1 Influencing factor of film thickness
In the production process of coating Colour Coated Steel Coil, the rolling direction of the backup roll, the coating roll, the draw roll, the roll diameter R, and the gap between the rolls will affect the coating film’s thickness. In the reverse coating mode, when the speed of the strip steel is lower than the speed of the coating roller, part of the coating will remain on the coating roller. At this time, the fluid lubrication between the coating roller and the strip is released, the wear is minor, and the coating process is always Stable; when the speed of the strip steel is higher than the speed of the coating roller, the paint on the coating roller can be transferred entirely to the strip steel. Dry friction will occur between the coating roller and the strip steel, which will cause the wear of the coating roller. When the gap between the rollers increases, the thickness of the coating film decreases with the increase of the gap, and the thickness of the remaining coating film of the draw roller increases accordingly. In addition, the smaller the roll diameter R, the more stable the roll coating system and the better the coating quality.
2 Control the coating thickness by adjusting the speed ratio of the rollers
Under specific parameters such as roller speed, belt speed, roller diameter, coating, etc., the roller coating process can be relatively narrow and stable working area. After the rotational speed of the draw roller and the rotational speed of the coating roller are determined, the total amount of coating film supplied by the coating roller to the strip steel per unit of time is also determined. At this time, if the speed of the strip is adjusted, the thickness of the coating film applied on the surface of the strip will change inversely proportional to it. After the traveling speed of the strip steel is fixed, changing the rotation speed of each roll will change the thickness of the coating film on the surface of the strip steel. If the speed ratio of the draw roll and the coating roll is increased, the thickness of the coating film on the surface of the strip will change in direct proportion to it.
3 Control the film thickness by controlling the pressure between the rolls
In actual production, the coating roll and strip are close together without gaps to obtain a thinner coating. In the case of two rigid rolls, it is theoretically impossible for the coating to pass between the applicator roll and the strip to be applied to the strip surface. On the other hand, the coating roll can be applied to the surface of the strip with a polyurethane rubber-lined coating roll. This is also why rubber-lined rollers must be used when rolling strips in production. When the production line speed and the rotation speed of the coating roll are determined, the thickness H1 of the coating film applied to the strip decreases with the increase of the pressure F between the coating roll and the strip.