Definition
A squeegee type automatic film coating machine is a laboratory instrument used to prepare uniform, controllable thickness wet film coatings on flat substrates. It drives a scraper or coating rod through a precision mechanical structure to move at a set speed and pressure on the surface of the substrate, evenly coating the coating or slurry into a film. The equipment is widely used in R&D and quality control links in the fields of coatings, inks, adhesives, electronic materials and new energy materials.
How it works:
The squeegee type automatic film coating machine works based on the principle of mechanical scraping. The instrument typically contains a rigid platform to hold the substrate, a height-adjustable scraper or coating rod, and a drive system. When working, an appropriate amount of sample is placed at the front end of the substrate, and the scraper is translated at a constant speed driven by the motor, and the gap between the lower edge of the scraper and the substrate determines the thickness of the wet film. The clearance height can be controlled by a precision fine-tuning mechanism, and some models also integrate a constant pressure device to ensure uniform force during the scraping process. Its basic relationship can be expressed as:
h ≈ k × g
where h is the thickness of the wet film, g is the gap height between the scraper and the substrate, and k is the coefficient related to the rheological properties of the material. The entire coating process is completed in a controlled environment to ensure the consistency and repeatability of the film layer.
Measurement method
Evaluation of coating quality typically involves measuring the thickness, uniformity, and properties of the coating after drying. The thickness of the wet film can be theoretically estimated by the set value of the scraping gap and the volume of the material, and more accurate measurement requires the use of a wet film thickness comb gauge for multi-point testing immediately after coating. The dry film thickness can be measured by micrometers, magnetic thickness gauges, or optical profilers. Film uniformity can be visualized by visual observation of interference frequencies or quantified using optical microscopy and surface profile scanners. Adhesion, gloss, color and other properties need to be tested in accordance with the corresponding industry standards using special instruments after the film layer is cured.
Influencing factors
The quality of the coating film is affected by multiple factors. Instrumental factors include scraper accuracy, translation speed stability, platform flatness, and parallelism between scraper and substrate. Operating parameters such as scraping speed, applied pressure, and coating angle can directly affect the shear force, which can change the spreading behavior of the material. Material properties are the key variables, and the viscosity, leveling, thixotropy and solids content of the sample determine its flow and film formation properties under shear. Environmental conditions such as temperature and humidity can affect the volatilization rate of solvents and the rheological state of materials. The surface energy, roughness and cleanliness of the substrate can also interfere with the wetting and adhesion of the coating.
Applications:
Squeegee automatic coating machines play an important role in many industrial and scientific research fields. In the coatings industry, it is used to prepare test paint films to evaluate color, weather resistance and mechanical properties. In the field of printing inks, it is used to simulate the printing process and study the transfer and drying behavior of ink layers. In the field of electronic materials, it is used to prepare conductive coatings, optical films or coatings for battery electrode slurries. In the adhesive industry, it is used to create uniform films to test bond strength. In the research and development of functional materials, it is used to prepare nanomaterial coatings, polymer films, etc., and serves cutting-edge research such as optoelectronics and sensing.
Selection considerations
When choosing a squeegee automatic coating machine, it is necessary to comprehensively consider the technical parameters and experimental needs. The coating range should cover common substrate sizes. The scraping speed range and adjustment accuracy need to meet the requirements of material shear rate. The thickness adjustment range and resolution should be adapted to the target film thickness. The type of scraper should be selected according to the characteristics of the sample, such as stainless steel scraper for general slurry, adjustable gap scraper for high precision requirements. The instrument should have good stability and repeatability. Additional functions such as vacuum substrate adsorption, temperature control platform, and programmed multi-stage coating can be expanded to expand application scenarios. At the same time, the ease of operation, safety protection design and compliance with relevant international standards of the instrument are also important references.