Machine

This article is about devices that perform tasks.
Wind turbines

The scientific definition of a machine is any device that transmits or modifies energy. In common usage, the meaning is restricted to devices having rigid moving parts that perform or assist in performing some work. Machines normally require some energy source ("input") and always accomplish some sort of work ("output"). Devices with no rigid moving parts are commonly considered tools, or simply devices, not machines.

People have used mechanisms to amplify their abilities since before written records were available. Generally these devices decrease the amount of force required to do a given amount of work, alter the direction of the force, or transform one form of motion or energy into another.

Modern power tools, automated machine tools, and human-operated power machinery are tools that are also machines. Machines used to transform heat or other energy into mechanical energy are known as engines.

Contents

Hydraulics devices may also be used to support industrial applications, although devices entirely lacking rigid moving parts are not commonly considered machines. Hydraulics are widely used in heavy equipment industries, automobile industries, marine industries, aeronautical industries, construction equipment industries, and earthmoving equipment industries.

History

Flint hand axe found in Winchester

Perhaps the first example of a human made device designed to manage power is the hand axe, made by chipping flint to form a wedge. A wedge is a simple machine that transforms lateral force and movement of the tool into a transverse splitting force and movement of the workpiece.

The idea of a simple machine originated with the Greek philosopher Archimedes around the third century B.C.E., who studied the Archimedean simple machines: lever, pulley, and screw. However the Greeks' understanding was limited to statics (the balance of forces) and did not include dynamics (the tradeoff between force and distance) or the concept of work.

During the Renaissance the dynamics of the Mechanical Powers, as the simple machines were called, began to be studied from the standpoint of how much useful work they could perform, leading eventually to the new concept of mechanical work. In 1586 Flemish engineer Simon Stevin derived the mechanical advantage of the inclined plane, and it was included with the other simple machines. The complete dynamic theory of simple machines was worked out by Italian scientist Galileo Galilei in 1600 in Le Meccaniche ("On Mechanics"). He was the first to understand that simple machines do not create energy, they merely transform it.

The classic rules of sliding friction in machines were discovered by Leonardo da Vinci (1452–1519), but remained unpublished in his notebooks. They were rediscovered by Guillaume Amontons (1699) and were further developed by Charles-Augustin de Coulomb (1785).

Impact

Industrial Revolution

Main article: Industrial Revolution

The Industrial Revolution was a period from 1750 to 1850 where changes in agriculture, manufacturing, mining, transportation, and technology had a profound effect on the social, economic, and cultural conditions of the times. It began in the United Kingdom, then subsequently spread throughout Western Europe, North America, Japan, and eventually the rest of the world.

Starting in the later part of the eighteenth century, there began a transition in parts of Great Britain's previously manual labor and draft-animal–based economy towards machine-based manufacturing. It started with the mechanization of the textile industries, the development of iron-making techniques and the increased use of refined coal.

Mechanization and automation

A water-powered mine hoist used for raising ore. This woodblock is from De re metallica by Georg Bauer (Latinized name Georgius Agricola, ca. 1555) an early mining textbook that contains numerous drawings and descriptions of mining equipment.

Mechanization is providing human operators with machinery that assists them with the muscular requirements of work or displaces muscular work. In some fields, mechanization includes the use of hand tools. In modern usage, such as in engineering or economics, mechanization implies machinery more complex than hand tools and would not include simple devices such as an un-geared horse or donkey mill. Devices that cause speed changes or changes to or from reciprocating to rotary motion, using means such as gears, pulleys or sheaves and belts, shafts, cams and cranks, usually are considered machines. After electrification, when most small machinery was no longer hand powered, mechanization was synonymous with motorized machines.

Automation is the use of control systems and information technologies to reduce the need for human work in the production of goods and services. In the scope of industrialization, automation is a step beyond mechanization. Whereas mechanization provides human operators with machinery to assist them with the muscular requirements of work, automation greatly decreases the need for human sensory and mental requirements as well. Automation plays an increasingly important role in the world economy and in daily experience.

Automata

An automaton (plural: automata or automatons) is a self-operating machine. The word is sometimes used to describe a robot, more specifically an autonomous robot.

Types

The mechanical advantage of a simple machine is the ratio between the force it exerts on the load and the input force applied. This does not entirely describe the machine's performance, as force is required to overcome friction as well. The mechanical efficiency of a machine is the ratio of the actual mechanical advantage (AMA) to the ideal mechanical advantage (IMA). Functioning physical machines are always less than 100 percent efficient.

Mechanical

The word mechanical refers to the work that has been produced by machines or the machinery. It mostly relates to the machinery tools and the mechanical applications of science. Some of its synonyms are automatic and mechanic.

Simple machines

The idea that a machine can be broken down into simple movable elements led Archimedes to define the lever, pulley and screw as simple machines. By the time of the Renaissance this list increased to include the wheel and axle, wedge and inclined plane.

Engines

Main article: engine

An engine or motor is a machine designed to convert energy into useful mechanical motion. Heat engines, including internal combustion engines and external combustion engines (such as steam engines) burn a fuel to create heat, which is then used to create motion. Electric motors convert electrical energy into mechanical motion, pneumatic motors use compressed air and others, such as wind-up toys use elastic energy. In biological systems, molecular motors like myosins in muscles use chemical energy to create motion.

