Author: Daniel J. Schaeffler, Ph.D. First published in the December 2017 issue of MetalForming Magazine Optimizing sheetmetal flow to form a stamped part requires understanding the interaction between the sheetmetal, surface characteristics and tooling. Consider where we were in the 1970s. Back then, we could choose between seven grades of sheet steel. Most of the steel used on cars did not contain a galvanized coating. Lubrication for many deep-drawn parts consisted of a paste made from animal fat. And the tooling material choices for large stampings? With apologies to Henry Ford, you can have any material you want, as long as it’s D2. If the surface wasn’t up to the desired quality, there was always Bondo and a few more layers of paint. Using just trial-and-error could produce a good part, given that there were a limited number of variables to master and that a threshold for “sufficient quality” took less effort. This sounds like ancient history. But is it? Almost half of all tool-and-die workers today are more than 55 years old. When they entered the field in the mid-1980s, they apprenticed under journeymen who learned the trade in the 1970s or earlier. Ideally, these workers now have 30 years of good experience. Unfortunately, some of them may very well have 1 year of experience 30 times over, repeating the lessons learned from their teachers. Today’s metalforming industry looks quite a bit different than the simpler times of the 1970s. We now can choose from more than 200 grades of sheet steel for automotive applications, ranging from one-half to 10 times the strength of the steels available four decades ago. Today, engineers can engineer properties of materials to meet the requirements of specific applications, moving away from commodity sheet metals. Zinc-coated steels for corrosion resistance are commonplace—with some automakers choosing soft pure zinc (either hot-dip galvanized or electrogalvanized) and others using a much harder zinc-iron alloy known as galvanneal. New aluminum alloys refined over the last decade are making significant inroads in more mass-market applications, with most suppliers bringing new capacity onstream. Class A panels for exposed applications made from these steel or aluminum alloys must exhibit consistent surface quality such that just 100 microns of paint (half of that being clearcoat) is sufficient. The choice of tooling material, with coatings and inserts as necessary, is made based on the sheetmetal, intended application and part volume. Lubricants with additives are engineered based on the contact pressures and temperatures encountered during stamping. Productivity increases and the ability to stamp difficult to form grades help justify the purchase of new servo presses. Basic Principles of Sheetmetal Forming Even with these advances, basic principles still apply. Fundamentally, sheetmetal forming involves applying energy to a flat metallic piece to deform it into the desired shape. The energy to make stamped parts transfers from a punch, where the top surface features a contour that mirrors the targeted profile. That energy transfer is a function of how the workpiece responds to deformation, the path the sheetmetal follows in reaching that desired part shape, and the interfaces between the punch and sheet as well as between the sheet and the rest of the tooling. If the energy applied to the forming system to stamp a part surpasses the amount that the forming system can handle, a split will form in the part. When this occurs, either the energy requirements in part forming must be lowered or forming-system capability must be increased. This is where the interface interaction of lubrication, tooling surfaces and radii, and sheetmetal properties all come into play. We must account for the variability inherent within the forming system. The specifications to which sheetmetals are ordered allow for a range of properties deemed to influence forming. A coil may measure more than a mile long, but we assume that mill certs taken on one sample from the coil end represent the entire batch. When we run a part and some of the stampings split, our first instinct may be to say that the sheetmetal changed, when in reality change occurred elsewhere in the forming system where we hadn’t measured—think of the unused tonnage monitors sitting in the corner of the plant. A better job of collecting meaningful information and analyzing the impact of these measurements on manufacturing results yields better anticipation and improved management of our processes, and, ultimately, greater efficiency and improved results. Moving From Trial-and-Error To a Science and Engineering Approach With so many variables present in today’s forming system, the metalforming industry must move from trial-and-error to a science and engineering approach. Experience remains vital, but we must recognize when to incorporate new information into the problem-solving process. The industry has made great progress via computer forming and structural simulation. The ease of use of these programs masks their complexity and caveats. But, deviations from reality can occur in many places, from a material model not matched to the sheetmetal grade, to the assumption that friction is uniform throughout the stamping. Furthermore, what metal properties should we add to the model? We must account for the full range of potential properties for a given grade. Sometimes new information isn’t necessary. We can benefit from looking at what we already have, just from a new perspective. For almost 20 years, Dr. Stuart Keeler has shared his knowledge and experience with the readers of MetalForming and the Precision Metalforming Association ’s conference attendees. He transformed the sheetmetal forming industry by enabling them to understand why the sheetmetal behaved predictably. He also showed them how to utilize this knowledge to produce a superior product, rather than just knowing how a part is formed. With Dr. Keeler’s retirement, I’m attempting to follow his path, and I can only hope to make a similar impact on our community. I look forward to sharing my perspective with you, and look forward to your comments, questions, critiques and criticisms .

