3-axis gantry CNC mill

The problem

I wanted to machine aluminium parts accurately and flexibly — not just plastic, and not just via a cheap controller with mushy step timing. That meant a machine rigid enough for aluminium, and a motion controller with real stepping/pulse discipline.

Constraints

• Aluminium cutting loads. Frame and spindle stiffness matter more than anything electronic.
• Step timing has to be deterministic. Jitter in step pulses shows up as surface finish problems, and no amount of CAM tweaking fixes it.
• Safety. A spindle at speed with a hand near the toolpath is not a place for optimistic wiring.

What I did

Selected a Mesa 7i96S FPGA motion controller, which does the step generation and I/O in hardware — the pulses are timed by the FPGA, not by Linux scheduling jitter.

Configured LinuxCNC with a real-time kernel and tuned it: CPU isolation for the RT thread, IRQ affinity so interrupt handling doesn’t land on the same core, and verified latency under load before cutting anything.

Integrated the VFD spindle — speed control and monitoring tied into LinuxCNC so spindle state is part of the G-code, not a manual step.

Built the electrical and control panel with proper safety practice, and do the CAM in Fusion 360.

Trade-offs

• Mesa FPGA + LinuxCNC over a standalone controller board. More setup, a Linux host, and more configuration files — but hard-real-time step generation and a system I can debug at every level.
• Real-time tuning is manual and machine-specific. I measured latency rather than trusting a canned config, because borrowing someone else’s numbers is how people get mystery stalls.

Status

Running and cutting aluminium. Still finishing enclosure and dust extraction, and refining the tool-height workflow.

What I’d do differently

I’d design the panel and the enclosure around each other from the start. The wiring came out right, but neat cable routing was an afterthought and it shows.