Jan 20, 2020
Contamination (especially when using recyclates) can be removed from the plastic melt with the help of a filter nozzle.
This saves the often very complex cleaning of the following mold components.
Furthermore the plastic melt is homogenized by the filter nozzle.
This has highly positive effects for the distribution of additives and colorants.
The fitler nozzle is attached to the injection unit using a machine-dependent adapter.
The filter removes any contamination (e.g. metal or wood shavings, not melted material) from the plastic melt.
The filter nozzle is very flexible and can be used for almost every application, as well as for filled materials, due to the different filter fineness.
If the filter is contaminated, it can be flushed without disassembly by an automatic “flushing process”.
Hot Runner: Filter nozzle with two different filter inserts.
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This glossary of plastic industry is provided by PLEXPERT Canada Inc.
Nov 5, 2018
In hot runner systems heater bands are used. This is to bring the temperature inside of the melt channel up to the wanted process temperature and keep it constantly at this level.
The hot runner system consists mostly of one manifold and one or more hot runner drops.
In order to control the temperature a sensors are used in combination with PID-Controller.
The aim is to reach a homogeneous temperature distribution within the melt channel.
Nov 15, 2018
In an injection molding tool, the melt channel between cylinder and cold runner / cavity is called hot runner.
The difference from a cold runner is that the hot runner has at least one heater band to keep the hot runner at temperature.
The melt inside the hot runner stays fluid during the complete cycle and will be used directly for the next shot.
No waste is produced.
Hot runners are used to save material or to avoid weld lines (sequential injection).
Nov 27, 2018
In a hot runner system, the hot runner nozzle is located between the manifold and cold runner or cavity.
As it is the last heated area for the melt, a good temperature control is important.
There are both, open and closed nozzles (valve gates).
Dec 6, 2018
The transportation of the molten plastic from the injection unit through the mold to the cavity can be done by a hot runner system.
This consists of at least one sprue bushing, the manifold and one or more hot runner gates.
The single components are provided with heaters, which are controlled by suitable PID-Controllers, to achieve a uniform temperature distribution. The system, on the other hand, is thermally decoupled from the mold so that there is a homogeneous heat balance inside the hot runner system.
Advantages of a hot runner system are for example the saving of material and the reduction of the cycle time.
There are different versions of hot runner systems.
The simpliest is the hot runner system with thermal lock.
At the end of the injection and packing phase the melt is cooling down at the gate due to the heat transfer in the colder mold.
The viscosity of the plastc decreases and a “thermal lock” develops, which prevents the melt from entering into the cavity.
Hot runner systems with valve gates are commonly used.
A needle is added to the gates. It can be moved by cylinders (hydraulic or pneumatic) allowing or preventing the melt to enter the cavity.
Advantages of the usage of valve gates are the controllable filling of the parts and that the break-off point can be designed without a residual pin.