FAQs Archive · Page 3 of 3 · Engineering Quality Solutions

May 28, 2018 3:09 pm

The Aluminum and Steel Battle in Automotive Applications

By Danny Schaeffler|2023-04-14T15:10:33-04:00May 28, 2018|Published Articles|0 Comments

Author: Daniel J. Schaeffler, Ph.D. First published in the May 2018 issue of MetalForming Magazine The aluminum and steel industries continuously battle for supremacy in becoming the metal of choice in automotive body construction. This makes sense—with about 2 tons of sheetmetal purchased for each of the 17-million vehicles sold annually in the United States, there isn’t another industry that offers such high-volume sales opportunities. Each metal grade provides critical [...]

Apr 1, 2018 4:54 pm

Know Your Sheetmetal—Aluminum-Alloy Terminology

By Danny Schaeffler|2023-04-09T07:00:48-04:00Apr 1, 2018|Published Articles|0 Comments

Author: Daniel J. Schaeffler, Ph.D. First published in the April 2018 issue of MetalForming Magazine Aluminum alloys are categorized by a four-digit code. The first digit indicates the main element or elements alloyed with aluminum to produce the specific grade. Products with the same first digit are said to be in the same series or family, described by a number followed by three zeroes or “X”s, such as 5000-series or [...]

Mar 1, 2018 4:39 pm

Know Your Sheetmetal Terminology—Part 2

By Danny Schaeffler|2023-04-09T07:00:48-04:00Mar 1, 2018|Published Articles|0 Comments

Author: Daniel J. Schaeffler, Ph.D. First published in the March 2018 issue of MetalForming Magazine Sheet mills produce steel grades to the requirements outlined in specifications. These typically are issued by the end user, national/international bodies such as ISO or ASTM, or industry organizations such as SAE or the Aluminum Association. These documents contain grade-by-grade requirements for tensile and ductility levels, flatness and width tolerances, and chemistry ranges. Consider [...]

Feb 1, 2018 6:00 pm

Know Your Sheetmetal Terminology—Part 1

By Danny Schaeffler|2023-04-09T07:00:49-04:00Feb 1, 2018|Published Articles|0 Comments

Author: Daniel J. Schaeffler, Ph.D. First published in the February 2018 issue of MetalForming Magazine “I need some cold-rolled for this part!” “Get me some 1008/ 1010!” You might think that you know what you’re asking for, but when talking with your supplier, it’s important that you both use the same language to be sure you’ll get what you need. Sheetmetal Sheetmetal is simply any metal alloy that stores as [...]

Jan 1, 2018 4:38 pm

See The Future By Exploring The Past

By Danny Schaeffler|2023-04-09T07:00:49-04:00Jan 1, 2018|Published Articles|0 Comments

Author: Daniel J. Schaeffler, Ph.D. First published in the January 2018 issue of MetalForming Magazine Even though both organizations are automotive-focused, FMEA and other quality tools should be applied to companies of all sizes and industries as an effective way to improve first-pass quality and reduce costs. Dimensional variability. Random splits. Surface waves. Any or all of these can cause big production headaches. Scrambling to fix the problems can lead [...]

Dec 1, 2017 5:50 pm

The More You Know

By Danny Schaeffler|2023-04-09T07:00:49-04:00Dec 1, 2017|Published Articles|0 Comments

Author: Daniel J. Schaeffler, Ph.D. First published in the December 2017 issue of MetalForming Magazine Optimizing sheetmetal flow to form a stamped part requires understanding the interaction between the sheetmetal, surface characteristics and tooling. Consider where we were in the 1970s. Back then, we could choose between seven grades of sheet steel. Most of the steel used on cars did not contain a galvanized coating. Lubrication for many deep-drawn parts [...]