{"course":{"slug":"vector-and-print","title":"Vectors, Logos and Things That Get Printed","url":"https://addaly.com/learn/vector-and-print","level":"beginner","track":"create"},"lesson":{"slug":"laser-cutting-and-engraving","title":"Laser cutting, kerf, and the material you must never use","url":"https://addaly.com/learn/vector-and-print/laser-cutting-and-engraving","position":69,"of":73,"minutes":8,"answer":"A laser distinguishes cut from engrave by stroke and colour on named layers, removes a kerf of 0.1 to 0.3 mm that must be measured on the real material before parts will fit.","keyIdea":"A laser distinguishes cut from engrave by stroke and colour on named layers, removes a kerf of 0.1 to 0.3 mm that must be measured on the real material before parts will fit, and must never be used on PVC or any other chlorine-bearing plastic."},"body":{"format":"markdown","text":"## Two operations, one machine\n\nA laser cutter does two different things and your file must say which is which.\n\n- **Vector cut**: the head follows a path at speed, the beam cutting through. Driven by paths.\n- **Raster engrave**: the head sweeps back and forth like an inkjet, pulsing the beam to burn a surface image. Driven by a bitmap, generated from your fill.\n\nMost machines distinguish them by **colour convention**: a hairline stroke of one colour means cut, another means score, and black fill means engrave. **The convention varies by machine and driver**, so ask the operator rather than trusting any rule you read, including this one. What is universal is that the distinction is made by colour and stroke, so keep them on separate, clearly named layers.\n\n## Kerf, and why the parts do not fit\n\nThe beam removes material as it travels. That removed width is the **kerf**, typically **0.1 to 0.3 mm** depending on material, thickness and focus.\n\nThe consequence:\n\n> Figure: Kerf, measured on the material itself. Bars (mm removed by the beam): 1 mm card 0.12; 3 mm acrylic 0.2; 3 mm plywood 0.25; 6 mm MDF 0.3. Cut a 20 mm square from a scrap, measure the square and the hole with callipers, and half the difference is your kerf. A hole comes out one kerf larger and the part one kerf smaller, so two pieces drawn to slot together exactly are loose by two.\n\n- A cut-out hole comes out **larger** than drawn, by one kerf.\n- A cut-out part comes out **smaller** than drawn, by one kerf.\n- So two parts drawn to slot together exactly will be loose by two kerfs: about 0.4 mm, which is a wobbly joint.\n\nMeasure it rather than guessing. The standard test: cut a 20 mm square from a scrap of the actual material, measure the square and the hole with callipers, and the difference divided by two is your kerf.\n\n```\nhole measured  20.22 mm\npart measured  19.78 mm\ndifference      0.44 mm  →  kerf 0.22 mm\n```\n\nThen offset your paths by half a kerf in the appropriate direction for a press fit, or design the clearance in deliberately.\n\n## Closed paths, always\n\nA cut path must be **closed**. An open path leaves the piece attached by whatever gap remains, and it has to be snapped or cut free by hand, leaving a mark. This is the same discipline as the plotter: weld overlaps, close every loop, remove duplicates.\n\nDuplicate paths matter more here than anywhere. Two identical paths stacked means the laser cuts the same line twice, which on thin material burns a wide, charred channel.\n\n## Material safety, which is not optional\n\n**Never cut PVC, vinyl, or anything containing chlorine.** Lasering PVC releases **hydrogen chloride gas**, which corrodes the machine's optics and rails and is seriously harmful to breathe. Sign vinyl is PVC. This is the single most important fact in this lesson, and reputable shops refuse the material outright.\n\nAlso refuse or check carefully:\n\n- **Polycarbonate**: burns rather than cutting, yellows the edge, smokes badly.\n- **ABS**: melts and produces cyanide compounds.\n- **Fibreglass and carbon fibre**: resin fumes and abrasive dust.\n- **Anything you cannot identify.** If the client cannot say what a sheet is made of, do not put it in a laser.