Analysis of Factors Affecting Die Cutting Performance
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1. The influence of processing quality and assembly precision of each component
From the single technical parameters of the die-cutting machine, the gap between the domestic die-cutting machine and the foreign die-cutting machine is small, but there is a big gap in the die-cutting speed, accuracy, stability and reliability. Mainly subject to the technical level of domestic manufacturing, many parts are rough in processing, the error range is relatively large, and the assembly is not accurate enough, resulting in the machine running fast enough and the die cutting precision is not high enough. For example, the matching and manufacturing precision between the intermittent mechanism and the main drive system and the chain row directly affect the increase of the machine speed. If the assembly precision is insufficient, the die cutting precision will be affected and the noise will be increased. For example, if the toggle mechanism is matched with the moving platform, there must be a gap due to the relative motion. If the gap is determined to be unreasonable, the impact load will be generated, vibration will occur, and the noise will increase, which will affect the speed and accuracy of the die cutting.
2. The speed of paper feeding and the influence of positioning mechanism
At present, the paper feeding method commonly used at home and abroad is continuous paper feeding, that is, the front sheet and the back sheet are always partially overlapped, and the paper feeding is smooth and fast. However, the paper feeding speed is fast, and the paper will have a large impact force when it is leaning against the front gauge, which may cause the paper to curl or bounce, resulting in inaccurate positioning and reduced accuracy. Therefore, the ideal die-cutting machine should reduce the speed of paper movement on the paper feeding table while ensuring the die-cutting speed, thereby reducing the impact of the paper on the front gauge and ensuring accurate positioning to improve the die-cutting precision.
The printed matter is first positioned by the 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 rear gauge mechanism. The positioning mechanism has a crucial influence on the accuracy of the die cutting machine.
The paper is positioned by the front gauge and the side gauge before entering the gripper row. The function of the front gauge is to longitudinally position the paper. If multiple front gauges are installed, only two of the positioning functions are used. It must be precisely on the same horizontal line to play an auxiliary role. Otherwise, over-positioning will occur and the positioning accuracy will be reduced. The height of the front gauge is adjustable. The height of the die cutting should be moderate. If the front gauge is adjusted too high, the front edge of the paper will be bent, which will affect the positioning accuracy. The front gauge is too low, and the paper cannot reach the front gauge. Can not be positioned. The side gauges are used for lateral positioning of the paper. There are usually two side gauges, but only one is used for work. In order to ensure accurate positioning, the side gauge pull roller pressure should be appropriate. If the pressure of the paper roller is too large, the side of the paper will be bent. If the pressure is too small, the paper may not be pulled and the positioning accuracy will be affected. In addition, since the positioning time is constant, the positioning time of the front gauge and the side gauge also affects the positioning accuracy, which in turn affects the die cutting precision. Therefore, the positioning time of the front gauge and the side gauge should be properly allocated.
After the paper is positioned, the paper is conveyed by the paper feed roller to the molded portion for die-cutting. The paper feed row is fixed on the intermittent conveyor chain. To ensure the die cutting precision, it must stay in the exact position. Therefore, when the paper feeding row moves to the end of the paperboard, the front positioning mechanism moves the tooth row axis to the determined position to complete the front positioning of the paper feeding row. When the conveyor chain discharges the paper feeding tooth between the platform and the lower platform of the molding part, the rear positioning mechanism moves the tooth row axis to the positioning point to achieve accurate positioning. Therefore, the front gauge and the rear gauge mechanism directly affect the die cutting precision.
