[…] the first step is to mine bauxite in Australia. Although the ore could in principle be mined in small amounts and sent along to the next step within a few minutes of the receipt of an order, the mining machinery is truly massive and the actual process involves scooping out millions of tons of bauxite at a go, in accord with a long-term production forecast. The mountain of ore is then transferred to massive trucks for shipment to a nearby chemical reduction mill where the bauxite is reduced to powdery alumina.

This process, which turns four tons of bauxite into two tons of alumina, requires about thirty minutes. When enough alumina is accumulated to fill ultra-large ore carrier (over two weeks or so; about 500,000 tons or enough for 10 million cans), it is shipped by sea—a four-week trip—to Norway or Sweden, countries with cheap hydroelectric power, for smelting. After about a two-month wait at the smelter, the application of an enorm­ous amount of energy (twenty times that needed to melt down and recycle 1 can) reduces two tons of alumina to one ton of aluminum in about two hours. Again, scale in smelting dictates that large amounts of aluminum be melted in each batch, with the molten aluminum poured into dozens of lots one meter on each side and ten meters long. These are then carefully cooled and stored for about two weeks before shipment by truck, boat, and truck to a hot rolling mill in Germany or Sweden.

After about two weeks of storage at the hot rolling mill, the ingot is heated to five hundred degrees centigrade and run through a set of heavy rollers three times to reduce the thickness from one meter to three millime­ters. The actual rolling process takes about one minute, but the machinery is extremely complex and difficult to change from one specification of prod­uct to another, so management has found it best to wait until there are orders in hand for a large amount of material of a given specification and then to process these orders all at once. When this is done for the specifica­tion of aluminum needed for cola cans, the aluminum sheet emerging from the rolling mill is wound onto a ten-ton coil and taken to a storage area, where it sits for about four weeks.

When needed for the next step, the coil is taken from storage and shipped by truck to a cold rolling mill, either in Germany or Sweden, where it is stored for about another two weeks. Cold rolling (at 2100 feet of aluminum sheet per minute—about 25 miles an hour) squeezes the aluminum sheet from 3 millimeters to .3 millimeter, the thickness needed by can makers. Because the cold rolling equipment is also extremely expensive and difficult to change over to the next product, the managers of the cold rolling mills have also found it most economical to accumulate orders for products of a given specification and do them all at once. The thin sheet emerging from the cold roller is then slit into narrower widths, wound onto ten-ton coils, and stored for about a month on average.

When needed for can making, the aluminum coils are shipped by truck, by sea, and again by truck to the can maker in England, where the coils are unloaded and stored, again for about two weeks. When needed, the coils are taken from storage to the can making machinery and run through a blanking machine which punches circular discs out of the aluminum sheet at the rate of four thousand per minute. The discs are then fed automatically into “wall drawing” machines, which punch the disc three times in succession to create a can without a top, at the rate of three hundred cans per minute per machine. (Thirteen forming machines are downstream from each blanking machine.)

From the forming machines, the cans travel by conveyor through a washer, a dryer, and a paint booth applying a base coat and then a top coat consisting of the cola color scheme plus consumer information in different languages and varying promotional messages. The cans then travel through lacquering, necking and flanging (to prepare the cans to receive their tops after filling), bottom and inside spraying (to prevent discoloration and any aluminum taste from getting into the cola), and on to final inspection.

The can making machinery just described (really just one big interconnected machine) is a technical marvel capable of converting a sheet of aluminum into a finished, painted can—with no human intervention—in less than ten seconds of actual processing time. However, it is also extremely expensive to change over from one type of can to the next and one paint scheme to the next, so management tries to produce large lots of each type. From the can maker’s standpoint this is clearly the most economical approach, and it also meshes with the practice of the smelter, hot roller, and cold roller of processing specific types of aluminum in large batches.

After inspection, the cans proceed to an automated palletizing machine which loads the empty cans on pallets, eight thousand to each pallet, and sends them to a massive warehouse for storage until needed, usually four weeks. In the warehouse, they are stored by type of can because the bottling firm eventually filling the cola cans needs a variety of cans with different labels for beverages besides plain cola (for example, diet cola, caffeine-free cola, cherry cola). And even for plain cola, the bottler must support many different packaging configurations and promotional campaigns. Each pack­age and many marketing campaigns require different information to be printed on the cans.Excerpted from Page numbers 39-41 of ‘Lean Thinking’ by Womack and Jones