Exploration of Folding Problems in Bookbinding Folds

The problem of collapsing (folding) of bookbinding folding pages is more common. The existence of this problem has seriously affected the quality of books and bound products. In the quality requirements of CY/T7.2~7.9 national binding quality standards, it is stipulated that: ""The fold of the book is flat and tidy, and there is no obvious breakage or deadfold?""". According to this standard, the problem of wrinkling of book pages has become one of the important factors that affect the qualification rate and quality of book binding products.
In order to solve this problem, I remember that as early as 1960 when the “Selected Works of Mao Zedong” was folded with a folding machine, after repeated trials, he found a way to install the wheel cutter on the folding machine so that air could be excluded from the signature. , Solve the problem of fast folding paper wrinkles. However, for decades, this quality problem has not yet been completely resolved. In recent years, the author has found through careful observation and repeated experiments. The use of a flower wheel cutter on a folding machine does not completely eliminate the air in the signature, which is mainly caused by two factors:
One is that the opening of the flower wheel knife is too large and the marking is too short. As a result, there are still some residuals in the folded pages. Once the signatures are bound, the parts that are partially connected to the pages in the demarcation area will still have different sizes. Wrinkles.
The second is the page ""displacement difference"". We have also found in practice that the more pages are folded vertically, the more wrinkles the page has. In addition to the degree of air exclusion, this phenomenon is related to the fact that there is a certain "displacement difference" between the inner and outer pages of the signature. The inside pages of the signatures are different from the "displacement" "small", "outer page", "displacement difference", and "outside page" "displacement difference", which causes the pages of the inside and outside of the page to have different "displacement" values. Wrinkles occur, and the creases gradually taper from the point of the attached page to the cut. The more times the signatures are folded, the larger the "displacement difference" between the inside and outside pages of the signatures, and the more crumpling the book will have.
We will use the flower wheel knife to fold the folded signatures, where L2 is the length of the paper with the wheel cutter and L1 is the length of the paper (ie the length of the connecting part) that is not cut by the drug wheel knife. We feel in practice that the wrinkling of book pages is mainly related to the values ​​of L1 and L2. The larger the value of L1, or the smaller the value of L2, the greater the wrinkling of the signature of the signature. On the contrary, the smaller the wrinkling of the book pages. Because the smaller the value of L1 is, the smaller the "displacement difference" of the page is, the larger the value of L2 is, the larger the surface of air exclusion, and the wrinkle phenomenon of the book page is difficult to produce. Therefore, to eliminate the "displacement difference" and expand the air exclusion area, it is necessary to reduce the value of L1, and at the same time, increase the value of L2, that is, reduce the opening length of the flower wheel cutter and increase the cut length of the flower wheel cutter.
In response to this problem, we have made important choices and improvements to the flower wheel knife of the folding machine, and based on the number of folding times of the signature, we decided to use two kinds of flower wheel knife. These two kinds of flower wheel cutters were used on the ZYH660B type hybrid folding machine manufactured by Shanghai No.2 Printing Machinery Factory. After repeated trials, we found that the opening length of the flower wheel cutter (page length) L1=3.6~2.8mm, or The cut-out length of the flower wheel knife is L2 = 20~60mm, and the "number of teeth" "E<=8E<=3 of the flower wheel knife is the best. The "displacement difference" of its signature book page is "minimum, and air exclusion is the best." In the production process, the 16th edition (three-fold booklet) should take the flower wheel knife with E<=8, and the 32-page version (four-fold booklet) should use the flower wheel knife with E<=3. This can basically eliminate the problem of wrinkling of the book page, and it is extremely advantageous to improve the product quality of the book binding.
After our factory used these two kinds of flower wheel cutters on the folding machine, the folding of the binding book pages was basically solved. The effect of improving the binding quality of the books was very obvious. In 1998, the quality ranking won the first place in Jiangsu Province and achieved national In the ninth place, this year, Comrade Li Jiaxiang, director of the printed product inspection department of the Printed Product Quality Supervision and Inspection Center of the State Press and Publications Administration, inspected the quality of our products on site and observed the use of this type of wheel cutter in the folding machine to solve the book for batch products. The quality of the folded pages of the book pages is very exciting and very much appreciated.