Post-treatment of vulcanization of rubber products

Rubber products often require some post-processing after vulcanization to become qualified finished products. This includes:

The rubber mold products to trim, so that the surface of the product is smooth, the size of the requirements;

② After some special processing, such as surface treatment of products, the performance of special purpose products has been improved; ③ products containing fabric skeleton such as tape, tires and other products should be cooled by hot stretching and vulcanization under inflation pressure to ensure product size, shape stability and good performance.

Finishing of 1. mould products after vulcanization

During vulcanization of rubber mold products, the rubber material will flow out along the parting surface of the mold and other parts to form overflow rubber edge, also known as burr or flash. The amount and thickness of the rubber edge depend on the structure and accuracy of the mold, the parallelism of the plate of the flat vulcanizer and the amount of residual rubber. The products produced by the current endless molds have extremely thin rubber edges, and sometimes they are taken off when the mold is taken off or can be removed with a light wipe. However, this kind of mold cost is high, easy to damage, most of the rubber molded products need to be trimmed after vulcanization.

1. Manual trimming

Manual trimming is an ancient trimming method, which includes manually punching the rubber edge with a punch; using scissors, scrapers and other tools to remove the rubber edge. The quality and speed of manually trimmed rubber products will also vary from person to person. It is required that the geometric dimensions of the trimmed products must meet the requirements of the product drawings, and there must be no scratches, scratches and deformation. Before trimming, the trimming parts and technical requirements must be clearly understood, and the correct trimming methods and tools must be mastered.

2. Mechanical trimming

Mechanical finishing refers to the use of a variety of special machines and the corresponding process methods for rubber mold products trimming process. It is currently the most advanced dressing method.

(1) Mechanical punching and trimming The rubber edge of the product is removed by means of pressure machinery, stamping dies and punching knives. This method is applicable to products and model products whose rubber edges can be placed on the bottom plate of a die or punch knife, such as bottle stoppers, leather bowls, etc. For products with high glue content and low hardness, impact trimming is generally adopted, which can reduce the uneven edge and side depression caused by the large elasticity of the product. For products with low glue content and high hardness, the method of knife edge die can be directly adopted for punching. In addition, punching is also divided into cold cutting and hot cutting. Cold cutting refers to punching under the posture piece at room temperature, which requires higher punching pressure of the equipment and better punching quality. Hot cutting refers to preventing high temperature contact with products for too long and affecting product quality during punching at higher temperature.

(2) Mechanical cutting and trimming is suitable for trimming products with large external dimensions, and cutting tools are used. One side cutting machine is a special machine, different products use different cutters. For example, after the tire is vulcanized, there are rubber strips with different lengths on the surface air hole and exhaust line. The rubber strips must be removed by a grooved device under the condition of tire rotation.

(3) Mechanical grinding and trimming For mold rubber products with inner holes and outer circles, grinding is usually used. The grinding tool is a grinding wheel with a certain thickness of particles, the precision of grinding and trimming is low, and the grinding surface is rough, which may contain residual sand particles, affecting the use effect.

(4) Low-temperature shot blasting trimming For fine products with high trimming quality requirements, such as O-rings, small leather bowls, etc., this method can be used for trimming. The product is rapidly cooled to below the brittle temperature with liquid nitrogen or dry ice, and then the flash is broken and peeled off by high-speed spraying of metal projectiles or plastic projectiles to complete trimming.

(5) Low-temperature brush grinding and trimming It is to remove the rubber edge brush of frozen rubber products by means of two nylon brushes rotating around the horizontal axis.

(6) Low-temperature drum trimming 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 break and fall off the flash of the products that have been frozen below the embrittlement temperature. The shape of the drum is generally octagonal to increase the impact force of the products in the drum. The rotating speed of the drum should be moderate, and the efficiency can be improved by adding abrasive. For example, the trimming process of the rubber plug of the electrolytic capacitor is the use of low-temperature drum trimming.

(7) Low-temperature vibration trimming is also called vibration freezing trimming. The products vibrate in a spiral shape in the circular sealing box. There is a strong impact between the products and between the products and the abrasive, resulting in the frozen embrittlement of the rubber edge. The low temperature vibration trimming is better than the low temperature drum trimming, the product damage rate is low, and the production efficiency is high.

(8) Low-temperature swing and jitter trimming are applicable to small or miniature products or miniature rubber products containing metal skeletons, and the rubber edges in the product holes, corners and grooves are repaired together with abrasives.