CadQuery vs OpenSCAD: a programmatic CAD comparison for engineers

Why search for an OpenSCAD alternative?

OpenSCAD pioneered the idea of describing CAD parts in code instead of clicking through a GUI. For simple parametric shapes it's elegant: a few lines of cube(), cylinder() and difference() and you have a printable model. But once a part gets real — fillets on selected edges, draft angles, organic shelling, threaded features, sheet-metal flanges — the functional, CSG-only language starts to push back. Selecting "the four top edges of this pocket" becomes an exercise in remembering which CSG operation produced them.

That's why "openscad alternative" is a recurring query among mechanical engineers. CadQuery is the most popular answer.

CadQuery in one paragraph

CadQuery is a Python library on top of the OpenCascade kernel — the same B-Rep kernel that powers FreeCAD and Onshape. You write normal Python, chain modeling operations on workplanes, and select features by query strings like .faces(">Z").edges("|X"). Because it's Python, you get loops, functions, classes, numpy, unit tests, packaging — the entire ecosystem an engineering team already uses for analysis and scripting.

Side-by-side

A concrete example: a bracket with countersunk holes

In OpenSCAD, countersinks and edge fillets are CSG gymnastics:

difference() {
  cube([60, 40, 6]);
  for (x = [10, 50])
    for (y = [10, 30])
      translate([x, y, -0.1]) {
        cylinder(h=6.2, d=4.2, $fn=48);
        translate([0, 0, 4])
          cylinder(h=2.3, d1=4.2, d2=8.4, $fn=48);
      }
}

In CadQuery, the same part reads like a design intent:

import cadquery as cq

part = (
    cq.Workplane("XY")
    .box(60, 40, 6)
    .faces(">Z").workplane()
    .rect(40, 20, forConstruction=True)
    .vertices()
    .cskHole(diameter=4.2, cskDiameter=8.4, cskAngle=82)
    .edges("|Z").fillet(2)
)

Same physical part, half the lines, and every constraint is explicit: hole pattern, countersink geometry, fillet radius. You can unit-test that part.val().Volume() falls inside a tolerance band — a workflow that's hard to even express in OpenSCAD.

Where AeroCAD fits

CadQuery's only real downside vs OpenSCAD is the learning curve: workplane mental model, selector strings, and OpenCascade quirks. That's exactly what AeroCAD removes. You describe the part in English — dimensions, hole patterns, fillets, materials — and AeroCAD streams back a ready-to-execute CadQuery script. You keep the kernel quality and the Python ecosystem; you skip the API memorization.

For mechanical engineers evaluating an OpenSCAD alternative, that combination — CadQuery's B-Rep kernel plus AI-assisted scripting — is the productivity upgrade most teams are actually looking for.

Try it

Open AeroCAD, describe a part, and run the script locally with python part.py — from quick brackets to multi-feature assemblies.