Foreword
In recent years, the rapid development of the transportation industry, particularly in heavy-duty trucks and commercial vehicles, has increased the demand for truck tires, stimulating the development of radial truck tires. Furthermore, in the repair market, customers have tangibly experienced the benefits of radial tires, especially in long-distance, high-volume transportation, highlighting their advantages. Therefore, not only has the market for replacement radial truck tires expanded, but the replacement of bias-ply tires with radial tires has also accelerated. The production of all-steel radial truck tires has experienced unexpectedly rapid growth, leading to a surge in demand for all-steel radial truck tire production equipment and increasingly higher requirements for the forming efficiency and quality of tire forming machines. In response to this trend, a new type of two-strand all-steel radial truck tire forming machine has been developed, significantly improving in terms of automation, forming quality, and forming efficiency. The structure, features, and main performance parameters of this equipment are described below.
1. Composition and characteristics of molding machine equipment
The LCZ-PB type forming machine consists of one main unit, four feeding racks, one electrical control system, and one pneumatic system. The main unit includes a tire unloading and bead-fastening device, a mechanically reverse-wrapping forming drum, a main shaft box, a transfer ring, an auxiliary drum, an auxiliary drum transmission box, a rolling device, and a dial indicator system. It is used to bond the tread and carcass components, assemble, shape, roll, form, and unload the tire, completing the entire tire blank forming process. The carcass feeding rack automatically supplies the inner liner, sidewall pre-composite components, bead wrapping fabric, and carcass steel cord fabric to the forming drum. The belt layer feeding rack is located behind the auxiliary drum, and the tread feeding rack is located in front of the auxiliary drum, used to bond the belt layer material and carcass fabric to the auxiliary strand. There is also a gasket feeding rack located in front of the forming strand, used to guide and bond the gasket. The electrical control system consists of an electrical control cabinet with a PLC as the main control unit and control panels. Each control panel is equipped with a touch screen and uses PROFIBUS-DP fieldbus for communication. It has functions such as communication, process program editing, process parameter modification, fault monitoring, fault self-diagnosis, and fault display. The pneumatic system adopts a distributed structure, with pneumatic control units installed on-site at components such as the main unit, main feed rack, and belt layer feed rack to directly drive the operation of each component.
1.1 Features of Molding Machine
(1) The use of mechanical drums for bonding and molding is a domestic first (patent pending), which helps to improve efficiency and reduce maintenance;
(2) Adaptable to large rolls. By selecting the appropriate specifications, the tire forming specifications can be extended down to R16 all-steel light truck tires;
(3) The whole machine has been optimized, which has improved the iron content, speed and forming efficiency;
(4) Multi-turn encoders (absolute) are used for important position control;
(5) The inner lining of the main feeding rack is pre-composite to the tire sidewall inside the machine and cut by ultrasonic cutting blade;
(6) The main feeding rack adopts infrared correction technology and camera correction technology;
(7) Modular design allows users to choose from multiple options;
(8) The pneumatic system is equipped with a central capsule pressure terminal detection and alarm display;
(9) The overall design adopts a large number of linear guides, circular guides, ball screws, bevel gears, reducers, fiber optic photoelectric controllers, diffuse reflection photoelectric switches and other advanced complete sets of accessories;
(10) Install edge safety switches and pull-wire switches to ensure safe operation.
1.2 Technical Parameters
The diameter of the formed tire bead is 17.5-24.5 mm. The width of the formed tire blank is 122.5-450 mm. The maximum diameter of the transfer ring can transfer tires is 1230 mm. The range of tire specifications is 7R17.5-12R14.5-315-80R24.5-12.00R20/12.00R24. The minimum outer diameter (including tread) of the standard tire is 740 mm. The maximum outer diameter (including tread) of the standard tire is 1230 mm. The standard auxiliary drum diameter is 830-1160 mm. The standard auxiliary drum width is 450 mm. The maximum auxiliary drum speed is 22 r/min. The maximum forming drum speed is 150 r/min.
