Manufacturing

Introduction

Manufacturing, producing goods that are necessary for modern life from raw materials. The word manufacture comes from the Latin manus (hand) and facere (to make). Originally manufacturing was accomplished by hand, but most of today's modern manufacturing operations are highly mechanized and automated.

There are three main processes involved in virtually all manufacturing: assembly, extraction, and alteration. Assembly is the combination of parts to make a product. For example, an airplane is assembled when the manufacturer puts together the engines, wings, and fuselage. Extraction is the process of removing one or more components from raw materials, such as obtaining gasoline from crude oil. Alteration is modifying or molding raw materials into a final product—for example, sawing trees into lumber.

Science and engineering are required to develop new products and to create new manufacturing methods, but there are other factors involved in the manufacturing process. Legal matters, such as obtaining operating permits and meeting industrial safety standards, must be adhered to. Economic considerations, such as competition, worldwide markets, and tariffs, control to some degree what prices are set for manufactured goods and what inventories are needed.

History of Manufacturing

Manufacturing has existed as long as civilizations have required goods: bricks to build the Mesopotamian city of Erech (Uruk), clay pots to store grain in ancient Greece, or bronze weapons for the Roman Empire. In the Middle Ages, silk factories operated in Syria, and textile mills were established in Italy, Belgium, France, and England. New routes discovered from Europe to the Far East and to the New World during the Renaissance (14th century to 17th century) stimulated demand for manufactured goods to trade. Factories were built to produce gunpowder, clothing, cast iron, and paper. The manufacturing of these goods was primarily done by hand labor, simple tools, and, rarely, by machines powered by water.

Industrial Revolution

The Industrial Revolution began in England in the middle of the 18th century when the first modern factories appeared, primarily for the production of textiles. Machines, to varying degrees, began to replace the workforce in these modern factories. The cotton gin, created by the American inventor Eli Whitney in 1793, mechanically removed cotton fibers from the seed and increased production. In 1801 Joseph Jacquard, a French inventor, created a loom that used cards with punched holes to automate the placement of threads in the weaving process. The development of the steam engine as a reliable power source by Thomas Newcomen, James Watt, and Richard Trevithick in England, and in America by Oliver Evans, enabled factories to be built away from water sources that had previously been needed to power machines. From the 1790s to the 1830s, more than 100,000 power looms and 9 million spindles were put into service in England and Scotland (see Factory System; Industrial Revolution).

Mass Production

In addition to inventing the cotton gin, Eli Whitney made another contribution to the factory system in 1798 by proposing the idea of interchangeable parts. Interchangeable parts make it possible to produce goods quickly because repairs and assembly can be done with previously manufactured, standard parts rather than with costly custom-made ones. This idea led to the development of the assembly line, where a product is manufactured in discrete stages. When one stage is complete, the product is passed to another station where the next stage of production is accomplished. In 1913 the American industrialist Henry Ford and his colleagues first introduced a conveyer belt to an assembly line for flywheel magnetos, a type of simple electric generator, more than tripling production. The assembly line driven by a conveyor belt was then implemented to manufacture the automobile body and motors.

Labour Movement

Labor unions, associations of workers whose goal is to improve their economic conditions, originated in the craft guilds of 16th-century Europe. The modern labor movement, however, did not start until the late 19th-century, when reliable railroad systems were developed. Railroads brought materials from diverse locations for final manufacturing and assembly and created a large demand for industrial labor. Labor unions gained enormous strength after World War II (1939-1945) when the United States had both high inflation and a huge population of factory workers. This combination forced labor unions to negotiate for better contracts and wages, and they achieved significant influence in industry. Today fewer manufacturing jobs and the trend for factories to relocate to foreign countries have combined to diminish the strength of organized labor (see Trade Unions).

Military Operations and Manufacturing

When the United States joined the Allies against Hitler in World War II, the country was in its 11th year of economic depression, 17 percent of the workforce was unemployed, and manufacturers were unprepared to mobilize for wartime production. President Franklin Delano Roosevelt succeeded in motivating the industrial complex to invest in new manufacturing facilities through a combination of generous business contracts, tax laws, and patriotism. By 1943 manufacturing capacity had increased dramatically: 10,000 military airplanes were produced a month, and it took only 69 days to build a warship. When World War II ended, the United States was the leading producer of manufactured goods. After the war, part of this vast military manufacturing capacity was converted to create consumer items such as automobiles, furniture, and televisions.

The development of the Cold War between Communist and non-Communist powers was accompanied by a buildup of manufactured weapons such as fighter airplanes and bombers, submarines, missiles, and nuclear weapons. The shift to a military manufacturing base accelerated the development of space science and advanced electronics, particularly integrated circuitry, which would eventually become the processing engine for the modern personal computer. Computers, in turn, have helped increase the productivity of modern manufacturing plants because they enable automated design, production, and record keeping (see Computer-Aided Design/Computer-Aided Manufacture).

Types of Manufacturing

Manufacturing processes can produce either durable or nondurable goods. Durable goods are products that exist for long periods of time without significant deterioration, such as automobiles, airplanes, and refrigerators. Nondurable goods are items that have a comparatively limited life span, such as clothing, food, and paper.

Iron and Steel Manufacture

Iron manufacturing originated about 3500 years ago when iron ore was accidentally heated in the presence of charcoal. The oxygen-laden ore was reduced to a product similar to modern wrought iron.

