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Electrical discharge machining

An electrical discharge machine

Electric discharge machining (EDM), sometimes colloquially also referred to as spark 

machining, spark eroding, burning, die sinking or wire erosion,[1] is a manufacturing processwhereby a wanted shape of an object, called workpiece, is obtained using electrical discharges

(sparks). The material removal from the workpiece occurs by a series of rapidly recurring current

discharges between two electrodes, separated by a dielectric liquid and subject to an electric

voltage. One of the electrodes is called tool-electrode and is sometimes simply referred to as‘tool’ or ‘electrode’, whereas the other is called workpiece-electrode, commonly abbreviated in

‘workpiece’. When the distance between the two electrodes is reduced, the intensity of the

electric field in the volume between the electrodes is expected to become larger than the strengthof the dielectric (at least in some point(s)) and therefore the dielectric breaks allowing some

current to flow between the two electrodes. This phenomenon is the same as the breakdown of a

capacitor (condenser) (see also breakdown voltage). A collateral effect of this passage of currentis that material is removed from both the electrodes. Once the current flow stops (or it is stopped

- depending on the type of generator), new liquid dielectric should be conveyed into the inter-

electrode volume enabling the removed electrode material solid particles (debris) to be carriedaway and the insulating proprieties of the dielectric to be restored. This addition of new liquid

dielectric in the inter-electrode volume is commonly referred to as flushing. Also, after a current

flow, a difference of potential between the two electrodes is restored as it was before the

 breakdown, so that a new liquid dielectric breakdown can occur.

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Contents

• 1 History• 2 Generalities

• 3 Definition of the technological parameters

• 4 Material removal mechanism

• 5 Types

o 5.1 Sinker EDM

o 5.2 Wire EDM

• 6 Applications

o 6.1 Prototype production

o 6.2 Coinage die making

o 6.3 Small hole drilling

• 7 Advantages and disadvantages

• 8 See also

• 9 References

• 10 External links

History

The EDM process was invented by two Russian scientists, Dr. B.R. Lazarenko and Dr. N.I.

Lazarenko in 1943.

The first numerically controlled (NC, or computer controlled) EDM was invented by Makino inJapan in 1980.

Agie launches in 1969 the world's first series-produced, numerically controlled wire-cut EDM

machine.

Generalities

Electrical discharge machining is a machining method primarily used for hard metals or those

that would be very difficult to machine with traditional techniques. EDM typically works withmaterials that are electrically conductive, although methods for machining insulating ceramics 

with EDM have also been proposed. EDM can cut intricate contours or cavities in pre-hardenedsteel without the need for heat treatment to soften and re-harden them. This method can be used

with any other metal or metal alloy such as titanium, hastelloy, kovar , and inconel.

EDM is often included in the ‘non-traditional’ or ‘non-conventional’ group of machining methods together with processes such as electrochemical machining (ECM), water jet cutting 

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(WJ, AWJ), laser cutting and opposite to the ‘conventional’ group (turning, milling, grinding,

drilling and any other process whose material removal mechanism is essentially based on

mechanical forces). Ideally, EDM can be seen as a series of breakdowns and restorations of theliquid dielectric in-between the electrodes. However, caution should be exerted in considering

such a statement because it is an idealized model of the process, introduced to describe the

fundamental ideas underlying the process. Yet, any practical application involves many aspectsthat may also need to be considered. For instance, the removal of the debris from the inter-

electrode volume is likely to be always partial. Thus the electrical proprieties of the dielectric in

the inter-electrodes volume can be different from their nominal values and can even vary withtime. The inter-electrode distance, often also referred to as spark-gap, is the end result of the

control algorithms of the specific machine used. The control of such a distance appears logically

to be central to this process. Also, not all of the current flow between the dielectric is of the ideal

type described above: the spark-gap can be short-circuited by the debris. The control system of the electrode may fails to react quickly enough to prevent the two electrodes (tool and

workpiece) to get in contact with a consequent short circuit. And this is unwanted because a short

circuit contributes to the removal differently from the ideal case. The flushing action can be

inadequate to restore the insulating properties of the dielectric so that the flow of current happensalways in the point of the inter-electrode volume (this is referred to as arcing), with a consequent

unwanted change of shape (damage) of the tool-electrode and workpiece. Ultimately, Adescription of this process in a suitable way for the specific purpose at hand is what makes the

EDM area such a rich field for further investigations and research. To obtain a specific geometry,

the EDM tool is guided along the desired path very close to the work, ideally it should not touch

the workpiece, although in reality this may happens due to the performance of the specificmotion control in use. In this way a large number of current discharges (colloquially also called

sparks) happen, each contributing to the removal of material from both tool and workpiece,

where small craters are formed. The size of the craters is a function of the technological parameters set for the specific job at hand. They can be with typical dimensions ranging from the

nanoscale (in micro-EDM operations) to some hundreds of micrometers in roughing conditions.

The presence of these small craters on the tool results in the gradual erosion of the electrode.This erosion of the tool-electrode is also referred to as wear. Strategies are needed to counteract

the detrimental effect of the wear on the geometry of the workpiece. One possibility is that of 

continuously replacing the tool-electrode during a machining operation. This is what happens if acontinuously replaced wire is used as electrode. In this case, the correspondent EDM process is

also called wire-EDM. The tool-electrode can also be used in such a way that only a small

 portion of it is actually engaged into the machining process and this portion is changed on a

regular basis. This is for instance the case, when using as tool-electrode a rotating disk. Thecorresponding process is often also referred to as EDM-grinding. A further strategy consists in

using a set of electrodes with different sizes and shapes during the same EDM operation. This is

often referred to as multiple electrode strategy and is most common when the tool electrodereplicates in negative the wanted shape and is advanced towards the blank along a single

direction, usually the vertical direction (i.e. z- axis). This resembles the sink of the tool into the

dielectric liquid in which the workpiece is immersed, so, not surprisingly, it is often referred to asdie-sinking EDM (also called Conventional EDM and Ram EDM). The correspondent machines

are often called Sinker EDM. Usually, the electrodes of this types have quite complex forms. If 

the final geometry is obtained using a usually simple shaped electrode which is moved along

several directions and is possibly also subject to rotations often the term EDM-milling is used. In

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any case, the severity of the wear is strictly dependent on the technological parameters used in

the operation (for instance: polarity, maximum current, open circuit voltage). For example, in

micro-EDM, also known as μ-EDM, these parameters are usually set at values which generatessever wear. Therefore, wear is a major problem in that area.

Definition of the technological parameters

Some difficulties have been encountered in the definition of the technological parameters that

drive the process. The reasons are explained below.

On the one hand, two broad categories of generators, also known as power supplies, are in use on

EDM machines commercially available: the group based on RC circuits and the group based on

transistor controlled pulses. In the first category, the main parameters that a practitioner may be

expected to choose from at set-up time are the resistance(s) of the resistor(s) and thecapacitance(s) of the capacitor(s).

In an ideal condition these quantities would then affect the maximum current delivered in anideal discharge, which is expected to be associated with the charge accumulated on the capacitorsat a certain moment in time. Little control, however is expected to be possible on the time

duration of the discharge, which is likely to depend on the actual spark-gap conditions (size and

 pollution) at the moment of the discharge. Yet, this kind of generators can allow the user to

obtain short time durations of the discharges relatively easier than with the a pulse controlledgenerator. This advantage is however going to be diminished with the progress in the production

of electronic components.[2] Also, the open circuit voltage (i.e. the voltage between the electrodes

when the dielectric is not yet broken) can be identified as steady state voltage of the RC circuit.In the second group of generators, based on transistor control usually enables the user to deliver 

a train of pulses of voltage to the electrodes. Each pulse can be controlled in shape, for instance

quasi-rectangular. In particular, the time between two consecutive pulses and the duration of each pulse can be set. The amplitude of each pulse constitutes the open circuit voltage. In this

framework, the maximum time duration of a current discharge is equal to the duration of a pulse

of voltage in the train. Two pulses of current are then expected not to occur for a duration equal

or larger than the time interval between two consecutive pulses of voltage. The maximum currentduring a discharge that the generator deliver can also be controlled. Design of generators

different from that described above is likely to be commercially available. Thus, the parameters

that a user may actually set on his own machine may be quite different and generator-manufacturer dependent. Moreover, the manufacturers are usually quite reluctant to unveil the

details of their generators and control systems to their user base not to give a potential

competitive advantage to their competitors. And, conversely, the average users are usually more

interested in a ‘machine that can do the job’, rather than in through understanding of the EDM process. This circumstance constitutes another barrier to the attempt of describing unequivocally

the technological parameters of the EDM process. Moreover, the parameters affecting the

 phenomena occurring between tool and electrode are related not only to the generator design butalso to the controller of the motion of the electrodes. A framework to define and measure the

electrical parameters during an EDM operation directly on inter-electrode volume with an

oscilloscope external to the machine has been recently proposed by Ferri et al.[3] These authorsconducted their research in the filed of μ-EDM, but the same approach can be used in any EDM

