Some time ago, many internationally renowned screen printers decided to invest in the latest prepress equipment. The main reason was that they did not want to expand the existing workshop area, but also to adapt to the long-term changes in the future. Modern, revolutionary equipment system.
Digital stencil direct imaging system eliminates the use of photographic film and related chemical agents in the production of stencils. The textile industry, apparel and textile printing first accepted and adopted this new technology, and invested heavily in the purchase of digital pre-press systems. . Similar similar revolutions have taken place in the pre-printing process of offset printing. Films are no longer used. Directly from the computer to the printing plate, the plate making speed is faster and the resolution is higher.
In the graphic printing industry, the computerization of prepress technology is currently the most common topic, and screen printing is no exception. With a powerful computer system, more and more traditional process steps are processed faster and more accurately.
With this technique, the job to be printed is read and scanned by a platform or roller scanner, and the data received by the computer is accurately processed, adjusted and modified to suit the screen printing requirements. Then, all the detailed information data is stored in the database. When needed, the information can be transmitted to multiple piezo nozzles and the image can be directly sprayed onto the template with the photo-resist layer with the highest possible accuracy and sharpness. . This method is similar to non-contact inkjet printing, but the quality is much better. When the stencil image is sprayed, the stencil is exposed to a metal-halogen light source that is rich in UV light. No vacuum squeegee is needed because the wax image on the stencil is firmly fixed.
This new technology saves material and production costs compared to traditional stencil production. The use of a computer can also avoid errors caused by manual plate-making and the use of films. To keep screen printing competitive with all other graphic reproduction processes, it is necessary to save the high cost of the prepress process. In order to prevent other printing processes from taking away the small print market, screen printers used this modern plate-making technology to ease this severe situation.
The average advertising company requires a smaller amount of printing and faster service, and an image transfer system equipped with a computer-printing plate, such as JetScreen can meet this need. The investment in JetScreen will enable the printing company to be at the forefront of this business, and because of the rapid availability of low-cost, high-quality printed products, the return on investment is guaranteed.
This technology requires not only a plate-making worker with practical experience, but also a well-trained desktop publishing expert who can prepare and process all the information on the monitor VDU and can operate the system through the RIP station on the JetScreen.
The latest JetScreen technology enables large format templates to be produced economically and accurately at the factory without polluting the environment. So far, in the equipment installed directly from the computer to the printing plate in the world, only Luscher's digital stencil imaging system has more than 100 sets. The manufacturers installed are mostly web textile printers and large-format graphic printers. And industrial screen printers.
JetScreen system can handle a variety of screen sizes, the smallest screen size is 1 400mm × 1 800mm, the largest screen size is 3 500mm × 5 200mm. Extra size is suitable for large format posters, glass and corrugated board printing. The computer-to-plate system is very attractive for such large screens because it does not require the use of films and chemicals. It is done in the factory, which saves production costs.
The application of computer-to-screen digital imaging technology in the field of screen printing is as follows:
- Large-format printing plants that print advertisements, stickers, plastics and corrugated cardboard on paper and paperboard;
- furniture industry, printed wood and marble;
- machine panel (back illuminated dial), membrane switch (surface pattern and conductive silver paste);
- decoration of the interior wall of the aircraft;
- automotive glass (post-heating and front windshield, sunroof, etc.)
--Construction Glass;
- Glass doors and furniture glass for kitchen ovens and microwave ovens;
- Showcase window doors;
- Decorative mirrors;
--battery;
- Ceramic tiles;
- stadium decoration (ground, playing field) and other sporting goods;
- wallpapers printed on flat screens and rotary screens;
- UV spotlighting;
- T-shirts and sportswear printing;
- Print thin lines and halftone images on the banner.
JetScreen Digital Imaging Operating Procedures
The JetScreen system uses a precision-selective-resolution piezo print head with resolutions up to 633 × 633 dpi. This high resolution makes it possible to produce excellent monochrome and multicolor halftone images, all round Shapes, squares, ellipses, and other geometrical dots do not have any undesirable effects on the gray scales to avoid streaking during imaging. 65 line/inch network quality is guaranteed.
The imaging process must be performed under a yellow safety light because the coated stencil is photosensitive but no dark room facilities are required.
