How to improve the quality of carton printing

As we all know, the key factors affecting product quality are equipment, raw materials, personnel and the environment. The same applies to the carton packaging industry. Here, we will briefly describe the experience of improving the quality of carton from the perspective of ink printing.

First, ensure the clarity of printing

Firstly, the printing plate should be made of wear-resistant, moderately elastic, and high-quality materials. The thickness of the same plate should be the same. The thickness of the resin plate should be no less than 4mm, and the rubber plate should be 6~7mm. Whether it is to use a dark film or a handmade knife, the layout must be neat. The depth of the lines of the pattern should not be less than 3mm. The arrangement of the text patterns should not be overcrowded. The arc should be sleek, uniform in thickness and straight and smooth. When printing, the ink should be properly lightened, the ink layer of the ink coating roller should not be too thick, and the pressure of the roller should be moderate, so that the printing ink is evenly distributed, and no obvious dents on the box surface are preferred. Do not increase the ink concentration, increase the pressure of the ink roller to improve the printing effect. This not only fails to achieve the ideal purpose, but also results in layout paste and poor printing quality. In particular, the text is small, the pattern is complex, the lines are delicate, and the printing requirements are accurate. With the high layout, the disadvantages are even more pronounced; the speed of the printing press can't be lower than 800 rpm, the speed is too slow and the ink in the box is uneven, and there is a phenomenon of exposed bottom. Too fast ink is too thick, the layout is easy to blur, but also to prevent paper hair, paper scraps, etc. into the printing press stick to the printing plate, if there is a piece of paper glue sticking, to immediately stop, wipe with a rag and dip in alcohol.

Second, the printing color should be pure, no color difference

The pros and cons of water-based inks are the key to the pure and bright color of carton printing. Therefore, great care must be taken in the selection. There is no obvious difference between high-quality inks and color scales. The hand is delicate, thick, and the concentration is suitable to add water or alcohol solvent to dilute without precipitation and agglomeration phenomenon. The foam is generated by stirring with a wooden stick. It is mixed with other inks, and the affinity is good. Solubility, pure ink, no abnormal reaction. On the contrary, it cannot be used.

It is best to print batches at one time when printing, otherwise, the same barrel of ink is used, and color differences also occur. The reason is that the original ink is diluted with water or an alcohol solvent and is not sealed. When it is exposed to the air for a long time, the chemical components in the ink react with the oxygen in the air, that is, the pigment is reduced, and the strong light can also decompose the ink.

Third, to prevent the overprinting and ghosting of coated whiteboard carton printing

When the coated whiteboard paper is manufactured, the coating liquid used for coating the whiteboard contains glue, and the surface of the high-grade whiteboard paper is coated with a small amount of gloss wax, so when the paperboard with whiteboard is used for printing, the printing plate and the whiteboard paper are printed. There is slippage at the moment of contact. In addition, the pressure of the printing plate is too heavy, the water-based ink is not easy to infiltrate, and the printed carton ink is dried slowly. The printing job is continuous, and the printing products are stacked one on top of the other. The scratches formed on the box surface are superimposed.

To solve this problem, the ink should be lightened with ethanol, do not use water, because it is not volatile, is not conducive to the drying of the ink; printing pressure is properly reduced, the printing speed should not be too fast, not more than 600 rev / min is appropriate. Before the stacking of printing presses, an exhaust fan or hot air drying box ink is installed.

Fourth, ensure overprint accuracy

The overlay accuracy depends firstly on the precision of the device and the adjustment of the feeding section to push the cardboard in parallel. In addition, the layout is made, assembled, and corrected. The following is a discussion of overprint accuracy in terms of layout collage.

After the plate is ready, take a piece of 0.5mm thick clear polypropylene plate, draw a vertical line at the center of its length, and then press the size of the carton to be printed. Draw the length, width and height of the line with a small pen, and then follow the sample or sample box. According to the production notice to impose imposition. After positioning the layout, use the pen to draw the line on the edge of the printing plate. After that, the same size plate base prepared in advance is overlaid on the base plate of the well-drawn line, and all edges are accurately traced (for example, three colors can be used to overprint a plate base). ), Finally, press the printing color, and the corresponding printing plate is firmly stuck in the painted position with neoprene. Then use the double-sided adhesive to attach the printing plate to the roller of the printing machine. The center line of the printing plate can be aligned with the centerline of the platen roller of the printing machine. As long as the position of the imposition is accurate and other objective conditions are satisfied, overprinting is accurate.

Fifth, the effect of full version printing on carton strength

We know that when the carton is printed, the corrugated cardboard is formed by the paper guide rollers and the printing rollers of the printing machine and transferred to the grooved portion. After the paperboard is pressed by the roller during the transfer process, the physical shape of the paperboard is changed by different procedures. Affect the strength of the carton. Full-plate printing is particularly prominent. Compared with no-printing, the cardboard box of the same material has to be reduced in strength by about 30%. Therefore, the production process must be very careful and can be mitigated by the following measures:

First, properly adjust the gaps of the paper guide rollers of the printing press so that the paperboard passes smoothly without deformation (slightly smaller than the paperboard thickness of 0.1-0.15mm);

Second, the pressure of the printing plate can be adjusted to meet the requirement of clear printing.

Thirdly, the speed of the printing press should be properly increased (above 1000 rpm), so that the board can pass through the printer as soon as possible to reduce the time for the board to withstand the pressure.

Sixth, carton leakage version timely reprint

The actual production of a printing machine without a computer stencil printing device is difficult to avoid because of the operator's negligence. After similar things happen, remedial measures should be taken promptly. If only the notch is cut, the slotted knife can be unloaded, the missed layout can be subsidized to the corresponding position, and then the other plates can be unwound and can be reprinted. However, the speed should not be too fast, or the effect of overprinting can be avoided. Poor or layout moves. If the printed carton has been nailed, in addition to the plate surface processed in accordance with the above method, but also adjust the guide roller gap to the shape of the carton is not passed through the deformation is appropriate, the printing roller pressure must be adjusted, and then transfer the paper Baffle, determine layout position, single delivery when printing.

Seven, thin cardboard printing notes so-called thin cardboard, namely D, E and other fine corrugated cardboard, these thin cardboard after the printing of the application of flat pressure die-cutting machine stamping, due to small quantities or customers only once, plus the die-cutting The high cost of the stencil, so the production of printed slotting instead. In actual operation, because the paperboard is too thin, the printing speed must be slowed, but the paper feeding device is not difficult to push paper, that is to push multiple paperboards at the same time into the printing press, resulting in a lot of waste. To solve this problem, you can use a single machine slot, nail printing and then printing, but according to the two sides of the carton, different loading, two times to complete a complete layout of the carton.

Eight, warpage cardboard to prevent running board, slotted go

The warped cardboard printing adopts single sheet feeding, low-speed operation, and appropriate adjustment of the amount of suction, adjusting the slot position of the printing product in time according to the layout and slotting, and correcting it in reverse. The cardboard with serious warpage is selected, every 3 to 5 sheets of positive and negative stacking are flattened and reprinted with a heavy object, or folded along the indentation line in the opposite direction to the warpage.

In short, in actual production, under specific circumstances, we must also be flexible in dealing with objective conditions. The above is for reference only, because the author's level is certainly limited, and is willing to discuss with peers.