Technical problems and processing in bookbinding books
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From the printing industry's use of EVA hot melt adhesive glue books, the time has been more than a decade. The book has a short cycle, stable quality, low error rate and low labor intensity. Welcomed by the publishing industry and the printing industry. In particular, this year's PUR hot melt adhesive was promoted and used abroad. PUR hot melt adhesive replaced the common EVA hot melt adhesive. The disadvantage of EVA hot melt adhesive was compensated by PUR hot melt adhesive. PUR hot melt adhesive is a perfect one. Binding method. However, in the current printing industry, EVA hot melt adhesives are used in adhesive books, and 80% of the problems in the quality of printed matter are caused by improper use of EVA adhesives. Therefore, this paper analyzes the technical problems in the binding and explores the common solutions.
First, the type and selection of hot melt adhesive
The research of hot melt adhesives in China began in the mid-1970s. In the past five years, the domestic hot melt adhesive industry has entered a mature stage, and the application range of hot melt adhesives is also expanding. Due to the difference in composition of hot melt adhesives and bonding objects, it has expanded from traditional hygiene products, packaging, printing and binding to more than ten industries including clothing, tape, shoes, refrigerators, cables, automobiles, and construction. A variety of hot melt adhesives.
The EVA hot melt adhesive used in books is a solid fusible polymer that does not require solvent or moisture. The hot melt adhesive is solid at normal temperature. When the hot melt adhesive is heated and melted to about 170 ° C, it becomes a liquid with good viscosity. When the temperature in the rubber pot rises above 250 ° C, the hot melt adhesive liquid begins to age. The glue that is discolored, deteriorated, has a reduced viscosity, and the film becomes brittle cannot be used.
At present, the country has not yet issued standards for hot melt adhesives for books and periodicals. The factory producing hot melt adhesives does not have a unified quality control system, and each factory has production standards for each plant. There are many types of hot melt adhesives, and the bonding properties are also different. According to the speed of different perfect binding machines, different objects of binding, opening time, curing time, etc., the adhesive and side glue are selected and selected.
The experience of a printing company in North China to control the hot melt adhesive index system can be used for reference. Their experience in practice: For each brand and batch of newly purchased hot melt adhesives, strict quality inspection is required. Only the glue that is qualified for each indicator can enter the workshop. In this way, the quality of the glued 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 range of -10 to 10 °C. The newly purchased hot melt adhesive is made into a certain strip of rubber, placed on a curved frame of the freezer, and subjected to a bending test at a constant temperature of -1 ° C. After 30 minutes, the unbreakable product is a qualified product. They are working on a hot melt adhesive that can be automatically controlled to withstand low temperature performance to make the results more objective and scientific. 2 anti-fatigue strength indicators. This is an indicator of the number of times the rubber layer is resistant to bending. It ensures that the book will remain intact after repeated readings. First, the hot melt adhesive is made into a rubber strip according to regulations, and then tested on a fatigue strength measuring instrument (self-made) at a predetermined temperature to obtain a number of indexes for bending resistance. 3 specific gravity indicators. After comparative tests, they found that the specific gravity of the rubber with a specific gravity greater than 1 is lower than that of the hot melt adhesive with a specific gravity less than 1. In addition, the higher the specific gravity of the hot melt adhesive, the greater the weight of the single adhesive when the adhesive layer is the same, which will significantly increase the production cost. The specific gravity can be measured in accordance with the relevant adhesive measurement method. In practice, they often use the "water bleaching" method for qualitative determination: the glue with a specific gravity greater than 1 will sink to the bottom of the water, and the rubber with a specific gravity of less than 1 will float on the surface. This method is simple but fast and effective. 4 anti-aging indicators. The use of hot-melt adhesive which is easy to age is obvious in the process of use, which will cause coking and discoloration, which will bring inconvenience to the normal operation of the process. Secondly, in the use of the bookbinding book, quality problems will occur due to the rapid aging of the glue. 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 thermostat the rubber sample at a higher temperature, and the change in the anti-aging property is very obvious.
"Good horse with a good saddle", high-quality products must be backed by high-quality equipment and materials. The problems of plastic bag machine, hot melt adhesive, workshop temperature and humidity are directly related to the quality of the glued products. Therefore, the work before the binding is as follows:
1. The glue shop requires a normal working temperature of 20 ° C - 30 ° C and a humidity of 50% - 70%. When binding the product, preheat the hot melt adhesive 2 hours in advance. For older models of plastic bag machines, there is no other hot pot for the hot melt preheater.
