Delta Mechanical and Electrical Products Application in the Double Location
Printing Coating Machine
[Abstract] This article mainly introduces the application of Delta's electromechanical products in a dual-station printing and coating machine. Taking the actual debugging of a dual-station printing and coating machine as an example, it introduces the debugging principle, the integrated control structure of the system based on PLC, touch screen and frequency converter, tension control implementation, unwinding diameter calculation, etc.
【Abstract】This paper mainly introduces the sets of mechanical and electrical products
application in the double location printing coating machine, double location
printing coating machine commissioning is presented based on the principle
and system debug PLC and touch screen, a frequency converter to the integrated
control structure, and tension control realization, put volumes diameter calculations, etc.
[Keywords] VFD-VE inverter | Touch screen | Constant tension control | Winding diameter calculation | Dual-station unwinding device
【Keywords】 VFD-VE; touch screen; CANopen; printing machine; constant tension control; coil diameter computing; double location cloth-extending system
The dual-station printing and coating machine is mainly used for making tapes, reflective films, protective films, and applying colorants and chemicals to materials such as BOPP, PVC, and PET paper. Type A is mainly used for coating BOPP, PVC, PET, and paper—materials that do not stretch when heated—while Type B is used for materials such as PE that do stretch when heated. The dual-station printing machine uses a Delta frequency converter to control the speed and a Delta PLC system for automatic tension control. It employs wire roller coating or three-roll reverse metering doctor blade coating methods, ensuring uniform adhesive application and adjustable adhesive amount. Drying is achieved through electric heating or steam heating. The external view of the dual-station printing and coating machine is shown in Figure 1.
Figure 1. Outline view of the dual-station printing and coating machine
1. Application Introduction
The mechanical structure of a dual-station printing and coating machine can be divided into a dual-station unwinding section, a printing, coating and drying section, and a rewinding section. The main transmission points include the unwinding A-axis, the unwinding B-axis, the unwinding traction, the printing and coating shaft, the sprocket drive shaft, the main traction motor, and the rewinding shaft.
The working principle of a dual-station printing and coating machine is as follows: The paper or PE film to be processed is installed on the unwinding shaft A or B. After pre-tensioning the unwinding and rewinding rollers, the rollers are pressed down, and the main motor is started to feed the paper in the direction of paper feed. This causes the printing roller and pressure roller to press together, and the machine is started once the appropriate tension is achieved. Adjusting the position of the alignment roller can adjust the flatness of the paper. Adjusting the air pressure of the swing arm cylinder can control the tension of the paper or PE film. The unwinding shaft adjusts the film speed smoothly via the tension swing arm. The unwinding traction, coating and printing, and rewinding shafts all operate smoothly through feedback adjustment of the transmission point speed via the swing arm, thus achieving good printing quality and effect. The main technical parameters of the equipment are shown in Table 1 below.
Table 1 Main Technical Parameters
2. Control System List
HMI: DOP-B07S (7-inch)
Inverter: VFD110V43A-2 (11kW, Unwinding A)
VFD110V43A-2 (11kW, unwinding B)
VFD037V43A-2 (3.7kW, unwinding traction)
VFD022V43A-2 (2.2kW, printed coating roller)
VFD037V43A-2 (3.7kW, sprocket)
VFD037V43A-2 (3.7kW, main traction)
VFD037V43A-2 (3.7kW, rewind)
EMV-PG01O*7 (Encoder Card)
PLC: DVP-80EH2*1 (Main Unit)
DVP04AD*1 (Analog Input Module)
DVP04DA*2 (Analog Output Module)
3. Control System Structure Diagram
The control system is shown in Question 2.
Figure 2 Control System
3. Principle Analysis
The control technology of a dual-station printing and coating machine mainly focuses on the speed synchronization of multi-axis drives, the constant tension during winding, unwinding, traction, printing, and coating, the roll diameter calculation during unwinding, and the switching between the A and B axes of the dual-station unwinding process. Winding tension control is crucial; the winding tension should be appropriate. Too little tension will cause the paper to loosen during winding, while too much tension will cause the material to wrinkle. In this example, the unwinding tension swing arm provides feedback on its angle, thereby using PID control to adjust the unwinding speed to achieve constant tension and stable speed. Furthermore, since the diameter of the roll continuously decreases during unwinding, if the unwinding shaft speed remains constant, the unwinding linear speed will decrease, potentially causing the PE film to break. To address this issue, the unwinding drive control must perform roll diameter calculations to determine the baseline speed.
4.1 Closed-loop vector control mode of VFD-VE frequency converter
All variable frequency drive shafts in the system adopt a closed-loop vector control mode with encoder feedback. The reason for using the closed-loop vector control mode is to ensure that the speed control accuracy of the drive shaft is more accurate, faster, and more stable, and to avoid the linear velocity relationship of different speeds caused by motor slippage as much as possible.
