Week 02 — Computer-Aided Design¶

Focus this week¶

I have some experience in Fusion 360, but this week I wanted to:

learn Joints and Motion tools (to test ideas for my final project)
understand how linear motion is defined and simulated
explore OpenSCAD as a code-based parametric CAD tool
compare traditional CAD (Fusion 360) with script-based modeling (OpenSCAD)

Tools I used¶

Fusion 360 (joints, motion, assembly tests)
OpenSCAD (parametric / code-based modeling)

Part A — Fusion 360 (Linear Actuator, Joints & Motion)¶

Goal

For my final project I plan to use linear actuators, so this week I focused on:

building a simple linear actuator model
understanding how linear motion is defined in Fusion 360
testing motion limits and constraints

Initial actuator test (components vs bodies)

First, I built a simple two-part model that connects and moves relative to each other.

Instead of modeling everything as bodies, I created separate components.
This is important because joints in Fusion 360 only work between components, not bodies.

Creating separate components

Model building process

I started by creating a 2D sketch on the base plane.

Drew simple geometry using rectangle and line tools
Applied dimensions to control size
Used constraints to keep the sketch stable

Base sketch for first component

Then I converted the sketch into a 3D model using the Extrude tool.

Defined thickness of the part
Repeated the same process for the second part

Extruding sketch into 3D body

Simple component connection test

After that, I positioned the two components and prepared them for motion testing.

Two simple parts prepared for connection

Next, I used the Joint tool in Fusion 360.

Selected both components
Defined a Slider Joint
Set the direction of movement

This joint allows motion only along a single axis, simulating a linear actuator mechanism.

Motion testing and observations

After applying the joint, I tested the movement:

the components moved smoothly along one axis
motion depended on proper alignment of joint origins

Motion Test

This helped me understand how constraints define real mechanical behavior in Fusion 360.

Reflection

This simple test helped me understand:

the importance of using components instead of bodies
how joints define movement
how Fusion 360 can simulate real mechanical systems

This will be useful for designing more complex actuator systems in my final project.

Part B — OpenSCAD (Parametric CAD Using Code)¶

Goal

After working with Fusion 360 and motion tools, I wanted to explore a different CAD approach.
For this purpose, I used OpenSCAD, which is a script-based parametric modeling tool.

The goal was to:

understand code-based modeling
compare it with traditional sketch-based CAD
create a simple parametric mechanical part
generate fabrication-ready geometry

Why OpenSCAD?

Unlike Fusion 360, OpenSCAD does not use sketches or graphical constraints.
Instead, geometry is defined entirely using code, variables, and logic.

This makes it:

fully parametric
very precise and repeatable
easy to modify by changing a few variables

However, it does not support:

assemblies
motion simulation
joints

OpenSCAD is more suitable for geometric and repeatable parts, rather than complex mechanical assemblies.

First Parametric Test

To understand the workflow, I created a simple parametric block.

Example code:

length = 50;
width  = 20;
height = 30;

cube([length, width, height]);

By changing the values of length, width, or height, the model updates instantly.

Adding Features (Boolean Operations)

Next, I modified the model by subtracting a hole using the difference() function.

difference() {
    cube([60, 20, 10]);

    translate([30, 10, 5])
        cylinder(d = 8, h = 20, center = true);
}

This introduces the concept of boolean operations, which are fundamental in OpenSCAD:

union() → combine shapes
difference() → subtract geometry
intersection() → keep overlapping volume

Simple Disc Geometry in OpenSCAD

To build a more realistic mechanical example, I created a parametric disc with bolt holes.

The model consists of:

one main cylindrical body (disc)
one center hole
multiple bolt holes distributed evenly on a circular pattern

Full OpenSCAD Code

// ===== Parameters =====
disc_d    = 160;   // Disc diameter
disc_thk  = 10;    // Thickness
center_d  = 50;    // Center hole diameter

bolt_count = 5;    // Number of bolt holes
bolt_pcd   = 100;  // Bolt circle diameter
bolt_d     = 10;   // Bolt hole diameter

// ===== Main Geometry =====
difference() {

    // Main disc
    cylinder(d = disc_d, h = disc_thk, center = true);

    // Center hole
    cylinder(d = center_d, h = disc_thk + 2, center = true);

    // Bolt hole pattern
    for (i = [0 : bolt_count - 1]) {

        angle = 360 / bolt_count * i;

        translate([
            (bolt_pcd / 2) * cos(angle),
            (bolt_pcd / 2) * sin(angle),
            0
        ])
        cylinder(d = bolt_d, h = disc_thk + 2, center = true);
    }
}

Code Explanation

The model is fully controlled by parameters:

disc_d → overall disc diameter
disc_thk → thickness
center_d → central hole
bolt_count → number of holes
bolt_pcd → bolt circle diameter
bolt_d → hole size

The difference() function subtracts all holes from the main disc.

A for loop is used to:

evenly distribute bolt holes
calculate angular positions
place holes using translate()

This makes the model fully parametric and scalable.

Exporting Files

After finishing the model, I exported it as:

STL file for fabrication

Then I verified the STL in a slicer to confirm:

correct scale (mm)
no geometry errors
clean mesh

Reflection

This exercise demonstrated the difference between visual CAD and code-based modeling.

Fusion 360 → intuitive, visual, good for assemblies
OpenSCAD → precise, parametric, ideal for repeatable parts

I found OpenSCAD especially useful for parametric mechanical components where dimensions may need to change frequently.

Image Optimization Workflow¶

To keep the website lightweight, I used a VS Code extension to compress images and convert them to WebP format.