Helix

helix() creates a helical wire — the curve that springs, threads, and coils are built from. On its own it renders as a wire; pair it with sweep() to turn it into a solid.

import { helix } from 'fluidcad/core';

helix("z").radius(15).pitch(10).turns(4);

The argument is the axis to coil around — a named axis like "z", anything axis-like, or an existing scene object (see deriving from geometry below).

Sizing

Three chained methods control the proportions, and any two determine the third:

helix("z").pitch(10).turns(4)       // height = 40
helix("z").pitch(10).height(40)     // turns = 4
helix("z").turns(4).height(40)      // pitch = 10

• .pitch(p) — axial rise per full revolution.
• .turns(n) — number of revolutions; fractional values are fine.
• .height(h) — total axial extent.

Unset values fall back to sensible defaults: turns defaults to 1, radius to 20, and height to 50 (or pitch × turns when a pitch is given).

Springs

Sweep a small profile along the helix to get a spring. The profile is positioned at the path start automatically:

import { sketch, circle, hMove, helix, sweep } from 'fluidcad/core';

const path = helix("z").radius(15).pitch(10).turns(5);

const profile = sketch("left", () => {
    hMove(15);
    circle(2);
});

sweep(path, profile);

Deriving from geometry

Instead of an axis, pass a scene object and the helix takes its frame from the geometry:

• Cylindrical face — axis, radius, and height come from the face.
• Conical face — the helix follows the cone's taper; radii are derived from the face geometry (.radius()/.endRadius() are ignored).
• Line edge — the line becomes the axis, its length the height.
• Circular edge — the circle's normal becomes the axis, its radius the helix radius.

import { cylinder, select, helix } from 'fluidcad/core';
import { face } from 'fluidcad/filters';

cylinder(15, 60);

helix(select(face().cylinder())).turns(6);

Use select(...) to narrow a body down to the single face or edge the helix should read from.

Threads and grooves

A helix at the surface of a cylinder is the spine of a thread. Sweep a profile along it and the result fuses with the cylinder (the default for boolean operations):

import { cylinder, sketch, move, circle, helix, sweep } from 'fluidcad/core';

cylinder(15, 50);

const path = helix("z").height(50).radius(15).pitch(5)
    .startOffset(-5).endOffset(5);

const profile = sketch("left", () => {
    move([15, 0]);
    circle(3);
});

sweep(path, profile);

Chain .remove() on the sweep to carve a groove instead:

import { cylinder, sketch, move, circle, helix, sweep } from 'fluidcad/core';

cylinder(15, 50);

const path = helix("z").height(50).radius(15).pitch(5)
    .startOffset(-5).endOffset(5);

const profile = sketch("left", () => {
    move([15, 0]);
    circle(3);
});

sweep(path, profile).remove();

Running past the ends

Real threads run off the ends of the stock rather than stopping flush. .startOffset() and .endOffset() shift the helix ends along the axis, in axial mm:

helix("z").height(50).startOffset(-5).endOffset(5)   // 5mm overshoot each side

A negative start offset extends the start; a positive end offset extends the end (and vice versa to trim). On a conical face the extension follows the cone's natural taper.

Tapered helixes

When .endRadius() differs from .radius(), the radius blends linearly along the height — a conical helix:

import { sketch, circle, hMove, helix, sweep } from 'fluidcad/core';

const path = helix("z").height(60).pitch(10).radius(25).endRadius(10);

const profile = sketch("left", () => {
    hMove(25);
    circle(2);
});

sweep(path, profile);

The same shape falls out automatically when the source is a conical face. .endRadius() is ignored for face and circular-edge sources, where the radii come from the geometry.

Limitations

• Turns must be positive and the pitch non-zero; a tapered helix must keep its end radius above zero.
• A face source must be cylindrical or conical; an edge source must be a line or a circle. Multi-shape sources need a select(...) to single out one face or edge.