Electronic cam application in printing press
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The improvement of the level of electrical control is a major direction in the development of traditional printing presses and in improving work performance.
First, the electronic cam
It is well known that cams are essential for printing presses. The design and processing of the cam is indeed very difficult. The printing speed of domestic printing presses is always below 8000 sheets/hour. A large part of the reason is that the dynamic performance of machine-related parts caused by cam mechanism is deteriorated at high speed, so mechanical cams have always been troubled by printing machines. A difficult problem in manufacturing. The emergence of electronic cams has brought hope to everyone.
The electronic cam is a function of simulating a mechanical cam by controlling a servo motor by a controller.
The structure of the electronic cam is destined to have many advantages over mechanical cams. The use of electronic cams improves the control accuracy of the machine, increases the control distance, reduces the failure rate, and improves the reliability. It simplifies the mechanism and makes the mechanism more flexible, making commissioning and maintenance easier. The electronic cam uses software to control the signal, and changing the program can change the output law of the control signal, and then change the process. If the controller of the electronic cam is modified to some extent and the sensor with higher precision is used, the number of switches can be increased, and the on-off time of the output point can be arbitrarily set, so that it can be versatile in many occasions. Electronic cam. All electronic cams have the following common characteristics:
1. Compact design and minimal wiring. The electronic cam consists of a controller, a position sensor (rotary encoder) and a connecting cable. In use, the controller is installed in the electrical cabinet and the position sensor is mounted on the rotating shaft. The sensor and controller are connected by a cable, which is convenient and quick to use.
2. Simple angle setting. The setting value of the ON/OFF position can be determined either by directly inputting the angle value or by the manual function; and the angle adjustment in the mechanical cam is difficult.
3. Durable sensor. The sensor can withstand harsh environments such as vibration, shock, harsh temperatures, oil, and dust.
In view of the many advantages of the above electronic cams, many industries and machines have adopted the advanced technology of electronic cams. Electronic cams are used in the improvement of spinning frames in the textile industry. After adopting the electronic cam technology, the traditional spinning molding process has been changed. According to the requirements of the user's spinning varieties, the spinning molding can be arbitrarily changed by parameter setting to meet the needs of new product development. The mechanical structure is simplified, the production efficiency of the machine is improved, and the consumption is reduced.
In the printing and packaging industry, electronic cams have also gradually been applied. Shanghai Yahua Company's MW1050A high-speed automatic die-cutting machine monitors and displays the whole machine operation and faults by PLC programmable controller and electronic cam indexer, which makes machine control and fault diagnosis extremely convenient. Moreover, thanks to the servo drive, its high speed, high precision and high response characteristics greatly increase the production speed. Conventional equipment typically has a maximum production speed of 80 sheets per minute, and this system doubles the production speed of the equipment to 160 sheets per minute. The closed-loop design and fast response capability of the system allows the unit to maintain extremely high control accuracy at high speeds, with overprint deviations ≤ ± (0.3 to 0.5) mm (depending on mechanical conditions).
Many foreign companies now use electronic cams as their main controller product, such as the FC21 programmable electronic cam switch manufactured by Japan Koyo Co., Ltd. for corner detection control. This provides technical support for the use of electronic cams in the printing industry machinery and equipment. For a printing machine with a large amount of mechanical cam mechanism, the use of electronic cams to modify the traditional mechanical cam structure will undoubtedly greatly improve the performance of the printing press.
Second, the offset machine constant force mechanism cam improvement
We know that the large tension spring of the offset paper feeding mechanism is used to overcome and balance the inertia of the paper swaying process. It keeps the roller of the linkage mechanism close to the paper feeding cam to keep the force closed and strict. The sporty relationship prevents shocks. Since the transfer paper shaft itself rotates around the center of the eccentricity, the transfer paper is controlled by the cam and the link mechanism for swinging motion, and is fixed on the hanging spring movable pin shaft at both ends of the transfer shaft, and its position constantly changes during the movement. As a result, the tensile length of the large tension spring is constantly changing in addition to the original pre-stretching during the working process. When the transfer paper is swung to two extreme positions, the maximum tensile change amount is 110 mm, which causes uneven load, which is detrimental to the dynamic performance of the transfer mechanism. At the same time, due to the frequent deformation of the spring, it breaks prematurely beyond the fatigue strength. The J2101 machine that has been eliminated will cause frequent failure of the large tension spring when it is used, which brings a lot of inconvenience to the user. Therefore, in the future improvement (such as J2108 machine), a set of tracking cam and pendulum mechanism are specially designed, so that the large tension spring keeps the stretch length constant during the whole movement of the transfer paper, which is the constant force mechanism. Through the principle and function of the constant force mechanism, we can understand that the tracking cam is the core of the constant force mechanism, but due to the limitations of its mechanical structure, there are many problems. Take the J2203 and J2108 offset press constant force mechanism, the constant force cam is not balanced, and the drum has an impact in each working cycle, so the key groove of the constant force cam hub is particularly easy to shake. Under normal circumstances, the keyway of the cam hub will sway within two years. In addition, we know that the pros and cons of cam profile design and the accuracy of machining assembly are directly related to the size of noise and vibration. At the same time, due to the limitation of processing capacity, it is difficult to obtain a perfect contour curve, so that the force of the large tension spring is difficult to ensure a constant, and only the change is small, and it is difficult to achieve the desired effect. If an electronic cam is used instead of the conventional mechanical cam, these problems are solved correspondingly, and the structure is simple, reducing the machining cost.
The original mechanical cam and many related parts were gone, and a servo motor appeared instead. The mechanical structure is greatly simplified, and the reliability of the corresponding mechanism can be improved. In summary, we can foresee that the application of electronic cams in printing presses will be more and more extensive. This will undoubtedly bring about an opportunity for China's printing machine manufacturing industry to improve product quality and catch up with foreign products in the same industry.