The analysis of affecting die cutting performance --quality control measures for film coated products

1. influence of machining quality and assembly accuracy of components



From the single technical parameters of die-cutting machine, the difference between domestic die-cutting machine and foreign die-cutting machine is very small, but there is a big gap in die-cutting speed, precision, stability and reliability, which is mainly limited by the technical level of domestic manufacturing industry, many parts of the rough processing, error range is relatively large. The assembly is not accurate enough to cause the machine to run fast enough and the die cutting accuracy is not high enough. For example, the matching and manufacturing accuracy between the intermittent mechanism and the main transmission system and the chain row directly affect the improvement of the machine speed. If the assembly accuracy is not enough, it will affect the die cutting accuracy and cause the noise to rise. If the elbow bar pressure mechanism and the moving platform are matched, there must be a gap because of the relative motion. If the gap is determined unreasonably, it will cause impact load, vibration, noise, and then affect the speed and accuracy of die cutting.



2. speed of paper feeding and influence of positioning mechanism



At present, the paper feeding method commonly used at home and abroad is continuous paper feeding, that is, front sheet and back sheet paper always overlap together, this way of paper feeding stable and fast. But the paper feeding speed is fast, the paper will produce a great impact when leaning against the forward gauge, easy to cause paper curl or bounce, resulting in inaccurate positioning, precision decline. Therefore, the ideal die-cutting machine should ensure the die-cutting speed at the same time as far as possible to reduce the speed of paper movement on the feeding table, thereby reducing the impact of paper on the front gauge, ensure accurate positioning, to improve the die-cutting accuracy.



Printed matter is positioned by positioning mechanism before die-cutting. The positioning mechanism of the die cutting machine is composed of a front gauge, a side gauge, a front gauge mechanism and a back gauge mechanism. The positioning mechanism has a vital influence on the accuracy of the die cutting machine.



Paper is positioned by the front gauge and the side gauge before entering the teeth row. The function of the front gauge is to locate the paper longitudinally. If there are several front gauges installed, only two of them play a role in positioning. The rest of the front gauge must be precisely on the same horizontal line and play an auxiliary role. Otherwise, it will lead to over-positioning and reduce positioning precision. Degree. The height of the front gauge is adjustable. The height of the front gauge should be moderate in die cutting positioning. If the front gauge is set too high, it will cause the front edge of the paper to bend, thus affecting the positioning accuracy. Side gauge is used for lateral positioning of paper. There are usually two side gauge, but only one at work. In order to ensure accurate positioning, side gauge pulley pressure should be appropriate. If the pressure of the pulling wheel is too high, it will cause the side bending of the paper; if the pressure is too small, the paper will not be pulled in place and the positioning accuracy will be affected. In addition, because the positioning time is fixed, the positioning time of the front gauge and the side gauge will also affect the positioning accuracy, and then affect the die cutting accuracy, so the positioning time of the front gauge and the side gauge should be reasonably allocated.



After the paper is positioned, the paper passes the paper to the molding part to carry out die cutting indentation. The paper feeding tooth row is fixed on the intermittent conveyor chain. In order to ensure the precision of die cutting, it must stay in the accurate position. Therefore, when the paper feeding row moves to the end of the cardboard, the front gauge mechanism moves the row shaft to the position to complete the front positioning of the paper feeding row. When the conveyor chain conveys the paper feeding tooth row to the upper platform and the lower platform of the moulding part, the back gauge mechanism moves the tooth row shaft to the positioning point to achieve accurate positioning. Therefore, the front gauge and back gauge mechanism directly affect the die cutting accuracy.



3. the influence of intermittent mechanism, chain and paper feed row.



The movement of paper feeding row is a intermittent movement process, which is controlled by intermittent mechanism. Parallel indexing cam mechanism is widely used in the intermittent mechanism of flat die cutting machine. Compared with other intermittent mechanisms, it has the following characteristics: reliable movement; smooth transmission; follower movement law depends on the cam contour shape; turntable can achieve ideal expected movement and obtain good dynamic performance; turntable positioning reason in intermittent time The cam curve groove is completed without additional positioning device. When the machine is running at high speed, the cam contour is affected by the speed, acceleration, inertia and direction of the follower, resulting in vibration of the machine. This vibration is transmitted to the chain, coupled with rapid start and stop will cause the jitter of the paper feed row, thus affecting the speed and accuracy of the whole machine. Therefore, on the basis of dynamic analysis, it is necessary to design the cam profile dynamically to ensure the smooth movement of the intermittent mechanism itself.



The chain is a flexible part, and the links are connected by pins, so the pitch error is large. For a long time, because of wear and tear, the chain will elongate naturally, the error will increase, bring unstable factors to the transmission, affect the position of the positioning point of the paper feeding row, and then affect the precision of die cutting. When working, the chain should not be too tight or too loose, too tight chain wear faster, shorten the service life of the chain; too loose chain vibration, noise increased.

