Among the many silicone parts, many need to be produced by silicone injection molding technology. Silicone O-ring, due to its characteristics, the degree of initial deformation is different, the hardness of the sealing material is different, and the compression pressure of the silicone rubber O-ring is also different.
silicone parts injection molding process
1. Tension and compression are two types of silicone parts installed in the groove. In the radial seal configuration, the O-ring is installed in the inner groove ((as an “outer seal” (), the O-ring must be stretched and its inner diameter stretched larger than the outer diameter of the groove. After installation, the maximum elongation of the O-ring should be 3% (inner diameter > 50mm) or 5%.
Take silicone injection molding as an example. Under the action of medium pressure in the groove, the silicone parts will deform and “flow” to the gap position to achieve the sealing effect. That is, as the pressure increases, the silicone parts deform more, and their stress increases, resulting in a tighter seal.
When the silicone parts are subjected to high pressure, they will be squeezed into the gap, causing the seal to fail. It is recommended to use a retaining ring of high hardness extrusions resistant material such as Teflon or hard rubber material. When we use silicone When injection molding, this is solved.
For silicone parts, in static sealing applications, the groove design can be modified to achieve higher pressures without the use of retaining rings. When designing, we should pay attention to making the gap as small as possible.
Silicone injection molding largely determines the characteristics of silicone parts. The size of the extrusion limit depends on the hardness of the O-ring, the working pressure, and the size of the groove gap. The radial clearance of the O-ring Groove must be kept within a certain range of radial clearance. If the tolerance is too large, it will cause the O-ring to squeeze out of the gap.
The allowable radial clearance between sealed components depends on system pressure, silicone parts’ cross-sectional diameter, and O-ring hardness. For the pressure greater than 5Mpa and the inner diameter of the O-ring greater than 50mm; and the pressure greater than 10Mpa and the inner diameter less than 50mm; we recommend the use of a retaining ring. In the production process of silicone injection molding, many details are easily ignored by us. Due to the excellent anti-extrusion ability and good dimensional stability of the polyurethane material O-ring, a larger gap can be used.
1. silicone parts
Back-up rings complement extruded seals such as O-rings and are not seals themselves. The purpose of using the retaining ring is to reduce the clearance on the low-pressure side of the O-ring and similar seals, and the structure of adding the retaining ring will bear much higher pressure than using the O-ring alone. This feature can be found in silicone injection molding.
2. Retaining ring material
The material of the retaining ring is mainly NBR, fluororubber, and PTFE. According to different use environments, we will recommend silicone parts of different materials for customers to use.
3. Application of silicone injection molding
The hardness of the rubber must be considered when selecting an O-ring. For general use occasions, we usually recommend a hardness of 70 degrees, because the material can obtain better comprehensive performance at 70 degrees. For use in high-pressure environments, general 70-degree materials are easier to extrude.
However, using a hardness above 85 Shore will have little success in dynamic environments, because the harder material does not easily follow the roughness of the sealing surface (such as the cylinder wall). All right.
Using the wear resistance of low hardness silicone parts and the high-pressure retaining ring, very good sealing performance can be obtained.
The company is committed to continuous improvement of inventory and the development of new products. Thereby, the problems of a long cycle and the high price of imported products are solved.