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operation. This would enable the user to estimate directly the electrical parameter that affect their 

operations in an open way, without relying upon machine manufacturer's claims. Finally, it is

worth mentioning that, quite unexpectedly, when machining different materials in identicalnominal set-up conditions the actual electrical parameters of the process are significantly

different.[3]

Material removal mechanism

The first serious attempt of providing a physical explanation of the material removal duringelectric discharge machining is perhaps that of Van Dijk [4]. In his work, Van Dijk present a

thermal model together with a computational simulation to explain the phenomena between the

electrodes during electric discharge machining. However, as Van Dijk himself admitted in hisstudy, the number of assumptions made to overcome the unavailability of experimental data at

that time was quite significant.

Further enhanced models trying to explain the phenomena occurring during electric discharge

machining in terms of heat transfer theories were developed in the late eighties and earlynineties. Possibly the most advanced explanation of the EDM process as a thermal process was

developed during an investigation carried out at TeXas A&M University with the support of 

AGIE, now Agiecharmilles, a company with headquarters in Switzerland. This stream of research resulted in a series of three scholarly papers: the first presenting a thermal model

addressing the material removal on the cathode [5] , the second, presenting a thermal model for 

the erosion occurring on the anode [6] and the third introducing a model describing the plasma

channel that is formed during the passage of the discharge current through the dielectric liquid [7].Validation of these models is carried out also using experimental data provided by AGIE. These

models constitute the most authoritative support for the claim that EDM is a thermal process,

describing how the material is removed from the two electrodes because of melting and/or 

vaporization processes in conjunction with pressure dynamics established in the spark-gap by thecollapsing of the plasma channel. However, from a careful reading of these papers it emerges

that for small discharge energies the presented models are quite inadequate to explain theexperimental data. Also, all these models hinge on a number of assumptions, often taken from

such disparate research areas as submarine explosions, discharges in gases, and failure of 

transformers. So it is not surprising that alternative models have been proposed more recently inthe literature trying to explain the EDM process. Among these, the model from Sigh and Ghosh[8] re-connects the removal of material from the electrode to the presence of an electrical force on

the surface of the electrode that would be able to mechanically remove material and create the

craters. This would be made possible by the fact that the material on the surface has reducedmechanical proprieties due to an increased temperature caused by the passage of electrical

current. The authors simulated their models and showed how they might explain EDM better than a thermal model (melting and/or evaporation), especially for small discharge energies,which are typically used in μ-EDM and in finishing operations. In the light of the many available

models, it appears that the material removal mechanism in EDM is not yet well understood and

that further investigation is necessary to clarify it.[3] Especially considering the lack of experimental scientific evidence to build and validate the current EDM models.[3]

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Types

Sinker EDM

Sinker EDM sometimes is also referred to as cavity type EDM or volume EDM. Sinker EDM

consists of an electrode and workpiece that are submerged in an insulating liquid such as oil or dielectric fluid. The electrode and workpiece are connected to a suitable power supply. The

 power supply generates an electrical potential between the two parts. As the electrode approaches

the workpiece, dielectric breakdown occurs in the fluid forming an ionization channel, and a

small spark jumps. The resulting heat and cavitation vaporize the base material, and to someextent, the electrode. These sparks strike one at a time in huge numbers at seemingly random

locations between the electrode and the workpiece. As the base metal is eroded, and the spark 

gap subsequently increased, the electrode is lowered automatically by the machine so that the process can continue uninterrupted. Several hundred thousand sparks occur per second in this

 process, with the actual duty cycle being carefully controlled by the setup parameters. These

controlling cycles are sometimes known as "on time" and "off time". The on time setting

determines the length or duration of the spark. Hence, a longer on time produces a deeper cavityfor that spark and all subsequent sparks for that cycle creating a rougher finish on the workpiece.

The reverse is true for a shorter on time. Off time is the period of time that one spark is replaced

 by another. A longer off time for example, allows the flushing of dielectric fluid through a nozzleto clean out the eroded debris, thereby avoiding a short circuit. These settings are maintained in

micro seconds. The typical part geometry is to cut small or odd shaped angles. Vertical, orbital,

vectorial, directional, helical, conical, rotational, spin and indexing machining cycles are alsoused.

Wire EDM

In wire electrical discharge machining (WEDM), or wire-cut EDM, a thin single-strand metalwire, usually brass, is fed through the workpiece, typically occurring submerged in a tank of 

dielectric fluid. This process is used to cut plates as thick as 300mm and to make punches,

tools,and dies from hard metals that are too difficult to machine with other methods. The wire,which is constantly fed from a spool, is held between upper and lower diamond guides. The

guides move in the x –  y plane, usually being CNC controlled and on almost all modern machines

the upper guide can also move independently in the z  – u – v axis, giving rise to the ability to cuttapered and transitioning shapes (circle on the bottom square at the top for example) and can

control axis movements in x –  y – u – v – i –  j – k  – l  –. This gives the wire-cut EDM the ability to be

 programmed to cut very intricate and delicate shapes. The wire is controlled by upper and lower 

diamond guides that are usually accurate to 0.004 mm, and can have a cutting path or kerf as

small as 0.12 mm using Ø 0.1 mm wire, though the average cutting kerf that achieves the besteconomic cost and machining time is 0.335 mm using Ø 0.25 brass wire. The reason that the

cutting width is greater than the width of the wire is because sparking also occurs from the sidesof the wire to the work piece, causing erosion. This "overcut" is necessary, predictable, and

easily compensated for. Spools of wire are typically very long. For example, an 8 kg spool of 

0.25 mm wire is just over 19 kilometers long. Today, the smallest wire diameter is 20micrometres and the geometry precision is not far from +/- 1 micrometre. The wire-cut process

uses water as its dielectric with the water's resistivity and other electrical properties carefully

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EDM control panel (Hansvedt machine). Machine may be adjusted for a refined surface

(electropolish) at end of process.

Master at top, badge die workpiece at bottom, oil jets at left (oil has been drained). Initial flatstamping will be "dapped" to give a curved surface.

Small hole drilling

Small hole drilling EDM is used to make a through hole in a workpiece in through which to

thread the wire in Wire-cut EDM machining. The small hole drilling head is mounted on wire-cutmachine and allows large hardened plates to have finished parts eroded from them as needed and

without pre-drilling. There are also stand-alone small hole drilling EDM machines with an x –  y

axis also known as a super drill or hole popper that can machine blind or through holes. EDM

Drills bore holes with a long brass or copper tube electrode that rotates in a chuck with a constant

flow of distilled or deionized water flowing through the electrode as a flushing agent anddielectric. The electrode tubes operate like the wire in wire-cut EDM machines, having a spark 

gap and wear rate. Some small-hole drilling EDMs are able to drill through 100 mm of soft or 

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through hardened steel in less than 10 seconds, averaging 50% to 80% wear rate. Holes of 

0.3 mm to 6.1 mm can be achieved in this drilling operation. Brass electrodes are easier to

machine but are not recommended for wire-cut operations due to eroded brass particles causing"brass on brass" wire breakage, therefore copper is recommended.

Advantages and disadvantages

Some of the advantages of EDM include machining of:

• complex shapes that would otherwise be difficult to produce with conventional cutting

tools

• extremely hard material to very close tolerances

• very small work pieces where conventional cutting tools may damage the part from

excess cutting tool pressure.

Some of the disadvantages of EDM include:

• The slow rate of material removal.

• The additional time and cost used for creating electrodes for ram / Sinker EDM.

