Programmable controller (PLC) is a special-purpose computer for logic control with a microprocessor as the core. It takes care of the skills and habits of on-site electrical operation and maintenance personnel. It uses computer software technology to form the relay model that people are used to, and discards it. The expression form of the computer programming language commonly used in microcomputers is uniquely formed into a set of image programming language and modular software structure based on relay ladder diagram. The user does not necessarily have much computer knowledge. According to the instructions of the PLC manual, Can be programmed directly according to relay ladder diagram and logic algebra. Therefore, it has the intuitiveness of the relay circuit, it is easy to learn, and programming and debugging are very easy. It breaks the psychological barrier of people who have a mysterious sense about the "computer", and the PLC technology makes full use of the advantages of the microprocessor to meet various industrial fields. Real-time control requirements, it can freely use internal relays, timers, counters and other logical functions composed of computer software, the input signal and the internal relays, timers, counter contacts can be called multiple times, making programming more flexible, It does not change the hardware and wiring too much due to the changed program of the controlled object, and often only needs to modify the user program to meet the new process requirements, which is unmatched by the control device composed of the relay and the sequence controller. In terms of service life, PLC also far exceeds the relay-contactor control system. Therefore, the control system is safer and more reliable, the downtime caused by the fault is reduced, the maintenance cost is reduced, and the production efficiency is improved. The application of programmable controllers on automatic die cutting machines now proves that PLC technology is bound to be widely used in all walks of life.
Tangshan Yuyin Printing Machinery Co., Ltd.'s leading product, the automatic die-cutting and creasing machine, originally used a relay-contactor control system. Due to the high degree of automation of this machine and the many electrical components, the original system was complicated, the wiring was inconvenient, and the installation was difficult. Maintainability is poor, various factors are combined, the original control system is not reliable, and debugging is also very difficult. At the same time, due to the backward control technology, the whole machine is of low grade and the competitiveness is not strong. It can only rely on low prices (relatively speaking) to occupy the market. Since August 1989, after cooperating with Japan Sun Company, its control system has been The fundamental transformation, the application of PLC technology, makes the automatic die-cutting and creasing machine look completely new, greatly improving the reliability and degree of automation. Flowering everywhere, bearing fruitful fruits. In order to facilitate the introduction of the application of PLC in automatic die-cutting machine, first briefly introduce the requirements of the automatic die-cutting machine on the electrical control system:
The machine is required to have functions of automatic paper feeding, automatic die cutting, automatic paper collection, automatic counting, fault parking alarm, and various safety protections. The analysis is as follows:
(1) Automatic paper feeding: the operator stacks the cardboard codes to be processed on the paper feeding table, and feeds the cardboards one by one through the feeder nozzle to the conveying cardboard, and presses one by one to advance with the conveyor belt. . As the paper is continuously fed out, the height of the paper stack is gradually reduced. When it reaches a certain height, a proximity switch is activated by the automatic paper lifting mechanism, which causes the motor to drive the paper table to rise and continue to feed the paper. The cardboard is all sent out, so as to realize automatic paper feeding. This part also requires manual rise and fall of the paper table.
(2) Automatic die-cutting: After the cardboard on the paper conveyor belt reaches the die-cutting part, it must be positioned by the front stop gauge and the side pull gauge, and after the electrical detection is correct, the cardboard is held by the grippers on the gripper row Brought to the die-cutting plate, through the four-bar mechanism of the crankshaft, the lower platform is driven and the processing is completed, and then the main chain drives the tooth row to take the processed cardboard to the position of the paper receiving table.
(3) Automatic paper collection: After the processed cardboard arrives, the gripper is opened by the tooth opening mechanism, and the cardboard falls on the paper collection table. With the continuous paper collection, the height of the paper stack on the paper collection table continues to increase, making the Shooting photoelectric switch shading action, the paper receiving table automatically descends a certain distance, the photoelectric switch is reset, so the cycle is continuous, and automatic paper collection is realized.
(4) Automatic counting: the cardboard is taken out of the die-cut part by the tooth row and then detected by the reflective photoelectric switch, and then cooperated with the timing photoelectric switch to realize counting when there is paper and not counting when there is no paper. In addition, a preset counter can also be provided. When the preset number is reached, a signal is sent to insert a paper strip in the paper pile so that the semi-finished product can be packaged according to the preset number later.
(5) Failure parking alarm and safety protection settings: the machine is equipped with super high paper feed, double sheets, skewed paper, not in place, paper accumulation, paper fall, front and rear lock plate, front and rear windows, platform extraction, abnormal paper collection, left and right Chain, abnormal oil pressure and other protection safety switches. Failure of any of these switches requires immediate shutdown. After each switch is activated, there is a corresponding red diode on the analog board of the panel to issue an alarm indication, which is convenient for the operator to eliminate the fault and shorten the downtime of the fault. There are many other functions, due to space limitations, which will not be introduced here. Most of the above functions have been realized before the PLC is not used, but it is unreliable, and it is difficult to maintain due to failure.
According to the requirements of the automatic die-cutting machine for the electrical control system, the input points and output points required by the PLC are calculated separately, and the hardware is selected for the PLC control system accordingly. After calculation, the Fuji NB series host is selected and expanded as the control configuration of the machine. Considering that there are many active sensing elements used in this machine, the PLC itself has a limited 24V capacity, and a DC stabilized power supply (3A, 24V) is also configured. . After the system configuration is completed, the PLC program is started. Due to the long program of this machine, only some of the program sections that highlight the characteristics of PLC applications are listed below:
1. Reset control program: The machine uses a large number of transfer switches, that is, knob switches that cannot be automatically reset, and there is no power failure protection. For example, the switch is in the "ON" position during a power failure, and the actuator acts immediately after power is supplied. It is easy to cause equipment and personal accidents. After carefully reading the PLC manual, it is found that its special relay M8011 has this feature, also known as "reset flag", so there are the following procedures, and the effect is better after application.
Schematic diagram 1
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