Application of Rubber Extrusion Machinery in Rubber Products

Rubber products are widely used in automotive, construction, aerospace, electrical and electronic, medical and other fields due to their excellent elasticity, wear resistance, corrosion resistance and sealing performance. The forming process of rubber products is complex, involving mixing, extrusion, vulcanization and other key links, among which extrusion is a core forming process that determines the shape, size and performance of products. Rubber extrusion machinery, as the main equipment of the extrusion process, has been continuously upgraded and improved with the development of the rubber industry, and has gradually developed from a single extrusion function to an integrated production line integrating mixing, extrusion, shaping and vulcanization.

Compared with traditional forming methods, rubber extrusion machinery has obvious advantages: it can realize continuous production, greatly improve production efficiency; the extruded products have uniform size, stable performance and good consistency; it can adapt to different types of rubber materials (such as natural rubber, synthetic rubber, recycled rubber) and different product shapes; the operation is simple, the maintenance is convenient, and the production cost is relatively low. These advantages make rubber extrusion machinery become an indispensable key equipment in the rubber product manufacturing industry, and its application scope is constantly expanding with the continuous emergence of new rubber products.

This paper systematically expounds the application of rubber extrusion machinery in various rubber products, combines the production practice, analyzes the application characteristics and technical requirements, and provides a reference for the rational selection and application of extrusion machinery in the rubber industry.

The basic structure of rubber extrusion machinery mainly includes feeding system, extrusion system, die system, cooling setting system, traction system and control system, each part cooperates with each other to complete the extrusion forming of rubber products:

• Feeding system: It is mainly composed of a feeding hopper and a feeding device, which is used to transport the mixed rubber material into the extrusion system stably and uniformly. The feeding device usually adopts a screw feeder or a plunger feeder, which can adjust the feeding speed according to the extrusion speed to ensure the stability of the extrusion process.
• Extrusion system: It is the core part of the extrusion machinery, mainly composed of a screw and a barrel. The screw is the key component that realizes the conveying, mixing, plasticizing and extrusion of rubber materials. According to the structure, it can be divided into single-screw, twin-screw and multi-screw extruders. The barrel is matched with the screw to form a closed extrusion space, and the inner wall is usually provided with a heating or cooling device to adjust the temperature of the rubber material.
• Die system: It is used to shape the extruded rubber material into the required product shape and size, which is composed of a die body, a core rod and a positioning device. The structure of the die is determined according to the shape of the product, such as circular die for rubber hoses, rectangular die for rubber profiles, and special-shaped die for seals.
• Cooling setting system: After the rubber material is extruded from the die, it needs to be cooled and set in time to maintain the shape and size of the product. Common cooling methods include water cooling, air cooling and oil cooling, among which water cooling is the most widely used due to its high cooling efficiency and uniform cooling effect.
• Traction system: It is used to pull the cooled and shaped rubber products at a constant speed, ensuring that the products are extruded continuously and stably, and the size is uniform. The traction speed can be adjusted according to the extrusion speed to match the production rhythm.
• Control system: It is composed of a controller, a sensor and an actuator, which is used to control the temperature, pressure, speed and other parameters of each part of the extrusion machinery, ensuring the stable operation of the equipment and the qualified rate of products.

The working principle of rubber extrusion machinery is to use the rotation of the screw in the barrel to generate pressure and shear force, so that the rubber material is conveyed forward in the barrel, and at the same time, through the heating of the barrel and the shear heat generated by the friction between the screw and the rubber material, the rubber material is plasticized and melted into a uniform viscous flow state. Then, under the action of the extrusion pressure, the viscous rubber material is extruded through the die with a specific shape, and after cooling and setting, it forms a rubber product with a fixed shape and size. Finally, the product is pulled by the traction system and cut into the required length to complete the entire extrusion forming process.

The key of the extrusion process is to control the temperature, pressure and speed parameters. The temperature directly affects the plasticization effect of the rubber material and the forming quality of the product; the pressure ensures that the rubber material can be fully filled into the die and extruded smoothly; the speed determines the production efficiency and the uniformity of the product size. Only by reasonably matching these parameters can we produce high-quality rubber products.

Rubber extrusion machinery is widely used in the production of various rubber products, covering tires, rubber hoses, rubber seals, rubber profiles, rubber sheets and other fields. Different types of extrusion machinery and dies are selected according to the characteristics of products, so as to meet the production requirements of different products.