• Reproducing sharp corners on the workpiece is difficult due to electrode wear.

Dielectric

A dielectric is a nonconducting substance, i.e. an insulator . The term was coined by WilliamWhewell in response to a request from Michael Faraday.[1] Although "dielectric" and "insulator"

are generally considered synonymous, the term "dielectric" is more often used to describe

materials where the dielectric polarization is important, such as the insulating material betweenthe metallic plates of a capacitor , while "insulator" is more often used when the material is being

used to prevent a current flow across it.

Dielectrics is the study of dielectric materials and involves physical models to describe how an

electric field  behaves inside a material. It is characterized by how an electric field interacts withan atom and is therefore possible to approach from either a classical interpretation or a quantum

one.

Many phenomena in electronics, solid state and optical physics can be described using the

underlying assumptions of the dielectric model. This can mean that the same mathematical

objects can go by many different names.

Contents

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• 1 Definitions

o 1.1 Classicalo 1.2 Behavior 

• 2 Dielectric model applied to vacuum

• 3 Applications

o 3.1 Capacitors

o 3.2 Cable insulation

• 4 Some practical dielectrics

• 5 See also

• 6 References

• 7 External links

Definitions

Electric field interaction with an atom under the classical dielectric model.

Von Hippel, in his seminal work, Dielectric Materials and Applications, stated:

 Dielectrics... are not a narrow class of so-called insulators, but the broad expanse of nonmetals

considered from the standpoint of their interaction with electric, magnetic, or electromagnetic

fields. Thus we are concerned with gases as well as with liquids and solids, and with the storageof electric and magnetic energy as well as its dissipation.[2]

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Classical

In the classical approach to the dielectric model, a material is made up of atoms. Each atom

consists of a cloud of negative charge bound to and surrounding a positive point charge at its

centre. Because of the comparatively huge distance between them, none of the atoms in the

dielectric material interact with one another [citation needed ]

. Note: Remember that the model is not attempting to say anything about the structure of matter. It is only trying to describe theinteraction between an electric field and matter.

In the presence of an electric field the charge cloud is distorted, as shown in the top right of thefigure.

This can be reduced to a simple dipole using the superposition principle. A dipole is

characterized by its dipole moment, a vector quantity shown in the figure as the blue arrow

labeled M . It is the relationship between the electric field and the dipole moment that gives riseto the behavior of the dielectric. Note: The dipole moment is shown to be pointing in the same

direction as the electric field. This isn't always correct, and it is a major simplification, but it is suitable for many materials.[citation needed ]

When the electric field is removed the atom returns to its original state. The time required to doso is the so-called relaxation time; an exponential decay.

Behavior

This is the essence of the model in physics. The behavior of the dielectric now depends on thesituation. The more complicated the situation the richer the model has to be in order to accurately

describe the behavior. Important questions are:

• Is the electric field constant or does it vary with time?

o If the electric field does vary, at what rate?

• What are the characteristics of the material?

o Is the direction of the field important (isotropy)?

o Is the material the same all the way through (homogeneous)?

o Are there any boundaries/interfaces that have to be taken into account?

• Is the system linear or do nonlinearities have to be taken into account?

The relationship between the electric field E and the dipole moment M gives rise to the behavior of the dielectric, which, for a given material, can be characterized by the function F defined by

the equation:

.

When both the type of electric field and the type of material have been defined, one then chooses

the simplest function F that correctly predicts the phenomena of interest. Examples of possible

 phenomena:

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• Refractive index

• Group velocity dispersion

• Birefringence

• Self-focusing

• Harmonic generation

May be modeled by choosing a suitable function F.

Dielectric model applied to vacuum

From the definition it might seem strange to apply the dielectric model to a vacuum, however, itis both the simplest and the most accurate example of a dielectric.

Recall that the property which defines how a dielectric behaves is the relationship between the

applied electric field and the induced dipole moment. For a vacuum the relationship is a real 

constant number. This constant is called the  permittivity of free space, ε0.

Applications

Capacitors

Commercially manufactured capacitors typically use a solid dielectric material with high permittivity as the intervening medium between the stored positive and negative charges. This

material is often referred to in technical contexts as the "capacitor dielectric" [3] . The most

obvious advantage to using such a dielectric material is that it prevents the conducting plates onwhich the charges are stored from coming into direct electrical contact. More significantly

however, a high permittivity allows a greater charge to be stored at a given voltage. This can beseen by treating the case of a linear dielectric with permittivity ε and thickness d between two

conducting plates with uniform charge density σε. In this case, the charge density is given by

and the capacitance per unit area by

From this, it can easily be seen that a larger ε leads to greater charge stored and thus greater capacitance.

Dielectric materials used for capacitors are also chosen such that they are resistant to ionization.

This allows the capacitor to operate at higher voltages before the insulating dielectric ionizes and

 begins to allow undesirable current flow.

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Cable insulation

The term "dielectric" may also refer to the insulation used in power and RF cables [citation needed ].

Common materials used as electrical insulations are electrical insulation paper  and  plastics.

Some practical dielectrics

Dielectric materials can be solids, liquids, or gases. In addition, a high vacuum can also be auseful, lossless dielectric even though its relative dielectric constant is only unity.

Solid dielectrics are perhaps the most commonly used dielectrics in electrical engineering, and

many solids are very good insulators. Some examples include porcelain, glass, and most  plastics.

Air, nitrogen and sulfur hexafluoride are the three most commonly used gaseous dielectrics.

• Industrial coatings such as parylene  provide a dielectric barrier between the substrate and

its environment.

• Mineral oil is used extensively inside electrical transformers as a fluid dielectric and to

assist in cooling. Dielectric fluids with higher dielectric constants, such as electrical gradecastor oil, are often used in high voltage capacitors to help prevent corona discharge and

increase capacitance.

• Because dielectrics resist the flow of electricity, the surface of a dielectric may retain

 stranded excess electrical charges. This may occur accidentally when the dielectric isrubbed (the triboelectric effect). This can be useful, as in a Van de Graaff generator or 

electrophorus, or it can be potentially destructive as in the case of  electrostatic discharge.

• Specially processed dielectrics, called electrets (also known as ferroelectrics), may retain

excess internal charge or "frozen in" polarization. Electrets have a semipermanent

external electric field, and are the electrostatic equivalent to magnets. Electrets have

numerous practical applications in the home and industry.

• Some dielectrics can generate a potential difference when subjected to mechanical stress,

or change physical shape if an external voltage is applied across the material. This

 property is called piezoelectricity. Piezoelectric materials are another class of very useful

dielectrics.

• Some ionic crystals and  polymer dielectrics exhibit a spontaneous dipole moment which

can be reversed by an externally applied electric field. This behavior is called the

ferroelectric effect. These materials are analogous to the way ferromagnetic materials

 behave within an externally applied magnetic field. Ferroelectric materials often havevery high dielectric constants, making them quite useful for capacitors.

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Milling machine

Example of a CNC vertical milling center 

A CAD designed part (top) and physical part (bottom) produced by CNC milling.

This article includes a list of references, related reading or external links, but its sources

remain unclear because it lacks inline citations. Please improve this article by

introducing more precise citations where appropriate. (October 2008)

A milling machine is a machine tool used for the shaping of metal and other solid materials.

Milling machines exist in two basic forms: horizontal and vertical, which terms refer to theorientation of the cutting tool spindle. Unlike a drill press, in which the workpiece is held

stationary and the drill is moved vertically to penetrate the material, milling also involves

movement of the workpiece against the rotating cutter, the latter which is able to cut on its flanks

as well as its tip. Workpiece and cutter movement are precisely controlled to less than 0.001inches (.025 millimeters), usually by means of precision ground slides and leadscrews or 

analogous technology. Milling machines may be manually operated, mechanically automated, or 

digitally automated via computer numerical control (CNC).

Milling machines can perform a vast number of operations, some very complex, such as slot andkeyway cutting, planing, drilling, diesinking, rebating, routing, etc. Cutting fluid is often pumped

to the cutting site to cool and lubricate the cut, and to sluice away the resulting swarf .

