Accurate control of the coating die involves the following steps:

1. Install a die height adjustment mechanism to adjust the vertical position of the coating die.
2. Mount distance sensors on either the coating die or the coating platform to measure the gap between them.
3. Define a target height value and an allowable deviation based on the application environment.
4. Use the distance sensors to measure the actual gap between the coating die and the coating platform.
5. Compare the measured distance with the target height value, and adjust the die height via the height adjustment mechanism accordingly.
6. Continuously monitor the gap in real time using the distance sensors.
7. Establish an acceptable height range based on the target value and allowable deviation. If the real-time measurement falls outside this range, initiate a closed-loop adjustment to bring the die height back within the preset range.

Owing to its high controllability over coating thickness and uniformity, slot-die (extrusion) coating has been widely adopted in emerging industries such as thin-film solar cells, advanced display materials, optical functional films, and eco-friendly permeable membranes. As these new sectors demand increasingly stringent physical and chemical properties—and higher performance—from functional films, even more precise control over coating thickness and its uniformity is required.

Generally speaking, the quality of coated films (in terms of thickness and uniformity) is influenced by both the coating equipment and process conditions. Aside from the machining precision of mechanical components, die height control and coating speed control have the most significant impact on film quality.

During slot-die flat-bed coating, the process sequence typically includes: substrate transport, die lowering, coating (completion), and die lifting. Throughout this process, the coating die is subject to mechanical transmission forces, and manual or mechanical adjustments can introduce height deviations. Over extended operation, these errors accumulate, leading to greater inconsistencies in film thickness. With the aforementioned preferred solution—using distance sensors to directly measure the gap between the die and the coating surface in real time, combined with closed-loop control for automatic height correction—the influence of die height variations on the coated film is significantly reduced, enabling the production of high-quality films with consistent and uniform thickness.