Page 46 - MetalForming June 2013

Tooling Technology
Incremental
Incremental
Forming-Simulation
Forming-Simulation
Software
Software
Back in June 1987, I was tasked with my first formability assign- ment as a second-year appren- tice at the famed UAW/GM Die Engi- neering Apprenticeship Program. We created die layouts on Mylar by using descriptive geometry with dividers, tri- angles and pencils to develop the die face for draw dies. The punch opening and binder surface was just a line drawn by hand—old school.
The two-dimensional die layout was the blueprint to build a three-dimen- sional model of the die face engineer- ing out of plaster. We executed engi- neering changes and what-if analyses with modeling clay and a sculpting knife, and machined tools from the plaster models. Formability analysis occurred for the first time at the tryout press.
Tim Stephens is an advanced manu- facturing engineer for the Johnson Con- trols automotive seating product group. He’s responsible for sheetmetal forma- bility for North America and provides regional simulation support to opera- tions in Asia, South America and Europe.
...is the safety net die shops use when walking what’s become a high-risk high-wire act to design and develop dies for high-strength automotive steel structures. The margin for error is nearly zero.
BY TIM STEPHENS
The automotive stamping world changed when the workhorse SAE 1008-1010 low-carbon-steel family was tossed aside in favor of high-strength low-alloy (HSLA), dual-phase (DP) steels and other materials with tensile strengths exceeding 1000 MPa—I refer to these as super steels—for structural stampings.
Not long ago, wire EDM revolu- tionized the manufacture of die sec- tions, replacing a generation of think- ing that the only way to machine steels was to mill and grind sections. Now there is another revolution under- way—software technology that accu- rately predicts the formability of sheet- metal stampings before any steel is ordered, let alone sent to the wire- EDM machine. This no longer is your
daddy’s die shop.
While automotive product geometry
has not changed much in the last 25 years, stampings now are made from materials with a fraction of the forma- bility characteristics of materials used in the past, all while tooling budgets seemingly have shrunk and continue to do so. The margin for error is nearly zero, and the stamping-die business is a high-risk high-wire act.
Your safety net: Formability-simu- lation software and the ability to predict production sheetmetal formability issues.
One Step vs. Incremental Simulation
I often hear from die shops, “Oh yeah, we did a simulation on that.” Actually,
44 MetalForming/June 2013
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