Contents

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[hide]

• 1 Types

o 1.1 Comparing vertical with horizontal

o 1.2 Other milling machine variants and terminology

•

2 Computer numerical controlo 2.1 Milling machine tooling

• 3 History

o 3.1 1810s-1830s

o 3.2 1840s-1860

o 3.3 1860s

o 3.4 1870s-1930s

o 3.5 1940s-1970s

o 3.6 1980s-present

• 4 See also

• 5 References

• 6 Further reading

• 7 External links

Types

There are many ways to classify milling machines, depending on which criteria are the focus:

Criterion Example classification scheme Comments

Control

Manual;

Mechanically automated via cams;Digitally automated via  NC/CNC

In the CNC era, a very basic distinction is manual versus

CNC.Among manual machines, a worthwhile distinction is non-

DRO-equipped versus DRO-equipped

Control (specifically

among CNC machines)

 Number of axes (e.g., 3-axis, 4-axis,

or more);

Within this scheme, also:

• Pallet-changing versus non-

 pallet-changing

• Full-auto tool-changing

versus semi-auto or manual

tool-changing

 

Spindle axis orientationVertical versus horizontal;

Turret versus non-turret

Among vertical mills, "Bridgeport-style" is a whole class of 

mills inspired by the Bridgeport original

PurposeGeneral-purpose versus special-

 purpose or single-purpose 

PurposeToolroom machine versus production

machineOverlaps with above

Purpose "Plain" versus "universal" A distinction whose meaning evolved over decades as

technology progressed, and overlaps with other purpose

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classifications above; more historical interest than current

SizeMicro, mini, benchtop, standing on

floor, large, very large, gigantic 

Power source

Line-shaft-drive versus individual

electric motor drive

Most line-shaft-drive machines, ubiquitous circa 1880-1930,

have been scrapped by now

Hand-crank-power versus electric Hand-cranked not used in industry but suitable for hobbyistmicromills

Comparing vertical with horizontal

In the vertical mill the spindle axis is vertically oriented. Milling cutters are held in the spindle

and rotate on its axis. The spindle can generally be extended (or the table can be raised/lowered,giving the same effect), allowing plunge cuts and drilling. There are two subcategories of vertical

mills: the bedmill and the turret mill. Turret mills, like the ubiquitous Bridgeport, are generally

smaller than bedmills, and are considered by some to be more versatile. In a turret mill the

spindle remains stationary during cutting operations and the table is moved both perpendicular to

and parallel to the spindle axis to accomplish cutting. In the bedmill, however, the table movesonly perpendicular to the spindle's axis, while the spindle itself moves parallel to its own axis.

Also of note is a lighter machine, called a mill-drill. It is quite popular with hobbyists, due to itssmall size and lower price. These are frequently of lower quality than other types of machines,

however.

A horizontal mill has the same sort of  x –  y table, but the cutters are mounted on a horizontal arbor 

(see Arbor milling) across the table. A majority of horizontal mills also feature a +15/-15 degreerotary table that allows milling at shallow angles. While endmills and the other types of tools

available to a vertical mill may be used in a horizontal mill, their real advantage lies in arbor-

mounted cutters, called side and face mills, which have a cross section rather like a circular saw,

 but are generally wider and smaller in diameter. Because the cutters have good support from thearbor, quite heavy cuts can be taken, enabling rapid material removal rates. These are used to

mill grooves and slots. Plain mills are used to shape flat surfaces. Several cutters may be gangedtogether on the arbor to mill a complex shape of slots and planes. Special cutters can also cut

grooves, bevels, radii, or indeed any section desired. These specialty cutters tend to be expensive.

Simplex mills have one spindle, and duplex mills have two. It is also easier to cut gears on a

horizontal mill.

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A miniature hobbyist mill plainly showing the basic parts of a mill.

Other milling machine variants and terminology

•  Box or column mills are very basic hobbyist bench-mounted milling machines that feature

a head riding up and down on a column or box way.

• Turret or vertical ram mills are more commonly referred to as Bridgeport-type milling

machines. The spindle can be aligned in many different positions for a very versatile, if 

somewhat less rigid machine.

•  Knee mill or knee-and-column mill refers to any milling machine whose x-y table rides up

and down the column on a vertically adjustable knee. This includes Bridgeports.

• C-Frame mills are larger, industrial production mills. They feature a knee and fixed

spindle head that is only mobile vertically. They are typically much more powerful than a

turret mill, featuring a separate hydraulic motor for integral hydraulic power feeds in alldirections, and a twenty to fifty horsepower motor. Backlash eliminators are almost

always standard equipment. They use large NMTB 40 or 50 tooling. The tables on C-

frame mills are usually 18" by 68" or larger, to allow multiple parts to be machined at thesame time.

•  Planer-style mills are large mills built in the same configuration as  planers except with a

milling spindle instead of a planing head. This term is growing dated as planersthemselves are largely a thing of the past.

•  Bed mill refers to any milling machine where the spindle is on a pendant that moves up

and down to move the cutter into the work. These are generally more rigid than a knee

mill.

•  Ram type mill refers to a mill that has a swiveling cutting head mounted on a sliding ram.The spindle can be oriented either vertically or horizontally, or anywhere in between. Van

 Norman specialized in ram type mills through most of the 20th century, but since theadvent of CNC machines ram type mills are no longer made.

•  Jig borers are vertical mills that are built to bore holes, and very light slot or face milling.

They are typically bed mills with a long spindle throw. The beds are more accurate, and

the handwheels are graduated down to .0001" for precise hole placement.

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•  Horizontal boring mills are large, accurate bed horizontal mills that incorporate many

features from various machine tools. They are predominantly used to create large

manufacturing jigs, or to modify large, high precision parts. They have a spindle stroke of several (usually between four and six) feet, and many are equipped with a tailstock to

 perform very long boring operations without losing accuracy as the bore increases in

depth. A typical bed would have X and Y travel, and be between three and four feetsquare with a rotary table or a larger rectangle without said table. The pendant usually has

 between four and eight feet in vertical movement. Some mills have a large (30" or more)

integral facing head. Right angle rotary tables and vertical milling attachments areavailable to further increase productivity.

•  Floor mills have a row of rotary tables, and a horizontal pendant spindle mounted on a set

of tracks that runs parallel to the table row. These mills have predominantly been

converted to CNC, but some can still be found (if one can even find a used machineavailable) under manual control. The spindle carriage moves to each individual table,

 performs the machining operations, and moves to the next table while the previous table

is being set up for the next operation. Unlike any other kind of mill, floor mills have floor 

units that are entirely movable. A crane will drop massive rotary tables, X-Y tables, andthe like into position for machining, allowing the largest and most complex custom

milling operations to take place.

Computer numerical control

Thin wall milling of aluminum using a water based coolant on the milling cutter 

Most CNC milling machines (also called machining centers) are computer controlled vertical

mills with the ability to move the spindle vertically along the Z-axis. This extra degree of freedom permits their use in diesinking, engraving applications, and 2.5D surfaces such as relief  

sculptures. When combined with the use of  conical tools or a ball nose cutter , it also significantly

improves milling precision without impacting speed, providing a cost-efficient alternative to

most flat-surface hand-engraving work.

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Five-axis machining center with rotating table and computer interface

CNC machines can exist in virtually any of the forms of manual machinery, like horizontal mills.The most advanced CNC milling-machines, the 5-axis machines, add two more axes in addition

to the three normal axes (XYZ). Horizontal milling machines also have a C or Q axis, allowing

the horizontally mounted workpiece to be rotated, essentially allowing asymmetric and eccentric 

turning. The fifth axis (B axis) controls the tilt of the tool itself. When all of these axes are usedin conjunction with each other, extremely complicated geometries, even organic geometries such

as a human head can be made with relative ease with these machines. But the skill to programsuch geometries is beyond that of most operators. Therefore, 5-axis milling machines are practically always programmed with CAM.

With the declining price of computers, free operating systems such as Linux, and open source 

CNC software, the entry price of CNC machines has plummeted. For example, Sherline, Prazi,

and others make desktop CNC milling machines that are affordable by hobbyists.

High speed steel with cobalt endmills used for cutting operations in a milling machine.

Milling machine tooling

There is some degree of standardization of the tooling used with CNC Milling Machines and to a

much lesser degree with manual milling machines.

