Gas injection was widely used in the early 1990s and is currently one of the most efficient injection moulding technologies.

This technique gives new plastics opportunities to designers and manufacturers, compared to conventional injection moulding this will allow the creation of products that are difficult or even impossible in another way:

- Plastic parts with thick and empty walls;

- Plastic parts with great variety of thickness.

LIGHTNESS

Product weight reduction

FASTNESS

Faster production cycles

STABILITY

High dimensional accuracy

QUALITY

Better surface appearance and quality

When the gas injection technique is used, the polymer is compacted by the gas pressure and not by the injection machine. The gas injection allows obtaining products with an excellent quality on its surface, without deformations and with a minimum of residual tensions, resulting in a high dimensional stability.

We use our 20 years' experience of gas injection know-how to provide all the necessary support to companies so that the process of moulds and parts manufacturing occurs without a hitch. We provide information on:

– Where to inject the gas;

– How many injection points to use;

– Studying the gas injection filler.

We test and supervise gas moulding, making our machines and operators available for this purpose.


GAS PROCESSES

SHORT SHOT

The SHORT SHOT method comprises first injecting a controlled volume short shot of plastic to partially fill the in-mould product cavity (or cavities), normally about two thirds of the cavity followed by injecting N2 gas to complete filling of the cavity with plastic and gas encapsulated by the plastic.


FULL SHOT

The FULL SHOT method developed by NSB Ltd comprises filling or nearly filling the mould cavity or cavities with plastic and then injecting N gas into the plastic. Gas penetration compensates for the volumetric plastic. Gas penetration compensates for the volumetric shrinkage of the plastic by up to 15% by volume (as it cools and solidifies).


PEP 1

PEP 1 comprises methods of expelling plastic from a mould cavity after first filling the cavity with plastic. Gas is injected at machine nozzle or more normally at one or more selected positions within the mould cavity, in order to applying a packing pressure to the plastic, before one or more PEP outlet valves located in connecting runners are opened to allow expulsion of plastic into one or more secondary cavities each of a predetermined volume. Filling the predetermined volumes of the secondary cavities precisely controls the amount of plastic displaced. This enables the further penetration of gas into the product cavity as illustrated.
Refer also to PEP leaflet for other PEP processes.


GAS COOL

The principal objective of Gas Cool is to reduce moulding time cycles by faster conduction of heat from the plastic whilst it cools and solidifies (static gas injection does not have a significant cooling effect) – thereby significantly reducing moulding cycles and production costs. NSB's Gas Cool is based on replacing the first injection of gas with a second charge of gas whilst the first is exhausted at a controlled back pressure. This is repeated to maintain flow of gas at the same time retaining a gas pressure in the moulding. The pre-chilling of the gas at temperatures down to -25°C and retaining high pressure before injection into the plastic further increases the effectiveness of Gas Cool with additional reduction in time cycles.