Aerial visit to a Ball® factory of cans and lids


Cans

    

                     9 pages,  5.3 MB

















             

Cans

Cans are today one of the most used materials for Beverage Packaging, with 34% of the worldwide packaging applications. Following their application in the Food and Beverage industry, cans are divided in two categories:

  • Pressure Filling;
  • Vacuum Filling.


Their entire production process, filmed at a Central European plant, visible in the video above.

  In the extrusion process, the final product is obtained heating the bar of Aluminium and exercising high pressures, so to extrude it in the desired shape


Cans for Pressure Filling   

Cans for Pressure Filling are divided in:

  • 2-piece cans                                                                                                                                  The can version made of Aluminum contributes to environmental friendliness.  A 2-piece can consists of two components of a body integrated with a bottom lid and a lid with a lip (an opening). A technique called double seaming is used to attach the can body and can lids (top and bottom) and the contents are protected from external contamination. 
  • Draw Wall Ironing (DWI) Aluminium Can                                                                                        A 2-piece can comprising a can body and a lid produced by drawing and ironing (DWI).  


In this category, the can’s inner pressure is increased to values over the atmospheric values, by mean of gas.  The gas allows to maintain the rigidity of the can’s body.    The can end, its bottom, has is dome-shaped so to participate in gas action, preventing deformations of the can body.   Both models of can above are inspected into the Food and Beverage Bottling Lines for positive inner Pressure by mean of Electronic Inspectors equppped with inductive sensors detecting the shape of the lid.                                                                                   

                                                                           On right side, a 2-pieces can: a lid and a body



  The injection moulds used in the fabrication of the cans later adopted by the Beverage Bottling Industry








2-piece cans made of tin free steel, laminated with PET film on both the interior and the exterior surface, is processed into cups.   The same process applies to Draw Wall Ironing cans.  A large machine, called a Cupping Press, starts the can shaping process. The press cuts circular discs from the aluminum sheet and forms them into shallow cups.  The cups drop from the press onto the cup conveyor. These 2 metal-forming operations are performed at high speeds, around (2500 - 3750) cups per minute.  The scrap aluminum left over from these operations is removed and recycled.  Finally, a Washer Machine cleans and dries the can bodies, so they can be decorated. 

 2-pieces cans of Aluminum, the most commonly used in Beverage Bottling here depicted in their most common Standard format.  Several years ago a new format was launched, mainly in the USA market, named Slim.  Today, depicted in an image down, is object of launch a new kind of can, slimmer than the Slim and whose registered trademark is “Sleek”®  (image credit Rexam®).




Cans for Vacuum Filling



          





























In this type of can, its inner pressure results lower than the external atmospheric, reducing the amount of Oxygen which could otherwise degrade the Quality of the product.  These cans are particularly adapt for sensitive beverages based on milk.    The bottom of these cans is typically flat to easy the Inspection Technique named Tapping, where a (huge) Ultrasound transducer resonates during the passage of the (tilted upside down) cans.

Cans for Vacuum Filling are divided in:

  • Welded Cans                                                                                                                          3-piece cans composed of a welded can body, can end, and can lid. Applicable only to vacuum filling.   3-piece cans are made of a rectangular sheet rolled into a cylindrical body and there are two seaming methods of soldering and electric welding.   3-piece cans, as the name suggests, consist of three components: bottom lid, cylindrical body and top lid (a lid with a lip, say an opening, for a beverage can).  
  • Re-sealable cans                                                                                                                 Cans with an “easy to open and drink” eco-friendly crew cap with added functionality.    

     

      On right side, a 3-pieces can: a bottom, a lid and a body.  In evidence, the welding line




Cans Printing Technology

Whatever the kind of can, the traditional offset printing is a the fundamental method for printing on metal cans because of its hard and non-absorbent material. 

The printing methods are mainly classified into two types by their can structure:

  • sheet printing, using lithographic plates, for metal sheet is applicable to 3-piece and DRD cans; 
  • curved surface printing, using plastic letterpress plates applicable to 2-piece Draw Wall Ironing cans.


Sheet Printing

Multiple same images are coated on a pre-processed metal sheet.  Then the sheet is transferred to the sheet printing machine (the rotary offset printing machine) one by one for printing.  A line set up independently from a can forming line.

The production process consists of coating and printing. Interior and exterior surface of sheets, such as tin plate, with a thickness of about 0.2 mm and large tin free steel plates with a length and width of 1 meter are coated, and then each color is overprinted on each sheet.

Production process includes: 

  1. interior coating;
  2. exterior coating;
  3. printing (multiple times);
  4. finishing varnishing;
  5. baking;
  6. drying.




Sizing (a transparent paint utilizing the metal base for creating a metallic look) and white coating to improve whiteness are used as substrates.   After printing, varnish is applied by coating to protect the surfaces and to provide gloss and smoothness.






Curved Surface Printing

After forming the can-body, printing on the exterior surface of the 2-piece cans (Draw Wall Ironing and 2-piece cans) is conducted one by one using a curved surface printing machine. Each color of ink is placed on a different plastic letterpress plate, then sequentially transferred to a single rubber blanket.  This last, is a rubber surface to re-transfer an inked image to a can, allowing all colors to be printed at a time.  An over varnish is applied after printing and just before the ink curing process.


The new ‘Sleek'® design, slimmer than the former existing ‘Slim’.  Slim & ‘Sleek® cans present two factual advantages over the Standard can at the price of a gigantic negative. The Beverage can be cooled faster than requested by Standard cans and the ergonomic characteristics fit an human hand. The negative side is visible in the out feed of these cans by the Seamer Machine.  Because of the smaller relation between diameter and height, they are unstable: their sliding is superior to Standard cans, > 300 mm at 90000 cph.  When sliding is > 1/2 of the container diameter, the container identity shall be lost by the Shifting-Register of the Electronic Inspector which has to control Filler, Seamer Machines and out feed Conveyor.  ‘Lost' meaning the detection of defective Filler Valves and Seamer is reduced from a true correct information, one whose dispersion is spiked, to a statistical one  (image credit Rexam®).








Gravure Printing Lamination

It is a particular technology that laminates pre-printed PET film onto formed cans using a gravure roll. Gravure printing is a variety of intaglio printing, obtained by pouring ink on the engraved sheet, then allowing drying and overprinting by color, offering advantages in the reproduction of a wide range of color gradation, like the smooth color shading, and density.  A variety of reproduced effects can be achieved such as photograph quality resolution, metallic mirror-like and pearl-like appearances. This technology is also applied to laminated 2-piece cans.


Lids





The lid is made of a slightly different alloy than the aluminum for the base and sides of the can. The inward bulge of the bottom of the can helps it withstand the pressure exerted by the liquid inside it, but the flat lid must be stiffer and stronger than the base, so it is made of aluminum with more magnesium and less manganese than the rest of the can. This results in stronger metal, and the lid is considerably thicker than the walls. For cans of standard common dimension, the lid is cut to a diameter of 53 mm  (2.1 inches), smaller than the 66 mm  (2.6-inch) diameter of the walls. The center of the lid is stretched upward slightly and drawn by a machine to form a rivet. The pull tab, a separate piece of metal, is inserted under the rivet and secured by it. Then the lid is scored so that when the tab is pulled by the consumer, the metal will detach easily and leave the proper opening.

To ensure that the cans are made properly, they are automatically checked for cracks and pinholes. One in 50000 cans is commonly found to be defective.


2-pieces-cans med

  2-pieces cans on a Conveyor in a Beverage Bottling Line, after having been depalletized  (image credit Rexam®).




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