In the recent years, plasma cutting has become the cutting process of choice for several industries and fabricators because of its efficiency and cost effectiveness. However, when the plasma cutting technology was first introduced, this technology was not so efficient or popular due to the short life of its consumables. Over the years, technological innovations have enabled plenty of changes in the plasma cutting process itself.
Metal cutting has been in existence from times when the welding process existed. The early method involved using a welding torch with a wire surrounded by shielding gas and this process could cut aluminum and stainless-steel plates. However, plasma cutting came into existence only in 1955 when the process was invented by Dr. R.M Gage at Union Carbide.
The First 15 Years of Plasma Cutting
The plasma cutting process underwent many innovations and improvements in terms of enhancing the arc stability and energy density, improving the cooling of components, using exotic materials, varying the plasma composition, etc.
The plasma cutter contained a tungsten rod which was surrounded by a constricting nozzle and an inert gas shielded the electrode in order to increase its life. Water was injected into the electrode to stabilise and constrict the arc and also cool the plasma torch. Later on, the method of water swirling or the liquid turbine was used to stabilise the arc.
Plasma cutting was an effective method to cut non-ferrous metals and it could not be used to cut metals like stainless steel as the tungsten electrode reacted with oxygen needed for stainless steel cutting. The electrode life was improved by adding an oxidising gas in the nozzle. The arc was further stabilised by swirling the plasma gas. The introduction of the secondary or shield gas around the arc jet improved the cutting process significantly. This helped to reduce the production of dross, helped to drive the arc further into the cut and also doubled the cutting speeds.
Cutting currents were increased to increase the cutting speeds, but this caused the electrode to wear out quickly, thereby affecting the productivity and efficiency of the cutting process.
The invention of the button-type electrode and the replacement of tungsten by zirconium along with air as the plasma gas increased the electrode life and this made air cutting of mild steel popular. Later, zirconium was replaced by hafnium that further improved the electrode life.
The 1970s and 80s
The plasma cutting process underwent several process improvements through the 70s and 80s, but the cutting process really took off when it was automated with the implementation of NC, CNC and DNC and the development of work piece sensing systems and automatic height controllers, which resulted in superior cut quality.
At this time, cost reduction was the key driver and the water injection process was used as it offered high speeds, long consumable life and best quality cuts. The process was used to cut non-ferrous metals and carbon steel with same consumables, varying current and fluids, and the downtime was minimised. The arc chamber was invented and this helped to improve the cut quality and consumable life.
Plasma Cutting Process Reinvented
At the end of the 80s, manual cutting with portable power supply units became popular in the U.S and high-definition plasma cutting was born in Japan. The 90s was the turning point for plasma cutting and the process evolved further. The plasma cutting process started being used for aluminum, as well as for stainless steel and became a cost-effective substitute for the traditional oxyfuel and the emerging laser cutting technologies.
In the last decade, the plasma cutting process has advanced significantly and has taken complete advantage of automation, CNC, table technology, gas controllers, nesting software, etc. Technological advancements and R&D has helped to increase consumable life, enhance cut quality and speed and improve the reliability of the entire cutting process from start to finish.
Today, we have automated systems with microprocessors and state-of-the-art controls for gas delivery, torch motion and current and this has made plasma cutting a cost-effective process. Cut quality has transitioned from being high-quality in the 60s to square cut in the 70s to being high-definition in the 80s and 90s. More than 50 years of continual effort and improvements have made plasma cutting a cost-effective and reliable cutting option for many metal fabricators around the world.