Coil processing basics to teach today’s workforce

Jan 10, 2024

A coil cart is used to hold the coil and load it onto the mandrel.

Stamping manufacturers vary in many ways, but they share in the struggle to find skilled labor to fill open manufacturing positions.

Filling and retaining people for these positions can be tough, especially as baby boomers retire from the workforce. Many of the new generation of workers want remote or flexible work schedules, which is difficult when stampers need an on-site operator to run equipment.

The good news is that interest in manufacturing as a career is growing. In the 2019 Leading2Lean Manufacturing Index, 27% of Generation Z and 26% of millennials have considered manufacturing as a potential career versus only 17% of Generation X. The caveat to this good news is that most of them need training in the fundamentals of coil processing.

Much of what is involved in coil processing equipment operation has not changed significantly over the years. Technology upgrades have been evolutionary rather than revolutionary.

Uncoiling, straightening, and feeding material to the press certainly are the mainstays of coil processing. Training starts with becoming familiar with the equipment basics—the reel/uncoiler, straightener, and feeder—componentry, and purpose. Next, trainees learn how to operate the equipment and the processes they perform.

Short, informative videos can be useful for connecting to and teaching the basics of stamping and coil processing to employees and potential employees. Training materials have typically existed only in the form of slides, presentations, and publication articles, but in the age of TikTok and Instagram, videos can supplement them. Videos can resonate with the new generations entering the workforce. "A picture is worth a thousand words" is especially meaningful in manufacturing in which processes can be complex and verbal instructions difficult to understand and remember.

Coil Reel/Uncoiler. The process starts with the uncoiling of material from a coil reel. The coil is loaded either directly onto the mandrel, which is a rotating spindle the coil is placed on for unwinding, or onto a mandrel.

Coil reel machines come in two versions—an unpowered pull-off, or a motorized version. Pull-off reels usually have only a short, fixed-speed threading drive and rely on a power straightener. Alternatively, they can have a set of pinch rolls that pull the material off the coil during an automatic operation. Powered reels are motorized with a loop control for payoff into a slack loop and are generally used in applications that don't require straightening, although they also can be used with a pull-through straightener powered by a feeder at the press. Either style of reel can handle a variety of coil widths and weights.

Containing the Coil. Coiled metal stores energy, similar to how a spring does, so it must be contained during storage with retaining bands. Before removing these metal bands, some other means of coil containment must be in place to prevent clock-springing from occurring. Most coil reels are equipped with hold-down or hold-up arms that contain the outer diameter of the material while the operator removes the retaining bands.

Coil keepers are another device used to contain the coil. They prevent the coil from telescoping. This occurs when the outer coil shifts out of line with the inner coil.

Straightening. The next step of the process is flattening the metal using a straightener. The steel- and aluminum-making processes inherently impart tensions and stresses into the coil. These create slight variations within the coil called crossbow, set, edge wave, buckle, camber, and twist. Typically, the purpose of a straightener in a coil feed line is to prepare the material so that it can pass freely through the die and produce an acceptable part. Straightening is executed by bending the strip around sets of rollers that stretch and compress the upper and lower surfaces alternately. By doing this, they exceed the coil's yield point so that both surfaces end up the same length after springback, which results in flat material.

Straighteners typically are available in models with seven to 11 work rolls. The roll diameters and center distances vary, depending on material thickness and width. Generally, they are equipped with fairly large-diameter, widely spaced rollers.

The growing use of advanced high-strength steels (AHSS) has required changes to straightener designs to effectively flatten these high-tensile materials.

Processing AHSS materials correctly demands a higher number of small rollers with closer spacing than are needed for conventional steels or aluminum. This roll configuration enables the material to be stretched and compressed more effectively. However, the smaller radii and closer spacing require that the straightener be built with stronger construction materials and greater depth penetration into the material.

Feeding. Once the material is straightened, it is fed to the roll feed which delivers the material in precise lengths to a stamping press or shear. Roll feeds are driven by servomotors that allow for precise control of angular position, velocity, and acceleration. The feed must not only move the proper amount of material into the tool, it must position the material correctly into the die—front to back, side to side, and square with the tool. If the material is not positioned correctly, the result is slippage.

The Pilot Release. One of the most important aspects of running a press feed operation is making sure that the pilot release is properly adjusted. Pilot release is the act of momentarily releasing the strip to allow it to be aligned by pilot pins in a progressive or blanking die. It gives stampers the ability to position their part on a strip in a consistent manner. The pilot pins in the die will correct slight misfeeds by pulling the material into final position for forming or blanking. This momentary release helps to relieve built-up stress and binding of the strip through the feed and die caused by misalignment or camber. In addition, it prevents the coil strip from walking as it moves through the die.

Another way to help address the labor issues facing manufacturing is by simplifying the process through software. A lot of coil processing machinery is equipped with software that provides prompts and cues to expedite tasks such as automating line setup. It may help the operator to quickly determine optimal speed, running parameters, and acceleration values for a job. Usually, these values can be saved immediately to the controller's memory for the next time the job is run. By automating repetitive tasks, software can help employees focus on more value-added activities, such as problem-solving and product development.

A learning curve is involved in any job, but it is especially prevalent on the manufacturing floor. Delivering easy-to-digest, accessible content can help shorten the learning curve, supplement traditional employee and customer classroom instruction, or serve as a resource for those who want to learn more about these topics.