Application of the most popular advanced motion co

2022-08-14
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Application of advanced motion control technology in printing equipment

today, the most common printing machines use flexographic printing technology. Flexographic printing is a kind of rotary printing method, in which patterns are printed on various substrates on the surface of raised patterns. That is, the non printing area of the rubber plate or photosensitive resin plate is withdrawn and lowered, and the desired printing pattern is generated on the printing plate. The printing plate is connected with a rotating cylinder with different diameters to obtain various sizes and patterns. The ink is transferred to the printing plate surface by an ink metering roller with a shape structure called a corrugated roller. Usually, the inkjet device works together with the scraper to supply ink to the roller. The above system operation can be repeated on the printer for each printing color. At present, the average number of printing stations on a printing machine is 10, and the web width is 6 to 136 inches

the main sports types in printing applications

printing applications are diverse, from simple monochrome printing to complex multi-color printing requiring positioning. Most printing applications use a rotary inkjet head containing the pattern to be printed, and the printing surface is usually a web of paper in direct contact with the inkjet head. Web paper is usually linear and can be composed of any kind of materials, including paper, plastic or resin film, corrugated paper, etc. The printing ink is directly supplied to the inkjet head. When the inkjet head contacts the web, the pattern is transferred to the web

in printing applications, the main motion type is spindle/slave shaft. The motion should be printed on the top. The web is the spindle and the inkjet head is the slave shaft. The traditional printing machine is mechanically connected between the web and the inkjet head. Now considering that the high-performance motion controller can perform electronic cam profiling, and the printing end user improves the flexibility of the machine, and hopes to shorten the production period and realize the requirements of rapid production conversion, the servo mechanism is usually used. This is especially true for inkjet heads, which also have this requirement for web spindles

multi color printing applications include multiple inkjet heads. Each inkjet head corresponds to a color and becomes a spindle slave shaft. Each inkjet head should be aligned with each other. Other types of motion printing applications are rare, such as moving the inkjet head into and out of the adjustment shaft for machine maintenance and product switching

typical printing applications require the use of a variety of motion control components, including feedback components such as encoders or resolvers, servo motors, reducers, servo amplifiers, and high-performance motion controllers. The motion control method used in printing can also be used in other paper processing applications where the rotary slave shaft contacts the linear web

main problems in motion control

there are several problems in realizing motion control in printing applications

first of all, when the inkjet head is in contact with the web, it is very important to accurately control the speed of the inkjet head. The speeds match each other, but the inkjet head speed will be higher or lower. Inaccurate speed matching will degrade the printing quality and may cause material damage

if the circumference of the inkjet head is the same as the length of the product, the motion relationship is a transmission ratio between the two, and there is also a position synchronization relationship (for example, they are proportional, but they are locked from a specific spindle position of the shaft, and the printing takes place in the correct position of the web). The circumference of the inkjet head is different from the length of the product. When the inkjet head contacts the web, it will produce speed matching. For the remaining length of the product, the inkjet head must accelerate or decelerate, and the appropriate position contacts the web to process the next product

in addition, when executing the motion curve, it is necessary to synchronize the speed and position. In this way, the relationship between the spindle/slave shaft can be effective at all spindle speeds from stop to full speed, and the scrap rate can be minimized. The speed depends on the substrate. The printing speed of labels is usually 300 ~ 1000 FPM. The speed of central embossing cylinder flexo printing on plastic (the web is wrapped around a large central embossing cylinder, and the inkjet head is positioned around the cylinder) is 1000 ~ 2000 FPM, while the speed of central embossing cylinder flexo printing on paper can exceed 3000 FPM

of course, there are exceptions. The speed of the web and the printing plate does not match, and one of the speeds can exceed or be less than 2% of the repetition length of the printing plate roller. The final customer can make the size as close as possible to the actual needs and accept the production capacity of the machine, which can save the plate cylinder/sleeve and greatly save materials

most printing applications also need positioning, and different positioning differences are great. The best positioning should be within 0.0005 inch, 0.002 inch for central embossing cylinder flexographic printing and 0.003 inch for line printing. The motion curve needs to be adjusted dynamically to compensate for small changes in the distance between positioning marks on the web. This is especially true in multicolor printing, in which accurate registration of colors must be maintained so that the final printed pattern has good quality

it is also important to design the motor/amplifier combination in the full range of product length. In design, the smallest and longest products may not represent the worst case. It is generally recommended that this design should be completed for several product lengths (such as 5 or 10) to ensure that a suitable motor/amplifier combination suitable for the whole product range is determined. The force and torque vary greatly with the size of the machine, and the load inertia also varies with the design. The design of motion control components should meet the inertia mismatch of 10:1 to 200:1

how to apply motion control technology to improve pre press and post press printing, and when possible, quantitative

it is crucial to the success of high-speed product positioning printing. To achieve high-speed positioning, it is necessary to provide high-speed position locking input to the driver or motion controller, and capture the precise spindle position when encountering the positioning mark. The difference between the front and rear positions is used to calculate the actual distance between the positioning marks. That is, the distance is compared with the theoretical distance between the marks, and a correction amount is calculated. Then, the correction amount is substituted into the slave axis motion curve

it is very important to produce high-quality products in the time required from detection to positioning mark to application of correction quantity. This time depends entirely on the motion controller used in this application, and will also be affected by the technology used (for example, some digital motion control networks have a transport lag that must be compensated. The "real" graphene only includes a single carbon atom layer with a single atom thickness, which may be unacceptable in some Applications). In some applications, special positioning algorithms need to be used, such as averaging several products that must be dried or many products, filtering the correction amount, or requiring some segments of the motion curve not to apply the correction amount. The motion controller shall also be able to properly handle web splicing and missing positioning marks

typical basic configuration 10 color printing machine production line has more than 65 closed-loop motion control axes. In larger production lines, there are usually more than 100 shafts. In the past, each shaft was mechanically driven, but now, the updated control system improves the positioning performance and reduces the positioning accuracy to half of the positioning accuracy value of the old system. These control systems are highly flexible and can cope with special tasks, providing infinite variable repetition. It is used to replace the speed matching method discussed above. It can enable users to increase or decrease the speed of the printing plate roller phase web to change the repetition length

Range grading refers to one of the opposite characteristic parameters of the experimental machine

these improvements can also make the speed faster, increase the maximum speed from 1200 FPM to 2000fpm, and achieve a higher speed in the flexographic printing process. The time for the printer to switch from one task to the next is shortened from an average of 4-6 hours to 30 minutes, and in some cases even shorter. The use of motion control and printing drive positioning system manipulator has a great influence on the switching time. Zhou Fulin, an academician of the Chinese Academy of engineering, is a member of the national Wenchuan earthquake expert committee. In the application, the whole control system provides better diagnostic information and prolongs the production time of the machine

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