Plasma cutting is a process that cuts through electrically conductive materials by means of an accelerated jet of hot plasma . Typical materials cut with a plasma torch include steel , stainless steel , aluminum , brass and copper , although other conductive metals may be cut as well. Plasma cutting is often used in fabrication shops, automotive repair and restoration , industrial construction , and salvage and scrapping operations. Due to the high speed and precision cuts combined with low cost, plasma cutting sees widespread use from large-scale industrial computer numerical control (CNC) applications down to small hobbyist shops.
43-401: The basic plasma cutting process involves creating an electrical channel of superheated, electrically ionized gas i.e. plasma from the plasma cutter itself, through the workpiece to be cut, thus forming a completed electric circuit back to the plasma cutter through a grounding clamp . This is accomplished by a compressed gas (oxygen, air, inert and others depending on material being cut) which
86-557: A battery or a generator . Active elements can inject power to the circuit, provide power gain, and control the current flow within the circuit. Passive networks do not contain any sources of electromotive force. They consist of passive elements like resistors and capacitors. A network is linear if its signals obey the principle of superposition ; otherwise it is non-linear. Passive networks are generally taken to be linear, but there are exceptions. For instance, an inductor with an iron core can be driven into saturation if driven with
129-468: A cascading failure of one quarter of the inverter. A later invention, IGBTs, are not as subject to this failure mode. IGBTs can be generally found in high-current machines where it is not possible to parallel enough MOSFET transistors. The switch mode topology is referred to as a dual transistor off-line forward converter. Although lighter and more powerful, some inverter plasma cutters, especially those without power factor correction , cannot be run from
172-440: A cleaner edge than oxy-fuel cutting . Early plasma cutters were large, somewhat slow and expensive and, therefore, tended to be dedicated to repeating cutting patterns in a "mass production" mode. As with other machine tools, CNC (computer numerical control) technology was applied to plasma cutting machines in the late 1980s into the 1990s, giving plasma cutting machines greater flexibility to cut diverse shapes "on demand" based on
215-407: A conventional 2-dimensional cutting path. The result of this is cut edges at an angle other than 90 degrees to the material surface, for example 30-45 degree angles. This angle is continuous throughout the thickness of the material. This is typically applied in situations where the profile being cut is to be used as part of a welded fabrication as the angled edge forms part of the weld preparation. When
258-409: A generator (that means manufacturer of the inverter unit forbids doing so; it is only valid for small, light portable generators). However newer models have internal circuitry that allows units without power factor correction to run on light power generators. Some plasma cutter manufacturers build CNC cutting tables, and some have the cutter built into the table. CNC tables allow a computer to control
301-509: A jacket are also recommended to prevent burns from sparks and hot metal. Working in a clean area free of flammable liquids, materials and gases is very important. Sparks and hot metal from a plasma cutter can quickly cause fires if they are not isolated from flammable objects. Plasma cutters can send hot sparks flying up to 1.5 meters (5 feet) away in certain situations. Machine operators are typically blind to any fire that has started because they are behind their face shields. Plasma cutters use
344-442: A large enough current. In this region, the behaviour of the inductor is very non-linear. Discrete passive components (resistors, capacitors and inductors) are called lumped elements because all of their, respectively, resistance, capacitance and inductance is assumed to be located ("lumped") at one place. This design philosophy is called the lumped-element model and networks so designed are called lumped-element circuits . This
387-454: A model of such an interconnection, consisting of electrical elements (e.g., voltage sources , current sources , resistances , inductances , capacitances ). An electrical circuit is a network consisting of a closed loop, giving a return path for the current. Thus all circuits are networks, but not all networks are circuits (although networks without a closed loop are often imprecisely referred to as "circuits"). Linear electrical networks,
430-464: A number of methods to start the arc. In some units, the arc is created by putting the torch in contact with the work piece. Some cutters use a high voltage, high frequency circuit to start the arc. This method has a number of disadvantages, including risk of electrocution, difficulty of repair, spark gap maintenance, and the large amount of radio frequency emissions. Plasma cutters working near sensitive electronics, such as CNC hardware or computers, start
