Decoration (Printing, Coating)
Printing Technologies for Cans
Offset printing is a major method for printing on metal cans because of its hard and non-absorbent material. The printing methods are mainly classified into two types, dependent on the can structure. Sheet printing, using lithographic plates, for metal sheet is applicable to 3 piece and DRD cans. Alternatively, curved surface printing, using plastic letterpress plates, is applicable to 2 piece DWI cans and TULC.
| Can's classification | Decorative Type | Object to be printed | Types of Can | Printing Method |
|---|---|---|---|---|
| 3 Piece Can | Sheeting Printing | Coated Metal Sheet | Welded Can | Lithography Offset Printing |
| 2 Piece Can | DRD | |||
| Curved Surface Printing | Metal Can | DWI, TULC, aTULC | Letterpress Curved Offset Printing | |
| Lithography Curved Offset Printing | ||||
| Labeling | PET Film | TULC | Gravure Printing |
- (1) Sheet Printing
- Multiple same images are coated on a pre-processed metal sheet, and then the sheet is transferred to the sheet printing machine (the rotary offset printing machine) one by one for printing.
- The production process consists of coating and printing. Interior and exterior surfaces of sheets, such as tin plate, with a thickness of about 0.2 mm and large plates with a length and width of 1 meter are coated, and then each color is overprinted on each sheet.
- Production process includes; interior coating -> exterior coating -> printing (multiple times) -> finishing varnishing -> baking and drying
- Sizing (transparent paint utilizing the metal base for creating a metallic look) and white coating are used as substrates. After printing, varnish is applied by coating to protect the surfaces, and to provide gloss and smoothness.
- (2) Curved Surface Printing
-
- After forming the can-body, printing on the exterior surface of the 2 piece cans (DWI and TULC cans) is conducted one by one using a curved surface printing machine. Each color of ink is placed on a different (plastic letterpress) plate, and then sequentially transferred to a single rubber blanket, allowing all colors to be printed at one time. After printing and just before the ink curing process, an over varnish is applied.
- The line control system automatically manages production consistency, from can forming to finishing, including printing and coating.
- (3) Gravure Printing Lamination
-
- Technology that laminates pre-printed PET film onto formed cans using a gravure roll. Gravure printing is a type of intaglio printing, allowing drying and overprinting by color, offering advantages in the reproduction of a wide range of color gradation and density.
- A variety of reproduced effects can be achieved such as photograph quality resolutions, metallic, mirror-like effects, and pearl tone effects. This technology is also applicable to TULC, called laminated TULC.
