Technical problems and treatment in bound book

Judging from the use of EVA hot-melt adhesives in the printing industry, it has a history of more than ten years. The cycle of the bound book is short, the quality is stable, the error rate is low, and the labor intensity is light. Welcomed by the publishing industry and the printing industry. Especially this year, the promotion and use of PUR hot-melt adhesives in foreign countries. The emergence of PUR hot-melt adhesives instead of the commonly used EVA hot-melt adhesives makes the disadvantages of EVA hot-melt adhesives compensated by PUR hot-melt adhesives. Binding method. However, in the current printing industry, EVA hot-melt adhesives are used in book binding, and 80% of the quality problems of printed products are caused by improper use of EVA adhesives. Therefore, this article analyzes the technical problems in bookbinding and explores common solutions.

1. The type and selection of hot melt adhesive

The research on hot melt adhesives in China started in the mid-1970s. In the past five years, the domestic hot melt adhesive industry has entered a mature period, and the application range of hot melt adhesives is also expanding. Due to the different components of hot melt adhesives and the difference between the bonding objects, it has expanded from traditional sanitary products, packaging, printing and binding fields to nearly 30 industries such as clothing, tape, shoemaking, refrigerators, cables, automobiles, and construction. Varieties of hot melt adhesives.

The EVA hot melt adhesive used in books and periodicals is a solid meltable polymer that requires no solvent and no moisture. Hot melt adhesives are solid at room temperature. When the hot melt adhesive is heated to about 170 ° C, it becomes a liquid with good viscosity; when the temperature in the glue pot rises above 250 ° C, the hot melt adhesive liquid begins to age Glue that discolors, deteriorates, has reduced viscosity, and the film becomes brittle cannot be used.

At present, the country has not promulgated standards for hot melt adhesives for books and periodicals. The factories producing hot melt adhesives do not have a uniformly controlled quality index system, and each factory has its own production standards. There are many types of hot melt adhesives, and the bonding performance is also different. According to the speed of different glue binding machines, different objects of glue binding, opening time, curing time, etc. to distinguish and choose to use adhesive and side glue.

The experience of a hot-melt adhesive index system used by a printing company in North China can be used for reference. Their experience summarized in practice: each brand and batch of newly purchased hot melt adhesive must undergo strict quality inspection, and only adhesives that pass each index can enter the workshop. In this way, the quality of the bound product is ensured. The quality indicators they control mainly include the following: ① Low temperature resistance index. They designed a temperature-controlled freezer with a temperature control error of +/- 1 ° C and a temperature measurement range of -10-10 ° C. The newly purchased hot-melt adhesive is made into a certain adhesive strip, placed in the bending rack of the freezer, and the bending experiment is carried out at a constant temperature of -1 ° C. After 30 minutes, the one that does not break is a qualified product. They are working on the design of an automatically controlled hot-melt adhesive tester with low temperature resistance to make the measurement results more objective and scientific. ②Fatigue strength index. This is an indicator for detecting the number of times the adhesive layer is resistant to bending, and it can ensure that the book will remain intact even after repeated reading. First, the hot-melt adhesive is made into a rubber strip according to the regulations, and then tested on a fatigue strength tester (self-made) at the specified temperature to obtain the index of bending resistance. ③ Specific gravity index. They have found through comparison experiments that the adhesive with a specific gravity greater than 1 has a lower comprehensive performance index than the hot-melt adhesive with a specific gravity less than 1. In addition, the greater the specific gravity of the hot-melt adhesive, the greater the weight of the single-use adhesive when the adhesive layer is the same, which will significantly increase the production cost. The specific gravity can be determined according to the relevant adhesive measurement method. In practice, they often use the "water float" method for qualitative determination: glue with a specific gravity greater than 1 will sink into the bottom of the water, and glue with a specific gravity less than 1 will float on the surface of the water. Although this method is simple, it is fast and effective. ④Anti-aging index. The use of hot-melt adhesives that are easy to age. First, it will obviously cause coking and discoloration during the use of the process, which will cause inconvenience to the normal operation of the process. Affect the life of books. This indicator can be determined according to the national standard, but it takes a long time. The simpler method is to treat the glue sample at a constant temperature at a higher temperature, and the change of the glue with poor anti-aging properties is very obvious.

"Good horse with good saddle", high-quality products must be backed by high-quality equipment and materials. The problems of plastic bagging machine, hot melt adhesive, workshop temperature, humidity and other issues are directly related to the quality of the glue binding products, so the work preparation before glue binding is as follows:

1. The normal working temperature of the glue binding workshop is 20 ° C-30 ° C, and the humidity is 50% -70%; when binding products, preheat the hot melt adhesive 2 hours in advance. For older models of plastic bagging machines, those without a hot-melt adhesive preheating device must be equipped with another glue pot.

