By Printara · Published 11 October 2026 · 16 min read
Laser-Cut Files: What to Check Before You Send Them to the Machine
Check that the file opens at 1:1 in millimetres, that every cut line is one closed path with no duplicate on top of it, that cut, score and engrave sit on separate colours or layers mapped to the right power and speed, and that text is converted to paths. Then check the fit: measure the real sheet with calipers, cut a kerf test and size the slots from it. Hold small parts so they cannot drop into the honeycomb, and cut one test joint before the whole sheet.
Short version. One supplier's tolerance on 3 mm plywood allows anything from 2.6 to 3.3 mm, so measure the sheet at four points and design to the reading. With the settings of the real job, cut a 20 mm square (kerf = 20.00 minus what it measures) and a comb of slots in 0.05 mm steps, starting about 0.3 mm under the sheet. Draw slots at the width the comb gives you with the kerf offset off, or at thickness plus play with the offset on, never both. Leave at least 1 mm between parts, and hold anything under 6 mm with tabs or a solid board.
Disclosure: Printara makes the laser-cut generator described in the last section. Everything before it works with any design tool and any laser.
The checklist
| Check | How | If you skip it |
|---|---|---|
| Sheet thickness | Calipers at four points; design to the reading, not the label | Slots that rattle or will not go together |
| Kerf and slot fit | A 20 mm test square and a slot comb, cut with the job's settings | Every joint loose by one kerf, or cracked when forced |
| Units and scale | Import, then measure a dimension you know | Parts 25.4 times too small or too big |
| Closed paths | Find open shapes and close or redraw them | No kerf offset, no fill engraving, parts left hanging |
| Duplicates and stray lines | Delete duplicates, guides, borders and construction lines | Lines cut twice: wider, darker kerf; cuts you did not want |
| Operations | One colour or layer per operation, each mapped to its settings | Score lines cut through, engraving cut out |
| Text | Convert to paths | A missing font replaced or dropped on the laser computer |
| Small parts | Tabs, or a solid board under them | Parts lost in the honeycomb or tipped up |
| Nesting and order | At least 1 mm between parts; engrave and score first, inner shapes before outlines | Charred bridges; parts that move before their holes are cut |
Measure the real sheet thickness
The thickness on the label is nominal. Kitronik, which sells laser plywood, gives its 3 mm birch sheets a tolerance of +0.3/-0.4 mm: anything from 2.6 to 3.3 mm. The next batch can sit somewhere else in that range, so measure every new stack.
- How: digital calipers, jaws flat on the faces, a little in from the edge where the plies may be crushed. Take at least four readings, near the corners your parts will come from, and write them on the sheet.
- Which number: size slots for the thickest reading if every joint must go together by hand. Joints from thinner spots will be slightly looser, which is fine if you glue.
- Flatness: Kitronik notes that plywood often bows or twists, has measured more than 25 mm of rise between the centre of a sheet and a corner, and says to strap or tape sheets to the bed. A bowed sheet changes the focus distance across the bed, so the kerf and the cut quality change with it.
How thickness and kerf change the fit
Kerf is the width of material the beam burns away. The beam is centred on your line, so each cut edge moves about half a kerf away from it: holes and slots come out one kerf bigger than drawn, outlines and tabs one kerf smaller. The fit is what is left between the cut slot and the real sheet:
cut slot = drawn slot + kerf play = cut slot - measured sheet thickness drawn slot = measured thickness + play - kerf (kerf offset off) drawn slot = measured thickness + play (kerf offset on)
A real case: a Fab Academy group with an 80 W CO2 laser cut a comb of slots from 2.80 to 3.20 mm in nominal 3 mm plywood. The snug fit was the 2.80 mm slot, the narrowest they had cut, a fifth of a millimetre under the label. Your machine, focus, power, speed and sheet will give a different number, so test, and start the comb below the sheet thickness.
- Play is a separate decision from kerf. Kerf is what the laser takes; play is what you want left: none or slightly negative for a press fit, a little for parts you slide together and glue.
