad Precision Casting Corp., Greensburg, Pennsylvania
Material: Brass.
Process: Permanent mold chill casting.
Weight: 9.82 lbs.
Dimensions: 10 x 8.5 x 6.7 in.
Application: Steering linkage for a pallet truck.
Converted from: Multi-piece weldment.
* The brass casting was redesigned from a weldment composed of 10
pre-fabricated pieces, 19 weld joints and four bushings, eliminating
some machining and the need for stress relieving.
* The permanent mold process produced the part in near-net-shape
and reduced its weight by 10%.
Best-In-Class
[ILLUSTRATIONS OMITTED]
Agri Speed Hitch
Dotson Iron Castings, Mankato, Minnesota
Material: Austempered ductile iron and ductile iron.
Process: Green sand.
Weight: 70 lbs.
Dimensions: 30 x 24 x 8 in.
Application: Enables hookup and disconnection of farm equipment.
Converted From: Steel weldment.
* The agri-speed hitch enables the automatic hookup and
disconnection of farm equipment without requiring the operator to leave
the cab.
* The part was reverse engineered from the customer's
weldment, resulting in a 30% weight reduction and 40% cost reduction.
Best-In-Class
[ILLUSTRATION OMITTED]
Static Mixer Tube
Castalloy Corp., Waukesha, Wisconsin
Material: White iron.
Process: Nobake sand casting.
Weight: 124 lbs.
Dimensions: 32 x 11 in.
COPYRIGHT 2008 American Foundry Society,
Inc. Reproduced with permission of the copyright holder. Further reproduction or distribution is prohibited without permission.
Copyright 2008 Gale, Cengage Learning. All rights
reserved. Gale Group is a Thomson Corporation Company.
NOTE: All illustrations and photos have been removed from this article.