Chapter 3 Rotary Printing
The printing principle of web offset presses and the basic offset presses are basically the same. However, due to the very high printing speed of the rotary press, printing on the front and back, and the automatic folding device, the volume of an 8-color commercial rotary press is very large. Of course, its printing efficiency is also very high. Roughly, the output of a rotary machine is equivalent to seven or eight flat-sheet four-color offset presses.
The following are the characteristics of the webcam:
l. Commercial web presses use roll paper, which is suitable for thin paper with a paper thickness of 1059 or less.
2. The printing speed of the rotary machine is very high, with an average speed of 50,000 sheets per hour, while the general flat-sheet offset press has a printing speed of 10,000 or less. In addition, the web printing machine prints both sides of the web at the same time, and the flat-sheet machine prints one side, and after the ink is substantially dried, the printing is reversed.
3, the wonderful thing about the rotary machine is that after printing, the printed sheets are rapidly dried and disconnected, and then the different binding methods are directly folded out.
4. Rotary machines are suitable for prints with large numbers of prints and short delivery times, such as magazines, supermarket discount books, etc.
Rotary printers vary in structure depending on the substrate, and their prices are quite different. There are specialized printed newspapers, special printed stickers, printed documents, etc., and our company's rotary machines belong to high-end commercial rotary machines (model is Heidelberg M600-C24), and are printing four colors at the same time. Specially printed high-end journals can also print color inserts of color textbooks and newspapers.
Printing knowledge:
* How to overcome the printing pressure and cause the mechanical dot enlargement In the printing process, the ink transfer and the print transfer require proper printing pressure. The deformation of the dot and deformation of the dot will be caused by the deformation of the roller and the deformation of the blanket. Therefore, in the process of drying the PS plate, it is necessary to combine different models (different printing presses have different dot gain values) to select an appropriate exposure time so that the dots on the PS plate are slightly smaller than the sample drafts, and the printed matter can be kept consistent with the proofs. .
When you stand in front of a large-scale commercial rotary machine that is moving at full speed, the huge roar and the glistening gushing of colorful prints are really an audio and visual feast for someone who is engaged in or loves printing. That is how a symphony of lakes is! $Page break $
Chapter 4 Paper Knowledge
The number of sheets of paper is calculated in terms of orders, regardless of the size of the paper, for every 500 sheets.
The number of webs is usually calculated in tons, that is, using the weight to reflect the quantity. The weight of a sheet of paper is expressed in grams per square meter, and the unit is gsm, which is g/m2. If the paper of 809 is 80 g of paper per square meter.
The size of the flat sheet is usually 889mm x ll94mm, 880nlnl x 1230mm, 787mm x 1092mm, etc. The size of these sheets directly defines the size range of the book. Before you write a book, make sure that its finished product size (size) is one of the first things you have to consider.
The thickness of the paper refers to the thickness of the paper.
For medium thickness thickness, the following estimation methods can be used:
Sub-paper thickness (mm) = weight/1000
Double powder thickness = weight/1000-0 .02
Book paper thickness (mm) = weight/1000+0.02
The following summarizes the current paper types commonly used in books and magazines for your reference.
In addition, there are specially-printed newsprint, super-matt papers, printed membership forms, exercise book writing papers, and map paper, Braille printing paper, stamp paper, and carbon writing papers. In addition, in the past few years there are endless dazzling special paper and a variety of special fabrics.
There are many properties of printing paper:
l. From the paper structure, paper lines are produced during the manufacturing process. The vertical paper pattern is a straight grain, and the horizontal grain is not smooth. When the books are printed, the paper lines are parallel to the spine, so it should be considered when opening the paper.
2. The paper's thickness, smoothness, stretch rate, etc. belong to the physical properties of the paper. The smoother the paper, the more fine-tuned the dots can be printed. If the paper expansion rate is large, overprinting will be inaccurate when printing, resulting in errors;
3, the paper's mechanical performance indicators are the degree of tear, folding degree, stiffness, such as the same thickness of paper, sometimes feel different thickness, in fact, because of good stiffness paper gives a thicker feeling;
4. The paper's whiteness, opacity, and glossiness belong to the optical properties of paper. The whiteness of the paper affects the printed color image, such as the same picture, printed on a slightly yellowish paper, and the effect is bright. On a white paper that is slightly blue, the effect is dark. In addition, paper with poor opacity is one of the causes of print-through.
Reprinted from: Hualian Printing "China Printing Light" Open Monthly Brochure
