Requirements for thick film printing screen printing machines
The screen printing machine is composed of three parts: the printing head structure, the screen plate, and the workbench. The uniformity and hardness index of the thick film screen silver with a thickness of 0.015 mm require the parallelism of the printing head, screen plate, and workbench of the screen printing machine. All indicators must be within a similar absolute horizontal range in order to produce products that meet the standards. Traditional screen printing machines are difficult to achieve the above data and have poor stability, which means that the maximum difference in film thickness after drying is constantly fluctuating and cannot be produced stably, resulting in an increase in product prices.
The author visited many enterprises and found through comprehensive analysis and research that the parallelism between the printing head scraper and the platform is 0.02 mm, and the parallelism between the bottom of the screen frame and the platform is 0.02 mm. The tension of the screen plate must be within a controllable range, with an error of no more than 1 um, which is considered a machine that can meet the requirements for product printing and brushing film thickness. If the above data is achieved, a stable control can be achieved by ensuring that the extreme difference in product drying film thickness is ≤ 0.015 mm.
To achieve the above data, the equipment needs to consider the precision of the printing guide rail and the degree of deformation of the guide rail mounting plate. The guide rail of the printing head adopts more precise imported guide rails, and the installation plate of the guide rail is cast and subjected to aging treatment to achieve long-term stable parallel effect; Moreover, the installation reference plane of the screen plate needs to use the same component as the printing substrate as much as possible in order to achieve parallel consistency.
The pressure and depth of the scraper are crucial factors. It is recommended to use a servo motor+electric cylinder to achieve this. Firstly, the pressure can be controlled, and secondly, an accurate value can be obtained for the depth of the pressure, so that the scraper always adheres tightly to the surface of the substrate. From the perspective of cost saving, the ink returning blade can be controlled by a cylinder, but it needs to be controlled by an electrical proportional valve to obtain a constant air pressure, in order to more accurately control the strength and depth of the ink returning blade.
The parallel operation of the product platform and the printing head, as well as the operation of the substrate, is recommended to use high-performance linear motors for motion power. Firstly, the parallelism with the screen and printing head is guaranteed, and secondly, the smoothness of operation is ensured. The linear motor can move quickly to avoid product shaking and reduce positional deviation caused by shaking. The parallelism of the substrate can be achieved by installing horizontal adjustment screws on the platform
