A new process open up new possibilities for mold designer

A good mold not only has a beautiful but delicate semblance. We all know that there are more or less etchings on surface. Then what should we do can remove them?

The previous，mostly mechanical and predominantly manual, procedures often did not allow imaginative designs. Only the chemical process has opened up new possibilities for the designer.

The basis of this process is the solubility of metals in acids, bases and salt solutions. Metallic materials dissolve as a result of potential differences between microregions of the material or between material and etching agent (Figure 2.27). The metal atoms emit electrons and are discharged as ions from the metal lattice. The free ions are used up by reducing processes with cautions and anions present in the etching agent. The removed metal combines with anions to form an insoluble metal salt, which has to be removed from the etching agent by filtering or centrifuging.

The exact composition of the etching agent is generally a trade secret of the developer. Almost all steels, without restriction on the amount of alloying elements such as nickel or chromium (including stainless steel), can be chemically machined or textured Besides lathe machine molds, those made of nonferrous metals can also be chemically treated. Particularly recommended are the tool steels listed below.

The depth of heat treatment should always be greater than the depth of etching. If this is not the case, (he heat-treated layer may be penetrated. This would result in very irregular etching. Adequate layers are obtained by a preceding case hardening, as already mentioned, the initial roughness of the mold plays an important role as regards the surface finish after etching. Non-permissible traces from machining are not covered up but remain hazily visible. Before etching, the surface should be well planed with an abrasive of grain size 240. The permissible depth of etching depends on the injection molding processing conditions.