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.
![](V5_5_front_thumbnail.png#center)
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
- Aluminum profiles bolted together
- 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
- The extrusions to not interact with each other
- The gussets and connectors to ‘bonded’ with every other component
X-Axis
![](X_stress.jpg#center)
Y-Axis
![](Y_stress.jpg#center)
Simulations were done along the x and y axes with a force of 10N.