The 0-lead paper conveying device is an important part of the sheet-fed printing press. Its main function is to smoothly convey the paper separated from the feeder feeder to the paper positioning unit of the printing press. After the front gauge vertically positions the paper and the side gauge pulls the paper to laterally position the paper, the paper is transferred by the feed tooth to the printing unit to complete the printing. Famous foreign press manufacturers such as Roland, Heidelberg and Mitsubishi have adopted vacuum paper feeding technology on sheet-fed presses. Zhao Xiaoping proposed a structural scheme of high-speed vacuum feeding for the shortcomings of the structure of the vacuum feeding device for offset presses in foreign countries, which was theoretically discussed. At present, when vacuum feeding is adopted, the adjustment of drawing force and air volume at the side of the specified position is mainly determined by experience and adjustment, and lacks theoretical basis. In the production process, when the gas flow rate changes frequently, the problem of incompatibility of the side-sheet pull-out force is not met, so that the positioning of the paper is inaccurate and the quality of the printed matter is affected. The author developed a set of vacuum conveying paperboard, which is equipped with a paperboard with holes in the air chamber of the paper feeding device. There are many small holes on the paper conveying belt carrying the paper. When the paper feed hole and the paper feed hole cross (in this case, the area between the two holes is called the breathable area), the air flow will absorb the paper, causing friction between the paper and the paper feed belt, and drive the paper vertically. Forward; At the same time, the frictional force balances laterally with the lateral gauge to achieve a smooth pull-paper positioning. The two adjacent rows of holes in the paper transport belt on the distribution paper feed belt and feed belt are staggered. R is the paperboard hole radius, the area At=Yang 2; r is the radius of the paper feeding hole, the area Ab = takes 2. There are altogether nc effective holes for each line on the paper feeding belt (refers to the paperboard has a breathable area Holes in the paper feeding belt that do not contribute to paper feeding do not count nBR perforations in each paper feeding belt.There are nT holes in each paper feeding hole in the paper feeding board.In order to prevent paper feed skew, the number of paper feeding belts is generally For an even number, four or two, here four conveyor belts are used, and accordingly there are four rows of paper feed holes, with the center T of the first hole in the paper feed plate as the origin and a coordinate system as shown. The intersection of the tape hole and the paperboard hole, and the shaded area is the breathable area. Let the conveyor belt speed be v, the center of the hole in the i-th row and j-th column on the feeder belt is B, the coordinates of this point are (x,y), and the center coordinate of the k-th hole on the Ijx paperboard is (xt, yr), the distance between the feeding belt hole and the center of the paper feeding board is based on the relative position of the paper feeding belt hole and the paper feeding board hole to determine whether there is a gas permeability area in the two. When the paper feed belt moves to the outer paper cut hole, it is in a critical state. At this time, the distance between the paper-feeding hole B and the paper-feeding hole center T that is about to enter the partial air-permeability phase is the farthest, expressed as TBlim. The x coordinate of the paper-feeding hole B also takes the critical value as follows: Obviously, IyI must be guaranteed. TBm. When IyI = TBm, the two holes pass through but are not air permeable, and when IyI>TBim, the two holes cannot be tangent and are in the separation position when |x|>xlim and IyI are fed. The hole is in a critical state when it is moved into the hole in the cardboard and the analysis method is the same as (1). When the center B of the paper feed belt is located outside the paperboard hole, the straight line AD intersects with the straight line TB at the point C. According to the geometric relation, it can be obtained that the air permeability area of ​​any paper feed belt hole is all the paper feed hole pairs. The air permeability area of ​​the paperboard hole is formula (2), which is the mathematical model of the air permeability area of ​​the vacuum paper feeding device. It reflects the shape, position parameters, and air cavity of the paper feed hole and the paperboard hole radius, the number and distribution of various holes. The functional relationship between the breathable area. By optimizing each variable, various structural parameters that minimize the change in the air-permeability area of ​​the air chamber when the conveyor belt position changes are obtained. Using the established model, through programming and calculation, it is determined that the device is mainly composed of a