Paper feeding row is used to transfer paper. Solid row is often used in flat die cutting machine. It is easy to be deformed during the high-speed operation of the machine, thus affecting the positioning accuracy. Therefore, it is the direction of future development to change the solid tooth row into the hollow tooth row with higher hardness. In addition, when the paper-carrying tooth is working, it will produce noise, which will cause the vibration of the tooth row, thereby affecting the cutting speed, and will also have an impact on other parts. Usually the following measures can be taken: (1) as small as possible between the occlusion; (2) the paper teeth should be staggered from the regular plate; (3) appropriate adjustment of the angle of the teeth. In addition, the size of the pressure between the teeth will also affect the precision of die cutting, too much pressure between the teeth will damage the paper; too little pressure will cause the paper to slip or slip in the process of transmission; uneven pressure between the teeth may cause the paper in the die cutting tilt.



4. the influence of chain rail



In the process of die cutting, paper is driven by a chain. In addition to matching the chain wheel with the circular rotation, the chain passes through the position, and the guide rail locates it to control the movement direction of the chain and the row of teeth. Therefore, when installing and adjusting the guide rail, it is necessary to ensure that the guide rail thickness is suitable and can be embedded in the chain sheet. The distance between the upper and lower guide rails must ensure that the chain passes smoothly. If the distance is too small, the transmission resistance will be increased, the transmission speed will be affected, and even the machine will be damaged if it is serious. If the distance is too large, the chain will jump easily in motion, which will affect the transmission accuracy, and then affect the die cutting accuracy. In addition, the track and chain length of the guide rail also affect the performance of the machine.



5. impact of transmission system



The main drive system of die cutting machine is driven by worm and worm gear driven by motor. The transmission performance of the main drive system has direct or indirect influence on the speed and precision of die cutting. Worm gear is a kind of gear. Gear transmission has the characteristics of stable transmission, strong bearing capacity, good thermal process and high efficiency. The most common transmission gears are spur gears and helical gears, the two are compared, helical gear stability is better, the coincidence coefficient is large. At present, helical gear is widely used in die-cutting machine, but its pressure angle will affect its transmission stability. When the worm gear and worm mesh in the dividing circle, the backlash between the tooth and the tooth is suitable, the worm gear transmission is stable, the lubrication is sufficient, and the worm gear is in the best working state. Otherwise, if the backlash is too large, the worm gear transmission will be unstable and cause vibration; if the backlash is too small, it is not conducive to the flow of lubricating oil and accelerates the wear of the gear; if it is serious, it will make the worm gear mesh with the worm "top tooth", which will affect the transmission accuracy, and then affect the die cutting speed and precision.



6. impact of pressure institutions



Die cutting is done under pressure, so the most important mechanism of die cutting machine is pressure mechanism. At present, the most commonly used pressure mechanism in China is the double-elbow bar mechanism, which has the transmission characteristics that the movable platform can reach the highest limit position (also known as "dead point") twice during the course of crank rotation. In die cutting, the upper platform composed of the upper frame and the die cutting plate does not move, and the lower platform rises gradually from the lowest point to the highest point through the main transmission system and the elbow bar pressure mechanism, and moves back and forth. When the movable platform reaches the "dead point", the die cutting pressure is the biggest, at this time the elbow rod is straight, the pressure will be transmitted vertically to the base, the connecting rod and the crank are not stressed, effectively reducing the peak load of the connecting rod and the crank. In order to ensure the quality of die cutting, the whole platform should be uniform under pressure, so the working surface of the upper and lower platforms must be parallel. Therefore, it is particularly important to design and optimize the length of components. If the design is not reasonable, it will cause uneven die cutting pressure, excessive empty stroke and other adverse factors, affecting the speed and accuracy of die cutting.



The influence of die cutting board, die cutting knives and rubber strips


Die cutting mechanism is the core of die cutting machine, and die cutting and die-cutting knife and indentation line are the basic parts of die cutting. In order to ensure high precision die cutting, it is necessary to select high quality die cutting plate, die cutting tool and indentation line.



Good die-cutting plate requires uniform density, light weight, high hardness, good flexibility, easy processing, good flatness, strong, not easy to deformation and other characteristics. It is also required that the performance of the die cutter and indentation line embedded in the die cutting plate is reliable and stable, and that the new die cutter and indentation line can still be well combined with the die cutting plate after replacing the die cutting tool and indentation line many times. At present, most large and medium-sized printing enterprises in China use laser die-cutting indentation plate, although this plate is simple and convenient, but affected by environmental temperature, humidity changes, easy to deformation, affecting the accuracy of die-cutting. In addition, due to the relatively high die cutting pressure, if the layout size is too large, no plate frame or plate is not solid, then the plate table is easy to move horizontally in the production process. In addition, under the huge pressure, the center of the transverse plate may be deformed, and the die-cutting blade is prone to bend and other undesirable phenomena, resulting in the change of the die-cutting plate specifications, affecting the die-cutting accuracy.