2. Before binding, perform data setting, specification and data review according to different specifications, different papers, book spine, thickness, etc.

3. Selection of hot-melt adhesive: To make the pages of the booklet bound by hot-melt adhesive not scattered or dropped, the tensile strength of the book block must have sufficient tensile (folding) strength. Hot melt adhesive with high temperature change, small temperature change, high melt viscosity, large hardness, large tensile strength and breaking elongation.

The author believes that 80% of the quality problems of perfect binding in production are caused by human factors such as improper operation and weak sense of responsibility. The operator should be familiar with the construction requirements of product process design and process before binding, and take a serious and responsible attitude , Quality problems are guaranteed.

Second, the technical improvement of the perfect binding machine

1. The treatment of the slotting knife: Judging from the actual operation results of a printing company, the top (blade tip) of the original slotting knife of the plastic bag machine is too narrow, especially for the 5cm thick books. The depth of the back slot is not ideal. The three-fold or four-fold adhesion and tear resistance of the post have a certain quality effect. The solution is: the top ∧ of the slotting knife can be cut into ∩ with a grinding wheel, so that the result of slotting the slotting knife is a "U" shape, the depth of the slot is 1.2mm? Juan 1.5mm, the slot The distance from the slot is about 4mm, and the slotting angle is 60 °, which increases the amount of glue applied to the "U" part in the slot of the signature and increases the bonding area in the signature. After flattening the book block, it is ensured that the inner pages are not easy to fall off and fall.

2. Equipped with pre-melted glue pot: Some glue packers have no hot-melt glue pre-melted pot. Due to improper addition of glue, etc., the temperature of the glue drops. Continued production will cause the glue to be brittle, the cover uncovered, and the text off page. In order to solve the key problems that affect the quality, it is best to prepare another hot melt glue pot during production. After the temperature of the hot melt glue in the glue pot reaches the standard temperature of the package, according to the needs of the production process, the hot melt glue Pour directly into the running rubber wheel pot to ensure the normal production of the plastic bag machine without downtime. The power supply of the pre-melted glue pot needs to be equipped with a voltage regulator to control the glue temperature to ensure that the glue temperature is stable and does not age. The pre-melting time of the second glue pot depends on the time needed for adding glue to the first glue pot, as long as it does not affect the progress of the package machine.

3. The plastic pot is equipped with dual thermometers: In order to accurately detect the temperature of the plastic pot, in addition to the original thermometer of the machine, it is best to equip a mercury thermometer and a thermometer metal shell, the position of the thermometer is not to affect the operation of the book holder standard.

3. Coordination of pre-press layout and binding

1. The stitching of the bound book signature is 1mm larger than that of the rated stitching. It is 2mm for the binding and milling back and slotting, to ensure that the milling cutter has sufficient milling back size and slotting depth.

2. In the process of perfect binding, in order to prevent the quality problems of wrong posts and fewer posts, it is necessary to check the wrong posts and fewer posts twice. There is a simple and feasible way: it is based on the original spine stepped signature block (knowledge), and also added a stepped signature block (knowledge) at the top of the signature, so that the back of the book is milled After slotting on the cover, solve the quality problem of checking whether there are wrong posts and fewer posts for the second time.

3. The processed book with a beaded book block must be treated as a pull (opening) before binding. That is, on the basis of the original size, the width is uniformly widened by 1.5mm? Juan 3mm. In this way, the book block is completely guaranteed that the product after the milling back is slotted into the book meets the standard size of the finished product. When the book block is milled with a 1 mm and 5 mm opening in the back slot, the incision will increase by 1.5 mm. In short, when opening the opening, it is necessary to master the principle of determining the opening according to the different paper and the number of folds. The size of the incision size added during the edition to ensure the standard cutting size of the book.

4. At the same time, when the large-scale cover is being built, the white part of the foot part of the cover should be enlarged by about 5mm. The white border can be used as a "containment station" for residual glue, which helps prevent the residual glue from leaking out of the cover during the binding process. First, it can prevent the residual glue from leaking onto the stereotyped clip; second, it can avoid the book being quilted. I glued dirty.

