Among all silicone rubber products, apart from tires which are the most common, the O-ring (also known as 0-ring) is the other one. It has basic characteristics such as shock absorption, sealing and wear resistance. Depending on the material, it can also have properties like oil resistance and chemical resistance. It is commonly used in excavators, automobiles, instruments and meters, construction machinery and other fields.
The most fundamental criterion for evaluating the quality of a sealing ring is whether there are any burrs (spurs). Because only with zero burrs can the sealing performance of the O-ring be guaranteed. Today, we are going to discuss how burrs are generated and how to achieve an O-ring with zero burrs.
The formation of burrs usually occurs during the molding and vulcanization process. At this time, the rubber material fills the entire cavity of the mold. Since the amount of the filled rubber material needs to be sufficient, the excess rubber material will flow out along the parting surface, resulting in different thicknesses of inner and outer diameters at the edges. Such edges are called burrs.
There are two common methods of trimming: manual trimming and mechanical trimming.
1. Hand trimming
This method is the most primitive and traditional one. It involves manually using a tool to remove the rough edges on the inner and outer edges of the ring. The quality of this edge-repairing method depends on the experience of the worker. It is inefficient and has a high scrap rate. Therefore, it is only suitable for the processing of small-batch zero-edge O-rings.
2. There are two types of mechanical edge trimming: grinding with a grinding wheel and edge removal through low-temperature freezing.
Compared with manual edge trimming, grinding with grinding wheels and sandpapers offers more significant improvements in terms of efficiency and quality. The specific method is to place the vulcanized O-ring on a sanding rod or nylon rod with the same inner diameter as the O-ring. Then, a motor is used to drive it to rotate at high speed, and the O-ring's outer circle is rubbed by sandpaper or grinding wheels to achieve edge trimming. However, the accuracy is not high, and the roughness of the grinding surface is the drawback of this edge trimming method.
The other method is low-temperature freezing edge removal. This technique originated from Japan and is also a type of mechanical edge trimming. The difference is that it operates in a refrigerated environment. It can achieve zero-edge O-rings through five different forms: vibration, oscillation or shaking, drum rotation, brush grinding, and shot blasting.
The specific principle is as follows: In a low-temperature refrigeration environment, the thin edges of the O-ring change from an elastic state to a glassy state due to freezing (becoming harder and more brittle), but the product itself still retains some elasticity. Then, during the vibration operation (or other five forms), the products collide with each other, the products come into contact with the abrasive agent for abrasion, and the products interact with the shot blasting for impact. At this point, the thin edges will be broken and fall off. Eventually, the purpose of edge trimming is achieved. After that, the product will regain its original performance at room temperature. This method has high production efficiency, but the edge trimming effect on the inner ring is relatively poor.
Alright, that's all the information about zero-overhang O-rings we can share for now. The manufacturer should, based on their own specific circumstances, choose one or more edge-trimming methods appropriately.
Yongyong Silicone Rubber has been dedicated to silicone rubber products for 25 years, providing a complete solution from material research, mold development to silicone rubber product manufacturing. Welcome to visit our factory. Website: www.seidai88.com
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