In book binding, wireless glue binding accounts for about 60% of the total annual production volume of 8 billion books. Its advantages are obvious, the cycle is short, the production process is simple, can be linked, can be stand-alone, especially the introduction and application of wireless glue binding production line, but also promoted the development of wireless glue binding technology. However, due to various reasons, there are many quality problems in wireless glue books, such as easy page drop. This problem not only confuses the manufacturers but also brings inconvenience to readers. In particular, the problem of more pages dropped in textbooks in primary and secondary schools has caused the attention of relevant leaders. As a result, publishers and printers face an unprecedented crisis in quality and credibility.
There are a number of factors that cause wireless glue to close pages. If several important aspects of the production process are not properly handled or are not standardized, they can cause pages to fall. However, as long as the cause of the page drop is found and an effective solution is taken, the quality of wireless glue can be guaranteed. Based on years of work experience and practice, the author believes that it can be controlled from several important processes in the binding process, which can effectively avoid the occurrence of page faults.
Milling back slot
Milling back draw groove is a very important link in the production process of adhesive bonding. It uses high-speed rotation of the flat cutter to mill the entire book into single pages, and pulls the slot on the back of the book through the end mill (slotting knife). Whether the back of the book has a strong ability to glue, the key is the depth of the groove, and the height of the end mill is the most difficult element to grasp. If the adjustment of the end milling cutter is too low, the depth of the groove is not enough; if the adjustment is too high, it may easily collide with the book holder and destroy the knife, as shown in FIG. 1 . In particular, the use of a disk type bookbinder can cause instability in the large disk after a few years of use, making it more likely to destroy the knife. Therefore, the following points should be noted in the milling and back-drawing step.
(1) Adjust the distance between the end mill and the book holder. First fix the height of the milling cutter, then use a feeler gauge to determine the distance between each end mill and the book holder, and keep it at 0.3mm, and after every determination of the height of the end mill cutter, it must be with all book holders The distance is measured. If the depth of the groove is not enough, the height of the milling cutter can be properly reduced to increase the position of the end mill to ensure that the depth of the groove is appropriate.
(2) The milling cutter should be inspected regularly during the work, and according to the specifications and requirements of the bound books and magazines, the corresponding cutters should be replaced in time.
(3) According to the degree of wear of the milling cutter, it is determined whether the milling cutter is replaced by a single handle, partially replaced, or completely replaced.
(4) The gauge must be installed when the tool is changed, so that the same set of milling cutters can be kept at the same radius to avoid damage to the blade, and its height error should be controlled within 0.1mm.
Coating adhesive
Wireless adhesive tape is mainly made of hot melt adhesive material. The hot melt adhesive has the characteristics of high melting point, fast curing, strong adhesion, etc., and the adhesive layer has a certain degree of flexibility and hardness, and is easy to use. In the back gluing process, the improper operation method and uneven glue application are the main reasons for the loss of pages.
1. Control glue thickness
Too thin a layer of glue will undoubtedly affect the degree of adhesion of the books and magazines; an overly thick layer of glue will increase production costs. Therefore, under the premise of not affecting the book binding quality, according to the thickness of the book and the type of paper, reasonably control the thickness of the glue layer.
After milling the back-drawing book block into the gluing process, the first rubber roller encountered is located 1.5mm below the back of the book. The roller has a large diameter (120mm), high position, and the surface is generally 1.5 to 2mm thick. The thickness of the adhesive layer can be controlled by the baffle on the rubber roller. Its function is to brush a little glue on the back of the book, and make part of the glue infiltrate into the back pull groove of the book. The role of the second rubber roller is to apply evenly the glue on the book block, which has a small diameter (117mm) and is located 2mm below the back of the book.
In the gluing process, the thickness of the back adhesive layer of the book is actually controlled by a roller that is reversed from the outside of the glue pan. If the adhesive layer is thinner, the height of the rubber roller can be reduced to compensate; if the adhesive layer is thick, the height of the rubber roller can be increased and the adhesive layer can be thinned. As long as its height is adjusted to the proper position, the desired adhesive layer thickness can be maintained. The inverting squeegee roller is generally located at 1 to 1.5 mm under the back of the book, which ensures that the glue layer after the book is dried is about 1 mm. Second, it has another function, which is to use the principle of reverse rotation to break the glue and keep the machine clean.
