THE ALUMINUM CAN
OMAR ELMOUGY- DOUGLAS 3
Aluminum is made from a plentiful material found in the earth's crust. It occurs naturally in a mineral called bauxite. Most bauxite is mined overseas and shipped to the United States for processing. The aluminum in bauxite is formed when the material is refined to remove impurities. The refining process produces a fine, white powder called alumina or aluminum oxide. Electricity "zaps" the aluminum powder with a continuous electric current, which separates the aluminum from the oxygen. The electricity melts the aluminum so that it is hot and bubbly, like lava. Next, small amounts of other metals are added to the molten aluminum to add strength and corrosion resistance to the final product. The molten metal is cast into ingots or blocks, which are then rolled into long sheets and coiled. The aluminum is then sent to the can or end manufacturing plant.
The aluminum beverage can is made with two pieces — the can body and the can end (or lid). The manufacturing process starts with coils of aluminum. Can plants use mass quantities of aluminum coil every day to make can bodies or ends. Each coil typically weighs about 25,000 pounds and, when rolled out flat, can be anywhere from 20,000 feet to 30,000 feet long and five to six feet wide. The aluminum is then cut into small rectangular parts that eventually make the can. All of the unused aluminum is recycled back into another roll sheet. The tin plate strip is unwound, its surface coated with a thin film of lubricant and the strip continuously conveyed to the deep-drawing press. At first a blank is cut out at each individual tool of the press; the drawing ram then presses this blank through the draw ring to form a cup. The tool is made up of 9 to 10 individual tools which are arranged next to each other and behind each other.
The cup is conveyed to the wall-ironing machine from the top. The ram first pushes it through the redraw ring to reduce its diameter to the punch diameter whilst retaining the sheet thickness. The cup is held by a blank holder to prevent puckers. There is a gap between the punch and the wall-ironing rings 1 to 4 immediately after the redraw ring where the wall thickness of the can is reduced by "ironing" the tin plate and consequently lengthening the can. At the end of this stroke, the punch with the can comes into contact with the base paneling tool and the can base is formed. When the ram is withdrawn, the can is removed from the punch by a stripper and conveyed out of the machine via an unloader belt.
In the trimming machine the can is held by a vacuum plate, set in rotation and then moved axially until it reaches the required trimming height. Then the movable cutter unit is guided to the can. Whilst the can rotates precisely once, the can rim between the upper and lower cutter is cut off burr-free at the required height. The rings cut off are removed by vacuum, pressed into bales and returned to the tin plate production facility.
The wall-ironing lubricant used in the can forming process is removed prior to coating the can internally and externally. The cans are transported to the washer on a wide belt and conveyed through several washing chambers upside down.
In this way the outside of the can is rinsed with tap water supplied through the jets located at the top and the inside of the can by the jets located at the bottom. Immediately downstream of the washing unit, the can is dried with dry air at a temperature of approx. 200° in the drying oven. The cans are coated on the outside as protection against corrosion and in order to apply a decorative design. White, gold or transparent coating as well as aluminum-colored coating can be used according to customer specifications. Generally the coatings are water-based. The cans are spaced by an intake wheel and drawn on to the coating mandrel of the mandrel wheel by means of a vacuum. They are then set in rotation around their own axis by the rotation belt. The coating film on the coater cylinder is then transferred to the cans positioned on the rotating coating mandrels. The coated cans are then blown off the coating mandrels and transported to the drying oven on a magnetic conveyor belt. The coating is pumped from a coating container to the engraved cylinder which transfers the appropriate quantity to the rubber-coated coating cylinder from where it is transferred to the cans.
The externally coated cans are spaced by the intake wheel, as in the coating machine, and drawn on to the mandrel wheel mandrels by means of a vacuum. The mandrels are set in rotation around their own axis by a rotation belt.
