Words the trade uses

Focus

Setting the lens the right height above the material so the beam narrows to its smallest, sharpest point right at the surface. Out of focus, the dot spreads and cuts weakly.

Air assist

A stream of air blown at the cutting point through the nozzle. It pushes away smoke and flame, so cuts are cleaner, edges scorch less, and the lens stays protected.

Focal length

The distance from the lens to the point where the beam is at its narrowest. A shorter one gives a finer point for detail; a longer one keeps a usable point deeper into thick material.

Spot size

How wide the beam is where it meets the material. At the focal point it is smallest and cuts best; above or below it spreads and only scorches.

Mirror alignment

Setting the mirrors so the beam lands in the same spot on the head wherever the head is on the bed. Out of alignment, a machine cuts well at one corner and badly at the other.

Nozzle

The cone under the lens that the beam and the air leave through. A small opening focuses the air on the cut; a damaged or dirty one throws the air sideways.

Water cooling

A CO2 tube turns most of its power into heat and has to have water moving through it. Fire it dry, even for a moment, and the glass cracks.

Power and speed

The two numbers that decide everything. How much energy lands in one place is power divided by speed, so the same depth can come from high power moving fast or low power moving slowly, and the two are not equal in how they burn.

Tube life

A CO2 tube weakens as it is used and does not announce it. Counted in hours of actual firing, not hours the machine was switched on.

Kerf

The strip of material the laser beam burns away as it cuts. It is usually about 0.1 to 0.3 mm wide, so a finished part comes out very slightly smaller than the line you drew.

Kerf offset

Shifting the cut line out by half the kerf so the finished part measures exactly what you designed. Cut on the outside of a shape and the inside of a hole.

Nesting

Arranging parts close together on the sheet so they use as little material as possible and leave less scrap.

Score

A shallow line that marks or etches the surface without cutting through. Done with low power or high speed, often to show a fold line or a light outline.

Lead-in and lead-out

A short extra path added before and after a cut so it starts and stops just off the visible edge. This hides the small mark left where the beam switches on and off.

Home and origin

The fixed corner the machine measures every position from. On most machines it is a back corner. All coordinates are distances from this point.

Passes

One trip of the laser over the design is a pass. Thick material is cut with several passes, each going a little deeper, instead of one slow high-power pass.

Taper

A laser cut is slightly wider at the top than the bottom, so the edge is not square. It matters when parts stack, when two edges meet, and on anything over about 6 mm.

Charring

The brown or black marking left when smoke and flame stay at the cut instead of being blown away. Usually air assist, sometimes speed, sometimes the material.

Overburn

The extra mark where the beam turns on and off in the same place, because it dwells there for a moment at each end. Lead-ins move it off the visible edge.

Common line cutting

Two parts that touch share the edge between them, so the beam travels it once rather than twice. Faster, less material, and no thin sliver of waste to fall through the bed.

Cut order

The sequence the shapes are cut in. It decides how far the head travels between them, and it decides whether a part drops out of the sheet before the cuts near it are finished.

Travel

The movement between cuts, with the beam off. It burns no material and plenty of time, which is why the order shapes are cut in is worth optimising.

Rapid move

A move at the machine\u2019s fastest speed with the beam off. The head accelerates hard, so a rapid is where a loose belt or a bad bearing shows itself first.

Honeycomb bed

An open metal grid the material rests on, so the beam has somewhere to go once it is through. It marks less than solid slats and clogs with resin over time.

Slat marks

The lines left on the underside where the sheet rests on whatever holds it. The beam comes through, hits the support and bounces back. Raising the work a few millimetres removes them.

Tabs and bridges

Small stretches deliberately left uncut so a finished part stays in the sheet instead of dropping through the bed or shifting while the rest is cut.

Offcut

What is left of a sheet once the parts are out. Big enough to cut from again and impossible to find later, unless somebody wrote down what is on the rack.

Offcut rack

Finger joint

Interlocking teeth cut into two edges so they slot together into a strong corner, like the fingers of two hands laced together. The go-to joint for boxes.

Tab and slot

A sticking-out tab on one part that drops into a matching slot on another. It holds pieces square while the glue sets.

Dogbone (corner relief)

A small round notch added to an inside corner so a square tab can seat all the way in. Without it, leftover material in the corner stops the tab short.

Corner relief (dogbone)

Living hinge

A grid of thin slits cut into stiff material so a flat panel can bend like a hinge. Used for curved lids and wrap-around shapes.

