Texturing

Thermo Pressure Forming's ability to pick up fine surface contours from the die allows it to reproduce sharply defined details such as engraved lettering, figures, and texturing. A good example of Thermo Pressure Forming's ability to faithfully reproduce surface details is the large prismatic lenses for light applications shown in Figure 20 .

Textured surfaces are put on plastic parts to make them look like something they are not. Combining the color of an original sheet with a blending of textured and non-textured surfaces can produce a rich, attractive appearance that rivals the images created by the injection molding process.

The textured patterns on surfaces parallel to the open face (deck) of the die are not troublesome and can be textured to any desired depth. Textured side walls which are nearly perpendicular to the open face of the die are a different matter however. Textured surfaces in these areas represent thousands of small undercuts which tend to lock the part into the die. Shrinkage of the plastic material helps free these undercuts. However, a draft angle of at least 1 degree per side plus 1 degree per side for each .001 of an inch of texture depth is recommended on all outside textured walls (Figure 21) .

Inside surfaces however, do not shrink away from undercuts formed by textured surfaces in the die and these walls must be provided with a draft angle of 5 degrees per side plus 1 degree per side for each .001 inch of texture depth. Even larger draft angles are desirable assuming they do not interfere with function or customer acceptance of the part.