The unit adopts pure fresh air heating method to improve the surface quality of home appliances and printed boards. In addition, in the pretreatment section, surface conditioning is added before the steel plate is passivated to increase the coating performance and the adhesion ability of the coating passivator. Printing is to print patterns or patterns on the steel plate. Its main feature is to add light patterns and varnish (glazing paint) to the existing color coating, which makes it more luxurious and bright-bright colors, prominent levels, better visual effects, and flash function; Packaging and decorative occasions can better achieve the purpose of beautifying the commodity and improving the competitiveness of the commodity; it can also improve the durability, corrosion resistance and formability of the product.