\n\nSafe and common: **plywood and MDF** (both give a charred edge, which is a look), **acrylic / PMMA** (cuts beautifully with a polished edge; cast acrylic engraves frosted white, extruded does not), **paper and card**, **leather** (vegetable tanned, not chrome), **fabric**, **cork**, **anodised aluminium** for marking.\n\n## Living hinges and the things a laser makes possible\n\nA **living hinge** is a pattern of interlaced slots cut into rigid sheet that makes it bend. The spacing, slot length and gap determine the bend radius, and it is worth cutting a test strip in the actual material rather than copying numbers.\n\nSimilarly, **inlay** work, **stacked layers**, **engrave-then-cut** sequences: all are just ordering operations correctly in the file and on the machine.\n\n## The software\n\n- **LightBurn** is what most small shops run. Paid, inexpensive, one-off licence, and good: layer-based, per-layer power and speed, kerf offset built in, and it drives most common controllers.\n- **Inkscape plus a CAM extension** (Gcodetools, or the several laser plugins) is the free route and works, with more friction.\n- **The machine's own driver**, often a printer driver where you \"print\" from any application, using colours for operations.\n\nSend SVG, DXF or PDF at 1:1 in millimetres, with layers named `CUT`, `SCORE` and `ENGRAVE`, and put the material and thickness in the filename."},"check":{"question":"A designer draws two plywood parts to slot together, with a 6 mm tab and a 6 mm slot, and sends the file for laser cutting. The joint comes out loose. What is the arithmetic?","options":[{"text":"The tab cuts 6 mm minus one kerf and the slot 6 mm plus one, so the gap is two kerfs.","correct":true},{"text":"Plywood expands when heated by the beam, so both features come out oversized and the fit is lost.","correct":false,"tempting":"Charring removes material rather than adding it, and any thermal expansion has reversed by the time the part is handled."},{"text":"The kerf applies only to the outer cut, so the slot is correct and the tab is undersized by one kerf.","correct":false,"tempting":"Kerf applies to every cut the beam makes, inside and outside. Both features are affected, in opposite directions."},{"text":"The file was drawn in inches and then converted, introducing a rounding error of about 0.4 mm on a 6 mm feature.","correct":false,"tempting":"A unit conversion error would scale everything, not just the joint, and 0.4 mm on 6 mm is far larger than any rounding in a conversion."}]},"prev":{"slug":"embroidery-digitising","title":"Embroidery, which does not use vectors at all","url":"https://addaly.com/learn/vector-and-print/embroidery-digitising"},"next":{"slug":"cnc-and-built-up-letters","title":"CNC routing, tool radius, and the letters on a shop board","url":"https://addaly.com/learn/vector-and-print/cnc-and-built-up-letters"},"authorship":"Founder and series editor: Dr Mustafa Mun. Written by AI models to a written standard. Exam keys checked blind by a second model: 3,665 of 3,666 agreed. Academic review invited.","review":{"status":"Draft, open for academic review"},"cite":"Addaly (2026) 'Laser cutting, kerf, and the material you must never use', in Vectors, Logos and Things That Get Printed. Edited by M. Mun. Addaly. Available at: https://addaly.com/learn/vector-and-print/laser-cutting-and-engraving (Accessed: 13 October 2026).","licence":{"name":"CC BY-NC-SA 4.0","url":"https://creativecommons.org/licenses/by-nc-sa/4.0/"},"reader":{"schema":1,"title":"Laser cutting, kerf, and the material you must never use","courseTitle":"Vectors, Logos and Things That Get Printed","module":{"index":8,"slug":"machines-that-make-things","title":"Machines that cut, stitch and burn"},"answer":null,"keyIdea":"A laser distinguishes cut from engrave by stroke and colour on named layers, removes a kerf of 0.1 to 0.3 mm that must be measured on the real material before parts will fit, and must never be used on PVC or any other chlorine-bearing plastic.","hero":{"kind":"figure","figure":{"t":"figure","label":"Figure","figure":{"type":"bars","unit":"mm removed by the beam","title":"Kerf, measured on the material itself","series":[{"label":"1 mm card","value":0.12},{"label":"3 mm acrylic","value":0.2},{"label":"3 mm plywood","value":0.25},{"label":"6 mm MDF","value":0.3,"highlight":true}],"caption":"Cut a 20 mm square from a scrap, measure the square and the hole with callipers, and half the difference is your kerf. A hole comes out one kerf larger and the part one kerf smaller, so two pieces drawn to slot together exactly are loose by two."