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Free 3D Printing and CNC Software — What Really Replaces Simplify3D and Mastercam, and What Does Not

Free 3D Printing and CNC Software — What Really Replaces Simplify3D and Mastercam, and What Does Not

Anyone who 3D prints or mills on a CNC runs into paid tools quickly: Simplify3D for slicing, and Fusion or Mastercam for toolpaths. The real question for an engineer or student is not whether a free alternative exists, but whether a free chain — from model, through G-code, to a machine that actually moves — holds up on real work.

Every tool here is open source and free, including for commercial use. Each one comes with an honest note on where it stops.

Slicers: from model to printer G-code

1. PrusaSlicer

Unusually fine control: parameters that change with height, hand-painted supports and modifiers for one region of a part. For a functional part or a jig, that is the difference between a print that carries load and one that splits between layers. It also works with printers from other manufacturers.

What is missing: the depth of settings takes time to learn, and a profile for a non-Prusa printer may need manual tuning.

2. OrcaSlicer

A fork of PrusaSlicer that adds a series of built-in calibration tests — flow rate, pressure advance, temperature, maximum volumetric speed and interlayer adhesion. It saves hours of trial and error with PETG, ABS or reinforced nylon.

What is missing: it is a fast-moving community project, so settings and profiles can change between releases.

3. UltiMaker Cura

The easy entry point: a very large profile library for printers and materials, a split between basic and advanced settings, and a plugin system.

What is missing: region-level control is less direct than in PrusaSlicer. Many engineers simply install both.

Modelling for printing and machining

4. FreeCAD

A parametric modeller with a history tree and STEP and STL export. Since version 1.0 the former Path workbench is called CAM and includes a new simulator: you set up a job, tools and operations such as profile and pocket, then write G-code through a post-processor.

What is missing: a real learning curve, and the CAM side needs more manual setup and checking than Mastercam or Fusion.

5. OpenSCAD

You write code instead of drawing, so every dimension is a genuine parameter. One file can produce a whole family of clamps, brackets and adapters by changing a variable.

What is missing: there is no mouse-driven sketch, and anyone uncomfortable with code will struggle.

CNC: toolpaths, simulation and control

6. DXF2GCODE

It takes 2D contours from a DXF or PDF drawing, lets you set tool, feed and cutting order, and writes G-code for milling, plasma or laser cutting.

What is missing: it is 2D only, and there is no macOS version.

7. CAMotics

It runs G-code from any CAM system and shows in 3D what the tool will remove from the stock, catching a rapid move into material, a tool that never reaches depth, or a shape different from the one you intended.

What is missing: it is a verification tool, not full CAM — it does not plan machining strategies from a CAD model.

8. LinuxCNC

It turns an ordinary PC into a real-time controller for a mill, lathe or plasma table, including five-axis kinematics. It is the basis of many retrofits where an old machine’s original controller has died.

What is missing: Linux only, with a real-time kernel and suitable interface hardware. Configuration requires understanding the machine and its electrics.

Nesting parts for cutting

9. Deepnest

It reads DXF, SVG and CDR, arranges parts on the sheet while continuously searching for a better layout, places small parts inside holes in larger ones and merges shared cut lines to shorten machine time.

What is missing: it nests only — toolpaths and cutting order come from another tool.

So can you drop Simplify3D and Mastercam?

Simplify3D — almost always yes. The three free slicers cover functional printing: OrcaSlicer for calibration, PrusaSlicer for control, Cura for a quick start. For CAM the answer is partial. For 2.5D work, sheet cutting and machine retrofits, the chain of FreeCAD or DXF2GCODE, a check in CAMotics and LinuxCNC on the machine is enough. For complex 3D and multi-axis production machining, commercial CAM still saves significant time.

Students and makers can start with Cura or PrusaSlicer plus OpenSCAD or FreeCAD; a small workshop with a plasma or router table gains most from Deepnest, DXF2GCODE and CAMotics together.

More tools in the 3D and CAD categories.

Further reading