When a company has to select the type of technology to use for sheet metal machining, the question arises as to what cutting machine is the most effective from among the different types available.
Today, the cutting of sheet metal, can be carried out by relying on a variety of solutions. Increasingly, companies in the metal, shipbuilding, automotive, and construction industries are putting laser cutting up against plasma cutting.
These sheet metal cutting technologies, predominantly used in metalworking, have similar manufacturing goals but can be quite distinct in their specific uses.
It is difficult to determine a priori which one to choose between plasma cutting or laser cutting. Selecting one of these options for the sheet metal working industry certainly involves an initial assessment of the applications and requirements for which one or the other cutting system is the more preferable.
Here we explain what the main differences are between laser cutting and plasma cutting of sheet metal.
The main features of laser cutting and plasma cutting
Laser cutting machines
Laser cutting machines (an acronym for Light Amplification by Stimulated Emission of Radiation) used for sheet metal working are based on the emission of a particularly collimated, monochromatic beam of light.
Laser cutting technology is ideally suited for processing thin, delicate sheet metal, i.e. 5 to 12 mm, as well as medium-thickness sheet metal, i.e. 20 mm.
This is for three basic reasons:
- laser light beam concentrates a vast amount of power on small areas;
- low thermal impact on the plate;
- extreme accuracy in cutting, no further machining is required.
Until recently, a technological limitation was 20 mm thickness, beyond which plasma cutting was the preferred option. Laser machines rarely exceeded the physical limit of cutting beyond 20-25 mm in thickness, and machining speeds were still rather poor.
Today high-power fiber sources (8, 10, 12, 15 and 20 kW) are available, and the substrate thickness limit to be cut has been raised to 35 to 50 mm.
Taking advantage of the high power of the new fiber laser sources, iron, stainless steel and aluminium can be cut with thicknesses reaching well over 20 mm at competitive speeds and with the guarantee of excellent surface finishes coupled with high degrees of accuracy.
Laser cutting systems are particularly advantageous because –
- They allow for clean, accurate, burr-free cuts on surfaces
- They do not require any further processing
- Low energy consumption compared with plasma cutting
- Very low use of consumables compared with plasma cutting
- Able to perform perfect under-thickness drilling (from 5mm to 20mm thickness)
- They can even be used for cutting stamped and deep-drawn surfaces.
- They can also be used for processing semi-finished and pre-coated items
Plasma cutting for sheet metal processing
Plasma cutting technology, discovered over fifty years ago, is used for processing various types of thicker conductive metal materials (stainless steel, aluminium, copper, and brass).
Plasma lasers use energy and heat to cut into materials. In particular, a gas jet is used that is sent to a torch and ionised at high temperature either by an electric arc or a high-frequency inductor.
Hydrogen and nitrogen are the gas mixtures used. A high-pressure gas is blown through a nozzle, which becomes plasma via an electrical interaction with an electrode and transfers heat to the metal, bringing it to melting temperature and thus cutting into it.
With a plasma cutting machine, a rather accurate but not outstanding job is achieved. As a result, removal of metal residue following the cut is required at a later stage by hand.
Plasma machines can also be used to cut other types of metals, including non-ferrous ones. However, for sheets of more ‘delicate’ alloys such as carbon steel, plasma cutting is preferable for smaller thicknesses and is carried out manually since there would less accuracy would be achieved with automatic cutting.
|Laser Cutting||Plasma Cutting|
|Ideal for thicknesses up to 40 mm||Suitable for considerable thicknesses|
|High accuracy and finish||Presence of micro-imperfections|
|Excellent value for money|
|Low operating costs|
|Optimisation of nesting and drastic reduction of sheet metal offcuts|
What are the advantages of plasma cutting?
Today, plasma cutting technology is ideal for processing sheet metal with thicknesses of over 35 to 40 mm. For example, in structural metalwork or where no particular cosmetic accuracy is required.
Unlike laser cutting, plasma cutting can more easily present micro-imperfections on surfaces of materials. The cutting surface is not perpendicular and has a poor surface finish. Holes are of poor quality and often have to be drilled by hand using other workshop machinery. Laser cutting makes it possible to reduce sheet offcuts and thus optimise the machinable surface.
Tolerances achievable with plasma cutting are two orders of magnitude higher than with laser cutting – of the order of millimetres with plasma versus a few hundredths of a millimetre with laser.
What to choose – laser or plasma cutting?
With the advent of high-power fiber laser sources, many processes that were previously performed on plasmas can now be transferred to laser machines. The advantages are manifold and we have described them in the article ‘What is a fiber laser? – All you need to know’.
The main advantages are quality of the cut pieces and productivity for low/medium thickness sheets. In addition to this, we can safely say that fiber lasers have much lower standing costs in terms of consumables (nozzles, ceramics and protective glass) than plasma lasers (torches, electrodes). Furthermore, with a laser there is a large saving to be made on material due to the optimisation of nesting and a considerable saving in electrical energy.
For plasma cutting machines, changeover times range from a few seconds (with straightforward procedures) to several minutes or hours (with complex procedures that then require fine-tuning and cutting tests).
This severely affects the availability of the machine for production purposes. Unlike a laser, a plasma cutting machine will be down for several hours each month for routine maintenance and set-up.
In light of these significant differences – which have a considerable impact on the final output – one can say that because of the latest technological developments, the fiber laser is becoming increasingly popular on the market. Indeed, it is widely accepted in the field of machining processes that were traditionally carried out with plasma cutting, but which today only make sense for thicker gauges.
Cutlite Penta provides your company with high-performance, low-cost fiber laser machines and special, large systems capable of interpolating machining in 3D and space. See our technological solution!