Electrical

Electrical means operating by or producing electricity, relating to or concerned with electricity. In other words, it means using, providing, producing, transmitting or operated by electricity.

Electrical machine

An electrical machine is the generic name for a device that converts mechanical energy to electrical energy, converts electrical energy to mechanical energy, or changes alternating current from one voltage level to a different voltage level.

Electronic machine

Main article: Electronics

Electronics is the branch of physics, engineering and technology dealing with electrical circuits that involve active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies. The nonlinear behavior of active components and their ability to control electron flows makes amplification of weak signals possible and is usually applied to information and signal processing. Similarly, the ability of electronic devices to act as switches makes digital information processing possible. Interconnection technologies such as circuit boards, electronic packaging technology, and other varied forms of communication infrastructure complete circuit functionality and transform the mixed components into a working system.

Computing machines

Main article: Computer

Computers are machines to process information, often in the form of numbers. Charles Babbage designed various machines to tabulate logarithms and other functions in 1837. His Difference engine can be considered an advanced mechanical calculator and his Analytical Engine a forerunner of the modern computer, though none were built in Babbage's lifetime.

Modern computers are electronic ones. They use electric charge, current or magnetization to store and manipulate information. Computer architecture deals with detailed design of computers. There are also simplified models of computers, like State machine and Turing machine.

Molecular machines

Study of the molecules and proteins that are the basis of biological functions has led to the concept of a molecular machine. For example, current models of the operation of the kinesin molecule that transports vesicles inside the cell as well as the myosin molecule that operates against actin to cause muscle contraction; these molecules control movement in response to chemical stimuli.

Researchers in nano-technology are working to construct molecules that perform movement in response to a specific stimulus. In contrast to molecules such as kinesin and myosin, these nanomachines or molecular machines are constructions like traditional machines that are designed to perform in a task.

Types of machines and related components
Classification Machine(s)
Simple machines Inclined plane, Wheel and axle, Lever, Pulley, Wedge, Screw
Mechanical components Axle, Bearings, Belts, Bucket, Fastener, Gear, Key, Link chains, Rack and pinion, Roller chains, Rope, Seals, Spring, Wheel
Clock Atomic clock, Watch, Pendulum clock, Quartz clock
Compressors and Pumps Archimedes' screw, Eductor-jet pump, Hydraulic ram, Pump, Trompe, Vacuum pump
Heat engines External combustion engines Steam engine, Stirling engine
Internal combustion engines Reciprocating engine, Gas turbine
Heat pumps Absorption refrigerator, Thermoelectric refrigerator, Regenerative cooling
Linkages Pantograph, Cam, Peaucellier-Lipkin
Turbine Gas turbine, Jet engine, Steam turbine, Water turbine, Wind generator, Windmill
Aerofoil Sail, Wing, Rudder, Flap, Propeller
Information technology Computer, Calculator, Telecommunications networks
Electricity Vacuum tube, Transistor, Diode, Resistor, Capacitor, Inductor, Memristor, Semiconductor
Robots Actuator, Servo, Servomechanism, Stepper motor
Miscellaneous Vending machine, Wind tunnel, Check weighing machines, Riveting machines

Machine elements

Machines are assembled from standardized types of components. These elements consist of mechanisms that control movement in various ways such as gear trains, transistor switches, belt or chain drives, linkages, cam and follower systems, brakes and clutches, and structural components such as frame members and fasteners.

Modern machines include sensors, actuators and computer controllers. The shape, texture and color of covers provide a styling and operational interface between the mechanical components of a machine and its users.

Mechanisms

Assemblies within a machine that control movement are often called "mechanisms." Mechanisms are generally classified as gears and gear trains, cam and follower mechanisms, and linkages, though there are other special mechanisms such as clamping linkages, indexing mechanisms and friction devices such as brakes and clutches.

For more details on mechanical machines see Machine (mechanical) and Mechanical systems.

Controllers

Controllers combine sensors, logic, and actuators to maintain the performance of components of a machine. Perhaps the best known is the flyball governor for a steam engine. Examples of these devices range from a thermostat that as temperature rises opens a valve to cooling water to speed controllers such the cruise control system in an automobile. The programmable logic controller replaced relays and specialized control mechanisms with a programmable computer. Servo motors that accurately position a shaft in response to an electrical command are the actuators that make robotic systems possible.

References

  • Boothroyd, Geoffrey and Winston A. Knight. 2005. Fundamentals of Machining and Machine Tools, Third Edition (Mechanical Engineering (Marcell Dekker)). Boca Raton, FL: CRC. ISBN 1574446592
  • Myszka, David H. 1998. Machines and Mechanisms: Applied Kinematic Analysis. Upper Saddle River, NJ: Prentice Hall. ISBN 0135979153
  • Oberg, Erik, Franklin D. Jones, Holbrook L. Horton, and Henry H. Ryffel. 2000. Machinery's Handbook. New York, NY: Industrial Press Inc. ISBN 0831126353
  • Uicker, John, Gordon Pennock, and Joseph Shigley. Theory of Machines and Mechanisms. Oxford University Press, 2010. ISBN 978-0195371239
  • Usher, Abbott Payson. A History of Mechanical Inventions. Dover Publications, 2011. ISBN 978-0486255934


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