2. Molding machine structure and principle
2.1 Host
2.1.1 Mechanical Drum
The structure of the mechanical forming drum is shown in the figure. The middle drum has a foldable three-layer structure. The cylindrical surface formed by the top surface of the finger-shaped reverse wrapping single-row reverse wrapping rods serves as the material-applying surface for the side drums. It features 24 fan-shaped fast and ring-shaped double-acting cylinders, with the panel/program setting controlled by pneumatic pressure. Using a mechanical forming drum improves the production efficiency of the forming machine, reduces maintenance time, and decreases the need for forming drum spare parts.
2.1.2 Spindle box
An AC servo motor achieves the rotation of the forming strand and the movement of the drum shoulder through switching between an electromagnetic clutch and an electromagnetic brake. The rotation speed and angular position of the forming strand are controlled by the servo motor and an encoder. The movement of the drum shoulder is controlled by a differential mechanism and an absolute incremental encoder. The drum shoulder movement has an overload protection function. An 8-way rotary valve supplies air to the forming drum.
2.1.3 Auxiliary Drum
The auxiliary drum consists of 12 sector-shaped blocks, and its opening and closing are achieved using a double-acting cylinder, connecting rod, and slider mechanism.
2.1.4 Auxiliary Drum Transmission Box
The auxiliary track's rotation and accurate angular positioning are achieved by an AC servo motor, encoder, reducer, and a set of synchronous pulleys. 2.1.5 Tread Transmission Ring
The clamping and releasing action of 12 sector blocks is achieved by using a locking cylinder and a swing arm mechanism, and the blocks are automatically positioned according to the table size.
2.1.6 Snap-ring transfer ring
A cylinder-linkage mechanism drives four clamping jaws to swing and grip the tire bead. The swing position (diameter) of the clamping jaws can be manually adjusted. The transfer ring is clamped by a cylinder, and the spacing is automatically positioned.
2.1.7 Rolling device
The static pressure roller is driven by a cylinder to extend and retract to roll the table surface. The dynamic pressure roller uses a floating rolling wheel to achieve tire shoulder rolling. Front and rear rolling is driven and controlled by an AC servo motor-ball screw-encoder; left and right rolling is driven and controlled by an AC servo motor-ordinary screw-encoder; oscillating rolling is driven and controlled by an AC servo motor-worm gear-encoder; and front, rear, left and right movement uses a linear guide structure.
2.1.8 Tire unloading and bead pre-positioning device
This component adopts a gantry structure and can be driven by a motor to complete the tire removal and tire bead installation operations.
2.1.9 Tail-end tip device
The component is moved in and out using a power push rod. If the tail tip is not in position, the main drum cannot function. Alternatively, a cylinder can be used to move the support plate in and out. The semi-circular groove engages with the end of the main drum.
2.1.10 Bed frame
The bed is welded from high-quality steel and equipped with linear guide rails.
2.1.11 Rubber Pad Feeder Rack (can also function as tire sidewall feeding rack)
The feed rack is installed separately, independent of the main drum drive box. The centering, width adjustment, and spacing adjustment mechanisms employ mechanical control. This structure allows for a clear view in front of the main unit, facilitating operation and maintenance.
2.2 Feeding rack
The tire carcass feeding system is used to bond the inner liner/sidewall composite, tire carcass steel cord fabric, and bead wrapping fabric to the delivery and forming drum. It employs infrared and camera-based alignment technology from BST (Germany) to automatically center the semi-finished components during conveying and bonding, meeting the specific requirements of the forming process. The inner liner and sidewall use EPC alignment. The steel cord fabric uses mechanical alignment. The inner liner and sidewall are bonded in-machine, automatically length-determined, ultrasonically cut, and manually joined. The cord fabric is automatically length-determined and cut with a hot disc cutter. The cutting angle of the inner liner/sidewall composite and steel cord fabric is 0 degrees between it and the drum spindle.
