High-performance coating helps stamper fight
Dies last longer, need no regrinding
December 7, 2004
stamper likes to have press downtime. It simply costs too much
money. For this reason, progressive stampers invest quite a
bit of time, money, and energy in finding ways to fight
downtime and to make their presses as productive as possible.
Omni Mfg. Inc. is one such stamper. A mentality of continuous
improvement permeates the entire business, including the
toolroom that manages the hundreds of dies working in its 68
The toolroom staff
doesn’t merely look for better ways to design the tools it
builds and keep the dies in good repair. It helps in the fight
for productivity in another, more direct way. The toolroom
staff has about 5 percent of the dies in its inventory coated
to prevent the galling and heating that occur during severe
draws. It also relies on coatings to improve the performance
of certain pierce punches.
As one of Omni’s presses forms the
heavy-duty door hinges, a transfer mechanism advances the
workpiece to the next station in the die. Because Phyge’s
FortiPhy™ UltraEndurance™ coating on the four forming
inserts inhibits galling and metal pickup, the four
inserts last for nearly 200,000 hits, which is
approximately 43 percent longer than a CVD TiC coating
would last on the same tool steel.
look to coat anything that has a deep draw, does a lot of forming,
or forms stainless steel,” said Bob Prater, toolroom manager. In
some cases, such as forming stainless steel, coatings are
mandatory for forming the part properly and achieving an appealing
The coatings provide a hard, slick barrier that not only protects
the die’s surfaces from wear, but also enhances flow of the steel
as it deforms against the die. The slickness of the coating
reduces the friction that can cause bits of workpiece material to
become welded to the tool. Because the tool picks up these tiny
bits of workpiece material, tool- and diemakers refer to this
process as pickup, which can result in workpiece galling, scoring,
Materials such as stainless steel and aluminized steel are prone
to this phenomenon and often receive ugly blemishes as a result.
However, coatings inhibit the abrasion and welding that result in
pickup. This, in turn, reduces a die’s downtime. Operators can run
dies longer before having to stop the press for tool maintenance.
Producing these heavy-duty door hinges is 10 times more economical
since Omni switched both the substrate and coating on the inserts
that form them inside the stamping die.
Productivity Hinges on Press Uptime
|Omni had a
particularly stubborn application in cutting and drawing
heavy-duty door hinges from 5-mm-thick, high-strength,
low-alloy steel—a project that originally had been contracted
to another stamper. The die for this application required
frequent reconditioning. With the carbide-based thermal
diffusion (TD) coating that the previous stamper had been
using, the form inserts in the die lasted 20,000 to 25,000
hits before they needed to be recoated.
Producing these heavy-duty
door hinges is 10 times more economical since Omni
switched both the substrate and coating on the inserts
that form them inside the stamping die.
“In my mind, that wasn’t an
acceptable number,” said Prater. He thought that the coatings
should last at least 100,000 hits.
To achieve this goal, he began
experimenting with different substrates and coatings. The first
round of experiments involved two conventional chemical vapor
deposition (CVD), titanium carbide-based (TiC) coatings on three
tool steels: D2, conventional M4, and powder metal M4. The
coatings performed approximately the same, boosting insert life to
between 40,000 and 45,000 hits. Although performance doubled, it
still fell short of the goal that Prater had in mind. So he
continued his search for a better combination of substrate and
During the search, he heard about a new coating/substrate
combination that one of his tool suppliers used for severe draws.
The dies were made of DC53 tool steel and coated with FortiPhy
UltraEndurance™ a coating from Phygen Inc.
Using a proprietary physical vapor deposition (PVD) process that
exploits plasma acceleration, the coater has been able to deposit
a thin, hard, dense protective layer at about half the temperature
of conventional hot TD and CVD processes. Because the resulting
coating has a single-phase, nanocrystalline structure, it has the
critical load strength to withstand the constant pounding and
extremely high forces inherent in metal stamping. Moreover, the
hard coating also has low coefficient of friction (less than 0.1),
making it a kind of lubricating agent.
