Treatment of rubber products after vulcanization

After the vulcanization of rubber products, certain post-treatments are often required before they can become qualified products. This includes: ① trimming of rubber mold products to make the surface of the product smooth and the external dimensions meet the requirements; ② after some special processes, such as treating the surface of the product, the performance of the products for special purposes is improved; Products containing fabric skeletons, such as tapes, tires, etc., must be heat stretched and vulcanized and then cooled under inflation pressure to ensure the product's size, shape stability and good performance.

I. Trimming of mold products

When the rubber mold product is vulcanized, the rubber material will flow out along the parting surface of the mold and form an overflow rubber edge, also known as burr or flash. The amount and thickness of the rubber edge depend on the structure, accuracy, and thickness of the mold. The parallelism of the plate of the plate vulcanizing machine and the remaining amount of rubber. The products produced by the current endless molds have extremely thin rubber edges, which are sometimes taken away or removed by light rubbing when they are lifted from the mold. However, such molds are costly and easily damaged, and most rubber molded products require trimming treatment after vulcanization.

1. Manual trimming. Manual trimming is an ancient method of trimming. It involves manually cutting the rubber edge with a punch; using scissors, scraping and other tools to remove the rubber edge. The quality and speed of manual trimming rubber products will also vary from person to person. It is required that the geometric dimensions of the finished product must meet the requirements of the product drawing without scratches, scratches and deformation. Before trimming, the trimming site and technical requirements must be clear, and the correct trimming method and the correct use of tools must be mastered.

2. Mechanical trimming. Mechanical trimming refers to the trimming process of rubber mold products using various special machines and corresponding technological methods. It is currently the more advanced dressing method.

Mechanical punching and trimming With the help of press machinery, die and die, the rubber edge of the product is removed. This method is suitable for products and model products whose rubber edges can be placed on the bottom plate of a die or a knife, such as stoppers and leather bowls. For products with high rubber content and low hardness, the impact method is generally used to cut the edges. This can reduce the uneven edge and sag of the side due to the greater elasticity of the product. The low rubber content and high hardness can be reduced. The products can be punched directly by knife edge die. In addition, die cutting is also divided into cold cutting and hot cutting. Cold cutting refers to punching at room temperature, and requires higher punching pressure and better quality of punching; hot cutting refers to punching at higher temperatures. When cutting, prevent high temperature contact with the product for a long time, which will affect the product quality.

Mechanical cutting and trimming is suitable for the trimming of larger products, using cutting tools. Yifang cutting machines are special machines, and different products use different cutters. For example, after the tire vulcanization surface has different lengths of rubber strips at the air holes and exhaust lines, the rubber strips must be cut off with a grooved tool under tire rotation conditions.

Grinding by mechanical grinding For mold rubber products with inner holes and outer circles, grinding squares are usually used. The grinding tool is a grinding wheel with a certain thickness of particles. The accuracy of grinding and trimming is low, and the grinding surface is rough. There may be residual sand particles, which affects the use effect.

Low-temperature shot blasting trimming can be used for trimming delicate products with high requirements on trimming quality, such as O-rings and small leather bowls. The product is rapidly cooled to below the brittle temperature with liquid nitrogen or dry ice, and then the metal shots or plastic shots are sprayed at high speed to shatter the flashes and complete the trimming.

Low-temperature brush grinding and trimming It removes the rubber edge brushes of frozen rubber products by means of two nylon brushes rotating around a horizontal axis.

Low-temperature drum trimming It is the earliest frozen trimming method. The impact force generated by the rotation of the drum and the friction between the products are used to make the products that have been frozen below the embrittlement temperature flash break.