2. Data setting, specification and data review according to different specifications, different papers, book backs, thickness, etc. before binding.
3, the choice of hot melt adhesive: In order to make the hot melt adhesive book pages do not loose pages, drop pages, you must make the book block between the seams must have sufficient tensile (folding) strength, it is necessary to use tensile strength Hot melt adhesive with high temperature, small temperature change, high melt viscosity, high hardness, high tensile strength and elongation at break.
The author believes that 80% of the quality problems in the 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 the process design and process, and be responsible and responsible before the binding. Quality issues are guaranteed.
Second, the technical improvement of the binding machine
1. Processing of the slotting knife: From the actual operation result of a printing company, the top of the original slotting knife (the blade tip) of the plastic bag machine is too narrow, especially the backing glue groove of the 5cm thick book is not ideal, the book The three-fold or four-fold bond and tear resistance of the post have a certain quality effect. The solution is: the top of the slotting knife can be twisted with a grinding wheel, so that the result of the slotting knife slotting is "U" shape, the slotting depth is 1.2mm? 鄄 1.5mm, the slot The distance between the groove and the groove is about 4 mm, and the groove angle is 60°, which is the best, thereby increasing the amount of glue applied to the "U" portion of the groove of the signature and increasing the bonding area in the signature. After flattening the book block, it is guaranteed that the inner page is not easy to fall off or fall off.
2, equipped with pre-melting glue pot: Some plastic-packing machines do not have hot-melt adhesive pre-melting pots, due to improper glue and other reasons, the glue temperature drops, continue to produce will make the rubber easy to crack, cover the shell, the text fell off the page. In order to solve the key problems affecting quality, it is best to prepare a hot-melt glue pot during production. After the hot-melt glue temperature in the glue pot reaches the standard temperature of the package, the hot-melt glue is required according to the production process. Directly pour into the running rubber wheel pot to ensure that the plastic bag machine does not stop in normal production. The power supply of the pre-melting glue pot needs to be equipped with a pressure regulator to control the temperature of the glue to ensure that the glue temperature is stable and not aging. The pre-melting time of the second plastic pot is determined according to the time required for the first plastic pot to be applied, so as not to affect the package progress of the plastic bag machine.
3, the glue pot is equipped with a double thermometer: in order to accurately detect the temperature of the glue pot, in addition to a thermometer originally equipped with the machine, it is best to match a mercury thermometer and a thermometer metal shell, so that the position does not affect the operation of the book holder. standard.
Third, the pre-press spelling large version and the binding of the binding
1. The binding position of the glued booklet should be enlarged by 1mm?鄄2mm than the rated book opening for the glued milling back and slotting to ensure that the milling cutter has sufficient milling back size and groove depth.
2, in the process of binding, in order to prevent the quality of the wrong posts and less posts, so that the second check for wrong posts and fewer posts. There is a simple and feasible method: on the basis of the original ridge-stepped block (identification), and in the sky part of the signature, a step-type post block (identification) is also added, so that the book back is in the milling back. After the cover is slotted, the second pass through the big head is checked to see if there are any quality problems with wrong posts and fewer posts.
3, the book of the book with the mouth of the book, the mouth should be made (opening) before the binding. That is to say, the width of the original book is widened by 1.5mm?鄄3mm, so that the product of the book block after the slotting is finished to meet the standard size of the finished product. In the milling back slot, when the book core mills the 1?郾5mm pull, the incision is increased by 1.5mm. In general, when pulling the mouth, it is necessary to master the drawing according to different paper and folding number. The size of the incision is increased at the time of the edition to ensure the cut size of the book standard.
4. At the same time, when the cover is printed, the white edge of the cover is designed to be increased by about 5mm. The white edge can be used as the “receiving station” of the residual glue, which helps to prevent the leakage of the glue to the outside of the cover during the binding process. First, the leakage of the residual glue can be avoided. Second, the book can be avoided. The glue is dirty.
