Five methods for checking the appearance quality of paper sheets
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The appearance quality of a paper sheet refers to the quality of a sheet of paper or a certain area of the paper tape that can be felt by the human touch.
The method of checking the appearance quality of the web paper is generally to cut 10 layers of the outer circumference of the reel, remove the outermost 5 layers, and use 5 layers as the pattern to check the quality of the web (the batch should generally take 2-3) Pieces). The quality inspection of the appearance of flat paper is relatively easy. Generally, several pieces of paper are opened according to the standard sampling method from all the papers of the same batch, and then two orders are taken from each piece to check the appearance quality page by page. Through inspection, the main advantages and disadvantages of the appearance of the paper are clarified, and the missing rate of the paper and the existing paper disease are detected. There are five specific inspection methods:
First, reflective light level inspection Check the paper on the inspection table or on the tabletop. Observe the color, whiteness, flatness and smoothness of the paper by the naked eye from the paper surface 30cm away. Pay attention to the paper for dust, spots, holes, holes, pleats, wrinkles, breaks, cracks, chamfers, dirty spots, seersucker, pulp and other hard blocks. When observing, the gaze is looking at the paper surface, usually under ordinary indoor light, and should not be carried out with strong light or direct sunlight. If necessary, it can also be observed with a general magnifying glass.
Second, the illuminating fluoroscopy checks the paper against the light source (or placed on the glass with the reflector), let the light through the paper, and observe the quality of the paper with the naked eye. Check the uniformity and opacity of the paper fiber structure and check the quality of the paper. Check the uniformity and opacity of the paper fiber structure, and check whether the paper has “cloud flower”, transparent spots, dirty spots, holes and uneven streaks.
Third, oblique inspection Some paper defects, such as glossy or matt streaks on paper, felt marks, roller marks, etc., are not easy to find with a flat inspection method, you must see it with a diagonal inspection. The oblique inspection is to raise or lower the side of the paper with both hands, and look at the paper from different angles to find defects or defects in the appearance quality of the paper. If some paper is improperly produced due to the vacuum of the vacuum roller or the pressure on the roller, the holes arranged regularly on the roller will be reverse printed on the paper. The shadow marks of such holes are not obvious enough, and both the head-up inspection and the fluoroscopy are not easy to find, and can only be found when the oblique inspection is performed. Another example is to check whether the paper surface is fluffed. Generally, the paper surface is rubbed by hand, then one side of the paper is raised, and the eyes are close to the light. If the paper is raised, it can be seen that many fine fibers are erected on the paper surface.
Fourth, hand touch inspection Hand touch inspection is reflected by the sensory contact feeling. Hand touch inspection can find problems with different thickness of paper. Experienced can also grasp the degree of paper high and low by hand. The hand touch test can also determine whether the paper has grass ribs, fiber bundles and fine sand particles sandwiched inside the paper sheet, thereby discovering the hidden paper disease. Some of the small pulp on the paper and the small white sand on the paper, because the color is the same as the paper surface, it is not easy to find by the naked eye, but it can be felt by hand. In addition, by gently rubbing or shaking the paper with your hand, and then observing whether the paper after smashing or shaking has cracks, it is possible to preliminarily determine whether the paper is brittle.
Fifth, hearing test Hearing is to shake the paper by hand or rub the paper, and use the ear to hear the sound it makes to judge some properties of the paper. The toughness of paper is often referred to as the "bone" of paper. When the paper with good body bone is used to hold the paper up and down with both hands, the sound is relatively crisp, and the sound of the paper with poor body bone is weak. The stronger the "body" is, the louder the paper is, and it is not easy to break under tension. Paper made from different raw materials has different sounds. Generally, wood pulp paper is crisper, straw paper is more turbid, and cotton pulp paper is softer. The paper produced by the same pulping method with different pulping methods also has different sounds. Generally, the paper made by the kraft pulp made by the kraft pulp is louder.