The nozzle system of the piezo print head maintains a warm state during operation, thereby keeping the nozzle open and free from clogging. The thermal wax tank and the piezo head in the control unit are equipped with several microfilters to prevent wax particles from clogging the nozzles and causing flow difficulties. The piezo head must be cleaned once a day. It should be done every morning when the wax in the system is heated. A small amount of wax flows through the nozzle and wets the nozzle wall. The process must not exceed 3 minutes. In doing so, the piezo head will work well one day. The wax tank in the control unit has a large volume, can add a few square meters to process once, when the wax in the wax tank drops to a certain level, the system will issue an alarm.
The wax heater consists of a preset timer and piping. The piezo head and JetScreen are on standby and ready for use.
The stencil image is accurately transferred to the coated stencil surface in a 1:1 ratio. At the operator station, the user can select the stencil's figure, size, and position on the stencil. Whether it is a negative or a positive image, it is possible to continuously shoot a continuous image or a single image.
At present, the finest dot and line width is 49 μm.
All of Luscher's JetScreen devices will have their computer hardware and software adapted to the ever-increasing technology needs for some time to come. Digital stencil imaging technology is the latest screen printing plate making technology. With the continuous improvement of technology, all devices will be constantly updated. Improving the quality of the template and accelerating the imaging speed is an important aspect for the user.
Ink media
The dyes in the Luscher Hot Melt Ink System are biodegradable, solvent free, and the solid particles are harmless to the environment. During the development process, cold water is used and dissolved under water at moderate pressure.
The hot melt ink system has an optical density of 4.0 or more and contains a large amount of effective UV photo-blockers, allowing the micro-levels of the template to be resolved during exposure. Using 65 lines/inch elliptical dots, the electronic template can be converted. 2% to 95% tone range.
Using the latest hot melt ink systems, stencils made by the JetScreen device can be developed with any type of developer, and any direct stencil material can be used. The transferred hot melt ink dissolves in a few seconds. The flushing water can be discharged into the waste water system without any environmental problems. It can also be recycled through the recycling system and reused after treatment.
The hot melt ink medium immediately solidifies upon contact with the surface of the coated stencil. Hot-melt inks are odorless, non-overflow, and non-proliferative, even when using low solids stencil materials or low-mesh screens. However, it must be known that the smoother the surface of the template (Rz value), the better the imaging effect of the template.
Template image conversion speed
The conversion speed of the image differs depending on the required resolution, sharpness, and fineness. There are many options available for printing jobs.
If the number of screen lines is 65 lines/inch, oval dots are used. With the best quality (single speed format), the printing area is 1 000mm×1 000mm, and the resolution is 633×633 dpi. The conversion speed needs about 20 minutes.
If the printing area is 1 000 mm x 2 000 mm, the resolution is the same as above, and the imaging direction is also similar, but the imaging time is not 2 times as mentioned above, but only 5 minutes is added, ie 25 minutes is shared.
If a lower resolution is used, the dots are coarser and between 40 and 50 lines/inch, the imaging speed is faster. In this case, with an elliptical dot, the imaging area is 1 000 mm×1 000 mm, and the imaging time is only 15 min. If the imaging area is 2m2, the imaging time is 20min.
When large-format posters are viewed from a greater distance, at least 60 cm or more, even if the resolution of the image processing is slightly lower, the quality of the entire print job will not be affected.
For a 33 line/inch thick dot or solid printing plate, the processing speed is faster, and a 1 000 mm×1 000 mm screen printing plate takes only 15 minutes.
Using JetScreen, a variety of geometric shapes and FM mesh points, or random mesh points can handle, and the conversion speed is fast. The operator can select JetScreen's imaging speed based on the fine level of printing, the viewing distance of the printed matter, and the size of the screen printing plate.
When comparing JetScreen's imaging speed with other devices, it is imperative that they be compared with other factors such as print size, print definition, resolution, and dot shape, otherwise it is not possible to draw true comparison results. .
The above data is based on the practical experience of the 65-line mesh modulation imaging in the international market. The lower the number of screen lines, the faster the imaging speed.
Author: Peigui Fan China Screen Printing and Graphic Imaging Association
Source: "Screen Printing"