The can positioned on the mandrel rolls synchronously over the blanket and absorbs the complete decorative design with all the ink colors from it. The individual colors are transferred by the inking units to the blankets via ink boxes, various rollers and the cliché cylinder with mounted printing plate. The high pressure printing clichés only absorb ink in the parts in which they are raised. Therefore each inking unit presses one color ink onto the rubber blanket. Prior to the can coming into contact with the blanket, all the ink colors are on the rubber blanket entering the inking section; here the printed image is mirror-inverted. The inks are transferred to the can by rolling the can over the rubber blanket and the printed image becomes positive. The printed cans are then blown off the mandrels and conveyed to the drying oven by a magnetic conveyor belt.
The drying oven is basically divided into 3 zones (2 heating zones and 1 cooling zone). The heating zones serve to heat the cans and to evaporate the fluid constituents as well as to cross link the coating and the printing ink. The air in the heating zones is recirculated to reduce the amount of fresh air which has to be heated.
The exhaust air is supplied to the thermal incineration unit where the exhaust gases from the oven are incinerated to carbon dioxide and water without any residue. After leaving the heating zone, the cans are conveyed to the cooling zone and are adapted to the ambient temperature.
Inside the internal coating machine, the can is conveyed to a coating turret and positioned on a vacuum plate. It is set into rotation and passes two spray guns, the first one which coats the lower section of the body and the second the body and the base.
When the spray guns have applied the required amount of coating, the can is conveyed via a discharge belt to a collective conveyer and to the internal coating drying oven connected downstream.
The diameter of the can which is still cylindrical needs to be reduced in the upper section to accommodate the smaller end. During the necking process the can is loaded on to a lifter and the axial movement of the lifter presses the open edge into the outer tool. There the upper rim of the can is bent inwards and the diameter cylindrically reduced by approx. 1 mm. The lifter is then withdrawn, the can is pushed out of the tool using compressed air and conveyed to the next station. There the diameter is reduced further following the same procedure. A total of 15 stations are required in order to obtain the required final diameter. The flange is required in order to seal the filled can securely to the end. The flange is produced in the 16th station of the necking in and flanging unit.
The can is again loaded on to a lifter and pressed axially on to a flanging head. The open end of the can is bent outwards by the rotation of the three rollers of the flanging head spaced around the circumference and the flange is formed according to the geometry of the neck roller. The metallic bright can end is coated from the outside in the end coating machine. The cans are conveyed via the intake turret to the working turret. Each of the 6 magnetic chucks picks up one can at the flange and sets it in rotation around its own axis. Six spray guns rotate synchronously with the working turret and spray-coat the base of the respective allocated cans.
We test all the cans produced for holes and flange cracks. These two types of defect can occur due to the great degree to which the tin plate is formed. Each can is picked up by a support spindle and immediately moved in an axial direction until the open side has reached the flange seal. It is then conveyed passed a series of lights by the turret wheel. That means that light is shed on to the body of the can. If a hole or a flange crack allows light into the inside of the can, then the sensor on the open side of the can reacts in such a manner that this defective can is ejected whilst the machine is operating at full speed. This test is a continuous 100% test of the inside of the can. It is performed by a CCD line scan camera system comprising five cameras. Camera no. 5 monitors the end and the lower section of the can. Cameras nos. 1, 2, 3 and 4 concentrate on the respective internal section of the can allocated to them.
The images from the five cameras are compared with a specified image in the computer system connected downstream. As soon as one of the five camera images does not correspond to the specified data in the computer system, then the can is removed from the can flow via a blow-off station. The palletizing unit assembles the cans in up to 23 layers to a package unit almost 3 m high. The palletizing process starts by picking up an empty pallet. Layers of cans and interim layers are pushed on to the pallet until the required number of layers has been reached. A cover frame made of steel forms the top layer. Plastic strips are wrapped around the package criss-crossing twice in order to make it stable for transport.
