CNC MACHINE COORDINATE SYSTEM

 Nearly all CNC machine uses a Cartesian coordinate system based on an X, Y, and Z-axis. This system allows a machine to move in a specific direction along a specific plane.

#1   How CNC machines are classified based on control system features?

    ''Classified by the servo system, it can be divided into open-loop control system, semi-closed loop control system and closed-loop control system. Open-loop control system means that there is no detection and feedback device''

#2   What does a coordinate code communicate to a CNC machine?

    ''G codes describe the operation that the machine will perform. X, Y, and Z codes determine the cutting operation location. F and S codes set the feed and speed, T codes signal the correct cutting tool, and M codes complete other miscellaneous functions''

                                         CNC MILLING COORDINATE SYSTEM

                                                       2 SLOT  AND 4 HOLLS

PROGRAM NO. 1

 O0003

 N01G90G21M03S1000

 N02G01X20Y20Z5F.25

 N03G01Z-5

 N04G01Z10

 N05G01X20Y80

 N06G01Z-5

 N07G01Z10

 N08G01X80Y20              

 N09G01Z-5

 N10G01Z10

 N11G01X80Y80

 N12G01Z-5

 N13G01Z10

 N14G01X40Y40

 N15G01Z-5

 N16G01X50Y40

 N17G01X50Y80

 N18G01X40Y80

 N19G01X40Y40

 N20G01Z10

 N21G01X60Y40

 N22G01Z-5

 N23G01X70Y40

 N24G01X70Y80

 N25G01X60Y80

 N26G01X60Y40

 N27 Z10 

 M30

PROGRAM NO. 2

  

                ANGLE HOLL CUTTING 

O0011

N01G90G21M03S1000

N02G16F2.00

N03G00X30Y0Z10

N04G01Z-5

N05G01Z10

N06G01X30Y30

N07G01Z-5

N08G01Z10

N09G01X30Y60

N10Z-5

N11G01Z10

N12G01X30Y90

N13Z-5

N14Z10

N15X0Y0

N16Z-5

M30

     

                                           CNC Turning coordinate system

Program No. 1

O0007

N01G90G21

N02U0W0M03S1000

N03G00X0Z0

N04G01X30Z0

N05G01X30Z-20

N06G03X35Z-30R10

N07G03X40Z-50R20

N08G03X50Z-70R20

N09G03X60Z-90R20

N10G03X70Z-110R20

N11G03X80Z-130R20

N12G01X80Z-180

M05

M02

Program No. 2

O0008

N01G90G21

N02U0W0M03S1000

N03G00X0Z0

N04G01X30Z0

N05G01X30Z-20

N06G02X40Z-40R20

N07G01X40Z-50

N08G03X50Z-60R10

N09G01X50Z-80

N10G03X60Z-90R10

N11G01X60Z-140

N12G02X70Z-160R20

N13G01X70Z-200

M05

M02

Program No. 3

O0009

N01G90G21

N02U0W0M03S1000

N03G00X0Z0

N04G01X20Z0

N05G01X20Z-10

N06G03X30Z-20R10

N07G01X30Z-40

N08G01X40Z-40

N09G01X40Z-60

N10G02X50Z-70R10

N11G01X50Z-90

N12G02X60Z-100R10

N13G01X60Z-110

N14G02X70Z-120R10

N15G01X70Z-140

N16G03X80Z-150R10

N17G01X80Z-170

N18G02X90Z-180R10

N19G01X90Z-200

N20G03X100Z-210R10

N21G01X100Z-250

M02

M05

CNC Turning Coordinate System

Nearly all CNC machine uses a Cartesian coordinate system based on an X, Y, and Z-axis. This system allows a machine to move in a specific direction along a specific plane. Reduce the Cartesian system to its basics, and you have a familiar number line. One point on the line gets designated as the Origin.

 1.  What are the 3 coordinate systems?

   

   There are three commonly used coordinate systems: Cartesian, cylindrical and spherical. In this chapter, we will describe a Cartesian coordinate system and a cylindrical coordinate system.

Coordinate system

A CNC program describes the work piece outline by indication of points in a coordinate system. Usually a right-hand coordinate system is used, but in certain cases also indication of polar coordinates can be used. Since turning acts with rotationally symmetric parts (mathematical: Volume body, which will be get through rotation of a piece of curve around an axle), a two-dimensional execution is sufficient. The X-axis shows in direction of the across support, the Z-axis coincides with the axis of rotation of the main spindle.

Machine zero point

The feed axles in along and transverse direction build the Machine coordinate (coordination) system. The machine zero point is given by the manufacturer and normally lies on the spindle axle at height of the chuck admission. To this coordinate system refers the control with its instructions.

Workpiece coordinate system

In a manufacturing drawing the zero point is on the reference element. That can be a front surface and the axis of rotation for e.g. So that one does not have to convert the dimensions during numerical control programming to the Machine coordinate system, one can determine a new workpiece zero point in the coordinate system by a zero shift (e.g. G54), to which all following data refer. This workpiece coordinate system can be selected by the operator freely and makes the simple conversion possible of drawing data to a NC-Program possible.

Absolute measure- Incremental measure

Coordinate data as absolute data refer to the zero point (e.g. move to the point X = 40mm Z =-50mm). The X-value indicates the diameter.

With an indication of incremental measure the values refer to the current position (e.g. move - 30 mm in Z-direction). In this case the X-value indicates the actual length of movement X-1 means a diameter reduction of two millimetres.

