Does the tolerance of the substrate affect the sealing effect during the secondary molding of liquid silicone?

Liquid silicone secondary molding technology, as an important manufacturing process, is widely used in multiple fields, especially in the manufacturing of components that require multi-layer structures or complex assembly relationships. In this process, the tolerance control of the substrate has become one of the key factors affecting the sealing effect.
Firstly, we need to understand the basic principle of secondary molding of liquid silicone gel. This technology usually involves two or more independent molds. First, the initial molding of some components is completed in one mold. Then, these components are transferred to another mold and injected with new liquid silicone material to achieve secondary bonding. This technology is particularly suitable for the manufacturing of complex structural components such as the combination of anti drop borders and soft rubber back shells in mobile phone protective cases.

In the secondary molding process of liquid silicone gel, the influence of substrate tolerance on the sealing effect is mainly reflected in the following aspects:
1、 Tolerance affects the filling effect of liquid silicone gel
Excessive or insufficient tolerance may result in liquid silicone not being able to fully cover the corners or gaps of the substrate, thereby affecting the sealing effect. When the tolerance is too large, liquid silicone may not be able to fully fill the small gaps of the substrate due to insufficient fluidity, resulting in glue leakage and affecting the sealing and durability of the product. On the contrary, when the tolerance is too small, the fluidity of liquid silicone may be limited, making molding difficult and even causing product deformation.
In order to optimize the filling effect, manufacturers need to strictly control the tolerance of the substrate and make reasonable adjustments based on parameters such as the viscosity of the liquid silicone gel, injection pressure, and mold temperature. For example, for liquid silicone with high viscosity, the injection pressure can be appropriately increased to promote filling; For substrates with smaller tolerances, higher precision molds and stricter process control are required to ensure the uniform distribution of silicone.
2、 Tolerance affects the strength of the bonding interface
The substrate tolerance not only affects the filling effect of liquid silicone, but also directly affects the strength of the bonding interface. Excessive tolerance may result in uneven bonding surfaces, reducing the adhesion between liquid silicone and substrate, thereby affecting the overall strength of the product. On the contrary, a too small tolerance may cause excessive pressure on the liquid silicone gel during the curing process, resulting in internal stress and reducing the strength of the bonding interface.
In order to enhance the strength of the bonding interface, manufacturers need to perform precise surface treatment on the substrate, such as sandblasting, chemical etching, or plasma treatment, to improve the adhesion of liquid silicone gel. Meanwhile, in the process of liquid silicone injection molding, it is necessary to strictly control the injection speed and temperature to ensure sufficient bonding between the silicone and the substrate.
3、 Tolerance affects the dimensional stability of products
The influence of substrate tolerance on product dimensional stability cannot be ignored. During the solidification process of liquid silicone, due to the different thermal expansion coefficients of the substrate and silicone, excessive tolerances may cause dimensional changes in the product during cooling, thereby affecting the dimensional accuracy and assembly performance of the product.
In order to control the dimensional stability of the product, manufacturers need to fully consider the impact of substrate tolerances on dimensional changes during the design phase and take corresponding compensation measures. For example, reserving a certain amount of shrinkage allowance during mold design, or using temperature control technology during liquid silicone injection molding to reduce the impact of thermal expansion on dimensional stability.
4、 Tolerance affects production costs and efficiency
The impact of substrate tolerances on production costs and efficiency cannot be ignored. Excessive or insufficient tolerances can lead to an increase in scrap rates during the production process, thereby increasing production costs. Meanwhile, improper tolerance control may also affect the automation level of the production line and reduce production efficiency.
In order to reduce production costs and improve production efficiency, manufacturers need to strengthen the control and management of substrate tolerances. This includes optimizing mold design, improving the accuracy and stability of manufacturing processes, and strengthening quality inspection and monitoring. By continuously improving and optimizing production processes, manufacturers can gradually reduce production costs, improve product quality and competitiveness.
In addition to the above aspects, substrate tolerances may also affect other factors during the secondary molding of liquid silicone, such as the curing speed of silicone and the appearance quality of the product. Therefore, in the secondary molding process of liquid silicone gel, manufacturers need to comprehensively consider multiple factors and develop scientifically reasonable tolerance control strategies.
In practical operation, manufacturers can take the following measures to optimize tolerance control:
1. Strengthen the procurement and inspection of substrates to ensure that their dimensional accuracy and surface quality meet the design requirements.
2. Optimize mold design, improve mold accuracy and stability, and ensure that liquid silicone can be evenly distributed during the injection molding process.
3. Strengthen quality inspection and monitoring in the production process, timely identify and handle quality problems caused by improper tolerance control.
4. Continuously improve and optimize production processes to enhance product quality and production efficiency.
In summary, the substrate tolerance has a significant impact on the sealing effect of liquid silicone during secondary molding. In order to optimize the sealing effect, manufacturers need to strictly control the tolerance of the substrate and make reasonable adjustments based on the material characteristics and molding process of liquid silicone. At the same time, manufacturers also need to strengthen quality inspection and monitoring work, timely discover and handle quality problems, to ensure the quality and competitiveness of products. By continuously improving and optimizing production processes, manufacturers can continuously promote the development and application of liquid silicone secondary molding technology, contributing to the transformation, upgrading, and high-quality development of the manufacturing industry.