When conducting LSR injection molding in plastic manufacturers, it is necessary to consider several aspects such as raw material characteristics, mold design, and equipment selection. The following are the design points of LSR injection molding summarized by BOOLING:

1. Selection of Mold Materials

The commonly used material for mold support plates is generally non-alloy tool steel. Mold support plates need to withstand high temperatures above 170 ℃, so their materials need to have good high-temperature resistance and rigidity and can be made of tempered steel. For mold support plates with mold cavities, B-shaped steel can be used, but it must be tempered or nitrided. For LSR materials with high filling requirements, such as oil-resistant LSR, manufacturers usually use bright chrome-plated steel or powder metal specially developed for this purpose, which have higher hardness and stiffness. When suppliers design molds with high friction, they can design components with high friction to be easy to replace, which will consume less time in providing maintenance services. The inner surface of the mold cavity greatly affects the surface smoothness of the product, so for products with high transparency, the mold should be polished before use. Materials such as nickel steel that have undergone surface treatment will have better wear resistance and easier demolding in the later stage.

2. Parting Line

One of the main steps for manufacturers to design silicone rubber injection molds is to determine the position of the parting line, and the grooves on the parting line are also an important factor affecting exhaust. Due to the strong fluidity of LSR materials, it is easy to cause overflow and affect the final product. At this time, the parting line of the mold must be accurate. Due to the influence of product shape on demolding, setting long chamfers on the product makes it easier to de-mold and less likely to cause product damage.

3. Injection Point

When processing LSR materials, a cold runner system is usually used, which can maximize the advantages of this rubber material, avoid material waste, and greatly accelerate the forming speed. The injection nozzle for rubber materials uses a needle valve as a forward flow control. Currently, many manufacturers have made injection nozzles with pneumatic switches as standard equipment and installed them in various parts of the mold. Even some mold manufacturers have specially developed an open cold runner system. Due to its small volume, multiple injection points need to be set up in the space to fill the entire mold cavity. This technology can produce a large amount of high-quality silicone rubber products without the need to separate the injection port. The most important aspect of using a cold runner system is to establish an effective temperature gap between the hot mold cavity and the cold runner. If the runner temperature is too high, the rubber material may undergo vulcanization before injection molding begins. However, if the temperature drops too quickly, the rubber material will absorb additional heat in the gate area, resulting in incomplete vulcanization of the material. For products injected using conventional sprues (such as submerged sprues and conical sprues), manufacturers should use small-diameter injection ports during pouring. LSR rubber, like thermoplastic rubber, has strong fluidity and low viscosity, so manufacturers need to pay extra attention to the balance of the flow channel system to ensure that the mold cavity can be uniformly filled.