Tools

Since there are turning tools of most diverse kind, the control must get all relevant data for the work. Common denominator of all tools is the tool adjusting point. It is at the notice surface of the tool holder and coincides when inserting into the tool chuck with the tool reference point (see up). The control takes this point for the calculation of the tool movement.

In order to consider now the different tool dimensions now, a correction value memory is assigned to each tool in the computer of the machine, which contains the distances of the chisel point of the tool reference point. These values are measured either before the job or determined by a sample manufacturing. The length of the tool is the distance in Z-direction (lengthwise to the spindle axle).  The transverse value of the tool is the distance in X-direction (transverse to the spindle axle). In addition the control needs the radius of the cutting edge and the work quadrant for the calculation of the radius correction.

For the production of a workpiece several different tools are usually needed. A tool magazine or a tool turret makes it possible to equip the machine with several preset tools. In the NC-Program the needed tool with it`s stored correction values will be called by the magazine number.

CNC Program structure

Program structure A NC-Program consists of individual sentences. These consist of individual words, which divide themselves in address and value. A sentence contains usually several words.

Frequent addresses:: 

N

record number

G

way conditions (circle, straight lines, rapid traverse)

X

X- coordinate endpoint

Z

Z-coordinate endpoint

F

feed rate

S

spindle speed

T

tool number

M

machine function

 

Some instructions apply only to the sentence, in which they are programmed. In addition, there are some which are valid over several sentences. The instruction “G00” (rapid traverse), e.g. is so long valid, until it is overwritten by another instruction. One speaks then of a modal effective instruction.

Work Coordinate Systems

For a coordinate system to be useful, the programmer must be able to assign the origin to a convenient place relative to the part to be machined. To define the work coordinate system origin, the programmer can position the the machine to the desired point and tell the machine that the position it is currently in should be the work origin.

The position of the work coordinate systems are often stored in an “offset register” or “offset screen.” Most machines can accommodate several different coordinate systems. The programmer can ask the machine to use one of the work coordinate systems by specifying, for example, G54.

Enabling G54 through G59 is a common way to specify a specific work coordinate system. To specify the origin of, for example, G54, the operator would use an edgefinder or other probe to position the spindle over the desired origin (see below).

GUNS

MAXIM MACHINE GUN

 In 1884, Hiram Maxim built the first effective machine gun, which revolutionized warfare. Born in 1840 in sangers Ville, Maine, Maxim was apprenticed at 14 to a carriage maker. While learning that trade, he exhibited a knack for invention, designing a mousetrap that automatically reset and rid local mills of rodents.

                                     

machine gun, automatic weapon of small caliber that is capable of sustained rapid fire. Most machine guns are belt-fed weapons that fire from 500 to 1,000 rounds per minute and will continue to fire as long as the trigger is held back or until the supply of ammunition is exhausted. The machine gun was developed in the late 19th century and has profoundly altered the character of modern warfare.

Modern machine guns are classified into three groups. The light machine gun, also called the squad automatic weapon, is equipped with a bipod and is operated by one soldier; it usually has a box-type magazine and is chambered for the small-calibre, intermediate-power ammunition fired by the assault rifles of its military unit. The medium machine gun, or general-purpose machine gun, is belt-fed, mounted on a bipod or tripod, and fires full-power rifle ammunition. Through World War II the term “heavy machine gun” designated a water-cooled machine gun that was belt-fed, handled by a special squad of several soldiers, and mounted on a tripod. Since 1945 the term has designated an automatic weapon firing ammunition larger than that used in ordinary combat rifles; the most widely used calibre is .50 inch or 12.7 mm, although a Soviet heavy machine gun fired a 14.5-millimetre round.

History-:

Multi-shot weapons have a long history of development, going as far back as the first century, with plans for a multi-shot arrow gun by Greek engineer Hero of Alexandria. Leonardo Da Vinci devised plans for one in the 1400s.

The Chinese had some success with creating a repeating crossbow. The most common model, the Zhuge Nu (better known in the West as the Chu-ko-nu), is typically attributed to second- and third-century strategist Zhuge Liang, who developed it for the Kingdom of Shu during the Three Kingdoms period. However, a buried library in the ancient state of Chu indicates that some sort of repeating crossbow had at the very least been designed in the third century B.C.E.

Some weapons with machine gun-like traits appeared as early as the 1700s. However, it was not until the mid-nineteenth century that successful machine-gun designs came into existence. The key characteristics of modern machine guns—their relatively high rate of fire and automatic loading—came with the Model 1862 Gatling gun, which was adopted by the United States Navy. These weapons were still powered by hand. This situation, however, changed with Hiram Maxim's idea of harnessing recoil energy to power reloading in his Maxim machine gun. Dr. Gatling also experimented with electric-motor-powered models; this externally powered machine reloading has seen use in modern weapons as well. The Vandenburg and Miltrailleuse volley (organ) gun concepts have been revived partially in the early twenty first century in the form of electronically controlled, multibarreled volley guns.

It is important to note that what exactly constitutes a machine gun, whether volley guns are a type of machine gun, and to what extent some earlier types of devices are considered machine guns, are matters of debate. The answers can vary depending on which language and exact definition is used.

