Extended Nozzle
It is a special nozzle that lengthens the nozzle of the ordinary injection machine so that it can directly contact the gate of the mold. It is heated by an electric heating coil and has a temperature measurement and control system. The temperature of the nozzle is required to be 15-20°C higher than that of the barrel. The nozzle mouth is actually the gate of the cavity, and a point gate with a diameter of 0.8-1.2mm is commonly used.
Since the high-temperature nozzle directly (or indirectly) forms the plastic part, the mold must be insulated to prevent the high temperature of the nozzle from affecting the curing of the plastic part. Air gap and plastic skin insulation are commonly used. After injection and pressure holding, the nozzle should be separated from the mold to minimize the contact area between the nozzle and the mold.
The extended nozzle has a simple structure and is often used in single-cavity molds. Commonly used are spherical, conical and other forms.
(a) spherical nozzle (b) conical nozzle
(c) Forming nozzle (d) Adiabatic nozzle
The structure of the extension nozzle
Figure (a) The nozzle extends into the sprue sleeve, the nozzle is positioned by the shoulder and bears the force, and there is a bushing to increase the gap between the nozzle and the sprue sleeve.
Figure (b) The end face of the nozzle is a part of the cavity, with an intermediate bush, an air gap slot, and the introduction of cooling water.
Figure (c) The nozzle must be positioned against the injection seat to withstand the pressure. The front end of the nozzle matches the hole, and thermal expansion must be considered
Bulge and flash.
Figure (d) is a heat-insulating nozzle, with a bowl-shaped plastic heat-insulating skin, with a central thickness of 0.4-0.5mm and an outer side of 1.2-1.5mm. The pressure shoulder is embedded with a PTFE gasket. Ensure the strong rigidity at the bottom of the sprue cup.