3. The influence of intermittent mechanism, chain and paper feed row
The movement of the paper feed row is an intermittent motion process controlled by an intermittent mechanism. The flat-type indexing cam mechanism is generally adopted in the intermittent die-cutting machine intermittent mechanism. Compared with other intermittent mechanisms, it has the following characteristics: reliable motion; stable transmission; the follower movement law depends on the contour shape of the cam; the turntable can achieve ideal expectations. Movement and good dynamic performance, the positioning of the turntable during the interval is completed by the curved groove of the cam, no additional positioning device is needed. When the machine is running at high speed, the cam profile is affected by the speed, acceleration, inertia magnitude and direction of the follower, causing the machine to vibrate. This vibration is transmitted to the chain, and the rapid start and stop will cause the tooth row to shake. , thus affecting the speed and accuracy of the whole machine. Therefore, on the basis of the analysis of the kinetics, the cam profile needs to be dynamically designed 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 of use, the chain will naturally elongate due to wear and the error will increase, which will bring unstable factors to the transmission, affecting the position of the positioning point of the paper feeding row, and thus affecting the die cutting precision. When working, the chain should not be too tight or too loose, too tight chain wear will accelerate, shorten the service life of the chain; too loose chain vibration and noise.
The paper feeding row is used to convey the paper. The flat die cutting machine uses the solid tooth row, which is easy to deform during the high speed operation of the machine, which affects the positioning accuracy, and because of its large quality, in the process of rapid transit It will not stop because of the inertia, which will affect the machine running stability and die cutting precision. Therefore, it is a future development direction to change the solid tooth row into a hollow tooth row with higher hardness. In addition, the gripper generates noise during operation, causing the tooth row to vibrate, which in turn affects the die cutting speed, and also affects other components. The following measures can usually be taken: (1) the gap between the plugs is as small as possible; (2) the grippers should be offset from the gauge plates; (3) the angle of the jaws should be adjusted appropriately. In addition, the pressure of the gripper will also affect the precision of the die-cutting. If the pressure of the gripper is too large, the paper will be damaged; if the pressure is too small, the paper will slip or slip during the transfer; the pressure between the grippers is not Both may cause the paper to skew during die cutting.
4. The influence of the chain guide
During the die-cutting process, the paper is driven by the chain. In addition to the cyclic rotation of the chain with the sprocket, the position of the chain and the guide rail position it to control the movement direction of the chain and the tooth row. Therefore, when installing and debugging the guide rails, it is necessary to ensure that the guide rails are of appropriate thickness and can be embedded in the links. The distance between the upper and lower rails must ensure that the chain passes smoothly. If the distance is too small, the transmission resistance will increase, affecting the transmission speed. In severe cases, the machine will be damaged. If the distance is too large, the chain will jump easily during the movement, which will affect the transmission accuracy. Affect the die cutting accuracy. In addition, the track of the guide rail and the length of the chain also have an effect on the performance of the machine.
5. The influence of the transmission system
The main drive system of the die-cutting machine is driven by the motor to drive the worm and the worm wheel. The transmission performance of the main drive system has a direct or indirect impact on the die-cutting speed and accuracy. The worm gear is a kind of gear, and the gear transmission has the characteristics of stable transmission, strong carrying capacity, good thermal processability and high efficiency. The most common transmission gears are spur gears and helical gears. Compared with the two, the helical gears have better smoothness and large coincidence coefficient. At present, helical gears are widely used in die-cutting machines, but their pressure angles affect the smoothness of their transmissions. When the worm wheel and the worm mesh at the indexing circle, the backlash between the gear teeth and the gear teeth is suitable, the worm gear transmission is smooth, the lubrication is sufficient, and the worm wheel is in an optimal working state. Otherwise, the side gap is too large, which will make the worm gear drive unsteady and cause vibration; the side gap is too small, which is not conducive to the flow of lubricating oil and accelerate the wear of the gear. When it is serious, the worm wheel and the worm will be “top teeth”, which affects the transmission. Accuracy, which in turn affects die cutting speed and accuracy.
6. Impact of pressure mechanism
Die cutting is done under pressure, so the most important mechanism of the die cutting machine is the pressing mechanism. At present, the most used pressure-applying mechanism in China is a double toggle mechanism, which has a transmission characteristic that the movable platform can reach the highest limit position (also called "dead point" twice during the rotation of the crank. During die cutting, the upper platform consisting of the upper frame and the die-cutting plate does not move, and the lower platform gradually rises from the lowest point to the highest point through the main transmission system and the toggle pressure mechanism, and reciprocates. When the movable platform reaches the "dead point", the die-cutting pressure is the largest. At this time, the toggle lever is straightened, the pressure is transmitted to the base vertically, and the connecting rod and the crank are not forced, which effectively reduces the load peak of the connecting rod and the crank. In order to ensure the quality of the die-cutting, the entire platform should be evenly stressed during pressurization. Therefore, the working surfaces of the upper and lower platforms must be parallel. Therefore, reasonable design and optimization of the length of the component is particularly important. If the design is unreasonable, it will cause uneven die-cutting pressure, excessive air travel and other undesirable factors, affecting the speed and accuracy of die-cutting.
