Shut-Off Nozzles

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Shut-Off Nozzles

Shut-off nozzles are used exclusively for injection moulding processing and are often an essential component of the machine. Installed at the crucial interface between heated injection unit and cooled mould, the nozzle is the gateway which regulates the melt flow while bearing the entire contact force of the machine.

Shut-off nozzles were originally developed in the 1960’s to prevent melt drooling from the nozzle orifice once the injection unit pulled back from the cold mould after injection. This not only prevented loss of material but also reduced process breakdowns. Even today shut-off nozzles can still be used for this purpose but of course the advantages of using them have increased considerably since those times. Nowadays the primary functions of the shut-off nozzle include;

  • Reducing cycle times by dosing the next shot regardless of whether the mould is open or if the injection unit is retracted.
  • Improving part consistency by enabling accurate and repeatable shot loading.
  • Facilitating advanced moulding techniques such as physical and chemical foaming, melt pre-compression and multi component injection moulding.

To cover today’s spectrum of applications Herzog continually develops and expands itsselection of shut-off nozzles. The product profile ranges from custom-engineering solutions for specific demands, through pneumatic and hydraulic needle and bolt style nozzles, to economical spring loaded systems.

Productivity Improvement
Example Cycle Time Cycles Per Day Extra Cycles Per Day Percentage Difference
Without shut-off nozzle 10 sec. 8640 - -
With shut-off nozzle 10 sec. 9600 960 11.11%
How do they work?

There are two ways of operating shut-off nozzles:

Via injection pressure; the nozzle is closed in its standard state and opens once the injection pressure rises above a defined amount. This is known as pressure-dependent operation.

Via hydraulic or pneumatic actuator; the nozzle is actively opened or closed through a command from the machine’s control unit. This is a two-way control and is a pressure independent operation

Products Range
  • Needle shut-off with pressure dependent spring operation

Shut-off needle positioned in-axis with the melt flow

Spring force holds the nozzle closed

Injection pressure overcomes the spring force to open the nozzle

Used for standard applications to prevent drooling with retracted injection unit

Requires regular cleaning and maintenance

  • Needle shut-off with hydraulic or pneumatic actuator

Shut-off needle positioned in-axis with the melt flow

Hydraulic or pneumatic actively opens or closes the nozzle

Precise flow control

Operation independent of melt flow or pressure

Used for advanced moulding techniques, engineering plastics and aggressive materials

Self-cleaning function, low maintenance

  • Bolt shut-off with hydraulic or pneumatic actuator

Shut-off bolt positioned perpendicular to the melt flow

Hydraulic or pneumatic actively opens or closes the nozzle

Operation independent of melt flow or pressure

Used for high-viscosity materials, large volume shots, very fast running machines

Self-cleaning function, low maintenance

  • Needle shut-off with pneumatic actuator for elastomeric plastics

Shut-off needle positioned in-axis with the melt flow

Pneumatic actively opens or closes the nozzle

Operation independent of melt flow

Used for liquid silicone rubber

Integrated cooling system; prevents material vulcanization in the nozzle

For over 40 years, Herzog has built its reputation on developing exceptional shut-off nozzles for injection moulding machines. As a technology leader, each innovative solution is meticulously engineered at its Swiss facility and since 1996 the company is certified in accordance with ISO 9001:2008.