# Unable to Calibrate X-Y Axis **URL:** \ **Category:** LightBurn Software Questions\ **Created:** [March 31, 2024, 6:52pm UTC](https://forum.lightburnsoftware.com/t/unable-to-calibrate-x-y-axis/135032 "2024-03-31T18:52:37Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![dalek](https://forum.lightburnsoftware.com/letter_avatar_proxy/v4/letter/d/e5b9ba/32.png) [@dalek](https://forum.lightburnsoftware.com/u/dalek)\ **Post date:** [March 31, 2024, 6:52pm UTC](https://forum.lightburnsoftware.com/t/unable-to-calibrate-x-y-axis/135032/1 "2024-03-31T18:52:37Z")
I’m not sure if this is software or hardware. I usually work small dimensional projects. Recently, I downloaded a larger project (120 X 345 X 226mm) from Etsy. the designer was very precise in his joinery and it was impossible to get the continuous slots and tabs to line up. The actual “box” parts ended up about 2mm oversized. I called Omtech tech support who walked me through Lightburn calibrate axis in machine settings. I thought we had it with a 25mm cutout. I still had problems and tried recalibrating a 75 X 100mm rectangle. First a little under, recalibrate then a little larger, recalibrate a little smaller and so on. What kind of precision should I expect? Over these distances, I’m about 0.5 to 0.7mm off. What else could be going on? Thanks! Dale ---
**Author:** ![ednisley](https://forum.lightburnsoftware.com/user_avatar/forum.lightburnsoftware.com/ednisley/32/40455_2.png) [@ednisley](https://forum.lightburnsoftware.com/u/ednisley)\ **Post date:** [March 31, 2024, 10:37pm UTC](https://forum.lightburnsoftware.com/t/unable-to-calibrate-x-y-axis/135032/2 "2024-03-31T22:37:29Z")
> [@dalek](#): > > we had it with a 25mm cutout The reason you can’t use a cutout is the measurement doesn’t include the vaporized kerf: the hole will be larger and the cut out shape will be smaller than the nominal size. Adjustments that make any given size accurate will make all other sizes inaccurate, because they do not take the kerf into account. Instead, engrave a square with a fine line on something cheap & flat, then measure center-to-center between the lines. This assumes you can make accurate measurements on, say, cardboard, which can be challenging. Instead, I use the red-dot pointer on a good metal scale: > **[OMTech 60 W Laser: Axis Scale Check](https://softsolder.com/2022/06/14/omtech-60-w-laser-axis-scale-check/)** > > Neither of those changes was large enough to affect the outcome When you’re done, the laser _should_ be pretty much dead on across the entire platform. When you care about the actual dimensions of the parts, you must apply a [kerf offset](https://docs.lightburnsoftware.com/UI/CutSettings/CutSettings-Line.html#kerf-offset) to lay the edge of the cut at the nominal outline position. All that assumes the machine is in good mechanical condition with no appreciable backlash. If that’s not the case, then fix the machinery before trying to calibrate it. ---
**Author:** ![dalek](https://forum.lightburnsoftware.com/letter_avatar_proxy/v4/letter/d/e5b9ba/32.png) [@dalek](https://forum.lightburnsoftware.com/u/dalek)\ **Post date:** [April 1, 2024, 12:42pm UTC](https://forum.lightburnsoftware.com/t/unable-to-calibrate-x-y-axis/135032/3 "2024-04-01T12:42:08Z")
Makes sense! I have a Starrett digital caliper from my furniture building past. Actually, 0.5mm differential on a 100mm test works out to about 1.5mm on a 350mm project piece; that makes a huge difference! I assume you are referring to the “Offset Tool”. So the offset would be inside the cut line? Also, I need to know the size of the laser beam, correct? Do I then delete the original project line and cut the offset line? Thanks! Dale Thanks guys! ---
**Author:** ![dalek](https://forum.lightburnsoftware.com/letter_avatar_proxy/v4/letter/d/e5b9ba/32.png) [@dalek](https://forum.lightburnsoftware.com/u/dalek)\ **Post date:** [April 1, 2024, 12:54pm UTC](https://forum.lightburnsoftware.com/t/unable-to-calibrate-x-y-axis/135032/4 "2024-04-01T12:54:01Z")
Ed, Now you have me thinking. Offset in or out? Here’s a screenshot of a portion of the project. Dale ![Screenshot 2024-04-01 084958](https://forum.lightburnsoftware.com/uploads/default/original/3X/9/a/9ac1b3489be4a310207ded65340ea79bc6e650ca.png) ---
