What is Metal Stamping?
Stamping is a metal forming application where a coil or sheet metal is pressed between a punch and die or multiple dies, forming and or cutting the metal to create a desired shape. This is a cold-forming process, meaning the metal does not need to be heated to be deformed, and the stamping process can occur at room temperature. The pressure needed to permanently deform the material needs to be carefully calculated by considering the type of material and the thickness of the sheet or coil. Thanks to modern developments with metal forming machinery, nearly all metals can be deformed and/or cut using metal stamping press applications, as well as many non-metal materials such as plastics, paper and materials used for sealing, particularly in the food packaging industry.
Metal stamping encompasses these other applications:
One or more of these applications can be combined to create complex shapes to be used in parts across a wide range of industries including automotives, aerospace, medical devices, computers and electronic components, and many more. Metal stamping with press machinery is a highly repeatable process that can create many of the same pieces and parts quickly and efficiently.
Types of Press Stamping
Single Station Stamping:
In single station stamping applications, either a single or combination of stamping processes are completed with one press, equipped with a single die set or compound / combination dies that perform more than one operation. With compound die tooling, separate stamping applications can be applied with the same single press or even within the same stroke.
Multi-station stamping, such as progressive die stamping or transfer die stamping can result in more intricate shapes created in a repeatable, efficient manner. This is typically performed with very large and complex press machinery with automated systems for rolling sheet metal through a series of separate stations or transferring larger pieces to separate machines for each step of the process.
What is Metal Shearing?
Shearing is the process of using a straight-edged punch or blade to cut sheet metal by pressing down with enough force to exceed the shear strength of the material and separate it into two parts. For this process to work without creating imperfections in the material, there must be a slight clearance between the punch and die that is no more than 10% of the material thickness. The force of the punch will first roll the material over the edge, creating what’s called rollover, and then the material will be stretched down through the clearance, creating a depth of burnished material before the shearing force exceeds the shear strength and the material is fractured apart.
The fractured material can be bumpy and coarse and the shearing process often leaves material that’s pushed beyond the sheet thickness, called a burr. Secondary finishing applications can be applied to remove burring and smother the fractured edging. Parts can be moved on for secondary finishing operations to remove the burring, smooth the fractured edge as desired or required.
What is Metal Punching?
Punching occurs when a curved punch or blade is pressed into an angled die at high force, removing a section of material from a sheet, typically of metal by shearing force, as described above. The removed part falls through the die into a scrap pile.
Metal punching is used to create many parts and products across many industries, including automotive, aerospace, medical devices and instruments, computers, electronics, appliances, food packaging, consumer products and much more. Once your punch and die setup is configured, metal punching with press machinery is a quick and highly repeatable process, making it a very cost effective and time efficient way to produce many identical parts.
Blanking uses the same method as punching, with the difference being that the piece removed from the sheet metal is the end part to be collected and used and the remaining sheet metal becomes scrap.
Fine blanking is when this process is modified by compressing the sides of the sheet metal on all sides and using higher force to create a more precise break between the fractured pieces, resulting in less burring and smoother edges before secondary finishing applications are applied.
The punch force required to punch a piece of sheet metal can be estimated from the following equation:
Where t is the sheet metal thickness, L is the total length sheared (perimeter of the shape), and UTS is the ultimate tensile strength of the material.
Air Hydraulics Presses for Stamping, Punching and Shearing:
The Right Press Machinery for Stamping, Shearing and Punching
Pneumatic, hydropneumatic and hydraulic presses can all be used for stamping, shearing and punching applications. The main consideration when determining the press you will need for your operation is force – depending on the material or materials you plan to work with and the greatest thickness your sheet or coil will be, size of the hole you wish to create in the case of punching, you will need a press that has enough force to deform or shear the metal (or other material) consistently. Once this has been determined, then it’s a matter of acquiring the proper tooling.
In many cases, the same press can perform many different operations, depending on the tooling affixed, and it is not always necessary to purchase custom punch and die sets for different shapes and jobs, as they can often be combined as needed. Even if you do find you need to purchase custom tooling for a particular product, a punch and die tooling usually lasts around 500,000 strokes on average, making metal punching with press machinery a cost efficient method for creating many of the same pieces quickly and efficiently after the initial press and tooling investment.