CAD and Text-to-CAD Glossary
Source-backed definitions of CAD, text-to-CAD, file format, and manufacturing terms, from B-Rep and STEP to K-factor, GD&T, and MCP.
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A
AI & text-to-CAD
AI copilot
An AI copilot is an assistant built into CAD software that answers questions, suggests commands or best practices, and sometimes runs small tasks from a chat panel. Copilots help with the workflow around a model, and most do not generate a finished part from scratch.
AI & text-to-CAD
AI-native CAD
AI-native CAD describes CAD software designed with AI as a core part of how geometry is created and edited, rather than an assistant added to an existing product. It is a marketing term without a standard definition, so claims should be judged by what the software actually does.
Geometry & modeling
Assembly
An assembly is a CAD model made of multiple parts or subassemblies positioned relative to each other with mates or joints. Assemblies are where fit, clearance, interference, and motion get checked.
B
Geometry & modeling
B-Rep
Boundary representation
B-Rep is the way professional CAD kernels describe a solid: by its boundary, made of exact surfaces (faces), the curves where they meet (edges), and the points where edges end (vertices). Because the geometry is exact and the topology is explicit, B-Rep models can be measured, filleted, dimensioned, and manufactured precisely.
Manufacturing & engineering
Bend allowance
Bend allowance is the length of material used up by a sheet metal bend, measured along the neutral axis between the bend's tangent points. It depends on thickness, bend radius, bend angle, and K-factor, and it decides whether the flat blank folds up to the right size.
C
Geometry & modeling
CAD kernel
A CAD kernel is the geometry engine inside a CAD program that creates and modifies solids: booleans, fillets, shells, intersections, and tessellation for display. Parasolid and Open CASCADE are common examples, and the kernel largely decides which operations are reliable and how exports behave.
AI & text-to-CAD
CadQuery
CadQuery is an open-source Python library for building parametric CAD models in code on top of the Open CASCADE kernel. It can export STEP as well as STL and 3MF, which makes it a common target when LLMs are asked to write CAD scripts.
Manufacturing & engineering
CAM
Computer-aided manufacturing
CAM is software that turns CAD geometry into toolpaths and machine instructions, such as G-code for a CNC mill or lathe. It needs clean solid geometry, and it is where problems like unreachable corners and missing tool clearance show up.
Geometry & modeling
CSG
Constructive solid geometry
CSG builds a shape by combining simple solids, such as cubes, cylinders, and spheres, with boolean union, difference, and intersection. OpenSCAD models are written this way, which makes them easy for people and language models to express as code.
D
AI & text-to-CAD
DeepCAD dataset
The DeepCAD dataset is a public research dataset of 178,238 CAD models stored as sketch-and-extrude construction sequences, released with the ICCV 2021 DeepCAD paper. Much text-to-CAD research trains and benchmarks on it, and its simple geometry limits what those models learn.
Geometry & modeling
Design intent
Design intent is the reasoning built into a model's structure: which dimensions drive others, what stays centered or symmetric, and what should move when something changes. Two models that look identical can behave very differently when edited because of how their intent was captured.
Manufacturing & engineering
DFM
Design for manufacturing
DFM is the practice of shaping a part so it can be made reliably and economically with the intended process. It covers choices such as wall thickness, draft, tool access, bend radii, hole sizes, and tolerances the supplier can actually hold.
Geometry & modeling
Direct modeling
Direct modeling edits geometry by pushing, pulling, moving, and deleting faces directly, without replaying a feature history. It is fast for imported files and late changes, but it does not record why the model has its shape.
Manufacturing & engineering
Draft angle
A draft angle is a slight taper on faces parallel to the mold's pull direction, so a molded or cast part can release from the tool. Missing draft is one of the most common reasons a plastic part design is sent back by a molder.
Manufacturing & engineering
Drawing
An engineering drawing is a 2D document generated from a 3D model, with views, dimensions, tolerances, and notes. Many shops still quote and inspect from drawings even when they also receive a STEP file.
File formats
DXF
Drawing Exchange Format
DXF is Autodesk's documented format for exchanging AutoCAD drawing data, most often 2D geometry. It is the usual handoff for laser cutting, waterjet, and sheet metal flat patterns.
F
Manufacturing & engineering
FEA
Finite element analysis
FEA predicts how a part behaves under loads, heat, or vibration by dividing it into small elements and solving the physics for each one with the finite element method. It is also the engine behind topology optimization and most generative design tools.
Geometry & modeling
Feature tree
A feature tree is the ordered list of operations, such as sketches, extrudes, cuts, fillets, and patterns, that builds a parametric CAD model. Editing an early feature replays every feature after it, which makes controlled changes possible and also makes the model depend on each earlier step.
Manufacturing & engineering
Flat pattern
A flat pattern is the unfolded 2D shape of a sheet metal part, calculated from its bends, radii, and K-factor or bend table. It is what gets cut from the sheet before the part is formed.
G
Manufacturing & engineering
GD&T
Geometric dimensioning and tolerancing
GD&T is a symbolic language for specifying the allowed variation in a part's form, orientation, location, and runout relative to datum features. In the US it is defined by ASME Y14.5, and it tells the manufacturer and inspector which geometry actually matters for fit and function.
AI & text-to-CAD
Generative design
Generative design is software that produces many design options from goals and constraints, such as loads, keep-out regions, materials, and manufacturing methods. It optimizes toward performance targets rather than following a text description of a shape.
