coil ppgi for wall cold rolled colour steel color coated galvanized metal sheet in coil1

The substrate type for producing color coated boards is crucial to the coating quality, and the main defects affecting the surface quality of the coating include wave edges, curling, and sickle bending.
Waves and Piaoqu
Wave edge refers to the wavy bending of a metal strip along its length, causing the surface to lose its flatness. Piaoqu refers to the phenomenon of high and low undulating waves appearing simultaneously in the length and width direction of a steel plate or strip, known as "Piaoshaped". Substrates with wave edge and curl defects may experience edge leakage on the color coating production line. The form of leakage is discontinuous or continuous due to the peak and valley values of wave edge and curl, greatly affecting the surface quality of the coating. Especially for the winding roller coating unit, due to the support of the support roller during the front coating of the strip steel, there is less leakage on the front side. However, when coating the back side, as the front side has already been coated, it is impossible to press the strip steel down with the roller, so leakage is prone to occur. The more wavy the wave edge, the more serious the leakage is. Waves and curls not only affect the coating quality of color coated boards, but also cause uneven pressure on the coating rollers, posing certain risks to the coating rollers, affecting their lifespan and increasing product costs.