Thermoset vs. Thermoplastic Injection Molding
Unlike thermoplastic injection molding, cured thermosets cannot be reground and
mixed with virgin material for reprocessing. In general, thermoset materials have a
low viscosity, so when the material fills the mold cavity under pressure, some of the
material will leak between the two halves of the mold typically at an area of the
cavity where vents have been added to allow for gas and air escapement. This is
called flash. While this problem can normally be prevented in thermoplastic injection
molding by proper mold construction and processing parameters, flashing cannot be
avoided in thermoset injection molding. Therefore, flash must be removed as a
secondary operation. When possible, the parts are deflashed
in an automatic
tumbling operation rather than hand deflashing
to save costs.