Programmable controller (PLC) is a microprocessor-based special computer for logic control. It takes care of the skills and habits of on-site electrical operation and maintenance personnel. It uses computer software technology to constitute the people's customary relay model, and abandons The computer computer language commonly used in computer programming language expression form, a unique form of a relay ladder diagram-based image programming language and modular software structure, the user does not necessarily grasp the number of computer knowledge, according to the PLC instructions prompts It can be programmed directly according to relay ladder diagrams and logic algebraic expressions. Therefore, it has the intuitiveness of the relay circuit, which is easy to learn and easy to program and debug. It breaks the psychological barrier that people have a mystery to the “computerâ€. PLC technology also makes full use of the advantages of the microprocessor to meet various industrial fields. Real-time control requirements, which can be freely used by the internal logic relays composed of computer software, timers, counters and other logic functions, the input signal and internal contacts of the relays, timers, counters can be called multiple times, making programming more flexible, It does not change the hardware and wiring too much due to the change of the controlled object's program. Often, it only needs to modify the user program to meet the new process requirements. This is unmatched by the control device composed of relays and sequence controllers. In terms of service life, PLC far exceeds the relay-contactor control system. Therefore, the control system is more secure and reliable, the downtime caused by the fault is reduced, the maintenance cost is reduced, and the production efficiency is improved. Now the application of programmable controllers on automatic die-cutting machines proves that PLC technology will be widely applied in all walks of life.
Tangshan Yuyin Printing Machinery Co., Ltd., the leading product of automatic die-cutting and creasing machine, originally used a relay-contactor control system. Due to the high degree of automation of the machine and many electrical components, the original system was complicated, wiring was inconvenient, and installation was difficult. Poor maintainability, a combination of various factors, the original machine control system is not reliable, debugging is also very difficult. At the same time, due to backward control technology, the overall quality of the machine is low, and its competitiveness is not strong. It can only rely on the low price (relatively speaking) to occupy the market. Since August 1989, it has cooperated with Japan Sun Corporation to carry out its control system. The fundamental transformation, the application of PLC technology, makes the appearance of the automatic die-cutting creasing machine a new look, greatly improving the reliability and degree of automation, digestion and absorption, and soon on the series models (MY680A, MY720, MY920A, MY1020, TYM1020) Blooming everywhere, bearing fruitful results. In order to facilitate the introduction of the application of PLC in the automatic die cutting machine, the requirement of the automatic die cutting machine for the electrical control system is briefly introduced:
The machine is required to have automatic paper feeding, automatic die cutting, automatic paper delivery, automatic counting, fault stopping alarm, and various safety protection functions. The analysis is as follows:
(1) Automatic paper feeding: The operator stacks the cardboard code to be processed on the paper feeding table, and feeds the paper boards one by one through the feeder suction nozzle to the paper feeding board, one by one, and advances with the conveyor belt one by one. . As the paper is continuously fed out, the height of the paper stack gradually decreases. When the height is lowered to a certain height, a proximity switch is actuated by the automatic paper lifting mechanism, so that the motor drives the paper feed table to increase, and the paper feed continues, and the cycle continues until All paperboard is sent out so as to realize automatic paper feeding. This section also requires manual lifting and lowering of the paper table.
(2) Automatic die cutting: After the paper board on the paper feeding conveyor arrives at the die cut part, it must be positioned by the front baffle, the side pull tab is positioned on the paper board, and after the electrical inspection is correct, the paper gripper on the gripper row will hold the paper board. Take to the die-cut version, through the crankshaft quadruple lever mechanism, driving the lower platform after the pressure is completed, and then the main chain driven teeth row will be processed after the paper board to the delivery station.
(3) Automatic delivery: After the processed cardboard arrives, the grippers are opened by the open mechanism, and the cardboard falls on the delivery table. As the paper is continuously delivered, the height of the paper stack on the delivery table is continuously increased. Shooting photoelectric switch shading action, the delivery table automatically drops a distance, photoelectric switch reset, so the cycle continues to achieve automatic delivery.
(4) Automatic counting: After the cardboard is brought out of the die-cut section by the tooth row, it is detected by the reflective photoelectric switch, and then it is matched with the time-saving photoelectric switch to count when there is paper, and it does not count when there is no paper. In addition, a preset counter may also be provided. When the preset number is reached, a signal is sent and a note is inserted in the stack so that the semi-finished product can be packaged by the preset number later.
(5) Fault parking alarm and safety protection settings: This machine is equipped with paper feed super high, double sheets, paper skew, not in place, build paper, paper fall, front and rear lock version, front and rear windows, platform extraction, delivery anomalies, left and right Various protection and safety switches such as chains and oil pressure abnormalities. Any failure of any of these switches requires immediate shutdown. After each switch, there is a corresponding red diode on the panel of the panel to give an alarm indication to facilitate the operator to troubleshoot and reduce the downtime. There are also many other features that are limited in length and will not be introduced here. Many of the above functions have been implemented before PLCs were used, but they are not reliable, they have failed, and maintenance is difficult.
According to the requirements of the automatic die-cutting machine on the electrical control system, the input and output points required by the PLC are calculated separately, and the configuration hardware is then selected for the PLC control system. After calculating the selected Fuji NB series host and extension as the machine's control configuration, but also taking into account the local application of more active sensing elements, PLC own 24V capacity is limited, and configure the DC power supply (3A, 24V) . After the system configuration is completed, the PLC program is set up. Because the program is longer, only some of the program sections that highlight the characteristics of the PLC application are listed below:
1. Reset control program: This machine uses a large number of switches, that is, the rotary switch can not be automatically reset, there is no power protection, such as power failure when the switch is in the "ON" position, immediately after the power transmission actuator to move, this non-human control action, Easy to cause equipment and personal accidents. After carefully reading the PLC manual, we found that its special relay M8011 has this feature, also known as "reset flag", so there are the following procedures, the effect is better after application.
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Program Diagram 1