- Thickness errors add up where parts stack. Ten layers of a nominal 3 mm sheet that measures 3.2 mm stand 2 mm taller than drawn. Kerf does not add up this way: the beam stays centred on your lines, so every joint is loose or tight by the same amount.
- Kerf is not a fixed number for your machine. It changes with material, thickness, focus, power and speed. In thick stock the cut is not perfectly square through the sheet, so test in the thickness you will use and cut every part with the same face up.
Run a kerf test and size the slots from it
Two small tests, cut on the same sheet with exactly the power, speed and focus of the real job:
- Kerf square. Cut a 20.00 mm square and measure it in both directions. Kerf = 20.00 minus the reading. A square that measures 19.84 mm means a 0.16 mm kerf. The offset that brings outlines and holes back to their drawn size is half of that, 0.08 mm, because each edge loses half the kerf.
- Slot comb. Cut a strip with slots in 0.05 mm steps from about 0.3 mm under your measured thickness up to the thickness itself, for example 2.80 to 3.10 mm for a sheet that measures 3.08 mm, with each width scored or engraved next to its slot. The kerf makes every slot wider than drawn, so the snug fit sits under the sheet thickness. Push an offcut of the same sheet into each one. The narrowest slot it enters by hand is your slide fit; one step narrower is a press fit you tap home.
The comb already includes your kerf. Use its number as the drawn slot width with the kerf offset off. If you would rather keep the drawing at true size, draw slots at thickness plus play and turn the offset on. Doing both compensates twice: in the worked example below that makes the slot 0.13 mm narrower than the sheet.
Where the offset lives. In LightBurn, Kerf Offset shifts the beam path off your line when the job is sent, without changing your drawing, and it only works on closed shapes. LightBurn also publishes a kerf test file with a vernier scale that gives you the value to enter. Other programs call it kerf, offset or beam compensation. Whatever the name, check the preview: outlines should grow and holes and slots should shrink. Box generators take it as a parameter: boxes.py asks for the material thickness and a burn correction (bigger values for a tighter fit), and its BurnTest generator cuts shapes to find the value.
Units: open the file at 1:1 in millimetres
Import the file, then measure something you know: the sheet outline, the length of a part, a hole for a known bolt. If it is 25.4 times too small or too big, inches and millimetres were mixed up.
- DXF is the usual suspect. Its coordinates are bare numbers with no unit attached; the unit comes from a header value ($INSUNITS), and when that is missing or not read, the importer assumes one. Set your laser software's DXF import unit to millimetres, then measure.
- SVG can carry its size in millimetres on the document itself. One saved in pixels depends on the resolution the importer assumes, which is why the same file can open at different sizes in two programs. Save SVGs with the document units in millimetres.
- One format, once. If you have both an SVG and a DXF of the same sheet, import one of them. Both together put every line on the sheet twice.
Closed paths, duplicate lines and stray geometry
Closed paths. A cut outline must be one closed path whose start and end are the same point. An open path still cuts as a line, but kerf offset and fill engraving only work on closed shapes, and a gap wider than the kerf leaves a bridge that holds the part in the sheet. Imported DXFs often bring outlines in as separate line and arc segments. LightBurn's Close Selected Paths With Tolerance joins ends that are almost touching; in a drawing program, join the nodes and check that the shape fills.
Duplicates. Two identical lines on top of each other cut twice: a wider, darker kerf and more charring on wood. On a fill layer, LightBurn warns, duplicates can stop the shape from engraving at all. They come from copy and paste, from importing two formats of the same file and from parts that share an edge. LightBurn's Edit > Delete Duplicates removes exact copies (the objects must be ungrouped), and its Cut Planner can remove overlapping lines between parts that share an edge.
Stray geometry. Delete everything that is not meant to burn: construction lines, dimensions, guides, a page border, hidden layers, stray points. The laser treats whatever sits on an active layer as work.
Cut, score and engrave: map colours to operations
Cut goes through the sheet along the outline, score burns only the outline into the surface, and engrave works the closed area inside the outline (xTool's definitions). The file needs one colour or layer per operation, and which colour means what is not standard:
- Ponoko, an online cutting service, recommends a blue stroke for cutting, a red stroke for line engraving and a grey fill for area engraving, and lets you assign any colour when you upload.