SHELF LIFE AND USAGE
The life cycle of an aluminum beverage can is just 60 days from “can to can.” In this short time, a beverage can goes from the grocery store shelf to the consumer, and then on to a recycling facility where it can be re-melted into can sheet and reformed into another aluminum beverage can with exactly the same physical characteristics as the original can. Because aluminum can be recycled with no degradation in quality, aluminum cans are the ideal product for a closed-loop approach to recycling.
Stage 1 – Can Shredding
In the first step, bales of aluminum cans are shredded into pieces the size of a walnut in a 1,000-horsepower shredder. The shreds are then passed through a double magnetic drum separator to remove any steel that may have been mixed into the bale.
Stage 2 – De-coating
Following the can shredding process, any lacquer or paint on the aluminum is removed by blowing hot air (around 550°C) through the shreds on a slowly moving insulated conveyor. The exhaust gases from this process are first passed through an afterburner and then used to heat incoming process air via a heat exchanger, minimizing the energy requirements of the system.
Stage 3 – Melting
After being de-coated, the aluminum shreds are then fed into melting furnaces containing submerged stirrers that create a vortex in the pool of molten aluminum and drag the shreds quickly down into the melt. This process achieves rapid melting rates and high yields.The furnaces have fuel-efficient, state-of-the-art regenerative burners and burner management systems to reduce the amount of energy used and the impact on the environment. They are also equipped with jet stirrers, which ensure an even temperature and composition by promoting metal circulation within the furnaces. The stirring process ensures the highest-quality end product.
Stage 4 – Aluminum Casting
The molten metal is transferred into a holding furnace, where it is treated to remove impurities before casting the aluminum. Ingots are cast by tilting the holding furnace and pouring the molten metal into a casting unit. The metal is treated in a two-stage process to remove any remaining microscopic non-metallic particles and gases, with chemical composition and metal cleanliness tested on each cast.
As the metal flows into the molds, it is chilled by jets of cool water pumped around and through the base of the mold. The aluminum ingot solidifies gradually during the casting process, which takes approximately three hours. The finished 18-ton ingots, each containing approximately 1.5 million used cans, are shipped to a mill for rolling into the sheet from which aluminum can makers subsequently produce new cans and the whole process begins again.
Aluminum recycling facilities are regulated by the environmental authorities of the countries in which they operate and also must meet their own strict control measures. All of the waste gases from the shredding, de-coating, melting and holding operations are removed from the plant and treated in purpose-built emission abatement facilities, including cold dust collection systems and hot dust scrubbers. The cold dust scrubbers are used to remove the exhaust gases from the shredding and conveying operations while the hot dust scrubbers control the gases from the de-coating, melting and holding furnaces. Aluminum scrap other than used beverage cans (UBCs) is recycled through a similar process with various upgrading and processing technologies.
Reduce. "Reduce" means using fewer resources in the first place. This is the most effective of the three R's and the place to begin. It is also, I think, the hardest because it requires letting go of some very American notions, including: the bigger the better, new trumps old and convenience is next to godliness. But you don't need to let go completely or all at once. "Reduce" is a comparative word. It says: cut back from where you are now.
Reuse. Before you recycle or dispose of anything, consider whether it has life left in it. A jam jar can store leftovers. Food scraps can become compost. An old shirt can become a pajama top. An opened envelope can become a shopping list. A magazine can be shared. DVDs can be traded. A dishwasher can be repaired. A computer can be upgraded. A car can be resold. A cell phone can be donated. Returnable bottles can be, well... returned. Reusing keeps new resources from being used for a while longer, and old resources from entering the waste stream. It's as important as it is unglamorous. Think about how you can do it more.
Recycle. Recycling is the "R" that has caught on the best. Partly, this is because there are so many curbside recycling programs today (8,660 as of 2006, according to the EPA), which makes recycling so darned easy. What keeps it from being a total piece of cake is the rules. Every municipality has its own, and they are not always as straightforward as they could be.
"American Beverage Association | American Beverage Association." American Beverage Association | American Beverage Association. Web. 27 Apr. 2015.