Fourth, preparation before binding
1. Stacking of signatures after folding: In the preparation work before the bookbinding, whether it is a linear plastic bag machine or a disc package machine and a binding production linkage line, the folding quality of the signature will directly affect the formation of the book. The quality and operation of the whole machine are normal, which affects the play cycle and economic benefits. From the situation of a dozen printing machine plastic bag machines, more than 50% of the failures of the plastic machine's shutdown and neutral operation (including the linkage line equipped with the throwing device) are caused by the non-standard folding and the irregular stacking of the signatures. Caused. In order to ensure the normal operation of the plastic bag machine, the post-folding post processing is the key link in the binding production. The method is as follows: the four-fold page above 180g is to be broken, and after the air in the signature is discharged, the two ends of the signature are made of hardwood (the size of the board is the same size as the signature) and the same length of the signature is used by the baler. Bundles, the level of the signatures must be bundled for more than 2 days. The time for the signature of the urgent items should not be less than 24 hours or the binding must be done before the binding. 2 After the book block used in the plastic bag machine is equipped with a page, it must be bundled-battered-separated to ensure that the back of the book block is flat and the inner page is not scattered or dropped. If the signature is not slag after the book is dispensed, the scattered book is easy to be scattered or some of the stickers, the page milling back and the slotting do not meet the standard, and it is easy to drop pages or loose pages. After the bundle of 3 folds, some of the factory buildings are limited by the development of production. Only the signatures are bundled in the aisle and outdoor. In winter, the books are bundled in the unheated warehouse. When binding, use the car. Ship directly to the glue shop. In winter, due to the large temperature difference between indoor and outdoor, this will seriously affect the quality of the binding. When the glue is in contact with the signature with the temperature difference, the surface of the rubber layer and the side rubber layer are instantly lowered to shorten the hot melt adhesive. The solidification time and opening time, for the above problems to be dealt with and avoided: when the production arrangement is carried out, at least one day in advance in winter, the booklets to be bound must be transported to the same place in the workshop and the workshop, and the bindings for the bindings are made. Aging treatment to minimize the quality problems caused by the temperature difference between the signature and the workshop. 4 dropped pages, scattered pages; the main reason for falling pages and loose pages is related to folding. If the folding out of the set is too large, the page hits the page when the page is not in place. In order to avoid the pages that are dropped or scattered (80g) or more, the air must be broken when the signature is broken. For example, there is a fold or a single page in the signature. Good for sticky page processing, so the problem of falling pages and loose pages (removing the milling cutter) is solved.
2, before the work of the plastic bag machine inspection: 1 domestic plastic bag machine before starting, pay attention to check the milling cutter plate and milling cutter. According to the length of use of the plastic bag production, the sharpness of the milling cutter should be checked regularly, and the milling cutter that can not be milled off by the paper scraps should be replaced regularly; the pallet should be corrected frequently to ensure the consistency of the pallet working surface; The work team will refuel at least twice for each fueling location. 2 At the end of each work class, it is necessary to clean the brushing machine and the slotting knife in time to keep the surface of the guide rail clean. Careful maintenance and inspection of the suction device and the discharge of paper dust are normal or not, ensuring that the paper dust is completely separated from the signature page during the milling and grooving process. Paper scraps cannot be brought into the pot with the movement of the signature pages. Otherwise, check the replacement pallets and milling cutters.
V. Avoidance of common quality problems
1. The round back and the back of the book are round and convex: 1 The reason is that the height of the pallet is not enough, it should be adjusted to the standard gap between the back of the book and the pallet; second, the weight of the cover is increased, and the weight of the cover is increased. The unindented line or the crease line is extra wide. 2 For the cover paper of the ultra-gram weight used in the binding production, the indentation must be indented. The crease should be thicker than the book block or less than the thickness of the book block 0?郾5mm. can.
2, book degumming, loose pages: 1 book core milling back depth is not enough, the signature page is not completely milled into a single page, causing book degumming, loose pages, should increase the milling back depth and improve the folding quality. 2 Slotted, the depth of the groove is not enough to cause the book to be off, loose pages, the depth of the slotting knife should be adjusted, and the sharpness of the slotting knife should be kept. 3 The temperature of the hot melt adhesive is too low, so that the fluidity of the glue is poor. The hot melt adhesive cannot penetrate into the groove opened by the book block, which causes the book to be degummed and scattered. The hot melt adhesive should be heated to 160 ° C ~ 180 ° C. Use it left and right. The best melting point of hot melt adhesives depends on the temperature adjustment of the workshop (the hot melt adhesive requires a workshop temperature of 20 ° C? 鄄 30 ° C). In the winter, especially in the bindering workshops of northern enterprises, there must be heating equipment; The workshop also needs heating equipment to ensure the quality of the plastic bag. 4 book back ridge hot sol sizing caused by book stripping, loose pages, should control the thickness of the backing, generally controlled between 0.6mm ~ 2mm, and adjust the distance between the rubber wheel and the back of the book. 5 improper use of hot melt adhesive models, is also the reason for the book degumming, loose pages, so the choice of using hot melt adhesive should match the model and season of the plastic bag machine. 6 After the milling, the paper wool, paper ash and paper scraps should be cleaned in time to avoid brushing. 7 Coated paper, offset paper mixed bookbinding, the depth of the groove, the glue, etc. should be based on the two papers.
