Plasma cutting is a process that cuts electrically conductive materials through accelerated jet heat. Typical materials are cut with a plasma torch including steel, stainless steel, aluminum, brass and copper, although other conductive metals may be cut as well. Plasma cuts are often used in fabrication stores, automotive repair and recovery, industrial construction, and rescue and demolition operations. Due to the high speed and precision cutting combined with the low cost, plasma cutting saw the widespread use of large-scale industrial CNC applications to small hobby shops.
Video Plasma cutting
Process
The basic plasma cutting process involves making electricity from heated gas and electrically ionizing the plasma from the plasma cutter itself, through the workpiece to be cut, thus forming a complete electrical circuit back to the plasma cutter via a grounding clamp. This is done by compressed gases (oxygen, air, inert and others depending on the cut material) which is exhaled through a high-speed focused nozzle toward the workpiece. The electric arc is then formed in the gas, between the near electrode or integrated into the gas nozzle and the workpiece itself. The electric arc ionises a portion of the gas, thus creating an electrically conductive plasma conduit. When the electricity from the cutting torch down this plasma, it provides enough heat to melt through the workpiece. At the same time, many high-speed plasmas and compressed gases blow hot molten metal away, thus separating the cutting of the workpiece.
Plasma cutting is an effective way of cutting thin and thick materials together. Hand torches can usually cut thick steel plates up to 38 mm (1.5 inches), and a stronger computer-controlled torch can cut steel to a thickness of 150 mm (6 inches). Because plasma cutter produces extremely hot and highly localized "cones" to cut, they are very useful for cutting metal sheets in a curved or sloping shape.
Maps Plasma cutting
History
The plasma cutting grew out of plasma welding in the 1960s, and emerged as a very productive way to cut sheet metal and plates in the 1980s. It has the advantage over traditional metal "metal to metal" cuts that do not produce metal chips, provides accurate cuts, and produces a cleaner edge than oxy-fuel cuts. The initial plasma cutter is large, somewhat slow and expensive and, therefore, tends to be dedicated to repeating cutting patterns in "mass production" mode.
Like other machine tools, computer numerical control (CNC) technology was applied to plasma cutting machines in the late 1980s through the 1990s, providing a larger flexibility plasma cutting machine to cut various "on demand" shapes based on a series of programmable instructions. into the numerical control of the machine. This CNC plasma cutting machine, however, is generally confined to the cutting pattern and the inside of a flat steel sheet, using only two motion axes (referred to as X Y cutting).
Security
Appropriate eye protection and facial protection is needed to prevent eye damage called bow eye and damage from debris. It is recommended to use the green color lens # 5. The OSHA recommends 8 shadows for arc currents of less than 300 A, but notes that "These values ​​apply where the actual arc is clearly visible Experience has shown that a light filter can be used when the arc is hidden by Work Unit." Lincoln Electric, a manufacturer of plasma cutting tools, said, "Normally dark colors from # 7 to # 9 are acceptable." Longevity Global, Inc., another manufacturer, offers a more specific table for Eye Protection for Plasma Arc Cutting at lower amperes:
Leather gloves, aprons and jackets are also recommended to prevent burns from splashes and debris.
Start method
The plasma cutter uses a number of methods to start the arc. In some units, the bow is made by placing the torch in contact with the workpiece. Some cutters use high voltage, high frequency circuits to start the arc. This method has a number of disadvantages, including the risk of electric shock, difficulty repairing, maintenance of splashes, and the large amount of radio frequency emissions. Plasma cutters that work near sensitive electronics, such as hardware or CNC computers, start arc pilots in other ways. Nozzles and electrodes touched. Nozzle is cathode, and electrode is anode. When the plasma gas starts to flow, the nozzle is blowing forward. The third less common method is the release of capacitive into the primary circuit through a silicon-controlled rectifier.
Inverter plasma cutter
Analog plasma cutter, usually requires more than 2 kilowatts, use a large electrical frequency transformer. The inverter plasma cutter improves the power supply to DC, which is fed to a high frequency transistor inverter between 10 kHz up to about 200 kHz. The higher switching frequency allows smaller transformers to produce overall size and weight reduction.
The transistor used was initially a MOSFET, but it is now increasingly using IGBT. With parallel MOSFETs, if one of the transistors is activated prematurely it can cause failure to flow from a quarter of the inverter. The next invention, IGBT, is not subject to this failure mode. IGBT can be generally found in high current machines where it is not possible to align enough MOSFET transistors.
