OpenSCAD Skill

Generate OpenSCAD (.scad) files for parametric 3D modeling. OpenSCAD is a functional programming language for creating solid 3D CAD objects using CSG (Constructive Solid Geometry).

Core Concepts

OpenSCAD scripts describe geometry through:

1. Primitives - Basic 2D/3D shapes (cube, sphere, cylinder, circle, square, polygon)
2. Transformations - Position/modify objects (translate, rotate, scale, mirror, color)
3. Boolean Operations - Combine shapes (union, difference, intersection)
4. Modules - Reusable parametric components
5. Extrusion - Convert 2D to 3D (linear_extrude, rotate_extrude)

Workflow

1. Define parameters as variables at the top for easy customization
2. Create modules for reusable components
3. Build geometry using primitives and boolean operations
4. Use comments to explain complex sections
5. Set $fn for curved surface resolution (higher = smoother but slower)

Quick Reference

3D Primitives

cube([x, y, z], center=false);
cube(size, center=false);
sphere(r=radius);  // or d=diameter
cylinder(h=height, r=radius, center=false);
cylinder(h=height, r1=bottom_r, r2=top_r);  // cone
polyhedron(points=[[x,y,z],...], faces=[[p0,p1,p2],...]);

2D Primitives

square([x, y], center=false);
circle(r=radius);  // or d=diameter
polygon(points=[[x,y],...]);
text("string", size=10, font="Liberation Sans");

Transformations

translate([x, y, z]) object();
rotate([x_deg, y_deg, z_deg]) object();
rotate(a=degrees, v=[x,y,z]) object();  // rotate around axis
scale([x, y, z]) object();
mirror([x, y, z]) object();  // mirror across plane
color("red") object();
color([r, g, b, a]) object();  // 0-1 values

Boolean Operations

union() { obj1(); obj2(); }         // combine (implicit if no operator)
difference() { base(); cut1(); }    // subtract from first child
intersection() { obj1(); obj2(); }  // keep only overlap

Extrusion (2D to 3D)

linear_extrude(height=h, twist=deg, scale=s, slices=n, center=false)
    2d_shape();
rotate_extrude(angle=360, $fn=n)
    2d_shape();  // shape must be on positive X side

Control Structures

// Loops
for (i = [0:10]) translate([i*5, 0, 0]) cube(3);
for (i = [0:2:10]) ...;  // start:step:end
for (pos = [[0,0], [10,5], [5,10]]) translate(pos) sphere(2);

// Conditionals
if (condition) { ... } else { ... }
variable = condition ? value_if_true : value_if_false;

Modules and Functions

// Module (creates geometry)
module my_part(size=10, holes=true) {
    difference() {
        cube(size);
        if (holes) cylinder(h=size+1, r=size/4, center=true);
    }
}
my_part(20, holes=false);

// Function (returns value)
function circumference(r) = 2 * PI * r;

Special Variables

$fn = 100;  // fragments for full circle (overrides $fa/$fs)
$fa = 12;   // minimum angle per fragment
$fs = 2;    // minimum size per fragment
$preview    // true during F5 preview, false during F6 render

Best Practices

Parametric Design

// Define all dimensions as variables
wall_thickness = 2;
inner_diameter = 20;
height = 30;

// Derive other values
outer_diameter = inner_diameter + 2*wall_thickness;

Avoiding Rendering Issues

// Use epsilon to prevent z-fighting in boolean operations
eps = 0.01;
difference() {
    cube([10, 10, 10]);
    translate([2, 2, -eps])
        cylinder(h=10 + 2*eps, r=3);  // slightly taller than parent
}

Manifold Geometry for 3D Printing

• Ensure all geometry is watertight (no gaps)
• Holes must fully penetrate surfaces
• Use render() to verify complex geometry
• Check face orientation with F12 (Thrown Together view)

Detailed References

• For complete syntax: See references/language_reference.md
• For example patterns: See references/examples.md

Output

Save generated code as .scad files. Users can open in OpenSCAD for:

• F5: Quick preview
• F6: Full render (required before export)
• Export to STL/AMF/3MF for 3D printing