Metal stamping and forming is a manufacturing process employed to convert flat metal sheets into specific or desired shapes. In this process, pieces of flat sheet metal called blanks are placed on stamping press that utilizes a tool and die surface to convert the metal into a different shape.
It is a high-speed, low-cost manufacturing process that manufacturers use to produce large volumes of identical parts. Stamping can be applied for both long and short production runs and can be carried out with other metal forming processes.
In this article, we’ll explore the steps and processes involved in stamping, the various types of stamping presses, and the advantages of this fabrication process over others.
Techniques Used in Stamping
The following are several techniques applied in this process:
- Blanking: This is the process of reducing larger coils or sheets of metal into smaller pieces. Usually, blanking is carried out when a stamped piece will be formed.
- Flanging: In this process, a flange or flare is introduced onto a workpiece using a specialized machinery, presses, or dies.
- Punching: This process is effectively employed to create holes in a workpiece.
- Embossing: Embossing is used to create recessed or raised design in a workpiece. It can be done by either passing the sheet through a roller die or by pressing the blank against the die that has the desired shape.
- Bending: Bending is the technique employed in forming metal into the shapes required for manufacturing processes. These shapes could be V, L, or U, or any other shape, depending on the goal in mind. In this process, the piece is stretched beyond its yield point but below its tensile strength.
- Coining: This is a type of bending technique that is used to create accurate and repeatable bends. The workpiece is stamped while it is placed between a press and a die. This technique causes the punch to penetrate deep into the processed part which relieves stress on the piece, helping in eliminating any spring back effect.
Types of Stamping
The type of stamping used in a process depends on the finished product. However, there are four types that are commonly used, and they are hot, precision, progressive, and transfer die metal stamping.
This process involves the use of extreme heat to form metal. Heat temperatures can go up to 17000F as in the case of boron steel. After being heated to that temperature, the steel is quenched in the die, resulting in a lightweight, high-strength steel part. Click here to learn more about lightweight materials.
This method has several advantages but the most notable one is the fact that the stamped part gets an incredible tensile strength that could go up to 200 kilo pounds per square inch (KSI). Other advantages are it allows for the formation of multiple complex parts at once, reducing welding time and other joining processes.
Also, warping and spring back are eliminated in workpieces that are passed through this method. One disadvantage of employing this method, however, is that hardened parts are difficult to cut. This means that post-formation cutting, and trimming becomes a challenge and most time will require powerful laser tool.
This method is used to create three-dimensional pieces with strong tolerance. It typically involves fewer movements of the workpiece between machines, making it a faster process than other types.
The high level of precision used in this method allows for the formation of complex, intricate designs meant to follow specifications to the T. Precision stamping can be used on metals with tolerances between 0.0005 and 0.001 inches for roundness, and 0.001 and 0.002 inches for length. Prototypes, engine parts, telecommunication devices, electronics, and aircraft components are all crafted using this type of stamping.
Also called progressive die stamping, this method takes a workpiece through multiple stages that each carry out a separate action on the piece. The part is attached to a long strip of material throughout the various stages and the finished product is only cut off by the last machine.
This approach is perfect for processes that involve long runs and high volume because the dies last long and there is minimal waste. In forming larger parts that require different presses, this process isn’t the best choice, instead use the transfer die stamping method.
This method is like the one we just discussed. The only difference between the two is that in transfer die, the piece is separated early on from the strip and is transferred from one machine to the next using another transport system, usually a conveyor belt. This method is utilized for larger parts requiring actions from different presses.
Types of Stamping Presses
The three most common types of presses are hydraulic, mechanical, and mechanical servo presses. These presses are usually linked to an automatic feeder that feeds metal sheets through the press.
- Hydraulic Presses: They make use of pressurized hydraulic fluid to apply force on the workpiece.
- Mechanical Presses: In this press, a motor is connected to a flywheel to both transfer and store energy. Punch sizes range from 5mm to 500mm, depending on the press.
- Mechanical Servo: Unlike mechanical presses that use flywheels, this type of press runs on high-capacity motors. Mechanical servos are faster than hydraulic presses and can create even more complicated stampings.
Advantages of Stamping Over Other Forming Processes
There are several benefits that a metal stamping company enjoys that are not accessible to companies using other forming methods.
- Die production costs is lower than the other types of forming processes. This cost reduces even more when ferrous metals are used in the project.
- Once dies are produced, parts can be produced in large volumes and in relatively less time. Production time can still be reduced further by using automation like CNC machining.
- There is hardly any waste with stamping since scraps can be recycled and used in the future.
While stamping appears to be a better option, it may not be suitable for certain types of production metals. Before you adopt this method, it is important that you do due diligence to find out if it is the most appropriate for you.