Vector and raster files
| Kind | Formats | Becomes | Notes |
|---|---|---|---|
| Vector | SVG, DXF, AI, PDF, EPS, DWG | Cuts and scored lines, and filled shapes | Scalable; the path is the toolpath; the usual way to cut |
| Raster | PNG, JPG, BMP, TIFF | Engraved pixels | Fixed resolution; dithered or grayscale (see Engraving, Marking and Raster Work) |
| Machine code | G-code (GRBL, Marlin, LinuxCNC), vendor formats (RD, LBRN, .job) | The commands the controller runs | Often generated by the software; read it to understand the machine (see CNC Machining) |
| Design formats | Fusion, Onshape, FreeCAD, Inkscape, Illustrator, AutoCAD | The source of the vector file | Keep the editable source; export a clean file |
- Prefer vector for cutting. A raster image has no path to cut.
- Units and scale are a common error: the same drawing can be exported at different resolutions.
- File size rarely matters for vectors (a 4 000-point drawing is about 64 kB) but raster images do: a 2 000 × 1 500 pixel gray image is 3.0 MB.
Preparing a vector file
Worked example: the scale trap
Illustration programs use points or pixels (72 or 96 per inch) while the laser works in millimeters. A 100 mm square exported at 96 dpi is 378.0 px; the same file read by software that assumes 72 dpi comes out 33.3 % too big (a ratio of 1.33): 100 mm becomes 133.3 mm. Check the size of the imported file against a known dimension, set the units explicitly, and cut a test square.
- Convert text to outlines (paths) before export, or the cutter will not find the font.
- Remove duplicates and overlaps: two lines on top of one another are cut twice (burn, flare). Use “delete duplicates” or merge paths.
- Close open paths where a closed shape is needed (a cut-out must be a closed loop, or the part falls out or the cut is incomplete).
- Join paths into continuous curves, so that the head does not stop at each joint.
- Simplify curves: too many nodes make a rough cut and a slow job; too few lose the shape.
- Draw at 1:1 scale, use millimeters and set the document size to the sheet.
- Use hairlines (0.01 to 0.1 mm line width) for cut lines if the software reads line width.
Worked example: arc tolerance and segment count
A controller or a G-code file approximates a circle by short straight segments. The largest deviation (the sagitta) of a chord is r (1 − cos(θ ÷ 2)). For a 20 mm radius circle to stay within 0.01 mm of the true circle each segment may turn by 0.063 rad, which means 100 segments of 1.26 mm: a smooth edge. With a coarse tolerance of 0.1 mm it is only 32 segments, and the circle shows facets under a magnifier. Set the export tolerance to a fraction of the kerf (0.01 to 0.02 mm).
Layers, colors and operations
Laser software (LightBurn, RDWorks, LaserGRBL, Lasercut, Trotec JobControl, Epilog Dashboard) groups the work into layers, usually identified by color, and gives each layer its own operation and settings: cut, score, engrave, with power, speed, passes, air, frequency and order.
| Layer (color) | Operation | Typical settings (3 mm plywood, 60 W, example) |
|---|---|---|
| Black | Raster engraving (filled areas, text, images) | 30 % power, 300 mm/s, 0.1 mm interval |
| Blue | Score or vector engrave (fold lines) | 15 % power, 60 mm/s |
| Green | Cut inside shapes (holes, slots, letters) | 75 % power, 20 mm/s |
| Red | Cut outlines, last | 75 % power, 20 mm/s |
- Order the layers: engrave first (while the sheet is flat and held), then score, then cut insides, then cut outsides.
- Save the settings with the material as a library entry (see Power, Speed, Focus and Assist Gas).
- Use “output” and “show” flags to run one layer at a time when testing.
Nesting and yield
Nesting arranges the parts on the sheet to use as little material as possible. The yield is the share of the sheet that becomes parts. The waste is paid for, so a better nest is a direct saving; nesting also shortens the travel, and cutting shared edges once saves time and material.
Worked example: the cost of waste
- The sheet is 400 × 300 mm = 120 000 mm² and costs $18.00. The 14 parts have a total area of 57 250 mm²: a yield of 47.7 %. The material in the parts costs $8.59 and the waste $9.41: 52 % of what you buy is thrown away.
- A better nest (rotating parts, filling holes with small parts, sharing edges) might reach about 65 to 75 %: on this sheet 12.60 dollars of parts instead of 8.59. Over a hundred sheets the difference is $401.
- Share cut lines. Where two rectangles touch along an edge, cutting that edge once saves its length. In this nest the shared edges (parts side by side with no gap) would save about 490 mm of cutting out of 3 650 mm. With kerf compensation the parts must be separated by a kerf, and the common edge is cut on the line between them, so the gap between parts is one kerf, not two.
- Keep a margin of several millimeters from the sheet edge (the sheet is not square and the edge may be damaged) and a gap of at least the sheet thickness between parts for thin webs.
- Use the sheet’s grain in wood: orient the parts so that strong direction goes where it is needed.
Cut order, lead-ins and travel
- Cut small inside features first, then the outlines, so that the part is still held when the delicate cuts are made.
- Cut a part’s inside holes before its outline, and the outline in one continuous loop.
- Use a lead-in: start a cut on the waste side with a short line (about 1 mm) that blends into the contour, so the pierce mark and the dwell burn are not on the finished edge; the lead-in takes about 0.05 s at 20 mm/s.
- Pierce points (where the beam first goes through) leave a bigger hole: keep them off the visible face and in the waste.
- Tabs (micro-joints) hold the part to the sheet so it does not fall or shift; cut them with a knife afterwards.