Geometry & modeling
Geometric constraint solver
A geometric constraint solver calculates the positions and dimensions of sketch geometry so declared relationships, such as parallel, perpendicular, tangent, equal, coincident, and fixed dimensions, are satisfied together. It lets a designer define intent instead of calculating every coordinate by hand.
File formats
glTF
GL Transmission Format
glTF is a Khronos Group format for delivering 3D scenes and models efficiently to web and real-time applications. It stores meshes with materials, textures, and animation, which makes it good for viewers and previews but not for engineering edits.
I
K
Manufacturing & engineering
K-factor
The K-factor is the ratio of the neutral axis position to the material thickness in a sheet metal bend. CAD programs use it to calculate bend allowance and the size of the flat pattern.
AI & text-to-CAD
KCL
KCL is Zoo's text-based programming language for parametric CAD. It is the source representation behind Zoo Design Studio models, so point-and-click actions and Zookeeper prompts can produce code that people can read, edit, reuse, and track with version control.
L
M
Geometry & modeling
Manifold
A manifold mesh is one where every edge is shared by exactly two triangles, so the surface clearly separates inside from outside. Slicers, mesh booleans, and CAD imports rely on manifold geometry to behave predictably.
Manufacturing & engineering
MBD
Model-based definition
MBD is the practice of making the annotated 3D model, with its PMI, the authoritative definition of a part instead of a separate 2D drawing. The model carries dimensions, tolerances, and notes directly to manufacturing and inspection.
AI & text-to-CAD
MCP
Model Context Protocol
MCP is an open-source protocol for connecting AI applications to external tools, data, and workflows. In CAD it is used to let an LLM call a CAD program such as OpenSCAD, FreeCAD, or Fusion, run modeling commands, and read back results instead of generating geometry blind.
Geometry & modeling
Mesh
A mesh represents a shape as a surface of small flat polygons, almost always triangles, joined at shared edges and vertices. Meshes work well for rendering, games, and 3D printing, but they have no true faces, edges, or exact curves, so they are hard to dimension or edit as engineering geometry.
N
AI & text-to-CAD
Neural CAD
Neural CAD refers to approaches where neural networks generate CAD modeling operations or editable CAD geometry, rather than meshes or images. Autodesk also uses the name for its work toward turning natural-language prompts into editable design geometry in Fusion.
Geometry & modeling
NURBS
Non-uniform rational B-splines
NURBS are mathematical curves and surfaces that can represent both simple shapes, such as lines, arcs, and circles, and complex freeform surfaces exactly. CAD kernels use them for the faces and edges of B-Rep solids that are not simple planes or cylinders.
O
File formats
OBJ
Wavefront OBJ
OBJ is a widely supported 3D geometry format that originated with Wavefront's Advanced Visualizer. In practice it is used to exchange polygon meshes with texture coordinates and materials, not engineering geometry.
AI & text-to-CAD
OpenSCAD
OpenSCAD is free, open-source CAD software where models are written as code using constructive solid geometry and extrusion of 2D outlines. Because the whole model is text, it is one of the easiest CAD targets for LLMs to generate and edit.
P
Geometry & modeling
Parametric modeling
Parametric modeling builds a CAD model from dimensions, constraints, and an ordered list of features, so changing a value regenerates the geometry. It is the default approach in SolidWorks, Fusion, Onshape, Creo, NX, and FreeCAD Part Design.
Manufacturing & engineering
PMI
Product and manufacturing information
PMI is the dimensions, tolerances, GD&T, materials, surface finishes, and notes attached to a 3D CAD model instead of, or in addition to, a 2D drawing. It is the core content of model-based definition.
S
Geometry & modeling
Sketch constraint
A sketch constraint is a rule applied to 2D sketch geometry, such as coincident, parallel, tangent, equal, or a fixed dimension. When a sketch is fully constrained, nothing in it can move freely, which makes later edits predictable.
File formats
STEP
Standard for the Exchange of Product Model Data
STEP is the ISO 10303 family of standards for exchanging 3D product data between CAD systems, usually saved as .step or .stp files. A STEP file carries exact B-Rep solid geometry that another CAD program can measure and edit, but it normally does not carry the original feature history.
File formats
STL
STL is a simple mesh file format that stores a surface as a list of triangles, each with a normal and three vertices. It is the long-standing default for 3D printing, but it has no units, colors, or exact geometry.
T
AI & text-to-CAD
Text-to-3D
Text-to-3D is AI that generates a 3D shape from a text prompt for visuals, games, or 3D printing, usually as a mesh or neural representation. It targets appearance rather than exact dimensions or editable CAD features.
AI & text-to-CAD
Text-to-CAD
Text-to-CAD is AI that turns a natural-language description into editable CAD geometry, such as a STEP file, a parametric model, or CAD code. The goal is a model with exact faces and dimensions that can be modified and manufactured, not just a shape that looks right on screen.
AI & text-to-CAD
Text2CAD
Text2CAD is a NeurIPS 2024 spotlight paper and dataset that generates parametric sketch-and-extrude CAD sequences from text prompts. It added about 660,000 text annotations, from beginner to expert level, to about 170,000 DeepCAD models.
Manufacturing & engineering
Tolerance
A tolerance is the allowed variation from a nominal dimension, such as 10.00 ± 0.05 mm. Tolerances drive fit, cost, and inspection, and they have to be specified deliberately because a CAD model on its own stores only nominal sizes.
Manufacturing & engineering
Topology optimization
Topology optimization is a simulation-driven method that removes material from a design space while meeting stiffness or strength targets under defined loads. The results are often organic shapes that need interpretation or rework before they can be manufactured.