- Printara's SVG files use red for cut, green for score and blue for engrave: Ponoko's cut colour is Printara's engrave colour.
- Epilog goes by line width: its setup guide for printing from Illustrator asks for 0.001 in (0.072 pt) lines for vector cutting and thicker lines for raster engraving, in RGB colours.
- LightBurn treats every colour as a layer with its own settings. Line mode traces the path, which cuts or, at low power or high speed, scores. Fill mode engraves parallel lines inside closed shapes.
Before you cut, list every colour in the file and give each one a mode, power, speed and number of passes. A score line left on the cut layer cuts straight through.
| Operation | What the laser does | In the file | In LightBurn | Printara SVG | Printara DXF layer |
|---|---|---|---|---|---|
| Cut | Goes through the sheet along the line | Closed path, stroke only | Line mode, cutting power and speed | Red stroke | CUT |
| Score | Burns the line into the surface | Path, open or closed, stroke only | Line mode, low power or high speed | Green stroke | SCORE |
| Engrave | Removes material inside the shape | Closed shape with a fill | Fill mode | Blue fill | ENGRAVE and ENGRAVE_FILL (set ENGRAVE_FILL to a fill operation) |
Order. Engrave and score first, cut last, so nothing has dropped or shifted when the head comes back. Within the cuts, inner shapes before the outline around them. In LightBurn, Order by Layer follows the order of the layers in the Cuts / Layers window, and Cut inner shapes first cuts the inner object before the outer one.
Which online tools support cut, score and engraving?
A design tool only has to keep the three operations apart in the file. The program that drives the laser is where each one gets its power and speed.
- In a browser, from file to laser: the Glowforge app at app.glowforge.com lets you set each part of a design to cut, score, engrave or ignore, for Glowforge machines. Ponoko has you pick a laser action for each colour when you upload, then cuts the parts for you.
- On the desktop, driving the laser: LightBurn (cut and score are Line layers, engraving is a Fill layer) and xTool Studio, where Score, Engrave and Cut are separate processing types and Score and Cut work on vectors only.
- In a browser, designing: Cuttle is a vector editor made for laser cutting; you keep score and cut on different colours in the SVG and assign them in your laser software. boxes.py generates boxes and other parts from thickness and burn values. Printara designs a whole kit from a written brief and writes the operations as colours in the SVG and as layers in the DXF.
Convert text to paths
Live text depends on the font being installed on the computer that runs the laser; a missing font gets replaced or dropped. Convert text to outlines before you export: in Inkscape, Path > Object to Path (Ctrl+Shift+C); in Illustrator, Type > Create Outlines. Keep an editable copy, because converted text cannot be retyped.
- Text cut through a panel loses the centres of O, A, B, D, P, R, a and e unless you bridge them to the rest or use a stencil font.
- Engraved letters need strokes thick enough to read. Ponoko notes that area engraving is not very crisp on text and thin areas under 1 mm, and suggests combining area and line engraving: a fill with a scored outline around it.
Small parts and the honeycomb
Ponoko notes that parts smaller than 6 mm can fall through the laser bed and be lost, and that features under 1 mm are likely to be fragile. A small part that tips up when its outline closes can also stand in the path of the head for the rest of the job.
- Tabs. Leave short uncut gaps that hold the part in the sheet until the job ends, then snap it out and sand the nub. LightBurn's Add Tabs places them on the shapes you pick.
- A solid board. Cut a sheet of tiny parts over a flat scrap board instead of the honeycomb, so nothing can drop.
Nesting and material use
- Spacing. Ponoko recommends at least 1 mm between elements of a design. On wood, more space keeps thin strips between parts from charring or breaking out.
- Shared edges. Rectangles that touch can share one cut line, which saves material and time, but the shared edge must be cut once: remove the overlap, or it is cut twice.
- Fill the waste. Rotate parts and put small parts inside the cut-outs of big ones; as inner shapes, they cut before the outline around them.
