Hardcover book shell production process (4)

Fourth, the hardcover book shell warping and prevent

1. The reason for the warpage of hardcover bookcases. When the water content of single sheets, semi-finished products and finished products changes, the natural bending deformation caused by the edges perpendicular to each Other is called warpage. After the coated or coated flat print, the natural bending deformation produced with respect to a centerline is called curl. The warpage of the cover board will inconvenience the manufacture of the hardcover bookcase, and the warpage of the hardcover book case will also bring difficulties to the processing and the upper case of the bookcase, and obviously reduce the stamping quality and the uppercase of the bookcase. The machine automatically supplies the reliability of the book case portion, thereby greatly affecting the appearance quality of the book.

Common hardcover shells are multi-layered composites consisting of cover materials, cardboard, and adhesive materials of different thickness and different physical and mechanical properties. The reason for the warpage of the hardcover bookcase is due to the different nature of the material constituting the bookcase. When the external conditions change, it will cause changes in the internal stress and other factors, resulting in varying degrees of appearance changes; for the same material, different direction of the silkworm, The shrinkage rate is different. In general, the longitudinal shrinkage is high and the transverse shrinkage is small. When the cover material and the cardboard are used improperly and cross-grained at the time of blanking, warpage will occur; the overwhelming majority of the bookcase material is a water-absorbent material, and the thickness and uniformity of the paper, especially the paperboard, are inconsistent, and they absorb moisture and dry. During storage, changes in the water content inside the book shell will cause deformation and warping.

During the manufacture of the book cover, when the cover material and the cardboard layer are bonded, the internal stress of the cover layer is reduced due to absorption of water in the glue layer, so that the book case is kept in an equilibrium state. However, the cover material is not easily permeable to water (such as linoleum). When dried, most of the water can only be distributed along the inner layer of the book shell. Therefore, the cardboard surface of the cardboard is dried and shrunk before the non-brushing surface. The non-rubbing surface of the cardboard is in a state of small internal force due to the effect of water and cannot balance the contraction force of the cover material, the glue layer, and the glue surface. Therefore, the book shell is curved to the surface layer with a large contraction force, which causes the book case to curl upwards.

After the bookshelf and the book block are flattened before the book is completed, warping may also occur. This is because the book shell and the ring liner are also bonded with a water-soluble adhesive, and each layer of the book shell has a different thickness and moisture content, different strengths and shrinkage rates, and thus determines that these materials have different shrinkages. Stress and warpage. Because the book is not easy to contact with the outside world after the book, while there is support at the back of the material, so when the glue layer dry and dehydrated, the water can only distribute along the three sides of the incision or absorbed by the book block. Therefore, the flat bookcase starts to curl after the book is finished, and is most obvious at the two corners of the incision.

2. Prevent bookcases from squeezing.

(1) Drying by hot pressing. The moisture inside the paperboard is evaporated to improve its anti-deformation ability, and at the same time, the surface of the paperboard can be made smooth.

(2) Use high quality cardboard. The tight or loose structure of the cardboard is an important factor in resisting the deformability under the effect of water. Foreign countries have produced high-quality cardboards with dense textures, interweaved with horizontal and vertical threads, so that the cardboards are basically the same in all directions when they are deformed.

(3) Control the moisture content of the adhesive. Paste cover must use adhesive with low water content, the coating is as thin as possible, which can reduce the total amount of moisture that can be contacted by the shell material, which is the key to solving the problem of hair curling.

(4) Controlling warping by selecting the direction of the winding of the shell material. The book shell material has different shrinkage rates in different wire directions. When the book shell material is cut, the longitudinal direction of the book must be maintained in the four directions.

(5) The effect of the linear shrinkage of the cover material of the book case on the warpage of the book case. If the linear shrinkage of the cover material is higher than the linear shrinkage of the cardboard, the degree of warping of the hardcover cover increases under the contraction stress generated in the cover material. Therefore, the requirement for the cover material is that during the drying process, the linear shrinkage of the cover material should be equal to or less than the linear shrinkage of the bookcase cardboard. Covers that are thicker in paper cover than in cover papers are warped. Therefore, cover paper made of thin cardboard should not use thick cover paper.

(6) Flatten the finished product when stacked. The upper surface of the book cover is covered with a heavy weight, and after 24 hours, the flat shape maintained when the finished product is completely dry can be fixed, and then checked and packaged.

In addition, the finished product should be stored in a relatively stable temperature and humidity environment. Overdrying or excessive humidity can cause changes in the appearance of books.

Fifth, hardcover book shell quality requirements

According to the national standards CY/T27-99, the quality of hardcover shells should meet the following requirements.

(1) The size of the middle seam. When the thickness of the cardboard is 1.5-3.0mm, the width of the middle seam is 7-10mm.

(2) Wide in diameter. The diameter of the round-backed shell is the length of the arc of the circle and two widths of the middle seams; the width of the middle of the square-backed shell is the width of the back of the book plus the width of the two slits. The width of the median diameter of the square back ridge should be added to the thickness of two cardboards.

(3) Floating mouth width. Floating mouth width of 2 ~ 4mm.

1. The book shell is made of animal parts or synthetic resin glue with less moisture, fast drying, and strong bonding.

2. The bookcase cardboard and middle diameter cardboard combination is correct and the dimensional error is: length ≤ 1.5mm, width ≤ 2.5mm.

3. The book case should be face-to-face stacked, flattened, and naturally dried after being transported. Drying and drying should not be allowed.

4. Hot stamping, clear pattern, no paste version, flower color, hot foil firmly, good gloss.

5. Press and embossing should be clear.

6. Based on the back center line of the book, the error range of the book backing is as follows:

Book back thickness error range ≤10mm ≤1.0mm
>10,≥20mm ≤2.0mm
>20, ≤30mm ≤2.5mm
>30mm ≤3.0mm
Source: Bison