Overview

I’ve been looking at getting a CNC mill to machine small, strong, metal parts. Initially I looked at the chinese mills such as the 3018 ($400). But they have a reputation of not lasting very long. Then I moved on to the Shapeoko 3 ($1550) and OpenBuilds C-Beam ($1200), but they’re too big to fit comfortably in an apartment. The Carbide3D Nomad ($2750) would be perfect. It is rigid, compact and easily enclosed.

I decided that this would be a great chance to learn and design my own CNC mill.

Design Objectives

  • Rigid, to cut aluminium
  • Enclosed and quiet
  • Minimal fabrication, using as many off-the-shelf parts as possible
  • Compact, to fit in an apartment

Key Parameters

  • Work area: 200mm x 200mm x 100mm
  • HGR20 Linear Rails
  • 2x HGR20 linear rails for each axis
  • SFU1204 Ballscrews with NEMA 23
  • 1500W air-cooled Spindle

Summary

  1. Aluminum profiles bolted together
  2. Linear rails and ball screws for all axes

Finite Element Analysis

I used FEA simulation to get an idea of the strain and deformation that I will see in the frame. The fact that the extrusions are bolted together complicates things, because it cannot be modeled as one large, ‘bonded’ component.

To approximate the fasteners, I set

  1. The extrusions to not interact with each other
  2. The gussets and connectors to ‘bonded’ with every other component

X-Axis

Y-Axis

Simulations were done along the x and y axes with a force of 10N.