Stamping Dies: A Basic Explanation of Metal Stamping
What is Metal Stamping?
Metal stamping is the act of forming, trimming, embossing, flanging, piercing, or restriking a metal blank (usually steel sheet metal). It's strongly associated with the automobile industry, simply because each car has many parts that can be made from steel. Outer car panels, like hoods and fenders, are common examples of parts made using metal stamping processes.
Sheet metal is used to make many different parts, not just those associated with automobiles, of course. But, since most people have seen a car and have a basic understanding of its outer sheet metal parts, most of the references used in this article will refer to stamped metal car panels. Plastic has been substituted for sheet metal in many industries, wherever it's reasonable to do so. Plastic molding is less costly than metal forming, but many automakers will still use steel for parts that simply look better when stamped as metal, or for other concerns such as passenger safety.
The illustration at right shows a round metal blank. The second illustration portrays a finished product, embossed with the likeness of American President George Washington. This was done with a machine that presses, or forms, the metal by applying pressure to it (metals used to make coins are obviously softer than steel, and therefore more ably pressed into shape). This pressure forming is a big part of what metal stamping is. Machines are built to repetitively stamp metals, like coins, in a process known as mass production. The same concept is applied when stamping car parts from sheet metal. There are still machines all over the world, running twenty-four hours a day, that travel up and down as they stamp sheet metal. Such machines are called presses.
Metal Stamping Presses
To better understand the act of stamping metal one need only observe a stamping press in action. A press is made of two main parts, upper and lower. The upper part, or 'ram', uses gravity to fall upon the lower part, or 'base', of the press. A press operator loads a sheet metal blank into the press while the press is in the open position. Today, most factories require the press operator to ensure everything and everybody is clear of the press. Once safety has been considered, the operator simply presses a button and the ram falls (in a controlled fashion, of course) upon the base.
Sheet metal stamping presses act as carriages to carry other machines. Dies are fairly simple machines that fit inside and are fastened to a press. A die has two halves, upper and lower, just like the press. The upper half of the die is mounted to the ram, whereas the lower half is mounted to the lower base, or carriage. Large presses are used over and over for many different projects. But it's the dies inside the press, the machines designed by the product manufacturer, that are unique and costly to design and build.
Metal Stamping Die Use in the Automotive Industry
The processes for stamping outer steel panels like fenders and hoods are involved. It starts with an artist, goes through a modeling process, and then, finally, approval is given and work begins to physically make the part.
The first thing that automakers look at when deciding to develop any outer automobile panel is appearance. Can this part be made from steel without showing any blemishes or uneven lines? Will the metal flow evenly and not leave weak spots in some areas? Following those concerns, they will address cost and determine whether it's financially reasonable to have the parts made. If the part has been conceptualized where it's too complicated, or too costly to make, it might get sent back to the concept people for reevaluation.
When a concept is approved, designers are given a number of dies to create using 3D virtual graphics programs. These programs allow a work in progress to be shown to various developmental managers so they may follow along with the design process.
A large car panel normally requires three or more dies to complete the operations necessary to make it. These machines are designed with cost considerations and safety at the fore. Next, when designs are finished and approved, the actual machines are built. The size of the machines will depend on the presses that will be employed. Some dies can be enormous in size, like a die built for forming a large SUV's hood. Some are also mechanical marvels, accomplishing multiple tasks with each downward stroke of the press it's attached to.