Press machine tools are used in the stamping process. The die, made of hardened steel, has a contour that matches the shape of the finished part and is mounted on the table of the press.
The punch, made of hardened tool steel or carbide, also matches the contour of the part but is slightly smaller to allow clearance between the die and the punch. It is mounted in the head or RAM, which moves down and punches the metal. The thickness of the sheet metal does not change during this process.
Design and manufacturing of dies and punches is a highly skilled process. Master craftsmen use precision jig boring, grinding, EDM, and lapping machines to produce highly accurate dies. Progressive stamping is used to design complex profiles. In this process, the profile is cut in steps with a series of different sized die and punch combinations.
The first punch in the series cuts a smaller profile and the next punch finely polishes the metal to obtain a desired shape. Tumbling process or deburring is used to remove any sharp edges and burrs. All through the process it is important to maintain a minimum wall thickness for the punched hole.
The metal may be plated with palladium, nickel or tin to protect it from oxidization.
Plating improves the durability and solderability of the product. For additional shelf life, the sheet metal is also pre-plated before the actual stamping process. The product is then cleaned to dispose of excess oils, grease, films or other materials used during the stamping process.
The heating process follows the cleaning process to enhance the toughness of the metal product. In some cases, to ease the stamping process, the sheet metal is subjected to a stress relieving process that removes internal stresses in the sheet and improves its machineablity.
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