Author Information: Cherry Tan, Chief Engineer Consultant of Tire Industry from ICONVEY Overseas Business Department
Reasonable structural design, formula design, high-quality raw materials and scientific process conditions require high-precision production processes. It is necessary to form a relatively complete production line and special auxiliary equipment from the production process equipment to ensure that the production process technology is advanced, strict, scientific and reasonable. Otherwise, no matter how good the design is, the quality and precision of tire processing cannot be guaranteed. If the production process is not well controlled, it is impossible to have good product quality.
The production process mainly includes: rubber compound preparation, fiber cord calendering, extrusion of various types of rubber, steel cord calendering, cutting, bead ring manufacturing, tire molding, vulcanization, white sidewall grinding and spraying of protective liquid, and finished product testing. The main processes are now introduced as follows:
1. Preparation of rubber compound:
The mixing process is an important link in the production of radial tires. The radial tire compound is characterized by a large amount of carbon black filling, high hardness of the compound, many additives added, and difficulty in mixing.
According to different rubber material requirements and formula characteristics, the determined mixing process is different. The mixing process is divided into masterbatch and final batch. The masterbatch is usually divided into one-stage masterbatch, two-stage masterbatch or three-stage masterbatch. The larger the amount of carbon black, the more stages of mixing. In the entire rubber compound preparation process, it is necessary to ensure that the two aspects of the process are effectively controlled, one is the weighing system, to ensure that various formulations of rubber and additives and other materials are accurately weighed, and the other is to require the mixing process. The process parameters such as medium temperature, time and power are effectively controlled, and these parameters directly affect the quality of the rubber compound. At present, the weighing and conveying of various materials and the process parameters of the production process basically adopt an automatic weighing system, which is automatically controlled by a computer to ensure the quality of the rubber compound.
The mixing system generally includes:
Small material automatic weighing system
Carbon Black Storage Tank and Weighing System
Process oil storage tanks and weighing systems
Barrier Fluid Storage Tanks and Circulation Systems
Upper Auxiliary Control System
Lower auxiliary system
The internal mixer used for master batch mixing generally has large capacity and high efficiency, such as PX-420 internal mixer, GK400, etc., and its auxiliary machine is screw extruder; the internal mixer used for final rubber mixing is GK255 internal mixer Machine, GK270N internal mixer, the auxiliary machine is open mixer, mainly to ensure that the temperature of the rubber material can be reduced as soon as possible.
Internal mixer is the most important equipment for rubber compound mixing. According to the different rotors, mixers can be divided into many types.
ZZ2 rotor has the characteristics of low rubber discharge temperature, high efficiency and good dispersion. Its rubber mixing performance is better than other types of internal mixers, especially suitable for the final mixing of radial tire rubber.
4-Wing is a quadrilateral tangential rotor, which has a large filling coefficient and energy input. Since the rubber material gets the most sufficient flow in the mixing chamber, it has a high rubber output and rubber mixing quality.
PES3 meshing rotor has a wider edge, which can make the rubber material continuously update the rubber surface along the spiral edge, and can eliminate the stagnation area with small flow. Uniform mixing, low temperature rise, suitable for refining various rubber compounds and plastics with high quality requirements.
Features of Internal Mixer
All parts in contact with the rubber material are cooled by water circulation, the cooling area is large, and it is equipped with a water temperature adjustment system controlled by constant temperature. Selecting the appropriate water temperature can effectively ensure the stable quality of various rubber materials.
The transmission system adopts DC motor stepless speed change and AC motor, and the speed reducer has various forms of gear shifting. And high-precision hardened surface reducer and drum gear coupling. The whole machine has the advantages of stable transmission, low voice and long life.
The control system adopts PLC, with manual and automatic functions, easy to switch, can realize time, temperature, energy control, and has perfect signal detection, feedback and safety protection, more effective control of rubber mixing quality, shorten auxiliary time, reduce labor strength.
The mixing process strictly controls the weighing of various raw rubber, carbon black and chemical additives within the tolerance range. The final rubber compound must pass the rapid inspection items such as sulfur change meter, Mooney viscosity, hardness, density, etc. and the inspection of mechanical and physical properties. , The adhesive compound should also be tested for its adhesive properties, and it can be put into use only after passing the test.
2. Extrusion process
The extrusion process is the preparation of semi-finished products such as treads, sidewall grommets, and rubber cores. The extrusion production line is divided into two compound extrusion line and three compound extrusion line. The system consists of extruder (also called main machine) and auxiliary line.
According to the performance characteristics of the rubber compound and the extrusion requirements, the extruder is also divided into two types: cold feeding and hot feeding.
The extrusion production line includes devices such as glue supply, extrusion, compounding, cooling, length-fixing, weighing and cutting. During the extrusion process, the size of the glue supply is stable and continuous, and the speed of the main machine and various pressures are kept stable to ensure that the extruded products are uniform. At the same time, the extrusion temperature should be strictly controlled to ensure the performance of the semi-finished product surface and avoid scorch and performance degradation caused by excessive temperature.
