14739255 pakistan machine tool factory internship report

7/22/2019 14739255 Pakistan Machine Tool Factory Internship Report

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PakistanMachine ToolFactory (PMTF)Internship ReportPMTF has rich experience in Designing andManufacturing of precision engineering goods andits facilities include Designing, Machining,Forging, Heat Treatment, Assembly, Die Castingetc.

2

009

B.E Electronics

M. Yasir Jamil Khan

M. Raghib Malik

Indus Institute of Higher Educationwww.iihe.edu.pk


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In the name of Allah most

merciful, the benevolent


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Indus Institute of Higher Education

Internship report submitted in fulfillment of the requirements

for the degree ofEngineering as per the criteria forengineering program.

Venue:

Pakistan Machine Tool Factory (PMTF)

Subject or Topics Covered:

CNC (Computerized Numeric Control)

NC (Numeric Control)

PLC (Programmable Logic Control)

Pneumatic & Hydraulic Controls

Dated:12th April, 2009 to 25th April, 2009

Belongs to:

Mohammad Yasir Jamil KhanMohammad Raghib MalikB.E Electronics Vth Semester


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Forewords:

The purpose of this report is to explainwhat we did and learned during internshipperiod with the Pakistan Machine ToolFactory (PMTF). The report is also arequirement for the fulfillment of Indus

Institute and Pakistan Engineering Councilfor engineering program. The reportfocuses primarily on the electronicallycontrolled machines such as CNCMachines, NC Machines, PLC andPneumatic and Hydraulic based controls,working environment, successes and short

comings that the intern did encounterwhen handling various tasks assigned bythe engineers & supervisor.

The various parts of the report reflect theinterns shortcomings, successes,observations and comments, it would be

imperative to be an engineer. Thereforethe report gives a number of commentsand recommendations on the internshipprogram.It is hoped that this report would serve as


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Table of Contents

Introduction . 02

Forewords . 03

Introduction to PMTF. 05

Departments at PMTF. 06

Topics Covered

NC and CNC ..... 11

PLC (Programmable Logic Control).. 25

Hydraulic Systems... 33

Pneumatic Systems.. 36

Abstracts

40

A Short Introduction to PMTF:


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Pakistan Machine Tool Factory (Pvt) Ltd. (PMTF) is aprecision engineering goods manufacturing enterprise inPakistan, established in technical collaboration with M/s.Oerlikon Buhrle & Co. of Switzerland who are the world'srenowned manufacturers of Machine Tools. The factory cameinto regular production in 1971.

It is located Off National Highway, about 35 Km from KarachiCity near Landhi Industrial Estate and spread over an area of226 acres out of which 17 acres are occupied by works. Thefactory employs about 1900 engineers, technician, workersand other service staff. The layout of the factory is according

to the best European standards. This factory is a unit of StateEngineering Corporation of Pakistan and is engaged in theproduction of Machine Tools, Automotive Transmissions andAxles Components, Gears for Locomotives, Pressure Die Castparts and other products.

PMTF has rich experience in Designing and Manufacturing of

precision engineering goods and its facilities includeDesigning, Machining, Forging, Heat Treatment, Assembly, DieCasting etc.

PMTF is certified to ISO 9001.Quality Assurance System andhas excellent Quality Control and Testing facilities to meet theinternational quality requirement.


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Departments Introduction:

Design Centre Machining

Tool Room Material Testing Heat Treating Forging Machine Tool Rebuilding

Design Centre:

Computer Aided Design & Manufacturing (CAD/CAM) facilitiesare installed for Product Design and Tools/Jigs/Fixtures Designand CNC Shop in 1990. Engineering software from Computervision (USA) and Autodesk namely:

- CADDS 5- Design View- Personal Designer

- Personal Designer/Personal Machinist- Micro draft- Personal Data Extract- Mechanical Desktop power pack (with Auto Cad)

are used for design of products, tools, jigs, fixtures, cutters,forging & die casting dies, gears, equipments, mechanicaldevices.

Machining:The works facility consists of variety of conventional and CNCmachine tools capable of performing various machiningoperations such as turning, planning, milling, drilling, jigboring, thread grinding, deep hole drilling, gear hobbling,
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shaping and shaving, gear grinding, spiral bevel gear cutting,broaching to the close tolerances specified in the design. Themaximum machining capabilities are as follows:

Turning: Max. 1000 mm dia x 4000 mm length x 800 kgwt.

Shaping/Planning

: Max. 6000 mm length x 1500 mm width x 2000kg wt.

Boring/Drilling : Max. 600 mm dia/50 mm dia max.

Gear Cutting : 10 module x 700 mm dia max.

Grinding : Max. 400 mm dia x 2500 mm length x 500 kg wt.

Pressure DieCasting

: Max 650 ton locking force x 12 kg wt.

Besides above facilities special purpose machines areavailable for die-sinking, spark erosion, thread grinding, jigboring, spine rolling, vertical turning, copy milling for intricateprecision components.

Tool Room:

The factory has a fully equipped Tool Room facility capable ofmanufacturing jigs & fixtures, special tools like drills, gauges,cutters and holding devices, special high precision machinetools like jig boring, thread grinding, die sinking, relievinglathes, vertical copying lathes, precision milling machines andspecial purpose tool grinding of Swiss and German originsupplements the facility and ensures that all specificationsand tolerances essential for tool room accuracy is met. The

Tool Room is linked with Tool Design Section fully equippedwith computer Aided Design facilities and supported byMetrology section located in same area for precise calibrationand control of tool room products. All recommendedinternational standards are followed for toolings.


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Material Testing:a. Metallographic:Complete Evaluation of :Macro and Micro StructureNon - Metallic Inclusion & segregationCase Hardening and Case DepthPhoto Micrograph of StructureFailure Analysis

b. Mechanical Testing:Facilities to determine:

Mechanical PropertiesStress - Strain

Tensile and Compressive StrengthShear and Impact Testc. Chemical Testing:Complete Analysis of:Metals and Alloys

Ferrous and Non Ferrous ElementsPaints, Chemicals, Ores, Oils Greases etc

d. Non-Destructive Testing:Determination of:Internal Cracks by Ultrasonic TestingSurface Cracks by Magnaflux and Dye- Penetration

Heat Treatment:The Heat Treatment shop is the largest and the most wellequipped in the country. The equipment is of French, Germanand Italian origin.

The Facilities has :


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- For Carburizing and Case Hardening :Five Sealed Quench Furnaces

Three Gas Fired Pit-type Muffle FurnacesTwo Rotary Hearth Furnaces with Quenching PressElectrically Heated Tempering Furnace

For Induction Hardening:Three High Frequency and Medium Frequency Induction

Hardening Machines

For Surface Hardening:Flame Hardening Machine

For Hardening High Speed Steel:Salt Bath Furnaces

Hydraulic Presses, Shot Blasting Machines, Sand BlastingPlant are available for post-

heat treatment process.

Forging:

The Forging shop is equipped with two drop hammers of 3000kg and 1500 kg Pneumatic hammers of 600 kg and 300 kg,

Trimming press of 320 tons and 1000 tons, Friction ScrewPress of 480 tons, Heating of stock for forging is done in rotaryhearth furnace. Furnace car-bottom type is installed fornormalizing the forged components. Removal of scales is donein Tumbler & Table type shot blasting machines. The forgeshop is capable of production of forgings up to 20 kg and 200

mm in diameter.

Machine Rebuilding:Machine Rebuilding is a comparatively new technology in theindustrially developed countries. It should not be mixed withmachine tool repair and maintenance and overhaul. The main


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characteristic of Machine Rebuilding are:

- The rebuilt machine has same performance andaccuracy as a new machine.- The warranty period is same as for a new one.- Cost of Rebuilding is one-third of the price of new

equivalent machine.

PMTF hasestablished this machine rebuilding facility in1994 with the assistance of UNIDO experts from UK and sincethen has undertaken the rebuilding activity with targetedoutput set for 10 to 12 machines per annum.

Quality Control:

Inspection and Testing is carried out according to proceduresestablished for ISO 9001 Quality Assurance System. Theinspection activities are backed up with the facility forcalibration of measuring and testing devices.

