Manufacturing History: Aluminium foil rolling - Thinner, faster, wider

Manufacturing History

The manufacture of aluminium foil dates back to the beginning of the 20th century. Prior to 1900 small quantities of aluminium foil had been produced by hammering, a laborious and costly process, it wasn't until 1908 that the production of aluminium sheet in thicknesses down to 0.05 mm really began with so-called pack rolling, based on a patent taken out by Swiss entrepreneur Alfred Gautschi in 1908.

The process involved cutting a thin sheet of alufoil into pieces placing one on top of the other and re-rolling several times.

But it wasn't until 1910 that the process began to make giant strides when Robert Victor Neher and his partner Dr Edwin Lauber patented a method to produce strip and foil continuously using automatic coiling in a similar way to that used for tin. They produced usable aluminium foil strip in quantities of about 200 kilograms/month in thicknesses of 0.03 - 0.04 mm.

Alufoil quickly found an application for chocolate wraps and by the middle of the decade coloured, embossed and printed aluminium foil was being produced.

Between 1910 and 1920 a series of process-related problems associated with aluminium foil manufacturing were solved including slitting using rotary shears instead of a band saw, annealing of the ready-cut coils of foil, and grinding of the rolling rolls.

One of the pioneers of modern aluminium foil technology was Rheinische Blattmetall (Rebag) based in Grevenbroich, Germany. Founded in 1922 Rebag established methods capable of rolling aluminium foil 320 mm wide at speeds of 12-24 metres/minute with an average thickness of 0.012 mm.

After the end of the Second World War, productivity increased to a rolling width of 510 mm and rolling speeds of 80-90 metres/minute.

During the 1950s and 1960s, foil production underwent dynamic growth, with new investment in technology leading to the development of two-high, then three-high and subsequently four-high rolling mills playing a significant role. This resulted in further improvements to auxiliary machinery and special equipment such as coilers and straighteners, exit devices, strip and slitting shears, coil transport units and ingot saws. By the second half of the 1950s, rolling widths of 1,100 mm and speeds of 500 metres/minute were reached.

Aluminium foil's triumphant march as a barrier material in flexible packaging began in 1963 when thicknesses of less than 0.009 mm became possible. The rolling mills used high-purity steels for the rollers, which avoided the formation of rolling holes, while it also became possible to reduce successively rolling oil viscosity, thus increasing rolling speeds still further and also improving the annealing quality. At the end of the 1960s, it was possible to produce thin foils of 0.0065 mm, similar in thickness to the foils used today for aseptic packaging of liquids.

At the beginning of the 1970s, the first rolling line with integrated transport and high bay warehouse technology for strip and coils was commissioned. And by the mid-1970s, rolling speeds reached 1,500 metres/minute and the rolling width rose to 1,500 mm. Roll roughness is increased step-by-step and electroslag-refined roll materials are used. (The electroslag process is used for remelting and refining steels and special alloys to create high-purity product.)

During this period, a strip thickness control with fully hydraulic adjustment was incorporated into a roll stand for the first time. It replaced the electro-mechanical adjustment that was used previously and allowed a high degree of dynamic control based on roll-gap measurement.

Significant developments in rolling-mill technology were made during the 1980s with improvements to process engineering, drive technology, and control and instrumentation. Ever greater rolling speeds led to a considerable increase in the requirements for strip flatness and strip thickness necessitating fully automatic measurement, display and control of the strip flatness. In 1987, the rolling speed of new units reached 2,200 metres/minute and a rolling width of 1,800 mm; alufoil for flexible packaging was rolled down to a thickness of 0.00635 mm.

In the 1990s, the emphasis is on the optimisation and automation of the complete foil-rolling plant. This included plant optimisation to provide environmental protection (exhaust air purification) and occupational health and safety. Today, foil-rolling plants with rolling widths of up to 2,150 mm are commercially available and can produce aluminium foil as thin as 0.006mm at rolling speeds of 2,500 metres/minute.