2. Control glue temperature
The hot melt adhesive used for wireless adhesive bonding is a high speed hot melt adhesive, and the temperature of the adhesive is generally controlled at about 160°C. Moreover, the hot melt adhesive can produce the strongest adhesive force only at an appropriate working temperature, that is, only applying the glue on the back of the book at the optimum temperature can firmly bond the back of the book and the cover. Therefore, the accurate control of the temperature of the plastic pot is the key to the best adhesion of the hot melt adhesive.
The temperature of the glue pan should not be too high or too low. If the temperature is too high, the glue will be aged and become thin, and the color will darken. The adhesive glue applied to the back of the book cannot be hanged, so that the book back does not reach the required amount of glue, causing the pages of the book to fall; the temperature is too low, and the glue thickens. Hardening, the back of the book is easily broken, and page breaks are also likely to occur.
In actual production, the hot melt temperature can be controlled from the following aspects.
(1) The glue temperature does not reach the target temperature and should not be turned on.
(2) If the temperature of the glue liquid is much higher than the target temperature, the temperature of the glue pan should be lowered in time or put in a little plastic block for stirring until it reaches the target temperature before it can be turned on.
(3) If the color of the glue liquid in the pot changes from pale yellow to dark brown, it indicates that the glue liquid is aging and can no longer be used. Otherwise, the dried brittle gel will seriously affect the quality of books and periodicals. Therefore, the glue in the plastic pot must be completely removed and replaced with new rubber.
(4) The hot melt must be preheated before use, and the temperature of the preheated glue pan must be the same as the temperature of the working glue pan.
3. Regularly clean the glue pot
Regular cleaning of plastic pots is an indispensable step in the adhesive bonding process, because any type of glue will produce some deposits on the bottom of the pot during use, which will affect the heating speed of the pot. If it is not cleaned up in time, part of the precipitate will cake, blocking between the rubber roller and the baffle, causing the glue to flow. In severe cases, there will be broken glue on the rubber roller, which will directly affect the thickness and evenness of the glue on the back of the book, resulting in sometimes gum and sometimes no glue on the back of the book. If this phenomenon cannot be detected in time, it will cause a page-failure failure, and a large number of finished books will be repaired. Visible, regular cleaning plastic pot is very important.
Generally, the cleaning cycle of the plastic pot can be determined by the output size of the visual equipment or the production interval, which can not only keep the plastic pot clean, but also guarantee the bookbinding quality and production cycle.
Timely repair of pages and periodicals
The use of hot-melt adhesives to produce adhesive repair books can be repaired, any quality problems found in the quality of the adhesive can be used to re-adhesive hot melt adhesive repair.
Especially in cutting, due to certain pressure, the quality of books and magazines is easily exposed. Therefore, when cutting a book with a three-sided knife, it is necessary to carefully observe, find problems in a timely manner, accurately determine the cause of the problem, and promptly remediate the books and periodicals to eliminate the quality of books and magazines from the factory. E.g:
(1) The back of the book may be due to the fact that the cover is double or the cover and back of the book are not firmly bonded.
(2) The back of the book is soft, which may be caused by insufficient thickness of the adhesive layer or broken glue.
(3) There are many folds in the back of the book, which may be because the thickness of the glue layer is not enough or the clamping strength of the hold is not enough.
(4) From the days and feet of books and magazines, it is also possible to find out about empty pages and missed books.
It should be noted that the repaired books and magazines must not be as beautiful as the ones that were formed on the machine. Therefore, they cannot be relied on to repair and ignore the quality control in the production process.
Although there are many reasons that affect wireless adhesive bookbinding, but as long as the strict quality control and standardized operation in all production processes, it can completely solve the issue of wireless glue binding book pages. Moreover, with the rapid development of China's printing technology and the continuous improvement of the requirements for finishing after printing, when studying the practical problems arising from the production process, we should continue to learn new processes and knowledge.