PMTF Products range includes:

MACHINE TOOLS:1- Heavy duty & light duty Milling Machines(Horizontal,Universal & Vertical)2- Vertical Copying Milling & Boring Machines3- Turret Milling Machine4- Precision Centre Lathes5- Universal Radial Drilling Machine (Portable)

6- Pantograph Engraving Machine7- Special Purpose Machine Tools8- Manual Arbor PressTRANSMISSION:1- Gear and Shafts for Agriculture Tractors like MasseyFerguson (MF 240, MF 375),and Fiat
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(Fiat 480, Fiat 640).2- Traction Gears and Pinions for Locomotives3- Gears for various Industrial applications4- Components for Bedford Trucks & Buses etc.DIE CAST COMPONENTS:1- Aluminum Pressure Die Cast components for Honda

Motorcycle Model CD 70 & CG 125, and Suzuki Motorcycle;Model A80.2- Aluminum Pressure Die Cast components for DomesticAppliances3- Aluminum Pressure Die Cast components of Gas Meter forGas distribution industries.4- Aluminum Pressure Die Cast components for Suzuki CarModel SB 308

TEXTILE MACHINERY:1- Ring Spinning Frame Model FA 506MISCELLANEOUS:1- Gears for various Industrial Applications.2- Spares for various plants/machinery.3- Machines / Equipments as per customer's design /requirement.
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Topics Covered:

N C & CNC

Numerical control (NC) refers to the automation ofmachinetools that are operated by abstractly programmed commandsencoded on a storage medium, as opposed to manuallycontrolled via hand wheels or levers or mechanicallyautomated via cams alone. The first NC machines were builtin the 1940s and 50s, based on existing tools that weremodified with motors that moved the controls to follow pointsfed into the system on paper tape. These earlyservomechanisms were rapidly augmented with analog anddigital computers, creating the modern ComputerNumerical Controlled (CNC) machine tools that haverevolutionized the design process.

In modern CNC systems, end-to-end component design ishighly automated using CAD/CAM programs. The programsproduce a computer file that is interpreted to extract thecommands needed to operate a particular machine, and thenloaded into the CNC machines for production. Since anyparticular component might require the use of a number ofdifferent tools - drills, saws, etc. - modern machines oftencombine multiple tools into a single "cell". In other cases, a

number of different machines are used with an externalcontroller and human or robotic operators that move thecomponent from machine to machine. In either case thecomplex series of steps needed to produce any part is highlyautomated and produces a part that closely matches theoriginal CAD design.
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Earlier forms of automation:Cams

The automation of machine tool control began in the 1800swith cams that "played" a machine tool in the way that camshad long been playing musical boxes or operating elaborate

cuckoo clocks.Thomas Blanchard built his gun-stock-copyinglathes (1820s-30s), and the work of people such asChristopher Miner Spencer developed the turret lathe into thescrew machine (1870s). Cam-based automation had alreadyreached a highly advanced state by World War I (1910s).However, automation via cams is fundamentally different fromnumerical control because it cannot be abstractlyprogrammed. There is no direct connection between the

design being produced and the machining steps needed tocreate it. Cams can encode information, but getting theinformation from the abstract level of an engineering drawinginto the cam is a manual process that requires sculptingand/or machining and filing. At least two forms of abstractlyprogrammable control had existed during the 1800s: those oftheJacquard loom and ofmechanical computers pioneered byCharles Babbage and others. These developments had the

potential for convergence with the automation of machine toocontrol starting in that century, but the convergence did nothappen until many decades later.

Tracer control:The application ofhydraulics to cam-based automationresulted in tracing machines that used a stylus to trace atemplate, such as the enormous Pratt & Whitney"Keller

Machine", which could copy templates several feet across.[1]

Another approach was "record and playback", pioneered atGeneral Motors (GM) in the 1950s, which used a storagesystem to record the movements of a human machinist, andthen play them back on demand. Analogous systems arecommon even today, notably the "teaching lathe" which gives
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new machinists a hands-on feel for the process. None of thesewere numerically programmable, however, and required amaster machinist at some point in the process, because the"programming" was physical rather than numerical.

Servos and selsyns:

One barrier to complete automation was the requiredtolerances of the machining process, which are routinely onthe order of thousandths of an inch. Although it would berelatively easy to connect some sort of control to a storagedevice like punch cards, ensuring that the controls weremoved to the correct position with the required accuracy wasanother issue. The movement of the tool resulted in varyingforces on the controls that would mean a linear output would

not result in linear motion of the tool. The key development inthis area was the introduction of the servo, which producedhighly accurate measurement information. Attaching twoservos together produced a selsyns, where a remote servo'smotions was accurately matched by another. Using a varietyof mechanical or electrical systems, the output of the selsynscould be read to ensure proper movement had occurred.

The first serious suggestion that selsyns could be used formachining control was made by Ernst F. W. Alexanderson, aSwedish immigrant to the U.S. working at General Electric(GE). Alexanderson had worked on the problem of torqueamplification that allowed the small output of a mechanicalcomputer to drive very large motors, which GE used as part ofa larger gun laying system for US Navy ships. Like machining,gun lying requires very high accuracies, less than a degree,

and the motion of the gun turrets was non-linear. In November1931 Alexanderson suggested to the Industrial EngineeringDepartment that the same systems could be used to drive theinputs of machine tools, allowing it to follow the outline of atemplate without the strong physical contact needed byexisting tools like the Keller Machine. He stated that it was a
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"matter of straight engineering development." However, theconcept was ahead of its time from a business developmentperspective, and GE did not take the matter seriously untilyears later, when others had pioneered the field.

Parsons and the invention of NC:

The birth of NC is generally credited toJohn T. Parsons,amachinist and salesman at his father's machining company,Parsons Corp. In 1942 he was told that helicopters were goingto be the "next big thing" by the former head ofFord Trimotor

production, Bill Stout. He called Sikorsky Aircraft to inquireabout possible work, and soon got a contract to build thewooden stringers in the rotor blades. After setting upproduction at a disused furniture factory and ramping upproduction, one of the blades failed and it was traced to thespar. As at least some of the problem appeared to stem fromspot welding a metal collar on the stringer to the metal spar,so Parsons suggested a new method of attaching the stringers

to the spar using adhesives, never before tried on an aircraftdesign.

But that development led to Parsons to wondering about thepossibility of using stamped metal stringers instead of wood,which would be much easier to make and stronger too. Thestringers for the rotors were built to a design provided bySikorsky, which was sent to them as a series of 17 points

defining the outline. Parsons then had to "fill in" the dots witha French curve to generate an outline they could use as atemplate to build the jigs for the wooden versions. But how tomake a tool able to cut metal with that shape was a muchharder problem. Parsons went to visit Wright Field to see FrankStulen, who was the head of the Rotary Ring Branch at the
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Propeller lab. Stulen concluded that Parsons didn't really knowwhat he was talking about, and realizing this, Parsons hiredhim on the spot. Stulen started work on 1 April 1946 and hiredthree new engineers to join him.Stulen's brother worked at Curtis Wright Propeller, andmentioned that they were using punch card calculators for

engineering calculations. Stulen decided to adopt the idea torun stress calculations on the rotors, the first detailedautomated calculations on helicopter rotors. When Parsonssaw what Stulen was doing with the punch card machines, heasked him if they could be used to generate an outline with200 points instead of the 17 they were given, and offset eachpoint by the radius of the cutting tool on a mill. If you cut ateach of those points, it would produce a relatively accurate

cutout of the stringer even in hard steel, and it could easily befiled down to a smooth shape. The resulting tool would beuseful as a template for stamping metal stringers. Stulen hadno problem doing this, and used the points to make largetables of numbers that would be taken onto the machine floor.Here, one operator read the numbers off the charts to twoother operators, one each on the X and Y axis, and they wouldmove the cutting head to that point and make a cut. This was

called the "by-the-numbers method".At that point Parsons conceived of a fully automated tool. Withenough points no manual working would be needed at all, butwith manual operation the time saved by having the partmore closely match the outline was offset by the time neededto move the controls. If the machine's inputs were attacheddirectly to the card reader this delay, and any associatedmanual errors, would be removed and the number of points

could be dramatically increased. Such a machine couldrepeatedly punch out perfectly accurate templates oncommand. But at the time he had no funds to develop theseideas.When one of Parsons Salesmen was on a visit to Wright Field,he was told of the problems the newly-formed US Air Force
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was having with new jet designs. He asked if Parsons hadanything to help to them. Parsons showed Lockheed their ideaof an automated mill, but they were uninterested. They hadalready decided to use 5-axis template copiers to produce thestringers, cutting from a metal template, and had ordered theexpensive cutting machine already. But as Parsons noted:

Now just picture the situation for a minute. Lockheed hadcontracted to design a machine to make these wings. Thismachine had five axes of cutter movement, and each of thesewas tracer controlled using a template. Nobody was using mymethod of making templates, so just imagine what chancethey were going to have of making an accurate airfoil shapewith inaccurate templates.

Parsons worries soon came true, and in 1949 the Air Forcearranged funding for Parsons to build his machines on hisown. Early work with Snyder Machine & Tool Corp proved thatthe system of directly driving the controls from motors failedto have the accuracy needed to set the machine for aperfectly smooth cut. Since the mechanical controls did notrespond in a linear fashion, you couldn't simply drive it with a

certain amount of power, because the differing forces wouldmean the same amount of power would not always producethe same amount of motion in the controls. No matter howmany points you included, the outline would still be rough.

Enter MIT:

This was not an impossible problem to solve, but wouldrequire some sort of feedback system, like a selsyn, to directlymeasure how far the controls had actually turned. Faced withthe daunting task of building such a system, in the spring of1949 Parsons turned to the MIT Servomechanisms Laboratory,a world leader in mechanical computing and feedback
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systems. During the war the Lab had built a number ofcomplex motor-driven devices like the motorized gun turretsystems for the B-29 and the automatic tracking system forthe SCR-584 radar. They were naturally suited to building aprototype of Parsons' automated "by-the-numbers" machine.