Early rapid-firing weapons:-

One of the first known ancestors of multi-shot weapons was created by James Pickle, a London lawyer, who patented what he called "The Pickle Gun" on May 15, 1718. It was a design for a 1 inch (in.) (25.4 mm) caliber, flintlock revolver cannon able to fire 9 rounds before reloading, intended for use on ships. According to Pickle, it was able to fire round bullets at Christians and square bullets at Turks. Although ahead of its time, foreshadowing the designs of revolvers, it was not adopted or produced.

In the early and mid-nineteenth century, a number of rapid-firing weapons appeared which offered multi-shot fire, and a number of semi-automatic weapons as well as volley guns. Volley guns (such as the Mitrailleuse) and double barreled pistols relied on duplicating all parts of the gun. Pepperbox pistols did away with needing multiple hammers but used multiple barrels. Revolvers further reduced this to only needing a pre-prepared magazine using the same barrel and ignitions. However, like the Pickle gun, they were still only semiautomatic.

The coffee-mill gun of the Civil War featured both automatic loading and single barrel, only separated functionally from the modern machine gun by being hand-powered rather than using cartridges.

TOP SHOT HOTKISS 

The Gatling gun, patented in 1861 by Richard Jordan Gatling, was the first to offer controlled, sequential automatic fire with automatic loading. The design's key features were machine loading of prepared cartridges and a hand-operated crank for sequential high-speed firing. It first saw very limited action in the American Civil War and was subsequently improved. Many were sold to other armies in the late 1800s and continued to be used into the early 1900s, until they were gradually supplanted by Maxim guns. The Gatling's were the first widely used rapid-fire guns and, due to their multiple barrels, could offer more sustained fire than the first generation of air-cooled, recoil-operated machine guns. The weight, complexity, and resulting cost of the multibaric design meant recoil-operated weapons, which could be made lighter and cheaper, would supplant them. It would be another 50 years before the concept was again used to allow extremely high rates of fire, such as in miniguns, and automatic aircraft cannons.

Interwar era and World War II :-

During the interwar years, many new designs were developed, such as the Browning M2 .50 caliber (12.7 mm) in 1933, which, along with others, were used in World War II. The trend toward automatic rifles, lighter machine guns, and more powerful submachine guns resulted in a wide variety of firearms that combined characteristics of an ordinary rifle and a machine guns. The Cei-Rigotti (1900s), Fedorov Avtomat (1910s), AVS-36 Simonov (1930s), MP44, M2 Carbine, AK-47, and AR-15 have come to be known as assault rifles (after the German term sturmgewehr). Many aircraft were equipped with machine cannons, and similar cannons (nicknamed "Pom-pom guns") were used as antiaircraft weapons. The designs of Bofors of Sweden were widely used by both sides and have greatly influenced similar weapons developed since then.

Germany developed during the interwar years the first widely-used and successful general-purpose machine gun, the Maschinengewehr 34, which inspired many modern machine gun developments. The later Maschinengewehr 42 was feared during WWII by Allied forces as it was capable of firing at a rate of 1200-1800 RPM with pauses of only a few seconds to replace the quick-change barrel when operated by experienced soldiers. The successor of the MG42, the MG3, is still today in use in the German army. Many modern machine guns are derived from the MG42.

Modern era :-

The Cold War era saw mostly a refinement of weapon types in the form of lower weight and higher reliability. The semi-automatic rifles of World War II vintage were almost totally replaced by lighter assault rifles such as the M16 and Soviet AK-47. Infantry adopted general-purpose machine guns like the American M60 for squad use, using air cooling for lighter weight. Heavy machine guns were retained for ground vehicles and fortifications. For aircraft use, even heavy machine guns proved to lack killing power in the air-to-air role, and by the late 1950s fighter aircraft armament had almost totally switched to automatic cannons. Machine guns, with lower recoil, remained popular for helicopters and for ground attack aircraft, supplemented by new Gatling-style, electric multibarrel weapons like the American Minigun. In police, special operations, and other paramilitary roles, smaller automatic weapons, including light submachine guns and machine pistols, proliferated, many relying on ubiquitous pistol rounds.

The last major use of a manual machine gun, was a manual grenade machine gun during the 1970s used on river boats in the Vietnam Conflict. The manual type, the Mk 18 Mod 0 was replaced by fully automatic ones such as the Mk 19 grenade launcher.

Types of machine guns :-

There are two main definitions of the upper limit of caliber for machine guns:

caliber larger than 12.7 millimeter (mm) (.50 caliber)

caliber larger than 20 mm

Larger-caliber automatic weapons are generally referred to as autocannons. In between, there are weapons that have been called by either name depending on other traits; for instance, there have been weapons of roughly 15 mm that were variably referred to as autocannons and machine guns.

Another factor is whether the weapon fires conventional rounds or explosive rounds. Automatic weapons firing large-caliber explosive rounds are generally either autocannons or automatic grenade launchers ("grenade machine guns"). Machine guns tend to share a very high ratio of barrel length to caliber (a long barrel for a small caliber).

There have been two main machine gun eras: The era of manual machine guns and the era of automatic machine guns. The technical development itself is marked by a series of developments of specific automatic features, as well as technical developments (such as linked ammunition). The era of manual multi-shot devices extends back hundreds of years (such as manual volley guns), but the development of manual and automatic machine guns takes place almost entirely in the latter half of the 1800s. Manual machine guns are manually-powered; for instance, a crank must be turned to power reloading and firing, as opposed to simply holding down a trigger, as with automatic machine guns. There are many other notable features, but this is one of the most significant, allowing the higher rates of fire common to machine guns.

