The definition of runnerless moulding is employed to explain any kind of mould tool in which a traditional
cold runner and sprue will not be generated :

Sprueless moulding

  • Insulated runner systems
  • Hot runner systems
 
Sprueless Moulding
There are 2 major categories for sprueless moulding:
  • Fundamental antechamber designs
  • Heated up hot sprue bushes or nozzles

Basic Antechamber Type

Sprueless moulding is frequently used for fast-cycling one cavity tools making
thin wall components in non -heat-sensitive materials just like PE, PP an d PS.
This technique normally is made up of particularly formed machine nozzle. which can be designed to
accommodate with a recessed characteristic inside the mould tool. The most basic designs combine an
antechamber characteristic. using this type of layout , a thin skin of cooler material insulates a
melted central core between the nozzle and gate.
Figure  demonstrates 3 standard types of antechamber type nozzle. The design and style demonstrated in following
Figure  has the advantage that if the melt
inside the nozzle stiffens to a cold slug, the
undercut
form on the nozzle enable s quick drawback from the tool. Figure (c) demonstrates
an antechamber feed system without having a cold slug well.
 
This method could also be used for bigger mouldings running on a single -impression
basis in which maximum control and quality are needed.
2.
 
Sprueless moulding options can also be utilized for much more heat-sensitive materials. In
these kinds of situations
it’s preferable to prolong the nozzle with regards to the gate , as in Figures 2. and
Figure 3. The serrated undercut on the nozzle in Figure  normally takes the type of a
screw thread. T his enables the cold plug to be merely unscrewed following the cylinder is
took back from the tool.
3.
Aside from the apparent conserving in eliminating the sprue, prolonged nozzles are employed in
three-plate or rnulr ipla re designs to reduce the opening stroke. Considering that no sprue is molded,
the opening required to allow the runner (if any) to be removed is much less.