Fisher Corporation Boosts Die Life by Ten Times by Using Thermal Diffusion Processby Steve
Chamberlain
Increasing die life from 10,000 hits to 100,000 using a thermal diffusion coating process has helped Fisher Corp. (Troy, MI) dramatically boost stamped part productivity and up time.Fisher Company builds metal components for seats such as recliner mechanisms for the automotive industry that are assembled by a sister company, Fisher Dynamics, (St. Clair Shores, MI). Fisher Company has been in operation over 50 years. Their owners are the grandchildren of the owners of the Fisher Body Corporation that built bodies for General Motor's vehicles and was eventually bought by GM. A vast majority of their parts are stamped from steel that can be up to 0.090" thick and from 1 to 24" in length. Their goal is to get at least 50 strokes per minute from each press with some parts being produced at 30,000 pieces per week. Currently the company uses a number of presses such as a 1200-ton Minster that does progressive stamping, along with 300, 200, 100, and 75-ton presses. To get this type of production speed without crashing a progressive die set was tricky. Tool Room Supervisor Terry Sechler, said, "To get 50 strokes a minute with some of our dies without special surface preparation is just about impossible."
"To get high production from this progressive die set that produced about 30,000 parts per week, we turned to a thermal diffusion process from the TD Center (Columbus, IN). Before this process, we could only get 20 to 30 strokes per minute, not enough to make production. "Four dies in a 14-station, 11' long progressive die set were used to produce inner and outer recliner seat parts on our 1200-ton Minster press. These parts measured 16" long and exited two off. The dies were fed with a 22"-wide coil stock using servo feeders. Running at these speeds and with the complexity of the part, we needed our dies protected. There's only one process that we knew of that could hold up to our production, and that's thermal diffusion from the TD Center." About TD Center / Thermal Diffusion
Sechler said they found out about the thermal diffusion via trial and error. "We were driven to take our presses up to 50 strokes a minute, and in some cases with our smaller presses, even higher than that. We just started calling lubricant and coating companies and seeing what they offered. But TD Center''s solution was the one that worked. It was the one we were looking for, and the only coating process that really works for our difficult applications."
Along with using the TD process, to get up to the needed 50-strokes per minute, Fisher uses chlorinated paraffin lubricant. For other jobs they use different types of lubricant, because the chlorinated paraffin sticks to certain dies that are plated and have special heat-treat processes. Currently, Fisher uses the TD Center process on about 30 dies, the majority of which produce their largest parts.
Other benefits of the TD Center coating include: the reduction or elimination of galling; extension of punch life up to 12 times; a decrease in maintenance; greater part quality; a reduction in scrap rates; elimination of rust on tooling; a reduction or elimination of lubrication in some applications; and a much nicer part surface appearance. |
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TD Center |
For
one job the company started producing in 1998, they purchased a
new press and new tooling, but couldn't get high production for
these parts because of problems with the die set. This component
was a GM pickup truck seat recliner that Fisher made for Fisher
Dynamics. The part had to be wrapped around a tight radius at the
same point where the material, a high-strength steel 0.090"
thick, flanges down. Wrapping the part created a lot of heat especially
in the top area of the die. Heat, combined with the restriction
to material flow, caused the steel to build up on the tool and eventually
gouge it. Coating the top portion of the die prevents heat buildup,
and polishing the bottom die area prevents the part from hanging
up on it. 
The TD Center thermal diffusion process is a hot process (1800°F)
that combines carbon from the tool surface with the element Vanadium
to grow a Vanadium Carbide layer that is 'welded' to the substrate
metallurgically. This method of "Thermally diffusing" a Vanadium
Carbide layer into the surface creates an incredible adhesive bond
far stronger than any deposited coating and better adhesion means
longer life. Because of the high temperature Thermal Diffusion process,
the coating does not chip, peel or spall off the substrate, and
it is extremely durable providing excellent protection from both
adhesive and abrasive wear. TD is a layer of Super Pure, Ultra-Dense
carbide
that completely covers the part, and is bonded below the surface.
The carbide is 0.0002"-0.0003" thick with a hardness of 3200
to 3800 HvU (Vickers Hardness), approximately 90 Rockwell C. Both
dies were micro polished before the layer was applied. For Fisher,
the coating lasted two million hits. It also successfully prevented
heat buildup in the dies.
Sechler
added, "We've been doing business with The TD Center for the
last five or six years. It's a good coating that we use on our most
complex die applications. We use different cold (coating) processes
for other die parts like punches, but on our larger seat-component
dies, we must use the TD process. If we were to run it without
the coating, or even use a cold-process on those dies, they wouldn't
last. We did tests and benchmarked the TD performance. We
even tried other products, but they just fell short of the thermal
diffusion performance. There's nothing out there that I know of
that can beat the TD Center for a hot process."
To
produce die designs, Fisher usually works closely with either their
parent company or other customers. Fisher has in-house engineering
capabilities and they offer complete die production and maintenance.