Manual machine guns, as well as manual volley guns, saw their first major use in the American Civil War. The Gatling gun and "coffee gun" both used manually-powered automatic loading, fed via a hopper filled with cartridges. The Gatling gun—a manually-powered rotary machine gun—would be the major type of the late nineteenth century, though there were many other manual designs used to varying degrees (for instance, the Nordenfelt machine gun). The first automatic machine gun was the recoil-operated Maxim gun, which used linked (belt) ammunition, as well as a single barrel and automatic loading. This concept of using bullet energy would also drive the development of nearly all other semi and fully automatic firearms of the twentieth century.

The two major operation systems of modern automatic machine guns are gas operation (which uses the gas generated from the burning powder to cycle the action), or recoil operation (which uses the recoil generated from the ejecting bullet to cycle the action). The first gas-operated machine gun was the Colt-Browning M1895. Another (minor) type is the externally-powered machine gun. Rather than human manual power or bullet energy, a third source (such as an electric motor) is used; these types are now called by more specific names (see Minigun, Chaingun). The most common type of modern machine gun remains the automatic, recoil-operated, and belt-fed type. Electric and Gatling-type machine guns are common on combat aircraft and other vehicles.

Overview of modern automatic machine guns :-

Unlike semi-automatic firearms, which require one trigger pull per bullet fired, a machine gun is designed to fire rounds as long as the trigger is held down and ammunition is fed into the weapon. Although the term "machine gun" is often used by civilians to describe all fully automatic weapons, the military use of the term is restricted to relatively heavy weapons fired from some sort of support rather than hand-held, able to provide continuous or frequent bursts of automatic fire for as long as ammunition lasts. Machine guns are normally used against unprotected or lightly-protected personnel, or to provide suppressive fire.

Some machine guns have in practice maintained suppressive fire almost continuously for hours; other automatic weapons overheat after sometimes less than a minute of use. Because they become very hot, practically all machine guns fire from an open bolt, to permit air cooling from the breech between bursts. They also either have a barrel cooling system, or a removable barrels which allow a hot barrel to be replaced.

Although subdivided into "light," "medium," "heavy," or "general purpose," even the lightest machine guns tend to be substantially larger and heavier than other automatic weapons. Squad automatic weapons (SAWs) are a variation of light machine guns and only require one operator (sometimes with an assistant to carry ammunition). Medium and heavy machine guns are either mounted on a tripod or on a vehicle; when carried on foot, the machine gun and associated equipment (tripod, ammunition, spare barrels) require additional crew members.

The majority of machine guns are belt-fed, although some light machine guns are fed from drum or box magazines, and some vehicle-mounted machine guns are hopper-fed.

Other automatic weapons are subdivided into several categories based on the size of the bullet used, and whether the cartridge is fired from a positively locked closed bolt, or a non-positively locked open bolt. Fully automatic firearms using pistol-caliber ammunition are called machine pistols or submachine guns (largely on the basis of size); selective fire rifles firing a full-power rifle cartridge from a closed bolt are called automatic rifles, while those using a reduced-power rifle cartridge are called assault rifles.

Assault rifles are a compromise between the pistol caliber submachine gun and a traditional rifle firing a full-power cartridge, allowing semi-automatic, burst, and full-automatic fire options (selective fire). The modern legal definition of "assault rifle" is of significance in states like California, where according to state law, certain short, small-caliber, semi-automatic weapons are considered to be "assault weapons" and are thus illegal. Supporters of gun rights generally consider the use of the phrase "assault weapon" to be pejorative when used to describe these civilian firearms, and this term is seldom used outside of the United States in this context.

The machine gun's primary role in ground combat is to provide suppressive fire on the oposition's position, forcing the enemy to take cover and reducing the effectiveness of enemy fire. This either halts an enemy attack or allows friendly forces to attack enemy positions with less risk.

Light machine guns usually have simple iron sights. A common aiming system is to alternate solid ("ball") rounds and tracer ammunition rounds (usually one tracer round for every four ball rounds), so shooters can see the trajectory and "walk" the fire into the target, as well as direct the fire of other soldiers.

Many heavy machine guns, such as the Browning M2 .50 caliber machine gun, are accurate enough to engage targets at great distances. During the Vietnam War, Carlos Hathcock set the record for a long-distance shot at 7382 feet (2250 meters) with a .50 caliber heavy machine gun he had equipped with a telescopic sight. This led to the introduction of .50 caliber anti-material sniper rifles, such as the Barrett M82.

Components :-

All machine guns require the following components:

A feed system to load the chamber. Cartridges can be fed into the chamber by a variety of methods, the most common being magazines or ammunition belts.

A trigger mechanism to fire the round. This includes the actual trigger, a trigger sear to catch the bolt, a bolt and a firing pin, as well as other components. Typically, the act of pulling the trigger causes something to strike the primer on the round in the chamber and disengages the sears. This allows continual cycling of the bolt until the trigger is released. A sear then grabs the bolt or firing pins. This stops the machine gun at some point in its cycle.

An extractor system to eject the spent or misfired cartridge. Usually this is fairly simple. A pin on the side of the bolt catches a ridge on the cartridge and flicks it out an ejection port.

These components form a mechanism which must be powered. If powered by absorbing the recoil of a cartridge, it is called recoil-operated. If powered by the expanding gases of a fired cartridge, it is called gas actuated. If powered by an external force, such as a motor, it is usually called a chain gun.

