Abstract: In roll paper packaging machines, there is a problem of synchronous control during the feeding process. We propose a synchronous control scheme for the feeding process. We install a semi-circular metal plate on the drive shaft of the roll paper feeding system and attach a proximity switch probe to its side. By judging the output state of the proximity switch each time the photoelectric sensor detects a color mark, we can determine whether the packaging paper feeding system is lagging or leading the roll paper feeding system, thereby enabling the servo motor to rotate forward, reverse, or remain stationary, thus achieving synchronous control during the feeding process. Keywords: Packaging machine; Synchronous control; Submitting process Abstract: Synchronous control is a significant challenge in packaging machines. This project presents a new control scheme for the transmitting process. A semicircle metal is installed on the drive bearing of the transmitting system, and a switch detector is placed on the side. This allows us to determine whether the packaging submitting system is late or early compared to the paper submitting system by detecting the output status of the optical receiver. Based on this, we can make the motor move clockwise and anticlockwise respectively, achieving synchronous control. Keywords: Packaging Machine; Synchronous Control; Submitting Process 1 Introduction The most prominent characteristic of packaging machinery is its complex and frequent actions, along with a large number of actuators. Using relay control logic in such applications inevitably requires a large number of intermediate relays. When controlled by a PLC, these intermediate relays can be replaced by programming their internal auxiliary relays. Therefore, foreign countries have widely adopted PLCs to replace traditional relay control panels in injection molding machines and various packaging machines, significantly reducing failure rates and improving performance. Currently, most packaging machinery in China still uses relays for its control components. If a PLC can be used instead, the mechanical structure can be simplified, and both mechanical and electrical designs can be simplified. More importantly, it can enable certain functions that were previously impossible, making the packaging machinery intelligent to some extent. For the control system of a PLC-based packaging machine, synchronous control during the feeding process is a very important link. This paper designs the synchronous control of the feeding process and designs the corresponding circuit. 2 Power Supply Line 2.1 Main Motor Start Control Before starting the main motor, the main control clutch should be in the disengaged state to ensure that the main motor starts under light load. If all detection and control conditions are valid, pressing the start button will enable the main motor to start under light load and low speed, and automatically control the high-speed operation of the frequency converter after a certain time delay. If the machine malfunctions, the power should be cut off immediately and mechanical braking should be applied to ensure the safety of the machine. 2.2 Frequency Converter Operation Control The operation control of the frequency converter mainly includes operation start, automatic speed setting, fault alarm shutdown, fault indication, and fault clearance. 2.3 Control of the Paper Feeding Motor After the main motor starts, the paper feeding motor should run automatically to ensure sufficient paper rolls in the lower paper path for the pusher board. It should also have automatic high/low speed switching under the control of the JS3 sensor (which detects whether the pusher board is pushing or retracting). When the main machine stops, the paper feeding motor should not stop immediately; it must stop after a delay. Otherwise, a short-term paper shortage or blockage in the lower paper path will occur, affecting the restart of the main motor. 3 Synchronous Control During Feeding During the operation of the high-speed fully automatic sealing machine, both product feeding and packaging material feeding are continuous and are affected by many factors, such as changes in production speed and uneven tension and stretching of the packaging material. Therefore, there is a synchronous control issue between these two systems that requires constant speed adjustment. 3.1 Synchronous Control System The block diagram of the synchronous control system of the sealing machinery is shown in Figure 1. Mechanical power is provided to both the product feeding system and the differential, with the differential output being used for packaging material feeding (equipment without synchronous control directly transmits mechanical power to the packaging material feeding system). The signals for product feeding and packaging material feeding are fed back to the synchronization control circuit to compare whether they are synchronized. If they are within the synchronization range, the servo motor stops, and the differential outputs the input speed to the packaging material feeding system. Otherwise, when the packaging material feeding is slower than the product feeding, the servo motor rotates forward, and the differential adds a positive compensation to the normal output speed to increase the packaging material feeding speed until they are synchronized; when the packaging material feeding is faster than the product feeding, the servo motor reverses, slowing down the packaging material feeding so that they are at the same speed. [align=center] Figure 1 Block diagram of the synchronization control system[/align] 3.2 Signal Acquisition When the packaging material needs to be cut to a fixed length, such as the packaging of a single toilet paper roll, the packaging material is placed on the raw material rack in the form of a roll, and a color mark is printed at certain intervals. At the same time as the toilet paper roll is fed, the packaging material also needs to be cut, which increases the complexity of synchronous feeding. As shown in Figure 2: When the packaging material is fed to a certain length, the photoelectric sensor reads the color mark signal and sends this signal as a synchronization signal to the comparator. Simultaneously, this signal is sent to the paper cutting mechanism. Since the paper cutting mechanism and the packaging material are synchronized in the horizontal direction (the synchronization control between the paper cutting mechanism and the packaging material will not be discussed here), the feeding speed is not affected. [align=center] Figure 2 Synchronization Control Method[/align] The signal from the product feeding system is extracted using a proximity switch. A semi-circular metal plate 1, as shown in Figure 3, is installed on the drive shaft of the product feeding system. A probe of the proximity switch J is installed on its side. At the instant shown in the figure, the proximity switch does not sense the metal plate 1, assuming the output state is 1. When the product feeding shaft 3 rotates, the semi-circular metal plate blocks the proximity switch, and the proximity switch output state J becomes 0. Therefore, for each rotation of the product feeding shaft, the proximity switch's 1 and 0 output states