A metal stamping process requires a specially designed machine to complete. The machine responsible for this task is called a stamping machine. It is sometimes called a stamping pressing machine, or simply stamping tool. Although it is called a stamping tool, or stamping machine, it can do more than stamping. This type of stamping tool is also used to perform punching, cutting and shaping metal sheets so to speak.
These stamping tools can be controlled in several manners. For example, the CNC (computer numerically control) system enables the stamping machines to offer high precision and repeatability for each stamped piece. The EDM (electrical discharge machining) and CAD (computer-aided design) programs would help with accuracy.
In general, stamping machines work with different dies according to different demands. By their combination, a well-formed stamping product would be complete perfectly. Another machine that would usually be linked with a stamping machine is the feeding machine, as known as the automatic feeder which can feed the metal sheets into the stamping machine safely without human forces. By the methods they are powered, stamping machines can be divided into three groups as the list below:
Metal stamping tools powered by mechanical ways use the motor connected to a mechanical flywheel to transfer and store energy. The punching range would be between 5 to 500 mm, and weight between 20 to 6,000 tons. Their pressing speed could be at least 20 and up to 1,500 per minute, which is still faster than hydraulic ones. Machines of this kind are suitable for manufacturing shallower and simpler parts with large production runs.
Stamping tools in this design stamps the workpieces by pressurized hydraulic fluid. The hydraulic piston would apply the proportional force according to the diameter of the piston head to drive the fluid for pressing. Compared with mechanical designs, the pressure add on workpieces would be more stable because they can be controlled more accurately. Hydraulic presses are mostly used for smaller production runs. Compared to the mechanical designs, they can offer more complicated and deeper stampings. Because of the adjustable stroke length and controlled pressure, they are more flexible.
Mechanical servo presses are driven by high capacity motors instead of using flywheels, and are powered by either a link-assisted drive system or a direct drive system. The whole producing progress can be programmable. Usually, mechanical servo presses are used to produce complex stamping products since they can work faster and provide more complex parts than others can do. Compared with these three types, mechanical servo press is the most expensive one.
Metal stamping is a cold-forming process by using dies and molds to form the metal sheets into the required forms or shapes by proper pressure. In general, steel, stainless steel, and alloys such as aluminum alloys, brass alloys, copper alloys, nickel alloys, etc. are the most used raw materials to apply metal stamping.
Before the start of metal stamping, the stamping professionals would design the tooling first by CAD / CAM engineering technology. The design they draw must be as precise as possible to ensure each punch and bend maintains proper clearance and able to provide products in high quality.
In the very beginning of the stamping progress, the raw material, the metal sheets, would be uncoiled and fed into the stamping machine. Then, the coil feeders would help to cut the metal sheets according to the required length one by one. After that, the metal sheets would be transferred into the stamping machine and progressed station by station until the product is finished. Below are stations that would be included in the stamping progress:
These two are the steps to cut the metal sheets into the required forms. While in the punching step, the stamping machine would press the sheet metals into the dies and modes to form the required shape on the workpieces. Then, the unnecessary parts of the workpieces would be removed in the blanking step.
Embossing is the step to form the workpieces in detail. Through this step, the raised or recessed design would be added onto the metal sheets to make them closer to the finished products. This step would be completed by pressure or passing the material blank through a roller die.
Coining is a kind of bending technique that can stamp the workpieces between a die and the punch or press without spring back effects. It is because that the punch tip would penetrate the metal and results in accurate and repeatable bends which can efficiently reduce the internal stresses in the metal workpiece.
Bending means simply shaping the workpieces into the required shape, such as V-shape, U-shape, etc.
The process of introducing a flare or flange onto a metal workpiece by the use of dies, presses, or specialized flanging machinery is called flanging.
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