Blanking and punching are two of the oldest yet most important steps in sheet metal fabrication. Blanking is best described as “cutting out” that involves cutting completely through the material. Punching involves raising the material, typically with a defined shape, like a circular or square hole in the sheet. This process is also sometimes referred to as “die cutting.”
Blanking and punching can be used successfully for a variety of fabrication applications, including creating a variety of product shapes, creating precision parts, and even creating a variety of intricate decorative applications. Both processes can be used on a variety of materials, such as steel, aluminum, copper, and various blends of these.
At its simplest, blanking and punching involves placing a material between a punch and a die. The dies, which come in various shapes and sizes, are made from hardened steel with a sharp cutting edge. The punch, which is typically delivered by a machine called a press, is also hardened steel and raised with a defined, sharpened structure. When the material is placed between the two, the punch applies pressure on the top while the die offers counterpressure that forces the punch to break through the material.
The type of blanking or punching is largely dependent on the shape of the die that is used. Round dies are typically used for circular shapes and square punches generally work best for square shapes. Custom dies can be made for more intricate or specific patterns. Because these dies are generally quite costly, when designing a product it is beneficial to consider the die shape to lower costs.
One of the most beneficial aspects of die cutting is that it allows for a great degree of accuracy. When it is conducted with proper equipment, blanking and punching can yield precision parts with a very high degree of repeatability from one piece to another. Conversely, more intricate die shapes can also be used to create complex and detailed designs with clean, sharp edges.
One of the key steps to successful blanking and punching is edge breaking. Edge breaking is the process of raising the material around the punctured area. This is useful for a variety of reasons, from making it easier to remove excess materials from around the punched pattern, to helping promote an even surface with the material. Edge-breaking punches are typically dome-shaped, which helps minimize sharp edges around the punched shape or pattern.
Blanking and punching are very versatile processes, often used in the production of large numbers of small parts, the creation of intricate parts, or the manufacture of decorative designs. Furthermore, both processes can be used on a variety of materials, are relatively accurate when done with proper equipment, and have long tool life. It should come as no surprise that both blanking and punching have proven to be invaluable in the world of metal fabrication.
