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Coil Processing and Leveling For Sheets


Manufacturers know that optimizing the production process goes much deeper than just choosing the right alloy. While extremely important, a lot more goes into developing a product that is both high quality and cost competitive. How you work with your materials and what quality control measures you employ are equally critical.

That’s why when you are working with a product such as aluminum (or stainless steel) coil, not only do you need to carefully evaluate what grade or alloy will best serve your application, but you want to know that the processing and leveling that go into the production of your coil meets the high standards you require.

What is Aluminum and Stainless Steel Coil?

Sheet metal is formed through an industrial process that flattens materials such as aluminum and stainless steel, as well as many other metals, into extremely thin pieces. One of the many advantages of sheet metal is that it can be cut and bent into a wide variety of shapes.

Sheet metal is defined by its thickness, which can vary significantly as required. Sheet that is extremely thin, less than .2 mm in thickness, is known as either foil or leaf. Sheet that is thicker than 6 mm (0.25 in) is referred to as plate. Sheet is therefore in the thickness range in between foil and plate.

The United States is unique in the way it measures sheet metal thickness. The rest of the world uses millimeters. Because we are not on the metric system, we still use the traditional, non-linear measurement known as gauge. In what may at first seem counterintuitive, the larger the gauge number, the thinner the metal actually is. For instance, steel sheet metal generally ranges from 30 gauge (thinner) to about 7 gauge (thicker).

When using gauge to measure sheet metal, keep in mind there are different measuring systems for ferrous (iron based) metals and nonferrous metals such as aluminum. Therefore, the gauge for aluminum will not correspond to the gauge for stainless steel.

While sheet metal can be purchased as individual flat pieces, for greater lengths, it is coiled into long rolled strips. Coils are generally formed in a process that involves running a continuous metal sheet through a roll slitter. For ideal results, sheet metal must maintain a uniform thickness and so the processing is very important.

 How does aluminum and stainless steel coil get processed?

In order to produce metal sheet, manufacturers use a process of metal cutting known as slitting. This involves employing extremely sharp rotary blades to create rolls, known as coils, of sheet metal stock. Straight lines are cut lengthwise into the large coil to create strips of metal of the desired width. The coil runs through the slitter as circular blades, commonly referred to as knives with one above and one below, make the cuts. The knives are adjusted to different aperture sizes to control the width of the metal strips.

When it comes to metal fabrication machines, slitters will generally be equipped with multiple knives so that a great deal of precision is manageable. The slitting process has the ability to cut sheets that are relatively thin, in the 0.001 to 0.125 inch range. It works with both steel and aluminum, as well as with other nonferrous metals. Precision is important when working with coil because it’s critical that the measurements remain consistent over the entire length of the coil. Therefore, a high quality production cutter is necessary to control the metal width.

The design and configuration of the knives used for cutting the sheet would normally depend on three criteria:

 The thickness of the work piece

  • The type of material involved
  • The desired tolerances of the finished coil or sheet

 In addition to slitting, modern machines that produce sheet usually can shear the metal as well. This refers to making cuts across the width of the coil.

How do metal workers ensure flatness with sheet and coil?

In order to make sure that you have consistently flat material over the length of the coil, it is necessary to employ roller leveling technology. One way of doing this is to add tension to the leveling process. The advantages of this method include extending the lower capacity range, producing greater material stability, and increasing the possible flatness tolerances.

The way a roller leveler works is that the material is bent up and down in alternating sequence, which stretches the outside and compresses the inside during each bend. That means that on the first bend, the bottom is stretched while the top is compressed. Then, on the second bend, the opposite occurs, with the bottom being compressed and the top being stretched. As the process continues, the middle region is never elongated or compressed past its yield point. 

Another alternative is to employ leveling in the slitting lines. There is also the option of non-conventional methods, such as leveling with a tension assist of each individual strand after slitting and prior to recoiling.

Whatever process you choose, make sure that you are working with a trusted processor who uses advanced methods and adheres to all suggested standards in order to ensure that your sheet or coil is of the highest quality.

What industries work with aluminum and stainless steel coil?

Many everyday objects are fabricated from sheet metal. As an example, grade 3003-H14 aluminum, with its high strength and formability and low cost, is frequently used in mailboxes, cabinets, tanks, and fan blades. Grade 5052-H32 aluminum is commonly used in electronic chassis, tanks, and pressure vessels. Grade 6061-T6 aluminum is found in many modern aircraft structures.


No matter what your application, make sure that your aluminum or stainless steel coil meets the highest standards for flatness and consistency. At Clinton Aluminum and Stainless Steel, our technical professionals pride themselves on being more than just material providers. We strive to be true partners to our clients, working with them at every step of the production process to ensure their success.

If you have any questions about our many offerings, please contact us today.

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