**Author:** ![ednisley](https://forum.lightburnsoftware.com/user_avatar/forum.lightburnsoftware.com/ednisley/32/40455_2.png) [@ednisley](https://forum.lightburnsoftware.com/u/ednisley)\ **Post date:** [April 1, 2024, 2:12pm UTC](https://forum.lightburnsoftware.com/t/unable-to-calibrate-x-y-axis/135032/5 "2024-04-01T14:12:06Z")
> [@dalek](#): > > 0.5mm differential on a 100mm test works out to about 1.5mm on a 350mm project piece A little error grows when it’s proportional to the size! > [@dalek](#): > > referring to the “Offset Tool”. [That will work](https://docs.lightburnsoftware.com/Tools/ModifierTools.html#offset), but you can also apply an [offset to the entire layer](https://docs.lightburnsoftware.com/UI/CutSettings/CutSettings-Line.html#kerf-offset). Negative values are “inward” and positive values are “outward” relative to the nominal perimeter. The gotcha: layer offsets apply to _closed_ shapes and can have peculiar interactions with complex patterns. You may not want to apply an offset to everything in the layer, which means you must move those shapes to a different layer. With that in mind, I apply offsets to specific shapes needing a precise fit, so I can verify what’s about to happen. > [@dalek](#): > > know the size of the laser beam The kerf width depends critically on the material, speed, power, and perhaps the moon phase. A handy pattern / tool to measure the actual kerf in whatever you’re cutting will come in handy: > [@Kerf Offset test: with built-in vernier scale for accuracy, no tools required!](https://forum.lightburnsoftware.com/t/kerf-offset-test-with-built-in-vernier-scale-for-accuracy-no-tools-required/98333): > > There has been a bit of a flurry of marquetry lately on the forum, and it prompted me to make a tool to help calculate kerf offset accurately and easily, while using minimal material: I was inspired by @jkwilborn’s [tool](https://forum.lightburnsoftware.com/t/marks-bumps-from-laser-refracting-off-honeycomb-laser-bed-is-that-a-thing/58558/4), but I added a [vernier scale](https://en.wikipedia.org/wiki/Vernier_scale) to make it easier to measure, without needing calipers! Just cut it, slide it, and calculate your kerf. Here’s the file: [Kerf Test with Vernier Scale.lbrn2](https://forum.lightburnsoftware.com/uploads/short-url/sgSzZNLnuzCgfSmvnT5XXs5SOFj.lbrn2) (2.4 MB) I’d love any feedbac… Think thrice, measure twice, cut once! ---
**Author:** ![dalek](https://forum.lightburnsoftware.com/letter_avatar_proxy/v4/letter/d/e5b9ba/32.png) [@dalek](https://forum.lightburnsoftware.com/u/dalek)\ **Post date:** [April 1, 2024, 3:10pm UTC](https://forum.lightburnsoftware.com/t/unable-to-calibrate-x-y-axis/135032/6 "2024-04-01T15:10:35Z")
Than you Ed but I’m trying to puzzle out whether it’s inside our outside in this specific case. ---
**Author:** ![ednisley](https://forum.lightburnsoftware.com/user_avatar/forum.lightburnsoftware.com/ednisley/32/40455_2.png) [@ednisley](https://forum.lightburnsoftware.com/u/ednisley)\ **Post date:** [April 1, 2024, 4:52pm UTC](https://forum.lightburnsoftware.com/t/unable-to-calibrate-x-y-axis/135032/7 "2024-04-01T16:52:38Z")
> [@dalek](#): > > puzzle out whether it’s inside our outside in this specific case. For the black lines, all the fingers around the perimeter must have the nominal size in order to fit together. That requires an _outward_ offset: the beam runs _outside_ the nominal perimeter, cutting exactly on the line. An _inward_ offset would put the beam on the _inside_ of the perimeter, so the material surrounding the part has the proper dimensions. Probably not what you want. The red stuff in the middle is up for grabs. If the rectangular outlines in the upper piece are sockets for more tabs, then they also need _outward_ offsets to put their borders at the nominal size. If you think of the laser spot as a (tiny) round cutting tool, you won’t go too far wrong. LightBurn counts boundary crossings on a per-layer basis to automagically apply layer offsets, so all the perimeters move in the same way relative to the part’s interior. This may be what you want, but it’s worthwhile to run a few tests even when you think you know what’s about to happen. Some projects aren’t that _ahem_ clearcut, in which case you must puzzle it out on your own. 😁 ---
**Author:** ![dalek](https://forum.lightburnsoftware.com/letter_avatar_proxy/v4/letter/d/e5b9ba/32.png) [@dalek](https://forum.lightburnsoftware.com/u/dalek)\ **Post date:** [April 1, 2024, 4:59pm UTC](https://forum.lightburnsoftware.com/t/unable-to-calibrate-x-y-axis/135032/8 "2024-04-01T16:59:05Z")
Thanks Ed, I made the kerf scale and top scale reds 5, bottom scale is 7. So, 5.7/20= .285mm. Sound right? ---
**Author:** ![ednisley](https://forum.lightburnsoftware.com/user_avatar/forum.lightburnsoftware.com/ednisley/32/40455_2.png) [@ednisley](https://forum.lightburnsoftware.com/u/ednisley)\ **Post date:** [April 1, 2024, 5:02pm UTC](https://forum.lightburnsoftware.com/t/unable-to-calibrate-x-y-axis/135032/9 "2024-04-01T17:02:04Z")
> [@dalek](#): > > Sound right? It’s in the right ballpark for a CO₂ laser cutting a wood-like substance: around 0.2 mm. May be a bit large, but that’s _exactly_ why measurements beat opinions: trust, but verify. Remember that the kerf offset is _half_ that value to shift the beam half the kerf width (in the proper direction!). ---