Operation :-

All machine guns follow a cycle:

Removing the spent cartridge through an ejection port

Cocking the trigger mechanism so the weapon can be fired again

Loading the next round into the firing chamber. Usually spring tension or a cam forces the new round and bolt back into the firing chamber

A mechanism makes the firing pin fire the cartridge, activating the ejection and reloading steps. The cycle repeats. This full cycle takes a fraction of a second and can thus occur many times per second. The operation is basically the same, regardless of the means of activating these mechanisms. Some examples:

Machine pistols and submachine guns (like the World War II "grease gun," MAC-10, or the Uzi) are usually blowback operated.

Most assault rifles and squad automatic weapons are gas actuated. Some weapons, such as the AR-15/M16, integrate the piston with the bolt. Others, such as the AR18 and AK patterns, attach the piston to a bolt carrier that unlocks and operates the bolt.

A recoil-actuated machine gun uses the recoil to first unlock and then operate the action. Heavy machine guns, such as the M2 .50 and Browning .50, are this type. These can be recognized by a large cocking lever needed to feed the first round.

An externally actuated machine gun uses an external power source, such as an electric motor or even a hand crank to move its mechanism through the firing sequence. Most modern weapons of this type are called chain guns in reference to their driving mechanism. Gatling guns and revolver cannon have several barrels or chambers on a rotating carousel and a system of cams that load, cock, and fire each mechanism progressively as it rotates through the sequence. The continuous nature of the rotary action allows for an incredibly high cyclic rate of fire, often several thousand rounds per minute. Not all chain guns use multiple barrels or chambers, though. Chain guns are less prone to jamming than a gun operated by gas or recoil, as the external power source will eject misfired rounds with no further trouble. This is not possible if the force needed to eject the round comes from the round itself. Chain guns are generally used with large shells, 20 mm in diameter or more, though some, such as the M134 minigun, fire smaller cartridges. They offer benefits of reliability and firepower, though the weight and size of the power source and driving mechanism makes them impractical for use outside of a vehicle or aircraft mount.

Heavy machine guns are often water cooled or have interchangeable barrels, which must be changed periodically to avoid overheating. The higher the rate of fire, the more often barrels must be changed and allowed to cool. To minimize this, most air-cooled guns are fired only in short bursts or at a reduced rate of fire.

Not all machine guns strike the primer in the same way. In blowback machine guns, the act of seating the round also fires the round. In gas operated and recoil-operated guns, a separate step in the firing sequence is needed to strike the round. In a progressive-fire gun, the firing pin is cycled by cams. In some automatic cannon, the primer is fired electrically.

U.S. Marines and their M240G at Camp Hansen, Okinawa

In weapons where the round seats and fires at the same time, mechanical timing is essential for operator safety, to prevent the round from firing before it is seated properly. This is especially important in weapons like the 40 mm grenade launcher, where high explosives are present in the rounds being fired.

Machine guns are controlled by one or more mechanical sears. When a sear is in place, it effectively stops the bolt at some point in its range of motion. Some sears stop the bolt when it is locked to the rear. Other sears stop the firing pin from going forward after the round is locked into the chamber.

Almost all weapons have a "safety" sear, which simply keeps the trigger from engaging .

Future development :-

Conventional machine-gun development has been slowed by the fact that existing machine-gun designs are adequate for most purposes, although significant developments are taking place with regard to anti-armor and antimissile weapons.

Electronically controlled machine guns with ultrahigh rates of fire, like Metal Storm's weapons may see use in some applications, although current small-caliber weapons of this type have found little use: They are too light for anti-vehicle use, but too heavy (especially with the need to carry a tactically useful amount of ammunition) for individual soldiers. The trend towards higher reliability and lower mass for a given power will likely continue. Another example, the six barreled, 4000 round per minute, XM214 minigun "six pack" developed by General Electric, has complex machinery, weighs 85 pounds, and has very little penetration power to show for it.

Human interface :-

The most common interface on machine guns is a pistol grip and trigger. On earlier manual machine guns, the most common type was a hand crank. On externally powered machine guns, such as miniguns, an electronic button or trigger on a joystick is commonly used. Lighter machine guns often have a butt stock attached, while mounted and tripod mounted machine guns usually have spade grips. In the late twentieth century, scopes and other complex optics became more common as opposed to just iron sights.

Loading systems in early manual machine guns were often from a hopper of loose (un-linked) cartridges. Manual volley guns usually had to be reloaded manually all at once (each barrel reloaded by hand). With hoppers, the rounds could often be added while the weapon was firing. This gradually changed to belt-fed types. Belts were either held in the open by the person, or in a bag or box. Some modern vehicle machine guns used linkless feed systems however.

Closeup of M2. This machine gun is part complex armament subsystem;it is aimed and fired from the aircraft rather than directly

Modern machine guns are usually mounted in one of four ways. The first is a bipod- often these are integrated with the weapon. This is common on light machine guns and also medium machine guns. Another major way is with a larger tripod, which can stand on its own. Medium and heavy usually use tripods. On ships and aircraft, machine guns are usually mounted on a pintle mount—essentially a steel post that is connected to the frame. Tripod and pintle mounts are usually used with spade grips. The last major way is disconnected from humans, as part of an armament system, such as a tank coaxial or part of an aircraft. These are usually electrically fired and have complex sighting systems.

What is the deadliest machine gun?