4. Preparation before binding

1. Stacked signatures after folding: In the preparation work before binding of books and periodicals, regardless of whether it is a linear binding machine or a disc wrapping machine and a binding production line, the folding quality of the signature will directly affect the book forming The quality and operation of the whole machine are normal or not, which affects the publishing cycle and the economic benefits. Judging from the situation of plastic printing machines in more than a dozen printing factories, more than 50% of the breakdowns and downtimes of the plastic printing machine (including the linkage line equipped with a throwing device) are caused by non-standard folding and non-standard stacking of signatures Caused. In order to ensure the normal operation of the plastic bag machine, the processing of folded signatures is the key link in the production of perfect binding. The method is as follows: â‘ The four-folded pages above 80g should be broken, and after the air in the signature is exhausted, the two ends of the signature are hardboard (the size of the plank is the same size as the signature) and the baler is used to make the signature of equal length. For bundling, the level of the signatures needs to be bundled for more than 2 days. The time for bundling and stacking the urgent signatures must not be less than 24 hours or must be flattened after binding. â‘¡After the book blocks used in the plastic packing machine are matched with pages, they must be bundled-paste-divided to ensure that the back of the book block is flat and the inner pages are not scattered or dropped. If the book signatures are not squeezed after the book is distributed, loose copies are easy to be scattered or some stickers, page milling and slotting do not meet the standards, it is easy to drop or loose pages. â‘¢After bundling the folded signatures, some enterprises' factory area is limited by production development. Only the signatures are bundled in the aisle and outdoor. In winter, they are bundled in a warehouse without heating. When binding, use a car Ship directly to the glue binding workshop for glue application. Due to the large temperature difference between indoor and outdoor in winter, this will seriously affect the quality of the glue binding. During the glue binding, after the glue liquid contacts the signature with a temperature difference, the surface of the spine adhesive layer and the side adhesive layer will drop instantly to shorten the hot melt adhesive. The curing time and opening time of the above problems are solved and avoided by the following methods: during production arrangements, the booklets that need to be bound are shipped to the workshop at the same temperature as the workshop at least one day in advance in winter. Aging treatment, as far as possible to reduce the quality problems caused by the temperature difference between the signature and the workshop. â‘£ Pages and loose pages; the main reason for pages and loose pages is related to folding. If the folding cover is too large and the pages are not hit in place when the pages are interleaved, in order to avoid falling or loose pages (80g) or more, the four-folded signature must be vented to exhaust air. Good for sticking pages, so that the problem of page breaks and loose pages (excluding the cause of the milling cutter) is solved.

2. Inspection before working of the plastic bag machine: â‘  Before starting the domestic plastic bag machine, pay attention to check the milling board and the milling cutter. According to the length of time used in the production of plastic bags, the sharpness of the milling cutters should be regularly checked, and the milling cutters that cannot be milled with paper scraps should be regularly replaced; The work team should refuel each refueling location at least twice. â‘¡At the end of each work shift, the brush cleaner and slotting knife should be cleaned up in time to keep the guide rail surface clean. Careful maintenance and inspection of the suction device and whether the discharge of paper scraps are normal or not, to ensure that the paper scraps are completely separated from the signature pages during milling and slotting. Paper scraps can not be brought into the glue pot with the movement of the signature page, otherwise, check and replace the pallet and milling cutter.

5. Avoidance of common quality problems

1. The unevenness of the round back and the back of the book is round and convex: ① The reason is that the height of the pallet is not enough, and it should be adjusted to the standard gap between the back of the book and the pallet; second, the cover weight is increased, and the cover weight is increased. The unindented line or the crease line is super wide. ②The cover paper used for the over-gram weight used in the binding production must be indented. The indentation crease should be the same thickness as the book block or less than the book block thickness of 0? 郾 5mm can.

2. Degumming and loose pages of books: ① The depth of the book core is not enough for milling and the pages of the signatures are not completely milled into a single page, which causes degumming and loose pages of the book. The depth of the milling and the quality of folding should be increased. ② Slotting, the slotting depth is not enough to cause the book to loose and loose pages, the depth between the slotting knives should be adjusted, and the sharpness of the slotting knives should be kept. ③ The temperature of the hot melt adhesive is too low, so that the fluidity of the glue is poor, and the hot melt adhesive cannot penetrate into the groove of the book block, which causes the book to degumme and loose pages. The hot melt adhesive should be heated to 160 ° C ~ 180 ° C Use it around. The best melting point of hot-melt adhesives is adjusted according to the workshop temperature (hot-melt adhesives require a workshop temperature of 20 ° C? Juan 30 ° C). In winter, heating equipment is especially required in the northbound enterprise's glue binding workshop; southern glue binding The workshop also needs heating equipment to ensure the quality of plastic bags. ④The thickness of the hot sol on the back of the book is too thin to cause degumming and loose pages. The thickness of the back should be controlled, generally between 0.6mm and 2mm, and the distance between the glue wheel and the back of the book should be adjusted. ⑤ The improper use of hot melt adhesive model is also the cause of degumming and loose pages of books. Therefore, the choice of hot melt adhesive should match the model and season of the plastic bag machine. ⑥ Paper wool, paper dust and paper scraps should be cleaned in time after slot milling to avoid brushing. ⑦ For book blocks mixed with art paper and offset paper, the depth of slotting and gluing should be based on the two papers sticking together firmly.

