Plasma cutting

Plasma cutting equipment has made the process accessible and commonplace in the industry. The following needs are taken into account in its design:

  • Simplicity and ease of installation.
  • Simplicity, use and maintenance of the equipment.
  • Mobility and versatility of the equipment, for different locations and materials.
  • Easy and fast component replacement without the use of special tools or wrenches.
  • Good cutting quality even in difficult conditions.
  • Low cost of production and equipment repairs.

 

Operation

In the plasma torch the air flows around the cutting electrode, then, a partial ionization takes place as the arc heats the air, which provides a plasma column, which leaves the torch with the arc following the path through the Transferred Arc.

By forcing the plasma gas and the electric arc through a small orifice, the torch undergoes significant heating both in the workpiece itself, which generates the cut, and in the welding torch, so it is necessary to increase the degree of cooling.

When the torch is ignited, an arc is established between the electrode (-) and the nozzle (+), this arc is called “Pilot”, it lasts approximately 2 seconds and its purpose is to start cutting at one end of the piece.

 

Protective gases

Cutting is performed by one of these five gases:

  • Air
  • Mixing Nitrogen with Carbon Dioxide
  • Mixing Nitrogen with Oxygen or Air
  • Mixed ternary
  • Oxygen

NITROGEN:
Non-flammable and inert gas that allows its use as a plasma cutting gas.
Its high purity allows excellent quality cuts.

ARGON:
Gas used as a cutting gas, especially in aluminum.

AIR:
Universally used gas used in plasma cutting, the oxygen in the air provides additional energy for cutting, but oxidizes the cutting zone…

MIXTURES:
Refers to the mixture of nitrogen with hydrogen and argon with hydrogen.
These are shielding gas in plasma cutting.

 

Cutting characteristics

  • Plate thickness up to 40mm.
  • The cut groove is 2 to 4mm wide.
  • It tends to leave oblique edges.
  • The beam is normally approx. 5mm.
  • High cutting speed.
  • This process can cut any electrically conductive metal as long as its thickness and shape allows the plasma jet to pass completely through the metal.

 

Advantages over oxyfuel

  • Less heat input than oxyfuel, meaning less heat-affected zone and less distortion of the part.
  • Less susceptibility to surface conditions of the base material (flaking or painting).
  • Possibility of mechanization and robotization.
  • All metals can be cut by the process.
  • Better cutting quality.
  • Reduction of electricity consumption.
  • Smoke and noise reduction.
  • Higher cutting speed than oxyfuel for medium and thin thicknesses.
  • Because of its speed, it is considered the most productive method of cutting.
  • The ZAT is higher than that of laser cutting and lower than that of oxyfuel.

 

Advantages of Plasma vs Laser

  • Increased flexibility for automated and manual cutting.
  • Significantly lower capital, operating and maintenance costs.

 

MATERIAL THICKNESS PLASMA OXICORTE
STEEL AL
CARBON		 UP TO 2 E I
3 a 15 E E
15 a 50 P E
50 a 90 I E
90 a 300 I E
STEEL
STAINLESS STEEL		 UP TO 5 E I
5 a 10 E I
10 a 50 E I
50 a 90 I I
ALUMINIUM UP TO 8 E I
8 a 50 E I
50 a 90 I I
COPPER UP TO 9 E I
10 a 40 P I
40 a 80 I I

 

E Excellent P Possible I Impossible

 

 

OXICORTE PLASMA
QUALITY
CUTTING		 Good angulation.
A large area is affected by heat.
Slag levels requiring subsequent finishing.
Not effective on stainless steel or aluminum.		 Excellent angulation.
A small area affected by heat.
Virtually no dross.
Good to excellent fine features cut.
PRODUCTION Slow cutting speeds.
The preheating time increases the drilling time.		 Very fast cutting speeds in all thicknesses.
Very fast drilling time.
Quick-connect torches maximize productivity.
COST OF
OPERATION		 The poor productivity and subsequent finishing required pushes the cost per part higher than the cost of plasma. Long consumable life, good productivity and excellent cut quality drive the cost per part lower than other technologies.
MAINTENANCE Simple maintenance requirements can often be done by the facility’s in-house maintenance group. Moderate maintenance requirements:
Many components can be serviced by the facility’s in-house maintenance group.

 

Sectors of application

  • Air conditioning and ventilation industries.
  • On-site maintenance.
  • Installations in general.
  • Metallic carpentry.
  • Construction of apparatus, vessels and tubular conduits.
  • Bodywork.
  • Craft and hardware sectors.
  • Medium and small production workshops.