The MIT team was led by William Pease assisted by JamesMcDonough. They quickly concluded that Parsons' designcould be greatly improved; if the machine did not simply cutatpoints A and B, but instead moved smoothly between thepoints, then not only would it make a perfectly smooth cut,but could do so with many fewer points - the mill could cutlines directly instead of having to define a large number ofcutting points to "simulate" it. A three-way agreement was

arranged between Parsons', MIT and the Air Force, and theproject officially ran from July 1949 to June 1950. The contractcalled for the construction of two "Card-a-matic MillingMachines, a prototype and a production system. Both to behanded to Parsons for attachment to one of their mills in orderto develop a deliverable system for cutting stringers.

Instead, in 1950 MIT bought a surplus Cincinnati Milling

Machine Company "Hydro-Tel" mill of their own and arrangeda new contract directly with the Air Force that froze Parsonsout of further development. Parsons would later comment thathe " never dreamed that anybody as reputable as MIT woulddeliberately go ahead and take over my project." In spite ofthe development being handed to MIT, Parsons filed for apatent on "Motor Controlled Apparatus for Positioning Machine

Tool" on 5 May 1952, sparking a filing by MIT for a "Numerical

Control Servo-System" on 14 August 1952. Parsons' receivedUS Patent 2,820,187 on 14 January 1958, and the companysold an exclusive license to Bendix. IBM, Fujitsu and GeneralElectric all took sub-licenses after having already starteddevelopment of their own devices.
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MIT's machine:

MIT fit gears to the various hand wheel inputs and drove them

with roller chains connected to motors, one for each of themachine's three axes (X, Y and depth). The associatedcontroller consisted of five refrigerator-sized cabinets that,together, were almost as large as the mill they wereconnected to. Three of the cabinets contained the motorcontrollers, one controller for each motor, the other two thedigital reading system.

Unlike Parsons' original punch card design, the MIT designused standard 7-track punch tape for input. Three of thetracks were used to control the different axes of the machine,while the other four encoded various control information. Thetape was read in a cabinet that also housed six relay-basedhardware registers, two for each axis. With every readoperation the previously read point was copied into the"starting point" register, and the newly read one into the

"ending point". The tape was read continually and the numberin the register increased until a "stop" instruction, four holesin a line, was encountered.

The final cabinet held a clock that sent pulses through theregisters, compared them, and generated output pulses thatinterpolated between the points. For instance, if the pointswere far apart the output would have pulses with every clock

cycle, whereas closely spaced points would only generatepulses after multiple clock cycles. The pulses are sent into asumming register in the motor controllers, counting up by thenumber of pulses every time they were received. Thesumming registers were connected to a digital to analog
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convertor that output increasing power to the motors as thecount in the registers increased.

The registers were decremented by encoders attached to themotors and the mill itself, which would reduce the count byone for every one degree of rotation. Once the second pointwas reached the pulses from the clock would stop, and the

motors would eventually drive the mill to the encodedposition. Each 1 degree rotation of the controls produced a0.0005 inch movement of the cutting head.. The programmercould control the speed of the cut by selecting points thatwere closer together for slow movements, or further apart forrapid ones.

The system was publicly demonstrated in September 1952,appearing in that month's Scientific American. MIT's system

was an outstanding success by any technical measure, quicklymaking any complex cut with extremely high accuracy thatcould not easily be duplicated by hand. However, the systemwas terribly complex, including 250 vacuum tubes, 175 relaysand numerous moving parts, reducing its reliability in aproduction setting. It was also very expensive, the total billpresented to the Air Force was $360,000.14, $2,641,727.63 in2005 dollars. Between 1952 and 1956 the system was used to

mill a number of one-off designs for various aviation firms, inorder to study their potential economic impact.

Proliferation of NC:

The Air Force funding for the project ran out in 1953, butdevelopment was picked up by the Giddings and Lewis

Machine Tool Co. In 1955 many of the MIT team left to formConcord Controls, a commercial NC company with Giddings'backing, producing the Numericord controller. Numericord wassimilar to the MIT design, but replaced the punch tape with amagnetic tape reader that General Electric was working on.

The tape contained a number of signals of different phases,
http://en.wikipedia.org/wiki/Digital_to_analog_convertorhttp://en.wikipedia.org/wiki/Scientific_Americanhttp://en.wikipedia.org/wiki/Vacuum_tubehttp://en.wikipedia.org/w/index.php?title=Numericord&action=edit&redlink=1http://en.wikipedia.org/wiki/Magnetic_tapehttp://en.wikipedia.org/wiki/General_Electrichttp://en.wikipedia.org/wiki/Digital_to_analog_convertorhttp://en.wikipedia.org/wiki/Scientific_Americanhttp://en.wikipedia.org/wiki/Vacuum_tubehttp://en.wikipedia.org/w/index.php?title=Numericord&action=edit&redlink=1http://en.wikipedia.org/wiki/Magnetic_tapehttp://en.wikipedia.org/wiki/General_Electric


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which directly encoded the angle of the various controls. Thetape was played at a constant speed in the controller, whichset its half of the selsyns to the encoded angles while theremote side was attached to the machine controls. Designswere still encoded on paper tape, but the tapes weretransferred to a reader/writer that converted them into

magnetic form. The magtapes could then be used on any ofthe machines on the floor, where the controllers were greatlyreduced in complexity. Developed to produce highly accuratedies for an aircraft skinning press, the Numericord "NC5" wentinto operation at G&L's plant at Fond du Lac, WI in 1955.Monarch Machine Tool also developed an NC-controlled lathe,starting in 1952. They demonstrated their machine at the1955 Chicago Machine Tool Show, along with a number of

other vendors with punch card or paper tape machines thatwere either fully developed or in prototype form. Theseincluded Kearney & Trekkers Milwaukee-Matic II that couldchange its cutting tool under NC control.A Boeing report noted that "numerical control has proved itcan reduce costs, reduce lead times, improve quality, reducetooling and increase productivity. In spite of these

developments, and glowing reviews from the few users,uptake of NC was relatively slow. As Parsons later noted:

The NC concept was so strange to manufacturers, and so slowto catch on, that the US Army itself finally had to build 120 NCmachines and lease them to various manufacturers to beginpopularizing its use.In 1958 the MIT published its report on the economics of NC.

They concluded that the tools were competitive with humanoperators, but simply moved the time from the machining tothe creation of the tapes. In Forces of production Noble claimsthat this was the whole point as far as the Air Force wasconcerned; moving the process off of the highly unionized
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factory floor and into the un-unionized white collar designoffice.

CNC arrives:

Many of the commands for the experimental parts wereprogrammed "by hand" to produce the punch tapes that wereused as input. While the system was being experimentedwith, John Runyon made a number of subroutines on thefamous Whirlwind to produce these tapes under computercontrol. Users could input a list of points and speeds, and theprogram would generate the punch tape. In one instance, thisprocess reduced the time required to produce the instruction

list and mill the part from 8 hours to 15 minutes. This led to aproposal to the Air Force to produce a generalized"programming" language for numerical control, which wasaccepted in June 1956.Starting in September Ross and Pople outlined a language formachine control that was based on points and lines,developing this over several years into the APT programminglanguage. In 1957 the Aircraft Industries Association (AIA) and

Air Material Command at the Wright-Patterson Air Force Basejoined with MIT to standardize this work and produce a fullycomputer-controlled NC system. On 25 February 1959 thecombined team held a press conference showing the results,including a 3D machined aluminum ash tray that was handedout in the press kit.Meanwhile, Patrick Han ratty was making similardevelopments at GE as part of their partnership with G&L on

the Numericord. His language, PRONTO, beat APT intocommercial use when it was "released" in 1958. Han rattythen went on to develop MICR magnetic ink characters thatwere used in cherub processing, before moving to GeneralMotors to work on the groundbreaking DAC-1 CAD system.
http://en.wikipedia.org/wiki/White_collarhttp://en.wikipedia.org/wiki/Punch_tapehttp://en.wikipedia.org/wiki/Whirlwind_(computer)http://en.wikipedia.org/wiki/APT_programming_languagehttp://en.wikipedia.org/wiki/APT_programming_languagehttp://en.wikipedia.org/wiki/Aerospace_Industries_Associationhttp://en.wikipedia.org/wiki/Air_Material_Commandhttp://en.wikipedia.org/wiki/Wright-Patterson_Air_Force_Basehttp://en.wikipedia.org/wiki/Press_kithttp://en.wikipedia.org/w/index.php?title=Patrick_Hanratty&action=edit&redlink=1http://en.wikipedia.org/wiki/MICRhttp://en.wikipedia.org/wiki/General_Motorshttp://en.wikipedia.org/wiki/General_Motorshttp://en.wikipedia.org/wiki/DAC-1http://en.wikipedia.org/wiki/White_collarhttp://en.wikipedia.org/wiki/Punch_tapehttp://en.wikipedia.org/wiki/Whirlwind_(computer)http://en.wikipedia.org/wiki/APT_programming_languagehttp://en.wikipedia.org/wiki/APT_programming_languagehttp://en.wikipedia.org/wiki/Aerospace_Industries_Associationhttp://en.wikipedia.org/wiki/Air_Material_Commandhttp://en.wikipedia.org/wiki/Wright-Patterson_Air_Force_Basehttp://en.wikipedia.org/wiki/Press_kithttp://en.wikipedia.org/w/index.php?title=Patrick_Hanratty&action=edit&redlink=1http://en.wikipedia.org/wiki/MICRhttp://en.wikipedia.org/wiki/General_Motorshttp://en.wikipedia.org/wiki/General_Motorshttp://en.wikipedia.org/wiki/DAC-1


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APT was soon extended to include "real" curves in 2D-APT-II.With its release, MIT reduced its focus on CNC as it moved intoCAD experiments. APT development was picked up with theAIA in San Diego, and in 1962, to Illinois Institute of

Technology Research. Work on making APT an internationalstandard started in 1963 under USASI X3.4.7, but many

manufacturers of CNC machines had their own one-offadditions (like PRONTO), so standardization was notcompleted until 1968, when there were 25 optional add-ins tothe basic system.

