Page 46 - MetalForming June 2009

Tooling Technology Copper-Alloy Die Insert
Experiencing a die-insert failure, due to tool-steel galling, after only 7500 hits sends out a call for help dealing with an
automotive-seat stamping of dual-phase steel. To the rescue: a new insert machine machined from a special
hardened copper-alloy casting.
BY BRAD F. KUVIN, EDITOR
When its customer, Johnson Con- trols, Inc. (JCI), could make only 7500 hits before being forced to remove a worn die insert and replace it with a freshly coated insert, Custom Tooling Systems (CTS) went back to the drawing board to find a better—a much better—solution. The Zeeland, MI, tool and die shop had successfully completed a 41-die order for JCI in 2007, valued at $10 million, yet this one die proved tricky. The die, part of a package to stamp all of the seating com- ponents of a 2008 model-year vehicle program, comprises 16 stations to stamp seat-side reinforcements. The challenge: stamping the large part from a 1.5-mm (0.059-in.)-thick dual-phase steel, Docol 800 from Swedish supplier SSAB.
“The first time JCI ran this tool,” shares CTS president John Bouwkamp, “it made 7500 hits before one of the form stations experienced excessive galling. Then, when carbide failed in the application as well, we turned to a spe- cial hardened copper alloy for the die insert, and the progressive die has run for more than eight months now, mak- ing more than 100,000 hits without requiring maintenance.”
TheTroublingStation
Of the 41 dies in the seat-stamping package, four process Docol 800 sheet. For these dies, CTS used D2 rather than A2 tool steel. For the dies not stamping Docol800,trimsteelsareofA2.Yet,even using coated D2, the form tool in the rein- forcement application failed to hold up.
“At that die station, the top surface of the part steps down 3⁄4 in., then gets flanged 90 deg.,” says CTS floor super- visor Tom Runyon. “And, the clearance radius specified created a lot of galling of the coated D2 insert. The radius goes from 0.080 in. and blends out to 0.125 in. Where this extreme flange condi- tion is, it more or less kinks the inside radius to a no-radius condition, or almost square inside.
To stamp this side-seat reinforcement, Custom Tooling Systems developed a 16-station progressive die. The part is of 1.5-mm dual-phase steel, which posed significant tooling challenges, particularly in the area where the top surface steps down 3⁄4 in. and then gets flanged 90 deg. For that chal- lenging form station, CTS machined a tool insert of a hardened copper-alloy casting, and to date the tool has made more than 100,000 hits.
“Forming Docol, we find that you get two hits,” Runyon continues. “The first hit can move a lot of steel. But with the second hit, the material has hardened so much that you can’t really move the steel too much or it will split.”
Where Carbide Fails, Copper Alloy Succeeds
After JCI experienced galling failure after 7500 hits with the die, it asked
44 METALFORMING / JUNE 2009
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