Today, iron is made from ore in blast furnaces. Oxygen and other elements are removed when the ore is mixed with coke (a material that contains mostly carbon) and limestone and is then blasted by hot air. The gases formed by the burning materials combine with the oxygen in the ore and reduce the ore to iron. This molten iron still contains many impurities, however. Steel is manufactured by first removing these impurities and then adding elements, predominantly carbon, in a controlled manner. Strong steels contain up to 2 percent carbon. The steel is then shaped into bars, plates, sheets, and such structural components as girders (see Iron and Steel Manufacture).

Textile Manufacturing

Raw fibers of cotton, wool, or synthetic materials such as nylon and polyester go through a complex series of processes to form fabrics for apparel, home furnishings, and biomedical, recreation, and aerospace products. In most cases, loose tufts of fiber are straightened, and the thick ropelike slivers are thinned for spinning. In the spinning process, the fibers are twisted to add strength. Synthetic fibers are generally made in a continuous string, but sometimes they go through a texturing process to give them a natural appearance. These twisted fibers, known as yarns, are then woven or knitted into fabrics. Weaving is a process that interlaces two sets of yarns, the warp and filling, in a variety of patterns that impart design and different physical characteristics. Knitting is a technique that loops yarns together to form fabric. The fabrics are then dyed, and finishes applied (see Textiles).

Lumber Industry

The lumber industry converts trees into construction materials or the precursor material for pulp and paper. Trees are harvested, debarked, then sawed into usable shapes such as boards and slabs. The lumber is graded for use and quality and then dried in large kilns, or ovens. Lumber is manufactured into boards, plywood, composition board, or paneling. Pulp wood for paper is sent directly to the manufacturer without sawing or drying (see Lumber Industry).

Automobile Manufacturing

The automobile was the first major manufactured item built by a mass production system using cost-effective assembly line techniques. Today, before an automobile reaches its final assembly point, subsystems, such as the engine, transmission, electrical components, and chassis, are fabricated from raw materials in other specialized facilities. The metallic automobile body parts are stamped and welded together by robots into a unibody, or one-piece, construction. This body is then dipped in a succession of chemical baths that rustproof and provide undercoat and paint treatments. During the final assembly, conveyor systems direct all of the components to stations along the production route. The engine, transmission, fuel tank, radiator, electrical systems, body panels and doors, suspension system, tires, and interior accessories are fastened to the chassis. Rigid quality-control standards at every step ensure that the completed vehicle is safe and built to specifications (see Automobile Industry).

Aerospace Industry

The aerospace industry manufactures airplanes, rockets and missiles, among other technologies. The first airplanes were constructed from wood and fabrics; modern airplanes are built from aluminum alloys, titanium, plastics, and advanced textile-reinforced composite materials. As in automobile manufacturing, components such as engines and landing gear are manufactured in separate facilities and then assembled with the wings, rudders, and fuselage to produce the finished airplane. Final assembly is conducted on an assembly line, where the partially manufactured airplane is moved from station to station.

Rockets are built on an individual basis. Rocket casings are created by winding high-strength carbon fibers and epoxy resins onto a cylindrical shape. The epoxy hardens and encapsulates the fibers to produce a strong, lightweight material. Solid rocket fuel is put into the body of the rocket. Thrust nozzles and exit cones are then added along with electronic guidance systems and payloads.

Petrochemical Industry

Petrochemicals are manufactured from naturally occurring crude oils and gases. Once removed from the earth, the crude oil is refined into gasoline, heating oil, kerosene, plastics, textile fibers, coatings, adhesives, drugs, pesticides, and fertilizers. Crude oil contains thousands of natural organic chemicals. These are separated by distilling, or boiling off, the compounds at different temperatures. Gases such as methane, ethane, and propane are also released. Methane, when combined with nitrogen and pressurized and heated, yields ammonia, an important ingredient in fertilizers. Simple plastic materials, such as polyethylene and polypropylene, are manufactured by first heating ethane and propane gases and then rapidly cooling them to alter their chemical structure (see Petroleum).

FUTURE TECHNOLOGIES

Manufacturing systems today are designed to recycle many of their components. For example, in the automotive industry, excess steel and aluminum can become scrap stock for new metal, rubber tires can be chopped and mixed with asphalt for new roadways, and engine starters can be remanufactured and sold again. Recycling for newer materials, such as composites (combinations of materials designed with superior physical and mechanical properties), has yet to be developed, however.

Emission control will be a critical issue for future manufacturers. Smoke scrubbers must remove dangerous gases and particulates from industrial plant discharges, and manufacturing facilities that dump chemicals into rivers must develop methods of eliminating or reusing these waste products.

The economically advantageous automated factory has become the norm. Most automobile engines are manufactured using robotic tools and handling systems that deliver the engine to various machining sites. Computers with sophisticated inventory tracking programs make it possible for items to be assembled and delivered at the manufacturing facility only as they are needed. In demand-activated manufacturing, when an item is sold a computer schedules the manufacture of an item to replace the unit sent to the customer.

Engineers use computers to help them design new products efficiently. The Boeing 777 jet, for example, was developed in record time by having its entire design and manufacturing systems created on a computer database rather than using traditional blueprints.

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