Just as APT was being released in the early 1960s, a secondgeneration of lower-cost transistorized computers was hittingthe market that were able to process much larger volumes ofinformation in production settings. This so lowered the cost of

implementing a NC system that by the mid 1960s, APT runsaccounted for a third of all computer time at large aviationfirms.

CAD meets CNC:

While the Servomechanisms Lab was in the process of

developing their first mill, in 1953 MIT's MechanicalEngineering Department dropped the requirement thatundergraduates take courses in drawing. The instructorsformerly teaching these programs were merged into theDesign Division, where an informal discussion of computerizeddesign started. Meanwhile the Electronic Systems Laboratory,the newly rechristened Servomechanisms Laboratory, hadbeen discussing whether or not design would ever start with

paper diagrams in the future.In January 1959, an informal meeting was held involvingindividuals from both the Electronic Systems Laboratory andthe Mechanical Engineering Department's Design Division.Formal meetings followed in April and and May, which resultedin the "Computer-Aided Design Project". In December 1959,


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the Air Force issued a one year contract to ESL for $223,000to fund the Project, including $20,800 earmarked for 104hours of computer time at $200 per hour. This proved to befar too little for the ambitious program they had in mind,although their engineering calculation system, AED, wasreleased in March 1965.

In 1959 General Motors started an experimental project todigitize, store and print the many design sketches beinggenerated in the various GM design departments. When thebasic concept demonstrated that it could work, they startedthe DAC-1 project with IBM to develop a production version.One part of the DAC project was the direct conversion ofpaper diagrams into 3D models, which were then convertedinto APT commands and cut on milling machines. In

November 1963 a trunk lid design moved from 2D papersketch to 3D clay prototype for the first time. With theexception of the initial sketch, the design-to-production loophad been closed.Meanwhile MIT's offsite Lincoln Labs was building computersto test new transistorized designs. The ultimate goal wasessentially a transistorized Whirlwind known asTX-2, but inorder to test various circuit designs a smaller version known

asTX-0 was built first. When construction of TX-2 started, timein TX-0 freed up and this led to a number of experimentsinvolving interactive input and use of the machine's CRTdisplay for graphics. Further development of these conceptsled to Ivan Sutherland's groundbreaking Sketchpad programon the TX-2.Sutherland moved to the University of Utah after hisSketchpad work, but it inspired other MIT graduates to

attempt the first true CAD system, Electronic Drafting Machine(EDM). It was EDM, sold to Control Data and known as"Digigraphics", that Lockheed used to build production partsfor the C-5 Galaxy, the first example of an end-to-endCAD/CNC production system.
http://en.wikipedia.org/w/index.php?title=Automated_Engineering_Design&action=edit&redlink=1http://en.wikipedia.org/wiki/DAC-1http://en.wikipedia.org/wiki/IBMhttp://en.wikipedia.org/wiki/Lincoln_Labshttp://en.wikipedia.org/wiki/TX-2http://en.wikipedia.org/wiki/TX-0http://en.wikipedia.org/wiki/TX-0http://en.wikipedia.org/wiki/TX-0http://en.wikipedia.org/wiki/Cathode_ray_tubehttp://en.wikipedia.org/wiki/Ivan_Sutherlandhttp://en.wikipedia.org/wiki/Sketchpadhttp://en.wikipedia.org/wiki/University_of_Utahhttp://en.wikipedia.org/wiki/Digigraphicshttp://en.wikipedia.org/wiki/Control_Datahttp://en.wikipedia.org/wiki/Lockheedhttp://en.wikipedia.org/wiki/C-5_Galaxyhttp://en.wikipedia.org/w/index.php?title=Automated_Engineering_Design&action=edit&redlink=1http://en.wikipedia.org/wiki/DAC-1http://en.wikipedia.org/wiki/IBMhttp://en.wikipedia.org/wiki/Lincoln_Labshttp://en.wikipedia.org/wiki/TX-2http://en.wikipedia.org/wiki/TX-0http://en.wikipedia.org/wiki/Cathode_ray_tubehttp://en.wikipedia.org/wiki/Ivan_Sutherlandhttp://en.wikipedia.org/wiki/Sketchpadhttp://en.wikipedia.org/wiki/University_of_Utahhttp://en.wikipedia.org/wiki/Digigraphicshttp://en.wikipedia.org/wiki/Control_Datahttp://en.wikipedia.org/wiki/Lockheedhttp://en.wikipedia.org/wiki/C-5_Galaxy


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By 1970 there were a wide variety of CAD firms includingIntergraph, Applicon, Computer vision, Auto-troll Technology,UGS Corp. and others, as well as large vendors like CDC andIBM.

Proliferation of CNC

The price of computer cycles fell drastically during the 1960swith the widespread introduction of useful minicomputers.Eventually it became less expensive to handle the motorcontrol and feedback with a computer program than it was

with dedicated servo systems. Small computers werededicated to a single mill, placing the entire process in a smallbox. PDP-8's and Data General Nova computers were commonin these roles. The introduction of the microprocessor in the1970s further reduced the cost of implementation, and todayalmost all CNC machines use some form of microprocessor tohandle all operations.

The introduction of lower-cost CNC machines radically

changed the manufacturing industry. Curves are as easy tocut as straight lines, complex 3-D structures are relativelyeasy to produce, and the number of machining steps thatrequired human action have been dramatically reduced. Withthe increased automation of manufacturing processes withCNC machining, considerable improvements in consistencyand quality have been achieved with no strain on theoperator. CNC automation reduced the frequency of errors and

provided CNC operators with time to perform additional tasks.CNC automation also allows for more flexibility in the wayparts are held in the manufacturing process and the timerequired to change the machine to produce differentcomponents.
http://en.wikipedia.org/wiki/Intergraphhttp://en.wikipedia.org/wiki/Appliconhttp://en.wikipedia.org/wiki/Computervisionhttp://en.wikipedia.org/w/index.php?title=Auto-trol_Technology&action=edit&redlink=1http://en.wikipedia.org/wiki/UGS_Corp.http://en.wikipedia.org/wiki/Minicomputerhttp://en.wikipedia.org/wiki/PDP-8http://en.wikipedia.org/wiki/Data_General_Novahttp://en.wikipedia.org/wiki/Microprocessorhttp://en.wikipedia.org/wiki/Intergraphhttp://en.wikipedia.org/wiki/Appliconhttp://en.wikipedia.org/wiki/Computervisionhttp://en.wikipedia.org/w/index.php?title=Auto-trol_Technology&action=edit&redlink=1http://en.wikipedia.org/wiki/UGS_Corp.http://en.wikipedia.org/wiki/Minicomputerhttp://en.wikipedia.org/wiki/PDP-8http://en.wikipedia.org/wiki/Data_General_Novahttp://en.wikipedia.org/wiki/Microprocessor


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During the early 1970s the Western economies were mired inslow economic growth and rising employment costs, and NCmachines started to become more attractive. The major U.S.vendors were slow to respond to the demand for machinessuitable for lower-cost NC systems, and into this void steppedthe Germans. In 1979, sales of German machines surpassed

the U.S. designs for the first time. This cycle quickly repeateditself, and by 1980 Japan had taken a leadership position, U.S.sales dropping all the time. Once sitting in the #1 position interms of sales on a top-ten chart consisting entirely of U.S.companies in 1971, by 1987 Cincinnati Milacron was in 8thplace on a chart heavily dominated by Japanese firms.Many researchers have commented that the U.S. focus onhigh-end applications left them in an uncompetitive situation

when the economic downturn in the early 1970s led to greatlyincreased demand for low-cost NC systems. Unlike the U.S.companies, who had focused on the highly profitableaerospace market, German and Japanese manufacturerstargeted lower-profit segments from the start and were ableto enter the low-cost markets much more easily.

