Definition
A wet film wheel gauge is a measuring tool used to measure the thickness of a coating in its liquid state. It is commonly used in coating, printing, anti-corrosion and other industries to quickly assess the thickness of wet coatings in the field to adjust process parameters in a timely manner. The measurement results of wet film wheel gauges help predict dry film thickness and have reference value for quality control.
Principle
Wet film wheel gauges are based on the principle of mechanical contact measurement. Its main body is three coaxial discs, flanked by fiducial discs of the same diameter, and in the middle is an eccentric measuring disc. When the wheel gauge rolls on the surface of the wet film, the middle disc will first touch the wet film, and as the rolling angle changes, the height difference between it and the reference disc will cause the wet film to produce traces. The thickness of the wet film can be obtained by reading the thickness value corresponding to the starting point of the wet film trace on the scale. This principle can be expressed as a geometric relationship: the thickness of the wet film is related to the radius difference and contact angle between the eccentric disc and the reference disc.
Measurement method
When measuring, the wheel gauge should be placed vertically on the surface of the wet film and rolled slowly along a straight line for more than half a week. Observe the position where the wet film traces first appear on the surface of the middle disc, and read the scale value corresponding to the position, which is the thickness of the wet film. Measurements should be taken immediately after the coating is applied to avoid solvent volatilization affecting the results. It is recommended to average multiple measurements per area for reliability. During operation, it is necessary to ensure that the wheel gauge is clean to avoid residue interference.
Influencing factors
Wet film thickness measurement is influenced by a variety of factors. Coating rheological properties such as viscosity and thixotropy can affect trace formation, leading to biased readings. Surface roughness can lead to unstable wheel gauge contact. Non-standard operating angles and speeds may introduce human error. Environmental conditions such as temperature and humidity may change the coating state. Additionally, the manufacturing accuracy and wear of the wheel gauge can also affect the measurement accuracy. Therefore, it is necessary to standardize the operation and take into account the actual conditions when measuring.
Application
Wet film wheel gauges are widely used in industrial coating, ship anti-corrosion, automotive spraying, architectural coatings and other fields. During the coating process, it is used to monitor the wet film thickness, helping to adjust the spraying parameters and avoid being too thick or too thin. In anti-corrosion engineering, it is used to ensure that the coating meets the design thickness requirements. In the printing industry, it can be used to detect ink layer thickness. Its portability and fast measurement characteristics make it suitable for on-site quality control.
Selection
The measurement range should be considered when selecting, and the common wheel gauge covers 0 to 1500 microns, and the appropriate range should be selected according to the coating thickness. In terms of material, stainless steel wheel gauges are corrosion-resistant and wear-resistant, making them suitable for most environments. The scale accuracy needs to meet the process requirements, and the general resolution is 5 to 25 microns. Additionally, consider wheel gauge size and feel to suit different field operation needs. When selecting a model, refer to relevant industry standards, such as ISO 2808, to ensure that the tool meets the specification requirements.