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.
Types of Stamping Operations
progressive die stamping process uses a sequence of stamping stations. A metal coil is fed into a reciprocating stamping press with progressive stamping dies. The die moves with the press, and when the press moves down the die closes to stamp the metal and form the part. When the press moves up, the metal moves horizontally along to the next station. These movements must be precisely aligned as the part is still connected to the metal strip. The final station separates the newly-fabricated part from the rest of the metal. Progressive die stamping is ideal for long runs, because the dies last a long time without becoming damaged, and the process is highly repeatable. Each step in the process performs a different cut, bend, or punching operation on the metal, thus gradually achieving the desired end-product shape and design. It is also a faster process with a limited amount of wasted scrap.
Transfer die stamping is similar to progressive die stamping, but the part is separated from the metal trip early on in the process and is transferred from one stamping station to the next by another mechanical transport system, such as a conveyor belt. This process is usually used on larger parts that may need to be transferred to different presses.
Four-slide stamping is also called multi-slide or four-way stamping. This technique is best-suited for crafting complex components that have numerous bends or twists. It uses four sliding tools, instead of one vertical slide, to shape the workpiece through multiple deformations. Two slides, or rams, strike the workpiece horizontally to shape it, and no dies are used. Multi-slide stamping can also have more than four moving slides.
Four-slide stamping is a very versatile type of stamping, as different tools can be attached to each slide. It also has a relatively low cost, and production is fast.
Fine blanking, also known as fine-edge blanking, is valuable for providing high accuracy and smooth edges. Usually done on a hydraulic or mechanical press, or by a combination of the two, fine blanking operations consist of three distinct movements:
Fine blanking presses operate at higher pressures than those used in conventional stamping operations, hence tools and machinery need to be designed with these higher operating pressures in mind.
The edges that are produced from fine blanking avoid fractures as produced with conventional tooling and surface flatness can exceed that available from other stamping methods. Since it is a cold extrusion technique, fine blanking is a single-step process, reducing the overall costs of fabrication.
Material Considerations
The choice of metal stamping materials used depends on the desired attributes of the finished piece. Stamping is not limited as a fabrication process to just metals - there are numerous metal stamping materials that can be processed through stamping techniques, such as paper, leather, or rubber, but metals are by far the most commonly used.
In general, metals tend to maintain their malleability and ductility after stamping. Those used in precision stamping parts usually range from soft to medium hardness and carry a low coefficient of flow. Some of the customary metals and metal types fabricated through stamping include:
Ferrous metals are commonly used in stamping operations, as their low carbon content means they are among the least expensive options available resulting in low unit production costs.
Several important factors and design considerations need to be addressed when performing sheet metal stamping operations.
Finishing Operations
Post-stamping production operations can include having the stamped product going through deburring, tapping, reaming, and counterboring processes. These allow for the addition of other parts to be added to a stamped piece or for the correction of imperfections in finish or removal of sharp edges that may impact safety.
Deburring involves the removal of shards of cut material that remain on the workpiece after the stamping operation has been completed. Sharp edges may require grinding to remove burrs or may need to be flanged over to produce a smoothed edge and to direct the burred edge to the inside fold where it will not cause injuries or be noticed cosmetically.