A spring lock washer is a small metal ring with a gap. Unlike flat washers, this one is twisted into a spiral shape, like a slice of a spring. It’s designed to stay slightly compressed, which helps hold bolts and nuts in place — even when things vibrate. This version shows how to model that twist using a helical sweep.

// Split Washer (Spring Version)
// A spring lock washer is a small metal ring with a gap. Unlike flat washers, this one is twisted into a spiral shape, like a slice of a spring. It’s designed to stay slightly compressed, which helps hold bolts and nuts in place — even when things vibrate. This version shows how to model that twist using a helical sweep.
// Categories: Fasteners

@settings(defaultLengthUnit = mm)

// ──────────
// PARAMETERS
// ──────────

// Inner hole diameter — matches the bolt shaft
washerHoleDiameter = 4
washerHoleRadius = washerHoleDiameter / 2

// Outer diameter of the washer — must be bigger than the hole
washerOuterDiameter = 8
washerOuterRadius = washerOuterDiameter / 2

// Thickness of the washer — this defines how tall the cross-section is
washerThickness = 1

// Vertical rise from one end of the washer to the other — defines the “spring” effect
washerSplitHeight = 1

// ──────────────────────────────
// STEP 1: DEFINE THE HELIX GUIDE
// ──────────────────────────────


// To make a 3D spring-like shape, we need a *path* for the geometry to follow. We'll use a helix (like a spiral staircase) as this path. The sweep will twist the washer’s cross-section along the helix, giving it the spring form.


// The helix:
// - Starts at the origin
// - Wraps in a counter-clockwise direction (ccw = true)
// - Has a radius equal to the bolt hole (so it wraps around the center)
// - Rises by `washerSplitHeight` over the revolution
// - We set revolutions to 0.95 (just under one full circle) to leave a realistic gap
// If we set it to exactly 1.0, the washer would be fully closed.


helixGuide = helix(
  axis = Z,
  radius = washerHoleRadius,
  length = washerSplitHeight,
  revolutions = 0.95,
  angleStart = 0,
  ccw = true,
)

// ───────────────────────────────────────
// STEP 2: DRAW THE WASHER’S CROSS SECTION
// ───────────────────────────────────────

// Next, we draw the shape that will be swept along the helix. This is a small rectangle that defines one slice of the washer’s ring.
// - The height of this rectangle is the washer’s thickness.
// - Its width is the difference between the outer and inner radius — the actual width of the ring material.
washerSectionWidth = washerOuterRadius - washerHoleRadius

// The sweep profile needs to sit on the XZ plane, because the helix starts at Y = 0.
washerSectionSketch = startSketchOn(XZ)

// We position the start of the rectangle at the washerHoleRadius, so it aligns with the helix guide.


washerSectionProfile = startProfile(washerSectionSketch, at = [washerHoleRadius, 0])
  |> yLine(length = washerThickness) // Go up to define thickness
  |> xLine(length = washerSectionWidth) // Go outward toward the outer radius
  |> yLine(length = -washerThickness) // Go back down to complete the rectangle
  |> line(endAbsolute = [profileStartX(%), profileStartY(%)])
  |> close()

// ──────────────────────────────
// STEP 3: SWEEP TO FORM THE BODY
// ──────────────────────────────


// Now that we have a path (helix) and a shape (rectangle), we sweep the shape along the helix.
// This creates a ring that’s slightly twisted — like a slice of a spring.
// The result is a true spring lock washer in 3D.


splitWasherBody = sweep(washerSectionProfile, path = helixGuide)


Split Washer (Spring Version)

Zookeeper

Zookeeper: The Conversational CAD Agent For Parametric Modeling

Automation

Automating Your Workflow

File Formats

A Practical Overview of CAD File Formats

KCL: A Programming Language for Parametric CAD

Geometry Engine

Zoo CAD Engine Overview