- Your real sheet. Set the sheet size in the design tool to the sheet or offcut you actually have, with a margin for the edge and for whatever holds the sheet down.
- Grain. Keep the face grain running the same way on parts that sit side by side. On solid wood, also run thin parts along the grain: across it they snap.
Worked example: prototyping a ribbed wooden display stand
A ribbed stand is a row of identical profiles, the ribs, held by rails that slot through them like an egg crate. Every rib meets every rail, so a slot error repeats at every joint. Say you want a stand that holds a tablet at an angle, cut from 3 mm birch plywood on 300 x 200 mm sheets. The readings below are an illustration of the method, not a test we ran.
| Part | Size | Joint |
|---|---|---|
| 7 ribs | About 110 mm deep and 150 mm tall, with a front lip and a back the tablet leans on | Two slots, 12 mm deep, from the bottom edge |
| 2 rails | 180 x 24 mm | Seven slots, 12 mm deep, from the top edge, 25 mm apart |
| Assembled | 150 mm from the first rib to the last, 15 mm of rail beyond each end | Halving joints: rib and rail bottoms sit flat on the table |
- Get the shape right cheaply. Cut one rib in cardboard, stand the tablet against it and check the angle, the lip and how far it leans. Cardboard tells you about shape, not fit: it is not your plywood's thickness.
- Measure the plywood. Say the four corners read 2.96, 3.04, 3.08 and 2.98 mm. Design to 3.08 mm so every joint goes together.
- Run the two tests. Say the 20.00 mm square measures 19.84 mm: kerf 0.16 mm, offset 0.08 mm. On a comb from 2.80 to 3.10 mm, an offcut from the thickest corner slides into the 2.95 mm slot by hand and needs a tap in the 2.90 mm one. That matches the math: 2.95 + 0.16 = 3.11 mm, 0.03 mm more than the sheet.
- Draw the slots. 2.95 x 12 mm in every rib and rail with the kerf offset off, or 3.11 x 12 mm with the offset on at 0.08 mm. Not 2.95 mm with the offset on: that slot cuts at 2.95 mm, 0.13 mm narrower than the sheet.
- Make the slot width one number. There are 28 slots (14 in the ribs, 14 in the rails). Keep their width as one parameter or one copied shape, so a new batch of plywood is one edit, not 28.
- Cut a test section. Two ribs and two 60 mm pieces of rail, each with two slots. Check that the ribs stand square, the bottoms sit flat and the tablet sits where the cardboard said. Push the tablet from the front: if the stand tips, make the ribs deeper at the back.
- Nest the full set. Two ribs side by side take about 225 mm of the 300 mm width; the strip under the 150 mm ribs takes one rail. Seven ribs and two rails fit on four sheets. If the rib profile allows, turning every second rib by 180 degrees nests them closer.
- Glue on a flat surface. Check that the ribs are square to the rails before the glue sets.
What Printara exports, and what it leaves to you
Printara's laser-cut generator works from the other end: you describe the object, its size and how it goes together, and it designs the flat parts and nests them on your sheet. The checks above still apply to its files. What it does and does not do, from the AI Laser Cut Generator page on 11 October 2026:
- Setup. In Printara Studio, open Sculpt and choose Laser cut. Set the Material thickness (0.5 to 25 mm) and the Sheet width and height (50 to 1500 mm), or start from 3 mm plywood, 3 mm MDF, 2 mm acrylic or 4 mm plywood. You can also set the sheet margin, the spacing between parts and whether parts may turn 90 degrees to fit.
- Fit. The Fit clearance (0.1 mm unless you change it, from 0 to 2 mm) is the total play added to every slot. Printara never applies kerf: the sheets carry nominal contours. So type the thickness you measured and turn the kerf offset on in your laser software; each slot then cuts at thickness plus clearance. Without the offset, every slot cuts one kerf wider than that.