Tires are one of the most important rubber products, and rubber extrusion machinery plays an important role in the production of tire components such as tire tread, tire sidewall, tire bead and inner liner. The tire production has high requirements on the uniformity, compactness and performance of the rubber material, and the extrusion machinery can well meet these requirements.

In the production of tire tread, twin-screw extruders are usually used. The twin-screw extruder has strong mixing and plasticizing capacity, which can fully mix the rubber material, carbon black, vulcanizing agent and other additives, ensuring the uniformity of the tread material. The extruded tread is cooled and set, and then cut into the required length, which is used for the subsequent tire building process. The extrusion speed of the tread can reach 10-50 m/min, which greatly improves the production efficiency.

In the production of tire sidewall and inner liner, single-screw extruders are usually used. The sidewall requires good elasticity and wear resistance, and the inner liner requires good air tightness. The extrusion machinery can adjust the temperature and pressure parameters according to the performance requirements of the material, ensuring that the extruded sidewall and inner liner have stable performance. In addition, rubber extrusion machinery is also used in the production of tire bead wrapping rubber, which can improve the bonding strength between the bead and the tire body.

The application of rubber extrusion machinery in tire production not only improves the production efficiency, but also ensures the uniformity and stability of tire performance, which is an important guarantee for the quality of tires.

Rubber hoses are widely used in fluid transportation in automotive, engineering machinery, petroleum, chemical and other fields. According to the structure, they can be divided into braided rubber hoses, wound rubber hoses and smooth rubber hoses. Rubber extrusion machinery is the core equipment in the production of rubber hoses, which is used in the extrusion of inner rubber, outer rubber and middle rubber layers.

In the production of braided rubber hoses, the inner rubber layer is first extruded by a single-screw extruder. The inner rubber layer requires good air tightness and corrosion resistance, so the extrusion temperature and pressure need to be strictly controlled to ensure the compactness of the inner rubber. Then, the braiding machine is used to braid the skeleton layer (such as polyester fiber, steel wire) on the inner rubber layer, and then the middle rubber layer and the outer rubber layer are extruded by the extrusion machinery. The outer rubber layer requires good wear resistance and weather resistance, and the extrusion machinery can adjust the formula and process parameters of the rubber material to meet these requirements.

For wound rubber hoses, the production process is similar to that of braided rubber hoses, but the skeleton layer is wound by steel wire or fiber, and the extrusion machinery needs to match the winding speed to ensure the uniformity of the rubber layer. For smooth rubber hoses (such as water hoses, air hoses), single-screw extruders are usually used for one-time extrusion forming, which has the advantages of simple process and high production efficiency.

The key of rubber hose extrusion is to ensure the uniformity of the rubber layer thickness and the bonding strength between the layers. The extrusion machinery can realize precise control of the rubber layer thickness through the design of the die and the adjustment of the traction speed, and improve the bonding strength between the layers through the control of the extrusion temperature.

Rubber seals are widely used in automotive, mechanical, electrical and other fields to prevent fluid leakage and dust entry. Common rubber seals include O-rings, oil seals, gaskets, etc. The production of rubber seals has high requirements on the shape accuracy and dimensional stability, and rubber extrusion machinery is widely used in the forming of seals.

For O-rings, the traditional production method is molding, but with the development of extrusion technology, extrusion vulcanization integrated production lines are now widely used. The rubber material is extruded into a circular strip through the extrusion machinery, and then continuously vulcanized (such as microwave vulcanization, hot air vulcanization) and cut into O-rings of different sizes. This production method has high production efficiency, uniform product size and good consistency, and is suitable for mass production.

For oil seals and gaskets with complex shapes, special-shaped dies are used in extrusion machinery to extrude the rubber material into the required shape, and then vulcanized and processed. The extrusion machinery can ensure the shape accuracy of the seal through the precise design of the die, and the uniform plasticization of the rubber material ensures the sealing performance of the product. In addition, the extrusion machinery can also be used to produce seal strips (such as automotive door and window seal strips), which are extruded into long strips of specific shapes, and then cut and processed according to the required length.

Rubber profiles are widely used in construction, automotive, aerospace and other fields, such as door and window seals, automotive body profiles, shock absorption profiles, etc. Rubber profiles have various shapes and sizes, and the requirements for dimensional accuracy and surface quality are high. Rubber extrusion machinery is the main equipment for the production of rubber profiles.

In the production of rubber profiles, single-screw or twin-screw extruders are used, and special-shaped dies are designed according to the shape of the profile. The rubber material is extruded through the die to form the initial shape, and then cooled and set by the cooling system to maintain the shape and size of the profile. The traction system pulls the profile at a constant speed to ensure the uniformity of the profile length and cross-sectional size.

