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Metal Forming Magazine
New CrN Tool
Coatings
Keep Going and Going and
Going…
Phygen PVD-applied
chromium-nitride coatings on
deep-draw tools, form tools and cutting-tool edges last longer
than other coatings, and they go on with minimal heating of the
tool, preventing distortion and other unsavory side effects of
hotter coating processes. Here are two testimonials.
BY BRAD F. KUVIN, EDITOR
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Let’s
see: A tool coating that allows you to keep a die in the press up to
50 percent longer between tool sharpenings, and goes on without using
distortion-causing heat. Sounds like an all-around winner, enough to
convince you to convert all of your dies to a new tool-coating
process, right? Well, that’s what’s happened at Beckett Gas Inc.,North
Ridgeville, OH, which stamps aluminized- steel sheet to make gas
burners. Beckett, reportedly the world’s largest supplier of
gas-burner products for water heaters and furnaces, produces nearly 30
million stamped parts per year on seven progressive-die presses from
100- to 600-ton capacity, and 30 single-station presses.
Some progressive dies make four million
stampings per year, so maximizing hits between tool sharpenings shows
immediate return for this 15-year-old company. Its roots were firmly
planted in 1925 when founder R.W. Beckett designed and built the
Commodore oil burner for C.W. Olsen Co., which is today York
International and still a major Beckett Gas customer.
“Our engineering team constantly
presents us with design challenges,” says Rick Roth, tool and die
foreman overseeing the pressroom of the 140,000-sq.-ft. plant, “which
has caused us to continue finetuning our stamping operations. Forming
aluminized cold-rolled sheet,much of which is 0.035 in. thick, to
standard tolerances on burr height (10 percent of material thickness)
and with increasingly tight form radii (as tight as 0.03 0-in. radius
) has led us to investigate our choice of tool steels and tool
coatings. Aluminized coating makes for a very abrasive material and
can really tear up a die.” Historically, Beckett ran dies tooled with
D2, which on parts for its most popular burner, inshot burners for
furnaces, would yield only 60,000 to 80,000 hits between sharpenings,
dictated by burrs exceeding the 10-percent limit. Next the firm
switched to powdered-metal (PM) tool steels, originally ASP 23 (now
Vanadis—Beckett uses Vanadis 4 and 6 alloys) from Bohler-Uddeholm. The
switch to PM steels doubled tool life between sharpenings. A TiCN
multiple-layer coating, applied using the physical-vapor-deposition (PVD)
process, on the PM tools added another 50 percent to tool life,
getting the dies to last 200,000 to 220,000 hits between sharpenings.
“We used TiCN-coated PM for four years,
very successfully,” says Roth. “Then we learned of a new coating, a
chromium-nitride PVD coating called ST.3 SuperTough (from Phygen,
Inc., Minneapolis, MN) and decided to try it on our most critical
tools, the form and cutting tools on the inshot dies. The result was
another 25-percent increase in hits between sharpenings.”
In addition to more hits, the Phygen
coating also causes no tool distortion, an unfortunate byproduct of
the previously used hot-process coating technique. “We’d get form
tools back from the coater,” recalls Roth, “and in some cases form
rings would shrink by as much 0.007 in. due to the hot coating
process.We’d have to send the tool back and have it fixed, further
delaying production. The Phygen process goes on at only 925 F and
therefore does not cause any distortion to our tools.”
In another instance, on a newly
developed form tool for drawing inshot halves (see photo), the die has
to draw 0.035-in.-thick aluminized steel to a 3.4-in. depth and roll a
tight corner of a mere 0.030-in. radius.
“Stuffing the material quick and hard
into that tight form in one hit,” says Roth, “was beating up our
tools. Using a hot thermal-diffusion coating process on those form
tools took us to 400,000 hits before the abrasive aluminized sheet
would wipe out the corners of the tools. Now we get 600,000 hits using
the CrN coating.”
Summarizing his experience with Phygen
CrN coatings, Roth says, “We started with one set of forms for an
inshot die, back in the fall of 2002, then decided to send all of the
form and cutting tools for that die to Phygen for coating. Now that
we’ve converted one complete die, we’ll continue to send tools there
as they need recoating, about one tool a month, until we convert
nearly every coated tool over.”
Galling Rocker-Arm Stampings
Toledo Technologies, Perrysburg, OH,
makes roller followers, roller rocker arms and rocker-arm stampings.
In April 2003, the firm faced a prototype runoff for a new rocker arm,
of 1008 cold-rolled steel 0.118 to 0.121 in. thick, and found that it
couldn’t produce even 100 parts before galling and cracked stampings
had the firm pulling tools for repolishing and coating, using TiN and
TiCN coatings.
“Running the prototype parts on a set
of single-hit line dies,” says Brian Towns, the firm’s sales manager
for North American automotive, “called for 24,000 stampings, 12,000
each of two arms, intake and exhaust. Then we entered first-year
production in May, using the single-hit line dies. For second- and
third-year production, we’ll build a transfer die and use a portion of
the single-hit tooling, so we had to solve the galling problem. Phygen
did that for us.”
Toledo eventually ran the prototype
contract in five weeks, using the Phygen CrN coating on the rocker-arm
die’s six forming tools (lower-die steels) and on three upper forming
punches. To prepare tools for Phygen, the firm wire- EDMs worn tools,
taking care to obtain “an above-average surface finish using EDM,”
says Larry Webb, production manager and former tool and die maker,
then hand-polishes. Tools average 3 in. thick, 3 in. wide by 6 in.
long. Punches average 5 in. tall, 1 in. wide by 3 in. long. All are of
D2 steel.
An
unexpected byproduct of the switch to Phygen CrN coatings: Toledo
Technologies found it could run the rocker arms using 25 percent
less die lubrication. “On the last 2500 prototype stampings,
knowing how smoothly the process would run,we decided to
experiment with lubrication,” says Scott Smith, manager of
stamping design. “We reduced lubricant supply by 25 percent and
saw no difference in part quality or tool wear.”
The newest of the firm’s rocker-arm
jobs is not the firm’s first experience with the Phygen coating.
Late in 2002 Toledo Technologies decided to try the new coating on
another rocker-arm project, using DC53 tool steel as a replacement
for carbide tools, as the firm struggled to get carbide shipped in
as needed.
“We tried the DC53 uncoated, which
worked pretty good for us,” recalls Dan Mills, manager of product
development, “particularly because we heattreated the DC53 to Rc
63-64, as hard as we could get it.DC53 is a cold-work die steel
popular in Japan and we’ve found it to be very resistant to
galling and to distortion from wire-EDM.
“When we coated the DC53 punches
with Phygen CrN, we wound up with punches comparable to or better
than carbide punches, at half the cost,”Mills continues. “We use
the coated DC53 punch at the most critical station, the one that
forms the socket for the rocker arm, where surface finish of the
part is critical.Using Phygen on DC53, we’ve run as many as
215,000 parts before we lose the required surface finish,while
running a double-coated (TiN and TiCN) carbide tool maxed out at
135,000 parts.” |


An inshot die, top, reveals an array of tool coatings, as
Beckett looks to eventually coat nearly all of its form and
cutting tools with Phygen ST.3 SuperTough. Not only does the
coating maximize hits between sharpenings, but it goes on
colder than other coating processes, says Beckett’s Roth,
avoiding distortion of components such as the form rings used
in water-heater-burner flame-spreader tools, bottom. |
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Reprinted with permission from Metal
Forming Magazine.
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