Injection Molding Compounders Molders Get
Control Of Their Materials The combination of an injection molding press and
a twin-screw compounding extruder represents a new paradigm for processors:
They create their own materials as they mold them. Although the machinery
systems are expensive, they provide new opportunities for materials cost
savings and flexibility to tailor formulations for individual parts.
However, the molder must now take responsibility for the raw materials as
well as the molded parts. And adding complexity to the process also
multiplies the number of variables to control.
Nonetheless, these multi-million-dollar machines have established a growing
niche. Almost four dozen have been sold, and the number of suppliers has
grown to three, with a fourth supplying a different but related approach.
What started out a decade ago as a way to reduce the costs of molding
long-glass thermoplastic composites for structural automotive parts has
spread to non-automotive applications and to other sorts of compounding and
In-line compounding and injection molding got its initial impulse from the
upsurge of so-called DLFT or DLFRT technologies in recent years (see Learn
More). Direct Long-Fiber (Reinforced) Thermoplastic processes for in-line
compounding-and-moldingeither compression or injectionwere aimed
at helping thermoplastic composites compete more cost-effectively with
thermoset SMC (also a long-fiber process). DLFT was developed to be lower
cost than glass-mat thermoplastics (GMT) and long-fiber pellets produced by
thermoplastic pultrusion methods. Both GMT and long-fiber pellets require
sophisticated, proprietary processes to produce the intermediate raw
material in sheet or pellet form. GMT has the additional disadvantage of
producing substantial amounts of scrap that cannot be reused in that
The first DLFT processes separated the compounding and molding steps and
required a manual or robotic transfer of the hot compound to the press. The
latest step in the evolution is to integrate compounding and molding on an
injection machine to provide greater automation and shorter cycles than can
be achieved with compression molding.