Page 30 - MetalForming November 2009

Tooling Technology
Lean Manufacturing
can take positive steps to upgrade tool performance by using more advanced tooling materials, surface coatings or treatments to enhance wear performance.
Upgrade Strategies
Although the common air-hardening grades such as S7, A2, D2 and M2 remain the workhorse tool and die materials, these materials have become commodities and quite generic in nature. The use of larger ingot and heat sizes along with the implementation of other cost-driven measures has nega- tively affected product uniformity and overall quality. This trend has given rise to the development of a number of pro- prietary premium tool-steel grades intended to improve performance in demanding applications.
Manufacturers produce premium tool steels using special melt methods and special compositions, resulting in improved metallurgical microstructures and correspondingly enhanced proper-
ties. Example: The powder-metallurgy (PM)-produced grades, characterized by very uniform and fine grain structure free from the alloy segregation effects inherent in any conventional ingot cast material. Highly alloyed PM grades offer levels of wear resistance previously unattainable, but there also are lower alloy grades that offer good wear resist- ance along with excellent toughness.
Applications where metalformers can benefit by using premium tool steels include: • Long production runs or extended
maintenance intervals;
• Heavy loads or limited lubrication; • Difficult workpiece materials, such
as HSLA steels and AHSS alloys, stain- less steels and coated materials;
• Highly complex dies and tooling.
In addition to upgrading tool mate- rials, tooling engineers can select among numerous options for coatings and sur- face treatments, which can improve tool performance. Examples include PVD thin-film coatings, which have evolved
recently to include a variety of process- es and coating compositions. One note: Take care to ensure that the substrate material is suitable for the coating process selected.
The Bottom Line
Extending lean implementation into the realm of tooling helps stampers begin to take some of the guesswork and “shoot from the hip” tendencies out of what often has been a very empirical art. In the past, metalformers made deci- sions based on the experience and assumptions of toolmakers, and metal- lurgy often was included as a key part of the various apprentice-training pro- grams. However, it seems that much of this has been lost in the shuffle, as much of the focus has shifted to engineering tools such as CAD/CAM software and CNC capabilities. Keep things in prop- er perspective by practicing a lean approach to selection and treatment of your tool steels. MF
28 METALFORMING / NOVEMBER/DECEMBER 2009 write no. 26
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