Scrap Extraction in the Can Making Industry

Can ends are the top of the can body in a two-piece type or the top and base in a three-piece type.

In beverage cans, the end is in the form of a ring-pull design and is known as an easy open end, or EOE. Most commonly today, these are manufactured in aluminium, like the body, but many are steel.

In food cans, the material is steel, and in a two-piece, design may be a plain/blank end or an EOE version. The can base end in a three-piece design is a simple disc design.

In the scrap extraction system a Chopper fan® provides the airflow though a ducting network to move the scrap waste from the pick-up points described above to the centralised collection in the baler room where the loose material is compressed into bales for cost effective transportation to the recycling process. The ducting network is carefully designed to balance the airflow between the numerous collection points maintaining air speeds in a tightly controlled range to ensure effective scrap extraction at every point.

In the baler room, the scrap is separated from the conveying air in an AMSP separator through a perforated plate screen. The scrap material then discharges for the base into the baler feed arrangement and the air is drawn from the clean side of the screen using a balance fan and discharged. The balance fan ensures the material feeding into the balers does so without pressure which would blow waste and dust into the surrounding area.

The Can Ends production starts at the shell press, the first stage of the process on blank or EOE versions where blank discs are cut and formed from a coil of metal, or from pre-cut plain sheets. From this process a waste offcut scrap lattice is produced which can be extracted from the shell press at high speed or centralised collection and recycling. Alternatively, on larger steel ends, the blanks are cut from a pre-cut flat sheet, rather than continuous coil feed, and the resulting lattice is larger but can be extracted from the press for transport to the recycling area, nonetheless.

For a plain end, there is no further waste produced, other than rejects, however in EOE manufacture there are futher stages where the ring pull sections are cut from a narrow coil in the conversion press, leaving a lattice strip waste and, separately the tab and chip are cut. This lattice waste can be combined with the shell press scrap above whereas the punched waste needs to be collected in a separate system and separated from the air using a cyclone.

The design of these cyclones has proved to be a critical one, to ensure the small metal particles discharge from the cyclone correctly, and without down pressure. Collection of the scrap pieces from the cyclone typically uses a big-bag system because the piece sizes are too small for a baling press. One alternative to the big-bag is to use a briquetting press which produces blocks of scrap for more cost-effective off-site transporation.