Today

Although modern data storage techniques have moved onfrom punch tape in almost every other role, tapes are stillrelatively common in CNC systems. This is because it wasoften easier to add a punch tape reader to a microprocessorcontroller than it was to re-write large libraries of tapes into anew format. One change that was implemented fairly widely

was the switch from paper to mylar tapes, which are muchmore mechanically robust. Floppy disks, USB flash drives andlocal area networking have replaced the tapes to somedegree, especially in larger environments that are highlyintegrated.
http://en.wikipedia.org/wiki/Mylarhttp://en.wikipedia.org/wiki/Floppy_diskhttp://en.wikipedia.org/wiki/USB_flash_drivehttp://en.wikipedia.org/wiki/Local_area_networkhttp://en.wikipedia.org/wiki/Mylarhttp://en.wikipedia.org/wiki/Floppy_diskhttp://en.wikipedia.org/wiki/USB_flash_drivehttp://en.wikipedia.org/wiki/Local_area_network


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The proliferation of CNC led to the need for new CNCstandards that were not encumbered by licensing or particulardesign concepts, like APT. A number of different "standards"proliferated for a time, often based around vector graphicsmarkup languages supported by plotters. One such standardhas since become very common, the "G-code" that was

originally used on Gerber Scientific plotters and then adaptedfor CNC use. The file format became so widely used that it hasbeen embodied in an EIA standard. In turn, G-code wassupplanted by STEP-NC, a system that was deliberatelydesigned for CNC, rather than grown from an existing plotterstandard.A more recent advancement in CNC interpreters is support oflogical commands, known as parametric programming.

Parametric programs include both device commands as wellas a control language similar to BASIC. The programmer canmake if/then/else statements, loops, subprogram calls,perform various arithmetic, and manipulate variables tocreate a large degree of freedom within one program. Anentire product line of different sizes can be programmed usinglogic and simple math to create and scale an entire range ofparts, or create a stock part that can be scaled to any size a

customer demands.As digital electronics has spread, CNC has fallen in price to thepoint where hobbyists can purchase any number of small CNCsystems for home use. It is even possible to build your own.

Description:

Modern CNC mills differ little in concept from the originalmodel built at MIT in 1952. Mills typically consist of a tablethat moves in the Y axis, and a tool chuck that moves in X andZ (depth). The position of the tool is driven by motors througha series of step-down gears in order to provide highly accurate
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movements, or in modern designs, direct-drive steppermotors.As the controller hardware evolved, the mills themselves alsoevolved. One change has been to enclose the entiremechanism in a large box as a safety measure, often withadditional safety interlocks to ensure the operator is far

enough from the working piece for safe operation. Mechanicalmanual controls disappeared long ago.CNC-like systems are now used for any process that can bedescribed as a series of movements and operations. Theseinclude laser cutting, welding, friction stir welding, ultrasonicwelding, flame and plasma cutting, bending, spinning,pinning, gluing, fabric cutting, sewing, tape and fiberplacement, routing, picking and placing (PnP), and sawing.

Programmable logic controller

A programmable logic controller (PLC) or programmablecontroller is a digital computer used for automation ofelectromechanical processes, such as control of machinery onfactory assembly lines, amusement rides, or lighting fixtures.PLCs are used in many industries and machines, such aspackaging and semiconductor machines. Unlike general-purpose computers, the PLC is designed for multiple inputsand output arrangements, extended temperature ranges,immunity to electrical noise, and resistance to vibration and

impact. Programs to control machine operation are typicallystored in battery-backed or non-volatile memory. A PLC is anexample of a real time system since output results must beproduced in response to input conditions within a boundedtime, otherwise unintended operation will result.
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Features:

The main difference from other computers is that PLCs arearmored for severe conditions (such as dust, moisture, heat,cold) and have the facility for extensive input/output (I/O)

arrangements. These connect the PLC to sensors andactuators. PLCs read limit switches, analog process variables(such as temperature and pressure), and the positions ofcomplex positioning systems. Some use machine vision. Onthe actuator side, PLCs operate electric motors, pneumatic orhydraulic cylinders, magnetic relays, solenoids, or analogoutputs. The input/output arrangements may be built into asimple PLC, or the PLC may have external I/O modules

attached to a computer network that plugs into the PLC.

System scale:

A small PLC will have a fixed number of connections built in

for inputs and outputs. Typically, expansions are available ifthe base model has insufficient I/O.Modular PLCs have a chassis (also called a rack) into whichare placed modules with different functions. The processorand selection of I/O modules is customized for the particularapplication. Several racks can be administered by a singleprocessor, and may have thousands of inputs and outputs. Aspecial high speed serial I/O link is used so that racks can bedistributed away from the processor, reducing the wiring costsfor large plants.

User interface:
http://en.wikipedia.org/wiki/Input/outputhttp://en.wikipedia.org/wiki/Sensorhttp://en.wikipedia.org/wiki/Actuatorhttp://en.wikipedia.org/wiki/Switchhttp://en.wikipedia.org/wiki/Machine_visionhttp://en.wikipedia.org/wiki/Electric_motorhttp://en.wikipedia.org/wiki/Pneumatichttp://en.wikipedia.org/wiki/Hydraulichttp://en.wikipedia.org/wiki/Relayhttp://en.wikipedia.org/wiki/Solenoidhttp://en.wikipedia.org/wiki/Input/outputhttp://en.wikipedia.org/wiki/Sensorhttp://en.wikipedia.org/wiki/Actuatorhttp://en.wikipedia.org/wiki/Switchhttp://en.wikipedia.org/wiki/Machine_visionhttp://en.wikipedia.org/wiki/Electric_motorhttp://en.wikipedia.org/wiki/Pneumatichttp://en.wikipedia.org/wiki/Hydraulichttp://en.wikipedia.org/wiki/Relayhttp://en.wikipedia.org/wiki/Solenoid


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PLCs may need to interact with people for the purpose ofconfiguration, alarm reporting or everyday control.A Human-Machine Interface (HMI) is employed for thispurpose. HMIs are also referred to as MMIs (Man MachineInterface) and GUI (Graphical User Interface).A simple system may use buttons and lights to interact with

the user. Text displays are available as well as graphical touchscreens. More complex systems use a programming andmonitoring software installed on a computer, with the PLCconnected via a communication interface.

Communications:

PLCs have built in communications ports usually 9-Pin RS232,

and optionally for RS485 and Ethernet. Modbus or DF1 isusually included as one of the communications protocols.Others' options include various fieldbuses such as DeviceNetor Profibus. Other communications protocols that may be usedare listed in the List of automation protocols.Most modern PLCs can communicate over a network to someother system, such as a computer running a SCADA(Supervisory Control And Data Acquisition) system or web

browser.PLCs used in larger I/O systems may have peer-to-peer (P2P)communication between processors. This allows separateparts of a complex process to have individual control whileallowing the subsystems to co-ordinate over thecommunication link. These communication links are also oftenused for HMI devices such as keypads or PC-typeworkstations. Some of today's PLCs can communicate over a

wide range of media including RS-485, Coaxial, and evenEthernet for I/O control at network speeds up to 100 Mbit/s.
http://en.wikipedia.org/wiki/User_interfacehttp://en.wikipedia.org/wiki/RS232http://en.wikipedia.org/wiki/RS485http://en.wikipedia.org/wiki/Ethernethttp://en.wikipedia.org/wiki/Modbushttp://en.wikipedia.org/w/index.php?title=DF1&action=edit&redlink=1http://en.wikipedia.org/wiki/Communications_protocolshttp://en.wikipedia.org/wiki/Fieldbushttp://en.wikipedia.org/wiki/DeviceNethttp://en.wikipedia.org/wiki/Profibushttp://en.wikipedia.org/wiki/List_of_automation_protocolshttp://en.wikipedia.org/wiki/SCADAhttp://en.wikipedia.org/wiki/User_interfacehttp://en.wikipedia.org/wiki/Personal_computerhttp://en.wikipedia.org/wiki/Ethernethttp://en.wikipedia.org/wiki/User_interfacehttp://en.wikipedia.org/wiki/RS232http://en.wikipedia.org/wiki/RS485http://en.wikipedia.org/wiki/Ethernethttp://en.wikipedia.org/wiki/Modbushttp://en.wikipedia.org/w/index.php?title=DF1&action=edit&redlink=1http://en.wikipedia.org/wiki/Communications_protocolshttp://en.wikipedia.org/wiki/Fieldbushttp://en.wikipedia.org/wiki/DeviceNethttp://en.wikipedia.org/wiki/Profibushttp://en.wikipedia.org/wiki/List_of_automation_protocolshttp://en.wikipedia.org/wiki/SCADAhttp://en.wikipedia.org/wiki/User_interfacehttp://en.wikipedia.org/wiki/Personal_computerhttp://en.wikipedia.org/wiki/Ethernet


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PLC compared with other control systems:

