Analysis of factors affecting die cutting performa

Post press processing: analysis of factors affecting die cutting performance

1 The influence of processing quality and assembly accuracy of various parts

from the perspective of single technical parameters of die-cutting machines, the gap between domestic die-cutting machines and foreign die-cutting machines is very small, but there is a large gap in die-cutting speed, accuracy, stability and reliability, which is mainly limited by the technical level of domestic manufacturing industry. The processing of many parts is rough, the error range is relatively large, and the assembly is not accurate enough, Cause the machine running speed is not 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 chain row directly affect the improvement of machine speed. If the assembly accuracy is not enough, it will affect the die-cutting accuracy and cause the noise to rise. Another example is that the elbow bar pressure mechanism is matched with the moving platform. Due to the relative motion, there must be a gap. However, today's road propaganda does not save money. If the gap is determined unreasonably, it will cause impact load, vibration, noise increase, and then affect the speed and accuracy of die cutting

2. The influence of paper feeding speed and positioning mechanism

at present, the paper feeding method widely used at home and abroad is continuous paper feeding, that is, the front paper and the back paper are always partially overlapped, which is stable and fast. However, the paper feeding speed is fast, and the paper will have a great impact when leaning against the forward gauge, which is easy to cause the paper to curl or bounce, resulting in inaccurate positioning and reduced accuracy. Therefore, the ideal die-cutting machine should not only ensure the die-cutting speed, but also try to reduce the speed of the paper moving on the paper feeding table, so as to reduce the impact of the paper on the front gauge, ensure accurate positioning, and improve the die-cutting accuracy

the printed matter is 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 side gauge before entering the paper take-up tooth row. The function of the front gauge is to position the paper longitudinally. If multiple front gauges are installed, only two of them play the role of positioning, and the remaining front gauges must be accurately 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 should be moderate during die cutting positioning. If the front gauge is adjusted too high, the front edge of the paper will be bent, which will affect the positioning accuracy; If the front gauge is adjusted too low, the paper cannot reach the front gauge and cannot play a positioning role. Side gauge is used for horizontal positioning of paper. There are usually two side gauges, but only one is used in operation. In order to ensure accurate positioning, the side gauge paper wheel pressure should be appropriate. Excessive pressure on the paper pulling wheel will cause the side of the paper to bend; Too little pressure may cause the paper sheet to be pulled out of place and affect the positioning accuracy. In addition, due to a certain positioning time, the positioning time of the front gauge and side gauge will also affect the positioning accuracy, and then affect the die-cutting accuracy. Therefore, the positioning time of the front gauge and side gauge should be reasonably allocated

after the paper is positioned, the paper is transferred to the molding part by the paper feeding tooth row for die cutting and indentation. The paper feeding tooth row is fixed on the intermittent transmission chain. In order to ensure the die cutting accuracy, it must stay at the accurate position. Therefore, when the paper feeding tooth row moves to the end of the paperboard, the front guide mechanism moves the tooth row shaft to the determined position to complete the front positioning of the paper feeding tooth row. When the conveying chain sends the paper feeding tooth row between the upper platform and the lower platform of the molding part, the back gauge mechanism moves the tooth row shaft to the positioning point to achieve accurate positioning. Therefore, the front and rear gauge mechanisms directly affect the die-cutting accuracy

3. The influence of intermittent mechanism, chain and paper feeding tooth row

the movement of paper feeding tooth row is an intermittent movement process, which is controlled by intermittent mechanism. Parallel indexing cam mechanism is widely used in the intermittent mechanism of flat pressing and die cutting machine. Compared with other intermittent mechanisms, it has the following characteristics: reliable movement; Stable transmission; The motion law of the follower depends on the contour shape of the cam; The rotary table can achieve the desired desired movement and obtain good dynamic performance. The positioning of the rotary table at intervals is completed by the curve groove of the cam, and no additional positioning device is required. When the machine is running at high speed, the cam profile is affected by the speed, acceleration, inertia and direction of the follower, causing the machine to vibrate. This vibration is transmitted to the chain. In addition, the rapid start and stop will cause the jitter of the paper feeding teeth, which will affect the speed and accuracy of the whole machine. Therefore, on the basis of dynamic analysis, it is also necessary to dynamically design the cam contour to ensure the smooth movement of the intermittent mechanism itself

the chain is a flexible part, and the chain links are connected with pins. Therefore, the pitch error is large. When used for a long time, due to wear, the chain will naturally lengthen and the error will increase, which will bring unstable factors to the transmission, affect the position of the positioning point of the paper feeding tooth row, and then affect the die cutting accuracy. When working, the chain should not be too tight or too loose. If it is too tight, the wear of the chain will accelerate and the service life of the chain will be shortened; Too loose chain vibrates violently and makes more noise

the paper feeding tooth row is used to transfer paper. The flat pressing die-cutting machine mostly uses solid tooth row, which is easy to deform in the process of high-speed operation of the machine, thus affecting the positioning accuracy. Because of its large mass, it will not be easy to stop due to large inertia in the process of sudden stop, affecting the stability of machine operation and die-cutting accuracy. Therefore, changing solid dental row into hollow dental row with high hardness is the direction of development in the future. In addition, the paper teeth will produce noise when working, causing the tooth row to vibrate, which will not only affect the die cutting speed, but also affect other parts. Generally, the following measures can be taken: (1) the clearance between plugs should be as small as possible; (2) The paper teeth should be staggered with the rule board of Lam's debut; (3) Properly adjust the tooth holding angle. In addition, the pressure of the paper teeth will also affect the die cutting accuracy. Excessive pressure of the paper teeth will damage the paper; Too little pressure will cause the paper to slip or slip during transmission; Uneven pressure between the paper teeth may cause the paper to skew during die cutting

