Metal stamping includes a variety of sheet-metal forming manufacturing processes, such as punching using a machine press or stamping press, blanking, embossing, bending, flanging, and coining. This could be a single stage operation where every stroke of the press produce the desired form on the sheet metal part, or could occur through a series of stages. The process is usually carried out on sheet metal, but can also be used on other materials, such as polystyrene.
Blanking and piercing are shearing processes in which a punch and die are used. The tooling and processes are the same between the two, only the terminology is different. In blanking the punched out piece is used and called a blank; in piercing the punched out piece is scrap.
Bending is a manufacturing process that produces a V-shape, U-shape, or channel shape along a straight axis in ductile materials, most commonly sheet metal. Commonly used equipment include box and pan brakes, brake presses, and other specialized machine presses. Typical products that are made like this are boxes such as electrical enclosures and rectangular ductwork.
A roll bender is a mechanical jig having three rollers used to form a metal bar into a circular arc. The rollers freely rotate about three parallel axes, which are arranged with uniform horizontal spacing. The two outer rollers have the same fixed vertical height and make contact with the underside of the bar to be formed. The middle roller has an adjustable height and makes contact with the topside of the bar. The bar to be shaped is assumed to have a uniform cross-section, but not necessarily rectangular, as long as there are no overhanging contours, i.e. positive draft. Such bars are often formed by extrusion. The bar is suspended between the rollers. The end rollers support the bottomside of the bar and have a matching contour (inverse shape) to it. so to maintain the cross-sectional shape. Likewise, the middle roller is forced against the topside of the bar and has a matching contour to it.
Drawing is a metalworking process which uses tensile forces to stretch metal. It is broken up into two types: sheet metal drawing and wire, bar, and tube drawing. The specific definition for sheet metal drawing is that it involves plastic deformation over a curved axis For wire, bar, and tube drawing the starting stock is drawn through a die to reduce its diameter and increase its length. Drawing is usually done at room temperature, thus classified a cold working process, however it may be performed at elevated temperatures to hot work large wires, rods or hollow sections in order to reduce forces. Sheet metal drawing becomes deep drawing when the workpiece is drawing longer than its diameter. It is common that the workpiece is also processed using other forming processes, such as piercing, ironing, necking, rolling, and beading. The success of forming is in relation to two things, the flow and stretch of material. As a die forms a shape from a flat sheet of metal, there is a need for the material to move into the shape of the die. The flow of material is controlled through pressure applied to the blank and lubrication applied to the die or the blank. If the form moves too easily, wrinkles will occur in the part. To correct this, more pressure or less lubrication is applied to the blank to limit the flow of material and cause the material to stretch or thin. If too much pressure is applied, the part will become too thin and break. Drawing metal is the science of finding the correct balance between wrinkles and breaking to achieve a successful part.
Coining is a form of precision stamping in which a workpiece is subjected to a sufficiently high stress to induce plastic flow on the surface of the material. A beneficial feature is that in some metals. the plastic flow reduces surface grains size, work hardening the surface, while the material deeper in the part retains its toughness and ductility. The term comes from the initial use of the process: manufacturing of coins. Coining is used to manufacture parts for all industries and is commonly used when high relief or very fine features are required. For example, it is used to produce money (coins), medals, badges, buttons, precision-energy springs and precision parts with small or polished surface features. Coining is a cold working process (similar to forging which takes place at elevated temperature) that uses a great deal of force to plastically deform a workpiece, so it conforms to a die. Coining can be done using a gear driven press, a mechanical press, or more commonly, a hydraulically actuated press. Coining typically requires higher tonnage presses than stamping, because the work piece is plastically deformed and not actually cut, as in some other forms of stamping
Progressive stamping is a metalworking method that can encompass punching, coining, bending and several other ways of modifying metal raw material, combined with an automatic feeding system. The feeding system pushes a strip of metal (as it unrolls from a coil) through all of the stations of a progressive stamping die. Each station performs one or more operations until a finished part is made. The final station is a cutoff operation, which separates the finished part from the carrying web. The carrying web, along with metal that is punched away in previous operations, is treated as scrap metal. The progressive stamping die is placed into a reciprocating stamping press. As the press moves up, the top die moves with it, which allows the material to feed. When the press moves down, the die closes and performs the stamping operation. With each stroke of the press, a completed part is removed from the die. Since additional work is done in each “station” of the die, it is important that the strip be advanced very precisely so that it aligns within a few thousandths of an inch as it moves from station to station. Bullet shaped or conical “pilots” enter previously pierced round holes in the strip to assure this alignment since the feeding mechanism usually cannot provide the necessary precision in feed length. The dies are usually made of tool steel to withstand the high shock loading involved, retain the necessary sharp cutting edge, and resist the abrasive forces involved.
Metal spinning, also known as spin forming or spinning, is a metalworking process by which a disc or tube of metal is rotated at high speed and formed into an axially symmetric part. Spinning can be performed by hand or by a CNC lathe. Metal spinning ranges from an artisans specialty to the most advantageous way to form round metal parts for commercial applications. Artisans use the process to produce architectural detail, specialty lighting, decorative household goods and urns. Commercial applications include rocket nose cones, cookware, gas cylinders, brass instrument bells, and public waste receptacles. Virtually any ductile metal may be formed, from aluminum or stainless steel, to high-strength, high-temperature alloys. The diameter and depth of formed parts are limited only by the size of the equipment available