The characteristics of ultrasonic cutting of the inner liner and sidewall pre-composite components are as follows:
(1) The ultrasonic cutting system of BRANSON, USA, is selected. The maximum kerf width is 40mm and the cutting angle is 15-22 degrees.
(2) Cutting is performed by driving the blade to generate reciprocating vibration of about 40KHz through high-frequency ultrasonic waves, and the ultrasonic vibration is used to directly tear the rubber polymer.
(3) High-frequency vibration cutting can prevent rubber from sticking to the cutting blade, and the friction heat can help the rubber sheet adhere to the molding drum to form a joint during molding, which is beneficial to improving the molding quality.
(4) Follow the principle of cutting thinner pieces quickly, cutting thicker pieces slowly, and cutting the feed even slower when the feed is coming in. The blade should be given enough cooling time during the cutting interval (90 seconds followed by a 30-second pause). The advantage of this cutting method is that the cross-section is flat, smooth, and wide, without any semi-vulcanized rubber particles. This feed rack can be equipped with a manual feed rack structure.
3. Control System Design
3.1 System Overview
The system consists of a PLC, a touch screen, and servo drives. It employs a popular control mode, using the PLC, PROFIBUS fieldbus, and distributed input/output stations to control the equipment. The touch screen provides human-machine interface functionality and displays status and troubleshooting information. Servo drives enable rapid group positioning. The PLC operates at high speed. The touch screen offers rich information; the servo system boasts powerful functions.
3.2 System Configuration and Functions
The PLC, distributed input/output stations, and servo systems form a control network via PROFIBUS and MPI, providing process parameters. The PLC sends parameters and start commands to the servo drive system and other actuators based on operator instructions and monitors their execution. It provides accurate troubleshooting information in case of improper operation or actuator malfunction. The molding process settings utilize an industrial computer for control, featuring parameter setting, program editing, status display, fault indication, and network expansion capabilities, making setup convenient.
3.3 Pneumatic System
In the pneumatic system, the central capsule and rolling rollers are controlled by proportional valves, and the pressure can be programmed, which is simple and reliable.
4. Modular design of molding machine
4.1 Security
Moving parts are equipped with edge safety switches and painted with movement warning paint. Warning lights are installed on the transfer rings and retaining rings. Tread and rubber pad feeding racks, which pose direct danger to personnel, are equipped with safety switches and automatic stop functions during operation to ensure operator safety. Emergency stop buttons are installed on all critical parts of the equipment. In the event of a safety problem or emergency stop, the entire machine will automatically stop. Normal operation can only resume after all faults have been eliminated and confirmed.
4.2 Reliability
We use high-quality outsourced components and strengthen the re-inspection of critical parts to ensure their reliability. We simplify mechanical structures to reduce equipment failure points and the likelihood of malfunctions. Components already in mass production are purchased outsourced or custom-made to reduce defective products from single-piece production, including various guide rails, gears, sprockets, lead screws, and conveyor rollers.
4.3 Maintainability
Improve equipment reliability and reduce maintenance workload. Simplify mechanical mechanisms to simplify equipment maintenance. Implement automatic fault diagnosis functions and provide automatic maintenance prompts, enabling maintenance personnel to quickly and accurately troubleshoot problems.
4.4 Modular Design
The equipment adopts a modular design. Within each feeding rack, the loading trolley, drive unit, conveyor, cutting mechanism, and bonding template form independent modules. By changing these configurations, it can adapt to the different configuration requirements of different users and processes. In the overall machine solution, many components offer two or more selectable options, providing choices for users with varying needs.
5. Conclusion
The LCZ-PB all-steel radial truck tire forming machine has been put into use in many tire factories, fully meeting various user requirements. In particular, the innovative use of a mechanical reverse-wrapping forming drum has greatly improved tire forming quality and efficiency, making it another mainstream option in the market for two-drum all-steel radial truck tire forming machines.
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