Flexo printing preparation before starting

Years of flexographic printing practice tells us that meticulous prepress preparation is very important. If the pre-press work is not done properly, carelessly, or hastily, then there will be an embarrassing situation where small problems continue to arise and large problems become a problem. This not only wastes raw and auxiliary materials, but also lowers the product's pass rate and affects the product's Quality, causing serious economic losses, but also may delay delivery time and reduce the credibility of the company. Therefore, I believe that optimizing human resources and carefully doing every preparatory work before flexographic printing is critical to our work.

The specific preparations before the flexible booting mainly include the following points:

First, check and maintain equipment

Equipment is the basis for producing quality products. Careful maintenance and maintenance of machinery and equipment are essential. First of all, carefully clean the surface of the machine, paper feeding, static electricity, and dust removal parts, and scrub all the rollers of the machine to reduce dirt and stickiness in the printing process. Then, lubricate the machine's gears and each fill port to reduce wear. Also check if there is any looseness in the drive chains and connecting parts and master the working status of the equipment.

Second, master the pre-press process requirements

1. Familiar with the standard proofs, including the color status of the proofs, the main features of the pictures and the main technical requirements.

2. Review the printing sequence. If there is anything wrong, you can propose amendments. Under normal circumstances, the small ink, line text, four-color small graphic, on the front printing, it is easy to dry, oven temperature is low, paper deformation is small, overprinting is relatively stable; large field, gold ink, silver ink and carrying ink Large amounts of graphics are printed at the back.

3. Understand the main performance characteristics of printed materials, in particular to master the main properties of the ink and solvent used.

Third, the preparation of the inspection and paste

For the plate roller used, the same manufacturer's plate roller should be used. Check roll bearing rotation is stable, there is an exception in time to replace. Check if the gears are clean and clean with kerosene. Apply grease afterwards. Remove the spool shaft and inspect it for damage. Clean the ink in the ink tray and ink fountain and clean the ink pump, hose and ink roller. Clean plate cylinders and anilox rollers.

Remove the new plate before printing, clean the front and back with alcohol, clean the residue, and then cut the plate. According to the number of teeth of the plate roller cut out the appropriate size plate.

If the size of the crop is slightly larger, after the plate is attached, the interface of the plate will be redundant. Some of the colleagues will be afraid of the trouble and cut it off directly on the platen roller. This will inevitably scratch the plate roller. As it happens, there will be multiple injuries on the plate roller.

If the size of the cutting is slightly smaller, the gap between the attached plate interface is larger, and the sealing tape cannot be evenly adhered to the top plate. The foam will be blistering. When the printing is performed, the solvent will infiltrate, causing the plate interface. There is a lifting of the sealing tape, and unnecessary dirt spots appear on the surface of the printed product.

Therefore, it is best to use a sharp blade to cut open at the time of cutting. It is neat and clean and does not drag on. Blunt knife cutting, after the printing plate is cut, there will be many burrs on the edge, which will affect the overprint of the product. The sticker tape should be flatly pressed against the surface of the printing roller and must have no air bubbles. Carefully align the lens with the paste to ensure that the plate overlay line is horizontal and vertical. Each plate must be repeatedly checked and verified before it can be sealed. The edge of the sealing tape should be pressed tightly with the back of the blade or with a sleek tool.

Fourth, matching anilox roller and adjusting pressure

Select the corresponding anilox roller according to the process sheet. When selecting, there may be several anilox rollers with the same number of lines, the length of time used, the situation of surface wear is not the same, some even have scars, and the use conditions of each anilox roller must be well known. One can be based on the product graphic features to avoid blindness, it will also be handy.

Flexo printing belongs to light pressure printing, and the adjustment of pressure is one of the keys to the success of printing. Since the pressure adjustment range is very small, it should be carefully handled during adjustment. The requirement of pressure for flexo printing is very strict, which directly determines the reproduction of the graphic and affects the printing quality. With years of experience in operating the machine, I believe that it is best to use the same roll with a plate and a feeler gauge to adjust the pressure in each color group, so that the adjusted pressure is almost the same size.