473-448: A set of instructions that were programmed into the machine's numerical control. These CNC plasma cutting machines were, however, generally limited to cutting patterns and parts in flat sheets of steel, using only two axes of motion (referred to as X Y cutting). Proper eye protection and face shields are needed to prevent eye damage called arc eye as well as damage from debris. It is recommended to use green lens shade #5. OSHA recommends
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#1732869999209516-522: A shade 8 for arc current less than 300 A, but notes that "These values apply where the actual arc is clearly seen. Experience has shown that lighter filters may be used when the arc is hidden by the workpiece." Lincoln Electric, a manufacturer of plasma cutting equipment, says, "Typically a darkness shade of #7 to #9 is acceptable." Longevity Global, Inc., another manufacturer, offers this more specific table for eye protection for plasma arc cutting at lower amperages: (ANSI Z87.1+) Leather gloves, an apron and
559-439: A special type consisting only of sources (voltage or current), linear lumped elements (resistors, capacitors, inductors), and linear distributed elements (transmission lines), have the property that signals are linearly superimposable . They are thus more easily analyzed, using powerful frequency domain methods such as Laplace transforms , to determine DC response , AC response , and transient response . A resistive network
602-585: A straight edge. In the past decade plasma torch manufacturers have engineered new models with a smaller nozzle and a thinner plasma arc. This allows near-laser precision on plasma cut edges. Several manufacturers have combined precision CNC control with these torches to allow fabricators to produce parts that require little or no finishing. Plasma torches were once quite expensive. For this reason they were usually only found in professional welding shops and very well-stocked private garages and shops. However, modern plasma torches are becoming cheaper, and now are within
645-399: A very hot and very localized "cone" to cut with, they are extremely useful for cutting sheet metal in curved or angled shapes. The arcs are generated in a three step process. A high voltage spark briefly ionizes the air within the torch head. This makes the air conductive and allows the "pilot arc" to form. The pilot arc forms within the torch head, with current flowing from the electrode to
688-493: Is a network containing only resistors and ideal current and voltage sources. Analysis of resistive networks is less complicated than analysis of networks containing capacitors and inductors. If the sources are constant ( DC ) sources, the result is a DC network. The effective resistance and current distribution properties of arbitrary resistor networks can be modeled in terms of their graph measures and geometrical properties. A network that contains active electronic components
731-419: Is blown through a focused nozzle at high speed toward the workpiece. An electrical arc is then formed within the gas, between an electrode near or integrated into the gas nozzle and the workpiece itself. The electrical arc ionizes some of the gas, thereby creating an electrically conductive channel of plasma. As electricity from the cutter torch travels down this plasma it delivers sufficient heat to melt through
774-419: Is called a semi-lumped design. An example of a semi-lumped circuit is the combline filter . Sources can be classified as independent sources and dependent sources. An ideal independent source maintains the same voltage or current regardless of the other elements present in the circuit. Its value is either constant (DC) or sinusoidal (AC). The strength of voltage or current is not changed by any variation in
817-433: Is known as an electronic circuit . Such networks are generally nonlinear and require more complex design and analysis tools. An active network contains at least one voltage source or current source that can supply energy to the network indefinitely. A passive network does not contain an active source. An active network contains one or more sources of electromotive force . Practical examples of such sources include
860-399: Is the oscillation rate of an alternating electric current or voltage or of a magnetic , electric or electromagnetic field or mechanical system in the frequency range from around 20 kHz to around 300 GHz . This is roughly between the upper limit of audio frequencies and the lower limit of infrared frequencies, and also encompasses the microwave range. These are
903-503: Is the conventional approach to circuit design. At high enough frequencies, or for long enough circuits (such as power transmission lines ), the lumped assumption no longer holds because there is a significant fraction of a wavelength across the component dimensions. A new design model is needed for such cases called the distributed-element model . Networks designed to this model are called distributed-element circuits . A distributed-element circuit that includes some lumped components
