Analysis and Countermeasures of the most popular d

  • Detail

Analysis and Countermeasures of die cutting and line breaking

the proportion of die cutting in the carton process in the carton industry has increased rapidly in recent years, breaking through the scope of graphene as a whole. The preparation technology is long, mainly because the automatic packaging line introduced by the product packaging industry puts forward new requirements for the carton structure; Various special-shaped packing boxes (boxes) with exquisite design have also been widely used; At the same time, various high-end products (such as notebook computers, liquid crystal displays, etc.) put forward strict requirements for packaging; Why do some large carton factories come here to improve production efficiency? Die cutting into cartons is also widely used in the delivery demand of large quantities of products, so die cutting into cartons is popular, especially the round pressing die cutting method. Because of its unique advantages of high production efficiency, one-time completion of printing die cutting and relatively simple equipment manufacturing, it is increasingly used by carton factories

no matter what method is used for die cutting, whether it is flat pressing, circular pressing or circular pressing, and no matter how complex the product is, the whole process of die cutting is to complete two actions, one is to remove excess materials, and the other is to press out creases (lines) in advance for forming. The action processes of these two actions are different, and their stress conditions are also very different. By analyzing their stress process, we can see that cutting waste is to complete the cutting of paperboard by the cutter, and the contact between the cutter and paperboard is line contact; The line pressing refers to the deformation caused by the local crushing of the paperboard by the tool through the application of force, and the contact between the tool and the paperboard is surface contact. Whether the change of paperboard shape (cutting and crushing) can be realized depends on the pressure per unit area, that is, the pressure. In the process of die cutting, the force exerted by the die cutter and the indentation knife on the cardboard is certain, but because the contact surface between the cutter and the cardboard is different from that of the optical fiber cable, metal foil, fiber wire and plastic film, which are difficult to measure by the conventional extensometer, the pressure borne by the cardboard is different, and the pressure of the indentation line is less than that of the cutting line; At the same time, the cutting process is actually the process of paper breaking after being stretched by external forces, while the pressing process is actually the process of inner paper being stretched and corrugated being compressed. Generally, the compressive property of solid materials is much greater than the tensile property

from the simple force analysis made above, it can be seen that the force required to press the line is far greater than that required for cutting in order to complete the touch cutting process of paperboard. One is cutting and the other is crushing. Different physical change characteristics also determine why there are more pressing problems than cutting problems in die-cutting production. A clear understanding of the mechanical mechanism in the process of die cutting can help us solve many problems in die cutting production. Pressing line fracture is a quality problem often encountered in die-cutting production, and it is relatively difficult to solve. In general, we pay more attention to the cutting results. Although the shape is very important, the pressing line also cannot be ignored. It is related to whether the product can be formed smoothly, and whether the accuracy can meet the requirements after forming. In addition, the cracking of the pressing line will also affect the strength of the product, so the production process is simple and weakens the protective function of the packaging. In fact, the main reason why many products are returned after being delivered to customers is the problem of pressing lines

solving the problem of proper pressing depth without cracking is the key to improve the quality of touch cutting. It can be analyzed from three aspects: equipment, paperboard and operation. What causes the force of paperboard to exceed its breaking strength, so as to find a solution to the problem. In terms of equipment, whether the mold design is reasonable, especially whether the height of the cutting knife and the height of the crimping knife are reasonable. When the paperboard passes through the touch cutting part in the production process, the main thing that drives the paperboard forward is the line pressing. If the line pressing knife is too low, it will not only make the line pressing very shallow, affect the forming, but also cause die cutting to escape due to insufficient transmission force; But the line pressing knife is too high. Although the line pressing is deep, the cardboard will be broken due to excessive force. Therefore, the selection of cutter height is very important, which should be determined according to the requirements of single and double tiles, pressing depth, paper distribution quality, etc. In addition, the installation of wire pressing protective strips on both sides of the wire pressing knife can effectively reduce the cracking of the wire pressing. After installing the line pressing protector, the line pressing protector can pressurize the lining paper, corrugated paper and core paper on both sides of the paperboard line pressing place and produce soft deformation while pressing the line with the line pressing knife during die cutting, so as to effectively reduce the stress concentration phenomenon and reduce or eliminate the line pressing fracture

generally, the height of the thread pressing protective strip is about 0.9mm lower than that of the thread pressing knife, and the shape of the thread pressing protective strip can be selected according to the use effect. At present, soft die cutting is adopted in the round pressing die cutting. The cutter on the die will constantly cut on the polyurethane anvil pad to form many grooves and make its surface uneven. The reaction force of paperboard occupying each point of the pad during the die cutting process will also be different. Therefore, it is necessary to often check the flatness of the felt pad surface, and if there are deep grooves or gaps, they should be polished in time. There is also a large force on the die-cutting part when it works. The larger transmission clearance and the larger radial runout of the die-cutting wheel and anvil wheel during operation will be detrimental to the die-cutting quality, especially the phenomenon of line pressing fracture. The poor quality of the paperboard itself is also one of the reasons for the line breaking

when the warped paperboard passes through the touch cutting part, it is not only easy to cause die cutting to escape, but also because the pressure cannot be transmitted evenly, the stress at some points is too concentrated, breaking through the tensile strength of the paperboard and causing cracking; Some paperboards have the defects of too deep indentation line or too large anti inflation stress of the inner paper due to the excessive tension force of the inner paper or the excessive pressure of the pressure wheel during the drawing process. Such paperboards are broken when they are slightly subjected to external force, not to mention the large pressure when they are subjected to the pressure line. Even when cutting, the cutting edge is often cracked

of course, the cracking phenomenon of this kind of paperboard will be improved when the humidity increases, but it will also increase the difficulty of cutting and waste discharge. With the rise of paper price, there is little profit margin left in the carton, and the competition in the industry is becoming more intense. Therefore, carton factories will use their brains in the selection of paper, especially the inner paper. More and more t-paper, C-grade paper and even worse paper are used, and the rupture strength of these papers is very low. It is difficult to resist the pressure of line pressing when die-cutting. If the quality of such cardboard is a little poor when pulling sheets, the phenomenon of line pressing cracking during die-cutting is inevitable

of course, the operator's operation technology is also a very important link to reduce or avoid the line breaking phenomenon, and the adjustment of pressure and the control of speed are the keys. The adjustment of pressure during touching and cutting depends on the adjustment of the gap between the cutter wheel and anvil wheel. Under normal circumstances, the larger the gap between the two wheels is, the better. At this time, if there are other quality problems, such as poor cutting, escaping, etc., the operator often solves the problem by increasing the pressure of touching and cutting. Sometimes the problem is solved by accident, or it is called a crooked way, In most cases, new problems will arise, especially the phenomenon of line breaking. In addition, the touch cutting speed should also be controlled well and strive to be appropriate. Too fast speed means that the time for each piece of paperboard to pass through the touch cutting part will be shortened, and the cutting force and line pressing force during touch cutting will remain unchanged, that is to say, the acceleration of the force will be greatly increased, and the chance of causing line pressing fracture will naturally increase

source: Corrugated Box - Issue 4, 2005

Copyright © 2011 JIN SHI