wormgear 0.1.0a2

Worm gears for build123d, with DIN-3975 engineering analysis

Wormgear

Worm gears for build123d, with real DIN-3975 engineering behind the geometry.

from wormgear import WormGear, WormWheel

worm  = WormGear(module=2.0, num_starts=1, length=40)   # is a build123d Part
wheel = WormWheel(module=2.0, num_teeth=30)             # is a build123d Part

worm.export_step("worm.step")
wheel.export_step("wheel.step")

Or for a guaranteed-matched pair in one line:

from wormgear import make_pair

worm, wheel = make_pair(module=2.0, ratio=30, length=40)

That's the whole API for most users. Both classes subclass build123d.BasePartObject, so you can show(), export_step(), or compose them into assemblies directly.

Why use this over a generic gear library

Worm gears are the part of the gear ecosystem that nobody else implements properly. bd_warehouse.gear has spur and helical gears but no worm primitives. gggears is excellent for general gears but doesn't do worm threading.

Wormgear:

• Implements real DIN-3975 derivation. Lead angle, pitch diameter, addendum/dedendum, throat radius for globoid worms — all standards-compliant rather than approximate.
• Calculates load-capacity-relevant fields per DIN-3996 (efficiency estimate, self-locking detection, recommended materials).
• Generates exact geometry. No "good enough after manufacturing" approximations — the STEP file is exactly what your CNC will cut or your printer will print.
• Two tooth profiles: ZA (straight flanks, CNC-friendly), ZK (slightly convex, 3D-print-friendly).

Install

pip install wormgear

Requires Python 3.12+. build123d (and its OpenCascade backend) installs automatically.

Beyond the basics

Engineering analysis

from wormgear import make_pair, check_mesh

worm, wheel = make_pair(module=2.0, ratio=30, length=40)

# Kinematic mesh validation (independent of how the gears were built)
report = check_mesh(worm._params, wheel._params, worm._assembly_params)
print(f"ok: {report.ok}, ratio: {report.ratio}, "
      f"centre distance: {report.centre_distance_mm:.2f} mm")

For full DIN-3975 design analysis (efficiency, self-locking, undercut, etc.):

from wormgear.calculator import design_from_module, validate_design

design = design_from_module(module=2.0, ratio=30)
result = validate_design(design)
print(f"efficiency: {design.assembly.efficiency_percent:.1f}%, "
      f"self-locking: {design.assembly.self_locking}")
for msg in result.warnings:
    print(f"warning: {msg.message}")

Features (bores, keyways, set screws)

from wormgear import WormGear
from wormgear.core import BoreFeature, KeywayFeature

worm = WormGear(
    module=2.0, num_starts=1, length=40,
    bore=BoreFeature(diameter=8.0),
    keyway=KeywayFeature(),  # auto-sized DIN-6885 keyway
)

Web calculator

Don't want to write any code? wormgear.studio is the browser-based version of the calculator. It produces a JSON file you can load:

from wormgear import WormGear, WormWheel
from wormgear.io import load_design_json

design = load_design_json("my-design.json")
worm  = WormGear.from_design(design, length=40)
wheel = WormWheel.from_design(design)

CLI

For shell-driven workflows (CAM pipelines, batch generation):

wormgear-geometry design.json -o out/
wormgear-geometry design.json --profile ZK --globoid --worm-bore 8

See wormgear-geometry --help for the full set of options.

Related libraries

Wormgear is one library in a coherent build123d gear ecosystem:

• bd_warehouse — spur gears, helical gears, fasteners, bearings
• gggears — general gear library with rich profiles

Use them together: spur gears from bd_warehouse for parallel-shaft stages, wormgear for perpendicular reduction stages.

Documentation

• Architecture — system design
• Geometry — technical specification
• Engineering Context — DIN-3975/DIN-3996 background

Background

Created for custom worm gear design in luthier (violin making) applications, where standard gears don't fit unusual envelope constraints. Extended to support CNC machining and 3D printing for makers and engineers.

License

MIT

Author

Paul Fremantle (@pzfreo)