Introduction to 3D modelling

3D modelling is the precursor to CNC machining (subtractive manufacture) and 3D printing (additive manufacture). Since computer screens and computer mice only give us a 2 dimensional view/UI, defining 3D forms needs to be done in a particular way. Of course, there are new technologies, such as 3D scanning pens, that allow defining a model simply by waving a pen in the air but these best suit specific use cases (such as copying an existing form). Typically, 3D volumes, even very complex ones, are created using a collection of operations executed on-screen.

Choosing a 3D modelling package

There are many modelling packages out there. We will use Fusion 360 because of four reasons:

  1. it is free for hobby use
  2. it runs on Mac and PC
  3. it is well-featured and aligns well with industry-standard Autodesk workflows
  4. it includes a CAM package, which allows defining tool paths for carving 3D forms from solid volumes (such as cutting volumes from perspex).

Fusion 360 can be downloaded from here:

Defining a model

3D modelling platforms typically offer 2 ways to build models.

5The first concerns ‘extruding’ a 2D shape. This is a simple and powerful technique, where a simple 2D shape can be drawn on a singular plane. It is then ‘extruded’ (pulled or pushed) along an axis to create a volume. This technique can be used over a straight axis … or the extrusion can occur on a curved path.



fig4The second technique involves effecting manipulations (such as ‘boolean’ operations) on existing volumes. For example, it is possible to ‘subtract’, ‘add’ or ‘intersect’ two volumes.

It is also possible to ‘cut’ a volume by using a defined plane.

Typically, 3D forms are created using a combination of all the above techniques. Often, creating a 3D form begins by extruding a 2D form, then applying boolean operations on it.

The Chassis of the Polygon Door Artbot begins with a simple 2D form. This will be the starting point for our explorations into 3D modelling and