Page 51 - MetalForming-Dec-2018-issue

temperature, as well with the lubricant additives active under those conditions. Different tests, such as Draw Bead Sim- ulator, Twist-Compression or Pin-On- Disk, can determine friction. The resultant values differ as the test con- ditions differ. For steels, friction changes based on the galvanized coat- ing. Not surprisingly, a hot-dip galva- nized coating has a different friction than electrogalvanized or galvannealed coating. Since the surface morphology of any one of these coatings can differ between suppliers, friction can vary even within a given coating.
Your choice of material model is a required simulation input. Which one is best? Unfortunately, no one right answer applies to all metals and form- ing conditions. A natural tendency may be to use a model not requiring the entry of many parameters, perhaps one that uses only uniaxial-tensile-test values. While easier, these models are not as accurate.
More accurate models typically require results from tests not common- ly performed. Without the correct data, people may choose values generated from other materials that may not be applicable for your particular product. Also, while tensile-testing procedures are very well-defined, results still differ from lab to lab. The test procedures needed for more complex models are not as rigorously defined as tensile testing, so variability in these tests are much more likely.
Finally, simulations offer a choice of what material properties to include. Some packages automatically vary the properties between low and high val- ues, but if not using such programs, you should manually test the effects of different properties. The inclination may be to run worst-case examples, but it is important that your selection be realistic. Simply inputting low-end properties is not appropriate as our supplier cannot produce a sheetmetal
The Science of Forming
with the lowest yield strength com- bined with lowest elongation and low- est n-value—low yield is associated with high elongation and n-value. While you may not worry about splits on a high-ductility metal, wrinkles are a concern, which, in turn, can restrict metal flow. Most forming simulation programs require r-value as an input. Not only does r-value change with ori- entation relative to the rolling direction, but the magnitude of this change is not consistent between grades. R-value changes with plastic deformation, which means that metal formability changes during the press stroke. Sim- ulation software packages typically do not account for this.
Forming in the virtual press shop is an efficient way to test out variables that you might eventually see in production. Understand the limitations of your virtual press shop, and the impact of the assump- tions made while developing a safe and robust stamping. MF
Spotlight on PMA
tool-and-die communities, and have the opportunity to network with industry peers.
Topics include:
• Avoiding Legal Risks in Labor and Employment Relationships • Navigating the Steel Market
• Best Contracting Practices for Manufacturing and Minefields
to Avoid
• Latest Innovations in High-Speed Stamping
• Cutting and Punching High-Strength Steels and Aluminum. Visit www.pma.org/mstd-conference for complete details and
registration.
Upcoming Calendar of Events
December 5-6, Deep Draw Technology Seminar, Cleveland, OH January 29-30, Metal Stamping and Tool & Die Conference, Nashville, TN
February 12-13, Lubrication Technology for Metalformers, Chicago, IL
February 19-20, Die Maintenance and Troubleshooting Semi- nar, Greenville, SC
Visit www.pma.org or contact PMA at 216/901-8800 or info@pma.org for details about these upcoming events.
New Online Training Resource for the Metalforming Industry
Increase productivity and improve employees’ skills in 2019 with METALFORM EDU, PMA’s new flexible, convenient, low-cost online training resource designed specifically for the metalforming industry.
METALFORM EDU provides companies with access to more than 550 training courses, including industry-related skills in precision measurement, blueprint reading, SPC, CNC, Six Sigma, lean manufacturing, safety and more. The platform also features 32 metalforming-specific courses not offered anywhere else.
For more, visit www.pma.org/metalformedu or contact Erin Riffle at 216/901-8800 or eriffle@pma.org with questions.
Premier Conference for Metal Stamping and Tool & Die
to Be Held in January
Presented by PMA, in association with MetalForming magazine, the 2019 Metal Stamping and Tool & Die Conference will take place January 29-30 in Nashville, TN. Participants will learn from industry-leading professionals in the metal-stamping and
www.metalformingmagazine.com
MetalForming/December 2018 49