Metal stamping is a cold-forming process that makes use of dies and stamping presses to transform sheet metal into different shapes. Pieces of flat sheet metal, typically referred to as blanks, is fed into a sheet metal stamping press that uses a tool and die surface to form the metal into a new shape. Production facilities and metal fabricators offering stamping services will place the material to be stamped between die sections, where the use of pressure will shape and shear the material into the desired final shape for the product or component.
This article describes the metal stamping process and steps, presents the types of stamping presses typically employed, looks at the advantages of stamping parts compared to other fabrication processes, and explains the different types of stamping operations and their applications.
Punching and blanking refer to the use of a die to cut the material into specific forms, such as pole line hardware. In punching operations, a scrap piece of material is removed as the punch enters the die, effectively leaving a hole in the workpiece. Blanking, on the other hand, removes a workpiece from the primary material, making that removed component the desired workpiece or blank.
Coining is a bending technique wherein the workpiece is stamped while placed between a die and the punch or press, such as sheet metal fabrication. This action causes the punch tip to penetrate the metal and results in accurate, repeatable bends. The deep penetration also relieves internal stresses in the metal workpiece, resulting in no spring back effects.
Metal stamping machines may do more than just stamping; they can cast, punch, cut and shape metal sheets. Machines can be programmed or computer numerically controlled (CNC) to offer high precision and repeatability for each stamped piece, and this technology is widely used in furniture hardware. Electrical discharge machining (EDM) and computer-aided design (CAD) programs ensure accuracy. Various tooling machines for the dies used in the stampings are available. Progressive, forming, compound, and carbide tooling perform specific stamping needs. Progressive dies can be used to create multiple pieces on a single piece simultaneously.
Four-slide stamping is a very versatile type of stamping, such as in electronics hardware, as different tools can be attached to each slide. It also has a relatively low cost, and production is fast.
Hydraulic presses use pressurized hydraulic fluid to apply force to the material, such as in agricultural machinery parts. Hydraulic pistons displace fluid with a force level proportional to the diameter of the piston head, allowing for an advanced degree of control over the amount of pressure, and a more consistent pressure than a mechanical press. Additionally, they feature adjustable stroke and speed capabilities, and can typically deliver full power during any point in the stroke. These presses usually vary in size from twenty to 10,000 tons and offer stroke sizes from about 10mm to 800mm.
Hydraulic presses are usually used for smaller production runs to create more complicated and deeper stampings than mechanical presses, such as car spare parts. They allow for more flexibility because of the adjustable stroke length and controlled pressure.