The extrusion of the white sidewall is designed with a special pre-mouth plate to ensure the stability of the size, the film is automatically attached, the attachment is tight, and the positioning is accurate. At the same time, strict on-site management ensures that the white glue is not polluted.
3. Fiber cord calendering
The fiber cord calendering adopts a four-roll calender. The purpose of the cord calendering is to attach the rubber material to the cord through the calender. The four-roll calender is composed of curtain fabric guiding, splicing, pulling, drying, calendering, cooling and coiling.
Different tensions are used in each area, and the thickness, temperature and tension of the calendering are automatically controlled to ensure the quality of the calendering.
Calendering adopts hot-melting and supplying glue, 4 sets of XK-660 open type rubber mixing machine to ensure that the rubber material is heated evenly, the temperature of the glue supply is suitable, and the size is stable. The calendering production line is imported from the Italian RODOLFO company, which automatically adjusts the calendering tension, automatically detects the moisture content of the cord, and automatically measures the thickness of the calendered cord through the ray system and adjusts it at any time, ensuring that the calendering accuracy meets the needs of the production of semi-steel radial tires.
4. Airtight layer calendering process
The airtight layer calendering production line and the film are manufactured by a four-roll calendering production line, and the cold-feed extrusion production machine is used to supply the glue. It is required that the calendered film has a smooth surface and stable width, thickness and differential.
5. Steel cord calendering
The steel cord calendering production line is similar to the fiber cord calendering, and also uses a four-roll calender. The purpose of the calendering is to attach the rubber material to the steel cord through the calender. The steel cord four-roll calender is manufactured by the Italian COMERIO steel wire calender. The production line mainly includes spindle house, main engine, cooling, coiling device and so on.
The spindle room is equipped with temperature control and humidity control devices, which strictly control the temperature and humidity, so as to avoid the rust of the steel wire and the excessive moisture that will affect the bonding.
Compared with the calendering of fiber cords, ① because the steel cords are arranged by the steel wires of the spindles, and there is no weft, the density of the cords is realized by the warping rollers, and the density is uniform, avoiding the occurrence of thin lines and jumpers. Calendering is an important control content, otherwise it will not only affect product quality but also cause great waste. ②The calendered steel wire with rubber cord should be rolled with plastic pad to ensure the freshness of the surface of the cord.
The steel cord is cut by the German FISCHER cutting machine. The main requirements are that the cutting size error is small and the precision is high.
6. Fiber cord cutting
The polyester cord fabric is a semi-finished product that is cut into a certain width and a certain angle by the cutting machine after calendering the fiber cord fabric according to the process requirements. A horizontal cutting machine specially used for the production of radial tires is used. The cord fabric should avoid stretching and deformation during the cutting process. It is necessary to ensure the size and angle of the cut cord and the size and quality of the joint.
7. Manufacture of traveler
The manufacture of the traveler is to roll the steel wire into a traveler after being glued. Including the steel wire station, extruder, material storage, winding machine and other parts. Semi-steel radial tires generally use side-by-side winding beaders. In the preparation of the traveler, attention should be paid to the surface quality of the steel wire, whether the glue is uniform, exposed copper, and whether the steel wire wrapped around the traveler is neatly arranged; , stored as required, and used in sequence.
8. Forming process
The molding process is a process in which various semi-finished products are formed into embryos through a molding machine, and is an important process in tire production. At present, the forming of semi-steel radial tires is divided into primary method and secondary method.
The secondary molding machine molding is divided into one-stage molding and two-stage molding. A tire is made up of one section and two sections, so it is called a group. One-stage molding includes feeding rack feeding, mechanical buckle, capsule reverse wrapping, pressing, etc. The process quality requires strict control of the size, weight and joint accuracy of each plastic component, and the weight of each component is staggered according to the specified position to improve the quality of the process. Uniform performance of tires.
The second-stage molding is to press the belt layer and the tread on the forming drum with a cloth supply frame, transfer it to the capsule-free machine head with a clamping ring, and then compact it with a pressing roller. Strictly control the inflation time, pressure and roller pressure to ensure the stability of the outer edge of the embryo.
In the past few years, the tire industry’s demand for improving tire quality and increasing its variety has increased significantly, and tire companies have to develop a new product for almost every new type of vehicle.
The more varieties of tires, the shorter the production cycle of each type of tire. Therefore, the requirement for flexibility is becoming more and more important; that is, flexible planning and organization of production. Just-in-time production is also increasingly common in the automotive industry. Due to the high quality requirements of tires and the rising wage costs, tire manufacturers must reduce their manufacturing costs if they want to remain competitive. All these factors have led to the design of new tire building machines specifically for today’s technologically advanced tire production plants. Such as the “(P1+2) one-shot molding machine” designed by Krupp, the 2020 molding machine of VMI company in the Netherlands, etc.
The principle is that the belt laminating device and the carcass forming device are connected by a transfer mechanism, and a transfer ring transfers the parts from one drum to another drum. The feeding device is located at the front and rear of the machine and is responsible for conveying various materials and components.
