Three key points of precision injection of LSR injection molding machine

Mar 20, 2020

There are many differences in the traditional thermoplastic rubber processing of LSR injection molding machine, which undoubtedly increases the processing difficulty. LSR is very different from traditional thermoplastic materials in terms of shrinkage, demolding, mold materials, cold runner systems, temperature control, etc., which makes LSR more difficult to process than ordinary thermoplastics.

The waterproof silicone ring of a smartphone is generally composed of original metal and plastic parts, and the volume is smaller than the commonly used silicone ring. Compatibility with the shell and accessories is higher, so generally require more precise injection molding technology.
LSR injection molding machine
The key points of LSR injection molding machine to achieve precision injection molding are as follows:

Fully mixed liquid silica gel, accurate mixing ratio, LSR is a two-component raw material of A and B. Before injection molding, it must be mixed in a precise 1: 1 ratio. If it is a colored liquid silicone product, the proportion of color paste must also be accurately controlled. Then there is the mixer: the static mixer is a key component of injection molding. After the mixture is completely homogeneously mixed, the A and B glues can only be completely cured and molded into the mold.

In addition, the sealing and temperature control of the injection molding machine parts, because the viscosity of LSR is low, it is necessary to consider the reflow and leakage of the material, and the screw must be sealed; and because the mold is heated during the LSR molding process, in order to prevent LSR from solidifying, it is generally used Water-cooled nozzles to ensure that the temperature is low enough.

Control the dividing line of the finished product during injection molding, and consider the position and accuracy of the dividing line in advance to help avoid entrainment and welding air and avoid burrs; shrinkage rate Although LSR will not shrink during the injection molding process, due to its extremely high thermal expansion Coefficient, usually shrinks by 2% to 3% after demoulding and cooling;

It is necessary to consider the actual product shrinkage; ensure that the mold is sealed when designing the parting line, and the vacuum pump vacuums all the mold cavities through the clip below the mold switch. General demoulding: the stripping technique of fractionating tray, push pin and air ejector is generally used, or manual demoulding. Temperature, when LSR vulcanizes and forms during the heating process, the temperature in the mold must be uniformly distributed.