The solution to the problem of wireless adhesive bookbinding
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In bookbinding, the wireless adhesive binding method accounts for about 60% of the total annual production of books and magazines of 8 billion. 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 the wireless adhesive binding production line, which promotes the development of wireless adhesive bonding technology. However, due to various reasons, there are many quality problems in the wireless adhesive book, such as easy page drop. This problem not only plagues the manufacturers, but also brings a lot of inconvenience to the readers. In particular, the problem of more page-outs in the textbooks of primary and secondary schools has attracted the attention of relevant leaders. As a result, publishers and printing companies face an unprecedented quality and credibility crisis.
There are many factors that cause the wireless adhesive book to drop pages. If several important links are improperly operated or not standardized during the production process, it will cause the pages to be dropped. But as long as you find the reason for the page drop and take effective solutions, you can guarantee the quality of the wireless adhesive book. Based on years of work experience and practice, the author believes that it can be controlled from several important processes of binding, which can effectively avoid the occurrence of page faults.
Milling back slot
Milling back groove is a very important part of the wireless adhesive binding production process. It uses a flat milling cutter to rotate at a high speed, and the entire book is milled into a single book page, and the end of the book is grooved by an end mill (grooving 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 to grasp. If the end mill is adjusted low, the groove depth is not enough; the adjustment is too high, and it is easy to collide with the book holder to destroy the knife, as shown in Figure 1. In particular, the disc-type binding machine will have a large disk instability after a few years of use, and it is easier to destroy the knife. Therefore, the following points should be noted in the milling back slot.
(1) Adjust the distance between the end mill and the book holder. First fix the height of the flat milling cutter, then use the feeler gauge to determine the distance between each end mill and the book holder, and keep it at 0.3mm, and after determining the height of an end mill, it must be with all the book holders. The distance between them is measured. If the depth of the groove is not enough, the height of the flat cutter can be appropriately reduced to improve the position of the end mill and ensure the proper groove depth.
(2) Regularly check the milling cutter during work, and replace the matching tool according to the specifications and requirements of the bound book.
(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) When changing the tool, the gauge should be installed so that the same set of flat milling cutters can be kept at the same radius to avoid the blade damage, and the height error should be controlled within 0.1mm.
Glue
The wireless adhesive is made of hot melt adhesive as the main bonding material. Hot melt adhesive has the characteristics of high melting point, fast curing, strong adhesion, etc., and the rubber layer has certain flexibility and hardness, and is convenient to use. In the back-coating process, the improper operation method and uneven coating are the main reasons for the publication of pages.
1. Control the thickness of the adhesive layer
If the adhesive layer is too thin, it will undoubtedly affect the degree of bonding of the book; if the adhesive layer is too thick, it will increase the production cost. Therefore, under the premise of not affecting the quality of book binding, the thickness of the glue layer should be reasonably controlled according to the thickness of the book and the type of paper.
After the back-slotted book core enters the gluing process, the first rubber roller encountered is located 1.5mm below the back of the book. The rubber roller has a large diameter (120mm), a high position, and the surface is generally 1.5 to 2mm thick. The thickness of the glue layer can be controlled by the baffle on the rubber roller. Its function is to apply a little glue on the back of the book, and let some of the glue penetrate into the back groove of the book. The role of the second rubber roller is to spread the glue on the book block, which has a small diameter (117 mm) and is located 2 mm below the back of the book.
In the rubber coating process, the thickness of the backing layer of the book is actually controlled by the rubber roller which is reversed outside the rubber pot. If the rubber layer is thin, the height of the rubber roller can be reduced to compensate; if the rubber layer is thick, the height of the rubber roller can be increased, and the rubber layer can be thinned. As long as the height is adjusted to the proper position, the desired thickness of the glue layer can be maintained. The inverted rubber roller is generally located 1 to 1.5 mm below the back of the book, which can ensure that the glue layer after drying is about 1 mm. Secondly, it has another function, which is to use the principle of reverse rotation to break the glue and keep the machine clean.
