Page 31 - 3D Metal Printing Summer 2019

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by MetalForming, 3D Metal Printing’s sister publication. Here’s a look at the tooling side, courtesy of Tom Bell, executive director of Hitachi Metals, and Dr. Harald Lempke, chief commercial officer for Formetrix.
Tooling Solutions Evolve to Keep Pace
To say that hot stamping taxes tooling is quite the under- statement, and material providers as well as tool designers and builders are striving to meet the challenge.
“For hot stamping, we’ve seen an evolution of tool steel stan- dard grades such as H13 and lower-alloyed steels, with all of that pushed upstream to higher-alloyed materials due to critical die expectations related to cycle time and wear,” says Hitachi Metals’ Bell.
Any material with yield strength surpassing 1200 MPa is con- sidered for hot stamped parts, he notes, which truly stresses tooling. Tool-material providers are well aware of the challenges, and are working to meet the needs.
“The challenge in the tool steel business: meeting wear and toughness requirements simultaneously,” Bell says. “But meeting these properties makes the tool steel difficult to work with— more difficult to machine.”
Machining difficulty becomes extra challenging for hot stamp- ing tooling, given the cooling channels and complex forms inher- ent in dies used in this process.
“The expanding requirements related to hot stamping keep us innovating,” Bell says.
He points to two technologies that have a role to play in tool material selection and die design/build for hot stamping: surface coatings and AM.
“As a steel maker, we want to make the best possible steel, meaning the best substrate and the best mechanical properties,” Bell says. “Surface coatings can help in terms of lubricity and wear, and we’re seeing development of coatings that can with- stand hot stamping.”
As for AM, “3D printed inserts enable the creation of effective conformal cooling lines in hot stamping dies,” Bell says. “Tradi- tionally, a water line in a hot stamping die runs along the X or Y axis—very linear. It doesn't always reach the surface of the die contour to cool as quickly as needed. AM inserts can be built to do that, which provides a big advantage.”
What remains to be seen, according to Bell, is whether AM technology can enable manufacture of inserts large enough to be effective in the very large hot stamping dies.
AM-Specific Tool Steel Boasts Simplified Printing
From production-line components to the manufacturing process itself, the metal forming industry continues to respond to the unique requirements of hot stamping and encourages the use of AM as a viable production option for mission-critical hot stamping tooling parts. As hot stamping is conducted on
3DMPmag.com