CNC Milling machines will nearly always use SK (or ISO), CAT, BT or HSK tooling. SK tooling

is the most common in Europe, while CAT tooling, sometimes called V-Flange Tooling, is theoldest variation and is probably still the most common in the USA. CAT tooling was invented by

Caterpillar Inc. of Peoria, Illinois in order to standardize the tooling used on their machinery.CAT tooling comes in a range of sizes designated as CAT-30, CAT-40, CAT-50, etc. The number 

refers to the Association for Manufacturing Technology (formerly the National Machine Tool

Builders Association (NMTB)) Taper size of the tool.

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CAT-40 Toolholder 

An improvement on CAT Tooling is BT Tooling, which looks very similar and can easily beconfused with CAT tooling. Like CAT Tooling, BT Tooling comes in a range of sizes and uses

the same NMTB body taper. However, BT tooling is symmetrical about the spindle axis, which

CAT tooling is not. This gives BT tooling greater stability and balance at high speeds. One other 

subtle difference between these two toolholders is the thread used to hold the pull stud. CATTooling is all Imperial thread and BT Tooling is all Metric thread. Note that this affects the pull

stud only, it does not affect the tool that they can hold, both types of tooling are sold to accept

 both Imperial and metric sized tools.

SK and HSK tooling, sometimes called "Hollow Shank Tooling", is much more common inEurope where it was invented than it is in the United States. It is claimed that HSK tooling is

even better than BT Tooling at high speeds. The holding mechanism for HSK tooling is placed

within the (hollow) body of the tool and, as spindle speed increases, it expands, gripping the toolmore tightly with increasing spindle speed. There is no pull stud with this type of tooling.

The situation is quite different for manual milling machines — there is little standardization.

 Newer and larger manual machines usually use NMTB tooling. This tooling is somewhat similar 

to CAT tooling but requires a drawbar within the milling machine. Furthermore, there are anumber of variations with NMTB tooling that make interchangeability troublesome.

Boring head on Morse Taper Shank 

Two other tool holding systems for manual machines are worthy of note: They are the R8 colletand the Morse Taper #2 collet. Bridgeport Machines of Bridgeport, Connecticut so dominated the

milling machine market for such a long time that their machine "The Bridgeport" is virtually

synonymous with "Manual milling machine." The bulk of the machines that Bridgeport madefrom about 1965 onward used an R8 collet system. Prior to that, the bulk of the machines used a

Morse Taper #2 collet system.

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As an historical footnote: Bridgeport is now owned by Hardinge Brothers of Elmira, New York .

History

1810s-1830s

Milling machines evolved from the practice of rotary filing—that is, running a circular cutter 

with file-like teeth in the headstock of a lathe. Both rotary filing and later true milling weredeveloped in order to reduce the time and effort spent on hand-filing. The full, true story of the

milling machine's development will probably never be known, because much of the early

development took place in individual shops where generally no one was taking down records for  posterity. However, the broad outlines are known. Rotary filing long predated milling. A rotary

file by Jacques de Vaucanson, circa 1760, is well known. It is clear that milling machines as a

distinct class of machine tool (separate from lathes running rotary files) first appeared between

1814 and 1818. Joseph W. Roe, a respected founding father of machine tool historians, creditedEli Whitney with producing the first true milling machine. However, subsequent scholars,

including Robert S. Woodbury and others, suggest that just as much credit belongs to variousother inventors, including Robert Johnson, Simeon North, Captain John H. Hall, and ThomasBlanchard. (Several of the men mentioned above are sometimes described on the internet as "the

inventor of the first milling machine" or "the inventor of interchangeable parts". Such claims are

oversimplified, as these technologies evolved over time among many people.) The two federalarmories of the U.S. (Springfield and Harpers Ferry) and the various private armories and inside

contractors that shared turnover  of skilled workmen with them were the centers of earliest

development of true milling machines (as distinct from lathe headstocks tooled up for rotaryfiling).

James Nasmyth built a milling machine very advanced for its time between 1829 and 1831. It

was tooled to mill the six sides of a hex nut that was mounted in a six-way indexing fixture.

A milling machine built and used in the shop of Gay & Silver (aka Gay, Silver, & Co) in the

1830s was influential because it employed a better method of vertical positioning than earlier machines. For example, Whitney's machine (the one that Roe considered the very first) and

others did not make provision for vertical travel of the knee. Evidently the workflow assumption

 behind this was that the machine would be set up with shims, vise, etc. for a certain part designand successive parts would not require vertical adjustment (or at most would need only

shimming). This indicates that the earliest way of thinking about milling machines was as

 production machines, not toolroom machines.

1840s-1860

Some of the key men in milling machine development during this era included Frederick W.

Howe, Francis A. Pratt, Elisha K. Root, and others. (These same men during the same era werealso busy developing the state of the art in turret lathes. Howe's experience at Gay & Silver in the

1840s acquainted him with early versions of both machine tools. His machine tool designs were

later built at Robbins & Lawrence, the Providence Tool Company, and Brown & Sharpe.) The

most successful milling machine design to emerge during this era was the Lincoln miller , which

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rather than being a specific make and model of machine tool is truly a family of related tools

 built by various companies over several decades. It took its name from the first company to put

one on the market, George S. Lincoln & Company.

During this era there was a continued blind spot in milling machine design, as various designers

failed to develop a truly simple and effective means of providing slide travel in all three of thearchetypal milling axes (X, Y, and Z—or as they were known in the past, longitudinal, traverse,

and vertical). Vertical positioning ideas were either absent or underdeveloped.

1860s

Brown & Sharpe's groundbreaking universal milling machine, 1861.

In 1861, Frederick W. Howe, while working for the Providence Tool Company, asked Joseph R.

Brown of Brown & Sharpe for a solution to the problem of milling spirals, such as the flutes of twist drills. These were filed by hand at the time. Brown designed a "universal milling machine"

that, starting from its first sale in March 1862, was wildly successful. It solved the problem of 3-

axis (XYZ) travel much more elegantly than had been done in the past, and it allowed for themilling of spirals using an indexing head fed in coordination with the table feed. The term

"universal" was applied to it because it was ready for any kind of work and was not as limited in

application as previous designs. (Howe had designed a "universal miller" in 1852, but Brown's of 1861 is the one considered groundbreakingly successful.)

Brown also developed and patented (1864) the design of formed milling cutters in which

successive sharpenings of the teeth do not disturb the geometry of the form.

The advances of the 1860s opened the floodgates and ushered in modern milling practice.

1870s-1930s

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Two firms which most dominated the milling machine field during these decades were Brown &

Sharpe and the Cincinnati Milling Machine Company. However, hundreds of other firms built

milling machines during this time, and many were significant in one way or another. Thearchetypal workhorse milling machine of the late 19th and early 20th centuries was a heavy

knee-and-column horizontal-spindle design with power table feeds, indexing head, and a stout

overarm to support the arbor.

A. L. De Leeuw of the Cincinnati Milling Machine Company is credited with applying scientificstudy to the design of milling cutters, leading to modern practice with larger, more widely spaced

teeth.

Around the end of World War I, machine tool control advanced in various ways that laid the

groundwork for later CNC technology. The  jig borer popularized the ideas of coordinatedimensioning (dimensioning of all locations on the part from a single reference point); working

routinely in "tenths" (ten-thousandths of an inch, 0.0001") as an everyday machine capability;

and using the control to go straight from drawing to part, circumventing jig-making. In 1920 the

new tracer design of J.C. Shaw was applied to Keller tracer milling machines for die-sinking viathe three-dimensional copying of a template. This made diesinking faster and easier just as dies

were in higher demand than ever before, and was very helpful for large steel dies such as thoseused to stamp sheets in automobile manufacturing. Such machines translated the tracer 

movements to input for servos that worked the machine leadscrews or hydraulics. They also

spurred the development of antibacklash leadscrew nuts. All of the above concepts were new inthe 1920s but would become routine in the NC/CNC era. By the 1930s, incredibly large and

advanced milling machines existed, such as the Cincinnati Hydro-Tel, that presaged today's CNC

mills in every respect except the CNC control itself.

1940s-1970s

By 1940, automation via cams, such as in screw machines and automatic chuckers, had already

 been very well developed for decades. By the close of World War II, many additional ideasinvolving servomechanisms were in the air. These ideas, which soon were combined with the

emerging technology of digital computers, transformed machine tool control very deeply. The

details (which are beyond the scope of this article) have evolved immensely with every passingdecade since World War II.

