The use of aluminum in packaging products offers a number of advantages in the beverage, food and cosmetic markets, making it an ever-growing packaging solution. Aluminum protects packaged products for a long time, as it is highly resistant to corrosion, light and oxygen. Also, despite being light, it is very durable due to the special properties of the alloys used. The most important advantage, however, is that aluminum is the most sustainable form of packaging, as it can be recycled indefinitely without degrading its original quality. In the past, food and beverage containers were made with 3 pieces of metal. The 3-piece cans, which were developed in the mid-19th century, consist of a cylindrical body wrapped in a piece of flat metal with a longitudinal seam (body) and 2 ends (can ends) which are joined to the body of the can. 3-piece boxes can be made in any practical combination of height and diameter.
In the middle of the 20th century, a new method of manufacturing aluminum boxes (DWI – Drawing and Wall Ironing) was developed, i.e. deep hollowing and rolling of the wall, which uses 2 pieces instead of the traditional 3 piece method. The DWI method was invented in the USA in 1958, expanded to the Japanese market in 1972 and has been widely used since then with application to aluminum and cast iron.
DWI boxes are made from aluminum rolls, which are first cup-shaped through the deep drawing process, and then converted into containers through several stages of wall stretching.
The process of drawing and wall ironing reduces the thickness of the wall by "ironing" it while at the same time stretching the container.
The above technology has been applied for many years to beer and beverage cans. In recent years there has been an attempt to use DWI technology in spray packaging boxes as well. To achieve this result a modified aluminum alloy with special thermo-mechanical treatment and high formability is needed.
In addition, unlike the traditional method, where the production of the product is made with a "pure" alloy of high purity, which is essentially a smelter alloy, in the new innovative production with the DWI method, an alloy with a high content of recycled material is used (recycling content), i.e. a greater percentage of post-consumer scrap is used, which has a positive effect on the circular economy and recycling.
Aerosol cans require high formability, because to form e.g. the "neck" of the aerosol bottle, the material must be able to withstand all this shaping - to meet particularly high formability requirements, which Elval (the aluminum rolling sector of ElvalHalcor) achieves by producing a special alloy with a special thermomechanical treatment in order to achieve the specifications and mechanical properties that the customer wants. It is characteristic that the bottom of the container has a dome shape to withstand the internal pressures. Also, unlike 3-piece containers, DWI containers offer the possibility of digital printing of the entire surface, as well as a wide variety of decoration methods and varnishes to enhance the overall image of the product.