PLCs are well-adapted to a range ofautomation tasks. Theseare typically industrial processes in manufacturing where thecost of developing and maintaining the automation system ishigh relative to the total cost of the automation, and where

changes to the system would be expected during itsoperational life. PLCs contain input and output devicescompatible with industrial pilot devices and controls; littleelectrical design is required, and the design problem centerson expressing the desired sequence of operations in ladderlogic (or function chart) notation. PLC applications aretypically highly customized systems so the cost of a packagedPLC is low compared to the cost of a specific custom-built

controller design. On the other hand, in the case of mass-produced goods, customized control systems are economicdue to the lower cost of the components, which can beoptimally chosen instead of a "generic" solution, and wherethe non-recurring engineering charges are spread overthousands or millions of units.For high volume or very simple fixed automation tasks,different techniques are used. For example, a consumer

dishwasher would be controlled by an electromechanical camtimer costing only a few dollars in production quantities.A microcontroller-based design would be appropriate wherehundreds or thousands of units will be produced and so thedevelopment cost (design of power supplies and input/outputhardware) can be spread over many sales, and where the end-user would not need to alter the control. Automotiveapplications are an example; millions of units are built each

year, and very few end-users alter the programming of thesecontrollers. However, some specialty vehicles such as transitbusses economically use PLCs instead of custom-designedcontrols, because the volumes are low and the developmentcost would be uneconomic.
http://en.wikipedia.org/wiki/Automationhttp://en.wikipedia.org/wiki/Ladder_logichttp://en.wikipedia.org/wiki/Ladder_logichttp://en.wikipedia.org/w/index.php?title=Function_chart&action=edit&redlink=1http://en.wikipedia.org/wiki/Dishwasherhttp://en.wikipedia.org/wiki/Cam_timerhttp://en.wikipedia.org/wiki/Cam_timerhttp://en.wikipedia.org/wiki/Microcontrollerhttp://en.wikipedia.org/wiki/Automationhttp://en.wikipedia.org/wiki/Ladder_logichttp://en.wikipedia.org/wiki/Ladder_logichttp://en.wikipedia.org/w/index.php?title=Function_chart&action=edit&redlink=1http://en.wikipedia.org/wiki/Dishwasherhttp://en.wikipedia.org/wiki/Cam_timerhttp://en.wikipedia.org/wiki/Cam_timerhttp://en.wikipedia.org/wiki/Microcontroller


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Very complex process control, such as used in the chemicalindustry, may require algorithms and performance beyond thecapability of even high-performance PLCs. Very high-speed orprecision controls may also require customized solutions; forexample, aircraft flight controls.Programmable controllers are widely used in motion control,

positioning control and torque control. Some manufacturersproduce motion control units to be integrated with PLC so thatG-code (involving a CNC machine) can be used to instructmachine movements.PLCs may include logic for single-variable feedback analogcontrol loop, a "proportional, integral, derivative" or "PIDcontroller." A PID loop could be used to control thetemperature of a manufacturing process, for example.

Historically PLCs were usually configured with only a fewanalog control loops; where processes required hundreds orthousands of loops, a distributed control system (DCS) wouldinstead be used. As PLCs have become more powerful, theboundary between DCS and PLC applications has become lessdistinct.PLCs have similar functionality as Remote Terminal Units. AnRTU, however, usually does not support control algorithms or

control loops. As hardware rapidly becomes more powerfuland cheaper, RTUs, PLCs and DCSs are increasingly beginningto overlap in responsibilities, and many vendors sell RTUs withPLC-like features and vice versa. The industry hasstandardized on the IEC 61131-3 functional block language forcreating programs to run on RTUs and PLCs, although nearlyall vendors also offer proprietary alternatives and associateddevelopment environments.

Digital and analog signals:

Digital or discrete signals behave as binary switches, yieldingsimply an On or Off signal (1 or 0, True or False, respectively).Push buttons, limit switches, and photoelectric sensors are
http://en.wikipedia.org/wiki/G-codehttp://en.wikipedia.org/wiki/CNChttp://en.wikipedia.org/wiki/PID_controllerhttp://en.wikipedia.org/wiki/PID_controllerhttp://en.wikipedia.org/wiki/Distributed_control_systemhttp://en.wikipedia.org/wiki/Remote_Terminal_Unithttp://en.wikipedia.org/wiki/Remote_Terminal_Unithttp://en.wikipedia.org/wiki/Distributed_Control_Systemhttp://en.wikipedia.org/wiki/Photoelectric_sensorhttp://en.wikipedia.org/wiki/G-codehttp://en.wikipedia.org/wiki/CNChttp://en.wikipedia.org/wiki/PID_controllerhttp://en.wikipedia.org/wiki/PID_controllerhttp://en.wikipedia.org/wiki/Distributed_control_systemhttp://en.wikipedia.org/wiki/Remote_Terminal_Unithttp://en.wikipedia.org/wiki/Remote_Terminal_Unithttp://en.wikipedia.org/wiki/Distributed_Control_Systemhttp://en.wikipedia.org/wiki/Photoelectric_sensor


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examples of devices providing a discrete signal. Discretesignals are sent using either voltage or current, where aspecific range is designated as On and another as Off. Forexample, a PLC might use 24 V DC I/O, with values above 22 VDC representing On, values below 2VDC representing Off, andintermediate values undefined. Initially, PLCs had only

discrete I/O.Analog signals are like volume controls, with a range of valuesbetween zero and full-scale. These are typically interpreted asinteger values (counts) by the PLC, with various ranges ofaccuracy depending on the device and the number of bitsavailable to store the data. As PLCs typically use 16-bit signedbinary processors, the integer values are limited between-32,768 and +32,767. Pressure, temperature, flow, and weight

are often represented by analog signals. Analog signals canuse voltage or current with a magnitude proportional to thevalue of the process signal. For example, an analog 4-20 mAor 0 - 10 V input would be converted into an integer value of 0- 32767.Current inputs are less sensitive to electrical noise (i.e. fromwelders or electric motor starts) than voltage inputs.

Example:

As an example, say a facility needs to store water in a tank. The wateris drawn from the tank by another system, as needed, and ourexample system must manage the water level in the tank.Using only digital signals, the PLC has two digital inputs from floatswitches (Low Level and High Level). When the water level is above theswitch it closes a contact and passes a signal to an input. The PLC usesa digital output to open and close the inlet valve into the tank.

When the water level drops enough so that the Low Level float switchis off (down), the PLC will open the valve to let more water in. Once thewater level rises enough so that the High Level switch is on (up), thePLC will shut the inlet to stop the water from overflowing. This rung isan example of seal in logic. The output is sealed in until some conditionbreaks the circuit.| |
http://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Current_(electricity)http://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Current_(electricity)http://en.wikipedia.org/wiki/4-20_mAhttp://en.wikipedia.org/wiki/Analog-to-digital_converterhttp://en.wikipedia.org/wiki/Current_loophttp://en.wikipedia.org/wiki/Float_switchhttp://en.wikipedia.org/wiki/Float_switchhttp://en.wikipedia.org/wiki/Valvehttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Current_(electricity)http://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Current_(electricity)http://en.wikipedia.org/wiki/4-20_mAhttp://en.wikipedia.org/wiki/Analog-to-digital_converterhttp://en.wikipedia.org/wiki/Current_loophttp://en.wikipedia.org/wiki/Float_switchhttp://en.wikipedia.org/wiki/Float_switchhttp://en.wikipedia.org/wiki/Valve


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| Low Level High Level Fill Valve |

|------[/]------|------[/]----------------------(OUT)---------|

| | |

| | |

| | |

| Fill Valve | |

|------[ ]------| |

| |

| |

An analog system might use a water pressure sensor or a loadcell, and an adjustable (throttling) dripping out of the tank,the valve adjusts to slowly drip water back into the tank.In this system, to avoid 'flutter' adjustments that can wear outthe valve, many PLCs incorporate "hysteresis" whichessentially creates a "deadband" of activity. A technicianadjusts this deadband so the valve moves only for asignificant change in rate. This will in turn minimize the

motion of the valve, and reduce its wear.A real system might combine both approaches, using floatswitches and simple valves to prevent spills, and a rate sensorand rate valve to optimize refill rates and prevent waterhammer. Backup and maintenance methods can make a realsystem very complicated.

