DUAL
- A dual-extrusion is the combination of two different thermoplastic
materials as a single profile. The materials used for dual-extrusion
must have compatible physical and chemical properties in order
to flow together and create homogeneous or mechanical bonds.
In general,
dual-extrusions consist of a rigid section and a flexible section.
The rigid material holds the shape and provides a structure
for attachment. The flexible material creates a water or dust-tight
seal, a cushion and/or absorbs impact.
A dual-extrusion
can perform the same functions as two individual profiles that
have been assembled. Many dual-extrusions simply snap, push
or press in place.
Although
the basic rules for thermoplastic design apply to dual-extrusions,
there are certain limitations. For example, the minimum wall
thickness of the rigid sections is 0.020 inches. the minimum
thickness for the flexible section is 0.005 inches.
Dimensional
tolerances for dual-extrusions follow the same basic principles
as those for single extrusions.
TRI
- As the name implies, a tri-extrusion is a combination of three
dissimilar materials that are bonded to form a single profile.
Tri-extrusion is usually done with vinyl materials and reflects
one of the following combinations:
One rigid
and two flexible components.
One rigid component and a combination of semi-rigid and flexible
materials.
One rigid and two semi-rigid components.
Flexible or semi-rigid PVC may be used as a protective capping
layer. This layer prevents loss of color or glossiness during
exposure to the sun and weather. The other two parts of this
type of tri-extrusion perform the same functions as the materials
in a dual-extrusion.
With tri-extrusion
a greater range of design choices are available. And in certain
situations, a tri-extrusion is the only way that all of the
perfomance demands can be met.
Several
factors add to the cost of tri-extrusions. These include the
additional materials as well as the complexity of the die and
the manufacturing process. Even so, one tri-extrusion can replace
several individually produced parts so that your assembly costs
are reduced. In the end analysis, you will find it to be a highly
cost-effective part.