mechanical system, an airway system, an electrical system, and a rack. Transmission conditions, analysis of changes in the speed of the machine, the gas flow rate and the change in air permeability after the change in the air permeability area, so as to establish the relationship between pull paper force and gas flow. 1 The test method line is basically consistent with the measured curve. When the flow rate is low (Q 0.4m3/h, the theoretical curve is basically the same as the measured curve and enters the stable feeding stage. The pulling force decreases as the printing speed increases, indicating that when the speed increases, the gas (2) 128g /m2 paper change breathable area before and after pulling paper force compared with the test data The paperboard hole area is closed 30%, equivalent to a 30% reduction in the breathable area. Use 128g/m2 coated paper to test the paper pull force before and after the change in air permeability area As can be seen, when the flow rate is low (Q 0.4m3/h, stable paper feeding can be achieved. With the constant flow rate, the lateral pull force decreases with the decrease of the air permeability area. As a result, in order to stabilize the transport of paper, a sufficiently large air-permeable area must be ensured. Comparison of the Workspace Quality of Four 1R2T Rope Towing Parallel Mechanisms ZHENG Yaqing1, LIU Xiongwei夂2 1. Huaqiao University, Quanzhou, 362021 2. University of Hertfordshire, Hertfordshire, UK 1R2T agency, compares the moving platform The size and shape of the workspace in the same two poses. The results show that when the connection point of the rope and pulley (or moving platform) coincides, the rotating working space is usually increased; based on the size of the rotating working space, the best configuration of the 1R2T fully constrained positioning mechanism is found; 2n The redundant constraint positioning mechanism provides a large translation work space for large corners. 0-lead 100-rope traction parallel mechanism is a new type of parallel mechanism. It has a simple structure, large working space, high load capacity, easy assembly and disassembly, reorganization, high degree of modularity, low cost and fast movement. The Natural Science Foundation of China (50475099) has the most practical application value for organizations whose type of freedom is 1R2T (1 rotational degree of freedom and 2 translational degrees of freedom) and 3R3T. In the past three years, the author has done in-depth theoretical research on the structural type, work space, rope tension optimization distribution, stiffness, kinematics, and trajectory planning of the rope traction parallel mechanism. In this paper, the definition of the degree of freedom of the end effector is given from a new perspective, and the mathematical model of the vacuum feeding technology is established based on the problems in the vacuum feeding technology with the scale factor, quality factor and global quality. The vacuum feeding experimental device provides a theoretical basis and experimental platform for the research of vacuum feeding technology and product development. A force model of the paper on the paperboard was established, and a calculation method of paper pulling force of the side gauge was provided. Through experimental verification, the theory is basically consistent with the measured laws, which provides a basis for the adjustment of the flow in the project. The experimental results show that regardless of the type of paper, the paper pull force always increases with the increase of the gas flow rate; the paper pull force decreases with the decrease of the air permeability area. In order to stabilize the paper feed, it is necessary to ensure sufficient air permeability.
"Gravity Die Casting. A permanent mould casting process, where the molten metal is poured from a vessle of ladle into the mould, and cavity fills with no force other than gravity, in a similar manner to the production of sand castings, although filling cn be controlled by tilting the die."
Sometimes referred to as Permanent Mould, GDC is a repeatable casting process used for non-ferrous alloy parts, typically aluminium, Zinc and Copper Base alloys.
The process differs from HPDC in that Gravity- rather than high pressure- is used to fill the mould with the liquid alloy.
GDC is suited to medium to high volumes products and typically parts are of a heavier sections than HPDC, but thinner sections than sand casting.
There are three key stages in the process.
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Study on Vacuum Feeding Technology of Printing Machine
Study on Vacuum Feeding Technology of Printing Machine
Core Tips: The Zero Lead Paper Feeder is an important part of the sheet-fed press. Its main function is to smoothly transport the paper from the feeder feeder to the paper positioning unit of the press. After the front gauge has positioned the paper longitudinally and the side guide pulls the paper to laterally position the paper, the paper is conveyed by the feed tooth.