},"alt":"Figure: Kerf, measured on the material itself. Bars (mm removed by the beam): 1 mm card 0.12; 3 mm acrylic 0.2; 3 mm plywood 0.25; 6 mm MDF 0.3. Cut a 20 mm square from a scrap, measure the square and the hole with callipers, and half the difference is your kerf. A hole comes out one kerf larger and the part one kerf smaller, so two pieces drawn to slot together exactly are loose by two."}},"blocks":[{"t":"h2","id":"two-operations-one-machine","runs":[{"text":"Two operations, one machine"}]},{"t":"p","runs":[{"text":"A laser cutter does two different things and your file must say which is which."}]},{"t":"ul","items":[[{"text":"Vector cut","b":true},{"text":": the head follows a path at speed, the beam cutting through. Driven by paths."}],[{"text":"Raster engrave","b":true},{"text":": the head sweeps back and forth like an inkjet, pulsing the beam to burn a surface image. Driven by a bitmap, generated from your fill."}]]},{"t":"p","runs":[{"text":"Most machines distinguish them by "},{"text":"colour convention","b":true},{"text":": a hairline stroke of one colour means cut, another means score, and black fill means engrave. "},{"text":"The convention varies by machine and driver","b":true},{"text":", so ask the operator rather than trusting any rule you read, including this one. What is universal is that the distinction is made by colour and stroke, so keep them on separate, clearly named layers."}]},{"t":"h2","id":"kerf-and-why-the-parts-do-not-fit","runs":[{"text":"Kerf, and why the parts do not fit"}]},{"t":"p","runs":[{"text":"The beam removes material as it travels. That removed width is the "},{"text":"kerf","b":true},{"text":", typically "},{"text":"0.1 to 0.3 mm","b":true},{"text":" depending on material, thickness and focus."}]},{"t":"p","runs":[{"text":"The consequence:"}]},{"t":"ul","items":[[{"text":"A cut-out hole comes out "},{"text":"larger","b":true},{"text":" than drawn, by one kerf."}],[{"text":"A cut-out part comes out "},{"text":"smaller","b":true},{"text":" than drawn, by one kerf."}],[{"text":"So two parts drawn to slot together exactly will be loose by two kerfs: about 0.4 mm, which is a wobbly joint."}]]},{"t":"p","runs":[{"text":"Measure it rather than guessing. The standard test: cut a 20 mm square from a scrap of the actual material, measure the square and the hole with callipers, and the difference divided by two is your kerf."}]},{"t":"code","lang":"","label":"Text","text":"hole measured  20.22 mm\npart measured  19.78 mm\ndifference      0.44 mm  →  kerf 0.22 mm"},{"t":"p","runs":[{"text":"Then offset your paths by half a kerf in the appropriate direction for a press fit, or design the clearance in deliberately."}]},{"t":"h2","id":"closed-paths-always","runs":[{"text":"Closed paths, always"}]},{"t":"p","runs":[{"text":"A cut path must be "},{"text":"closed","b":true},{"text":". An open path leaves the piece attached by whatever gap remains, and it has to be snapped or cut free by hand, leaving a mark. This is the same discipline as the plotter: weld overlaps, close every loop, remove duplicates."}]},{"t":"p","runs":[{"text":"Duplicate paths matter more here than anywhere. Two identical paths stacked means the laser cuts the same line twice, which on thin material burns a wide, charred channel."}]},{"t":"h2","id":"material-safety-which-is-not-optional","runs":[{"text":"Material safety, which is not optional"}]},{"t":"p","runs":[{"text":"Never cut PVC, vinyl, or anything containing chlorine.","b":true},{"text":" Lasering PVC releases "},{"text":"hydrogen chloride gas","b":true},{"text":", which corrodes the machine’s optics and rails and is seriously harmful to breathe. Sign vinyl is PVC. This is the single most important fact in this lesson, and reputable shops refuse the material outright."