build123d Design

build123d is a modern Python CAD library using builder patterns for cleaner code.

Installation

pip install build123d

Basic Workflow

from build123d import *

# Create a box with a hole using context manager
with BuildPart() as part:
    Box(10, 10, 5)
    with Locations((0, 0, 5)):
        Hole(radius=1, depth=5)

# Export
part.part.export_step("part.step")
part.part.export_stl("part.stl")

Builder Types

BuildPart - 3D Solid Modeling

with BuildPart() as result:
    Box(20, 20, 10)
    with Locations((5, 5, 10)):
        Cylinder(radius=3, height=5)

BuildSketch - 2D Sketching

with BuildSketch() as sketch:
    Rectangle(20, 10)
    with Locations((5, 0)):
        Circle(radius=2, mode=Mode.SUBTRACT)

BuildLine - Wire/Path Creation

with BuildLine() as path:
    Line((0, 0), (10, 0))
    Line((10, 0), (10, 10))
    Line((10, 10), (0, 0))

Common Operations

Extrusions and Cuts

with BuildPart() as part:
    with BuildSketch():
        Rectangle(20, 20)
    extrude(amount=10)

    with BuildSketch(part.faces().sort_by(Axis.Z)[-1]):
        Circle(radius=5)
    extrude(amount=-5, mode=Mode.SUBTRACT)

Fillets and Chamfers

with BuildPart() as part:
    Box(10, 10, 10)
    fillet(part.edges().filter_by(Axis.Z), radius=1)
    chamfer(part.edges().sort_by(Axis.Z)[-4:], length=0.5)

Assemblies

from build123d import *

base = Box(50, 50, 10)
pin = Cylinder(radius=5, height=20)

# Position parts
pin_located = Pos(10, 10, 10) * pin

# Combine
assembly = Compound([base, pin_located])
assembly.export_step("assembly.step")

Face and Edge Selection

# Get top face
top_face = part.faces().sort_by(Axis.Z)[-1]

# Get vertical edges
vertical_edges = part.edges().filter_by(Axis.Z)

# Get edges on face
face_edges = top_face.edges()