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FJournal Magazine,
April, 2009 |
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Cutting Tool Costs
Reprinted with
permission from FF Journal |
 art
of a progressive die's tooling was causing major production delays
for Steve Paul, tool room manager at ThyssenKrupp Automotive Ltd.,
Cannock, England. After 10,000 to 15,000 hits, it would break,
causing downtime and increasing maintenance costs.
ThyssenKrupp Automotive produces stampings for many of the
European and Japanese automakers. Toyota is one of its main
customers, but it also does stampings for General Motors, Nissan,
Ford and Jaguar.
Although the company doesn't produce any Class-A exterior body
panels, it primarily stamps all the underskin body panels and
body-in-white parts. The company also stamps high-strength steels
and high-strength, low-alloy steels. The largest component stamped
is a dashboard panel. At the Cannock site, there are 1,100
employees, and Paul has 35 people in the tool room to service the
facility.
 Paul
says there was a problem with a small progressive die that made a
U-shaped bracket out of 2.4-mm-thick mild-carbon steel. One of the
stages within the die kept breaking.
"It's quite a thin construction across the die," he says. "It
was [similar to] a bridge piece, and it was cracking on both sides
on the bridge. When it broke, it was increasing our downtime on
the die. We tried all sorts of different tool steels, including D2
and A2."
The company produces around 8,000 parts per run of this
approximately 6-in. square part.
After reviewing the die's construction, Paul felt it couldn't
be redesigned to make it last longer. Instead, he began a search
for a different type of tool steel to increase its life and found
one called Toolox 44 from International Mold Steel Inc., Florence,
Ky.
Although he was reluctant to try the steel, Paul didn't have
much choice. "We used Toolox 44 as somewhat of a last attempt to
repair the die and make it last longer/' he says. "It was a
success. With the A2 and D2 tool steels, we were getting probably
10,000 to 15,000 hits before the die broke. With the Toolox 44, we
did 254,000 hits on the die insert.
"We ran it for about 12 months, and there were a number of
other issues with the die not involving the Toolox. The top punch
was still D2 steel, and we had one instance where one of the other
D2 steel punches broke and dropped across the die where the Toolox
44 is used. After the press came down on the broken punch, we
found that the Toolox 44 insert was still in one piece. This
incident could've caused a lot of damage to the tool, but it
didn't. We've been quite impressed with the steel."
Paul says the company also tried quite a few other materials,
and none stood up to the stamping until the company tried the
Toolox 44.
"Although it's a much tougher steel, it isn't more difficult to
machine," he says. "But most of our dies are produced using EDM
equipment."
Along with the Toolox 44 steel, Paul says the company has also
been trying different metal coatings on its dies to improve
productivity. Titanium and a two-stage aluminum-carbonite coating
will be used.
 After
the success of using Toolox 44 for this application, Paul says the
company will be applying it in other projects. "It'll be used in
our progressive tooling because the die sections tend to be more
complex with less support underneath rather than using it for
tooling that produces larger stamped panels where we don't have
support problems," he says. "We certainly won't give it an easy
process to continue our trials on either."
Toolox 44 history
Toolox 44 was originally developed from Hardox 660 steel by SSAB
Oxelösund AB, Oxelösund, Sweden. It's a new quenched-and-tempered
tool steel with high-impact resistance and low-residual stresses,
giving it excellent dimensional stability. By using an intensive
quenching process, the company's able to reach the same hardness
as regular tool steel with less carbon and fewer alloying
elements. Through this process, Toolox 44 has fewer carbide
inclusions, making it easier to machine.
Because it's already at 45 HRC, heat treating isn't needed
after machining, and it can easily be machined with either carbide
or high-speed-steel cutting tools. It's well-suited for stamping
applications, for which it offers excellent impact toughness and
long service life, according to Tom Schade, executive vice
president of International Mold Steel.
Another area in which Toolox 44 has increased productivity is
blanking dies. In one application, nitride-coated Toolox 44 was
used for a blanking die and blanked a 3.8-mm-thick mild-carbon
steel sheet. Before Toolox was used, the company tried a D2 tool
steel for the die at 58 to 62 HRC, which gave it 10,000 hits
before breaking. The company then tried a D2 tool steel at 54 to
56 HRC, which gave it 10,000 hits before breaking. Next, the
company tried a DC 5 3 tool steel with 8 percent chromium, which
gave it 15,000 hits before breaking. After failing with these tool
steels, the company tried the Toolox 44 with a nitride coating on
the surface. It's given the company more than 254,000 hits and
remains in operation.
About International Mold Steel, Inc.
International Mold Steel, is a leading supplier of tool steels
uniquely designed to produce higher quality products (with
greater detail and definition) at less cost. This company has
pioneered steel solutions for a host of Fortune 500 companies
in a variety of industries. They provide: Matrix High Speed
Steels and DC-53 for die steel markets and supply these mold
steels for plastics and rubber markets: Porcerax II, NAK 55,
NAK 80, DH2F, Premium H-13, PX5. International Mold Steel
Inc., is a global company headquartered in the U.S.A., with
sales/service throughout North America, Europe and South
America. Thomas Schade is Executive Vice President for
International Mold Steel. He has held various positions in the
production and distribution of specialty steels since 1966.
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