Acceptance of paper outer packaging
At present, lithographic paper packaging mainly uses wooden plywood packaging and wooden box packaging
Two basic forms. Qualified lithographic paper generally has more than two layers of wrapping paper in its appearance and packaging, and then is packed with wooden boards and tied with iron strips. The packaging paper used mainly includes wax paper, tar paper, kraft paper, snake skin paper, etc. Indicate the words "moisture-proof", "do not throw" on the wooden plywood or wooden box, and some also indicate the direction of the paper. The certificate of conformity of the product should also be posted on the wooden plywood or on the wooden box, and the product name, specifications, order weight, order number per piece, paper grade, implementation standard, production date, name of the production enterprise, etc. should be marked. The outer packaging should be intact and free from deformation and damage. If the outer packaging is severely damaged and the paper is exposed outside the packaging, it should be rejected without hesitation, or other measures should be taken to avoid unnecessary losses. The acceptance of paper outer packaging is a basic acceptance, and we must strictly grasp this point.
Acceptance of appearance after removing outer packaging
After removing the outer packaging of the paper, first check whether there is a quality inspection sheet, and then check the paper phase and color of the paper.
The basic characteristics of normal paper are good flatness, that is, the paper is flat on the paper and flat on the end. As for a piece of paper, it is relatively difficult to judge whether the paper phase is normal unless the paper has been severely deformed.
The usual method is to untie the paper bag and pile up 1m high to see if the paper phase is normal. When the paper phase is not normal, it shows a variety of shapes, the common ones are wavy and dish-shaped. Other shapes such as mountain shape, valley shape, angle warp shape, bag shape, inclined shape, valley shape, curled shape, saddle shape, etc.
The reasons for these poor paper phases are various. In summary, there are mainly the following aspects: â‘ The water content of the entire web is uneven, thus showing uneven local shrinkage; â‘¡ The thickness of the paper during the papermaking Uneven; â‘¢ The front and back sides of the paper are inconsistently stretched, especially single-sided coated paper.
In addition, you can also see from the side of the paper pile whether the color of the paper is uniform. In any case, the paper supplied in the same batch must have the same whiteness, uniform color tone, and small color difference. Otherwise, after the printed matter is bound into a book, there will be obvious tonal stratification in the parts of the sky, feet, cuts and so on.
How to detect paper size
According to national standards, the measurement of paper size should be made with a steel tape measure with a length of 2m and an accuracy of 1mm. When measuring, 3 samples should be taken arbitrarily in the same package, and the measurement results are expressed in all measured values, accurate to 1mm. The allowable error of paper length size is ± 3mm. Skewed paper may cause insufficient or excessive paper size, and the angle between the long and short sides of the paper may not be at right angles. Therefore, in addition to measuring the length of the paper, the skewness of the paper should also be measured. The allowable error of paper skewness is 3mm ~ 5mm.
In addition, the size stability of the paper can also be expressed by the paper's expansion and contraction rate. The paper elongation in water can be used to measure the paper acceptance. Cut a horizontal strip of paper with a size of 2cm × 20cm and place it in water for 1h ~ 2h to fully swell it until the size remains unchanged. Take it out and lay it flat on a glass plate. Long rate, and compare with the standard.
If the paper is unhealthy after unpacking, and the elongation of the paper in water is too large, it is best to reject such paper to avoid future troubles.
How to detect paper surface strength
Paper surface strength is a very important property of paper. Each printing paper has certain requirements.
Therefore, the country has made clear regulations on the surface strength of each printing paper.
If the surface strength of the paper fails to meet the requirements of printing, then the paper will fluff, de-powder and even delaminate during printing. Therefore, the inspection of the surface strength of the paper is also an important content of acceptance paper, but often many printing companies ignore it, so a variety of printing failures occur during printing.
When accepting paper, you can use some simple methods to judge the strength of the paper surface. Such as using the Denny's wax stick test. Although this method has some shortcomings, it is still a relatively simple method for determining the anti-fluff ability of a particular paper.
During the measurement, the end of a certain wax stick is melted and pressed against the surface of the paper to be tested. After 15 minutes, it is quickly pulled up and the peeled paper wool or paper powder is checked on the end surface. Another simple method is to use a slightly wet finger (usually a thumb) to press the paper surface heavily, and after a little rubbing, quickly separate, and observe whether the finger surface is stained with short fibers or powder.
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