To ensure the flatness of the screen printing screen, you can start from the following aspects:
Screen frame selection and processing
Choose a suitable screen frame: The screen frame must have sufficient strength and rigidity to withstand the tension of the screen without deformation. Generally speaking, metal screen frames (such as aluminum alloy screen frames) perform well in strength and stability, and are suitable for making screen printing screens that require high flatness. Avoid using screen frame materials that are too soft or easily deformed.
Inspect and trim the screen frame: Before use, carefully check the flatness of the screen frame. If slight deformation is found, it can be corrected with some simple tools (such as woodworking clamps, bench vises, etc.). For uneven surfaces, sandpaper can be used to gently polish them to make the surface smooth and flat, so that it is easier to fit the screen later.
Screen selection and screen stretching operation
Choose a high-quality screen: The quality of the screen has a great influence on the flatness of the screen. A screen with uniform wire diameter, tight weaving and good tension consistency should be selected. For example, polyester screen (PET screen) has good stability and tension retention, which can provide a good foundation for the flatness of the screen.
Standardize the screen stretching process:
Control the screen tension: When stretching the screen, use professional screen stretching equipment (such as manual screen stretching machine, pneumatic screen stretching machine, etc.) to accurately control the tension of the screen. Different screen materials and printing requirements correspond to different tension ranges, and generally need to be operated strictly in accordance with the recommended tension value provided by the screen supplier. Appropriate tension can make the screen stretch flat and even on the screen frame, avoiding loose or locally tight areas, which will affect the flatness of the screen.
Apply tension evenly: During the screen stretching process, ensure that the tension is evenly applied to the screen. For example, by using a multi-point screen stretching method, tension is applied from different positions of the screen frame at the same time, so that the screen can be subjected to balanced tension in all directions, and then stretched flat. Avoid excessive tension at a single point, which may cause local deformation of the screen.
Selection of screen stretching angle: Reasonable selection of the screen stretching angle can also help improve the flatness of the screen. Generally, for most printing situations, a 45° stretching angle can make the warp and weft of the screen relatively balanced during the printing process, reducing the deformation of the screen caused by uneven force.
Let the screen stand after stretching: After the screen is stretched, do not perform subsequent operations immediately. Let the screen stand for a period of time (generally recommended to stand for about 24 hours) to allow the screen to be fully stable under the new tension state and further ensure the flatness of the screen.
Platemaking process optimization
Glue coating uniformity: When applying photosensitive glue or other platemaking glue on the screen, ensure that the glue is evenly applied. You can use special glue coating tools (such as scrapers, glue rollers, etc.) to apply glue in a certain direction and sequence. For example, starting from one end of the screen, scrape glue to the other end at a uniform speed to ensure that the glue layer thickness is consistent and evenly distributed, and avoid uneven screen surface due to uneven glue layer thickness.
Exposure and development control:
Exposure uniformity: When performing exposure operations, ensure that the light source of the exposure equipment is evenly distributed so that the photosensitive glue is evenly exposed on the entire screen. Exposure uniformity can be achieved by adjusting the position and angle of the exposure equipment and using diffusers. Uniform exposure can ensure that the curing degree of the photosensitive adhesive is consistent, thereby maintaining the flatness of the screen.
Development specification operation: The development process must be carried out strictly in accordance with the operating procedures. Use appropriate developer and correct development time, temperature and other conditions to ensure that the photosensitive adhesive is accurately removed or retained to avoid uneven surface or local defects of the screen due to improper development.
Screen use and maintenance
Correct installation and use: When installing the screen on the screen printer, ensure that the installation position is accurate and firmly fixed to avoid displacement or deformation of the screen due to improper installation during the printing process. During the printing process, the specified printing parameters (such as printing pressure, speed, etc.) must be followed to prevent excessive printing pressure or too fast printing speed from affecting the flatness of the screen.
Regular maintenance: After printing, the screen should be cleaned and maintained in time. Remove residual ink, glue and other debris on the screen, and then store it properly. Check the flatness of the screen regularly. If any signs of deformation are found, take appropriate corrective measures (such as re-stretching the screen, adjusting exposure, etc.) to maintain the flatness of the screen.
