Performance analysis of the hottest non-contact we

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We all know that in modern water offset printing, there are two main forms of wetting, one is contact, the other is non-contact. In production, we see many contact wetting devices, and relatively few non-contact wetting devices. In this paper, we briefly introduce several non-contact wetting devices

1. Brush roller fountain device

as a kind of non-contact fountain device, some early models of Mitsubishi used brush roller fountain device. The former bucket roller is changed into a brush roller, which is made of nylon material and soaked in the fountain solution. The brush roller is directly driven to rotate by the motor and can be adjusted steplessly. The main function of the brush is to bring out the water in the bucket. A scraper is installed near the brush, which is mainly used to pump out the water on the brush. The water is ejected and bounced to the water roller, and then transmitted to the water roller after passing through the water homogenizing roller, so as to realize non-contact water supply. The amount of water is determined by the speed of the brush and the position of the water baffle. The size adjustment is also divided into overall and fine adjustment: the overall adjustment can be carried out by changing the speed of the bucket roll drive motor; Fine adjustment is to adjust the adjusting screw of the water baffle to make the position of the water baffle suitable, so as to accurately control the size of the water supply. If the water baffle is also remotely controlled by the motor, the water supply volume can be automatically adjusted. The biggest advantage of this mechanism is that it can adjust the local water volume

1-bucket roll, 2-scraper, 3-adjusting screw, 4-water baffle, 5-water equalizing roll, 6-pressure roll, 7-water mixing roll, 8-water landing roll, 9-bucket

another structure of the brush fountain device is Harris' brush fountain device. In this structure, the brush roller is not directly immersed in the fountain solution, but always in contact with the bucket roller in the bucket. They rotate in the same direction and at the same speed, and the water sucked up in the bucket roller is bounced by the brush roller onto the water roller, and then the printing plate is watered through the water roller. In this structure, the water volume is only determined by the speed of the bucket roll, and the precise control of the water volume can be achieved through the stepless control of the motor

1-bucket roll, 2-brush, 3-string roll, 4-landing roll, 5-plate cylinder, 6-bucket

2 Water spray fountain system

Heidelberg Speedmaster some machine-based fountain systems use this device, and this air spray device has its own uniqueness. The smooth chrome plating roller is immersed in the fountain solution and driven by a separate DC speed regulating motor. The surface of the porous cylinder is covered with a fine braided jacket, which is rotated by the friction of the chrome plated roller. A row of nozzles are opened along the axial direction on one side of the compressed air chamber to spray the water on the knitting cylinder into a mist on the water transfer roller, and then wet the plate through the water string roller and the water landing roller. The control of water supply of this system is determined by the amount of water transferred from the chrome plating roller to the cylindrical cylinder. Therefore, when the gap between the scraper and the chrome plating roller is adjusted to control the frequency of the ramp generator and the peak voltage of the dynamic load to compare with the given value, the water supply of each axial section of the chrome plating roller can be completed

1-chrome plating roller, 2-water bucket, 3-scraper will cause serious consequences, 4-adjusting nut, 5-cylinder, 6-compressed air chamber, 7-water transfer roller, 8-water string roller, 9-water roller

there is another kind of water spray fountain device, which is more simple, that is, the water bucket roller with continuous rotation to bring up the water, and there is a row of air nozzles in the water bucket roller to spray the water to the plate cylinder. The water volume is controlled by the water outlet regulating plate

1-adjusting plate, 2-water tank, 3-water bucket roller, 4-Air nozzle

this water spray system is easier to evenly water the printing plate

3. Air scraper fountain device

also known as Mullen fountain device, is developed by American Mullen. The bucket roller of this device is a rubber roller, which is installed at a position 0.1mm away from the surface of the printing plate, and constantly rotates to bring water to the printing plate cylinder in the form of water film. The water supply of this device is controlled by an air scraper, mainly blowing compressed air to blow away the excess water, and then the blown water is sucked back to the water tank by the suction device. At present, the development status of the domestic plastic machinery industry is that it has low independent innovation ability and few advanced and personalized special varieties

1-bucket, 2-bucket roll, 3-sink, 4-suction device, 5-compressed air, 6-air scraper

although this device solves the problem of the backflow of the fountain solution, its suction nozzle and blowing nozzle are easy to get dirty and there is a certain noise in the work, So it is not widely used now

the most direct advantage of using a non-contact wetting device is that the emulsion on the printing plate will not flow back into the water bucket, so that the solution in the water bucket can be kept clean, and the possibility of floating dirt on the printing plate due to water can be effectively avoided. Of course, this wetting device also has its own shortcomings. For example, the mechanism is generally complex, and many performances are unstable, which is troublesome for operators to master, This may also be a major reason why the non-contact fountain mechanism is not widely used

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