**Author:** ![dalek](https://forum.lightburnsoftware.com/letter_avatar_proxy/v4/letter/d/e5b9ba/32.png) [@dalek](https://forum.lightburnsoftware.com/u/dalek)\ **Post date:** [April 6, 2024, 2:36pm UTC](https://forum.lightburnsoftware.com/t/unable-to-calibrate-x-y-axis/135032/10 "2024-04-06T14:36:38Z")
I’m back. Please see attached screen shots. While I have not changed kerf offset settings, I’m concerned that increasing the offset may make the tabs the correct size, won’t the slots also change? Dale ![Fish](https://forum.lightburnsoftware.com/uploads/default/original/3X/9/0/9063c563d4515b6bbda9d9937ba7b042238864c5.png) ![Support Base](https://forum.lightburnsoftware.com/uploads/default/original/3X/7/f/7f051da6c3d1bcb82819bd519ae981e95d82a5d2.png) ---
**Author:** ![ednisley](https://forum.lightburnsoftware.com/user_avatar/forum.lightburnsoftware.com/ednisley/32/40455_2.png) [@ednisley](https://forum.lightburnsoftware.com/u/ednisley)\ **Post date:** [April 6, 2024, 4:16pm UTC](https://forum.lightburnsoftware.com/t/unable-to-calibrate-x-y-axis/135032/11 "2024-04-06T16:16:05Z")
> [@dalek](#): > > increasing the offset may make the tabs the correct size, won’t the slots also change? Everything is deeply intertwingled! **Caveat** : I don’t know how all those parts are supposed to fit together, nor whether the red crosses represent holes, so pay attention to catch my incorrect _assumptions_. I _assume_ all the lines in those layouts are on the nominal dimensions, so that an ideal zero-width Xacto-knife cut will fit everything together. If you apply the correct outward (positive) kerf offset to the (black?) layer with the fish outlines in the first screenshot, then their posts come out exactly at the nominal width. The notches (slots?) in the black round bases (?) also cut to the nominal size, so the tabs should fit into the slots. In both cases, the kerf offset moves the beam outward so the inner edge of the cut = outer boundary of the shape lies exactly along the nominal perimeter. If you apply the same outward offset to the (blue-ish? green-ish?) layer with the notches (slots?) in the second screenshot, they also come out at the nominal size to match the nominal size of the red crosses. However, if the crosses in the red layer in the first screenshot represent _holes_ inside the black bases, then applying an outward kerf offset to the _red_ layer will make the holes too large, because the beam will travel around the _outside_ of the cross: LightBurn does not know those are holes. If you apply an inward (negative) offset to the red layer, then the beam travels around the _inside_ of the cross so the surrounding material has the correct size after the cross drops out. Instead, you can put the crosses on the black layer, in which case LightBurn [knows they are holes](https://docs.lightburnsoftware.com/UI/CutSettings/CutSettings-Line.html#kerf-offset) by counting perimeter crossings from outside the layout into the closed shape: - Odd number of crossings = outside perimeter = object - Even number of crossings = inside perimeter = hole So, yes, applying a kerf to a layer means _everything_ changes: it’s your responsibility to know which way they’ll change. You should definitely practice on cheap material until you’re sure you understand what’s going on and, even then, expect a few surprises. ---
**Author:** ![cggorman](https://forum.lightburnsoftware.com/user_avatar/forum.lightburnsoftware.com/cggorman/32/75539_2.png) [@cggorman](https://forum.lightburnsoftware.com/u/cggorman)\ **Post date:** [April 6, 2024, 5:27pm UTC](https://forum.lightburnsoftware.com/t/unable-to-calibrate-x-y-axis/135032/12 "2024-04-06T17:27:28Z")
Preview DOES SHOW the kerf-adjusted output. If you want to see the relative directions of all the offsets, you can temporarily apply an exaggerated kerf offset value to make them visible. Kerf is typically a fraction of a millimeter, so it would be easy to simply add a digit to the left of the decimal. ---
**Author:** ![dalek](https://forum.lightburnsoftware.com/letter_avatar_proxy/v4/letter/d/e5b9ba/32.png) [@dalek](https://forum.lightburnsoftware.com/u/dalek)\ **Post date:** [April 6, 2024, 7:47pm UTC](https://forum.lightburnsoftware.com/t/unable-to-calibrate-x-y-axis/135032/13 "2024-04-06T19:47:11Z")
Thanks Ed! ---
**Author:** ![system](https://forum.lightburnsoftware.com/user_avatar/forum.lightburnsoftware.com/system/32/64335_2.png) [@system](https://forum.lightburnsoftware.com/u/system)\ **Post date:** [May 6, 2024, 7:47pm UTC](https://forum.lightburnsoftware.com/t/unable-to-calibrate-x-y-axis/135032/14 "2024-05-06T19:47:52Z")
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