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Mastering fundamentals opens opportunities for advancement

While technology advances rapidly, a need to understand the basics of how metal is formed remains constant

In manufacturing, as in athletics, understanding fundamentals is the foundation for success.

Barry Larkin, the Cincinnati Reds Hall of Fame shortstop, said it best: “What people don't realize is that professionals are sensational because of the fundamentals.”

Sheet metal professionals must understand the relationships among product design, material properties, and forming processes. Gordon Moore, co-founder of Intel Corp., once said, “The technology at the leading edge changes so rapidly that you have to keep current after you get out of school. I think probably the most important thing is having good fundamentals.” The materials and technologies involved in forming sheet metal components are evolving at an accelerated pace. Your knowledge of the basics and their application makes the difference between success and failure.

The mild steels commonly used 15 to 20 years ago were easily formable and corrosion-resistant, but lacked the strength and weight advantages of today's high-strength steels. New materials, designs, and technologies make today's vehicles much safer for restrained passengers than older vehicles. Also, weight reduction allows automakers to use fuel-efficient, smaller displacement engines to achieve similar performance. Forming components with today's stronger steels and introducing other materials present new challenges in design and manufacturing.

Forming sheet metal components remains an exercise in applying energy to a blank in a die until it attains the desired shape. Understanding the relationships between material properties, blank temperature, energy used for forming, and friction is critical in an environment where new grades of material and new forming technologies are used.

Product Design

Each component in a product has a specific function. The geometry and material used must be able to meet the component's requirements for strength, appearance, function, corrosion resistance, and acceptable worst-case behavior. Automotive skin panels must be dent-resistant, free from visible imperfections, and corrosion-resistant. Appliances must be able to withstand shipping and handling along with normal in-service abuses. Some electronic components must be small and lightweight, yet strong enough to not fail under the load of electrical connectors.

Function, durability, and aesthetics define the geometry and materials needed to form the component.

Material Properties

Each component in a product system must meet its localized requirements while supporting functional and aesthetic requirements for the entire product. The component meets its requirements through its geometry and its physical properties. This requires the selection of appropriate materials that support the component's needs for strength, mass, formability, and corrosion resistance.

Some fundamental properties of a material are:
  • Tensile Properties. Probably the most common test of any material's properties is the uniaxial tensile test. From this test we can determine a material's strength and stiffness. Most important, we can understand the amount of energy required to permanently deform the material, as well as the point where we can expect material failure to begin.

    In their paper “Tensile Testing of Metallic Materials: A Review,” Malcolm S. Loveday, Tom Gray, and Johannes Aegerter stated that “feed-stock metallic materials are subsequently used by the entire engineering manufacturing sector to produce products as diverse as automobiles, white-ware domestic products such as cookers, washing machines and refrigerators, power plant, aerospace products as well as the civil engineering construction industry. Thus, the tensile test may be regarded as one of the fundamental foundation stones on which the whole of the manufacturing sector is based and represents a massive proportion of the European and worldwide economy.”

  • Corrosion Resistance. Mankind has been battling corrosion since the early days of metal production. Today's coatings and material technologies provide superior performance in preventing corrosion in the product's operating environment.
  • Surface Hardness. For aesthetic applications, hardness testing offers a measure of the material's resistance to scratches and dents.
  • Weldability. While all metals are weldable, different alloys and carbon content present complications to the welding process. Welding dissimilar materials also presents challenges. Improper welding techniques can lead to embrittlement in the welding zone.

Forming Processes

The process of forming sheet metal blanks into components includes many variables. These variables are used to manage the condition of the blank, apply energy to the blank, reduce friction, and ensure the formed product retains the desired shape without splitting or wrinkling. At this stage, all the elements of your product design and material selection come together to support a quality product with minimal scrap.

Some of the fundamental items in the forming process are:

  • Forming Temperature. Stronger steels with higher yield strengths are increasingly used in applications requiring lighter-weight and stronger components. Forming these metals introduces new challenges in required press energy and managing springback. Cold forming is still common, but warm forming and hot forming change the properties of the blanks enough to more easily form high-strength components. This creates new challenges in managing furnaces, monitoring transfer times, and establishing proper quench times for the formed component.
  • Die Geometry. The most important component in the forming operation is the die. The die determines what shape the blank will take after energy is applied by the punch. Designing a die demands the designer understand the properties of the metal being formed, anticipated springback, and the behavior of the metal during stretching, bending, and drawing.
  • Press Energy. The amount of press energy you apply to your blank and how you apply that energy is important to product quality as well as for managing your investment in press technologies.
  • Lubrication. The interaction between the punch, die, and the blank creates a tremendous amount of friction that can affect the quality of your finished component. Many alternatives are available to manage friction through lubrication.

The Case for Fundamentals

During periods of technological advancement, your knowledge of fundamentals is your foundation for making correct and profitable decisions. Sheet metal formers must understand how material properties affect process results and how processes impact the properties of finished products. Given this understanding, adopting new technologies and forming new grades of sheet metal become less frustrating and less costly activities.

About the Author
4M Partners LLC

Bill Frahm

President

P.O. Box 71191

Rochester Hills, MI 48307

248-506-5873