- Files. An SVG and a DXF for every sheet, at true size in millimetres. The SVG uses red for CUT, green for SCORE and blue for ENGRAVE, with fill engraving as filled blue shapes. The DXF is R12 with the layers CUT, SCORE, ENGRAVE and ENGRAVE_FILL; set ENGRAVE_FILL to a fill operation and check the toolpath preview. You also get the assembled model as STL, 3MF and GLB and a Parts ZIP with one STL per part; keep those out of the laser software.
- Before you cut. The quote asks when something is unclear (in the Academy lesson it asked about the lettering, the headphone clearance and whether everything had to fit on one sheet), and Preview shows each sheet before you download it. Some kits come with fit-test coupons, like the two on the Gothic jewelry box sheet above.
- Limits. Printara does not test the files on specific machines: import one format, check the scale and the layer mapping, and cut a test piece first. Material preview changes the look of the 3D view only, never the cutting files.
- Cost. The account is free and so is the quote. Building uses credits from a plan or a credit pack, the quote shows the number before you confirm, and credits come back automatically if a build fails. Paid plans start at €3.99 a month for 150 credits; a 300-credit pack is €4.90 with a plan or €9.90 without, on the pricing page.
The Academy lesson Design a laser-cut headphone stand (3 min 36 s, narrated in seven languages) goes from a reference image to the SVG and DXF download, and ends where this guide starts: check scale, thickness and fit before cutting the full kit.
Design a laser-cut kit
Describe the object, its size and your sheet. The quote is free and shows the credits before you build.
Open Sculpt How the generator worksFAQ
What colours should cut, score and engrave lines be?
There is no universal standard. Printara's SVGs use red for cut, green for score and blue for engrave; Ponoko recommends blue for cutting, red for line engraving and grey fill for area engraving; Epilog's setup guide goes by line width. Use one colour per operation and map each one to its settings in your laser software before you cut.
How do I measure the kerf of my laser?
Cut a 20.00 mm square with the settings of the real job and measure it with calipers. The kerf is 20.00 minus the reading, so a 19.84 mm square means 0.16 mm. The kerf offset for outlines and holes is half of that. Test again when the material, thickness, focus, power or speed changes.
Should a slot be the same width as the material?
Not as drawn. A slot cuts one kerf wider than you draw it, and the sheet is rarely its nominal thickness. Draw the slot at measured thickness plus play minus kerf with the kerf offset off, or at measured thickness plus play with the offset on. A comb of test slots in 0.05 mm steps gives you the number directly.
Should I send SVG or DXF to my laser?
Whichever your laser software imports reliably. An SVG can carry its size in millimetres and a colour per operation; a DXF stores bare numbers, so set the import unit to millimetres and measure a known dimension. Import one of them, never both of the same sheet.
Why did my laser cut the same line twice?
Because there are two lines there. Duplicates come from copy and paste, from importing two formats of the same file and from parts that share an edge. Delete exact duplicates (in LightBurn, Edit > Delete Duplicates) and let the cut planner remove overlapping lines on shared edges.
Do I need to convert text to paths before laser cutting?
Yes. Live text depends on the font being installed on the computer that runs the laser. Convert it to outlines (Inkscape: Path > Object to Path; Illustrator: Type > Create Outlines) and keep an editable copy.
Sources, checked on 11 October 2026: plywood tolerance and bow from Kitronik's 3 mm birch laser plywood page; the slot comb result from the Fab Academy 2024 Lakemac group assignment; LightBurn's documentation on Line mode and Kerf Offset, kerf testing, layer modes, colours and layers, Delete Duplicates, closing paths, optimization settings and tabs; Ponoko's help on colours and design quality; Epilog's graphics software setup; xTool on engrave, score and cut and on Score and Cut in xTool Studio; ezdxf on DXF units; boxes.py BurnTest; NAU Cline Library's Glowforge guide; Cuttle on scoring; SendCutSend on text in Inkscape. Printara details are from the AI Laser Cut Generator page, the Academy lesson and the pricing page on the same date. The worked example's readings are an illustration, not a test we ran.
About Printara. Printara is an AI-powered creative manufacturing platform for creating 3D models, dioramas, laser-cut designs, molds and printable products. Questions or corrections: hello@printara.co.