During the 1950s, numerical control (NC) made its appearance.

During the 1960s and 1970s, NC evolved into CNC, data storage and input media evolved,

computer processing power and memory capacity steadily increased, and NC and CNC machinetools gradually disseminated from the level of huge corporations to the level of medium-sized

corporations.

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1980s-present

Computers and CNC machine tools continue to develop rapidly. The PC revolution has a great

impact on this development. By the late 1980s small machine shops had desktop computers and

CNC machine tools. After that hobbyists began obtaining CNC mills and lathes

G-code

This article is about the machine tool programming language. For the video recorder 

 programming system, see Video recorder scheduling code.

G-Code, or preparatory code or function, are functions in the Numerical control  programming

language. The G-codes are the codes that position the tool and do the actual work, as opposed to

M-codes, that manages the machine; T for tool-related codes. S and F are tool-Speed and tool-

Feed, and finally D-codes for tool compensation.

The programming language of Numerical Control (NC) is sometimes informally called G-code.

But in actuality, G-codes are only a part of the NC-programming language that controls NC and

CNC machine tools. The term Numerical Control was coined at the MIT ServomechanismsLaboratory, and several versions of NC were and are still developed independently by CNC-

machine manufacturers. The main standardized version used in the United States was settled by

the Electronic Industries Alliance in the early 1960s. A final revision was approved in February

1980 as RS274D. In Europe, the standard DIN 66025 / ISO 6983 is often used instead.

Due to the lack of further development, the immense variety of machine tool configurations, and

little demand for interoperability, few machine tool controllers (CNCs) adhere to this standard.Extensions and variations have been added independently by manufacturers, and operators of a

specific controller must be aware of differences of each manufacturers' product. When initiallyintroduced, CAM systems were limited in the configurations of tools supported.

Today, the main manufacturers of CNC control systems are GE Fanuc Automation (joint venture

of General Electric and Fanuc), Siemens, Mitsubishi, and Heidenhain, but there still exist manysmaller and/or older controller systems.

Some CNC machine manufacturers attempted to overcome compatibility difficulties by

standardizing on a machine tool controller built by Fanuc. Unfortunately, Fanuc does not remain

consistent with RS-274 or its own previous versions, and has been slow at adding new features,as well as exploiting increases in computing power. For example, they changed G70/G71 to

G20/G21; they used parentheses for comments which caused difficulty when they introduced

mathematical calculations so they use square parentheses for macro calculations; they now have

nano technology recently in 32-bit mode but in the Fanuc 15MB control they introduced HPCC(high-precision contour control) which uses a 64-bit RISC processor and this now has a 500

 block buffer for look-ahead for correct shape contouring and surfacing of small block programs

and 5-axis continuous machining.

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This is also used for  NURBS to be able to work closely with industrial designers and the systems

that are used to design flowing surfaces. The NURBS has its origins from the ship building

industry and is described by using a knot and a weight as for bending steamed wooden planksand beams.

Contents

• 1 Common Codes

• 2 Example Program

• 3 See also

• 4 External links

Common Codes

G-codes are also called preparatory codes, and are any word in a CNC program that begins withthe letter 'G'. Generally it is a code telling the machine tool what type of action to perform, suchas:

• rapid move

• controlled feed move in a straight line or arc

• series of controlled feed moves that would result in a hole being bored, a workpiece cut

(routed) to a specific dimension, or a decorative profile shape added to the edge of aworkpiece.

• change a pallet

• set tool information such as offset.

There are other codes; the type codes can be thought of like registers in a computer 

X absolute positionY absolute position

Z absolute position

A position (rotary around X)B position (rotary around Y)

C position (rotary around Z)

U Relative axis parallel to XV Relative axis parallel to Y

W Relative axis parallel to ZM code (another "action" register or Machine code(*)) (otherwise referred to as a"Miscellaneous" function")

F feed rate

S spindle speed

 N line number R Arc radius or optional word passed to a subprogram/canned cycle

P Dwell time or optional word passed to a subprogram/canned cycle

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T Tool selection

I Arc data X axis

J Arc data Y axis.K Arc data Z axis, or optional word passed to a subprogram/canned cycle

D Cutter diameter/radius offset

H Tool length offset

(*) M codes control the overall machine, causing it to stop, start, turn on coolant, etc., whereasother codes pertain to the path traversed by cutting tools. Different machine tools may use the

same code to perform different functions; even machines that use the same CNC control.

• Partial list of M-Codes

M00=Program Stop (non-optional)M01=Optional Stop, machine will only stop if operator selects this option

M02=End of Program

M03=Spindle on (CW rotation)M04=Spindle on (CCW rotation)

M05=Spindle Stop

M06=Tool Change

M07=Coolant on (flood)M08=Coolant on (mist)

M09=Coolant off 

M10=Pallet clamp onM11=Pallet clamp off 

M30=End of program/rewind tape (may still be required for older CNC machines)

Common FANUC G Codes for Mill

Code Description

G00 Rapid positioning

G01 Linear interpolation

G02 CW circular interpolation

G03 CCW circular interpolation

G04 Dwell

G05.1 Q1. Ai Nano contour control

G05 P10000 HPCC

G07 Imaginary axis designation

G09 Exact stop check  

G10/G11 Programmable Data input/Data write cancel

G12 CW Circle Cutting

G13 CCW Circle Cutting

G17 X-Y plane selection

G18 X-Z plane selection

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G19 Y-Z plane selection

G20 Programming in inches

G21 Programming in mm

G28 Return to home position

G30 2nd reference point return

G31 Skip function (used for probes and tool length measurement systems)

G33 Constant pitch threading

G34 Variable pitch threading

G40 Tool radius compensation off  

G41 Tool radius compensation left

G42 Tool radius compensation right

G43 Tool offset compensation negative

G44 Tool offset compensation positive

G45 Axis offset single increase

G46 Axis offset single decrease

G47 Axis offset double increase

G48 Axis offset double decrease

G49 Tool offset compensation cancel

G50 Define the maximum spindle speed

G53 Machine coordinate system

G54 to G59 Work coordinate systems

G54.1 P1 to

P48Extended work coordinate systems

G73 High speed drilling canned cycle

G74 Left hand tapping canned cycle

G76 Fine boring canned cycleG80 Cancel canned cycle

G81 Simple drilling cycle

G82 Drilling cycle with dwell

G83 Peck drilling cycle

G84 Tapping cycle

G84.2 Direct right hand tapping canned cycle

G90 Absolute programming (type B and C systems)

G91 Incremental programming (type B and C systems)

G92 Programming of absolute zero point

G94/G95 Inch per minute/Inch per revolution feed (type A system) Note: Some CNCs usethe SI unit system

G96 Constant surface speed

G97 Constant Spindle speed

G98/G99 Return to Initial Z plane/R plane in canned cycle

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A standardized version of G-code known as BCL is used, but only on very few machines.

G-code files may be generated by CAM software. Those applications typically use translatorscalled post-processors to output code optimized for a particular machine type or family. Post-

 processors are often user-editable to enable further customization, if necessary. G-code is alsooutput by specialized CAD systems used to design printed circuit boards. Such software must be

customized for each type of machine tool that it will be used to program. Some G-code is written by hand for volume production jobs. In this environment, the inherent inefficiency of CAM-

generated G-code is unacceptable.

Some CNC machines use "conversational" programming, which is a wizard-like programming

mode that either hides G-code or completely bypasses the use of G-code. Some popular examples are Southwestern Industries' ProtoTRAK, Mazak's Mazatrol, Hurco's Ultimax and

Mori Seiki's CAPS conversational software.

Example Program

This is a generic program that demonstrates the use of G-Code to turn a 1" diameter X 1" long

 part. Assume that a bar of material is in the machine and that the bar is slightly oversized in

length and diameter and that the bar protrudes by more than 1" from the face of the chuck.

(Caution: This is generic, it might not work on any real machine! Pay particular attention to point5 below.)

