FOCUS ON PLASMA CUTTING
below the water surface , significantly reducing noise , dust and aerosol pollution in the environment .
■ Plasma gouging . Plasma gouging is the process of removing surface material using a plasma arc . It is used for eliminating defects in welds or surface defects on structural steel and high-alloy steels .
■ Plasma marking . This process is used for marking cut components .
Plasma cutting benefits with intelligent strategies to pierce and lead in and lead out of the profile . Failure to do so will impact consumable life and cut quality . Some types of CAD / CAM nesting software for plasma cutting can control and automatically set up virtually every aspect of the plasma cutting operation .
“ While the plasma unit is central to the cutting process , it is the sum of the complementary parts that control , hold and move the plasma cutting torch that will ultimately define cut quality . When investing in this type of CNC technology , you are doing so to decrease your costs and increase your profits . A high-performance plasma cutting machine can reward you with returns of over one hundred pounds per hour if you can produce high-quality parts . As the saying goes ‘ a chain is only as strong as its weakest link ’ and that is very much the case with a plasmacutting machine installation ,” continued Kerf Developments .
There are three major components inside the torch body itself ; electrode , gas baffle ( swirl baffle ) and nozzle . These items are called consumables . They are consumed over time during the plasma process and must be replaced . The electrode is connected to the negative side of a DC plasma power supply . The nozzle is connected to the positive side but is electrically isolated using a normally open relay .
Plasma cutting with FineCut ® consumables ( image : Hypertherm ).
variation of the dual-gas process where water is substituted for the shield gas .
■ Water injection plasma cutting . This process uses a single gas for plasma and utilises water either radially or swirlinjected directly into the arc to greatly improve arc constriction so that arc density and temperatures increase .
■ Precision plasma cutting . This process produces superior cut quality on thinner materials at slower speeds . This improved quality is the result of using the latest technology to super-constrict the arc , dramatically increasing energy density .
■ High-tolerance plasma arc cutting ( HTPAC ). The process gives better precision on material of under 12mm thick and can be a low-cost alternative to laser cutting .
■ Underwater plasma cutting . This variation significantly increases operating safety . Cutting is done about 60-100mm
“ Plasma cutting is unrivalled when it comes to cutting medium to thick sheets of high-alloy steel and aluminium . It is also used for cutting normal structural steel up to about 40mm in thickness and results in very little distortion , particularly on thin workpieces . Owing to its low heat input , it is also especially suitable for cutting high-strength , fine-grained structural steels . The high cutting speeds are especially important in the preliminary fabricating process : in comparison to oxyfuel , cutting speeds of five to six times higher can be achieved ,” commented BOC .
“ The cutting process can be easily automated . By using different plasma cutter guidance systems , both flat and threedimensional components with different contours can be produced . There are also various modern peripheral devices and accessories available for manual cutting , which allow for easier handling of parts during processing and simplify assembly and repair work . Modern plasma cutting technology is becoming increasingly important . Especially when it comes to cutting thin , high-alloy steels , plasma cutting allows vertical cuts to be produced on multiple sheets simultaneously in laser-quality without the need for further machining ,” it concluded . n
Process variations
There are many variations of the plasma cutting process ; some of these are listed below .
■ Conventional plasma cutting ( using a single gas ).
■ Dual-gas plasma cutting .
■ Water shield plasma cutting . This is a
34 | ismr . net | ISMR December 2023 / January 2024