Introduction: Convex embossing, a special process technology in the surface finishing of printed materials. The use of uneven embossing can make printed products have a three-dimensional effect, and the overall structure also has rich levels, adding more and more intense artistry. And it is an environmentally friendly process, and its production process is free of any pollution.
“A special process technology in the surface finishing of convex prints. It is suitable for female (concave) and male (convex) molds. It uses mechanical action to apply pressure exceeding the elastic limit of printed substrates to perform artistic processing on the printed surface. .

01 Features
The embossing process is an environmentally friendly process, and its production process is free of any pollution. In today’s green era, the use of this process can focus on embodying the environmental protection of users or publishers. The use of concave-convex embossing on the printing material can make the printed product have a three-dimensional effect, and the overall structure also has rich levels, adding more and more intense artistry. It can replace traditional fonts, colors, etc. to display the core content, highlight a part of the overall design, and highlight its important status.
02 Material characteristics
Template material
According to different design requirements and printing quantities, the material selection of the embossed embossing template will be different. The template materials are different, and there are also significant differences in production costs, process effects, and number of prints.

Zinc version (or magnesium version)
With laser phototypesetting and film layout, the plate making price is relatively low, the edges are soft, the maximum number of printing can not exceed 5,000, and relief printing plates cannot be made.

copperplate
Laser engraving technology is used to make the plate. The positive plate can be made of resin or plastic materials. It has high hardness, high durability, and clear lines. The printing quantity can reach 100,000 copies. The production price is more expensive.

Brass plate (or zinc-copper alloy)
It is currently the best material for making concave-convex templates, and the price of materials and the cost of plate making are relatively high. Laser engraving can be used in mass production, which can reach more than 1 000 000 prints. Can produce high quality products.

Paper
In the production of bump embossing, in addition to choosing the right print, the right paper is also important to make a good embossing effect. The thickness of the paper and the thickness of the surface will affect the performance of details. For example, 25% cotton and 100% cotton paper exhibit significantly different printing results.

a. Generally, paper with a grammage of 180g / m2 or more is more suitable for embossing, but this is not a constant standard. If the paper is too thin, it will be easily broken during embossing.
b. A sufficiently thick and flexible paper is the basis for printing effects, especially for print designs that need to highlight the relief effect.
c. Long-fiber paper generally has good toughness, and its resistance to India is better than short-fiber paper.
d. Recycled environmentally friendly paper is not suitable for embossed embossing. Due to the factors of the paper itself, it may cause deviations in the effects of different pages, and it is easy to cause edges to crack.
e. If it is a process that requires heating (such as bronzing), it will greatly increase the probability of paper breakage. Therefore, it is more important to choose paper carefully. Before the four-color printing, the relevant tests should be done well, and the consumption paper budget should be appropriately increased.

03Common process characteristics and application The plain embossing area and the surrounding area do not have any printed patterns. The requirements for paper depend on the specific design graphics, but paper with light color, long fiber and high toughness is more suitable for the plain embossing process.

Tong Ming convex

Leave blank areas when printing, and then bump after printing. Stencil making requires strict alignment requirements. As the bumps will be slightly raised after the bump, the stencil should be slightly smaller than the graphic design graphic.

Texture
According to the texture and texture of the graphics, it can be perfectly combined with various other printing technology processes to produce printed works similar to exquisite reproduction oil paintings. Therefore, it is also called convex painting.

Engraved
The convex surface is a three-dimensional plane structure, which makes the overall figure float out, but the outline of the periphery should be changed according to the screen design to show a similar print effect.

Polyconvex
The laser engraving version has clear levels and a large difference in up and down. There are strict requirements for the production of embossed stencils. In order to highlight the details, it is best to provide fine graphics or originals to the stencil maker.

Bronzing convex

Using the embossed hot stamping plate production method, bumping and hot stamping can be completed at one time. In the terminology of hot stamping anodized aluminum, this process is called three-dimensional hot stamping. The stamping stencil is generally made of brass material, which can improve the accuracy of stamping and bumping. In addition, the printing material must meet the physical requirements of stamping and bumping at the same time. The bump height needs to consider the toughness of the paper and the impact strength that the gold foil can withstand.

04Common faults and solutions
1) The outline of the pattern is unclear
cause
① The pad is uneven and the pressure is not enough
② The gypsum layer is unevenly distributed, and the thickness of the gypsum layer is not enough
③The accuracy of the imprint machine is poor.
④ Uneven thickness of paper, or double sheets
Solution
① Increase the pressure appropriately and adjust the pad
② Repair with plaster
③ Adjust the mechanical accuracy and the position of the plaster plate
④ Repair plaster board
⑤ Eliminate double sheets and change paper

2) Inaccurate outline
cause
① The engraving position of the printing plate (yin version) is inaccurate
② The rules of printed matter are inconsistent
③ Overprinting error in printing
Solution
The negative graphic is smaller than the printed material, that is, corrected on the printing plate, and the printed graphic is larger than the printed material (the error is small), that is, corrected on the positive plate. When the above methods do not work, you must make a new plate.

3) Broken during plaster relief printing
cause
① Too little glue is added when adjusting the gypsum slurry
② The quality of gypsum powder is not good, and the fastness and viscosity are not enough
③ Suddenly increased pressure during imprinting
④ Double sheets or debris on the surface of printed matter
⑤ Imprint pressure adjustment is not suitable
Solution
① Properly increase the amount of glue
② Replace gypsum powder
③ Avoid sudden pressure increase
④ Avoid double-sheet and sticky matter input
⑤Adjust pressure

4) Surface spots
cause
① There are impurities in gypsum powder or glue
② Impurities on the surface of printed matter
③ plaster sticks and impurities
Solution
① Before mixing with gypsum slurry, carefully check and remove impurities
② Remove impurities
③Check and remove plaster shavings

5) Printing on the way
cause
① uneven pressure
② The bonding strength of the printing plate is not enough
Solution
① Check the flatness of letterpress
② Check the adhesion fastness, or re-stick the printing plate

05 matters needing attention
1) Do not bump the surface of the product in multiple places, or bump in a large area. The effect is not obvious, production is difficult, cost is high, and quality accidents are prone to occur.
2) The product has small lines or small fonts. It has no effect, and it causes problems with the convex registration.
3) The convex position of the product is close to the side, that is, the main line (fold line) of the product. It is ineffective and explosive.
4) The product is white, or the contrast color is not obvious. It has no effect.
5) The product has a large area of ​​graphics, fonts. No effect.
6) Do not hit convex products in general. Because the paper is extremely large and easy to explode.
7) When making letterpress, depending on the material of the product, make letterpress. As the general small box, the paper under 350g should be printed with general letterpress. For the mounted products, the thickened version, especially the pitted products, must be 3.0 or more, otherwise it has no effect.