There has recently been a proliferation of products made in LSR (Liquid Silicone Rubber). LSR has characteristics that make it ideal for many fields of application. In particular, this material resists temperatures ranging from -60°C to +280°C, is very elastic and maintains good mechanical properties over a wide temperature range, it does not contain toxic or aggressive components, has a very good weathering, chemical and aging resistance and moreover can be injection moulded.

In contrast to the thermoplastic moulding process, that for LSR requires that the machine's plasticating unit be fed by a pressure system rather than by gravity alone or by screws. The unit, moreover, and also the runner system on the mould, has to be cooled, rather than heated. The mould, on the other hand, must be heated with plates or resistors up to 200°C. In fact, the curing of the material, activated by the mixing of two elements, can be accelerated or delayed by changing the temperature. However, once curing has started, it cannot be stopped, and there is no way to recover production scrap. Such a fact, given the high costs of the resin, can represent a serious problem.

Guzzini Engineering, always sensitive to market demands, has developed a version of its well-known PONY shut-off nozzle, adapted for LSR moulding. Notable features include the replacement of the cartridge heaters by a hydraulic circuit that allows the temperature of the injector to stay within the limits of the set-up temperature, without any problem. The PONY-LSR's characteristics render it the ideal solution for LSR moulding. In particular

1. During the injection phase the closing pin withdraws completely from the flow channel, preventing stagnation of partially cured material. This moreover makes the cleaning process an easy task.
2. At the end of the injection phase the pin goes forward to perfectly close the injection nozzle. This produces perfectly smooth injection points without any sprues.
3. The remarkable efficiency of the cooling circuit provides a perfect separation of the cold channel from the hot mould with great advantages in terms of cycle time.
4. The presence of a thermocouple allows for temperature monitoring and/or control, not only of the refrigeration fluid, but also of the injector, yielding perfect process control.
5. The pneumatically operated piston makes PONY-LSR the ideal choice for moulding medical and food applications, where oil contamination could be extremely harmful.
6. The positioning of the piston, off-center but still integrated into the nozzle itself, makes it possible to reduce overall dimensions and facilitates assembly.
7. Pony-LSR is ideal for single-cavity applications, but can also be perfectly integrated into cold manifolds developed specifically for multi-cavity systems.

PONY-LSR makes the liquid silicone rubber moulding economical.