Offset printing can dominate printing for a long time, mainly due to the continuous improvement and innovation of offset printing technology and offset printing machines. Now the main achievements of technological innovation and technological improvement of sheet-fed offset presses in recent years are summarized to provide references for manufacturers and users of offset presses.
1. No side gauge technology
In recent years, the technology without side gauges is that during the continuous movement of the paper, the sensor continuously scans the edge of the paper and sends the scanned data to the control system. The control system sends instructions to the paper transfer mechanism for coarse adjustment. , And then make fine adjustments to ensure the correct lateral position of the paper. The non-side gauge technology does not require the pause time for front positioning and side positioning of the paper. The paper continuously advances, greatly increasing the available time, which is very beneficial to the stable positioning of the paper, improving the accuracy of overprinting and the machine speed. When replacing the printing material and work piece, no manual adjustment is needed, which reduces the adjustment time and the problems caused by improper adjustment.
2. Single-sheet paper shaftless drive feeder
Using shaftless transmission technology, the paper feeder is divided into several parts, which are driven by their respective servo motors. Generally, the separation head, paper conveying belt and front gauge, side gauge, and paper table lifting are driven separately. It is said that the application of the shaftless paper feeder can greatly improve the accuracy and stability of the paper separation system, and can separate substrates from thin paper to thick cardboard and corrugated cardboard and plastic sheets without replacing any parts.
The shaftless transmission technology is also used between the paper feeder and the printing unit to control the synchronization of the paper feeder and the printing unit.
3. Ink supply system without ink key
The traditional offset press ink supply system requires a lot of ink rollers, the structure is complicated, the adjustment is troublesome, and the water and ink balance is slow. People have been studying ink supply systems with simple structure and good performance. The ink supply system without ink key is one of the most successful. In this ink supply system, there is no ink area and no ink key, and there will be no problem of affecting the ink color of the surrounding ink area due to the adjustment of the ink key. There will no longer be a device to control the ink keys on the console.
There is no ink key ink supply system. At present, there are mainly anilox roller and doctor blade type and digital inkjet ink supply type.
4. Ink leveling device that can change the ink path and inking rate
The printing products are ever-changing, and a constant ink distribution device is difficult to meet the demand for ink supply. Thus, the ink leveling device which can change the ink path and the ink injection rate appeared. The typical structure of a sheet-fed offset press is a manroland company's ink leveling device that can change the ink path and inking rate, as shown in Figure 1. The ink leveling device, which can change the ink path and the inking rate, can be combined in different ways according to the different needs of the printed matter (it can also be switched during the printing process). The advantage is that the direction and flow of ink flow can be changed according to different printing conditions to achieve a perfect inking effect. The third state is adopted when printing is stopped. When reprinting, the water-ink balance can be quickly reached and the waste rate can be reduced.
Figure 1 Manroland variable ink leveling system
5. Water supply device capable of changing waterway and landing mode
In the ink system, the water path and the way of water can be changed by an intermediate roller between the first ink roller and the water roller. The rubber roller between the upper water roller and the first ink roller as shown in Figure 2 can be adjusted. If this intermediate roller leaves (dotted line position) is a pure conventional wetting system, if the intermediate roller is closed (solid line position) ), Part of the water can be applied to the printing plate through the first inking roller. The wing roller wetting system shown in Fig. 3 also moves the position of the water roller and contacts the intermediate roller. The fountain solution is applied to the printing plate through the first inking roller. If the water roller and the intermediate roller are separated, It is a general moist system. The use of adjustable or detachable intermediate rollers can change the watering method when needed, which is more conducive to quickly reaching a stable water-ink balance, so as to better meet the changing needs of different printed products and different wetting fluids. Now some high-end offset presses are already equipped with this device.
