Your model never leaves your device
Knurlsis has no upload and no server-side code. The page is a set of static files; once they have loaded, everything happens in your browser:
- reading the file (STL, 3MF, OBJ, and STEP through OpenCascade compiled to WebAssembly),
- finding the surfaces you can click,
- laying the chosen surface flat and drawing the grooves on it,
- cutting the grooves into the solid (Manifold, compiled to WebAssembly),
- writing the STL or 3MF file, which your browser saves straight to your disk.
Nobody receives a copy: not us, not a cloud service, not an analytics company.
How that is enforced, not just promised
- No server code. The site is static files served by Cloudflare. There is no endpoint that could accept a model.
- A strict Content-Security-Policy (
connect-src 'self'): your browser itself refuses to send data to any other website. - No analytics, no trackers, no cookies, no third-party scripts, fonts or images. Every library is served from this site.
- Check it yourself: open your browser's developer tools (F12, then the Network tab) while you use Knurlsis. You'll see the site's own files load, and nothing else.
Your browser keeps your last knurl settings and export format in its local storage, on your device only, so they're ready next time.
How the knurl is made
When you click a surface, Knurlsis works out which faces belong to it and lays them flat without stretching wherever the shape allows it: flat faces are used as they are, cylinders and the sides of rounded boxes are unrolled exactly, and bands that close on themselves get a pattern that wraps around with a whole number of diamonds, so there is no seam. Cones and other tapering knobs are mapped so the diamonds keep their shape and shrink with the radius.
The grooves are then real V-shaped cutters, swept over the surface and subtracted from your model, so the result is a clean, watertight solid that any slicer accepts. Each groove ends exactly on the edge-gap line, which keeps the border of the knurl crisp.
Knurlsis also checks the wall behind the grooves and warns you if a groove would break through, with a one-click shallower depth.
Free, really
There is no paid tier, no export limit and no account. Knurlsis is a free alternative to paid knurling services.
Credits
Built with three.js, three-mesh-bvh, Manifold, occt-import-js (licence) with Open CASCADE Technology (licence), fflate and the Barlow typeface by Jeremy Tribby.