Intro
A while back I wrote a guide on taking an STL into FreeCAD, converting it to a solid, and running it through the CAM workbench to produce G-code. That process still works, and FreeCAD remains one of the most capable open-source CAD/CAM packages available—deep, flexible, and genuinely powerful when you want full parametric control.
RotatoCAM was built for a narrower, sharper problem: getting simultaneous 4-axis rotary toolpaths out of an STL (or STEP) with as little friction as possible, especially for the DIY machines and controllers most of us actually own. The two approaches overlap in the end goal (a G-code file), but they take very different roads to get there.
FreeCAD workflow (from the earlier article)
- Import the STL.
- Switch to the Part workbench → Create Shape from Mesh → Convert to Solid.
- Optionally refine the shape or wrap it in a Part Design Body.
- Switch to the CAM workbench, create a Job, and set tools/materials.
- Define operations (pocket, profile, drill, 3D Surface, etc.).
- Generate the path and post-process it into the dialect your controller expects.
This is a real, workable pipeline. FreeCAD’s strength is that it can do a lot more than just this one task—parametric modeling, assemblies, drawings, and a growing set of CAM operations all live in the same program. When the geometry is clean and the job is primarily 3-axis, it is a solid, free solution. The trade-offs are the extra conversion steps (mesh-to-solid is never perfect), the workbench switching, and the fact that true simultaneous rotary is not a first-class feature.
RotatoCAM workflow (Universal Workflow)
- Load the model (STL, STEP, OBJ, etc.) — or skip the file entirely and use conversational strategies.
- Define the stock and fixture (for rotary work: bar diameter, length, and distance from the chuck). The preview shows the bar and a wireframe chuck so you can see clearance before you generate.
- Add operations to the queue and choose a strategy for each. A typical rotary part is a radial rough followed by a spiral finish on the same tool.
- Pick the tool.
- Set feeds and the chuck-RPM cap.
- Set Work Zero.
- Generate.
- Preview with the backplot and the material-removal simulator (it plays the actual G-code you are about to export).
- Post to your controller (grblHAL, LinuxCNC, Mach3/4, Centroid, MASSO, and others).
- Verify on the machine.
The sequence stays the same whether you are doing a simple wrapped engraving or a full simultaneous 4-axis spiral finish. One tool per posted program keeps the G-code continuous and avoids mid-job tool changes. Undercuts are measured and flagged before the file is generated. The simulator consumes the posted code, not an idealized preview.
A lot of the useful stuff—radial roughing, continuous spiral finishing, wrapped engraving, stock visualization with the chuck, feed-checked material-removal simulation, and direct posts for the controllers people actually run—is sitting a few clicks away once the model is loaded. No workbench hopping, no separate windows for conversion and cleanup, and no multi-step solid reconstruction before you can even start thinking about toolpaths.
Where RotatoCAM changes the picture
For years, accessible simultaneous 4-axis rotary CAM has been either expensive, subscription-based, or missing entirely from the free/open tools. RotatoCAM treats the rotary axis as a primary capability rather than an afterthought. Radial roughing and continuous spiral finishing are available in the free Community Edition. The stock visualization, chuck-RPM cap, and undercut warnings are built around the reality of a bar in a chuck on a benchtop machine. The result is that a clean STL of a handle, finial, pawn, or similar part can go from file to posted 4-axis G-code without the intermediate solid-conversion and workbench-switching steps required in a general-purpose CAD/CAM system.
FreeCAD is still the better choice when you need full parametric modeling, complex multi-tool 3-axis work, or a single environment that covers design through documentation. RotatoCAM is the better fit when the part is already an STL (or a simple shape) and the goal is to spin it on a 4th axis with a short, repeatable path to G-code.
(And yes, the same core ideas that make the 4-axis path feel straightforward are the ones that make a future 5-axis mode interesting to think about. That is still down the road.)
Closing
Both tools get you to G-code. FreeCAD gives you a deep, open, general-purpose workshop. RotatoCAM gives you a direct, purpose-built route to simultaneous 4-axis rotary toolpaths that used to be out of reach for most DIY setups—most of the interesting pieces are just a few clicks away once the file is loaded. Use the one that matches the job in front of you!
— Rev. J. Money