Figure 2 Conventional wetting system
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6. Closed-loop color control system
In the printing process, the scanning head is used to scan and measure the printing control bar or screen, and the measurement result is compared with the standard ink color. When the specified difference is exceeded, the computer automatically converts the difference into the ink tone setting value and automatically adjusts the ink supply. The amount (such as adjusting the position of the ink key) to make the color meet the requirements. The closed-loop color control system can objectively judge the color of the printed product, and is not affected by human and light. Reduce waste products, improve print quality, reduce machine adjustment time, and improve efficiency. In addition, the ink supply and water supply system calculated by the computer are used to keep the water and ink balance and make the ink color more uniform. Figure 4 is a comparison of the ink color change effect with or without a color control system.
Figure 4 Whether to apply color control ink color change system effect comparison
7. Anti-sticking and dirty treatment of imprinting and paper transfer roller
Single-sheet double-sided offset printing machine, except BB double-sided offset printing machine is printing on both sides at the same time, no matter what type of double-sided printing, after printing one side, the other side will be printed soon, the interval and distance are both It is very short, so the ink that is not dried on the first side will often stick to the impression cylinder and paper transfer cylinder of the second side printing color group, causing problems such as sticking, cross-coloring, and ghosting. Therefore, the surfaces of the impression cylinder and paper transfer cylinder of the second-side printing unit must be properly treated. Replaceable fiber sleeves (see Figure 5) and various sheaths can be installed on the impression cylinder and paper transfer cylinder. The common feature of various jackets is that the surface is specially treated to form a rough surface (see Figure 6) and has ink repellency. Although this jacket has ink repellency, it is not absolutely free of ink. Therefore, it must be cleaned after a period of use.
Figure 5 Fiber sheath
Figure 6 Enlarged view of the rough surface of the roller jacket
8. Online laminating device
Sheet-fed offset presses can now be laminated online. For example, ROLAND700 can cover the printing material before the color printing starts. The first unit of the printing press prints adhesive on the substrate, and the rubber cylinder of the second unit is wrapped with a film, and the film is glued to the corresponding part when the printing material passes by. This process is completed at normal temperature, which completely avoids the influence of temperature on the film and printing materials.
9. The plate cylinder of sheet-fed offset printing press is driven independently
Manroland and KBA use plate cylinders to drive on sheet-fed offset presses, that is, gears are still used during normal operation. In the pre-press preparation stage, the gear of the plate cylinder is disengaged and driven by a separate drive motor of the plate cylinder. Its main advantage is that each unit changes plates and plates at the same time, and cleaning is carried out simultaneously. The plate cylinder is driven separately, which has obvious effect on the multi-color offset printing machine. The more colors, the more significant the effect. A Manroland 6-color machine can complete 103 jobs in 24 hours, and change the printing plate every 14 minutes. Each plate prints 1000 copies. The machine can meet the requirements.
10. Online cold stamping
Online cold stamping is Manroland's patented innovative technology and won the 2006 PIA / GATFInterTech Technology Award. Online cold stamping is installed on two ROLAND700 printing units, as shown in Figure 7. It can be installed in any position of the machine, which is completely determined according to the needs. The first unit before putting the foil prints the special adhesive on the paper according to the pattern required by the cold foil. The second unit equipped with a foil laying mechanism bonds (hot stamps) the aluminum foil to the place where the adhesive is printed, and the remaining aluminum foil is taken away by the winding mechanism above the third unit. When cold stamping is not required, the first and second units can print normally as other units.
Figure 7 manroland connection cold stamping device
Online cold stamping has the following advantages:
(1) Printing and hot stamping can be completed at one time, which can achieve accurate overprinting; (2) Cold hot stamping does not require heating, will not cause paper deformation, and will not affect the aluminum foil and subsequent printing; (3) It can be printed on the aluminum foil to make the aluminum foil Arbitrary graphics and special color effects are formed; (4) Since re-printing can make the aluminum foil get different colors, the printing factory does not need to buy aluminum foil of various colors, only silver foil can be used to reduce inventory; (5 ) The operator does not need to master the hot stamping technology, as long as the offset printing technology is available; (6) When hot stamping is not performed, the original unit can perform the usual printing; (7) The cold stamping system can be installed on the old machine.
Figure 3 Foil roller wetting system
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