Automatic Drip Coffee Maker

Background

Coffee was first cultivated in Ethiopia in the sixth century a.d. The coffee berries were consumed whole, or a wine was made out of the fermented fruits. Coffee as we know it, made from ground, roasted beans, dates to the thirteenth century, and by the fifteenth century, coffee was popular all across the Islamic world. The drink was introduced to Europe around 1615. The ancient method of preparing coffee was to boil the crushed roasted beans in water until the liquid reached the desired strength. The typical coffee pot was a long-handled brass pot with a narrow throat. This kind of pot is still used throughout the Arab world, and is known in the West as a Turkish coffee pot.

In England and America, boiling coffee in a sauce pan was for a long time the standard method. Sometimes the coffee was boiled for several hours; other classic recipes called for additions to the pot such as egg white, salt, and even mustard.

More sophisticated methods of brewing coffee evolved in France. The coffee bag, similar to the familiar tea bag, appeared in France in 1711. Ground coffee was placed in a cloth bag, the bag into a pot, and boiling water poured on top. Nearly a hundred years later, Jean Baptiste de Belloy, who was Archbishop of Paris, invented a three-part drip coffee pot. The top part of the pot held inside it a filter section made of perforated metal or china. Boiling water was poured through the filter section, and it slowly dripped down to fill the pot below. The percolator was invented in 1825. In a percolator, the pot full of water is placed directly on the stove burner. When the water boils, it condenses in the top of the pot, and then drips through a strainer basket filled with coffee. The Melitta filter—a plastic cone with several openings in the bottom, that holds a paper filter of finely ground coffee—appeared around 1910, as did the glass Silex, an hourglass-shaped filter pot.

The automatic drip coffee maker operates on the same principle as the Melitta and Silex, by dripping boiled water through finely ground coffee in a paper filter. This machine debuted in the United States in 1972 as the well-known Mr. CoffeeTM. Mr. CoffeeTM was an immediate success, and popularized the automatic drip method. As of 1996, some 73% of American households report owning an automatic drip coffee maker. In an automatic drip coffee maker, a measured amount of cold water is poured into a reservoir. Inside the reservoir, a heating element heats the water to boiling. The steam rises through a tube and condenses. The condensed water is distributed over the ground coffee in the filter through a device like a shower head. The water flows through the filter, infusing with the coffee, and falls into a carafe. The carafe sits on a metal plate which has another heating element inside it. This keeps the coffee warm. Some models have timing features, so that they can be pre-filled at night to make coffee at dawn. Other units have a temporary shut-off function, so the carafe can be removed from the warmer plate while the coffee is filtering. Others pulse the water over the filter at intervals, for a slower drip and more concentrated brew.

Raw Materials

Most automatic drip coffee maker parts are made out of plastic, including the body and the basket which holds the filter. The base plate, warmer plate, and heating unit are made out of various metals, usually steel or anodized aluminum. The carafe is made out of heat-proof glass. Other parts include timers, switches, and wiring.

The Manufacturing
Process

The parts for the automatic drip coffee maker are typically made by specialized shops. The digital clocks, timers, and switches are all purchased from companies that produce those items. The plastic parts are made at a plastics company, and the metal parts at a metal stamping plant. The manufacture of the actual coffee maker consists of putting all these parts together.

Injection molding

• 1 The plastic parts for automatic drip coffee makers are designed by the manufacturer and then outsourced to specialty plastics companies. The plastics company uses the manufacturer's design to make a mold. Then parts are produced by injection molding; heated plastic is forced into the mold under pressure, cooled, and released. These parts are then shipped to the manufacturer for assembly.

Stamping

• 2 The metal base plate is made at a specialized metal stamping plant. A sheet of metal is rolled out, and heavy machines punch out the specified shape. Then these are shipped to the manufacturer.

Assembly

• 3 The parts of the coffee maker are put together on an assembly line. The electrical components are assembled first. These are designed so they can be simply snapped together. Workers standing at the assembly line each snap in a part as it comes to them, and the whole line may have 40 to 80 workers, each doing a specialized job. The timer device is snapped in, then the cord. The metal warmer plate is snapped on, and then the thermostat is wired. The heater for the warmer plate is assembled, then placed on a a small pallet about the size of an index card. The pallets are placed on a conveyer belt that carries them through a sonic welding machine. This automatically welds the wiring for the heater. Once the internal wiring is complete, the rest of the pieces—the housing and the filter reservoir—are snapped together. Some pieces may be screwed in by workers using pneumatic screw drivers.

Packaging

• 4 After assembly, workers place the coffee makers in small cartons. Then workers place these cartons in larger packing cartons which might contain several units. These may be taped shut by hand, or they may be taped automatically by passing on a conveyor belt through a taping machine. Typically, another machine automatically imprints a bar code on the packing box, for tracking information. Then the boxes are stacked on large pallets and shipped or stored in a warehouse.

Quality Control

When the outsourced parts arrive at the coffee maker manufacturer, a receiving inspector checks them. Any defective parts are weeded out before they are taken to the assembly line. Then there may be several points along the assembly line where random pieces are removed and inspected. Typically, a hundred piece audit is done at the end of the assembly process. One hundred units are taken at random as they come off the assembly line, and these are thoroughly checked for internal and extemal defects.

The Future

European manufacturers are experimenting with coffee makers made out of a single plastic. The advantage of this is that the unit is recyclable. The single plastic can be melted down and re-used after the appliance is thrown away. There are distinct engineering problems to making a single-plastic coffee maker, since as many as six different plastics are used in some models to make up a single component. U.S. manufacturers do not seem as interested in single-plastic as European makers, but this may well become a global trend as recycling becomes more of an issue.

Where to Learn More

Books

Castle, Timothy James. The Perfect Cup. Addison-Wesley, 1991.

Roden, Claudia. Coffee. Faber & Faber, 1977.

Periodicals

Ellis, Beth R. "Mr. Coffee: the Man and His Machine." Weekly Home Furnishing Newspaper, June 15, 1987, pp. 1-3.

Huneve, Michelle. "Eat or Be Eaten." The New York Times Magazine, March 10, 1996, pp. 62-63.

—AngelaWoodward

Melitta drip coffee maker Invented by Dresden housewife Melitta Bentz, 1909, initially using blotting paper in the base of a tin can with holes punched through it.