HOW TO ADJUST THE PRINTING PROCESS FOR DIFFERENT BASE PAPER

The common varieties of base?paper used for corrugated box outer lines?are: cardboard, linerboard, kraft paper,?yellow board, white board and single-sided coated white board. The physical and chemical indicators, surface properties and printability of these papers vary considerably due to differences in the copying materials and papermaking processes of each type of paper. The following is a discussion of the problems that the above-mentioned paper products bring to the process of flexo?printing on corrugated board.

Problems caused?by low grammage base paper

The use of low-grain base paper as the outer line?of corrugated board can lead to the problem of exposed fluting on the surface of corrugated board. This can easily cause fluting and failure to print the required graphic content at the low concave part of the flute. For the uneven surface of corrugated board caused by exposed fluting, a flexible resin plate with good resilience should be used as the printing plate to overcome the defects of unclear printing and exposed bottom. In particular, A-type corrugated board produced from low-grain paper will suffer greater damage to the flattening strength of corrugated board when printed on a flexo printer, and to the edge pressure strength of corrugated board after it has passed through the printing and impression rollers.

If there is too big?a difference in the outer liner and inner liner?of the corrugated board, it can also lead to warping of the corrugated board produced by the corrugator. Warped cardboard can lead to inaccurate overprinting and slotting, so warped cardboard should be flattened and reprinted. Forced printing of uneven corrugated cardboard can easily lead to gauging. It can also cause the thickness of the corrugated board to drop.

Problems caused by different surface roughness of the base?paper

In the surface of the rough, loose structure of the base?paper printing, its ink permeability, printing ink drying fast, and in the surface of the smoothness of the high, dense and tough fibre paper printing, the ink drying speed is slow. Therefore, in the rougher paper, the amount of ink applied should be increased, and the amount of ink applied should be reduced on the smooth surface of the paper. In the absence of sizing on the paper printing ink drying fast, and after the sizing of the paper printing ink drying slow, but the reproducibility of the printing pattern is good. Such as coated white board?because of ink absorption than the cardboard, yellow?board , ink drying slow, and smoothness than the?cardboard,?linerboard, yellow?board, therefore, in its printing on the small dot resolution is also high, the reproducibility of its pattern than?the?cardboard,?linerboard, yellow?board to good.

Problems caused by?differences in base?paper absorption

Due to differences in raw materials and base?paper sizing, calendering, coating differences in absorption energy is different, such as in single-sided coated white board?and kraft paper?for overprinting, because of the low absorption performance, ink drying speed is slower, so should reduce the concentration of the previous ink, improve the viscosity of the ink behind. And the lines, text, small patterns in the first colour printing, the fully?solid?printing should be?in the last colour printing, which can improve the effect of overprinting, in addition to the dark colour in front of the printing, the colour shallow in the back of the printing, can cover overprinting errors, because the dark colour coverage force is strong, conducive to overprinting standards, while the light colour coverage ability is weak, placed in the back of the printing?even if there is a run gauge phenomenon is not easy to observe.

The different gluing?conditions on the surface of the base?paper will also affect the amount of ink absorption. Small gluing amount of paper to absorb more ink, Large gluing amount of paper to absorb less ink, so should be based on the gluing?state of the paper, adjust the gap between the ink rollers, that is, adjust the gap between the ink rollers, to control the inking of the printing plate. It can be seen that the base?paper into the factory should be the base?paper absorption performance of the condition of the test, and provide the related performance parameters to ?printer?slotter operators and ink?staffs, so that they can facilitate the inking and adjustment of equipment. The ink viscosity and PH value are adjusted for the absorption status of the different papers.