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Plasma Cutting Systems and Consumables

A plasma cutter uses an electric arc and compressed gas to cut conductive metal. The torch consumables (electrode, swirl ring, nozzle, retaining cap and shield) wear together, must match the amperage, and last longer with clean, dry air.

Ref WG-0121IEC 60974-1

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

A plasma system has a power source, a torch and a gas supply, usually shop compressed air. The arc heats the gas into plasma that melts the metal, and the gas flow blows the melt out of the cut. Power sources are covered by IEC 60974-1. The torch front end, from inside to outside, is:

Electrode: copper body with a hafnium insert where the arc starts.
Swirl ring: spins the gas to center and constrict the arc.
Nozzle (tip): has a small orifice that focuses the arc. Sized by amperage.
Retaining cap: holds the stack together.
Shield or deflector: protects the nozzle from spatter and lets drag cutting where the system allows.

How to identify

Consumables are system-specific and marked with a part number. Nozzles and shields are usually stamped with the amperage, such as 45 A or 65 A. Mixing amperage parts gives poor cuts and short life. See the identifying plasma consumables by amperage sheet.

Consumable wear signs

Part	Normal wear sign	Replace when
Electrode	Pit in the hafnium insert	Pit depth reaches the maker's limit
Nozzle	Orifice becomes oval or rough	Orifice is out of round or gouged
Shield	Spatter, nicks	Holes blocked or damaged
Swirl ring	Usually long-lived	Cracked, burned or holes blocked
Retaining cap	Long-lived	Cracked or damaged insulator

Replace the electrode and nozzle together on most systems, since a worn one wears the other faster.

Air quality

Plasma air must be clean, dry and oil-free. Water and oil in the air shorten consumable life sharply and cause sputtering and poor cuts. Use the filter and dryer the maker calls for, drain the compressor tank, and set the pressure and flow the maker gives for the torch length.

Key points

Match nozzle and shield amperage to the cutting current.
Cut quality depends on travel speed, standoff and amperage. Follow the maker's cut charts.
Avoid starting the arc in the air without need. Pilot arc time wears consumables.
Plasma cutting makes intense light, noise and fumes. Use proper eye protection and fume control. See the welding filter shade chart.
Pierce from a standoff and move to cutting height to protect the nozzle.

Common mistakes

Running with wet or oily air.
Mixing parts of different amperage or from different systems.
Replacing only the nozzle and leaving a worn electrode.
Dragging a torch that is not set up for drag cutting.

Governing standards: IEC 60974-1 (welding power sources); IEC 60974-7 (torches); ANSI Z49.1 (safety in welding and cutting); maker's cut charts and consumable data.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

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