Sheet-fed offset press connection device features (2)


Disadvantage

(1) When printing on aluminum foil, the drying time of the ink is affected. If necessary, a drying device or a coating and drying device should be added.

(2) In the current hot stamping structure, the utilization rate of aluminum foil is low, especially single-scroll type. The use of multi-scroll type can improve the utilization of aluminum foil and reduce the cost of use.

Fourth, connect the light and dry

Now packaging can not only protect the goods, but more importantly, it can stimulate people's desire to purchase, and even become one of the criteria for deciding to purchase. Therefore, about 80% of folding cartons, 70% of labels, and many books and magazines use glazing technology to attract people's attention.

Standard offset printing units can also be glazing or printing metallic inks, such as coated offset printing inks. However, due to the thin ink layer and the use of wetting liquids and additives, the glazing effect is not good. Therefore, at present, the coating device mainly adopts flexographic printing, and generally there is one or two separate coating units. When the coating requirement is very high, two coating units are required. The first coating unit is generally water-based varnishes to act as a seal for the ink and the surface of the paper to reduce the penetration of bleed inks due to the first coating. Loss of light caused by paper.

After drying, the second coating can make the distribution of the varnish even more uniform, forming a high-gloss glazing layer. The second glazing unit can use UV varnish, its effect is better than pure UV, it can also use water-based varnish to further improve the glazing effect, or use a special effect pigments to show special effects.

Double glazing units are generally located at the rear of the printing unit, and drying units are provided behind each glazing unit. If it is necessary to apply opaque white or a special effect primer to the surface of the substrate prior to printing, a flexographic coating unit and drying device should be installed before the first printing unit. The selection of coating units should be based on the requirements of the printed matter.

(1) Selection of oil supply mode: The coating machine is mainly provided with different types of light oil. The amount of varnish can be adjusted according to the need. Generally, the gap or pressure of the two rollers is adjusted, and the rotation speed of the roller is changed. This kind of mechanism is currently widely used, but adjustments are troublesome.

The newly developed closed type varnish supply device consists of an anilox roller and a chamber scraper. The cavity box is equipped with two scrapers, one of which is applied with a lacquer evenly along the direction of rotation of the anilox roller, and the other is rotated against the direction of the anilox roller to scrape off the excess coating on the anilox roller. The size of the anilox roller access hole determines the amount of varnish used, and the amount of varnish is easy to control.

If you need to change the amount of polishing oil, you need to change the anilox roller, therefore, the coating device is often equipped with 2 to 3 different network size anilox roller. The standard holding oil amount of the general anilox roller is 20 cm3/m2, and the thickness of the varnish layer printed on the substrate is about 8 μm, and the basis weight is 8 g/m2. This chamber type coating oil supply device can prevent dust, flying ink and varnish from drying up the skin. The installation position of the cavity squeegee must be correct, otherwise it will not work properly. The general cavity type coating oil supply device needs to be equipped with an automatic polishing oil pump for automatic coating of oil.

(2) Selection of glazing roller: When coating all, the coating plate is generally a blanket. In the case of partial coating, the coating plate is generally a flexographic plate, which is mainly composed of a rubber plate and a polyester plate.

Whether the glazing roller needs to be adjusted depends on the coating requirements. Only the entire coating, roller generally do not have to adjust. In order to accurately overprint the part when the light is applied, it is required that the glazing roller can be adjusted axially and circumferentially, and when the requirement is high, the diagonal adjustment of the roller is also required. Medium-to-high-end machines generally control the adjustment of the glazing roller on the center console.

After drying, it must be dried immediately. Sheet-fed offset presses are often based on the needs of the print, water-based coating, UV coating, and the requirements of the print and change at any time. There are roughly two ways to dry it. That is, the use of oily ink + water-based varnish, IR (far-infrared) and/or hot air drying; UV ink + UV varnish, using UV dry curing. Of course, it can also be an IR/UV combination. The specific choice should be based on the varnish and product use. There are three types of UV curing devices, namely, the inner baking plate method, the drying unit pattern, and the long line conveying method. The inner baking method does not require a special unit and is generally installed between the units. It is convenient to change the installation position, but the drying capacity is the lowest among the three methods. The drying unit method requires special units but the highest drying capacity.

The long-distance transmission method is to increase the paper-feeding distance. After the last coating machine, IR, UV and hot air drying equipments are installed, taking into account IR/UV drying methods (varying drying methods or drying lamps for varnishes). The plate method and the drying unit method are difficult to use both IR/UV drying methods, and in order to reduce the thermal deformation of the paper, a low-heat type UV device or an additional cooling device (usually behind an extended UV lamp) can be used.

In order to adapt to the variability of the surface of a sheet-fed offset printing machine, generally in the rear of the last printing unit or coating unit of a sheet-fed offset printing machine, infrared, UV, hot air drying devices are also provided to form an elongated delivery device. Prints need to open different drying devices. Such as water-based glazing, infrared and hot air drying devices, both with a very good drying effect. UV glazing starts the UV drying device.

In general, the extended delivery device is also equipped with a cooling device (recycled cold air), which cools the printed paper on the one hand and helps the ink dry on the other.

In order to ensure proper ink drying between the various colors of the printing unit, it is necessary to install a UV or infrared drying device between the printing units and both can be replaced.

V. UV offset printing

UV printing was first applied on screen printing and then applied on flexo printing. UV offset printing has developed greatly in the past 10 years. UV offset printing can be roughly divided into color printing and surface finishing. Color printing and conventional printing are basically the same. Surface finishing such as UV glazing can be used instead of lamination, either fully or partially. Using UV ice or UV matte ink printing, you can form a "three-dimensional" image and colorful texture effects on the surface of the substrate. In recent years, UV offset printing and composite ink printing have emerged with many advantages. Of course, there are also respective problems.

Disadvantage

(1) Special supporting device: printing equipment

UV offset printing must be equipped with special rubber rollers, printing plates and blankets, and special cleaning agents are needed for cleaning; ink rollers need to increase the water cooling system; due to poor UV ink overprinting, it is generally necessary to add special UV inks between the units. Curing drying device. (To be continued)

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