Quality and paper defects of the hottest printing

Quality and paper defects of printing paper

paper defects that are not included in the technical requirements for paper quality can be called paper defects. Paper defects include some performance defects that cannot be seen or touched and can only be known through experiments or printing, such as embrittlement, through printing, hair loss, powder loss, etc., as well as various defects and defects that can be directly seen or felt on the surface of the paper, such as dust, dirt, etc. Here, the latter is called the appearance paper disease of paper

there are many appearance diseases of paper, including dust, spots, marks, woolen cloth marks, "cloud flowers", seersuckers, wrinkles, folds, dirty spots, turf, transparent spots, warm spots, holes, embossing, scars, pulp pimples, hard blocks, uneven quantification, poor uniformity, etc. Some of these appearance paper diseases are brought in by the paper materials before papermaking, some are caused by poor technical operation or poor technology in the papermaking process, and some are caused by poor environmental sanitation in the factory. Once they appear, some appearance paper diseases are relatively continuous, such as wool marks and "cloud flowers", which will always exist if no measures are taken once they appear; Some appearance paper diseases are accidental or occur only once at a long interval, such as dirty spots, holes, etc. Some paper diseases will deteriorate the quality of paper, such as dust, wool marks, etc; Some paper diseases make the paper waste, such as offset books and periodicals with hard blocks or coated paper with large dirty spots, which can only be treated as waste

according to different types of common paper diseases, they can be divided into:

fluctuation of paper quantity and unevenness of paper web quantity

the first fluctuation is generally caused by the periodic vibration of the flow system of the paper material to the headbox, the shaking of the rotor screen in front of the headbox or the vibration of the pulp pump, and sometimes caused by the bending or unreasonable opening of the homogenizing roller in the headbox. Second, the fluctuation of household decoration use is generally caused by unreasonable production process or improper operation and management

poor uniformity. The phenomena are:

1) lumpy tissue: refers to the state in which fibers are flocculent together and become lumps

2) "cloud flower": also known as cloud like tissue, it refers to that the fibers in the paper are distributed in the paper like clouds

3) fiber tissue disjunction: refers to poor fiber interweaving in the running direction of the paper machine

4) wavy fibrous tissue: refers to the wavy thickened layer with bends along the transverse width of the paper. No range setting requires bending

5) pulp track: refers to some longitudinal strip pulp marks visible against the light on the paper web

dust, spots, sand and hard blocks

1) dust: it can be divided into "fibrous dust", "non-metallic dust" and "metallic dust"

2) spots: can be divided into "wet spots and steam spots", "cylinder spots", "pressure light dark spots", "slurry spots", "bubble spots", "filler spots and paint spots", "bright spots and white spots"

3) sand: refers to hard mineral sand particles such as sediment, lime product residue, carbon residue, etc. on the paper

4) hard block: refers to the block materials or coarse-grained materials with hard texture and higher than the paper surface that occasionally appear on the paper, such as knots, grass knots, pulp blocks, etc., which are the most harmful to printing

holes and through curtains

1) holes: holes that are completely penetrated and have no fibers on the paper. Holes can be divided into pinholes, holes and holes according to their size

2) transparent curtain: refers to the point where the fiber layer on the paper is thin but not completely penetrated, and its transmittance is larger than that of other parts of the paper. The small ones are called light transmission points, and the large ones are called transparent curtains

embossing and various impressions

1) embossing: refers to the phenomenon that the fibrous tissue forming wet paper collapses under excessive pressure during the pressing process, leaving scattered, irregular, transparent cracks and many small pinholes on the paper. This phenomenon of wet paper being crushed by the pressing roller is called embossing. Serious embossing is easy to cause wet paper to break in the crushing department

2) streaks: refers to the streaks that are different from the gloss or color of the paper under the light

3) felt mark: refers to the mark of the warp and weft lines of the papermaking felt on the paper

4) other marks: there are marks, watermark roll marks, vacuum roll marks, etc

folding and wrinkling

1) folding: refers to the folding of paper pages, and the Netherlands covers the packaging materials with "tight hoops" to fold or overlap, forming overlapping lines or creases. It can be divided into dead fold and live fold

2) warping and arching: warping refers to the state that both sides or four corners of the paper are warped and the middle is concave; Arching refers to the state in which the middle or middle part of the paper is arching in a large area and the two sides or four corners are concave

3) bubbling and bubble sand: bubbling refers to the local contraction of the paper page, resulting in protruding bubbles on the paper surface and fine wrinkles on the paper surface around the bubbles; Bubble sand refers to the dense arrangement of small bubble points on the paper

4) various wrinkles: according to different sizes and shapes, they are divided into curly wrinkles, fine oblique wrinkles, curly wrinkles, etc

other paper diseases

1) cracks: refers to cracks or breaks in the middle or edge of the paper

2) the paper edges are not neat and clean: on the one hand, the paper edges cannot be parallel or rectangular after cutting, or the paper edges have burrs, bends and twists; on the other hand, the paper after cutting and sorting is stacked unevenly or the end face after rewinding has the phenomenon of "inside out and outside in". The unclean edge of the paper refers to the burrs, jagged edges, incomplete edges and dirty edges of the paper after cutting

3) inconsistent hue: refers to the inconsistency of whiteness and color of the same batch of products or even the same order of paper

4) "Lotus edge": refers to the bending state in which the edge of the paper, especially the longitudinal edge, loses its due straightness and is not in the same plane as the paper surface

5) obvious difference between two sides: the obvious difference between two sides of the paper can be seen with the naked eye (except for single-sided offset paper and single-sided coated paper)

6) incomplete, broken pieces and paper fragments: incomplete and broken pieces refer to the paper with incomplete pages, including missing corners, edges, rags or only half pieces; Shredded paper refers to small pieces of paper of different sizes mixed in the paper

the appearance quality of paper refers to the quality of paper that can be identified only by human senses without using instruments and equipment. It can be divided into the appearance quality of the paper itself and the appearance quality of pieces of paper formed by sheets of paper or long strips of paper

no matter what kind of appearance quality affects the use of paper to varying degrees. Poor appearance quality will not only reduce the use value and printing yield of paper, but also make paper waste in serious cases. In addition, some serious appearance paper diseases in the paper, such as hard paper blocks, will also damage the printing plate and cots during printing, causing damage to the printing equipment. The appearance quality of paper is also closely related to its physical properties. For example, the smoothness and opacity of paper with obvious seersucker will also be affected

the appearance quality inspection of paper should achieve the following three purposes:

check the finished quality of paper. It mainly includes: whether the shape of the piece of paper is good, whether the size is qualified, packaging quality and damage degree, etc

master the basic paper of paper. Including color, evenness, flexibility and tensile strength, smoothness and cleanliness

spot check to find out the approximate missing rate of lithographic paper (the percentage of paper with obvious paper defects in the total number of papers)