Second, the letterpress production method
After the gravure is made, it is also necessary to formulate a cooperating relief plate. The graphic on the letterpress is the opposite of the embossed intaglio. The method of making the relief printing differs depending on the raw materials used. At present, gypsum-made relief printing and polymer-based relief printing are often used.
1. Plaster made of letterpress. Its main production material is gypsum powder. Gypsum powder is gypsum plaster, and its powder has plasticity after being mixed with water and hardens, but its texture after drying is very brittle and its compressive strength is not high.
Other auxiliary materials include: 1 Gum arabic: used as a binder for gypsum powder, it can increase the durability of gypsum after drying; 2 paste: as a gypsum powder for the slow release agent, can prevent drying too fast, so that Plate processing; 3 cardboard. The base liner for the positive punch, paper requirements soft; 4 thin paper: apply to the male punch surface to avoid undue gypsum stick to the bright gravure; 5 fine sandpaper: for positive convex Mold trimming.
The manufacturing method of the gypsum punch is: the prepared gravure is glued on the metal floor of the hand press. After the flat board, the yellow cardboard is stuck on the embossed plate, and then the gypsum powder is reconstituted into a paste with a gum solution. , and quickly apply the gypsum plaster on the yellow cardboard imprinted on the surface of the printing plate; after the flattening, cover with a thin layer of paper (such as postal paper, cane paper, etc.), and then cover with a layer of plastic film. Anti-gypsum pulp is embedded in the concave floor pattern. In this way, after pressing, the surface of the gypsum layer forms a convex graphic.
When the first impression, the pressure should not be too large, as long as the developer can be slightly, the main purpose is to obtain a clear graphic mark on the surface of the gypsum layer, as a reference for checking the layout and adjusting the pressure. Followed by a second imprint. First, add a thick white paperboard behind the intaglio plate. When the gypsum layer is nearly dry, press it again. At this time, the graphic indentation on the surface of the gypsum layer will be very obvious.
After the second embossing, a portion of the gypsum slurry was squeezed and then overflowed, and the gypsum slurry with the depressed plate was convexly formed. In order to reduce the pressure on the machine and enhance the effect of the graphic and text, the part of the gypsum layer that does not need to be raised and does not need to be imprinted should be scraped off and removed.
When scraping, it should be dealt with separately according to the structural features of the graphic outline. Through scraping and controlled art processing, the printing plate can meet the requirements of the imprinting process.
2. Polymer material made of letterpress. Such reliefs are generally based on thermoplastics and are formed by single-die molding.
The single-die die-press molding is a method in which after the pre-assembled sheet and the female die are overlapped, the pre-formed sheet is formed by heating and pressing in a special-purpose molding machine.
The process is as follows:
The surface of the blank is washed, the surface of the die is coated with a release agent, the frame is mounted on the machine, the temperature is adjusted, the pressure is pressed into a mold, the cooling is released, the trim is trimmed, and the finished product is a relief.
Among them, the blank can be cleaned using a detergent or a weak acid, a weak alkaline solution. Mold release agents generally use silicone grease or silicone oil.
Molding temperature, pressure and time are the main factors affecting the quality of the punch. For example, the molding temperature and pressure directly affect the draw ratio of the substrate and the punch size error.
It is very important to choose the base material from the convex plate made of polymer materials. The choice of process conditions in the punch molding depends mainly on the type of substrate. The same die, the same process conditions, if the use of different substrates, the quality of the punch after molding may have greater differences. It is generally required that the substrate has good mechanical strength, the molding is quick and convenient, and the molding process conditions are demanding.
After molding, the relief plate can obtain sufficient plate-printing rate with general double-sided tape or universal adhesive.
The main advantages of high-molecular materials are: short plate-making cycle, high speed, low technical difficulty, and easy operation; prefabrication can be used to facilitate the commercialization and popularization of plate-making of concave-convex plates; the relief substrate has high compressive strength and flexibility. The recovery value is large. Under certain conditions, the prints can always maintain the quality effect within a certain amount of impressions. With the further popularization of the embossing and embossing process and the continuous development and application of new polymer materials, the methods for making the relief will be widely used.
III. Technology and Art Processing in Concave-Pattern Edition
The embossing and embossing product can thus obtain the effect of three-dimensionality on the surface of the plane print, and the design and production quality of the printing plate (mainly gravure) is the key.
In addition, the design and production of the entire concave-convex part must take into account the characteristics of each part, and also consider the entire layout style and the overall artistic style, so as to achieve a harmonious unity between the local and the overall.
