RGS Automatic Registration System Used in Web Printing Presses

The RGS automatic registration system automatically maintains color registration throughout the printing process. Among them, the RGS V-Series N-type uses an optical scanning head to monitor the diamond-shaped positioning marks printed on the surface of the web. In automatic mode, when the average positioning error is greater than the maximum positioning error, the system will start the lateral or radial motor to correct the error. The appearance of the system is shown in Figure 1. Its operation control station is a touch screen, and input relevant control parameters on the touch screen, such as the location of the positioning mark of the web, the printing format, and the positioning tolerance. After the printing machine is running, the scan head searches for and tracks the positioning marks printed on the paper, and then transmits the data to the printer interface box. The printing machine interface box uses the data from the scanning head to monitor the position and quality of the printed positioning marks, and determines whether there is Mark misplaced.

1. Operation Control Station 2. Optical Scan Head 3. Interface Box

Quad/Tech registration marks are in the shape of diamonds. These marks are printed on a web, along with a color separation version of the printed image. These marks are an integral part of the exposed monochrome image. The RGS registration system reads two sizes of Quad/Tech registration marks: standard size (1.5 mm/0.05 inch) and small size (1 mm/0.04 inch).

The Quad/Tech registration system scans the printed registration marks with the optical scanning head. If the mark is not registered and the system is in [AUTO] mode, the RGS system will send a signal to the corresponding register motor to make it print. The platen roller moves circumferentially or axially, restoring the mark to the register state. If registration errors occur with more than one diamond mark, the RGS system will mobilize all the required register motors to recalibrate the plate cylinder.

When the printer exceeds the following rate, the registration system will not be able to properly track the mark:
Use the standard diamond marked RGSIV series X------2200 feet/minute;
Use small diamond-shaped RGSIV series X------1600 feet/minute;
Use standard or small diamond shaped RGSV and RGS series N—3000 feet/minute.
The registration mark format includes two reference marks and a registration mark for each color separation (one registration mark for each additional color on the roll).
When using the four-color marker format, five markers can be used for six different color registrations;
When using the six-color marker format, seven markers can be used for six different color registrations;
When using the eight-color marker format, nine markers can be used for six different color registrations.

The printing press plate must be printed on the web so that it matches one of the mark patterns on the following pages. The printed mark must match the size of the registration mark provided on the original Quad/Tech company (as shown below). Once the RGS scanhead detects and tracks the printed pattern, the RGS system can determine if the mark has deviated.

Each pair of registration marks has a pair of fiducial marks at its front end and at the back end. These two marks respectively indicate the start and the end of the registration mark pattern and are used by the RGS system to indicate the reference color. The reference color is generally the main color of the printed image, usually black. If there is no black, the color is the second highest in color (preferably red).

The RGS system requires that each web layout to be controlled must have a set of registration marks, in addition to the printing plate of the reference color. Each plate must have an exposure mark, and the plate for printing the reference color should have two exposure marks.

Pictured:
1. Plate front 2. Plate back 3. Proper mark 4. Error mark is not corrected perpendicular to the leading edge of the plate 5. The wrong reference marks are not aligned

To ensure normal operation, the plate must print the registration mark in accordance with the following requirements. The back-end fiducial marks must be directly aligned with the front-end fiducial marks, and the fiducial marks must be vertically aligned with the leading edge of the plate.
To maximize system performance, the space surrounding the printed registration mark set should meet or exceed the following requirements: 12.7 mm (0.5 inch) in front of the first mark or 12.7 mm (0.5 mm) after the last mark There should not be any printed image or mark within inches. The registration mark should be centered in a blank area or blank area that is at least 4.8 mm (0.19 inches) wide.

Leaving a large blank area around the marker group enhances the scanning head's ability to correct large register errors. Therefore, do not print any image or mark in the blank area. Otherwise, the mark or image in the blank area will be misidentified by the system as the registration mark, causing unnecessary correction errors and affecting the registration performance of the RGS system.

When the web for printing is thin and light, the scanning head may not read the registration mark on the surface of the paper by scanning the paper to the reverse mark. In this case, the scanning head will not detect the sleeve. Quasi-marking or sending wrong data to the system causes unnecessary correction errors. To prevent this from happening, it should be ensured that there is a blank area on the web of the reverse side of the registration mark. It is best to develop a set of standard work procedures that everyone must follow in the plate making room. For example, let the plate-making staff mark the upper plate surface of the web at the front of the printing plate, and mark the exposure of the lower plate of the web at the trailing edge of the plate. Therefore, do not print registration marks on the same location on both sides of the web. If the scan head reads the mark on the reverse web layout, it will provide the system with an error message.

The best registration mark orientation is in the center trim area of ​​the plate, and the orientation next to the center trim area of ​​the plate is one of the empty edges on both sides of the center trim area. It is better not to place registration marks in the trim area along the edge of the printing plate. The reason is: First, the web is more prone to “loading the edge” (the web is deformed toward the reverse paper pattern); second, the edge of the printing plate The ink balance is not as good as the ink balance in the center of the printing plate. If the registration mark is on the edge of the printing plate, the mark may be rubbed due to the accumulation of excessive ink on the plate edge. In addition, if the blanket roller or the plate wrapper wears, it will result in The mark is damaged or even missing.

If the registration marks must be placed on both sides of the plate, it is better to select the transmission side instead of the operator side. The transmission unit of the printing unit is the fulcrum when the roller lifting operation is adjusted. After the roller is lifted up, the image will be deformed. The farther away from the fulcrum, the greater the image deformation, so the degree of deformation of the mark printed on the operator side will be lower than that of the transmission. Large side printed.

In short, whether it is the operator of the layout room or the unit, only by familiarizing with the principles and requirements of the RGS system, can the efficient production and maintenance of the equipment and maintenance, in order to minimize the material waste.