Spring activated needle type shut-off nozzle

Application

The needle type shut-off nozzle (NVD) is used to process thermoplastics and liquid media. The choice of nozzle size depends on the flow of injection volume (cm3/s).

The NVD (shut-off nozzle) is responsible for the clean separation of the molten mass and reliable shut-off during dosing and is the prerequisite for fault free, economic production.

The GT-NVD stands out with its compact, modular construction. It guarantees fault-free functioning and optimum flow geometry. The shut-off system separates the flow of the mass, depending on the process, at a defined point.

Targeted deployment of wear protection guarantees a long service life.

Description of function

The spring loaded NVD type A is opened by the pressure of the molten mass and is shut off by the power of the spring.

A needle that moves axially in the NVD is pushed by the power of the spring via the pressure pin to the NVD’s outlet drill hole. The nozzle’s outlet opening is shut. The nozzle opens with increasing molten mass pressure, which operates via a ring surface on the needle against the power of the spring, at approx. 200 bar. The nozzle shuts off when the molten mass pressure decreases (80 bar). The pressurised ring surface of the needle must be made larger (less opening pressure) or smaller (greater opening pressure) when a different opening pressure is required. The pressure spring is not modified, as this would affect its service life. Temperature resistant material up to a maximum of 520°C is selected for the spring.

Advantages

  • Shorter cycle times
  • Dosing with withdrawn nozzle
  • Greater process reliability when injection moulding
  • Compact and robust construction
  • All parts can be replaced
  • Simple upgrade at any time
  • User friendly

Features

  • Modular construction
  • Delivered including heating element and thermal sensor
  • Customised design
  • Maximum injection pressure of 2000 bar
Operating data A0 A1 / A1.1 A2
Injection volume cm3/s based on polystrene
up to 45 up to 500 up to 750
Screw Ø [mm] up to 18 20 - 50 up to 80
Opening pressure
200 bar 200 bar 200 bar
Injection pressure
2000 bar 2000 bar 2000 bar
Operating temperature
350°C 350°C 350°C