Raster and vector

Vector cuts follow lines, so the head traces each path once, for cutting and scoring. Raster engraving sweeps back and forth like an inkjet to fill an area, for photos and solid fills.

DPI

Dots per inch: how closely the engraving dots sit together. Higher DPI gives smoother detail but takes longer and can over-burn.

Dithering

Turning a photo into a pattern of tiny dots so the laser can suggest shades of gray using only burnt or unburnt spots. Darker areas get denser dots.

Hatch fill

Filling a shape with closely spaced parallel lines so the laser engraves the whole area. The line spacing sets how solid the fill looks.

Scan gap

The distance between one sweep of an engrave and the next, sometimes called line interval. Close together is smooth and slow; far apart is quick and striped.

Overscan

Letting the head run past the edge of the picture before it turns around, so it is at full speed everywhere inside it. Without it the ends of every line are darker than the middle.

Halftone

Shading built from marks of different sizes rather than different darknesses, because the laser has only burnt and not burnt. Bigger dots read as darker from a step back.

Bidirectional scanning

Engraving on the way out and on the way back rather than only one way. Close to twice as fast, and it exposes any misalignment between the two directions.

Scan offset

The correction that lines up the two directions of a bidirectional engrave. Without it text looks doubled or ragged, and it changes with speed, so it is measured at the speeds you use.

Engrave depth

How far into the surface the beam has taken. Set by power, speed and the number of passes, and limited by the material long before it is limited by the machine.

Registration marks

Reference marks, usually small crosses or dots, that you or the camera line up on to place a cut exactly onto an already printed sheet. The heart of print and cut.

Path and node

A path is the line the beam follows, and a node is one of the points it is built from. Editing a shape means moving nodes; the handles on a node bend the line into and out of it.

Open and closed path

A closed path ends where it started. An open one does not, and until it does the shape cannot be filled, offset or turned into a joint, because there is no inside.

Duplicate lines

Two lines lying on top of each other, usually from an export or a paste. The beam cuts the line, then cuts it again through the cut it just made, which doubles the time and scorches the edge.

Boolean operations

Making one shape out of two: joining them, taking one out of the other, or keeping only where they overlap. How a plate with holes in it is drawn.

Weld

Stroke to path

Turning a line that has thickness into the outline of that thickness. A laser cuts a line, so a drawing that means a 3 mm bar has to say so as a shape, not as a thick pen.

Layer

A group of shapes that share one set of settings and one job: cut at these numbers, engrave at those, or do not go to the machine at all. Usually shown as a colour.

Print and cut

Cutting around something already printed. The sheet carries marks in known places, the camera reads where they actually landed, and the cut is bent to follow the print rather than the bed.

Units

A DXF can carry no unit at all, so a drawing made in millimetres and one made in inches look identical to whatever opens them. This is why a part arrives 25 times too big or too small.

Cast and extruded acrylic

Two ways of making the same plastic. Cast engraves to a frosty white and is what signage uses; extruded stays nearly clear when engraved and cuts a little faster. Both cut cleanly.

PVC and vinyl

Never put it in the machine. Cutting it releases chlorine gas, which corrodes the rails, the optics and the electronics, and harms whoever is standing there. If a sheet is unlabelled, do not guess.

Plywood and MDF

Plywood is layers with glue between them, and the glue lines cut differently from the wood, so the same settings can cut through one sheet and stall in the next. MDF is even all the way through and more predictable, and it smells.

Anodised marking

On anodised aluminium the beam removes the colour rather than the metal, leaving a permanent white mark. It is marking, not engraving, and a CO2 machine cannot cut the metal itself.

Interlock

A switch that stops the beam firing when it should not: the lid open, the water not moving, the extraction off. The one safety feature that has to work whatever anybody has clicked.

Extraction

The fan and ducting that pull smoke out of the machine. Weak extraction shows up first as haze on the lens and edges that will not come clean, and it is what stands between the fumes and the room.

Backlash

Play in the belts or bearings, so the head arrives in a slightly different place depending on which way it came. It shows as doubled edges on an engrave and corners that do not meet.

Limit switch and homing

The switch the head touches when it goes looking for its corner at startup. Everything the machine knows about position is measured from there, so a switch that is loose moves every job.

Controller

The box inside the machine that turns a file into movement and beam. On these machines it is a Ruida, and it holds settings of its own that outlast whatever software is talking to it.

Rotary

An attachment that turns the work under the head so a cylinder can be engraved all the way round. The machine still thinks it is moving in a straight line, so the software scales one axis to match the diameter.