There are many differences between LSR and traditional thermoplastic rubber processing, which makes processing difficult. LSR differs greatly from traditional thermoplastic materials in terms of shrinkage, mold release, mold material, cold runner system, temperature control, etc., making LSR processing more difficult than ordinary thermoplastic glue.

The waterproof silicone ring of the smart phone is mostly secondary-molded on the original metal or plastic accessories, and the volume is smaller than that of the commonly used silicone ring. Injection molding technology.

The key points for LSR to achieve precision injection molding are as follows:

(1) Thorough mixing of liquid silica gel
Precise mixing ratio: LSR is a two-component raw material. Before injection molding, it must be fully mixed according to accurate 1: 1. If it is a colored liquid silicone product, the color paste ratio must also be accurately controlled.

Mixer: The static mixer is a key component in injection molding. Only after the static mixer is fully and uniformly mixed can the liquid silicone injected into the mold be completely cured.

(2) Sealing and temperature control of injection molding machine parts
Due to the low viscosity of the LSR, it is necessary to consider the reflow and leakage of the material, and the screw must be sealed;

Because the mold is heated during the LSR forming process, in order to prevent the LSR from curing, a water-cooled structure nozzle can be used to ensure that the temperature is sufficiently low.

(3) Finished product control during injection
Parting line: The position and accuracy of the parting line are considered in advance, which helps to avoid air entrainment and welding, and avoid burrs;

Shrink: Although LSR does not shrink during injection molding, due to its extremely high thermal expansion coefficient, it usually shrinks by 2% to 3% after demolding and cooling;

Location of the injection port: the actual product shrinkage needs to be considered;

Evacuation: When designing the parting line, ensure that the mold is sealed. The vacuum pump evacuates all the cavities through the clamp under the mold switch;

Demoulding: Demoulding column trays, ejector pins and ejector technology are generally used, or manual demoulding.

Mold temperature: LSR is vulcanized during heating, and the temperature in the mold must be controlled to be evenly distributed. The temperature difference is controlled at +/- 10 ° C.