Offset production, often because of paper off powder and stop cleaning plate and roller. Paper hair loss powder on the impact of printing there are two main aspects: First, paste version, the second is in the blanket or printing plate on the pile of ink.
When the paper off powder, the paper powder or filler and ink will be mixed together, and then gradually accumulated to the blanket, the formation of heap. When the heap begins to form, the printed image becomes rough, due to the mixing of the paper powder and the ink, forming a bulge on the rubber roll, resulting in difficulty in ink transfer, that is, heap hiding the ink transfer, and the part of the ink is not transferred to the paper , So that the image color is bleak, expression is reduced. If the area of the ink is small, a small white spot will be produced on the printed image; if the area of the heap is large, a large white spot will appear on the printed image.
Jubaolong company uses a split two-color offset printing machine for printing production, and were selected 70g / m2A grade double adhesive tape, 70g / m2B grade double adhesive tape and 70g / m2 light paper as the substrate, looking for the impact of offset paper off powder the elements of. The relevant production conditions are: printing speed 6000 sheets / hour, printing workshop temperature 23 ℃, humidity 50% ~ 60%, ink viscosity 30Pa · s. Printing the above three kinds of paper, the plate on the hair drop powder situation as follows.
(1) A-level Shuangjiao paper hair loss powder rarely, half-way almost no need to stop cleaning blanket, suitable for high-quality offset printing.
(2) B-level double-paste paper there is a slight drop off powder, but within a reasonable limit, the occasional need to stop cleaning blankets.
(3) light paper hair loss powder phenomenon is more serious, resulting in the printed surface appears some obvious white spots, printing need to often stop wiping blanket, so apply to the general offset.
Therefore, we speculate that the main reason for paper loss of paper powder and paper tightness of the two major factors.
1. paper moisture content
The moisture content of the three kinds of paper was measured by wet weight method, and then the paper was dropped under three kinds of water content under constant printing conditions.
The quality of the three types of paper before and after drying in the blast oven is shown in Table 1, where: water content = (paper quality before drying - quality of paper after drying) ÷ paper quality before drying × 100%.
Under normal circumstances, as long as the paper moisture content in the normal range (8%), the higher the water content, the more conducive to the paper fiber swelling and paper fiber intertwined, thereby increasing the paper surface strength, The probability of falling powder.
2. Paper tightness
The thickness of each sheet is calculated by calculating the thickness of each of the three sheets, and the tightness of the three patterns is calculated according to the formula: paper tightness = paper weight ÷ paper thickness, as shown in Table 2 above.
Found that the tight relationship between the three patterns: A-level double-binding paper> B-level double-adhesive paper> light paper. It can be seen that the smaller the tightness of the paper off the powder powder more serious, so we initially determine: to a certain extent, the greater the paper, the higher the strength of the paper surface, hair loss powder phenomenon less.
Under the normal printing conditions (printing speed, ink viscosity, workshop temperature and humidity), through the experiment to verify the characteristics of the paper itself on the impact of paper off powder, hoping for the majority of printing practitioners to provide some reference.