3. The back ridge of the book is not square: ① The back of the book is not square when the back is milled with an unsharp milling knife. The sharp milling knife should be replaced. ②The uneven glue application causes the back of the book to be square. The glue application mechanism should be adjusted to make the glue application even. ③ Improper adjustment of the pallet setting mechanism will cause the back of the book to be square, and the pallet setting mechanism should be adjusted. ④The uneven arrangement of the signatures causes the back of the book to be square, and it should be arranged to ensure that the signatures are flat. ⑤ The key to the deformation of the spine is caused by the short setting time, the rapid fall of the book, and the heavy fall, especially thick books are more prone to this problem, (some hot melt adhesives open for a long time, and the same symptom problems), The solution is: the speed of the plastic packaging machine should be controlled according to the size of the book block in production; and at the same time, pay attention to the principle of thick books and fast cost-reduction.

4. The cover is uneven and the cover bar lines are obvious: ① The amount of side glue is too large, resulting in uneven cover and obvious cover bar lines. The amount of side glue coating should be controlled. ②The temperature of the side glue is too low, which causes uneven coating of the side glue, resulting in uneven cover and obvious cover lines. The temperature of the side glue should be increased. According to the paper type of the book block, the temperature of the glue is generally controlled at 120 ~ 160 ° Around C.

5. The size of book cutting is not accurate, etc .: ① First check whether the size of the positioning gauge of the three-sided knife, the front knife, the side knife, and the book pusher (book pusher) are equal to the size of the cut open book. Appropriate, the "kilogram" pressure of the two-sided knife should be adjusted to 3 kg-5 kg. ② When the pressure of the "thousand catties" of the three-sided knife is too small, the book will be large and small, and the back of the cover will be broken. ③ The pressure of the "thousand catties" of the three-sided knife is based on the compaction of the book, the cover is not wrinkled, and there is no upper and lower knife. ④If the book size of the platform machine knife is not standard, the size of the left and right ends of the rear gauge should be adjusted to be parallel or the screw wear clearance of the rear gauge should be repaired. ⑤When the size of the book is cut by the platform machine knife, when the upper and lower knives and indentation appear, the pressure of "Jianjin" should be adjusted. At the same time, the "Jianjin" presser foot should be equipped with "wooden cover plate". Standard, thus avoiding the presser foot impression left by the platform machine knife cutting books and periodicals.

6. Bubbles and empty glue appear on the spine of the bound book. There are many reasons for it: â‘  Hot melt glue is damp. When the water content is high, bubbles are most likely to be generated. Hot melt glue should be stored in a dry warehouse to avoid moisture. â‘¡The back of the book is uneven after milling and slotting, resulting in gaps in the glue on the backing. Check whether the milling cutter and the slotting knife are sharp. Otherwise, replace and grind in time to control the uniformity of the backing. â‘¢ Empty glue may occur when the pallet is not parallel to the back of the book, adjust the pallet mechanism.

In the glue binding process management, when there is no preheated glue pot production, strictly limit the amount of glue added to the glue pot at one time, so as to reduce the amount of work, and make the time of glue in the glue pot as short as possible to avoid hot melt glue Aging. It has been proved in practice that the temperature of the glue used in the book block in winter is generally increased by about 10 ° C compared with other seasons, and the glue temperature is controlled between 180 ° C and 185 ° C, so that the viscosity of the glue is lower than 4000mPa · s. In order to maintain the good wetting performance of the glue on the book pages. In the normal use of hot-melt adhesives, the aging critical temperature of 170 ° C ~ 220 ° C, strictly control the higher temperature, this is not only to maintain good wettability, but also to make the glue drawing phenomenon greatly reduced or even disappeared. Reduce or avoid the processing time of each process failure caused by rubber winding, which is conducive to improving the production efficiency of the whole machine.

In short, as long as we continually explore and summarize from practice, carefully understand and master the performance and process parameters of materials, and strictly process operations in production, we can obtain bound products that meet quality standards.

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