With the diversification of packaging materials, products and the emergence of unique packaging design, high-quality die-cutting knives for different die-cutting materials have become a necessary condition to ensure the accuracy of die-cutting. The quality of the die cutting knife depends mainly on the sharpness of the knife edge, the height error of the whole knife and the condition of big knife bending. The sharper the knife edge, the smaller the height error of the whole knife, the smaller the big knife bend, indicating that the better the quality of the die cutting knife. In addition, the thickness of the die cutter should be uniform, uneven thickness or beyond the error range will lead to difficult insertion, deformation or loosening of the cutter line, thereby affecting the accuracy of die cutting. The height of the die cutter varies with the different packaging materials. For example, when the packaging material is double corrugated cardboard, the peak knife is used; when the packaging material is single corrugated cardboard, cardboard or thinner paper, the low peak knife is more stable.



In order to ensure the smooth running of paper, rubber strips need to be pasted on the main cutter line, and the elastic resilience of rubber strips is used to push the imprinted printed material from the cutter to prevent the imprint material from sticking. When selecting rubber strips, the height and thickness should be determined according to different products. Usually the height of the rubber strip is about 1-3 mm higher than the die-cutting blade, and the specific height should depend on the different printing materials. The rubber strip is too high, and it is easy to make die cutting inaccurate because the rubber strip touches the warped paper surface first when it is pressed. In addition, the hardness of rubber strip should also be moderate, if the rubber strip is too hard, die cutting is bound to produce a greater extrusion force on the die cutter, so that the knife edge deformation, affecting product quality; if the rubber strip is too small hardness, insufficient resilience, may cause "paste plate" or "loose plate". Therefore, the thickness and height of rubber strip should be selected reasonably according to the printing material, and the rubber strip should be pasted in the appropriate position to ensure the elasticity is moderate and reduce its adverse effect on die cutting accuracy.



There are many factors affecting the speed and precision of die cutting. In order to improve the speed and precision of die cutting and the stability and reliability of die cutting machine, in addition to optimizing the design of the mechanism of each component, accurately machining each component, and reasonably selecting the base material of each component, the ideal assembly precision is also very important to improve the stability and reliability of the machine.



In addition, the accuracy of equipment installation and commissioning also directly affects its production speed, product quality, stability and reliability. Improper installation and commissioning not only reduces the speed and accuracy of the whole machine, but also brings unexpected consequences and troubles to the actual production. Therefore, we must pay enough attention to it. And the quality of machine installation and debugging is related to the actual operator, therefore, actively training staff, improve the quality of staff and technical level is very necessary.



Film mulching is often used in the process of trademark making and packaging. However, in actual production, due to improper operation of the operator or other reasons, the product often causes wrinkling, blistering, crimping and other quality problems after coating. Bubble often occurs after a period of storage, which affects the quality of products, and even causes scrap in serious cases. Therefore, in the production, the operator must operate correctly, grasp each link, and make the product meet the quality requirements. The following is about the quality control of film coated products.



Control of products to be constructed



1. products waiting for construction must be straight. We must deal with the uneven paper with "lotus leaf edge" and "tight edge" phenomenon. The "lotus leaf" paper can be roasted, and the "tight side" paper can be hung for drying.



2. be sure to wait until the blot is dry before covering the film, otherwise it will cause blistering or hair removal.



3. printing as little as possible, otherwise the powder will be empty. The powder should be sprayed off before the film is covered. If there are more prints, the powder can be hanged and dried. If there are fewer prints, the powder can be wiped manually.



4. Paper filament direction, especially thick paper, should be paid attention to when coating, so as to reduce the crimp of paper caused by rolling and drawing.



Control of operation process



1. the thickness of glue should be appropriate. Too thick is easy to curl, and affect gloss; too thin, not enough viscosity, and even bubbling. Should be adjusted according to the product, the general coated paper should be properly controlled, and the offset paper should be properly controlled.



2. pressure should be adjusted according to the product situation. The pressure of general coated paper should be smaller than that of offset paper, and thin paper is smaller than that of thick paper.



3. the temperature is generally controlled at 40~60 C. If the temperature is too high, the paper and film will be deformed, resulting in product curl, but not too low, otherwise it will cause insufficient viscosity. The temperature of coated paper should be slightly lower than that of offset paper.



4. film tension should be appropriate. Generally speaking, it is appropriate to maintain normal work and not lag behind. Too tight is easy to curl the product and wrinkle it too loosely.



Control of temperature and humidity in workshop



1. In order to ensure the quality of the products, the temperature of the coating workshop should generally be suitable for the printing workshop, not too high or too low.



2. humidity is generally smaller than that in printing workshop. Too much humidity causes the product to be deformed or even wrinkled. It will cause curling after processing. Too little humidity will cause static electricity in the process of film mulching, resulting in the subsequent process being affected.



Control of raw materials



Proper selection of raw materials is based on product properties, paper thickness and quality requirements. The thin film used in general paper should also be thinner so as not to curl. High gloss films should be selected for high product requirements. The glue should be transparent and non precipitated. We advocate the use of precoating to reduce damage to human health.