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#1732869999209946-541: The PLECS interface to Simulink uses piecewise-linear approximation of the equations governing the elements of a circuit. The circuit is treated as a completely linear network of ideal diodes . Every time a diode switches from on to off or vice versa, the configuration of the linear network changes. Adding more detail to the approximation of equations increases the accuracy of the simulation, but also increases its running time. Radio frequency Radio frequency ( RF )
989-558: The heating, ventilating and air conditioning (HVAC) industry. Software processes information on ductwork and creates flat patterns to be cut on the cutting table by the plasma torch. This technology has enormously increased productivity within the industry since its introduction in the early 1980s. CNC plasma cutters are also used in many workshops to create decorative metalwork. For instance, commercial and residential signage, wall art, address signs, and outdoor garden art. In recent years there has been even more development. Traditionally
1032-499: The 50 or 60 Hz current used in electrical power distribution . The radio spectrum of frequencies is divided into bands with conventional names designated by the International Telecommunication Union (ITU): Frequencies of 1 GHz and above are conventionally called microwave , while frequencies of 30 GHz and above are designated millimeter wave . More detailed band designations are given by
1075-489: The circuit conform to the voltage/current equations governing that element. Once the steady state solution is found, the operating points of each element in the circuit are known. For a small signal analysis, every non-linear element can be linearized around its operation point to obtain the small-signal estimate of the voltages and currents. This is an application of Ohm's Law. The resulting linear circuit matrix can be solved with Gaussian elimination . Software such as
1118-1341: The connected network. Dependent sources depend upon a particular element of the circuit for delivering the power or voltage or current depending upon the type of source it is. A number of electrical laws apply to all linear resistive networks. These include: Applying these laws results in a set of simultaneous equations that can be solved either algebraically or numerically. The laws can generally be extended to networks containing reactances . They cannot be used in networks that contain nonlinear or time-varying components. [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] To design any electrical circuit, either analog or digital , electrical engineers need to be able to predict
1161-522: The current proliferation of radio frequency wireless telecommunications devices such as cellphones . Medical applications of radio frequency (RF) energy, in the form of electromagnetic waves ( radio waves ) or electrical currents, have existed for over 125 years, and now include diathermy , hyperthermy treatment of cancer, electrosurgery scalpels used to cut and cauterize in operations, and radiofrequency ablation . Magnetic resonance imaging (MRI) uses radio frequency fields to generate images of
1204-413: The cut edges are at 90 degrees to the material surface. High powered CNC plasma cutting beds are configured in this way, able to cut profiles from metal plate up to 150 mm thick. Once again, a process for producing flat profiles from sheet or plate metal, however with the introduction of an additional axis of rotation, the cutting head of a CNC plasma cutting machine can tilt whilst being taken through
1247-446: The frequencies at which energy from an oscillating current can radiate off a conductor into space as radio waves , so they are used in radio technology, among other uses. Different sources specify different upper and lower bounds for the frequency range. Electric currents that oscillate at radio frequencies ( RF currents ) have special properties not shared by direct current or lower audio frequency alternating current , such as
1290-413: The human body. Radio Frequency or RF energy is also being used in devices that are being advertised for weight loss and fat removal. The possible effects RF might have on the body and whether RF can lead to fat reduction needs further study. Currently, there are devices such as trusculpt ID , Venus Bliss and many others utilizing this type of energy alongside heat to target fat pockets in certain areas of
1333-485: The machines' cutting tables were horizontal, but now vertical CNC plasma cutting machines are available, providing for a smaller footprint, increased flexibility, optimum safety and faster operation. There are three main configurations of CNC plasma cutting, and they are largely differentiated by the forms of materials before processing, and the flexibility of the cutting head. This is the most common and conventional form of CNC plasma cutting. Producing flat profiles, where