}]},{"t":"p","runs":[{"text":"Also refuse or check carefully:"}]},{"t":"ul","items":[[{"text":"Polycarbonate","b":true},{"text":": burns rather than cutting, yellows the edge, smokes badly."}],[{"text":"ABS","b":true},{"text":": melts and produces cyanide compounds."}],[{"text":"Fibreglass and carbon fibre","b":true},{"text":": resin fumes and abrasive dust."}],[{"text":"Anything you cannot identify.","b":true},{"text":" If the client cannot say what a sheet is made of, do not put it in a laser."}]]},{"t":"p","runs":[{"text":"Safe and common: "},{"text":"plywood and MDF","b":true},{"text":" (both give a charred edge, which is a look), "},{"text":"acrylic / PMMA","b":true},{"text":" (cuts beautifully with a polished edge; cast acrylic engraves frosted white, extruded does not), "},{"text":"paper and card","b":true},{"text":", "},{"text":"leather","b":true},{"text":" (vegetable tanned, not chrome), "},{"text":"fabric","b":true},{"text":", "},{"text":"cork","b":true},{"text":", "},{"text":"anodised aluminium","b":true},{"text":" for marking."}]},{"t":"h2","id":"living-hinges-and-the-things-a-laser-makes-possible","runs":[{"text":"Living hinges and the things a laser makes possible"}]},{"t":"p","runs":[{"text":"A "},{"text":"living hinge","b":true},{"text":" is a pattern of interlaced slots cut into rigid sheet that makes it bend. The spacing, slot length and gap determine the bend radius, and it is worth cutting a test strip in the actual material rather than copying numbers."}]},{"t":"p","runs":[{"text":"Similarly, "},{"text":"inlay","b":true},{"text":" work, "},{"text":"stacked layers","b":true},{"text":", "},{"text":"engrave-then-cut","b":true},{"text":" sequences: all are just ordering operations correctly in the file and on the machine."}]},{"t":"h2","id":"the-software","runs":[{"text":"The software"}]},{"t":"ul","items":[[{"text":"LightBurn","b":true},{"text":" is what most small shops run. Paid, inexpensive, one-off licence, and good: layer-based, per-layer power and speed, kerf offset built in, and it drives most common controllers."}],[{"text":"Inkscape plus a CAM extension","b":true},{"text":" (Gcodetools, or the several laser plugins) is the free route and works, with more friction."}],[{"text":"The machine’s own driver","b":true},{"text":", often a printer driver where you “print” from any application, using colours for operations."}]]},{"t":"p","runs":[{"text":"Send SVG, DXF or PDF at 1:1 in millimetres, with layers named "},{"text":"CUT","code":true},{"text":", "},{"text":"SCORE","code":true},{"text":" and "},{"text":"ENGRAVE","code":true},{"text":", and put the material and thickness in the filename."}]}],"check":{"question":[{"text":"A designer draws two plywood parts to slot together, with a 6 mm tab and a 6 mm slot, and sends the file for laser cutting. The joint comes out loose. What is the arithmetic?"}],"options":[{"text":[{"text":"The tab cuts 6 mm minus one kerf and the slot 6 mm plus one, so the gap is two kerfs."}],"correct":true,"tempting":null},{"text":[{"text":"Plywood expands when heated by the beam, so both features come out oversized and the fit is lost."}],"correct":false,"tempting":[{"text":"Charring removes material rather than adding it, and any thermal expansion has reversed by the time the part is handled."}]},{"text":[{"text":"The kerf applies only to the outer cut, so the slot is correct and the tab is undersized by one kerf."}],"correct":false,"tempting":[{"text":"Kerf applies to every cut the beam makes, inside and outside. Both features are affected, in opposite directions."}]},{"text":[{"text":"The file was drawn in inches and then converted, introducing a rounding error of about 0.4 mm on a 6 mm feature."}],"correct":false,"tempting":[{"text":"A unit conversion error would scale everything, not just the joint, and 0.4 mm on 6 mm is far larger than any rounding in a conversion."}]}],"order":[3,1,2,0],"why":null},"prev":{"slug":"embroidery-digitising","title":"Embroidery, which does not use vectors at all","minutes":9},"next":{"slug":"cnc-and-built-up-letters","title":"CNC routing, tool radius, and the letters on a shop board","minutes":8}}}