2. Control the temperature of the gel pot
The hot melt adhesive used in wireless adhesive bonding is a high-speed hot melt adhesive. The temperature of the adhesive is generally controlled at about 160 °C. Moreover, the hot melt adhesive can only produce the strongest adhesive force at the proper working temperature, that is, only the adhesive is applied to the back of the book at the optimum temperature, so that the back of the book and the cover are firmly bonded. Therefore, accurate control of the temperature of the glue pot is the key to achieving the best adhesion of the hot melt adhesive.
The temperature of the glue pot should not be too high or too low. If the temperature is too high, the glue will age and become thinner and the color will become darker. The glue applied to the back of the book will not hang, so that the back of the book will not reach the required amount of glue, causing the book to fall off the page; if the temperature is too low, the glue will thicken. Hardened, the back of the book is easy to break, and it is easy to fall off the page.
In actual production, the hot melt temperature can be controlled from the following aspects.
(1) The temperature of the glue does not reach the target temperature and should not be turned on.
(2) If the temperature of the glue is higher than the target temperature, the temperature of the glue pot should be lowered in time or a small piece of rubber should be added for stirring until it reaches the target temperature before starting.
(3) If the color of the glue in the pot changes from light yellow to dark brown, it means that the glue is aging and can no longer be used. Otherwise, the crispness of the gel after drying will seriously affect the quality of the book. Therefore, all the glue in the rubber pot must be removed and replaced with a new one.
(4) The hot melt adhesive must be preheated before use, and the temperature of the preheated rubber pot must be consistent with the temperature of the working rubber pot.
3. Regularly clean the glue pot
Regular cleaning of the glue pot is an indispensable step in the wireless adhesive bonding process, because any type of glue will produce some sediment at the bottom of the pot during use, which will affect the heating speed of the plastic pot. If it is not cleaned in time, some of the sediment will agglomerate and block between the rubber roller and the baffle, causing the glue to flow poorly. In severe cases, there will be a phenomenon of gel breaking on the rubber roller, which directly affects the thickness and uniformity of the brush on the back of the book, resulting in sometimes glue on the back of the book, sometimes without glue. If this phenomenon cannot be discovered in time, it will cause a page fault and cause a large number of finished books to be repaired. It can be seen that it is very important to clean the glue pot regularly.
Usually, the size of the visual equipment or the production interval to determine the cleaning cycle of the plastic pot, not only to keep the plastic pot clean, but also to ensure the book binding quality and production cycle.
Timely repair of page books
The wireless adhesive book produced by hot melt adhesive is repairable. Any problem of the quality of the bond found in the quality inspection can be repaired by the re-adhesiveness of the hot melt adhesive.
Especially in the 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 time, accurately determine the cause of the problem, and promptly remedy the books and periodicals to prevent the publication of books with quality problems. E.g:
(1) The back of the book may be caused by a double cover or a cover that is not firmly bonded to the back of the book.
(2) The back of the book is soft, which may be due to insufficient thickness of the glue layer or broken glue.
(3) There are many wrinkles on the back of the book, which may be due to insufficient thickness of the glue layer or insufficient clamping force.
(4) From the sky and the foot of the book, you can also find that the folds are empty and the posts are not uniform.
It should be noted that the restored books must not be as beautiful as the ones that were formed on the machine at one time. Therefore, it is not possible to rely on the repair and ignore the quality control in the production process.
Although there are many reasons for affecting the pages of wireless adhesive bookbinding, as long as the quality is strictly controlled and the operation is standardized in the various processes of production, the problem of the page offset of the wireless adhesive book can be solved. Moreover, with the rapid development of China's printing technology and the continuous improvement of the requirements of the post-press binding process, we should continue to learn new processes and knowledge when researching and solving practical problems arising in the production process.