The switch mode topology is referred to as a dual transistor off-line forward converter. Although lighter and stronger, some plasma cutter inverters, especially those without power factor correction, can not be run from the generator (which means the inverter unit manufacturers forbid doing it; this applies only to small and lightweight portable generators). However newer models have internal circuits that allow the unit without power factor correction to run on the light power generator.
CNC Cutting Method
Some manufacturers of plasma cutter make CNC cutting tables, and some have cutter built on the table. The CNC table allows the computer to control the head of a torch that produces sharp cuts. Modern CNC plasma equipment is capable of cutting thick multi-axis materials, allowing opportunities for complex weld coatings that may not be otherwise. For thinner materials, plasma cutting is progressively replaced by laser cutting, primarily because of the superior cutting capability of the laser cutter.
The special use of CNC Plasma Cutters has been in the HVAC industry. The software processes information on the work channel and creates a flat pattern to cut on the cutting table with a plasma torch. This technology has greatly increased productivity in the industry since its introduction in the early 1980s.
CNC Plasma Cutters are also used in many workshops to create decorative metal. For example, commercial and residential nameplate, wall art, address sign, and outdoor garden art.
In recent years there have been further developments. Traditionally the cutting table of the machine is horizontal, but now a vertical CNC plasma cutting machine is available, providing a smaller footprint, increased flexibility, optimum security and faster operation.
CNC Plasma Cutting Configuration
There are 3 major CNC Plasma Cutting configurations, and they are largely distinguished by the material forms before being processed, and the flexibility of the cutting head. <2> 2 Dimensional/2-Axis Plasma Cutting It is a form of CNC Plasma Cutting the most common and conventional. Generate flat profile, in which the cut edges are at 90 degrees to the surface of the material. Plasma high-powered plasma cutting configured in this way, were able to cut the profile of the metal plate up to 150mm thick. up to 30mm thickness 3-D/3 Axis Plasma Cutting
Again, the process to produce a flat profile of a sheet or metal plate, but with the introduction of an additional axis rotation, the cutting head of the CNC Plasma Cutting machine can tilt while being carried through a conventional two-dimensional cutting line. The result of this is the edges that are cut at an angle other than 90 degrees to the surface of the material, for example an angle of 30-45 Degrees. This angle is continuous along the thickness of the material. This is usually applied in situations where the cut profile will be used as part of the welded fabrication as the sloping end forms part of the weld preparation. When weld preparation is applied during the cnc plasma cutting process, secondary operations such as grinding or machining can be avoided, reducing costs. 3rd cutting capability The plasma cutting dimensions can also be used to make countersunk holes and profiled holes in the holes.
Tube & amp; Plasma Cutting Section
Used in processing tubes, pipes or any other forms of long parts. The plasma cutting head usually remains stationary while the workpiece is inserted through, and is rotated around the longitudinal axis. There are several configurations in which, like with 3 Plasma Cutting Dimensions, the cutting head can tilt and rotate. This allows slant cutting through tube thickness or parts, usually utilized in the manufacture of process pipes where the cutting pipes can be fitted with welded preparations on straight edge sites.
New technology
In the last decade the plasma torch manufacturers have engineered new models with smaller nozzles and thinner plasma arcs. This allows precision near the laser at the cut edge of the plasma. Some manufacturers incorporate precise CNC controls with these torches to allow assemblers to produce parts that require little or no finishing.
Cost
Plasma torch used to be quite expensive. For this reason they are usually only found in professional welding shops and private garages and very well-stocked shops. However, modern plasma torches are becoming cheaper, and are now in the price range of many fans. The old unit may be very heavy, but still portable, while some newer with inverter technology weighs only slightly, but the same or exceeds the older capacity. etc
See also
- Laser cutting
- Air carbon arc cutting
- Las plasma arc
- Water jet cutter
- Welding
- List of plasma (physics) articles
References
External links
- HowStuffWorks on plasma cutting
- Manufacturing Network & gt; & gt; Knowledge Base - Is CNC Plasma Cutting?
- Statement of the Safe Working Method of Plasma Cutter
- Corrosion Inhibitor for Plasma Table Cutting
Source of the article : Wikipedia
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