Aluminum plate coating and packaging processing

First, glazing

Glossing, also known as cover light, is to apply a layer of varnish to the surface of the printed pattern (just like a protective net on the cover, so it is called cover light). The purpose is to enhance the adhesion of the ink and protect the printing pattern. Scratched by hard objects. After printing on the aluminum plate, the hardness of the surface of the printed pattern is significantly improved (up to 4H pencil hardness), the brightness of the printed pattern is also enhanced, and the visual effect is more ideal. However, if the coating operation is not properly handled, the negative impact on the product must not be underestimated. The following is the main relationship between coating and print hardness and brightness, the color of the printed aluminum plate after coating, the impact of the coating process of the coating machine on the product, and the effect of the insert plate on the quality of the coated aluminum plate is analyzed as follows.

1. Hardness and brightness after printing on aluminum plates

The varnish used in the printing of aluminum plate is thermosetting, which must be cured by heating. Therefore, the hardness of the printing pattern after glazing is directly related to whether or not the varnish can be completely cured during baking. Hardness testing method according to the national standard "coating hardness pencil test" GB/T6739-1996 test, which "coating hardness pencil test" divided into two test methods: test machine method and manual method. Materials and instruments used in the test machine method: A set of Chinese high-grade drawing pencils (9H, 8H, 7H, 6H, 5H, 4H, 3H, 2H, H, F, HB, B, 2B, 3B, 4B, 5B, 6B, Among them, 9H is the hardest, 6B is the softest, Great Wall advanced drawing eraser, 400 water sandpaper, pencil sharpener, pencil hardness tester. The manual method uses the same material as the A method except that there is no pencil hardness tester. The manual method is usually used to test, the detection instrument is simple and easy to operate. The hardness of printed aluminum plates is not less than 4H pencil hardness. During the test, it was found that the same varnish baked at different temperatures had different hardness. In the range that light oil allows baking, Wen Hao Xu Bo

High gloss oils have good hardness, and different varnish oils have different optimal curing temperatures. Therefore, different baking temperatures must be used according to the different varnish during production, so as to avoid the hardness of the product being hard to be set by blindly setting the same temperature.

The brightness of the printed aluminum plate is related to the film thickness of the varnish. The so-called "film thickness" is the dry film weight per unit area after the varnish or coating is cured, which is usually expressed in g/m2. Film thickness measurement in production can use advanced film thickness gauges, but also can use simple, practical measurement board. The measurement of the measuring plate is to coat the varnish or paint with a 10cm*10cm aluminum piece, and subtract the weight of the unpainted varnish or coating aluminum piece by the weight of the baked aluminum piece and multiplied by 100 or the film thickness. The higher the film thickness of glazing products in a certain range, the brighter the prints, but will also increase the cost of the product accordingly, so manufacturers should pay attention to the control of film thickness, neither too low (too low printing products without brightness), nor Too high (the high cost will make the manufacturer almost unprofitable). Taking Guangdong Baiyun BV8290 varnish as an example, it is recommended that the film thickness be controlled between 2 and 3 g/m2.

2. Pay attention to the color change of printed aluminum plate E after baking

After the light baking of some printed aluminum plates, the color of the printing pattern changes, and in particular, spot color inks are the most common. There are two main reasons for discoloration. One is the discoloration of the ink and the other is the discoloration of the lacquer, and the degree of discoloration of different varnishes is not uniform. Therefore, the production process color card should include the printed sample before coating and the printed sample after polishing, as a reference before coating. If the varnishes used for varnishes are replaced, prenatal tests should be carried out to confirm the effect of lacquer on the color of the printed aluminum sheet so that pre-production can be mastered; during production control, the effect of varnish on the color of the printed aluminum sheet is minimized.

3. Coating process coating machine impact material quality of printed aluminum

At present, light is usually printed on aluminum plates using a coater. The varnish coated with a varnish is subjected to a circular motion, and the centrifugal force tends to leave the varnish off the rubber roller. When glazing, if the operator does not properly handle, it is easy to cause the glazing oil to be thrown onto the printed aluminum plate in strips, and after curing, the plane of the printed aluminum plate is highlighted, and the appearance effect of the printed aluminum plate is affected. Therefore, ensure the normal operation of the equipment and check the operation of the equipment at all times during the production process.

4. Putty Adhesion to the Surface of Aluminium Prints Affects Product Quality

The gusset plate is an aluminum plate printed on the glaze baking, because the aluminum plate conveying posture is not correct, resulting in an angle of the aluminum plate is inserted into the flower iron frame. The gusset plate will agitate the dust deposited on the bottom of the oven, so that the dust adheres to the lacquer that has not been completely cured. After solidification, black impurities are formed on the surface of the aluminum plate print, resulting in a product failure. Therefore, during the glazing process, the entrance of the oven should be assigned a special person to inspect the transport status of the aluminum plate, and check whether there is a gusset plate at the tail stack, and if any, check the machine for downtime and take remedial measures.

Second, packaging

The packaging requirements for aluminum plate prints are more stringent because aluminum plates are soft, easily deformed, and easily scratched. Unqualified packaging will cause quality defects such as scratches and collisions on the surface of aluminum printed products. Therefore, the packaging must be designed according to its nature. There are strict requirements on the packaging weight and packaging methods of aluminum plate prints. Only after complying with the corresponding requirements can the products be satisfied with the quality of printed aluminum plates after the products are delivered to customers.

1. Packaging product weight requirements

Aluminium plates are metal, and aluminum plates per unit volume are heavier. This requires that the weight of each package cannot be too large, otherwise the package cannot withstand it. The weight of a large package must not exceed 500 kg. Excessive weight can cause sliding of the aluminum plate and form friction scratches.

2. Packing

Printed aluminum plates can be easily scratched and scratched, affecting the quality of the product and causing serious returns. Therefore, according to the product transport distance and the degree of slippery, the following three kinds of packaging are formulated.

(1) Ordinary printing aluminum plate, short-distance transportation (within 100 kilometers range): smooth wooden pallets at the bottom to prevent aluminum plate from soft deformation, upper soft paper shell corners, fiber board protection edges, iron waist Play #word to prevent folding and bulking.

(2) Ordinary printing aluminum plate, long-distance transportation: the bottom uses a smooth wooden pallet to prevent the aluminum plate due to soft deformation, the upper side of the triangle guard, use iron waist to fight # word to prevent folding, bulk bag, and then use wooden The box was trapped, the standard definition was up and down, and then the iron waist was used to play the # word package.

(3) The packaging requirements for plates with adhesives and back lubricants are the same as those for long-distance transportation of printed aluminum plates: The plates are relatively slippery, and the printed aluminum plates of the parts are gently pushed without being packed. It will fall to the ground. At the bottom, smooth wooden pallets are used to prevent the aluminum plate from soft deformation, and the upper part is protected by triangle iron. The iron waist is used to fight the # character to prevent folding and bulking, and then it is trapped in a wooden box, the standard is cleared up and down, and then iron is used. Waist playing # word package.

Polishing and packaging are the post-printing processes for aluminum printing. Although they are final processes, their importance cannot be ignored. Many finely-printed aluminum plates have failed to pass the light or packaging, resulting in unsatisfactory printing of aluminum plates, which has delayed the completion date and caused many economic losses. ※

Reprinted from: print magazine Author: Hao Xubo