Omni had this set of four forming inserts stripped, polished, and
recoated with Phygen’s coating. The coating has the adhesion and
wear resistance of CVD processes, but because it is applied at a
relatively low temperature, it does not distort the tooling. This
characteristic lends itself to recoating the tooling over and over
|To test the
coating, Prater bought a bar of DC53 from International Mold
Steel Inc. and made two sets of inserts from it to conduct a
controlled study that compared the performance of the new
coating with the conventional TiC coating on this unfamiliar
grade of tool steel.
“All of the DC53 came from the same bar,” said Prater. “They
[the test inserts] were heat-treated at the same time and
processed in the same way.” The only difference was that the
two sets went to different coaters to receive their respective
Although both substrate-coating combinations improved tool
life substantially and more than met Prater’s performance
goal, FortiPhy outperformed the TiC coating by 43 percent. It
lasted approximately 199,000 hits, whereas the CVD TiC coating
lasted 139,000 hits.
Omni had this set of four
forming inserts stripped, polished, and recoated with
Phygen’s coating. The coating has the adhesion and wear
resistance of CVD processes, but because it is applied at
a relatively low temperature, it does not distort the
tooling. This characteristic lends itself to recoating the
tooling over and over again.
Not only did the longer-lasting
coating reduce downtime by allowing the die to run longer between
reconditionings, but Phygen’s PVD process also did not distort
Omni’s die inserts. A distorted insert requires grinding to get it
back to its original shape.
“Anytime you have blocks that fit together, you have only a
thousandth [of an inch] or so to play with,” Prater said. Despite
the limitation, the inserts fit in the die after the coating
process and conformed to the print.
This had been a persistent problem for Omni. “If we’d send out
rings, for example, for coating, they’d come back too big,
egg-shaped, or too small,” said Prater. “So we would have to
regrind them back into shape.”
The coating has a single-phase,
nanocrystalline structure that provides the cohesive strength and
coating density to withstand the constant pounding and extremely
high physical forces inherent in metal stamping. The hard, dense
coating also has a coefficient of friction less than 0.1, allowing
it to emulate a lubricating agent.
Phygen’s cooler PVD process
eliminates the tendency for tooling to become distorted. “We
temper our tool steel at roughly the same temperature that Phygen
applies its coating,” Prater said. “So, theoretically, the
stresses are relieved.”
How Many Hits?
Despite the benefits that his controlled
study has documented, Prater has enlisted Phygen’s help in
running another battery of tests. The first of these tests
will help Omni determine the optimal number of strokes that
the door hinge die can run the coated inserts before pulling
them for reconditioning.
The coating has a single-phase,
nanocrystalline structure that provides the cohesive strength
and coating density to withstand the constant pounding and
extremely high physical forces inherent in metal stamping. The
hard, dense coating also has a coefficient of friction less
than 0.1, allowing it to emulate a lubricating agent.
“I think that
the press operators ran [both sets of dies] maybe 10,000 pieces
more than they should have” in the first study, Prater said.
Although the results showed the new coating/ substrate combination
exceeded his goal by nearly 100 percent, he wants to determine the
right number of hits for production to use as a guideline for
Two other experiments are pending. One is testing the coating on a
tool for producing an exhaust resonator, and the other is testing
it on some deep-drawing rings for manufacturing stainless steel
bushings for front-end suspension units.
Management at Omni puts great stock in such dividends and invests
heavily in finding more productive ways of stamping better parts.
In fact, it credits these gains and others from continuous
improvement programs as crucial to the company’s growth throughout
the past few years when many of its competitors closed their
“We like new technology,” Prater summarized. “We’re fairly
aggressive about trying new things.”
Omni Mfg. Inc., 901 McKinley Road, St.
Marys, OH 45885, 419-394-7424, fax 419-394-3437,
International Mold Steel, 6796 Powerline Drive, Florence, KY
41042, 800-625-6653, fax 859-342-6006,
Phygen Inc., 1400 Marshall St. N.E., Minneapolis, MN 55413,
612-331-4224, fax 612-331-4230,
permission from The Fabricator.