                                         The 5 Deadliest Machine Guns of World War I

1. Germany: Maschinengewehr 08.

2. France: Hotchkiss M1909 Benét–Mercié Machine Gun. 

3. Great Britain: Vickers Machine Gun.

4. Russian: Maxim M1910 Machine Gun.

5. United States: Browning M1917.

 (Germany: Maschinengewehr 08.)

MG 08

The Deutsches Heer, German army, wants to adapt for its infantry the machine-gun MG 99 developed by Maxim in 1899 and used by the Imperial Navy, as well as the MG 01. Technical evolutions aimed in particular to lighten the weight of the weapon give Birth in 1908 to a new model that is selected.

Made of steel, this machine-gun manufactured by Maxim is water-cooled and has a firing rate of up to 500 rounds per minute. The tank contains four liters of water, which is enough for a shot of 2,000 to 2,500 rounds.

Widely used during the First World War, it is particularly robust but has a major flaw: the water vapor released by the overheating of the radiator indicates very clearly the position of the shooter, especially in winter. The new model was renamed in 1915 (including the reduction in weight due to repeated requests from the infantry). The new model is called MG 08/15 and is one of the first German light machine guns. A flame arrester is added to the MG 08 from 1916.

During the period between the wars, no fewer than 17 foreign armies bought this machine gun, especially from Belgium, the Netherlands and Yugoslavia. Copied by Great Britain, the United States and Russia, the MG 08 is also manufactured by China under the name Type 24.

When the Second World War broke out in Europe, this machine gun was particularly aging. However, it remains in a fixed position, particularly along the Atlantic Wall support points.

MG 08 machine gun specification :-

Creator/User: Germany

Denomination: MG 08

Fire mode: automatic

Caliber: 7.65×53mm

Feed system: 250-round fabric belt

Rate of fire: 550 rounds/min

Gun body weight: 26.4 kg

Loaded weight: 69 kg

Length: 118 cm

Barrel length: 68 cm

(France: Hotchkiss M1909 Benét–Mercié Machine Gun)

The Hotchkiss M1909 machine gun was a French designed light machine gun of the early 20th century, developed and built by Hotchkiss et Cie. It was also known as the Hotchkiss Mark I and M1909 Benét–Mercié.

It was adopted by the French army as the Hotchkiss M1909 (or Mle 1909) in 1909, firing the 8mm Lebel.

A variant to use the .303 round was produced in Britain as the "Hotchkiss Mark I" and manufactured by Enfield. The British army employed three different types of machine gun: the Vickers medium machine gun, the Hotchkiss (for cavalry and tank use), and the Lewis Gun with the infantry.

It is also known as the Hotchkiss M1909 and M1909 Benét–Mercié, but should not be confused with the heavier Hotchkiss M1914 machine gun.

Users :-

1. Austria-Hungary

2. Australia

3. Belgium

4.Brazil

5.French Third Republic

6. Ireland

7. New Zealand

8. Taiwa

9.  Spain

10.  United Kingdom of Great Britain and Ireland

11.  United States

(Great Britain: Vickers Machine Gun)

The Vickers machine gun or Vickers gun is a name primarily used to refer to the water-cooled .303 British (7.7 mm) machine gun produced by Vickers Limited, originally for the British Army. The machine gun typically required a six- to eight-man team to operate: one fired, one fed the ammunition, the rest helped to carry the weapon, its ammunition, and spare parts.[11] Not to be confused with the Maxim machine gun, it was in service from before the First World War until the 1960s, with air-cooled versions of it on many Allied World War I fighter aircraft.

The weapon had a reputation for great solidity and reliability. Ian V. Hogg, in Weapons & War Machines, describes an action that took place in August 1916, during which the British 100th Company of the Machine Gun Corps fired their ten Vickers guns to deliver sustained fire for twelve hours. Using 100 barrels, they fired a million rounds without breakdowns. "It was this absolute foolproof reliability which endeared the Vickers to every British soldier who ever fired one. It never broke down; it just kept on firing and came back for more.

Did the British invent the Vickers gun?

A mainstay of the British army, the Vickers machine gun is a classic First World War weapon. The design actually built on a previous gun, invented in the late 19th Century by Hiram Stevens Maxim.

Who won World War 1 ?

The Allies

The Allies won World War I after four years of combat and the deaths of some 8.5 million soldiers as a result of battle wounds or disease. Read more about the Treaty of Versailles.

Russian: Maxim M1910 Machine Gun.

"Maxim's machine gun Model 1910")is a medium machine gun that was used by the Imperial Russian Army during World War I and the Red Army during the Russian Civil War and World War II. Later the gun saw service in the Korean War and the Vietnam War"

History :-

It was adopted in August 1910 and was derived from Hiram Maxim's Maxim gun, chambered for the standard Russian 7.62×54mmR rifle cartridge. The M1910 was mounted on a wheeled mount with a gun shield.

In 1918 - 1920, the industry of Soviet Russia produced 21 thousand new Maxim 1910 machine guns for the Red Army.

In 1930, a modernized version 1910/30 was adopted by the Red Army.[4] M1910/30 can be equipped with optical sight.

In 1941, the gun was modernized once again.

In May 1942, an order was given to begin the development of a new machine gun to replace the Maxim 1910/30. On May 15, 1943, the SG-43 Goryunov was adopted and since summer 1943 Maxim guns were replaced in Soviet service by the SG-43, which retained the wheeled and shielded carriage. However, production of the Maxim did not end until 1945.

In addition to the main infantry version, there were aircraft-mounted and naval variants. Some were fitted with a tractor radiator cap fitted on top of the water jacket to allow handfuls of snow to be packed in to melt while firing.