Tool Path for program

Sample

Line Code Description

 N01 M216 Turn on load monitor  

 N02 G00 X20 Z20 Rapid move away from the part, to ensure the starting position of the tool N03 G50 S2000 Set Maximum spindle speed

 N04 M01 Optional stop

 N05 T0303 M6Select tool #3 from the carousel, use tool offset values located in line 3 of 

the program table, index the turret to select new tool

 N06G96 S854 M42M03 M08

Variable speed cutting, 854 ft/min, High spindle gear, Start spindle CWrotation, Turn the mist coolant on

 N07 G00 X1.1 Z1.1 Rapid feed to a point 0.1" from the end of the bar and 0.05" from the side

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 N08 G01 Z1.0 F.05 Feed in horizontally until the tool is standing 1" from the datum

 N09 X0.0 Feed down until the tool is on center - Face the end of the bar  

 N10 G00 Z1.1 Rapid feed 0.1" away from the end of the bar 

 N11 X1.0 Rapid feed up until the tool is standing at the finished OD

 N12 G01 Z0.0 F.05

Feed in horizontally cutting the bar to 1" diameter all the way to the

datum N13 M05 M09 Stop the spindle, Turn off the coolant

 N14 G28 G91 X0 Home X axis in the machine coordinate system, then home all other axes

 N15 M215 Turn the load monitor off  

 N16 M30Program stop, pallet change if applicable, rewind to beginning of the

 program

Several points to note:

1. There is room for some programming style, even in this short program. The grouping of 

codes in line N06 could have been put on multiple lines. Doing so may have made iteasier to follow program execution.2. Many codes are "Modal" meaning that they stay in effect until they are cancelled or 

replaced by a contradictory code. For example, once variable speed cutting had been

selected (G96), it stayed in effect until the end of the program. In operation, the spindle

speed would increase as the tool neared the center of the work in order to maintain aconstant cutting speed. Similarly, once rapid feed was selected (G00) all tool movements

would be rapid until a feed rate code (G01, G02, G03) was selected.

3. It is common practice to use a load monitor with CNC machinery. The load monitor willstop the machine if the spindle or feed loads exceed a preset value that is set during the

set-up operation. The job of the load monitor is to prevent machine damage in the event

of tool breakage or a programming mistake. On small or hobby machines, it can warn of a tool that is becoming dull and needs to be replaced or sharpened.

4. It is common practice to bring the tool in rapidly to a "safe" point that is close to the part

- in this case 0.1" away - and then start feeding the tool. How close that "safe" distance is,

depends on the skill of the programmer and maximum material condition for the rawstock.

5. If the program is wrong, there is a high probability that the machine will crash, or ram

the tool into the part under high power. This can be costly, especially in newer machiningcenters. It is possible to intersperse the program with optional stops (M01 code) which

allow the program to be run piecemeal for testing purposes. The optional stops remain in

the program but they are skipped during the normal running of the machine. Thankfully,most CAD/CAM software ships with CNC simulators that will display the movement of 

the tool as the program executes. Many modern CNC machines also allow programmers

to execute the program in a simulation mode and observe the operating parameters of themachine at a particular execution point. This enables programmers to discover semantic

errors (as opposed to syntax errors) before losing material or tools to an incorrect

 program. Depending on the size of the part, wax blocks may be used for testing purposes

as well.

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6. For pedagogical purposes, line numbers have been included in the program above. They

are usually not necessary for operation of a machine, so they are seldom used in industry.

However, if branching or looping statements are used in the code, then line numbers maywell be included as the target of those statements (e.g. GOTO N99).

MATLAB

For the subdistrict in Chandpur District, Bangladesh, see Matlab Upazila. For the computer 

algebra system, see MATHLAB.

MATLAB

MATLAB R2008a screenshot

Developer(s) The MathWorks

Stable release R2009a / 2009-03-06; 4 months ago

Written in C

Operating system Cross-platform[1] 

Type Technical computing

License Proprietary

Website MATLAB product page

MATLAB

Paradigm imperative

Appeared in late 1970s

Designed by Cleve Moler 

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Developer The MathWorks

Typing discipline dynamic

OS Cross-platform

MATLAB is a numerical computing environment and fourth generation programming language.Developed by The MathWorks, MATLAB allows matrix manipulation, plotting of functions and

data, implementation of algorithms, creation of user interfaces, and interfacing with programs in

other languages. Although it is numeric only, an optional toolbox uses the MuPAD symbolicengine, allowing access to computer algebra capabilities. An additional package, Simulink , adds

graphical multidomain simulation and Model-Based Design for dynamic and embedded systems.

In 2004, MathWorks claimed that MATLAB was used by more than one million people across

industry and the academic world.[2]

Contents

• 1 History

• 2 Syntax

o 2.1 Variables

o 2.2 Vectors/Matrices

o 2.3 Semicolon

o 2.4 Graphics

• 3 Object-Oriented Programming

• 4 Limitations

• 5 Interactions with other languages

•

6 Alternatives• 7 Release history

• 8 See also

• 9 References

• 10 Further reading

• 11 External links

History

MATLAB (meaning "matrix laboratory") was invented in the late 1970s by Cleve Moler , then

chairman of the computer science department at the University of New Mexico.[3] He designed itto give his students access to LINPACK  and EISPACK without having to learn Fortran. It soonspread to other universities and found a strong audience within the applied mathematics

community. Jack Little, an engineer, was exposed to it during a visit Moler made to Stanford

University in 1983. Recognizing its commercial potential, he joined with Moler and SteveBangert. They rewrote MATLAB in C and founded The MathWorks in 1984 to continue its

development. These rewritten libraries were known as JACKPAC.[citation needed ] In 2000, MATLAB

was rewritten to use a newer set of libraries for matrix manipulation, LAPACK [4]  .

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MATLAB was first adopted by control design engineers, Little's specialty, but quickly spread to

many other domains. It is now also used in education, in particular the teaching of linear algebra 

and numerical analysis, and is popular amongst scientists involved with image processing.[3]

Syntax

This article is written like a manual or guidebook . Please help rewrite this article from a

neutral point of view. (October 2008)

MATLAB, the application, is built around the MATLAB language. The simplest way to executeMATLAB code is to type it in at the prompt, >> , in the Command Window, one of the elements

of the MATLAB Desktop. In this way, MATLAB can be used as an interactive mathematical

shell. Sequences of commands can be saved in a text file, typically using the MATLAB Editor, asa script or encapsulated into a function, extending the commands available.[5]

Variables

Variables are defined with the assignment operator, =. MATLAB is dynamically typed, meaning

that variables can be assigned without declaring their type, except if they are to be treated as

symbolic objects[6], and that their type can change. Values can come from constants, from

computation involving values of other variables, or from the output of a function. For example:

>> x = 17

x =

17

>> x = 'hat'

x =

hat

>> x = [3*4, pi/2]

x =

12.0000 1.5708

>> y = 3*sin(x)

y =

-1.6097 3.0000

Vectors/Matrices

MATLAB is a "Matrix Laboratory", and as such it provides many convenient ways for creatingvectors, matrices, and multi-dimensional arrays. In the MATLAB vernacular, a vector refers to a

one dimensional (1× N or  N ×1) matrix, commonly referred to as an array in other programming

languages. A matrix generally refers to a 2-dimensional array, i.e. an m×n array where m and n

are greater than or equal to 1. Arrays with more than two dimensions are referred to as

multidimensional arrays.

MATLAB provides a simple way to define simple arrays using the syntax:init :increment :terminator . For instance:

>> array = 1:2:9

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array =

1 3 5 7 9

defines a variable named array (or assigns a new value to an existing variable with the name

array) which is an array consisting of the values 1, 3, 5, 7, and 9. That is, the array starts at 1

(the init value), increments with each step from the previous value by 2 (the increment value),

and stops once it reaches (or to avoid exceeding) 9 (the terminator value).

>> array = 1:3:9

array =

1 4 7

the increment value can actually be left out of this syntax (along with one of the colons), to use a

default value of 1.

>> ari = 1:5

ari =

1 2 3 4 5

assigns to the variable named ari an array with the values 1, 2, 3, 4, and 5, since the default

value of 1 is used as the incrementer.

Indexing is one-based[7], which is the usual convention for matrices in mathematics. This isatypical for programming languages, whose arrays more often start with zero.

Matrices can be defined by separating the elements of a row with blank space or comma and

using a semicolon to terminate each row. The list of elements should be surrounded by square

 brackets: []. Parentheses: () are used to access elements and subarrays (they are also used todenote a function argument list).