- Cut direction: clockwise or counter-clockwise for inside and outside, so that the kerf compensation lies on the waste side; the software sets it.
- Reduce heat build-up by alternating between areas of the sheet, not cutting a dense cluster in order.
Worked example: travel moves
Between cuts the head moves with the beam off (a “rapid”) at 400 mm/s. Visiting the 14 parts of the nest in random order covers 2 469 mm of travel (6.2 s); a nearest-neighbor order covers 1 064 mm (2.7 s), a saving of 57 %. The saving is a few seconds on this job but repeats with every sheet: enable “optimize cut path” (order by nearest neighbor) in the software. A rule: never let optimization break the inside-before-outside order.
Time estimates
Worked example: the whole nest
- Cutting length: the perimeters of the 14 parts add up to 3 650 mm; at 20 mm/s that is 183 s.
- Pierces: 14 × 0.30 s = 4.2 s.
- Travel: 2.7 s with an optimized order.
- Total: 189 s, about 3.2 minutes for the sheet (plus the time for the head to accelerate at corners, see Power, Speed, Focus and Assist Gas). The software’s estimate is usually within 10 % once the settings are right: use it to quote a job.
G-code and the controller
Many laser controllers run G-code (GRBL, GRBL-HAL, Marlin, Ruida in some modes). Understanding it helps in debugging. The important commands are G0 (rapid, beam off), G1 (cut move at the feed rate F with power S), G2 and G3 (arcs), M3 or M4 (laser on; M4 is dynamic power mode, where the power follows the speed so that corners do not burn), and M5 (off).
; A square cut at 20 mm/s, 45 % power, in GRBL laser mode ($32=1, spindle max S1000)
G21 ; millimetres
G90 ; absolute positions
G0 X10 Y10 ; rapid to the start, beam off
M4 S450 ; dynamic laser power, 45 %
G1 X50 Y10 F1200 ; feed in mm/min: 1200 mm/min = 20 mm/s
G1 X50 Y50
G1 X10 Y50
G1 X10 Y10
M5 ; beam offWorked example: powers and feed
| Power % | G-code | Light (80 W tube) |
|---|---|---|
| 10 % | S100 | 8.0 W (80 W tube, if linear) |
| 25 % | S250 | 20.0 W (80 W tube, if linear) |
| 45 % | S450 | 36.0 W (80 W tube, if linear) |
| 80 % | S800 | 64.0 W (80 W tube, if linear) |
- Feed rate is in mm per minute in G-code, mm per second in most laser software: 20 mm/s is F1 200. A common error is a speed 60 times wrong.
- GRBL settings: steps/mm (
$100,$101), here 80; maximum rate ($110), here 24 000 mm/min = 400 mm/s; acceleration ($120), 1 500 mm/s²; maximum travel ($130); laser mode ($32=1); spindle max ($30), here 1 000. - M4 versus M3: with M3 the power is constant, so corners (where the head slows) get too much; with M4 the controller scales the power with the actual speed. Use M4 for engraving and cutting.
Origin, framing and alignment
- Absolute coordinates are measured from the machine’s home (usually the top left), user origin from a point you set on the work, and current position from where the head is now. Choose one and check it before every job.
- Frame the job: run the head around the bounding box with the beam off (or at a very low “pointer” power) to see where the job will land on the sheet.
- Check that the job fits the work area: this job is 400 × 300 mm on a 600 × 400 mm bed: fits. The head may not reach the extreme corners (the limit switches take some of the travel).
- Jigs and registration: a pin jig or corner stops on the bed lets you repeat the position, and cut a second side or a print-and-cut job with registration marks and a camera.
- Camera alignment (on desktop machines) places the design over a photograph of the sheet; calibrate the camera and check the offset with a test cut.
Pre-flight checklist
| Check | Why |
|---|---|
| Size of the imported drawing against a known dimension | The scale trap |
| Closed paths, no duplicates, text as outlines | No missed or double cuts |
| Kerf offset applied once | Fits |
| Layer settings and order (engrave, score, inside, outside) | Quality and flat sheet |
| Job inside the work area, and framing run | No cuts off the sheet |
| Material loaded, flat, focus set, air on, lid closed, extraction on | Cut quality and safety (see Laser Safety, Fire and Fumes) |
| Estimated time reasonable | A wrong speed shows up |
| Someone stays with the machine | Fire |
Related
- Laser Cutting: the overview of this guide.
- Kerf, Accuracy and Designing Parts: kerf compensation in the file.
- Machine Hardware: Optics, Motion and Cooling: the controller and the motion that run the file.
- CNC Machining (G-code and CAM) and Data, Files and Parsing.
FAQ
Why is my part the wrong size?
Usually the import scale (72 against 96 dpi), the steps per mm, or no kerf compensation. Check the file against a known dimension and cut a test square.
What is the difference between M3 and M4?
M3 keeps the laser power constant; M4 (dynamic power) scales the power with the speed, so corners and starts do not burn. Use M4 for laser work.
How do I reduce waste?
Nest the parts tightly (rotation and filling gaps), share cut lines where it is safe, and use offcuts for small parts. Yield of 65 to 75 % is good for mixed shapes.
In what order should the cuts be made?
Engrave first, then score, then cut inside features, then the outlines, with a lead-in and an optimized travel path.
References
- GRBL documentation (laser mode, settings and G-code), LinuxCNC and Marlin documentation.
- LightBurn, LaserGRBL and machine makers’ software manuals for layers, nesting and cut order.
- ISO 6983 (numerical control of machines: G-code programming format).
Last reviewed: October 2026. Times, costs and settings are illustrative: use your own machine and material.