V. Preparation of ink

1. Before starting the machine, it is necessary to fully stir the ink, especially if the ink is stored in the warehouse for a long time, the viscosity is relatively large, and after being fully stirred in the vat, it is poured into the keg and the amount is enough to be used on the machine. According to the viscosity of the ink, add a small amount of pH adjustment solution, add special thinner to the gold and silver ink, and then stir it clockwise or counterclockwise in a direction so that the pigment particles are evenly distributed in the connection material, so that the ink printing The best fit.

2. For the old ink or crusted ink, it is best to use 300 mesh mesh filter. The gold and silver inks can be filtered by thicker mesh cloths to remove the solidified particles of the crusts, to avoid damage to the doctor blade and anilox roller, and to prevent the printed products from being dirty.

3. In general, the stability of the ink is poor, and the color of the new ink will be deepened when it is left for a while. If there is a spot color ink product, it is best to adjust it proportionately one or two days before printing, stir evenly and thoroughly in one area, and then place the lid so that the stability and printability of the spot color ink will reach the best state. .

Sixth, check the squeegee and knife holder

When installing the squeegee blade, carefully inspect the blade for damage, and if it can not be used in order to reduce waste and save cost, it can be used in color groups that are out of reach. When the ink tray is not filled with ink, the anilox roller cannot rotate in contact with the squeegee to avoid damaging the anilox roller. When the squeegee is working on the anilox roller, check the length and position of the squeegee and the position of the anilox roller. Check if there is ink on both sides of the anilox roller. The length of the doctor blade and the length of the anilox roller are preferably the same, which can reduce the waste of ink and the generation of ink flying in the high speed operation of the machine.

Seven, the control of printing tension

In flexographic printing, the printing tension refers to the sum of the tension generated by the tensioning device on the printing material and the tension of the printing material in the printing. The change in printing tension is one of the main factors that affect the accuracy of overprinting and determines the rate of scrap. For the unit type flexo press, the tension between the various color units does not need to be adjusted, in order to eliminate the interference on the tension of the paper strip when the printing plate cylinder is pressed, the diameter of the impression cylinder of each unit should be larger than that of the previous group. ~ 0.02mm, the impression cylinder of each unit can not be arbitrarily switched.

The registration of the unit type flexographic press is often not ideal at low speeds (15m/min). This is because the frictional resistance and inertia of the machine parts have not yet entered the steady state. Once the machine enters the high speed state, the registration effect is achieved. Can be improved. Therefore, when the machine is operating at a low speed, the coarse adjustment can be completed as soon as possible (the registration error is within 1mm), and then the registration accuracy is adjusted on the main console with the increase of the vehicle speed.

Eight, post-processing preparation

Under normal circumstances, the products are cut into large pieces after printing, and then hot stamping, embossing, die cutting and other post-processes. If the product printed by the flexographic printing press belongs to the in-line formed product, the indentation is formed by the yin-yang indentation roller compressing the paper under a certain pressure. Put the upper roller on the machine and carefully check whether there is any foreign matter in each indentation line groove to avoid damage to the positive tool or the burst line after the machine is on.

When the mold is lifted on the machine, it cannot hit the equipment and the used tool. Carefully adjusted after installation, to ensure that the body and rely on the outside of the roller body is vertical, to the positive roller, negative roller zero-position to lay a solid foundation. The same method to install the positive roller, the positive roller, the negative roller alignment zero position, can not be sloppy. After meshing, use a hand to move the machine to ensure smooth running. Then install the pressure frame and pressure gauge. When the machine is running at a low speed, look at the pressure gauge. At the same time, slowly pressurize both sides of the machine. If the indentation line is not sufficiently full, it means that the alignment of the yin and yang roller is incorrect. The positioning gear of the male roller needs to be fine-tuned. After the adjustment, the gear is locked and greased.

There are many preparatory work before flexographic printing. If there is a preparatory work that is not in place, it will affect the quality of printed products to some extent. "Details determine the success or failure" is the best interpretation of the pre-press work and has an important role in improving the quality of printed products.