OpenSCAD tutorial for beginners: build your first parametric part

OpenSCAD is free CAD software where you type a short script instead of drawing. You place shapes like cube() and cylinder(), combine them with union(), difference() and intersection(), and turn every dimension into a variable. This tutorial teaches that whole core by building a printable M3 L-bracket, and every example runs in your browser.

What is OpenSCAD and why use it for 3D printing?

OpenSCAD is a script-based CAD program. There's no feature tree and no sketch tool like in Fusion or Onshape. You write code that describes solids, and OpenSCAD compiles it into a mesh you can slice. It's free and open source (GPL v2 or later) and runs on Windows, macOS and Linux.

• Everything is parametric. Dimensions are variables, so changing one number regenerates the whole part.
• Everything is text. Models diff cleanly in git, fit in a forum post, and are easy for an AI to write and edit.
• The trade-off: no clicking on faces, no constraint solver, and organic shapes are hard. It shines for brackets, boxes, mounts, spacers and anything with numbers in its spec.

Set up: OpenSCAD in your browser or on your desktop

Pick one. The code is identical either way.

Your first OpenSCAD model: hello, cube

The smallest useful OpenSCAD program is one shape and a semicolon:

cube([30, 20, 10]);

That's a box 30 mm along X, 20 mm along Y and 10 mm tall, with one corner on the origin. cube(10) makes a 10 mm cube. Add center = true to centre it on the origin instead:

cube([30, 20, 10], center = true);

The core 3D shapes: cube, sphere and cylinder

Nearly every part starts from these. Full details are in the 3D primitives reference.

cube([20, 20, 10]);                                        // box
translate([35, 10, 10]) sphere(d = 20);                    // ball resting on the bed
translate([60, 10, 0]) cylinder(h = 20, d = 16);           // round post
translate([85, 10, 0]) cylinder(h = 20, d1 = 16, d2 = 0);  // cone

Curves are really polygons. With the default settings ($fa = 12, $fs = 2) a 3 mm hole has only 5 sides and a 20 mm disc has 30. Two lines at the top of a file fix that for every curve:

$fa = 1;      // min degrees per segment
$fs = 0.4;    // min segment length in mm

cylinder(h = 10, d = 3);                          // now 24 sides instead of 5
translate([10, 0, 0]) cylinder(h = 10, d = 3, $fn = 6);   // $fn forces an exact count: a hexagon

Move and rotate shapes with translate() and rotate()

A transform applies to the single shape (or { } block) that follows it. There's no semicolon between the transform and its shape. More examples: transformations reference.

translate([20, 0, 0]) cube(5);                     // moved 20 mm along +X
rotate([0, 0, 45]) cube(5);                         // spun 45° around Z
mirror([1, 0, 0]) translate([10, 0, 0]) cube(5);    // lands on the -X side

Transform order matters

Read a chain from the shape outward. Swapping two transforms usually moves the part somewhere else entirely:

// A: rotate the rod first, then move it. It lies along X from x = 20 to 30, resting on the bed.
translate([20, 0, 2]) rotate([0, 90, 0]) cylinder(h = 10, d = 4);

// B: same two steps, swapped. The move gets rotated too, so the rod ends up 20 mm below the bed.
rotate([0, 90, 0]) translate([20, 0, 2]) cylinder(h = 10, d = 4);

To transform several shapes at once, wrap them in braces:

translate([0, 0, 5]) {
  cube(10);
  translate([5, 5, 10]) sphere(3);
}

Combine shapes with union, difference and intersection

Booleans do most of the modelling work in OpenSCAD. There are three (full boolean guide):

• union() merges its children into one solid. Shapes listed side by side at the top level are unioned for you.
• difference() keeps the first child and subtracts every child after it.
• intersection() keeps only the volume that all children share.

Drill a hole through a plate:

difference() {
  cube([40, 40, 4]);                                // the plate
  translate([20, 20, -1]) cylinder(h = 6, d = 6);   // the cutter, 1 mm past each face
}

And a dice blank, the overlap of a cube and a sphere:

intersection() {
  cube(20, center = true);
  sphere(d = 27, $fn = 96);
}

Make it parametric with variables and modules

Name your dimensions once and reuse them everywhere:

plate_w = 40;
plate_t = 4;
hole_d  = 6;

difference() {
  cube([plate_w, plate_w, plate_t]);
  translate([plate_w / 2, plate_w / 2, -1])
    cylinder(h = plate_t + 2, d = hole_d);
}

