Technical reference

Laser Cutting Glossary: Terms Engineers Actually Use

Updated 2026-10-13 · 8 min read

Laser cutting has its own vocabulary, and it is not always used consistently. Suppliers describe the same specification with different words, and buyers end up comparing numbers that are not comparable. This glossary defines the terms as we use them on the shop floor.

Laser sources and types

Fiber laser

A laser where the active medium is an optical fiber doped with rare-earth elements, generating light at roughly 1.07 µm. Metals absorb this wavelength well, so fiber lasers cut steel, stainless, aluminium, brass and copper efficiently. This is the dominant technology for metal cutting.

CO2 laser

A laser using a gas mixture (CO₂, nitrogen, helium) that emits at 10.6 µm. Non-metals such as acrylic, wood, leather and glass absorb this wavelength strongly; metals reflect it. The standard choice for non-metal cutting and mixed-material work.

Diode laser

A semiconductor laser, usually at 445 nm or around 1 µm. Compact and inexpensive, common in entry-level engraving machines. Limited power compared with fiber or CO2, and not a production cutting tool for thick metal.

MOPA

A fiber laser architecture (Master Oscillator Power Amplifier) that allows independent control of pulse width and frequency. Used mainly in marking for colour marking on stainless steel and fine control on heat-sensitive parts.

Wavelength

The colour of the laser light, measured in micrometres. It determines which materials absorb the beam and therefore which materials the machine can cut. The single most important specification for material compatibility.

Beam quality (M²)

How close the beam is to a perfect Gaussian profile. M² = 1 is ideal. Better beam quality means a smaller focus spot and higher power density, which matters for cutting thin material fast and thick material cleanly.

Single-mode and multimode

Single-mode fiber lasers deliver a near-perfect beam for thin sheet and fine features. Multimode sources have a larger core, deliver more total power and are used for thick plate where raw power matters more than spot size.

Machine components

Cutting head

The assembly that holds the focus lens, protective window and nozzle, and controls focus position and height. A branded auto-focus head costs several times a generic one and is where cheap machines usually save money.

Focus lens

The optic that concentrates the beam. Its focal length sets the depth of focus: shorter for thin material and fine features, longer for thick plate.

Collimating lens

The optic that takes the diverging light from the delivery fiber and makes it parallel before the focus lens. A contaminated collimating lens degrades the beam without an obvious symptom.

Protective window

A sacrificial optic between the nozzle and the focus lens. It takes the spatter so the expensive lens does not. Replaced on a schedule or when pitted — never reused once the coating is breached.

Nozzle

The copper tip that shapes and directs the assist gas into the kerf. Nozzle diameter and condition directly affect cut quality. A spattered or deformed nozzle ruins every parameter you set.

Ceramic ring

An insulating ring in the nozzle holder that supports capacitive height sensing. A cracked ring causes height-sensing faults and is a common cause of sudden cutting failures.

Capacitive height sensing

A system that measures the distance between the nozzle and the workpiece electrically, keeping the cutting height constant even if the sheet is not perfectly flat.

Auto-focus

A cutting head that adjusts focus position under program control, so different materials and thicknesses can be cut in one job without manual adjustment.

Galvanometer

A mirror assembly that steers the beam at high speed. Used in laser marking machines and some fine-cutting systems rather than in gantry-style cutters.

Chiller

The cooling unit that keeps the laser source and optics within their temperature range. Must be matched to the source's heat load; an undersized chiller causes derating and shutdowns in warm weather.

Gantry

The moving bridge that carries the cutting head across the bed. Its rigidity and mass determine how fast the machine can accelerate without losing accuracy.

Linear guide rail

The precision track the gantry and carriage run on. Brand and condition matter: worn rails show up as lost accuracy on long cuts and circles that are not round.

Ballscrew

A recirculating-ball screw that converts rotary motion into linear motion with minimal backlash. More accurate than rack and pinion, and normally used on the Z axis and on smaller beds.

Rack and pinion

A gear rack drive used on large beds where speed and travel length matter more than ultimate precision.

Servo motor

A closed-loop motor with position feedback. Provides the acceleration and accuracy needed for complex contours at speed.

Stepper motor

An open-loop motor that moves in discrete steps. Cheaper, adequate for light engraving, but prone to losing position under load — which is why production machines use servos.

Rotary attachment

A chuck or roller accessory that rotates a tube or cylinder under the cutting head, letting a flat-bed machine process tubes and round parts.

Cutting parameters and process

Kerf

The width of material the beam removes. Typically 0.1–0.2 mm on thin sheet, 0.4–0.7 mm on thick plate. The tool path must be offset by half the kerf on each side to hit a nominal dimension.

Focus position

Where the beam waist sits relative to the material surface. Expressed as a negative number when focused below the surface. Set too high, the kerf widens; too low, the cut becomes narrow and drossy on thick material.

Assist gas

The gas blown through the nozzle into the kerf to expel molten material and, in some cases, participate in the cut chemically.

Oxygen cutting

Using oxygen as the assist gas. The oxidation of iron releases heat that helps cut carbon steel fast, at the cost of an oxidised edge that must be cleaned before welding or painting.