For rubber profiles with complex cross-sections (such as automotive door and window seal strips with multiple cavities), the die structure is relatively complex, and the extrusion machinery needs to have stable extrusion pressure and speed to ensure that the rubber material can be fully filled into each cavity of the die. In addition, the surface quality of the profile is also an important index. The extrusion machinery can improve the surface smoothness of the profile by optimizing the die structure and adjusting the extrusion temperature.

In addition to the above products, rubber extrusion machinery is also widely used in the production of other rubber products:

• Rubber sheets: Single-screw extruders are used to extrude the rubber material into sheets of different thicknesses, which are used for gaskets, conveyor belts and other products. The extrusion machinery can adjust the thickness of the sheet by adjusting the die gap and traction speed.
• Rubber cables: The rubber insulation layer and sheath of cables are extruded by extrusion machinery. The extrusion machinery needs to have stable temperature control to ensure the insulation performance of the cable.
• Recycled rubber products: Rubber extrusion machinery can be used to process recycled rubber into various products (such as rubber tiles, rubber hoses), which realizes the recycling of rubber resources and reduces environmental pollution.

In the practical application of rubber extrusion machinery in rubber product production, some problems often occur, which affect the production efficiency and product quality. The common problems and corresponding solutions are as follows:

The main reasons for uneven product size are unstable feeding speed, inconsistent extrusion pressure, improper die design, and uneven cooling. The solutions are: optimize the feeding system, ensure stable feeding speed; adjust the extrusion speed and temperature to keep the extrusion pressure stable; improve the die design, ensure the uniform flow of rubber material in the die; check the cooling system, ensure uniform cooling of the product.

The surface quality of products is often affected by factors such as insufficient plasticization of rubber materials, excessive die temperature, and impurities in the rubber materials. The solutions are: adjust the extrusion temperature and screw speed to ensure sufficient plasticization of the rubber material; reduce the die temperature to avoid the rubber material sticking to the die; strengthen the pretreatment of the rubber material, remove impurities and foreign bodies in the material.

In the production of multi-layer rubber products (such as rubber hoses), the bonding failure between layers is a common problem, which is mainly caused by insufficient temperature of the bonding surface and impure rubber material. The solutions are: increase the temperature of the bonding surface to improve the bonding strength; strictly control the quality of the rubber material, avoid mixing impurities; optimize the extrusion process to ensure the close contact between the layers.

The screw and barrel of the extrusion machinery are easy to wear after long-term use, which affects the extrusion effect. The solutions are: select wear-resistant materials (such as alloy steel) for the screw and barrel; regularly maintain and lubricate the equipment to reduce wear; control the particle size of the rubber material to avoid excessive wear caused by hard impurities.

With the continuous development of the rubber industry and the increasing requirements for product quality, energy conservation and environmental protection, rubber extrusion machinery is developing in the following directions:

• Intelligentization: The integration of intelligent control systems, such as Internet of Things, big data and artificial intelligence, can realize real-time monitoring and adjustment of equipment parameters, predict equipment faults, and improve the automation level and operation efficiency of equipment.
• High efficiency and energy saving: By optimizing the screw structure, improving the heating and cooling system, and adopting energy-saving motors, the energy consumption of the equipment is reduced, and the extrusion speed and production efficiency are improved.
• Specialization and customization: According to the production needs of different rubber products, specialized extrusion machinery and dies are developed to meet the personalized requirements of products.
• Green environmental protection: The development of environmentally friendly extrusion technology, such as the recycling of waste gas and waste water, and the use of environmentally friendly rubber materials, reduces the impact on the environment.
• Integration: The integration of mixing, extrusion, vulcanization and other processes forms a complete production line, which reduces the floor space of the equipment and improves the production efficiency.

Rubber extrusion machinery, as a key equipment in the rubber product manufacturing industry, has the advantages of high production efficiency, stable product quality and strong adaptability, and is widely used in the production of tires, rubber hoses, rubber seals, rubber profiles and other rubber products. It plays an important role in improving production efficiency, ensuring product quality and promoting the development of the rubber industry.

In practical application, we need to solve common problems such as uneven product size, poor surface quality and bonding failure according to the characteristics of different products and production processes, so as to ensure the stable operation of the equipment and the qualified rate of products. With the continuous development of intelligent manufacturing and green environmental protection, rubber extrusion machinery will develop towards intelligentization, high efficiency, energy saving and specialization, and will play a more important role in the high-quality development of the rubber industry.