Two-Shot Mould Terminology

  • Boss: A raised cavity on the part designed facilitate alignment during assembly or attachment to other parts
  • Cold-runner mold: A mold in which the runners are kept at the same temperature as the mold and must be ejected at the end of each molding cycle
  • Draft: A slight taper built into the mold walls to facilitate removal of the part from the mold
  • Flash: Material that forms in the seams or parting lines of the mold cavity
  • Gate: The channel through which molten plastic resin enters the mold cavity
  • Hot-runner mold: A mold in which the runners are insulated or heated to keep resin in a molten state to facilitate flow control
  • Knockout pin: A pin that ejects the molded part from the mold
  • Living hinge: A thin section of the part along which the part can fold
  • Parting line: A mark on a molded part indicating where the two halves of the mold meet in closing
  • Rib: A thin wall-like feature that increases the bending stiffness of wall sections and bosses
  • Runner: A channel within the mold through which molten resin flows from the machine sprue to the cavity gate
  • Short shot: Failure to fill the mold completely with resin, resulting in missing geometry and melted edges
  • Shrinkage: The contraction of a plastic molded part as it cools
  • Shut-off: An area where the mold seals against the other half of the mold, an insert, or the first-shot substrate formed in the two-shot molding process, to form a slot, hole, or void
  • Sink mark: A surface indentation caused by differential rates of cooling in areas with significant changes in wall thickness
  • Sprue: The channel through which molten plastic resin flows from the machine nozzle to the mold runner
  • Undercut: A protrusion, hole, cavity, or recessed area in the part that impedes ejection from the mold, therefore requiring movable mechanisms within the mold to form the shape