# From a sentence to a printable part: how Meshra builds real CAD What actually happens between typing a prompt and downloading a STEP file: parametric code generation, a real geometry kernel, and sliders for every dimension. --- Most AI 3D generators give you a mesh: a shell of triangles that looks right in a render and falls apart the moment you need to change a dimension, cut a thread, or send it to a machine shop. Meshra takes a different route. When you type "a wall bracket for a 30 mm pipe with two M5 mounting holes", you get real parametric CAD: exact geometry, editable dimensions, and manufacturing files that CNC and print workflows accept without repair. This post walks through what actually happens between the sentence and the download. ## Step 1: your sentence becomes engineering code Meshra does not ask a model to imagine a shape. It asks a model to write a small engineering program: CadQuery code, a Python dialect used to script the same OpenCascade geometry kernel that powers professional CAD packages. Your bracket is not a picture of a bracket; it is a sequence of operations. Sketch a profile, extrude it 12 mm, bore two 5.2 mm holes at a 40 mm spacing, fillet the corners. Alongside the code, Meshra extracts a parameter manifest: every meaningful dimension in the design (pipe diameter, wall thickness, hole spacing) becomes a named, typed value with sensible limits. ## Step 2: a real geometry kernel builds it The code runs in a sandboxed geometry engine. This is the honesty checkpoint most AI tools skip: either the kernel can construct your solid, or it cannot. There is no "close enough". If an operation fails (a fillet larger than the wall it rounds, a hole that exits through a curved face), Meshra's self-healing pass corrects the usual failure modes deterministically and rebuilds. What comes out is a boundary representation solid: mathematically exact faces and edges, not triangles. That distinction is why the STEP file opens cleanly in Fusion 360, SolidWorks, or FreeCAD. ## Step 3: every dimension becomes a slider Because the part is a program with parameters, changing it does not mean regenerating from scratch. The parameter drawer in the builder shows a slider for each value in the manifest. Drag the pipe diameter from 30 mm to 32 mm and the same code re-executes with the new value: holes stay aligned, walls keep their thickness, and nothing melts or distorts the way mesh editing does. Parameter changes are deterministic re-execution, not new AI calls, so they are fast and free on every plan. ## Step 4: export files a machine can use When the part is right, you export: - **STEP** for CAD interchange and CNC quoting: exact geometry, the format machine shops ask for. - **STL** for slicers and 3D printing. - **GLB** for web previews and AR. You can also grab all formats in one ZIP, plus a parts list for multi-piece assemblies. ## Why this matters The gap between "looks like a bracket" and "is a bracket" is exact dimensions, editability, and file formats that downstream tools trust. Parametric CAD has always offered that; it just demanded years of CAD skills first. Writing one clear sentence is the whole learning curve now. If you have a part in mind, the fastest way to understand Meshra is to describe it and drag the sliders yourself.