All mold part drawings must show the required finish specifications and any additional finishing requests such as sand blasting, vapor honing, buffing, etc. Table 4-3 lists many industry
finishes and their related manufacturing methods and typical applications.
Even where only one or just a few areas require finishing specifications, symbols and notes
are used to indicate the finish, rather than placing written specifications directly on the affected
surface. It also may be necessary to show limits for a finished area.
If the mold part has several areas that require finishing specs, each surface to be finished will
require a symbol pointing at it. The shape of symbols is left to the designer, and the meaning of
each symbol must be explained in notes. There isno standard meaning attached to these symbols. Each must be explained every time it is used on adrawing. Other shapes may also he used, as long as it becomes clear to which surface they apply.
Textures such as basket weave, leather grain, etc., are usually produced by suppliers
specializing in texturing, which is a chemical etching process involving the removal of material
from the surface on which the texture is applied. The texture itself is defined by referring to
sample chips, identified by names and / or numbers. Unless it is obvious, the designer must
specify the area limits of the texture and show the depth of the texture from the surface to which it
If not properly indicated on the product drawing, Fig. 4-22 shows clearly what can happen. In
Fig. 4-22a), the height h of the product includes the texture; in Fig. 4-11b), the texture is added to
the height h. Since the depth of textures is usually 0.05~0.10 mm, or even more, an error in
specifying the depth of the etching may affect the product height and appearance significantly, and
may lead to scrapping of the mold part .
Note that the etching process starts from the surface of the mold part and sinks into the steel.
This depth d must be specified. It can be shown with dimension lines, as shown in Figure 16-4, or
with a note next to the texture specification.
1. EDM texturing
For texturing, or any other pattern that can be machined into the electrode with EDM, the
electrode requires the finish as specified for the molding surface. During the EDM process, the
electrode is then sunk into the often already hardened mold steel.
2. EDM finish
This finish is produced by a smooth electrode approaching a work piece with a matching
smooth surface. The finish is produced uniformly over the whole area touched by the electrode.
The grain of the finish is controlled by the intensity of the current used. To specify and check the
finish, comparison chips issued by VDI (a German engineering organization) are used as shown in
Fig. 4-23. This is a subjective method of specifying and inspecting, but it is satisfactory for most
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