On the principle of gravure printing

2022-08-02
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On the principle of gravure printing

gravure printing is abbreviated as "gravure printing". A printing method in which the inking part of a printing plate is concave. In Europe, which first appeared in the 15th century, sunken graphics and texts were carved on metal plates by hand. During printing, ink was applied to remove the ink from the layout, and only the ink left in the sunken part was transferred to the paper. Later, photographic corrosion intaglio (formerly known as photocopying version) and mechanical carving were developed. Vegetable stalls in the community and roadside vendors were also hand intaglio in plastic bags (including those carved with electronic carving machines), laser engraving intaglio Electron beam engraving intaglio, etc. The gravure shape also developed from flat plate type to arc type. Most modern gravure printing is rotary printing. The plate is mainly made of metal (supplemented by chromium plating, nickel plating, etc.), and now the plastic sleeve method is developed. It is mainly used for color images, advertising, packaging and decoration printing, as well as professional banknote printing. The finished product has fine and thick characteristics

working principle:

gravure printing machine is mainly composed of uncoiler, guide group, printing group, slitting group and control group. The uncoiler is mainly used to unfold the web at a certain speed and tension, maintain the corresponding stable state, and complete the automatic or manual splicing of the web at the same time. The main function of the guide group is to ensure that the paper web does not shift laterally during the printing process and that the tension of the paper is stable. The printing group is the main component of the gravure press, which completes the main printing process, including ink supply, printing, drying, etc. The slitting group will cut the whole printed semi-finished product into small pieces so that they can understand it immediately. The control group mainly sets the operating parameters and working conditions of the gravure press, including speed, tension, temperature, and the working conditions of the pressure roller, doctor blade and ink pump

principle and operation of uncoiler

the uncoiler is mainly composed of clutch, tension roller and tension controller. The three constitute a closed-loop automatic control system, which is used to automatically adjust the speed and tension of web paper unfolding

1. Working principle

the uncoiler is a driven device without power. It mainly adjusts the supply of paper according to the needs of the printing unit (the rotation speed of the paper pulling the web). In the control formula for the rotation speed of the Web: ε T is elongation at break or elongation at yield; The process is realized through the clutch and the paper reel. In the past, most of them used electromagnetic clutch. At present, Dachuan adopts pneumatic clutch

in the printing process, the printing speed is not a constant value, sometimes gradually increasing, sometimes gradually decreasing, so it is necessary to use the tension roller to control the paper supply and tension

the tension roller swings up and down around the fixed point, and the thrust of the cylinder is balanced with the tension of the paper to ensure that the tension roller is in a balanced state. The position of the tension roller indicates the paper tension and the size of the paper supply. Input the information of this position into the tension and the paper supply speed. In the printing process, the smaller the floating distance of the tension roller, the more conducive to the stability of the paper tension

tension controller is a key component in the tension control system of Uncoiler. It mainly completes the processing and analysis of detection signals, and sends out execution commands. At present, mcs-202e controller is mainly used in China, which can indicate the working state of the brake pad used with the clutch paper reel, and set or correct the rubbing position of the tension roller at any time

2. Operation of uncoiler

according to the requirements of Frontier printing, gravure printing machines generally use ordered web paper. Due to different machine models, the outer diameter and fuel efficiency of the uncoiler paper mandrel can be increased by 6% to 8%; When the curb weight of an automobile is reduced by 100 kg, the difference is large, usually 3, 6 or 12 inches. Therefore, when ordering web paper, first consider the outer diameter of the paper roll mandrel. Generally, the inner diameter of the web paper mandrel is 2 ~ 5mm larger than that of the paper mandrel; Secondly, pay attention to the maximum outer diameter of the web paper that can be used by the uncoiler. During installation, check whether the paper core is deformed. If the deformation is too large, repair it first. After the paper is unfolded and aligned, insert the paper core into the web paper core, then check the distance between the two ends of the paper core shaft, and try to install the web paper in the middle

after the web is put on the machine, make sure that the transverse direction is at the same position as the paper being rolled. If the uncoiler receives paper automatically, butt or lap it according to the requirements of the uncoiler. When splicing, first draw lines at the splicing position, and then paste it with double-sided and single-sided adhesive tape. During splicing, ensure that the outer diameter and linear speed of the two rolls of paper are consistent

if the uncoiler receives the paper manually, cut off the winding web after stopping the machine, adjust the horizontal position of the paper, and stick it directly on the beginning of the new web

adjustment of the horizontal position of the paper during printing

the so-called horizontal adjustment is to adjust the position of the paper along the axial direction of the printing plate. This is very different from the horizontal registration of the pattern during printing. It is generally divided into three parts: uncoiler adjustment, pre printing and pre slitting adjustment

1. uncoiler adjustment

the installation of the web on the uncoiler is generally in the middle, but sometimes when the printing plate pattern is biased to one side, the horizontal position of the web must be adjusted. This adjustment is generally a one-time manual adjustment

2. adjustment before printing

this is the main work in horizontal adjustment, which is automatically completed by the guidance group. The cylinder pushes the drive roller to swing around the fixed point to adjust the relative position of the drive roller. The dotted line indicates the width of the paper and the arrow indicates the moving direction of the paper. In the process of use, first set the horizontal position of the photoelectric detection switches on both sides according to the requirements of the plate pattern position on the paper horizontal position. In this way, a closed-loop control system is formed, and the guide controller plate controls the horizontal position of the paper. The control accuracy of the system is very high, which can reach +/- 0.15 mm. In addition, it can also carry out unilateral or bilateral control

3. adjustment before slitting

in order to ensure that the slitter cuts to the horizontal tangent position, the horizontal position of the paper needs to be adjusted. The position generally adopts the same closed-loop control system as before printing, and the position of the photoelectric detector also needs to be preset

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