How to solve the problem of severe burrs on silicone rubber products?

1. In terms of molds
Check the accuracy and fit clearance of the mold
The excessive clearance between the mold cavity and the core is one of the important reasons for the occurrence of burrs. If the gap exceeds the minimum flash edge gap of silicone rubber during the molding process (usually around 0.01-0.02mm, depending on the performance and product size of the silicone rubber), the mold needs to be adjusted or repaired. For example, a professional mold grinder can be used to grind the mating surface of the mold and reduce the gap.
Check if the parting surface of the mold is flat. If there is any unevenness, silicone rubber is prone to overflow from the parting surface under injection pressure and form burrs. Precision grinding machines can be used to adjust the parting surface to achieve a high flatness, generally requiring the flatness error of the parting surface to be controlled within 0.005mm.

Optimize mold temperature control
The mold temperature has a significant impact on the flowability and curing properties of silicone rubber. If the mold temperature is too high, the flowability of silicone rubber will increase, making it easier to produce burrs. The mold temperature can be appropriately reduced. For example, for general hot vulcanized silicone rubber products, the mold temperature can be controlled between 120-180 ℃, and the specific temperature should be adjusted according to the vulcanization characteristics of the silicone rubber and the thickness of the product. By installing a cooling system (such as setting up cooling channels inside the mold) to control the mold temperature, the occurrence of burrs can be effectively reduced.

2. In terms of molding process
Adjust injection pressure and speed
Excessive injection pressure is a common cause of flash. When silicone rubber is injected into the mold cavity with excessive pressure, it will force the silicone rubber to extrude from the small gaps in the mold and form flying edges. The injection pressure can be appropriately reduced, for example, for small silicone rubber products, the injection pressure can be reduced from the original 5-10 MPa to around 3-5 MPa, but it is necessary to ensure that the silicone rubber can completely fill the mold cavity.
Injecting too quickly can also cause flying edges. Excessive speed can cause turbulence in the mold cavity, increasing the possibility of silicone rubber overflowing from the mold gap. Slow injection can be used, such as reducing the injection speed from 100-200mm/s to around 50-100mm/s.
Control vulcanization time
Excessive vulcanization time can cause silicone rubber to continue expanding within the mold cavity, thereby increasing the risk of flash formation. If the vulcanization time is too short and the product is not fully vulcanized, it can also cause difficulty in demolding, which may tear the product and produce burrs. The optimal vulcanization time needs to be determined through experiments based on the vulcanization system and mold temperature of silicone rubber. For example, for hot vulcanized silicone rubber, the vulcanization time is generally between 1-10 minutes, and the specific time should be based on the complete vulcanization of the silicone rubber and the product performance meeting the requirements.

3. In terms of silicone rubber materials
Choose the appropriate silicone rubber material
Different silicone rubber materials have different flowability and vulcanization characteristics. If silicone rubber with high fluidity is used, the flash problem will be even more severe. You can choose silicone rubber with moderate fluidity, such as high branched structure silicone rubber, which has relatively low fluidity. At the same time, attention should be paid to the hardness of silicone rubber. Silicone rubber with higher hardness is relatively less likely to produce burrs during the molding process.
Check the quality of silicone rubber material
Check whether the silicone rubber contains impurities or has deteriorated. Impurities may affect the flow and curing of silicone rubber during the molding process, leading to the formation of burrs. If silicone rubber deteriorates, its properties will change, such as faster or slower vulcanization speed, which will also affect the molding quality. Simple testing can be performed on silicone rubber, such as observing its appearance, measuring its viscosity, etc., to ensure that high-quality silicone rubber materials are used.