Environmental Engineering Reference
In-Depth Information
Figure 4.5
Schematic diagram of an injection molding machine showing
the reciprocating screw and different heating zones.
Source: Reproduced with permission from Bull and Zhou (2001).
Figure 4.6
An injection molding machine and examples of molded
products.
Source: Reproduced with permission from Styrolution, Styrolux, BASF.
Injection molding is estimated to typically require 1.3-1.6 kW/kg of
moldings; however, less than 10% of this energy is input into the plastic
resin and most being used to operate the equipment (British Plastics
Federation, 1999). More than half the energy is spent during the so-called
“recovery” step where the screw rotates to create a fresh shot of melt to
be injected (Franklin Associates, 2011). Injection, mold release, and heaters
each account for about 10-15% of the energy; the heating energy is low
because the frictional heat contributes significantly to melting.
