Engel Combimelt
Engel Combimelt technology embraces all the various types of injection molding processes for the production of composite parts from thermoplastics, elastomers and thermosets. Virtually any size Engel Injection Molding machine, from our 28 ton Victory to our 6000 Ton Duo injection Molding machine can be equipped with multiple Injection Units to provide a solution for any given application.
These multi-component injection molding processes can be divided into two main groups, according to the intended function of the molded part:
A. Composite molding
B. Assembly molding
Composite Molding
1.) Sequential molding
This process, which also includes multi-color injection molding, involves the sequential
addition of different plastic components. It is used, for example, for the mass-production
of control elements, such as keys and pushbuttons, incorporating abrasion-resistant
back-lit symbols molded from translucently pigmented plastics. Another typical example
is the multi-component injection molding of rear light covers, featuring differently colored segments.
2.) Overmolding
This process is used, for example, when handles and finger grips on equipment housings
have to be provided with a soft, non-slip covering. This is done by overmolding the thermoplastic
part with an elastomer.
3.) Co-injection
Also known as sandwich molding, this process can be used for the production of multi-layer parts
(usually three layers) and involves separate injection of the skin and core melts.
The two outer skins provide the part with a highquality surface finish, while the reinforcing materials
in the central core improve the part's mechanical and heat-resistant properties. The use of reclaim for
the core can help to reduce costs considerably, and a foam core reduces weight.
Assembly Molding
1.) Component assembly
By selecting materials which do not adhere to one another, it is possible to produce articulated
parts– knuckle joints, for example – assembled in the mold, thus waiving the need for downstream
assembly.
2.) Assembly molding of seals and gaskets
Special rigid/flexible composites, e.g. combinations of thermoplastic polymers with thermoplastic
or conventional elastomers, can display an extremely high strength bond without any need to
coat their mating surfaces with coupling agents. Rubber/thermoplastic composites, which are
used in cases where low weight and freedom from corrosion are of the utmost importance,
are rapidly replacing rubber/metal composites. A similarly important area of application is the
in-mold fitting of seals and gaskets. Thermoplastic elastomers are used as sealing materials
in most cases.
