Definition
A laboratory automatic film coater is an automated device used to prepare uniform and controllable thickness coatings on the surface of substrates. It replaces the traditional manual coating operation by mechanical or programmatic methods, realizes high repeatability and standardization of the coating process, and is widely used in sample preparation and performance testing in coatings, inks, adhesives, electronic materials and other fields.
How it works:
Automatic film coating machines usually work on the principle of coating with a squeegee or wire rod. The core of the device contains a precision mobile platform and coating head. The coating head holds the scraper or wire rod, and the platform carries the substrate. When working, the platform moves at a set speed, and the coating head evenly scrapes the appropriate amount of sample placed in front of the substrate on the surface of the substrate. The coating thickness is mainly determined by the diameter of the scraper gap or the wire winding wire, and the relationship can be approximately expressed as:
h ≈ k × d
where h is the thickness of the wet film, d is the scraper gap or wire rod diameter, and k is the coefficient related to the rheological properties of the material. The equipment controls the movement speed and pressure through stepper motors or servo systems to ensure linearity and stability of coating.
Measurement and calibration methods
The measurement of coating film thickness is divided into two types: wet film and dry film. Wet film thickness can be measured at multiple points using a wet film comb gauge immediately after application. The dry film thickness needs to be measured by magnetic thickness gauge, eddy current thickness gauge or microscopic cross-sectional method after the coating is completely cured. Equipment calibration is performed regularly, including calibration of platform movement speed (verified using a tachymeter), parallelism adjustment of the coating head (use a feeler gauge to check the uniformity of the scraper and platform gap), and thickness calibration (coating comparison using standard thickness sheets or known viscosity standards).
Influencing factors
Coating uniformity and thickness control are affected by multiple factors. Material factors include sample viscosity, leveling, solids content, and thixotropy. Materials with higher viscosity require higher coating pressure or clearance. Process parameters such as coating speed affect the shear rate, and too fast speed may lead to discontinuous coating. Too slow speed can easily cause sagging. Temperature and humidity affect the volatilization rate of solvents and the rheological behavior of materials under environmental conditions. The surface energy, flatness and cleanliness of the substrate also affect the adhesion and uniformity of the coating. The accuracy of the equipment itself, vibration control and scraper wear are also factors to consider.
Applications:
In the coatings industry, it is used to prepare paint film samples to test adhesion, hardness, abrasion resistance and weather resistance. In the field of printing inks, they are used to simulate the printing process and evaluate the color, gloss and drying properties of inks. It is used in the electronics industry to prepare specimens of conductive coatings, optical films, or packaging materials. Quality inspection institutions and scientific research institutes use it for the preparation of material standardization test samples, such as corrosion resistance test plates, optical performance test pieces, etc. In addition, it is also used in coating development and inspection in industries such as paper, textiles, and automotive materials.
Key points to consider when selecting
When selecting a model, it is necessary to first clarify the commonly used coating methods, such as scraping, spin coating or slit coating. The range of key parameters is determined based on common sample characteristics, including coating speed range (typically 0.1-500 mm/s), thickness range (micron to mm), maximum substrate size, and load weight. In terms of equipment accuracy, pay attention to speed stability, repeat positioning accuracy and platform flatness. Functionally, consider whether a heated platform, vacuum adsorption substrate, multi-speed program, or environmental chamber integration is required. The operation interface should be intuitive, easy to set and store parameters. Ease of maintenance involves ease of scraper replacement, clean design, and calibration tool kit. Finally, it is necessary to confirm that the equipment complies with relevant industry standards, such as ASTM D823, ISO 2808 and other standard methods involved in the preparation of coating films.