Page 50 - MetalForming-Aug-2018-issue

The Science of Forming
Standard Deviation of a Normal Distribution
0.60 0.50 0.40 0.30 0.20 0.10 0.00
160
–3􏰀 =170
280
Average
–1􏰀 +1􏰀 =203 =237
68% of all points are within ±1􏰀 of average
–2􏰀 =187
+2􏰀 =253
95% of all points are within ±2􏰀 of average
180 200 220 240 260 Strength (MPa)
99.7% of all points are within ±3􏰀 of average
+3􏰀 =270
to all readings falling within ±5􏰀 of average (one defect per one-million tests).
Tighter process controls will decrease the standard deviation. There may be valid reasons why your supplier is not implementing all steps to reduce variability when it already can meet the specified tolerances. For example, the alloying-element range in the melt specification likely is wide to enable production of several grades from that one set of chemistries. This allows for production efficiencies and provides for steady-state processing conditions that will improve process quality. Sim- ilarly, adjustments in the annealing temperature cannot be realized instan- taneously in the furnace. Rapid changes bring a greater risk of under- shooting or overshooting the targeted value, leading to a wider property vari- ation in the finished product. MF
Learn about high-strength-steel grades and formability, tool steels and
Fig. 3
coatings, presses and die design, and effective lubricant strategies at PMA’s two-day Stamping Higher-Strength Steels Seminar in Nashville, TN, Sep-
tember 12-13. Visit www.pma.org for details and registration, or contact Mar- ianne Sichi at msichi@pma.org for information. MF
SEPTEMBER 25-26, 2018 | GRAND RAPIDS, MI
Whether you operate, or have yet to purchase, servo-driven presses or other servo-driven line equipment, you’ll benefit from attending the 2018 ServoTechnology Experience.
Key takeaways:
• Learn how servo technology is invading the automotive pressroom, taking on a myriad of challenges, including forming thinner-gauge and higher-strength materials.
Mark Stevens, Project Manager, Center for Automotive Research
• Learn how pressroom technology is impacting the forming capabilities of newer aluminum alloys for automotive applications.This presentation updates attendees on where the use of aluminum in automotive applications is heading, and addresses how servo-based pressroom equipment fits into the picture.
J.P. McGuire, Program R & D and Applications Engineering, Aleris
• Discover how servo-based pressroom equipment helps reduce energy usage, and how to make your existing servo-driven equipment run more efficiently and reliably.
Sponsors:
www.MetalFormingmagazine.com/servo
6363 Oak Tree Blvd. Independence, OH 44131 216/901-8800 www.metalformingmagazine.com www.pma.org
48 MetalForming/August 2018
www.metalformingmagazine.com
Relative Frequency