What's the difference between offset printing and flexography?

Flexo printing is a kind of relief printing, and the material of printing plate is flexible resin plate.

The three key areas of flexographic printing are trademark labels, plastic flexible packaging and folding cartons (such as milk cartons).

A complete flexographic printing unit is usually a reel machine.

Offset printing belongs to lithography, and PS plate is used as printing plate.

Books, paper packaging and so on are generally offset printing. There are two types: lithographic and scroll.

There are two other popular printing methods-gravure printing or screen printing.

The main object of gravure printing is also plastic soft packaging, but the ink thickness of gravure printing is better than that of flexography. For example, instant noodle packaging bags and cigarette cases are basically gravure printing;

Compared with flexographic printing, gravure roller plate-making has long cycle, high cost and great pollution, and is suitable for long-term printing. Flexographic printing is low in cost and simple in production, which belongs to green plate making, but the printing quantity of flexographic printing should not be too large.

Screen printing is generally used to print special materials. Such as cloth, metal, leather, etc., are also often used in the production of post-press special effects.

Of course, in practical applications, there are usually a combination of multiple printing methods.

Any printing principle is inseparable from color separation and dot. Many things can be realized by different printing methods, but the specific process arrangement depends on the quantity of products, economic costs, customer requirements and the length of production cycle.

Flexographic printing is a direct printing method, because it uses an elastic convex image printing plate, so it is called flexographic printing. The flexographic printing plate is glued to the printing plate cylinder, and the printing plate is supplied with ink through the engraved metal anilox roller. Because flexography is very elastic, it can transfer liquid or fat ink to almost all kinds of materials. Flexography is light pressure printing.

According to the characteristics of flexographic printing, the manuscript suitable for flexographic printing should be selected when selecting manuscripts:

1. To design various patterns suitable for flexible printing, such as lines and color blocks, spot colors are preferred.

2. Too small words and lines (especially the requirements of highlighting) are difficult to achieve and should be avoided in design.

3. The design should avoid strict registration requirements.

4. Also consider the characteristics of the printing machine and whether the ink can truly restore the manuscript. Half-tone manuscripts should avoid designing and selecting large-area high-gloss manuscripts and pictures.

5. The size of the manuscript should avoid high-magnification reduction and enlargement, because these will cause the loss of layers.

Flexographic printing has unique flexibility and economy, which is beneficial to environmental protection and conforms to the hygienic standard of food packaging printed matter, which is one of the reasons for the rapid development of flexographic printing technology abroad. However, from the domestic situation, offset printing is more popular, gravure printing occupies a large market in the packaging industry, and flexographic printing started relatively late. Although great progress has been made in recent years, it still lags far behind the international advanced technology level.

From the perspective of manuscript design and plate-making technology, flexographic printing technology is self-contained and unique, and its plate-making technology is basically as follows:

Original manuscript → electronic color separation or photography → positive and negative images → back exposure → main exposure → development and development → drying → post-processing → post-exposure → pasting.

Compared with offset printing, there are mainly the following differences:

1, reproducible color value range. Offset printing is 1% ~ 99% (or 2% ~ 98%), and flexography is 3% ~ 95%.

2. Dot expansion (50%). Offset printing 15% ~ 20%, flexo printing 30% ~ 40%.

3. The number of screening lines. Generally, the maximum offset printing is 175 lines/inch, while the number of flexographic screening lines generally does not exceed 150 lines/inch.