Nitrogen cutting

Using nitrogen as the assist gas. Inert, so it prevents oxidation and produces a clean, weldable edge. The standard for stainless steel and aluminium, at pressures of 10–20 bar.

Piercing

Making the initial hole before the cut profile begins. Piercing thick material at full power spatters badly, so a two-stage pierce (low power, then full) is used above roughly 4 mm.

Dross

Molten material not expelled from the kerf, re-solidified — usually on the bottom edge. Caused by too much heat for the speed, focus set too low, or insufficient gas pressure.

Heat affected zone (HAZ)

The band of material beside the cut whose microstructure has been altered by heat. Narrow on fiber laser cuts, wider on CO2 and plasma, and relevant where fatigue or corrosion performance matters.

Cutting speed

How fast the head travels along the profile, in metres per minute. Falls sharply with thickness, and differs by material: stainless cuts at roughly half the carbon steel speed at the same thickness.

Power density

Power delivered per unit area at the focus spot. The real determinant of cutting capability — which is why beam quality matters as much as wattage.

Nesting

Arranging parts on a sheet to minimise waste. Nesting software can also apply common-line cutting and chain cutting to reduce total travel and pierce count.

Common-line cutting

Sharing a single cut path between two adjacent parts, halving the cut length and the number of pierces.

Micro-joint (tab)

A small uncut bridge that holds a part in the sheet so it does not tip or shift before the job finishes. Broken by hand or with a tool after removal.

Quality and measurement

Tolerance

The permissible variation in a finished dimension. For laser cutting, typically ±0.05 to ±0.10 mm on thin sheet and ±0.10 to ±0.25 mm on thicker material — including thermal distortion, not just machine accuracy.

Positioning accuracy

How close the machine brings the head to a commanded coordinate. A property of the machine, typically ±0.01 to ±0.05 mm, and not the same thing as the tolerance of the finished part.

Repeatability

How consistently the machine returns to the same position. Usually similar to or better than positioning accuracy.

Perpendicularity

How square the cut face is through the thickness. Degrades with thickness because the kerf tapers. Part of what ISO 9013 classifies.

Surface roughness (Rz)

A measure of the cut face texture, expressed as a mean peak-to-valley height. Finer classes of cut require slower speeds.

ISO 9013

The standard classifying thermal cuts by quality — mainly perpendicularity and roughness. Classes 1 (finest) to 5. Use it when the cut edge itself is a specified feature.

ISO 2768

The general tolerance standard for linear and angular dimensions where no individual tolerance is stated. Classes f (fine), m (medium), c (coarse), v (very coarse).

Taper

The difference in kerf width between the top and bottom of the cut. Always present to some degree; increases with thickness and with focus set too high.

Striation

The vertical drag lines on a cut face. Regular fine striations indicate a good cut; coarse or irregular striations mean speed is too high for the power.

Burr

A raised edge of material remaining on the cut face. On laser cutting it usually indicates focus or gas problems rather than a blunt tool.

Materials

Mild steel (carbon steel)

The most common laser cutting material and the fastest to cut, thanks to oxygen-assisted exothermic cutting.

Stainless steel

Steel alloyed with chromium (and often nickel and molybdenum). Cut with nitrogen. Grades 304 and 316 behave differently: 316 contains molybdenum, which makes the melt more viscous and cuts roughly 5–15% slower.

Aluminium

Light, reflective and highly heat-conductive. Cuts more slowly than stainless at the same thickness and needs tight gas control because it reflects the beam.

Galvanised steel

Steel with a zinc coating. The zinc vaporises during cutting and produces fume that must be extracted; it can also affect the cut edge.

HSLA steel

High-strength low-alloy steel. Cuts similarly to mild steel but with a narrower process window on thick sections.

Titanium

Cuts well with fiber lasers using inert gas. Requires particular care over fume and oxygen exclusion because titanium reacts readily at temperature.

Reflective materials

Aluminium, copper and brass reflect a large fraction of the beam at CO2 wavelengths, which is why CO2 machines struggle with them and fiber machines do not.

Commercial terms

MOQ

Minimum order quantity. For capital equipment this is normally one machine; for accessories and spares it is set per item.

FOB, CIF, DDP

Incoterms defining where responsibility passes. FOB: buyer arranges freight from the origin port. CIF: seller pays freight and insurance to the destination port. DDP: seller delivers duty paid to the buyer's address.

Declaration of Conformity

The manufacturer's signed statement that a machine meets the applicable EU directives and standards. For most laser cutters this — not a third-party "CE certificate" — is the document that carries legal weight.

NRTL

Nationally Recognized Testing Laboratory, such as UL or ETL. In the United States an NRTL listing is normally required for the electrical installation to pass inspection.

Consumables

Parts that wear in normal use and are excluded from warranty: nozzles, protective windows, focus lenses, ceramic rings, belts and filters.

Lead time

Time from order to shipment. Depends on production scheduling, configuration and freight; always confirm it in writing on the order confirmation.