Liquid silicone injection molding process

To obtain moulded products by liquid silicone injection molding, a cross-linking agent and a catalyst are pumped into different drums before being blended in the static mixer.

According to customer needs, colour pigments and additives can also be added. Through gravity, the material flows into the injection screw which transports it to the mould while maintaining it at room temperature.

The liquid silicone rubber (LSR) is then injected into the mould through the cold runner and heated at between 170°C and 200°C in order to vulcanise and to take its final shape.

Liquid silicone injection molding process

Liquid silicone rubber (LSR) injection technology is burr-free, so no post production deburring stage is necessary to obtain a perfectly smooth finish.

For some products a post curing stage is necessary to obtain a minimal level of volatile organic material. However this stage is gradually being phased out as “low level volatile” Liquid silicone rubber (LSR) has become available on the market and so the process can be 100% automated, including the packing stage at the end of the line.

 
Tool
 

Cavitites (ejection side): T = 150 - 220 °C

Cold number (injection side): T = 23 °C

Injection under vaccum

Liquid
Silicone
Rubber

Fluid material at room: T°;
vulcanising under high T°

Bi-component : mixing ration 1:1
A - catalyst (Pt)
B - crosslinker

Injection
molding
machine

Specific injection unit : T = 23 °C

Archimedes' screw with one-way valve

Peripherals' monitoring

LSR
mixing
unit

Pneumatic or hydraulic

Barrels pressure ¯ 200 bar

Addition of dies/additives

Static mixer and pressure reducer