Abstract: This paper introduces the design and application of pneumatic control components in a skein-winding machine, and discusses the main problems solved by the application of pneumatic control components in the HXFA368 skein-winding machine.
1. Introduction:
With the rapid development of technology, the textile machinery manufacturing industry has also ushered in a revolutionary development. The current development characteristics of textile machinery equipment are mainly reflected in the widespread application of touch-screen human-machine interfaces (HMIs), programmable logic controllers (PLCs), and various pneumatic control components. Currently, continuously improving the automation level of textile machinery equipment to reduce the labor intensity of operators and increase the production efficiency of textile mills has become an important R&D and design principle for textile machinery manufacturers. The realization of automated actions generally requires the use of PLCs to control solenoid valves and cylinders, among other actuators. The sliver-drawing and rapier combination machine is one of the most efficient pieces of equipment in the combing preparation process of pre-spinning. The automated actions of the HXFA368 sliver-drawing and rapier combination machine are achieved through compressed air driving cylinders, and the compressed air is controlled by a PLC-controlled solenoid valve. The HXFA368 sliver-drawing and rapier combination machine uses Airtac's solenoid valves and cylinders to achieve the execution of automated actions.
2. Application Design
2.1 Overview of the pneumatic control system of the HXFA368 strip-winding machine
A typical pneumatic system consists of a directional control valve, pneumatic actuators, various pneumatic auxiliary components, and air purification components. The HXFA368 strip-winding machine uses Airtac solenoid valves, cylinders, pressure gauges, and pipe fittings as standard equipment. The main air supply enters the main air path after passing through a three-piece assembly. Each solenoid valve controls the on/off flow of compressed air in its corresponding action unit. The solenoid valves are logically controlled by a PLC controller. The selection of cylinders is determined based on the specific mechanical action, and the cylinder speed is adjusted using a corresponding throttle valve.
2.2 Overview of the Operation Flow of the HXFA368 Strip-Winding Machine
Partial operation flow chart of HXFA368 strip-winding machine:
HXFA368 Strip-Winding Combined Machine Partial Operation Flowchart
When the set cotton web length is reached, the main motor of the HXFA368 sliver-winding machine switches to low speed, the electromagnetic clutch disengages and breaks the cotton web, the main motor stops, and the cotton frame rises rapidly. When it reaches the set position, the clamping plate opens, the cotton frame pauses at the highest position, the front door opens, and the cotton roll is pushed after the front door opens. After the cotton roll is pushed out, the pushing mechanism returns, and after the pushing mechanism returns, the front door closes. After the front door closes, the cotton roll frame quickly descends to the lowest position, and then proceeds to the upper empty tube step. After the cotton roll is pushed out, the action of flipping the cotton roll onto the trolley is performed. After the flipping mechanism returns, the trolley moves forward one step, and the pushing mechanism returns.
The HXFA368 skein and coil machine achieves all its actions through pneumatic actuators. In a pneumatic control system, the element that converts the pressure energy of compressed air into mechanical energy to drive the mechanism in linear reciprocating motion, oscillating motion, and rotary motion is called a pneumatic actuator. In the skein and coil machine, solenoid valves control cylinders to perform the actions, and the operation of the solenoid valves is controlled by a PLC. In this equipment's control system, a DVP60ES PLC from Delta Electronics Co., Ltd. is used to control the entire system; the solenoid valves and cylinders are all products from Airtac Co., Ltd.
2.3 Implementation of Automatic Operation of HXFA368 Strip-Winding Combined Machine
The HXFA368 sliver winding machine features a high degree of mechatronics integration. Its main power comes from an 11KW variable frequency motor, which achieves variable frequency speed control. The various steps are mainly controlled by solenoid valves that control compressed air to drive cylinders. Actions such as loading and unloading empty tubes, turning cotton rolls, raising and lowering the cotton roll support, pushing cotton rolls, trolley forward movement, opening and closing the front protective door, dropping empty tubes from the empty tube bin, and raising and lowering the empty tube delivery mechanism all correspond to the respective solenoid valves and cylinders. The coordinated operation of the entire machine is controlled by a PLC controller, which will only be briefly outlined here.
2.4 Overview of PLC Programming for Controlling Solenoid Valves
The various automatic actions on the HXFA368 strip-winding machine are achieved by using a PLC to control solenoid valves. Below is a step program that controls some of the actions.
In the program:
S41 controls the "air delivery tube rising" process. X17 is the rising limit position detection point for the air delivery tube mechanism. X30 is the left closing position detection point for the cotton roll clamping plate, and X31 is the right closing position detection point for the cotton roll clamping plate. Relay M131 controls the rising action of the air delivery tube mechanism. The first line of the program executes the rising action of the air delivery tube mechanism in the S41 step program step when the air delivery tube mechanism has not risen to the rising limit position and neither the left nor right clamping plate is in a closed state. The second line of the program uses relay M132 to control the falling of the air delivery tube mechanism. The second line of the program executes the falling action of the air delivery tube mechanism in the S41 step program step when the air delivery tube mechanism has risen to the rising limit position. The third line of the program executes the S42 step program segment, i.e., the clamping plate rising 1mm step segment, when the air delivery tube mechanism has risen to the rising limit position.
