Mold design and precision metal stamping

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Moulds (02)

The mold is a matrix which is specifically designed as a tool in some industrial manufacturing processes such as molding, casting, deep drawing, foaming or sintering: serves to give the final or intermediate form to the workpiece or the material to be processed.

In precision metal stamping, a mold is usually composed of two or more half-shells, ranging to delimit an area of the space with the shape of the piece to be obtained. The production molds are usually made of hardened steel (a thermal process to improve its characteristics), or tempered.

 

Molds of less resistant materials, such as chalk, or silicone resin are used for the production of small series for rapid prototyping. The useful life of a mold can go from a few pieces, or even just one, to thousands million of copies.

 

The molds are made according to the processes of traditional milling or high speed, to reach the shape are used for 7-axis milling machines. For the active parts of the mold are also used as electrical discharge machines (wire or tuff), lathes, grinders.

 

In the precision metal stamping field, the mold must usually be designed without cavities that might restrict the removal of the piece: in particular undercuts are to be avoided, that is, angles of 90° or more, which in fact make the printed indivisible element from the mold.

 

In the design of a mold must pay particular attention to the draft angles: since the creation of the walls perfectly in axis with the extraction movement could give problems in the removal of the finished parts, the walls should never be designed vertical, but must have a slight angle (1 or 2 degrees) to the outside. To exemplify, a cylinder should be converted into a truncated cone in order to be extracted without problems.

 

In the molding of sheet metal the mold is made from a steel block, divided into two parts, one on the base and the other on the movable part of the machine tool, which deform the material to obtain even with subsequent steps (and with molds gradually slightly different) the final shape of the piece industrial.

 

A process of precision metal stamping is known as deep drawing. It is a very difficult task, which must be divided into several steps to prevent the sheets from being stretched excessively and therefore can tear or bring thinning non-uniform.

Angela Melocchi
author Angela Melocchi
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