each occupy approximately half the time. Assuming the photoelectric sensor S outputs 1 when it detects a color mark signal and 0 when it doesn't, we can determine whether the product feeding system is lagging or leading the packaging material feeding system by judging the output state of the proximity switch each time the photoelectric sensor detects a color mark. At the moment shown in Figure 3, when the photoelectric sensor S outputs 1, the proximity switch J also outputs 1, indicating product feeding is lagging. When J is 0 (i.e., the semi-circular metal plate blocks the proximity switch), S is 1, indicating product feeding is leading. This judgment can be used to control the servo motor to compensate for the product feeding system's speed. If the two systems are perfectly synchronized, within the synchronization range of Figure 3, the servo motor should neither rotate forward nor backward, remaining stationary. Specifically, the control circuit is triggered by a transition signal at the transition between leading and lagging, providing a delay time. During this time, obtaining the color mark signal S indicates synchronization, and the servo motor is kept stationary. The length of this delay time can be adjusted at any time, thus achieving adjustable synchronization accuracy. After this delay ends, if an S signal is obtained, it indicates that the product supply is ahead of schedule, triggering a control action. [align=center] Figure 3: Acquisition of Product Supply Signal Figure 4: Control Circuit Principle[/align] The above principle can be implemented by Figure 4. When S is 0, no color mark is detected, and both AND gates F and Z are locked. The state of J has no effect on the output result, and there is no output for either positive or negative compensation. Only when a color mark signal is detected, S=1, and pins 2 and 4 in the circuit are at high potentials, does the state of J affect the output. If J=1, pin 1 is at a high potential, F outputs 1, and reverse compensation is performed. If the packaging material supply is ahead of schedule, J just changes from 1 to 0, pin 1 is at a low potential, locking F, while pin 3 is at 1 due to the inverter. If S=1 is obtained, the potential of pin 4 is also 1, and the output state of Z depends on pin 5. However, due to the jump of J, the delay circuit receives a negative trigger pulse, outputs a low potential, making pin 5 0, locking Z and resulting in no output. At this time, neither forward nor reverse compensation operates, meaning the compensation motor stops, indicating that the two systems are in a synchronized state. After the delay ends, the delay circuit outputs a high potential, making pin 5 a potential of 1. If the packaging material supply is delayed, the color mark S=1 is detected, making pins 3, 4, and 5 all high potentials, and Z output is 1, forming forward compensation. 3.3 Implementation of Synchronous Control Circuit Principle The principle of the synchronous control circuit is shown in Figure 6. The input of the proximity switch is connected to the J terminal, and the input of the photoelectric sensor is connected to the S terminal. The comparator circuit is composed of two three-input NAND gates from a 74LS10 integrated circuit, and the inverter is a 74LS00 integrated circuit. A 555 timer circuit is used, and the delay time T1 of the circuit can be adjusted by adjusting the potentiometer R1. Figure 5 Control Circuit The shorter the T1 time, the higher the synchronization accuracy. The adjustment effect of T1 can be indicated by the light-emitting diode LED1. As long as pin 2 of the 555 receives a negative pulse, pin 3 outputs a high potential. In order to lock pin 5 of the NAND gate 74LS10, an inverter is used to invert the phase. The comparison result of the NAND gate is output to two delay circuits composed of 556 timers. The outputs of these two delay circuits control the forward and reverse rotation of the servo motor, respectively. R8 and C9 determine the reverse compensation time, and R7 and C7 determine the forward compensation time. R8 and R7 have equal values ​​and are linked, and C9 and C7 also have equal capacitance, so the forward and reverse compensation times of the servo motor are the same. BG1 and BG2 drive relays K1 and K2 respectively to achieve forward and reverse control of the servo motor. Diodes D2 and D3 provide protection, meaning that the servo motor will not malfunction if reverse or forward commands are issued during forward or reverse compensation. There is also an interlock protection circuit in the main circuit of the servo motor. In fact, solid-state relays can be used instead of ordinary contact relays in the main circuit. The forward and reverse operating status can be indicated by LED2 and LED3. The synchronization accuracy adjustment of product feeding and packaging material feeding should be comprehensively considered based on factors such as packaging quality requirements, production speed, and forward and reverse compensation. Adjust the variable precision of R1; if the synchronization accuracy requirement is high and the production speed is fast, the resistance value of R1 should be appropriately reduced. Additionally, adjust R7 and R8 to change the compensation time of the servo motor each time. If the servo motor frequently alternates between forward and reverse movements, it indicates that the compensation amount exceeds the requirement, and the compensation time can be appropriately reduced. If the servo motor frequently moves in one direction, it indicates that the compensation in that direction is insufficient, and the compensation time can be appropriately increased. Ideally, the compensation of the servo motor should not be too frequent, and both forward and reverse movements should alternate. Therefore, R1, R7, and R8 should be adjusted together. [align=center] Figure 5 Control Circuit Principle[/align] 4 Summary In the roll paper packaging machine, the roll paper and packaging paper are required to arrive at station 1 simultaneously, which raises the issue of synchronous control during the feeding process. In synchronous control, we install a semi-circular metal plate on the drive shaft of the roll paper feeding system and install a proximity switch probe on the side. By judging the output state of the proximity switch each time the photoelectric sensor detects the color mark, we can know whether the packaging paper feeding system is lagging, leading, or synchronized with the roll paper feeding system, thereby enabling the servo motor to move forward, reverse, or remain stationary, thus achieving synchronous control during the feeding process. The author's innovative points: This paper analyzes and studies the control system of a PLC-based packaging machine, and proposes a synchronous control scheme for the feeding process. Practical operation proves that the principle and circuit of this control method are reasonable and feasible, meeting actual needs. The synchronous control accuracy can be adjusted online without stopping the machine, and the control effect is significantly better than conventional cam control methods. References: [1] Wu Yaxiong. PLC control system and design of towel printing machine. 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