In the previous molding machine, all working steps, such as material unwinding, cutting to length, handling, centering and splicing, were all manual operations. The one-shot molding machine is almost all automatically controlled. Therefore, the one-shot tire building machine can be operated by only one builder whose main task is to supervise the function of each unit. Therefore, this kind of building machine requires much lower physical strength than previous building machines, and the quality and output of tires are less affected by the operation of the builders.
Take the Krupp P1+2 one-shot forming machine for forming car tires and light truck tires as an example. This molding machine is suitable for tires of various structures with bead sizes ranging from 12 to 16 inches. Such as single and double ply tires, tires with or without crown plies and/or crown strips, tires with sidewall treads or tires with sidewall treads, etc., can be formed by the same molding machine. Even in small batches.
A one-shot building machine consists of several different units that can be configured to meet the requirements of the final production, as shown in the Krupp tire building machine. In order to successfully build high-precision tires, Krupp tire building machines are assembled from precision components with tight tolerances, which are precisely centered during installation. Good machine design means that the equipment remains rigid and stable in a factory environment, maintaining its original tolerances after years of temperature extremes and routine maintenance.
Vulcanization is the last step in the tire production process except for testing. Through vulcanization, the molded tire is turned into a finished tire, and the rubber compound is turned into a material with various characteristics through vulcanization.
Radial tires are vulcanized using a dual-mode vulcanizing machine. It has the functions of automatic tire loading and unloading, and the single-board machine controls the vulcanization process, which reduces human operation errors and ensures the quality of tire production. Before vulcanization, pay attention to the inspection of the tire blank, and there must be no quality defects such as impurities, bubbles, and folds. Strictly control the shaping pressure, height and time; ensure the stability of the vulcanization time, temperature and pressure.
At present, the vulcanization method is distinguished according to the different medium of vulcanization internal temperature. Regardless of the method, the external temperature (or the hot plate temperature, the mold temperature) is a certain pressure of steam, but the temperature is high or low.
Hot water vulcanization—The water is heated and superheated by steam.
Steam vulcanization—a saturated state is formed by steam, that is, saturated steam is used as the internal temperature medium. Also known as high temperature vulcanization.
Nitrogen vulcanization – in the later stage of steam vulcanization, the vulcanization process is completed by nitrogen pressure holding. It is the current advanced vulcanization technology and meets the requirements of environmental protection (Welcome to discuss with Iconvey related engineers, you can send an email to email@example.com).
Nitrogen vulcanization system is very complex and technical content. ICONVEY will independently explain the knowledge in this field in the next issue.
Variable temperature vulcanization – in the later stage of steam vulcanization, the vulcanization process is completed by using superheated water as the internal temperature medium to maintain pressure.
10. Grinding of the white sidewall
The process of sanding the black cover glue on the white glue with a sander. The grinding machine has two sets of devices: rough grinding and fine grinding. By adjusting the operation steps and time of rough grinding and fine grinding, the best grinding effect can be achieved. After polishing, the white sidewall part is automatically sprayed with protective liquid, which is evenly sprayed and dried quickly, which improves the production efficiency and the appearance quality of the tire.
11. Tire testing and testing equipment
Inspect the appearance of the tire, mainly including exposed lines in the tire, unevenness, blistering in the tire, delamination, heavy skin, cracks, lack of glue, drawing of the bead ring, grinding and spraying effect of the white sidewall, etc.
X-ray machine is used to conduct internal quality inspection of tires, including belt deviation, poor grade, bead pull-up, looseness, tire impurities, delamination, etc. The inspection adopts a general-purpose X-ray non-destructive flaw detector, produced by Monsanto Company in the United States. Through the X-ray wavelength, the structural arrangement of the skeleton material used in the tire and other quality defects can be clearly seen on the screen.
Uniformity testing machine
The radial force, lateral force warp, lateral runout and taper of all radial tires were tested by a uniform testing machine, and the tire quality was graded.
The uniformity testing machines are mainly imported from Akron Corporation of the United States and Kobelco of Japan.
Dynamic balance testing machine
The dynamic balance test of the product is carried out with a dynamic balance testing machine.
The dynamic balance testing machine is imported from Micro-poise Company and Japan International Measurement and Measurement Company.
Tire performance test
Mainly carry out random inspection on tire durability, high-speed performance, strength, outer edge size, etc. Durability and high-speed performance The radial tire was tested by the TTM-3 high-speed performance testing machine of Akron Corporation of the United States.
The tire manufacturing industry chief engineer discussion group
At present, ICONVEY and its brother brand HONG’S BELT are deeply rooted in the field of tire manufacturing, and have jointly designed manufacturing processes and developed corresponding solutions for a large number of well-known tire manufacturing brands. Welcome international colleagues to join our tire industry discussion group, immediately send an email to firstname.lastname@example.org or email@example.com to apply for permission to enter the tire manufacturing industry chief engineer discussion group, and become friends with international bigwigs.