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1376-402: The mains supply to DC, which is fed into a high-frequency transistor inverter between 10 kHz to about 200 kHz. Higher switching frequencies allow smaller transformers resulting in overall size and weight reduction. The transistors used were initially MOSFETs , but are now increasingly using IGBTs . With paralleled MOSFETs, if one of the transistors activates prematurely it can lead to
1419-406: The nozzle inside the torch head. The pilot arc begins to burn up the nozzle, a consumable part, while in this phase. The air then blows the plasma out the nozzle towards the work, providing a current path from the electrode to the work. When the control system senses current flowing from the electrode to the work, it cuts the electrical connection to the nozzle. Current then flows from the electrode to
1462-454: The pilot arc by other means. The nozzle and electrode are in contact. The nozzle is the cathode , and the electrode is the anode . When the plasma gas begins to flow, the nozzle is blown forward. A third, less common method is capacitive discharge into the primary circuit via a silicon controlled rectifier . Analog plasma cutters, typically requiring more than 2 kilowatts, use a heavy mains-frequency transformer. Inverter plasma cutters rectify
1505-413: The price range of many hobbyists, less than $ 300. Older units may be very heavy, but still portable, while some newer ones with inverter technology weigh only a little, yet equal or exceed the capacities of older ones. Electric circuit An electrical network is an interconnection of electrical components (e.g., batteries , resistors , inductors , capacitors , switches , transistors ) or
1548-465: The standard IEEE letter- band frequency designations and the EU/NATO frequency designations. Radio frequencies are used in communication devices such as transmitters , receivers , computers , televisions , and mobile phones , to name a few. Radio frequencies are also applied in carrier current systems including telephony and control circuits. The MOS integrated circuit is the technology behind
1591-428: The time, cost and risk of error involved in building circuit prototypes. More complex circuits can be analyzed numerically with software such as SPICE or GNUCAP , or symbolically using software such as SapWin . When faced with a new circuit, the software first tries to find a steady state solution , that is, one where all nodes conform to Kirchhoff's current law and the voltages across and through each element of
1634-413: The torch head producing clean sharp cuts. Modern CNC plasma equipment is capable of multi-axis cutting of thick material, allowing opportunities for complex welding seams that are not possible otherwise. For thinner material, plasma cutting is being progressively replaced by laser cutting , due mainly to the laser cutter's superior hole-cutting abilities. A specialized use of CNC plasma cutters has been in
1677-462: The voltages and currents at all places within the circuit. Simple linear circuits can be analyzed by hand using complex number theory . In more complex cases the circuit may be analyzed with specialized computer programs or estimation techniques such as the piecewise-linear model. Circuit simulation software, such as HSPICE (an analog circuit simulator), and languages such as VHDL-AMS and verilog-AMS allow engineers to design circuits without
1720-469: The weld preparation is applied during the CNC plasma cutting process, secondary operations such as grinding or machining can be avoided, reducing cost. The angular cutting capability of 3-dimensional plasma cutting can also be used to create countersunk holes and chamfer edges of profiled holes. Used in the processing of tube, pipe or any form of long section. The plasma cutting head usually remains stationary whilst
1763-448: The work, and the arc forms outside the nozzle. Cutting can then proceed, without burning up the nozzle. Nozzle life is limited by the number of arc starts, not cutting time. Plasma cutting grew out of plasma welding in the 1960s, and emerged as a very productive way to cut sheet metal and plate in the 1980s. It had the advantages over traditional "metal against metal" cutting of producing no metal chips, giving accurate cuts, and producing
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1806-399: The workpiece is fed through, and rotated around its longitudinal axis. There are some configurations where, as with 3-dimensional plasma cutting, the cutting head can tilt and rotate. This allows angled cuts to be made through the thickness of the tube or section, commonly taken advantage of in the fabrication of process pipework where cut pipe can be provided with a weld preparation in place of
1849-458: The workpiece. At the same time, much of the high-velocity plasma and compressed gas blow the hot molten metal away, thereby separating, i.e. cutting through, the workpiece. Plasma cutting is an effective way of cutting thin and thick materials alike. Hand-held torches can usually cut up to 38 mm (1.5 in) thick steel plate, and stronger computer-controlled torches can cut steel up to 150 mm (6 in) thick. Since plasma cutters produce
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