United States: Browning M1917.

M1917 Browning machine gun

The M1919 Browning is a .30 caliber medium machine gun that was widely used during the 20th century, especially during World War II, the Korean War, and the Vietnam War. The M1919 saw service as a light infantry, coaxial, mounted, aircraft, and anti-aircraft machine gun by the U.S. and many other countries.

The M1919 was an air-cooled development of the standard US machine gun of World War I, the John M. Browning-designed water-cooled M1917. The emergence of general-purpose machine guns in the 1950s pushed the M1919 into secondary roles in many cases, especially after the arrival of the M60 in US Army service. The United States Navy also converted many to 7.62 mm NATO, and designated them Mk 21 Mod 0; they were commonly used on riverine craft in the 1960s and 1970s in Vietnam. Many NATO countries also converted their examples to 7.62 mm caliber, and these remained in service well into the 1990s, as well as up to the present day in some countries

It was in 1900 that John Moses Browning launched his study project to develop a water-cooled machine gun. The first prototype is available the following year: this model is much lighter than its foreign contemporaries, including the German MG 08 and the English Vickers.

Before the First World War, the American Army was not particularly interested in this machine gun, but the entry of the United States into the war in 1917 changed the situation. In order to impress the soldiers, Browning organized a shooting session with several of his machine guns: the first shot 40,000 shots in several incidents. The second opens the fire continuously for 48 minutes and 12 seconds without stopping! The US Army immediately adopted it as one of its two main machine guns (the other being the 8 mm Hotchkiss M1914). However, only 1,200 models of the Browning 1917 are actually used on the front because of delivery times. In 1919, Browning produced another air-cooled machine-gun, the 1919.

In 1930, the Browning 1917 machine gun was modified and the new version, called 1917A1, was used during the Second World War. It is equipped with M2 cartridges, ammunition particularly powerful. Due to its weight and its installation time, the use of this machine gun is limited to an essentially static use. The Browning 1917A1 is used in particular during the Battle of Normandy.

Several examples of this machine gun were used during the Korean and Vietnamese wars. Several irregular armies around the world continue to use it today.

Cnc machines for woodworking

The following routers are ideal for small workshop use.

°E3 CNC Router Engraver Kit with DeWalt DW660 Router (450mm x 390mm x 85mm) °The CNC Piranha FX.
°CNC Shop, CNC Router Engraving Machine, 3 Axis 3040T.
°Vevor CNC Router 3020T 3 Axis CNC Router Machine.
°Sanvn CNC 3020t Rouer Engraver Drilling/milling Engraving Machine.

 

° The E3 CNC Router has the following   features.  

(A rigid laser cut frame)

(MDF Spoil-board with 1/4-20 threaded inserts)

(DeWalt DW660 router included in the kit)

Hydraulic machine

 Hydraulic machine

Introduction :-
The subject ' Hydraulic Machines may be defined as that branch of Engineering - science which deals with the machines run by water under some head or raising the water to higher levels.
Impact of water jets  :-
What is the impact of jets of water in hydraulic machines and fluid dynamics? What force does a water jet imposes on different surfaces like plane surface, curved surface and moving curved vanes etc.
Hydraulic Turbines :-

A hydraulic turbine is a machine which converts the hydraulic energy into mechanical energy. The hydraulic turbines are also known as water turbines. Following two types of hydraulic turbines are important.

1.     Impulse turbine

2.     Reaction turbine

In an impulse turbine, the total energy at the inlet of a turbine is only kinetic energy. The pressure of water both at entering and leaving the vanes is atmospheric. It is used for high head of water. A Pelton wheel is a tangential flow impulse turbine.

In a reaction turbine, the total energy at the inlet of a turbine is kinetic energy as well as pressure energy. It is used for low head of water. The Francis and Kaplan turbines are inward flow and axial flow reaction turbines respectively.

1. Impulse Turbines :-

What is an impulse turbine? How do we calculate hydraulic efficiency and mechanical efficiency of an impulse turbine? The following important points may be noted for impulse turbines:

(a) The hydraulic efficiency of an impulse turbine is the ratio of the work done on the wheel to the energy of the jet.

(b) The hydraulic efficiency of an impulse turbine is maximum when the velocity of wheel is one half the velocity of jet of water at inlet.

The mechanical efficiency of an impulse turbine is the ratio of the actual work available at the turbine to the energy imparted to the wheel.

2. Reaction Turbines:-

What is a reaction turbine? How to calculate hydraulic and overall efficiency of reaction turbine? What is difference between a Kaplan turbine and Francis turbine?

The following important points may be noted for reaction turbines :

(a) In a reaction turbine, the water enters the wheel under pressure and flows over the vanes.

(b) The hydraulic efficiency of a reaction turbine is the ratio of the workdone on the wheel to the energy (or head of water) actually supplied to the turbine.

(c) The overall efficiency of a reaction turbine is the ratio of the power produced by the turbine to the energy actually supplied by the turbine.

(d) A Kaplan turbine is an axial flow reaction turbine. The number of blades are generally 4 to 8 in a Kaplan turbine runner.

(e) A Francis turbine is an outward flow reaction turbine. The number of blades are generally 16 to 24 in a Francis turbine runner.

Draft Tube in Turbine :-

The draft tube is a pipe of gradually increasing area used for discharging water from the exit of a reaction turbine. It is an integral part of mixed and axial flow turbines. Because of the draft tube, it is possible to have the pressure at runner outlet much below the atmospheric pressure.