4.2 Implementation Process
The four axes—unwinding, unwinding traction, coating and printing, and rewinding—all require a constant tension speed control mode. The process is as follows: First, the actual baseline linear speed of each axis is calculated electronically. Then, ±5% of the baseline linear speed is used as the allowable adjustment range for PID control. Next, the collected pendulum position and angle feedback is used as the PID feedback value to adjust the speed and maintain constant tension of each axis. After adjusting the PID parameters, the system can maintain speed stability even at the maximum speed of 65 m/min, with the pendulum swing amplitude not exceeding ±1%.
4.3 Winding Control
For unwinding and take-up control, there are two main aspects: speed control and constant tension control. Since the linear speed of the paper material is achieved through contact with the pressure rollers (preventing slippage), only the speed of the take-up motor needs to be controlled separately.
Since the actual size of the unwinding roller changes over time, its accuracy is crucial for the reference speed. Currently, two methods are commonly used: the thickness method and the linear velocity calculation method.
The principle of the thickness method is based on an understanding of the material thickness. For every revolution of the motor, the diameter of the winding roller increases by two material thicknesses, and the diameter of the unwinding roller decreases by two material thicknesses. This method is mainly used when the thickness of the winding and unwinding material is uniform. Its advantage is the accuracy of the calculated thickness value; its disadvantage is that the user needs to input the material thickness information into the inverter's relevant parameters.
The principle of linear velocity calculation is mainly based on the following formula: D=(G*V)/(π*n). Where D is the current roll diameter, G is the mechanical transmission ratio, V is the current linear velocity, and n is the motor speed. The current linear velocity can be acquired through analog signals or pulses. The advantage of the linear velocity calculation method is that it can be used in situations where the material thickness is uneven, eliminating the need to set the material thickness value and reducing the requirements for the operator. The disadvantage is that the calculated current roll diameter value is affected by the accuracy of the linear velocity acquisition; if the linear velocity fluctuates greatly, the current roll diameter value will also fluctuate greatly.
The calculated roll diameter is basically equal to the actual measured roll diameter. Therefore, the ±5% adjustment range of the PID control can also be calculated. To increase flexibility, the ±5% range can be expanded to ±15%, and the result is still quite ideal, ensuring that the normal fluctuation range of the tension swing arm is within ±1%.
Note: Do not calculate the roll diameter during acceleration and deceleration, because the target speed increases during acceleration and deceleration, while the speed follow-up of PID control is delayed. Therefore, try to avoid calculating the roll diameter during speed changes.
4.4 Calculation Process
When unwinding is running at low speed (0-5Hz), the error between the given speed and the actual output speed will inevitably be greater than ±15% due to factors such as motor slip. Therefore, the process requires that the PID adjustment range should be inversely proportional to the frequency of the drive shaft during operation (0-5Hz). The formula is: F=K/V, where F is the allowable adjustment range of the PID, K is a constant value, and V is the actual output frequency of the drive shaft. The actual allowable adjustment range F value obtained by this formula is: ±150%～15% (0～5HZ); ±%15 (5～50HZ).
By adjusting the PID fluctuation range under different speed output conditions, the high-precision PID speed control is fully satisfied in all situations, achieving both the small-proportion, large-amplitude characteristic at high speeds and the large-proportion, small-amplitude characteristic at low speeds.
4.5 Pre-tensioning function upon startup:
After the initial film loading and startup, the machine checks whether the angles of the take-up and unwind levers are in the tensioned position. If not, PID adjustment will be disabled during this stage, and the take-up and unwinding will proceed at a fixed speed. Once the take-up and unwind levers are determined to be within the specified angles, the speed will be switched back to PID control.
4.6 Unwinding dual-station switching,
When the current roll finishes unloading, a backup roll is pre-started (running at a fixed speed based on the set initial roll diameter). After manual reloading, the current roll is stopped, and the speed of the backup roll is switched to PID control mode, thus completing the dual-station unloading and reloading control process.
5. Parameter settings via touchscreen
The main screen displays the operating status of all drive shafts, the current unwinding diameter, linear speed, and the tension angle position of each lever, as shown in Figure 3. The parameter setting interface provides some process parameter data, as shown in Figure 4.
Figure 3 Main interface of the coating machine
Figure 4 Parameter Settings
6. Conclusion
Through debugging the dual-station printing and coating machine system, it was found that the machine can maintain constant tension and stable linear speed within a maximum speed control range of 0-65 m/min. In particular, the angular deviation of all four tension levers does not exceed ±1%, effectively ensuring product quality and high-speed production efficiency. The system has been well-received by the end customer. Another significant achievement is that the successful application of Delta's full range of products, especially the system composed of VFD-VE frequency converters and PLCs, in the printing industry has created a new landscape for Delta products and systems in the local printing industry.
