Introduction
Modern manufacturing equipment is often designed against a number of operating targets – such as low energy consumption and high operating speed. Based on these requirements, hd plasma cutters has always been considered as an attractive alternative to other cutting machines owing to its efficiency and excellent operating performance.
Traditionally, conventional Plasma Cutting technologies, such as air plasma cutters and oxygen-based plasma cutters, have been employed in cutting materials with electrically conductive properties such as brass, steel, copper, and aluminium using a highly accelerated jet of hot plasma. Conventional plasma cutters have been well adopted in fabrication shops, restoration and repair industries as well as the scrapping and salvage sectors.
However, as with all things, technology moves on, high definition plasma cutters have been developed to replace conventional plasma cutters and bring with them a number of extra benefits. As such, owing to their high precision, high cutting speed, and low production costs, plasma cutting is increasingly in widespread use in large-scale CNC industrial applications. This article focuses on evaluating the potential benefits of high definition plasma cutters over convectional plasma cutters.
Fundamental operating concepts of plasma cutting
The working mechanism of plasma cutting is the formation of electrical arc between the workpiece and an electrode which is constricted through a fine bore copper nozzle. This constriction leads to an increase in both temperature and the plasma velocity. During cutting, the flow of the plasma gas is increased, causing the plasma jet to cut and penetrate deeper into the workpiece material while the molten material is continually removed as efflux plasma or dross.
Figure 1 The working mechanism of plasma cutting
Evolution of plasma cutters
Air plasma cutting was first developed in the early ‘60s and is believed to have evolved from the low-cost plasma cutting systems that were employed in handheld torches. These early cutters required about 400Amps of power supply and often employed nitrogen as the cutting gas and CO2 as the shield gas. The cutting torch was heavy, large, and often produced a lot of molten metallic spars, thereby producing a poor quality of cut surfaces with low durability. Further developments introduced HD plasma cutters using compressed air instead of hydrogen to allow for lower costs, compactness, and lower power input.
Today’s air plasma cutters employ an inverter-based power supply, produce reasonable cutting speeds and cut quality. However, the precision of cutting is still relatively low and can be inconsistent as it is dependent upon the operator’s skills.
Convectional oxygen-based plasma cutters were developed in the mid-’80s and were mainly employed in cutting stainless steels and aluminium material of up to 15.875mm and 152.4 inches respectively. These plasma cutters employed oxygen as the cutting gas and water injection for constriction. The cutting speeds were better than those of air plasma cutters with clean cuts, lower edge taper, and dross free cuts. The main drawback of these cutters was reduced durability owing to the use of oxygen which had a significant impact on the working environment of the plasma torch.
Today’s oxygen plasma cutters employ improved design which allows up to 50.8mm and 158.75mm cuts for steel and aluminum respectively – and when incorporated with other gases such as argon and hydrogen, the cutting depth tolerance can increase by 0.508mm.
(High definition) HD plasma cutting is the latest thermal cutting technique and was first introduced in the early 1990s after the discovery that increased energy density, through tighter constriction and gas mixing, could improve the cutting process. Higher energy density at the reduced cutting interface allowed for reduced power input (About 70 Amps), precise cut edge, excellent dross-free cuts, high durability, and narrow kerf.
Further refinement of this technology over the years such as advanced liquid cooling and vented nozzle design has allowed cutting of up to 76.2mm for steels and 203.2mm for aluminum – with the excellent cut quality and faster cutting speeds as compared to air and oxygen plasma cutters. Further, HD plasma cutters allow high automation levels with other advanced manufacturing systems, enabling large-scale production with very high accuracies of about 0.254 mm range.
Key benefits of HD plasma cutters over convectional plasma cutters Precision
HD plasma cutters have a great capability to produce clean and very precise cut edges as compared to conventional plasma cutters such as air and oxygen-based cutters. As such, in conventional plasma cutting some degree of dross is present and the edge finish may be unattractive, leading to a need for secondary finishing operations. Figure 2 illustrates a comparison between a conventionally cut material and an HD cut material.
Plasma cutting performed conventionally A View of HD Plasma Cut
Efficiency
High definition plasma cutters can achieve about 3000 starts and above making the cutting process quicker especially when cutting thin metals. This capability is particularly important in CNC plasma cutting. Conventional cutters achieve only around 500 starts, hence cutting operations are relatively slower. Moreover, HD cutters are considered more efficient in producing non-linear cuts as compared to conventional plasma cutters. Table 1 illustrates power requirements and starts of HD plasma cutters and convectional plasma cutters
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Table 1: Power requirements and starts of HD plasma cutters & convectional plasma cutters
Plasma cutting processPower requirementsstartsAir plasma cutter400amps300Oxygen plasma cutter200 amps500High definition plasma cutter70amps3000
Durability
HD plasma cutters are often specifically designed and well refined to increase their durability and life-long consistency in the cutting process. In addition, these plasma cutters can offer a longer consumable life at lower costs compared to conventional plasma cutters. Additionally, HD plasma cutters effectively remove impurities from workpieces thereby reducing the maintenance costs.
Versatility
HD plasma cutters are more versatile in terms of materials they can cut. As such, these plasma cutters can cut non-ferrous materials and steel of varying thickness. Comparatively, HD plasma cutters can achieve a cutting depth of about 203.2mm for alumnium and up to 76.2mm for steel while conventional oxygen plasma cutters can only achieve about 50.8mm for steel and 158.75mm for aluminium. Table 2 illustrates the cutting depths and accuracy of HD plasma cutters and convectional plasma cutters.
Table 2: The cutting depths and accuracy of HD plasma cutters and convectional plasma cutters
Plasma cutting process Depth of cut -Steels
Depth of cut -Alumnnium
AccuracyAir plasma cutter15.875mm152.4mm0.762mmOxygen plasma cutter50.8mm158.75mm0.508mmHigh definition plasma cutter76.2mm203.2mm0.254mmAutomation
HD plasma cutting machines allow automation with CNC machines thereby allowing operators to control cutting operations through computer-based systems. Further, the automation of these metal cutting tools facilitates large-scale production efficiency without having to perform manual cutting or frequent resets of workpieces.
Conclusion
Compared to older designs, HD plasma cutters exhibit high precision in cutting a variety of materials and can also achieve higher depths of cut without secondary operations. The high efficiency and automation of these cutters allows for reliable, accurate and large-scale production of parts.
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