4. Influence of chain guide rail

in the die cutting process, the paper is driven by the chain. In addition to the circular rotation of the chain with the sprocket, the position passed by the chain is positioned by the guide rail to control the movement direction of the chain and tooth row. Therefore, when installing and debugging the guide rail, it is necessary to ensure that the thickness of the guide rail is appropriate and can be embedded in the chain piece. The distance between the upper and lower guide rails must ensure the smooth passage of the chain. If the distance is too small, it will increase the transmission resistance, affect the transmission speed, and even damage the machine in serious cases; If the distance is too large, the chain is easy to jump in motion, which affects the transmission accuracy, and then affects the die-cutting accuracy. In addition, the track of the guide rail and the length of the chain also have a certain impact on the performance of the machine

5. The main drive system of the die-cutting machine is driven by the motor to drive the worm and worm gear. The transmission performance of the main drive system has a direct or indirect impact on the die-cutting speed and accuracy. Worm gear is a kind of gear. Gear transmission has the characteristics of stable transmission, strong bearing capacity, good thermal processability and high efficiency. The most common transmission gears are spur gears and helical gears. Compared with them, helical gears have better stability and large coincidence coefficient. At present, helical gears are widely used in die-cutting machines, but their pressure angle will affect the stability of their transmission. When the worm gear and the worm mesh at the indexing circle, the side clearance between the teeth is appropriate, the worm gear transmission is stable, the lubrication is sufficient, and the worm gear is in the best working state. Otherwise, excessive side clearance will make the worm gear drive unstable and cause vibration; The side clearance is too small, which is not conducive to the flow of lubricating oil and accelerates the wear of gears. In serious cases, it will make the top teeth when the worm gear engages with the worm, which will affect the transmission accuracy, and then affect the die cutting speed and accuracy

6. Influence of pressure mechanism

die cutting is completed 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 mechanism, which has the transmission characteristics that the movable platform can reach the highest limit position (also known as dead center) twice in the process of crank rotation. During die cutting, the upper platform composed of the upper plate 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 elbow bar pressure mechanism, and moves back and forth. When the movable platform reaches the dead point, the die-cutting pressure is the maximum. At this time, the elbow bar is straightened, and the pressure will be vertically transmitted to the base. The connecting rod and crank are not under force, effectively reducing the peak load of the connecting rod and crank. In order to ensure the quality of die cutting, the whole platform should be stressed evenly when pressurized. Therefore, the working surfaces of the upper and lower platforms must be parallel. Therefore, reasonable design and optimization of the length of components is particularly important. If the design is unreasonable, it will cause adverse factors such as uneven die-cutting pressure and excessive empty stroke, which will affect the speed and accuracy of die-cutting

7. The influence of die-cutting plate, die-cutting knife and rubber strip

the die-cutting mechanism is the core of the die-cutting machine, and the die-cutting plate, die-cutting knife and indentation line are the basic components of die-cutting. In order to ensure high-precision die-cutting, it is very necessary to select high-quality die-cutting plates, die-cutting knives and indentation lines

die cutting plates that need to tighten the foundation bolts of the experimental machine are required to have the characteristics of uniform density, light weight, high hardness, good flexibility, easy processing, good flatness, firmness, and not easy to deform. It is also required that the performance of the die-cutting knife and indentation line embedded in the die-cutting plate is reliable and stable, which can ensure that the new die-cutting knife and indentation line can still be well combined with the die-cutting plate after replacing the die-cutting knife and indentation line for many times. At present, most large and medium-sized printing enterprises in China use laser die-cutting indentation plates. Although this plate is simple and convenient to install, it is prone to deformation due to changes in ambient temperature and humidity, affecting the die-cutting accuracy in 2014. In addition, due to the large die-cutting pressure, if the layout specification is too large, the plate frame is not used for plate loading or the plate loading is not firm, it is easy to make the plate table move horizontally in the production process. In addition, under great pressure, the center of the horizontal version may be deformed, and the die-cutting blade is prone to bending and other undesirable phenomena, resulting in changes in the specification of the die-cutting version and affecting the die-cutting accuracy

with the diversification of packaging materials and 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 die-cutting accuracy. The quality of the die-cutting knife mainly depends on the sharpness of the knife edge, the height error of the whole knife and the bending of the big knife. The sharper the knife edge, the smaller the height error of the whole knife and the smaller the big knife bend, indicating that the better the quality of the die-cutting knife. In addition, the thickness of the die-cutting knife should be uniform. Uneven thickness or exceeding the error range will lead to difficulty in inserting the knife, deformation or too loose knife line, which will affect the die-cutting accuracy. The height of the die-cutting knife varies with the packaging materials of the die-cutting. For example, when the packaging material is double corrugated cardboard, use a peak knife; When the packaging material is single corrugated board, cardboard or thinner paper, the stability of low peak knife is better

in order to ensure smooth paper feeding, it is necessary to paste a rubber strip at the main knife line, and use the elastic restoring force of the rubber strip to push the stamped print out of the knife, so as to prevent the printing material from sticking during die-cutting indentation. When selecting rubber strips, their height and thickness should be determined according to different products. Usually, the height of the rubber strip is higher than