Programming:

PLC programs are typically written in a special application ona personal computer, then downloaded by a direct-connectioncable or over a network to the PLC. The program is stored inthe PLC either in battery-backed-up RAM or some other non-volatile flash memory. Often, a single PLC can be programmedto replace thousands ofrelays.Under the IEC 61131-3 standard, PLCs can be programmed

using standards-based programming languages. A graphicalprogramming notation called Sequential Function Charts isavailable on certain programmable controllers.Recently, the International standard IEC 61131-3 has becomepopular. IEC 61131-3 currently defines five programminglanguages for programmable control systems: FBD (Function
http://en.wikipedia.org/wiki/Pressure_sensorhttp://en.wikipedia.org/wiki/Load_cellhttp://en.wikipedia.org/wiki/Load_cellhttp://en.wikipedia.org/wiki/Hysteresishttp://en.wikipedia.org/wiki/Deadbandhttp://en.wikipedia.org/wiki/Water_hammerhttp://en.wikipedia.org/wiki/Water_hammerhttp://en.wikipedia.org/wiki/RAMhttp://en.wikipedia.org/wiki/Flash_memoryhttp://en.wikipedia.org/wiki/Relayhttp://en.wikipedia.org/wiki/IEC_61131-3http://en.wikipedia.org/wiki/Sequential_function_charthttp://en.wikipedia.org/wiki/IEC_61131-3http://en.wikipedia.org/wiki/Function_block_diagramhttp://en.wikipedia.org/wiki/Pressure_sensorhttp://en.wikipedia.org/wiki/Load_cellhttp://en.wikipedia.org/wiki/Load_cellhttp://en.wikipedia.org/wiki/Hysteresishttp://en.wikipedia.org/wiki/Deadbandhttp://en.wikipedia.org/wiki/Water_hammerhttp://en.wikipedia.org/wiki/Water_hammerhttp://en.wikipedia.org/wiki/RAMhttp://en.wikipedia.org/wiki/Flash_memoryhttp://en.wikipedia.org/wiki/Relayhttp://en.wikipedia.org/wiki/IEC_61131-3http://en.wikipedia.org/wiki/Sequential_function_charthttp://en.wikipedia.org/wiki/IEC_61131-3http://en.wikipedia.org/wiki/Function_block_diagram


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block diagram), LD (Ladder diagram), ST (Structured text,similar to the Pascal programming language), IL (Instructionlist, similar to assembly language) and SFC (Sequentialfunction chart). These techniques emphasize logicalorganization of operations.While the fundamental concepts of PLC programming are

common to all manufacturers, differences in I/O addressing,memory organization and instruction sets mean that PLCprograms are never perfectly interchangeable betweendifferent makers. Even within the same product line of a singlemanufacturer, different models may not be directlycompatible.

History

Origin:

The PLC was invented in response to the needs of theAmerican automotive manufacturing industry. Programmablecontrollers were initially adopted by the automotive industrywhere software revision replaced the re-wiring of hard-wiredcontrol panels when production models changed.Before the PLC, control, sequencing, and safety interlock logicfor manufacturing automobiles was accomplished usinghundreds or thousands ofrelays, cam timers, and drumsequencers and dedicated closed-loop controllers. Theprocess for updating such facilities for the yearly modelchange-over was very time consuming and expensive, as therelay systems needed to be rewired by skilled electricians.In 1968 GM Hydramatic (the automatic transmission division

ofGeneral Motors) issued a request for proposal for anelectronic replacement for hard-wired relay systems.

The winning proposal came from Bedford Associates ofBedford, Massachusetts. The first PLC, designated the 084because it was Bedford Associates' eighty-fourth project, wasthe result. Bedford Associates started a new company
http://en.wikipedia.org/wiki/Function_block_diagramhttp://en.wikipedia.org/wiki/Ladder_logichttp://en.wikipedia.org/wiki/Structured_texthttp://en.wikipedia.org/wiki/Pascal_programming_languagehttp://en.wikipedia.org/wiki/Instruction_listhttp://en.wikipedia.org/wiki/Instruction_listhttp://en.wikipedia.org/wiki/Assembly_languagehttp://en.wikipedia.org/wiki/Sequential_function_charthttp://en.wikipedia.org/wiki/Sequential_function_charthttp://en.wikipedia.org/wiki/Relayhttp://en.wikipedia.org/wiki/Cam_timerhttp://en.wikipedia.org/w/index.php?title=Drum_sequencer&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Drum_sequencer&action=edit&redlink=1http://en.wikipedia.org/wiki/Changeoverhttp://en.wikipedia.org/wiki/General_Motorshttp://en.wikipedia.org/wiki/Bedford,_Massachusettshttp://en.wikipedia.org/wiki/Function_block_diagramhttp://en.wikipedia.org/wiki/Ladder_logichttp://en.wikipedia.org/wiki/Structured_texthttp://en.wikipedia.org/wiki/Pascal_programming_languagehttp://en.wikipedia.org/wiki/Instruction_listhttp://en.wikipedia.org/wiki/Instruction_listhttp://en.wikipedia.org/wiki/Assembly_languagehttp://en.wikipedia.org/wiki/Sequential_function_charthttp://en.wikipedia.org/wiki/Sequential_function_charthttp://en.wikipedia.org/wiki/Relayhttp://en.wikipedia.org/wiki/Cam_timerhttp://en.wikipedia.org/w/index.php?title=Drum_sequencer&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Drum_sequencer&action=edit&redlink=1http://en.wikipedia.org/wiki/Changeoverhttp://en.wikipedia.org/wiki/General_Motorshttp://en.wikipedia.org/wiki/Bedford,_Massachusetts


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dedicated to developing, manufacturing, selling, and servicingthis new product: Modicum, which stood for Modular DigitalController. One of the people who worked on that project wasDick Morley, who is considered to be the "father" of the PLC.

The Modicum brand was sold in 1977 to Gould Electronics,and later acquired by German Company AEG and then by

French Schneider Electric, the current owner.One of the very first 084 models built is now on display atModicums headquarters in North Andover, Massachusetts. Itwas presented to Modicum by GM, when the unit was retiredafter nearly twenty years of uninterrupted service. Modicumused the 84 moniker at the end of its product range until the984 made its appearance.

The automotive industry is still one of the largest users of

PLCs.

Development:

Early PLCs were designed to replace relay logic systems.These PLCs were programmed in "ladder logic", whichstrongly resembles a schematic diagram of relay logic.Modern PLCs can be programmed in a variety of ways, from

ladder logic to more traditional programming languages suchas BASIC and C. Another method is State Logic, a Very HighLevel Programming Language designed to program PLCsbased on State Transition Diagrams.Many of the earliest PLCs expressed all decision making logicin simple ladder logic which appeared similar to electricalschematic diagrams. This program notation was chosen toreduce training demands for the existing technicians. Other

early PLCs used a form ofinstruction list programming, basedon a stack-based logic solver.

Programming:
http://en.wikipedia.org/wiki/Dick_Morleyhttp://en.wikipedia.org/wiki/Gould_Electronicshttp://en.wikipedia.org/wiki/AEGhttp://en.wikipedia.org/wiki/Schneider_Electrichttp://en.wikipedia.org/wiki/North_Andover,_Massachusettshttp://en.wikipedia.org/wiki/General_Motorshttp://en.wikipedia.org/wiki/Ladder_logichttp://en.wikipedia.org/wiki/State_Logichttp://en.wikipedia.org/wiki/Very_High_Level_Programming_Languagehttp://en.wikipedia.org/wiki/Very_High_Level_Programming_Languagehttp://en.wikipedia.org/wiki/State_diagramhttp://en.wikipedia.org/wiki/Ladder_logichttp://en.wikipedia.org/wiki/Instruction_listhttp://en.wikipedia.org/wiki/Dick_Morleyhttp://en.wikipedia.org/wiki/Gould_Electronicshttp://en.wikipedia.org/wiki/AEGhttp://en.wikipedia.org/wiki/Schneider_Electrichttp://en.wikipedia.org/wiki/North_Andover,_Massachusettshttp://en.wikipedia.org/wiki/General_Motorshttp://en.wikipedia.org/wiki/Ladder_logichttp://en.wikipedia.org/wiki/State_Logichttp://en.wikipedia.org/wiki/Very_High_Level_Programming_Languagehttp://en.wikipedia.org/wiki/Very_High_Level_Programming_Languagehttp://en.wikipedia.org/wiki/State_diagramhttp://en.wikipedia.org/wiki/Ladder_logichttp://en.wikipedia.org/wiki/Instruction_list


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Early PLCs, up to the mid-1980s, were programmed usingproprietary programming panels or special-purposeprogramming terminals, which often had dedicated functionkeys representing the various logical elements of PLCprograms. Programs were stored on cassette tape cartridges.Facilities for printing and documentation were very minimal

due to lack of memory capacity. The very oldest PLCs usednon-volatile magnetic core memory.

Functionality:

The functionality of the PLC has evolved over the years toinclude sequential relay control, motion control, processcontrol, distributed control systems and networking. The datahandling, storage, processing power and communicationcapabilities of some modern PLCs are approximatelyequivalent to desktop computers. PLC-like programmingcombined with remote I/O hardware, allow a general-purposedesktop computer to overlap some PLCs in certainapplications.

