CAD for Combat Robots

Designing your robot in CAD (computer-aided design) software lets you check that everything fits, keep track of weight, calculate your weapon's energy, and send files straight to a 3D printer or a cutting service. Most competitive robots today are designed in CAD first. This page compares popular software and gives tips for designing combat robots. See also OnlineTools for calculators and design tools.

Software licenses and prices change often. The terms below were checked in October 2026; check the vendor's site before you choose.

Choosing software

Software	Cost	Notes
Onshape	Free plan for non-commercial use; free education plan for students and teachers	Runs in a web browser, so it works on almost any computer. On the free plan, all your documents are public. The education plan allows private documents.[1] Very popular with robot builders, and easy to share designs.
Autodesk Fusion	Free for personal use; full version $680/year	The free personal-use version is limited to personal, non-commercial projects (under $1,000 a year in revenue), with limited CAM, drawings and export file types. Widely used, with lots of tutorials.
FreeCAD	Free and open source	Version 1.0 (2024) and 1.1 (2026) fixed many long-standing problems and added a built-in assembly workbench. Runs offline on Windows, Mac and Linux.
SOLIDWORKS for Makers	About $48/year	The industry-standard professional software, licensed for personal non-commercial use.
Shapr3D	Free basic plan (2 projects, limited exports); Pro $299/year	Designed for tablets and touch, also on desktop. Free for students and teachers.
Tinkercad	Free	Browser-based and very easy to learn. Great for simple printed parts and for beginners, but limited for complex designs.

Blender is a powerful free 3D modeling program, but it's designed for art and animation rather than precise mechanical parts, so it's not a good fit for robot design.

A typical workflow

1. Start with the parts you're buying – motors, battery, ESCs, wheels, weapon motor. Download CAD models where they exist, or model them from their datasheets.
2. Arrange them to find the smallest, best-protected layout.
3. Design the frame and armor around them, as sketches turned into 3D parts (extrudes, cuts and fillets).
4. Assemble everything to check fit, wire routing, weapon clearance and how the robot sits when it's upside down.
5. Check the weight by assigning materials to each part (see below).
6. Export files for making the parts:
   • STL or 3MF for 3D printing (see 3D Printing)
   • DXF (flat 2D outlines) for laser and waterjet cutting
   • STEP for CNC machining and for sharing models (see Fabrication Services)

Tips for combat robots

• Use mass properties. Most CAD programs can calculate a part's or assembly's mass and moment of inertia once you assign materials. Onshape, for example, has a Mass Properties tool for parts and assemblies.[2] Use it to keep a running weight budget, and to calculate your weapon's moment of inertia and stored energy (see Spinner Design). Leave a margin for wires, screws and glue, which are easy to forget.
• Design in parameters. Base your sketches on dimensions you can change (like wheel diameter or plate thickness), so you can quickly adjust the design.
• Use real hardware models. McMaster-Carr has free CAD models for most of its parts, and Fusion can insert them directly.[3] Community models of robot parts are on GrabCAD, but check their dimensions against the real part.
• Design for repair. Make the parts that get damaged most (wedges, armor panels, weapon teeth) easy to replace, and design so you can reach the battery and switch quickly.
• Check the robot both ways up and from every side for exposed wheels, wires and weak points.
• Learn from others. Many builders publish their CAD – see the designs listed on 3D Printing.

Further reading

• Repeat Robotics – Combat Robot Design Handbook – a free guide to designing a beetleweight from scratch
• OnlineTools – calculators for weapons, drive and more
• Armor and Materials