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The automotive industry's need for textured parts has risen
steadily over the past few years. In response to this need, the
process of mold cavity texturing has evolved -- rapidly.
In the past, the primary concern most mold makers had about texturing
was, most likely, its ability to hide surface imperfections. Now,
however, with exacting quality standards and process manufacturing
philosophies becoming second nature, it has become clear that when
preparing a mold to be textured, the entire process should be
considered to ensure quality.
Competitive Mold Maker spoke with two employees from Midwest Mold and
Texture Corporation to learn more about texturing and, as a result,
see how these processes impact each other. Midwest Mold and Texture
serves some of the leading manufacturers of highly complex molds in
the automotive, electronics and building materials industries.
According to Midwest Mold and Texture's Rick Verkamp and Mervin
Senters, Jr., knowing how surface finishes and texturing are
associated can help mold shops better prepare mold cavities and, in
turn, increase the quality of their textured molds.
"Texturing enhances the value of a molded part cosmetically and
functionally," says Verkamp, assistant general manager of Midwest
Mold and Texture. "It gives a part a more attractive look and, in
some cases does actually help it withstand wear, hide scratches and
provide an easy-to-grip surface depending on the intended use for the
part." Texturing might also be applied on some areas of the mold core
to possibly help solve ejection problems in the molding process.
"From a low glare, matte finish pattern to a more exotic, leather
grain pattern, texture designs are limitless," says Senters,
supervisor of Midwest Mold and Texture's texturing division. And with
each pattern, various specifications must be met to achieve a quality
texture.
"The texture must be applied evenly to a surface without any flaws,"
says Senters. "If you don't begin the process with a good surface
finish," he warns, "scratches from the polishing stone and surface
flaws will most likely appear through the textured finish."
Mold texturing begins with the printing of a texture pattern on
the mold cavity's surface. This is done with photographic films.
After this application, the mold cavity is treated with various
chemicals to harden the texture pattern. Once the pattern is
hardened, the surface of the steel is subjected to corrosive agents
which produce a three-dimensional image design by etching the steel
that is not protected by the hardened image.
"A smooth, uniform finish is important so the texture has an even
depth, free of pockets or other hills and valleys that will cause
problems when creating parts with the mold," says Verkamp.
"Generally, a 400 or higher grit paper better ensures that the
surface finish will be adequate, and the surface will be uniform for
application of the texture."
This is easier said than done when considering some of the more
complex mold cavities. "The cavity can hide some of the flaws due to
its complex shape," says Senters. The mold cavity should be checked
closely for any marks or flaws. If the cavity is outside a tolerance
level for a specific texture, the texturing facility must contact the
mold manufacturer and arrange a rework on the surface finish --
wasting valuable production time and money.
The type of surface finish and texture applied to a mold can be impacted by the following variables:
Some textures can be as shallow as a couple microns. With such a low level of material removal, the surface finish must be of the highest quality to achieve a good texture. A more precise process is required for this texture than when creating a texture with a greater depth and a much higher material removal rate, like leather grain.
Performed incorrectly or not taken into consideration, these variables will impact the mold quality, showing deviation after the chemical etching process or, even worse, affecting the plastic.
With the seemingly endless amount of variables involved in
texturing, Senters recommends working with your texturing facility
for best results. "This interaction allows sharing of expertise,"
says Senters. "Together you can close the gap on certain variables
and create a higher quality part."
Verkamp agrees. "It's best to work with the texturing facility early
in the process," he says. "Understanding design objectives will
enhance success of the total project."
Keep in mind the surface finish tolerance levels for each mold,
adjusting based on texture: more tolerance for deeper textures and
the least tolerance for light, shallow textures. The bottom line is
that the texture is only as good as the mold cavity's finish; there
are very low tolerances for surface imperfections.
"If the surface finish has flaws before the texturing facility gets
the mold, we can't provide the highest quality texture," says
Senters. The balance between production levels and quality in a mold
shop is always tight, but by considering the texturing process in
advance, it becomes clear that an even higher quality mold can be
realized.
Located at the edge of the Clermont County Airport in Batavia Township, a suburb of Cincinnati, Ohio, Midwest Mold and Texture consists of two independent divisions. Combined activities of the Mold Division and the Texture Division involve building, modifying, repairing and texturing molds. The parent company of the Texture Division, Tanazawa Hakkosha, was established in the early 1900s, and is a pioneer and worldwide leader in the etching industry. Tanazawa Hakkosha is a developer of unique processes for producing textures.
