Page 64 - Injection Molding Advanced Troubleshooting Guide

6 Mold Texture and Polish

„ „6.1„ Mold Texture

There are a wide variety of texture patterns available for molds to provide many
unique looks. The basic idea behind a texture is to change the appearance of the
part beyond just a plain flat plastic surface. It is important to understand the im-
pact of texture on the finished part because texture may improve part appearance
but may also cause additional problems such as sticking and drag marks.

The steel surface finish and texture will affect gloss, cosmetics on the part, and
part sticking issues. It is also plastic-material specific regarding cosmetics or stick-
ing issues; what works for one material may not work for another. The common
reaction to a part sticking issue is to shine up the cavity surface, although on
smooth surfaces with some materials this will have a negative impact.

So what exactly on a microscopic level affects gloss on the plastic part? It comes
down to the geometry and depth of the texture and the surface finish of the tex-
ture/steel itself via polishing or blast media. To understand exactly how this works
we will need to go under the microscope where the naked eye cannot see.
We mentioned two things that affect the gloss: the geometry, and the surface fin-
ish. And remember we are molding the plastic to the steel so the color of the tool
steel has absolutely nothing to do with gloss. The steel can appear to have a
different color when polished or roughed up but it is the surface finish and how it
reflects light that changes the color appearance; for example, Figure 6.1 shows
various gloss levels on the same piece of steel. The color of the steel appears to
vary but the color is actually the same; it is how the various surface finishes reflect
light differently that affects this [1].