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
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.