Hydraulic drive system

A hydraulic or hydrostatic drive system or hydraulicpower transmission is a drive or transmission system thatuses hydraulic fluid under pressure to drive machinery. Theterm hydrostatic refers to the transfer of energy from flow andpressure, not from the kinetic energy of the flow. Such asystem basically consists of three parts. The generator (e.g. a
http://en.wikipedia.org/wiki/Computer_terminalhttp://en.wikipedia.org/wiki/Magnetic_core_memoryhttp://en.wikipedia.org/wiki/Process_controlhttp://en.wikipedia.org/wiki/Process_controlhttp://en.wikipedia.org/wiki/Distributed_control_systemhttp://en.wikipedia.org/wiki/Computer_networkhttp://en.wikipedia.org/wiki/Desktop_computerhttp://en.wikipedia.org/wiki/Kinetichttp://en.wikipedia.org/wiki/Computer_terminalhttp://en.wikipedia.org/wiki/Magnetic_core_memoryhttp://en.wikipedia.org/wiki/Process_controlhttp://en.wikipedia.org/wiki/Process_controlhttp://en.wikipedia.org/wiki/Distributed_control_systemhttp://en.wikipedia.org/wiki/Computer_networkhttp://en.wikipedia.org/wiki/Desktop_computerhttp://en.wikipedia.org/wiki/Kinetic


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hydraulic pump, driven by an electric motor, a combustionengine or a windmill); valves, filters, piping etc. (to guide andcontrol the system); the motor (e.g. a hydraulic motor orhydraulic cylinder) to drive the machinery.

Principle of a hydraulic drive:Pascal's law is the basis of hydraulicdrive systems. As the pressure in thesystem is the same, the force that thefluid gives to the surroundings istherefore equal to pressure x area. Insuch a way, a small piston feels asmall force and a large piston feels a

large force.The same counts for a hydraulic pumpwith a small swept volume, that asksfor a small torque, combined with ahydraulic motor with a large sweptvolume, that gives a large torque.In such a way a transmission with a certain ratio can be built.Most hydraulic drive systems make use of hydraulic cylinders.

Here the same principle is used- a small torque can betransmitted in to a large force.By throttling the fluid between generator part and motor part,or by using hydraulic pumps and/or motors with adjustableswept volume, the ratio of the transmission can be changedeasily. In case throttling is used, the efficiency of thetransmission is limited; in case adjustable pumps and motorsare used, the efficiency however is very

large. In fact, up to around 1980, ahydraulic drive system had hardly anycompetition from other adjustable(electric) drive systems.Nowadays electric drive systems usingelectric servo-motors can be controlled
http://en.wikipedia.org/wiki/Hydraulic_pumphttp://en.wikipedia.org/wiki/Electric_motorhttp://en.wikipedia.org/wiki/Enginehttp://en.wikipedia.org/wiki/Windmillhttp://en.wikipedia.org/wiki/Hydraulic_motorhttp://en.wikipedia.org/wiki/Hydraulic_cylinderhttp://en.wikipedia.org/wiki/Torquehttp://en.wikipedia.org/wiki/Hydraulic_pumphttp://en.wikipedia.org/wiki/Electric_motorhttp://en.wikipedia.org/wiki/Enginehttp://en.wikipedia.org/wiki/Windmillhttp://en.wikipedia.org/wiki/Hydraulic_motorhttp://en.wikipedia.org/wiki/Hydraulic_cylinderhttp://en.wikipedia.org/wiki/Torque


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in an excellent way and can easily compete with rotatinghydraulic drive systems. Hydraulic cylinders are in factwithout competition for linear (high) forces. For thesecylinders anyway hydraulic systems will remain of interestand if such a system is available, it is easy and logical to usethis system also for the rotating drives of the cooling systems.

Hydraulic cylinder:

Hydraulic cylinders (also called linear hydraulic motors) aremechanical actuators that are used to give a linear forcethrough a linear stroke. A hydraulic cylinder is without doubtthe best known hydraulic component. Hydraulic cylinders areable to give pushing and pulling forces of millions of metrictons, with only a simple hydraulic system. Very simplehydraulic cylinders are used in presses; here the cylinderconsists out of a volume in a piece of iron with a plungerpushed in it and sealed with a cover. By pumping hydraulicfluid in the volume, the plunger is pushed out with a force ofplunger-area * pressure.More sophisticated cylinders have a body with end cover, apiston-rod with piston and a cylinder-head. At one side the

bottom is for instance connected to a single clevis, whereas atthe other side, the piston rod also is foreseen with a singleclevis. The cylinder shell normally has hydraulic connectionsat both sides. A connection at bottom side and one at cylinderhead side. If oil is pushed under the piston, the piston-rod ispushed out and oil that was between the piston and thecylinder head is pushed back to the oil-tank again.

The pushing or pulling force of a hydraulic cylinder is:

F = Ab * pb - Ah * phF = Pushing Force in NAb = (/4) * (Bottom-diameter)^2 [in m2]Ah = (/4) * ((Bottom-diameter)^2-(Piston-rod-diameter)^2))[in m2]pb = pressure at bottom side in [N/m2]
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ph = pressure at cylinder head side in [N/m2]

Apart from miniature cylinders, in general, the smallestcylinder diameter is 32 mm and the smallest piston roddiameter is 16 mm.

Simple hydraulic cylinders have a maximum working pressureof about 70 bar, the next step is 140 bar, 210 bar, 320/350bar and further, the cylinders are in general custom build. Thestroke of a hydraulic cylinder is limited by the manufacturingprocess. The majority of hydraulic cylinders have a strokebetween 0,3 and 5 metres, whereas 12-15 metre stroke is alsopossible, but for this length only a limited number of suppliersare on the market.

In case the retracted length of the cylinder is too long for thecylinder to be build in the structure. In this case telescopiccylinders can be used. One has to realize that for simplepushing applications telescopic cylinders might be availableeasily; for higher forces and/or double acting cylinders, theymust be designed especially and are very expensive. Ifhydraulic cylinders are only used for pushing and the piston

rod is brought in again by other means, one can also useplunger cylinders. Plunger cylinders have no sealing over thepiston, or the piston does not exist. This means that only oneoil connection is necessary. In general the diameter of theplunger is rather large compared with a normal pistoncylinder, because this large area is needed.Whereas a hydraulic motor will always leak oil, a hydrauliccylinder does not have a leakage over the piston nor over thecylinder head sealing, so that there is no need for amechanical brake.

Hydraulic motor:
http://en.wikipedia.org/w/index.php?title=Telescopic_cylinders&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Telescopic_cylinders&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Telescopic_cylinders&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Telescopic_cylinders&action=edit&redlink=1


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The hydraulic motor is the rotary counterpart of the hydrauliccylinder.Conceptually, a hydraulic motor should be interchangeablewith hydraulic pump, because it performs the oppositefunction -- much as the conceptual DC electric motor is

interchangeable with a DC electrical generator. However,most hydraulic pumps cannot be used as hydraulic motorsbecause they cannot be back driven. Also, a hydraulic motoris usually designed for the working pressure at both sides ofthe motor.

Hydraulic valves:

These valves are usually very heavy duty to stand up to highpressures. Some special valves can control the direction of theflow of fluid and act as a control unit for a system.

Pneumatics

Pneumatics is the use ofpressurized gas to affectmechanical motion.Pneumatic power is used in industry, where factory machinesare commonly plumbed for compressed air; other compressedinert gases can also be used. Pneumatics also hasapplications in dentistry, construction, mining, and otherareas.

Examples of pneumatic systems:
http://en.wikipedia.org/wiki/Hydraulic_cylinderhttp://en.wikipedia.org/wiki/Hydraulic_cylinderhttp://en.wikipedia.org/wiki/Hydraulic_pumphttp://en.wikipedia.org/wiki/Electric_motorhttp://en.wikipedia.org/wiki/Electrical_generatorhttp://en.wikipedia.org/w/index.php?title=Backdrive&action=edit&redlink=1http://en.wikipedia.org/wiki/Pressurized_gashttp://en.wikipedia.org/wiki/Industryhttp://en.wikipedia.org/wiki/Compressed_airhttp://en.wikipedia.org/wiki/Inert_gaseshttp://en.wikipedia.org/wiki/Dentistryhttp://en.wikipedia.org/wiki/Constructionhttp://en.wikipedia.org/wiki/Mininghttp://en.wikipedia.org/wiki/Hydraulic_cylinderhttp://en.wikipedia.org/wiki/Hydraulic_cylinderhttp://en.wikipedia.org/wiki/Hydraulic_pumphttp://en.wikipedia.org/wiki/Electric_motorhttp://en.wikipedia.org/wiki/Electrical_generatorhttp://en.wikipedia.org/w/index.php?title=Backdrive&action=edit&redlink=1http://en.wikipedia.org/wiki/Pressurized_gashttp://en.wikipedia.org/wiki/Industryhttp://en.wikipedia.org/wiki/Compressed_airhttp://en.wikipedia.org/wiki/Inert_gaseshttp://en.wikipedia.org/wiki/Dentistryhttp://en.wikipedia.org/wiki/Constructionhttp://en.wikipedia.org/wiki/Mining


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Pneumatic drill (jackhammer) used by road workers Pneumatic nail gun Electro-pneumatic action Pneumatic switches Air compressors Vacuum pump Barostat systems used in Neuro gastroenterology and for

researching electricity Cable jetting, a way to install cables in ducts

Gases used in pneumatic systems:

Pneumatic systems in fixed installations such as factories usecompressed air because a sustainable supply can be made bycompressing atmospheric air. The air usually has moistureremoved and a small quantity of oil added at the compressor,to avoid corrosion of mechanical components and to lubricatethem.Factory-plumbed, pneumatic

14739255 pakistan machine tool factory internship report

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