S42 controls the "clamping plate rises 1mm" process. X16 is the detection point for the lowering limit position of the air delivery tube mechanism. The instruction implemented in the fourth line of the program is to reset the lowering action of the air delivery tube mechanism when it is reset. The instruction implemented in the fifth line of the program is to control the corresponding solenoid valve through Y7 to achieve the control of the cotton roll clamping plate rising 1mm. X33 in the sixth line is the detection point for the cotton roll support rising 1mm and the lowering limit. The instruction implemented in the sixth line is to enter the S43 step program segment after the cotton roll clamping plate rises 1mm.
S43 controls the "clamping the empty tube after rising 1mm" process. The M129 relay in line 7 controls the release of the cotton roll clamp, and the instruction in line 7 resets the release action. The M124 relay in line 8 controls the closing of the cotton roll clamp, and the instruction in this line executes the command to close the cotton roll clamp. The instruction in line 9 enters the S44 step program segment when the left and right cotton roll clamps are closed.
S44 controls the process of "cotton roll support rising and empty tube falling". In the program on line 10, relay M513 implements the control function of holding the cotton roll support in the running state; relay M134 in line 11 implements the command to drop the empty tube from the empty tube compartment; line 13 executes the command to flip the empty tube after a 2-second delay. In line 14, X25 is the empty tube detection point at the spring plate. The command executed in this line is to enter the S45 program step segment when there is an empty tube at the spring plate.
S45 controls the "start after roll change" process, and line 15 executes the start-up low-speed operation control command.
The PLC coordinates the execution of each cylinder's actions by detecting the limit points of each automatic action. The cylinders are driven by compressed air controlled by solenoid valves, and the accuracy of the specific actions is determined by sensor detection. The cylinder's operating speed is regulated by adjusting the throttle valve.
2.4 Overview of Human-Machine Interface Programming for Controlling Solenoid Valves
To facilitate the separate debugging of various automatic actions on the HXFA368 skein and coil machine, a Delta DOP-AE10THTD human-machine interface was applied. The HMI allows operators to easily control each solenoid valve in real time, greatly simplifying the debugging of various automatic actions.
2.4.1 Interface design for controlling and adjusting the solenoid valve's actions via a human-machine interface on the HXFA368 strip-winding machine.
On this interface, the touch keys for actions such as opening the cotton roll clamp, pushing the cotton roll, and flipping the empty tube once control the corresponding solenoid valves. These solenoid valves control the compressed air, which in turn drives the cylinder piston, thus actuating the cylinder. During equipment commissioning, the operator first uses the touch keys on the setup interface to control the execution of single-step actions. Then, based on actual operational needs, the throttle valve is adjusted to regulate the cylinder's operating speed.
3. Common Faults and Solutions in the Pneumatic Control System of HXFA368 Strip Winding Machine
3.1 Solenoid valve malfunction
As an actuator controlled by a PLC controller, the solenoid valve is prone to two problems due to the long-term 24-hour operation of cotton textile equipment: incomplete engagement or complete damage. In the HXFA368 sliver winding machine, incomplete engagement manifests as intermittent operation, leading to intermittent equipment shutdowns. In this situation, it's difficult to determine the valve body damage when inspecting a single solenoid valve; a comprehensive assessment based on the specific circumstances is necessary. In the case of a completely damaged solenoid valve, the fault manifests as a failure to perform a certain action. In this case, replacing the corresponding solenoid valve can resolve the problem.
3.2 Sensor Failure
During the automatic operation of equipment, sensors are needed to perform limit detection on the cylinder's movements so that the PLC can logically coordinate and control the automatic actions. Generally, two types of sensors are used: magnetic induction sensors and proximity switches. If a sensor fails, the automatic operation will stop at a certain position and not continue to the next step. In such cases, the damaged sensor should be located and replaced based on the observed automatic operation.
3.3 Cylinder failure
As an important actuator, the cylinder often experiences air leakage from the piston inside due to prolonged operation. In this case, the cylinder will not move after compressed air is supplied, or the moving force and stroke will not meet the requirements. In such cases, the damaged cylinder should be repaired or replaced.
4. Conclusion
The HXFA368 sliver-drawing-rapier combination machine is a highly automated cotton textile equipment. This high-efficiency machine prepares the combing process in the pre-spinning section of cotton textile enterprises. Through years of improvement, its overall performance and efficiency have been enhanced, making it a complete replacement for similar foreign machines, such as the E32 and E35 sliver-drawing-rapier combination machines produced by Rieter of Switzerland, at only about one-third the price, saving the country a significant amount of foreign exchange. Currently, the HXFA368 sliver-drawing-rapier combination machine is widely used in many cotton textile enterprises in Shandong, Hebei, Henan, Shaanxi, Gansu, and Hunan provinces, and its excellent performance has been unanimously praised by users.
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