Automatic Tool Changer for Carvera Air
A hardware and firmware retrofit
CAD drawings, final build, control board I/O, and machine setup — click thumbnails or use arrows to browse
Overview
The Carvera Air is a capable desktop CNC machine, but it ships without ATC. For multi-tool jobs, every stop means a manual swap, inconsistent offsets, and broken workflow. I wanted to fix that, so I designed and prototyped a full ATC retrofit inspired by its bigger sibling, the Carvera, but with more tool slots.
This project is built on top of the Carvera Community Firmware. Orginally, I have to modified the controller firmware and software to make it work, but now support for ATC-equipped Carvera Air configurations was added upstream by the maintainer, so it will work for anyone in the future that does this mod.
Latest Dev Firmware and Controller add support for ATC-equipped machine
Mechanical Design
The tool changer mechanism had to fit within the Carvera Air's footprint without major structural changes. Key design constraints were drawbar force, tool rack indexing accuracy, and clearance during a tool change cycle. I went through several iterations before it was reliable enough to run unattended.
Original quick-change mechanism in clamped position (0° relative) — click thumbnails or use arrows to browse
ATC tool magazine and BGX-35N laser sensor — click thumbnails or use arrows to browse
Lever Range
All angles reference the back plate as 0°, not the lever's own relative position. To convert any value to lever-relative position, subtract the start angle (0.55°).
| Position | Angle | Description |
|---|---|---|
| Start (Clamp) | 0.55° | Lever fully pressed - maximum clamp force applied |
| Neutral Clamp | 1.0° – 1.5° | Natural spring-back resting position while clamped |
| Spring Range | up to 16.8° | Low force region - spring is the dominant force |
| Drawbar Pull Range | 16.8° – 61.4° | Drawbar is being pulled, beginning to open the collet |
| Unclamp (Hold) | 61.4° – 77.2° | Fully unclamped - lever stays without input |
| End of Travel | 77.2° | Hard end of travel |
Force vs. Angle
Note: High uncertainty (~20%) - measurements taken by hand with a scale. Values are directional only; do not use at face value.
| Angle (°) | Force (kg) |
|---|---|
| 20.0 | 1.37 |
| 25.0 | 2.80 |
| 27.0 | 4.00 |
| 35.0 | 3.00 |
| 50.0 | 2.60 |
| 53.0 | 3.20 |
| 55.5 | 3.80 |
Maximum force required: 5.80 kg (occurs within the Drawbar Pull Range)
The force curve peaks around 27° before dropping off - I'm pretty sure there is a cam system built into the lever shaft.
Napkin Calculations
Napkin calculations — click thumbnails or use arrows to browse
Results
A full tool change cycle with more tool slots than its big brother, the Carvera.