A module is reusable geometry with its own parameters. A function returns a value:

module mounting_hole(d = 3.4, depth = 4) {
  translate([0, 0, -1]) cylinder(h = depth + 2, d = d, $fn = 32);
}

function inch(x) = x * 25.4;

difference() {
  cube([inch(2), inch(2), 4]);              // 50.8 × 50.8 × 4 mm plate
  for (x = [6, 44.8], y = [6, 44.8])
    translate([x, y, 0]) mounting_hole();   // four M3 clearance holes
}

Repeat with for loops and choose with if

A for loop places one copy of its body per value. Ranges are written [start : step : end], and the end is included:

for (x = [0 : 10 : 40])                 // 0, 10, 20, 30, 40
  translate([x, 0, 0]) cylinder(h = 5, d = 6, $fn = 32);

for (p = [[0, 20], [20, 20], [10, 35]])  // or loop over a list of points
  translate([p[0], p[1], 0]) cylinder(h = 5, d = 4, $fn = 32);

Use if to switch geometry on and off, and the ? : operator to pick a value:

rounded = true;
plate_h = rounded ? 4 : 3;     // ? : picks a value

if (rounded) {
  hull()
    for (x = [3, 27], y = [3, 17])
      translate([x, y, 0]) cylinder(h = plate_h, r = 3, $fn = 32);
} else {
  cube([30, 20, plate_h]);
}

That rounded plate uses hull(), which wraps the shapes in the tightest convex skin. Four cylinders in, one rounded rectangle out.

Build a parametric L-bracket in OpenSCAD, step by step

Time for a real part: an L-bracket for M3 screws with two holes in each leg. Tick the steps off as you go.

1. Name the dimensions. Leg length, width, thickness and hole diameter go at the top, each with a comment so they show up as labelled sliders.
2. Model one leg as a module. plate() is a flat cube with two holes cut out by difference().
3. Keep the holes clear of the corner. Holes at 45% and 80% of the leg leave room for a screw head next to the other leg.
4. Reuse the module for the upright leg. rotate([0, -90, 0]) stands the plate up, and translate([thick, 0, 0]) moves it onto the corner.
5. Union and render. Check that the holes go all the way through both legs.
6. Export and print on its side. With the L flat on the bed, layer lines run around the corner, which is stronger than printing it standing up.

// L-bracket for M3 screws. All sizes in mm.

// Length of each leg
leg = 40;        // [20:80]
// Bracket width
width = 20;      // [10:40]
// Wall thickness
thick = 4;       // [2:8]
// Screw hole diameter (3.4 = M3 clearance)
hole_d = 3.4;
$fn = 48;

module plate() {
  difference() {
    cube([leg, width, thick]);
    // two holes, kept clear of the inside corner
    for (x = [leg * 0.45, leg * 0.8])
      translate([x, width / 2, -1])
        cylinder(h = thick + 2, d = hole_d);
  }
}

union() {
  plate();                                              // horizontal leg
  translate([thick, 0, 0]) rotate([0, -90, 0]) plate(); // vertical leg
}

Now change it. Every edit should take one number:

• Set leg = 60 and watch the holes move with it.
• Set thick = 6 for a stiffer bracket.
• Set hole_d = 4.5 to take M4 screws.
• Challenge: add a triangular gusset at each edge. Hint: hull() a flat thin cube and a standing thin cube.

Export STL or 3MF from OpenSCAD for your slicer

• Desktop OpenSCAD: press F6 to render, then File → Export → Export as STL (F7). 3MF, OFF and AMF are in the same menu. A preview (F5) can't be exported.
• PrintPal editor: open the File menu and choose Export STL (binary) or Export 3MF (printable). Advanced mode adds Export STEP (faceted), Export OFF (text) and Export OpenSCAD source.

Common OpenSCAD beginner mistakes and how to fix them

Skip the typing: describe the bracket to the CAD Agent

PrintPal's CAD Agent writes OpenSCAD from plain English, runs it in the same in-browser OpenSCAD (with BOSL2 and MCAD), and turns the parameters into sliders. Try the bracket you just built and compare its code with yours. The button only fills in the prompt. Nothing is sent until you press send.

For prompts that produce clean, dimensioned parts, read the text-to-CAD prompting guide.

Frequently asked questions

Related articles

Tools for thisAll tools

CAD AgentDescribe a part in plain English and get editable OpenSCAD with a live 3D preview and STL or 3MF export.

Watch it doneVideo library

0:57 Parametric CAD from a photo using PrintPalTools 0:25 turn text to mechanical parts for 3D printingTools 2:12 CAD Agent, but the Prompts DoubleIdeas

Was this article helpful?

Yes Not really

Send

Thanks! We read every note and use them to decide what to update next.