>> A = [16 3 2 13; 5 10 11 8; 9 6 7 12; 4 15 14 1]

A =

16 3 2 13

5 10 11 8

9 6 7 12

4 15 14 1

 

>> A(2,3)

ans =

11

Sets of indices can be specified by expressions such as "2:4", which evaluates to [2, 3, 4]. For 

example, a submatrix taken from rows 2 through 4 and columns 3 through 4 can be written as:

>> A(2:4,3:4)

ans =

11 8

7 12

14 1

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A square identity matrix of size n can be generated using the function eye, and matrices of any

size with zeros or ones can be generated with the functions zeros and ones, respectively.

>> eye(3)

ans =

1 0 0

0 1 00 0 1

>> zeros(2,3)

ans =

0 0 0

0 0 0

>> ones(2,3)

ans =

1 1 1

1 1 1

Most MATLAB functions can accept matrices and will apply themselves to each element. For example, mod(2*J,n) will multiply every element in "J" by 2, and then reduce each element

modulo "n". MATLAB does include standard "for" and "while" loops, but using MATLAB's

vectorized notation often produces code that is easier to read and faster to execute. This code,excerpted from the function magic.m, creates a magic square M for odd values of n (MATLAB

function meshgrid is used here to generate square matrices I and J containing 1:n).

[J,I] = meshgrid(1:n);

A = mod(I+J-(n+3)/2,n);

B = mod(I+2*J-2,n);

M = n*A + B + 1;

Semicolon

Unlike many other languages, where the semicolon is used to terminate commands, in MATLAB

the semicolon serves to suppress the output of the line that it concludes.

Graphics

Function plot can be used to produce a graph from two vectors x and y. The code:

x = 0:pi/100:2*pi;

y = sin(x);

plot(x,y)

 produces the following figure of the sine function:

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Three-dimensional graphics can be produced using the functions surf , plot3 or mesh.

[X,Y] = meshgrid(-10:0.25:10,-10:0.25:10);

f = sinc(sqrt((X/pi).^2+(Y/pi).^2));

mesh(X,Y,f);

axis([-10 10 -10 10 -0.3 1])

xlabel('{\bfx}')

ylabel('{\bfy}')

zlabel('{\bfsinc} ({\bfR})')

hidden off

 

[X,Y] = meshgrid(-10:0.25:10,-10:0.25:10);

f = sinc(sqrt((X/pi).^2+(Y/pi).^2));

surf(X,Y,f);

axis([-10 10 -10 10 -0.3 1])

xlabel('{\bfx}')

ylabel('{\bfy}')

zlabel('{\bfsinc} ({\bfR})')

This code produces a wireframe 3D plot of thetwo-dimensional unnormalized sinc function:

 This code produces a surface 3D plot of thetwo-dimensional unnormalized sinc function:

 

Object-Oriented Programming

MATLAB's support for object-oriented programming includes classes, inheritance, virtual

dispatch, packages, pass-by-value semantics, and pass-by-reference semantics.[8]

classdef hello

methods

function doit(this)

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disp('hello')

end

end

end

When put into a file named hello.m, this can be executed with the following commands:

>> x = hello;

>> x.doit;

hello

Limitations

For a long time there was criticism that because MATLAB is a proprietary  product of The

MathWorks, users are subject to vendor lock-in.[9][10] Recently an additional tool called theMATLAB Builder under the Application Deployment tools section has been provided to deploy

MATLAB functions as library files which can be used with .NET or  Java application building

environment. But the drawback is that the computer where the application has to be deployedneeds MCR (MATLAB Component Runtime) for the MATLAB files to function normally. MCR 

can be distributed freely with library files generated by the MATLAB compiler.

MATLAB, like Fortran, Visual Basic and Ada, uses parentheses, e.g. y = f(x), for both

indexing into an array and calling a function. Although this syntax can facilitate a switch between a procedure and a lookup table, both of which correspond to mathematical functions, a

careful reading of the code may be required to establish the intent.

Many functions have a different behavior with matrix and vector arguments. Since vectors are

matrices of one row or one column, this can give unexpected results. For instance, function

sum(A) where A is a matrix gives a row vector containing the sum of each column of A, andsum(v) where v is a column or row vector gives the sum of its elements; hence the programmer 

must be careful if the matrix argument of sum can degenerate into a single-row array.[11] While

sum and many similar functions accept an optional argument to specify a direction, others, like

plot,[12] do not, and require additional checks. There are other cases where MATLAB's

interpretation of code may not be consistently what the user intended [citation needed ] (e.g. how spacesare handled inside brackets as separators where it makes sense but not where it doesn't, or 

 backslash escape sequences which are interpreted by some functions like fprintf but not

directly by the language parser because it wouldn't be convenient for Windows directories). Whatmight be considered as a convenience for commands typed interactively where the user can

check that MATLAB does what the user wants may be less supportive of the need to construct

reusable code.[citation needed ]

Array indexing is one-based which is the common convention for matrices in mathematics, but

does not accommodate any indexing convention of sequences that have zero or negative indices.

For instance, in MATLAB the DFT (or FFT) is defined with the DC component at index 1

instead of index 0, which is not consistent with the standard definition of the DFT in anyliterature. This one-based indexing convention is hard coded into MATLAB, making it difficult

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for a user to define their own zero-based or negative indexed arrays to concisely model an idea

having non-positive indices.

Code written for a specific release of MATLAB often does not run with earlier releases as it mayuse some of the newer features. To give just one example: save('filename','x') saves the

variable x in a file. The variable can be loaded with load('filename') in the same MATLABrelease. However, if saved with MATLAB version 7 or later, it cannot be loaded with MATLABversion 6 or earlier. As workaround, in MATLAB version 7 save('filename','x','-v6')

generates a file that can be read with version 6. However, executingsave('filename','x','-v6') in version 6 causes an error message.

Interactions with other languages

MATLAB can call functions and subroutines written in the C programming language or Fortran.

A wrapper function is created allowing MATLAB data types to be passed and returned. The

dynamically loadable object files created by compiling such functions are termed "MEX-files"

(for MATLAB executable). [13][14]

Libraries written in Java, ActiveX or  .NET can be directly called from MATLAB and many

MATLAB libraries (for example XML or SQL support) are implemented as wrappers around

Java or ActiveX libraries. Calling MATLAB from Java is more complicated, but can be donewith MATLAB extension[15], which is sold separately by MathWorks.

Through the MATLAB Toolbox for Maple, MATLAB commands can be called from within the

Maple Computer Algebra System, and vice versa.

AlternativesMATLAB has a number of competitors.

There are free open source alternatives to MATLAB, in particular GNU Octave, FreeMat, and

Scilab which are intended to be mostly compatible with the MATLAB language (but not the

MATLAB desktop environment). Among other languages that treat arrays as basic entities (array programming languages) are APL and its successor J, Fortran 95 and 2003, as well as the

statistical language S (the main implementations of S are S-PLUS and the popular open source

language R ).

There are also several libraries to add similar functionality to existing languages, such as PerlData Language for Perl and SciPy together with NumPy and Matplotlib for Python.

See also: list of numerical analysis software and comparison of numerical analysis software

Release history

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version[16] release name Year

MATLAB 1.0 R? 1984

MATLAB 2 R? 1986

MATLAB 3 R? 1987MATLAB 3.5 R? 1990

MATLAB 4 R? 1992

MATLAB 4.2c R7 1994

MATLAB 5.0 R8 1996

MATLAB 5.1 R9

MATLAB 5.1.1 R9.11997

MATLAB 5.2 R10

MATLAB 5.2.1 R10.1 1998

MATLAB 5.3 R11

MATLAB 5.3.1 R11.11999

MATLAB 6.0 R12 2000

MATLAB 6.1 R12.1 2001

MATLAB 6.5 R13 2002

MATLAB 6.5.1 R13SP1

MATLAB 6.5.2 R13SP22003

MATLAB 7 R14

MATLAB 7.0.1 R14SP12004

MATLAB 7.0.4 R14SP2

MATLAB 7.1 R14SP32005

MATLAB 7.2 R2006a

MATLAB 7.3 R2006b2006

MATLAB 7.4 R2007aMATLAB 7.5 R2007b

2007

MATLAB 7.6 R2008a

MATLAB 7.7 R2008b2008

MATLAB 7.8 R2009a 2009