7. Effects of die-cutting plates, die cutters and rubber strips
The die cutting mechanism is the core of the die cutting machine, and the die cutting plate and the die cutter and the indentation line are the basic components of the die cutting. In order to ensure high-precision die-cutting, it is necessary to use high-quality die-cutting plates and die cutters and indentation lines.
Good die-cut plates require uniform density, light weight, high hardness, good flexibility, easy processing, good flatness, firmness, and low deformation. It also requires the die-cutting knife and the indentation line to be embedded in the die-cutting plate to have reliable and stable performance. It can ensure that the new die-cutting knife and the indentation line can be combined with the die-cutting plate after replacing the die-cutting knife and the indentation line multiple times. At present, most large and medium-sized printing enterprises in China use laser die-cutting indentation plates. Although these plates are simple and convenient to install, they are easily affected by changes in ambient temperature and humidity, which affects the precision of die cutting. In addition, since the die-cutting pressure is relatively large, if the layout specification is too large, and the plate-mounted plate is not used or the plate is not firmly fixed, the plate can be easily moved laterally during the production process. In addition, under great pressure, the lateral version of the core may be deformed, and the die-cutting blade is prone to bending and other undesirable phenomena, which causes the die-cut plate to change in specifications and affect the die-cutting precision.
With the advent of packaging materials, product diversification and unique packaging design, high-quality die-cutting knives for different die-cut materials have become a necessary condition for ensuring die-cutting accuracy. The quality of the die cutter mainly depends on the sharpness of the knife edge, the height error of the whole knife and the situation of the big knife bend. The sharper the knife edge, the smaller the height error of the whole knife, and the smaller the large knife bend, indicating that the quality of the die cutter is better. In addition, the thickness of the die cutter should be uniform, and the uneven thickness or the error range may cause the insert to be difficult, deformed or the cutter line is too loose, thereby affecting the die cutting precision. The height of the die cutter varies depending on the die-cut packaging material. 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 stability of the low peak knife is better.
In order to ensure smooth paper feeding, it is necessary to stick a rubber strip at the main cutting line, and use the elastic restoring force of the rubber strip to push the embossed printed matter out of the knife to prevent the printing material from being stuck when the die cutting is indented. When selecting a rubber strip, its height and thickness should be determined according to different products. Usually, the height of the rubber strip is about 1 to 3 mm higher than that of the die-cutting blade, and the specific height should be determined depending on the printing material. When the rubber strip is too high, it is easy to cause the paper strip to be displaced and the die-cutting is inaccurate because the rubber strip first hits the raised paper surface. In addition, the hardness of the rubber strip should also be moderate. If the rubber strip is too hard, the die cutting will inevitably produce a large pressing force on the die cutter, which will cause deformation of the knife edge and affect the product quality; if the hardness of the rubber strip is too small, the resilience Insufficient, may result in "paste" or "bulk". Therefore, it is necessary to rationally select the thickness and height of the rubber strip according to the printing material, and stick the rubber strip at an appropriate position to ensure that the elastic force is moderate and reduce the adverse effect on the precision of the die cutting.
There are many factors affecting the die cutting speed and precision. In order to improve the die cutting speed and precision and the stability and reliability of the die cutting machine, in addition to optimizing the mechanism for designing each component, accurately processing each component, and rationally selecting the basis of each component. Outside the material, the ideal assembly accuracy is also critical to improving the stability and reliability of the machine.
In addition, the accuracy of equipment installation and commissioning 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 actual production. Therefore, it must be paid enough attention. The quality of machine installation and commissioning is related to the actual operators. Therefore, it is very necessary to actively train employees and improve the quality and technical level of employees.