The efficiency of a draft tube is defined as the ratio of net gain in pressure head to the velocity head at entrance of draft tube.

Specific Speed of turbine :-

The specific speed of a turbine is defined as the speed of an imaginary turbine, identical with the given turbine, which develops unit power under unit head. Mathematically, specific Speed. 

The specific speed plays an important role in the selection of a type of turbine. By knowing the specific speed of a turbine, the performance of the turbine can also be predicted.

Unit Speed, Unit Discharge and Unit Power :-

What is Unit Speed, Unit Discharge and Unit Power of a turbine? How do we calculate these using formula?


The unit speed is the speed of the turbine operating under one meter head. Mathematically, unit speed. 

The unit discharge is the discharge through a turbine when the head on the turbine is unity. Mathematically, unit Discharge. 
The unit power is the power developed by a turbine when the head on the turbine is unity. Mathematically, unit power. 

Cavitation :-

What is cavitation and how is it formed and how to prevent/ avoid cavitation in a hydraulic machine? The formation, growth and collapse of vapour filled cavities or bubbles in a flowing liquid due to local fall in fluid pressure is called cavitation. The cavitation in a hydraulic machine affects in the following ways:

(a) It causes noise and vibration of various parts.

(b) It makes surface rough.

(c) It reduces the discharge of a turbine.

(d) It causes sudden drop in power output and efficiency.

"The cavitation in reaction turbines can be avoided to a great extent by using the following methods"

a) By installing the turbine below the tail race level.

(b) By using stainless steel runner of the turbine.

(c) By providing highly polished blades to the runner.

(d) By running the turbine runner to the designed speed.

Centrifugal Pumps :-

What is a centrifugal pump and its manometrichead? How to calculate discharge, efficiency and power required for a centrifugal pump using formula?

A centrifugal pump is a machine which converts the kinetic energy of the water into pressure energy before the water leaves its casing. The flow of water leaving the impeller is free vortex. The impeller of a centrifugal pump may have volute casing, vortex casing and volute casing with guide blades.

blades.

The following important points may be noted for centrifugal pumps:

(a) The manometric head is the actual head of water against which a centrifugal pump has to work.

Manometric head = Workdone per kg of water - Losses within the impeller

 = Energy per kg at outlet of impeller - Energy per kg at inlet of impeller

 = Suction lift + Loss of head in suction pipe due to friction + Delivery lift + Loss of head in delivery pipe due to friction + Velocity head in the delivery pipe.

"The mano metric efficiency of a centrifugal pump is defined as the ratio of the mano metric head to the energy supplied by the impeller"
"The mechanical efficiency of a centrifugal pump is defined as the ratio of energy available at the impeller to the energy supplied to the pump by the prime mover"
"The overall efficiency of a centrifugal pump is defined as the energy supplied to the pump to the energy available at the impeller"
"The efficiency of a centrifugal pump will be maximum when the blades are bent backward"

Multistage Centrifugal Pumps :-

The multistage centrifugal pumps are those which have two or more identical impellers mounted on the same shaft or on different shafts. They are used to produce high heads or to discharge a large quantity of liquid. In order to obtain a high head, a number of impellers are mounted in series or on the same shaft while to discharge a large quantity of liquid, the impellers are connected in parallel.

Reciprocating Pump :-

The reciprocating pump is a positive displacement pump as it discharges a definite quantity of liquid during the displacement of its piston or plunger which executes a reciprocating motion in a closely fitting cylinder. It is best suited for less discharge and higher heads.
The difference between the theoretical discharge and the actual discharge is called the slip of the pump.

Air Vessels:-

What is an air vessel in a reciprocating pump What is purpose of air vessel and why is it used. How it increases saving of work and power (mechanical)?
The air vessel, in a reciprocating pump, is a cast iron closed chamber having an opening at its base. These are fitted to the suction pipe and delivery pipe close to the cylinder of the pump. The vessels are used for the following purposes:

(a) To get continuous supply of liquid at a uniform rate.

(b) To save the power required to drive the pump. This is due to the fact that by using air vessels, the acceleration and friction heads are reduced. Thus the work is also reduced.


It may be noted that by fitting an air vessel to the reciprocating pump, the saving of work and subsequently the power is about 84.8 % in case of a single acting reciprocating pump and 39.2 % in case of double acting reciprocating pump.

Miscellaneous Hydraulic Machines:-

Information about different hydraulic machines like hydraulic press, hydraulic ram, hydraulic accumulator, hydraulic intensifier, hydraulic crane and hydraulic lift. The following are the miscellaneous hydraulic machines:


(a) Hydraulic press. It is a device used to lift larger load by the application of a comparatively much smaller force. It is based on Pascal's law.

(b) Hydraulic ram. It is a device used to lift small quantity of water to a greater height when a large quantity of water is available at a smaller height. It works on the principle of water hammer.

(c) Hydraulic accumulator. It is a device used to store pressure energy which may be supplied to hydraulic machines such as presses, lifts and cranes.

(d) Hydraulic intensifier. It is device used to increase the intensity of pressure of water by means of energy available from a large quantity of water at a low pressure.

(e) Hydraulic crane. It is a device used to lift heavy loads. It is widely used in docks for loading and unloading ships, ware houses, foundry workshops and heavy industries.

(f) Hydraulic lift. It is a device used for carrying persons and loads from one floor to another, in a multistory building.

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