3, the book back is not square: 1 use the unsharp milling back knife milling back resulting in the back of the book is not square, you should replace the sharp milling back knife. 2 The unevenness of the adhesive on the backing causes the back of the book to be unsquare. The glueing mechanism should be adjusted to make the adhesive evenly glued. 3 improper adjustment of the pallet setting mechanism causes the back of the book to be unsquared, and the pallet setting mechanism should be adjusted. 4 The arrangement of the posts is not flat and the book back is not square. It should be arranged to ensure that the posts are flat. 5 The key to the deformation of the spine is that the setting time is too short, the book is falling, and the book is falling, especially thick books are more prone to this problem. (Some hot melt adhesives have a long opening time and will also cause the same symptoms) The solution is to control the speed of the plastic bag machine according to the thickness of the book block in the production; at the same time pay attention to the principle of thick book and fast copy to adjust the speed of the package.
4, the cover is not flat, the cover bar line is obvious: 1 the amount of side glue is too large, resulting in uneven cover, cover bar line is obvious, should control the amount of side glue coating. 2 The side glue glue temperature is too low, causing uneven coating of the side glue, resulting in uneven cover and obvious cover line. The glue temperature of the side glue should be increased. In the paper type of the book block, the glue temperature is generally controlled at 120-160°. C or so.
5, book size is not accurate, etc.: 1 First check the three-sided knife positioning gauge, front knife, side knife, push book trolley (pushing book) size is equal to the size of the cutting open, "thousands" pressure is whether Suitably, the pressure of the two-sided knife should be adjusted to 3 kg to 5 kg. 2 Three-sided knife "Thousands of pounds" pressure is too small when cutting, causing the book to be big and small, the cover back is broken. 3 "Three pounds" of the pressure of the three-sided knife to compact the book, the cover is not wrinkled and no upper and lower knife. 4 If the size of the book is not standard, the left and right ends of the rear gauge should be adjusted to be parallel or the lead wear clearance of the rear gauge. 5 platform machine knife cutting the size of the book when the upper and lower knives and indentation, should adjust the "thousands" pressure, while the "thousands" presser foot with "wooden board", the wooden board does not affect the back and forth movement of the rear gauge Standard, thus avoiding the presser foot indentation left by the platform knife cutting the book.
6. There are many bubbles and empty glue on the back of the book. There are many reasons for this: 1 The hot melt adhesive is damp. When the water content is high, the bubble is most likely to be generated. The hot melt adhesive should be stored in a dry warehouse to avoid moisture. 2 After the milling back is slotted, the back of the book is not flat, and the gap of the adhesive is uneven. Check whether the milling cutter and the slotting knife are sharp. On the contrary, timely replacement and grinding are performed to control the uniformity of the adhesive. 3 The pallet is not parallel with the back of the book, and the glue is also generated, and the pallet mechanism is adjusted.
In the binding process management, when there is no preheating rubber pot production, the amount of glue added to the rubber pot is strictly limited, so that the amount of glue in the glue pot is shortened as much as possible to avoid hot melt adhesive. Aging. In practice, it is proved that the temperature of the glue used in the winter of the book core is generally higher than other seasons by about 10 ° C, and the temperature of the glue is controlled between 180 ° C and 185 ° C, so that the viscosity of the glue is lower than 4000 mPa·s. In order to maintain good wetting properties of the glue on the pages. In the normal use temperature of 170 ° C ~ 220 ° C in the normal use of hot melt adhesive, the higher temperature is strictly controlled, not only to maintain the wettability, but also to greatly reduce or even eliminate the drawing phenomenon of the rubber coating. The processing time of each process failure caused by the rubber entanglement is reduced or avoided, which is beneficial to improve the production efficiency of the whole machine.
In short, as long as we continue to explore and summarize from practice, carefully understand and master the performance of materials, process parameters, and strict process operations in production, it is able to obtain the binding products that meet the quality standards.