August 2025 Volume 7

EQUIPMENT & TECHNOLOGY

F orging die wear isn’t just expected, it’s inevitable. How you deal with it makes all the difference in uptime, part quality, and your bottom line. At Gemini Precision Machining, Inc., we’ve spent decades on shop floors, and we’ve learned this: there’s no one-size fits-all answer to tooling wear. What you need is a smart, tailored strategy that considers the type of wear, the volume of parts, and your die geometry. In this article, we’ll break down the common types of die wear and failure and provide practical tooling and refurbishment strategies that can extend die life and increase efficiency. FORGING DIE WEAR: UNDERSTANDING FAILURES, EXTENDING DIE LIFE By Dan Ullrich and David Mills

die was addressed by rethinking the insert design. A two-piece insert was developed where the floor and plug were one component, and the wall was a second insert. This placed the crack-prone area at the boundary solving the problem with smart design. • When the walls of a die are too thin , the dies can crack. As a rule of thumb, the die wall thickness should be 1.5X the depth of the cavity or more. For round parts with deep die cavities, a shrink-fitted insert may be the solution. A crack can only form if the die is in tension. If you apply compressive stress to the OD of the insert, these cracks can’t initiate.

Understanding Die Wear 1. Thermal Fatigue Thermal fatigue is a classic case of the environment turning against you. During forging, the die heats up rapidly as it's struck repeatedly by red-hot billets. Then it’s suddenly cooled by die lubricant, water spray, or air. This extreme and repeated cycle of expansion and contraction leads to surface cracking. Over time, the die surface begins to resemble alligator skin. Although thermal fatigue is expected, certain die strategies such as using tougher materials or maintaining a consistent die temperature can slow the progression. 2. Erosion Erosion is normal wear; material is gradually being removed from the die face due to friction. Erosion leaves directional lines aligned with the flow of material over the die. These patterns will appear in areas of high material flow, such as plugs and flash land. 3. Cracking Cracks in dies can be a bigger problem and are often more preventable than people think. Cracking has multiple causes: • Trapped gas in the die cavity can build extreme internal pressure, causing cracks. The fix? Venting. Designing in strategic escape paths or using die inserts that double as vents is highly effective. • Stress risers such as tight radii, tool marks, weld defects, or even embossed lettering create concentrated points of stress where cracks tend to initiate. Smoothing these areas and avoiding sharp transitions helps. • Mechanical overload is another culprit, where forging loads exceed the material’s strength. In one real-world example, a crack in the bottom of a

Tooling Approaches That Extend Die Life Insert Tooling

Insert tooling is a modular approach where only the critical working surface of the die, the area that wears the fastest, is removable and replaceable. Inserts are machined to tight tolerances and dropped into a reusable holder block. Inserts can be swapped out when

FIA MAGAZINE | AUGUST 2025 16