Page 20 - Metalforming Magazine April 2022

StampingTooling:
Die Design, Materials,
Coatings and Setup
BY LOUIS A. KREN, SENIOR EDITOR
Our assembled experts provide overviews of developments in these critical die-related areas.
As newer, stronger part materials inhabit stamping presses, sup- pliers of die-design software, materials and coating technologies have taken heed. Research on these topics, and the resulting technology advancements, offer solutions for form- ing challenges. Shop-floor personnel can supplement these advances by pay- ing close attention during job setups.
Tool Steels for Stronger, Thinner Part Materials
“I remember 20 years ago when the industry started incorporating high- strength, low-alloy stamping material, and that evolved into advanced high- strength steel,” recalls Tom Bell, vice president Americas for Groditz Steel North America, Deer Park, IL. “Now, we hear about 1200-MPa material and higher—steel makers have developed much stronger and much thinner steels.”
Against that backdrop, conventional tool steels such as A2, D2 and S7—the workhorses for a half century—are joined by newer additions such as 8-percent chrome steels and matrix steels, Bell reports. His company, Groditz Steel, supplies these materials as well as diecast-industry materials that offer advantages in hot stamping operations.
“More and more tool designs are calling out the 8-percent chromes and the matrix steels,” he says, “and they
will continue to grow.”
The problem: Quantified data on
the performance of the older tool steels in unique applications, and their newer brethren, can be hard to find.
“It’s kind of like the cart before the horse,” says Bell. “There’s a general mentality to run these dies and tools, and process mechanisms until they fail, and then determine why they failed and produce a fix. There’s a tendency to operate in reactionary mode. I get it: A stamper’s job is to make parts, not be a test lab.”
Many stampers lack the mecha- nisms to effectively track new materials and evaluate their performance—either they don’t have the time to examine the issue closely, or are not recording closely enough when, and in what par- ticular process mode, tooling fails or excessively wears.
Bell cites the Auto/Steel Partnership as taking a lead role in evaluating the effectiveness of tool steels in automo- tive applications, but wishes for avail- ability of more real-word data.
“Before the discussion even starts on use of newer tool materials,” Bell says, “we try to evaluate a metal former’s ability to track, quantify and trace per- formance, failures and process ele- ments within the tool. The most sophis- ticated automotive OEMs will remove a die from the press and scan a detail, then compare the scan-detail dimen- sions with the original detail and deter-
mine where a tool is breaking down. Then they’ll take the data to determine why the detail failed and how they can correct it. At the other end of the spec- trum, a Tier One supplier under tremen- dous time pressure just runs and runs the tooling until a detail breaks, and then installs another until that one breaks. There’s no follow up or aware- ness as to solving the problem.
“Now, in the last 5 to 10 yr.,” Bell adds, “I will say that the industry has improved greatly in problem-solving tool problems. But, there’s still the thought that during die design, ‘if it’s a trim section, let’s use S7; if it’s a form section, let’s use D2; and unless it gives us a headache, we'll keep using it.’”
Innovation in Shearing, Press Building, Hot Stamping
More proactive are material processors tasked with slitting or blanking, according to Bell, who bet- ter identify what materials best per- form in cutoff tools and have imple- mented improvements.
And, with stamping presses provid- ing greater force to deal with the newer super-high-strength materials, forged bolster blocks (Groditz produces such blocks) find increased use as an alter- native to more fragile cast construc- tions in press builds.
Hot stamping represents an area, notes Bell, seeing a rapid evolution in tool-material technology and applica-
18 MetalForming/April 2022
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