Multi-material molding is a process
in which two or more materials are added to a mold in order to produce
multi-material objects; that is objects consisting of sections of
differing material composition. Multi-material molding is becoming
increasingly popular in the molding industry due to the functional and
economical advantages of multi-material components over traditional
single material components. For example, some advantages of
multi-material molding include being able to produce components with a
skin/core arrangement, and the ability to selectively control the
relative motion between the differing material sections in molded
components.
There are several individual manufacturing processes which can all be
classified under the broad range of multi-material molding. These
processes, such as co-injection, sandwich, and multi-shot molding all
rely on different principles and produce different types of
multi-material components. These processes can all be further
sub-classified depending on the relation of the finished component to
the mold or molds used to produce it. For example, co-injection
components are all formed using a single mold, whereas multi-shot
molding can use several different molds to produce a single component.
The selection of an optimal process for a given component design is a
complex function of part geometry, size, material selection, and other
factors.
These new molding technologies require many new part and mold design
considerations not applicable to traditional single material molding.
An overview can be found in [Gup04], while [Li04] and [Kum02] outline
algorithms for automated design and manufacture of such multi-material
objects. To further aid this process, two independent yet
complementary models for comparing traditional injection molding and
assembly operations with bi-material rotary platen multi-shot injection
molding can be utilized. The first model uses a cost-based
metric for evaluation and comparison whereas the second model uses a
set
of relevant performance aspects as a basis for comparison.
The models can account for every structural aspect
of single-material (SM) and multi-material (MM) injection molding of
several
real-world products and their associated molds. An example of one such
product is the Dewalt (Black & Decker) saw housing shown
below in Figure 1.
Although multi-material molding was initially rare and mostly limited
to the automotive industry, recently, multi-material molding
technologies are expanding their applicability to consumer products,
electrical devices, medical equipment, leisure items and packaging
components. As the demand for multi-material components increases,
these technologies will continue to expand and improve in order to more
efficiently and economically meet this need.
Sections
