Stamps, Dies and Press Tools

(in Russian, shtamp), in engineering, a tool for imparting a given configuration to a work-piece by means of plastic deformation of metal stock or the division of the stock into sections. Each article requires its own tool, the design of which depends on the type of metal stock (section or sheet stock), the type of machine used (hammer forge or press), the nature of the operations to be performed, and the size of the production run.

When dies are used with forge hammers to shape section stock, the die cavities fill with stock metal during deformation, and the stock acquires the shape and size of the die cavity. The deformation of the metal is accomplished by the relative displacement of the individual working elements of the die. In this case there are two such elements: the upper half of the die, which is attached to the hammer, and the lower half, which is attached to the anvil. A distinction is made between open dies, in which the clearance between the working elements decreases during deformation, and closed dies, in which the clearance is constant. In open dies the metal is partially forced into the clearance during deformation, forming a flash, which is subsequently removed by special trimming dies. Open dies have several impressions, in which the stock is successively deformed to effect a gradual approximation of the shape of the manufactured article. The impressions are sometimes made in separate dies, and the billet is consecutively transferred from one die to the next. A distinction is made between preforming die impressions, which give the stock a preliminary shape that makes it easier to achieve the required final shape of the article, and final impressions.

In order to facilitate removal of the workpiece from the die, the side walls of the cavity are made to slope. The slopes can be made less steep if the dies are designed to incorporate knockouts (die shedders), which forcibly remove the forged articles from the die cavity. In closed impression die forging of articles with complex shapes, the dies are made in several parts with several parting lines to facilitate removal of the forging from the die. Closed dies with two cavities are used, for example, in horizontal forging machines. Dies for sheet stamping and hot stamping of section stock on crank presses consist of many parts mounted on upper and lower plates (the working elements of dies include the punch and matrix in sheet stamping, components to guide the upper plate relative to the lower, guide and locating components for positioning the stock in the die, and attachment components). Dies for cold forging and sheet-metal forming may be designed for a single operation or multiple operations. Dies of the second type are classified as progressive-action dies (the stock is subjected to various operations in different positions in the direction of the feed), and compound-action dies (various operations are performed in a single position). Small-series production calls for the use of simple dies with fewer auxiliary components and dies that are not attached to the machine elements.