How to 3D model a combat robot

There are many programs available, ranging from simple to professional. To start with, these are excellent choices:

• Autodesk Fusion 360: Very popular in the robot builder community. It is free for hobby use and startups. It is extremely powerful, yet has a friendly learning curve. It offers great tools for precision modeling.

• Tinkercad: A completely free, web-based program, ideal for absolute beginners. You work by assembling and removing basic shapes (cubes, cylinders). It may be sufficient for simple chassis, but it is no longer suitable for more complex robots.

• Onshape: A professional CAD with a free version for public projects. You don’t need to download it as it runs through a web browser. The disadvantage of the free version is that, theoretically, anyone can look at the model you have created.

First, you always need to consider what kind of robot you actually want to build, what it will look like, what weapon and drive system it will have, and what it should be capable of. After that, you must find suitable electronics to get the robot moving. Once the initial concept is ready, it is helpful to put it on paper, at least in the form of a simple sketch that you can stick to throughout the modeling process.

Never start modeling “blind.” First, you must know everything that needs to fit inside the robot.

• Measure all components: Take a caliper or a ruler and measure all the parts that will go inside the robot: motors, wheels, electronic speed controllers (ESC), the signal receiver, the battery, the power switch, and, most importantly, your weapon system.

• Create models of the components: In your CAD program, create simple cuboids or cylinders that exactly match the dimensions of your components. This will help you visualize how much space they will take up. Alternatively, you can download existing models for common parts.

• Test the layout of components: Try to arrange the components next to each other so that they take up as little space as possible, but don’t forget to leave room for the cables. This will give you an idea of how big your robot will be and whether the design is even realistic.

With a prepared plan, modeling is much easier.

• Start with the base: Create the robot’s bottom plate, ideally 2–3 mm thick.

• Place the components: Place your component models onto the base. Arrange them so that the robot is well-balanced and everything fits. Don’t forget to leave space for cable routing.

• Create the walls: Build the outer walls of the robot around the components. Consider the thickness – the walls need to be durable. For an antweight robot, a wall thickness of around 2.7 mm is a good starting point.

• Integrate mounts: Add holes for screws or threaded inserts, tabs, and brackets for securing motors, the battery, or other electronics. It is good to think about how to easily disassemble and repair the robot.

• Design the top cover: The body often consists of a bottom “tub” and a top cover. Figure out how the cover will be secured – most commonly using screws and threaded inserts embedded into the body.

The model must be not only functional but also easy to print.

• Avoid large overhangs: A 3D printer prints in layers. If a layer overhangs the one below it by more than 45–60 degrees, it will require temporary supports that must be removed after printing. Try to design the model so that as few supports as possible are needed.

• Use fillets: Sharp internal corners are weak points where cracks occur and parts of the frame can snap off. By adding fillets (rounding them), you will significantly increase the strength of the part.

• Correct orientation: Think about how you will print the part while you are still modeling it. 3D printed parts are weakest at the bond between individual layers. The part should be oriented so that the expected impact force does not act in a direction that could peel the layers apart.

• Think about extrusion width: Every print nozzle has a diameter and a recommended extrusion width. A standard 0.4 mm nozzle will print a line approximately 0.42–0.45 mm thick with default settings. It is therefore a good idea to optimize wall thicknesses so that they are multiples of the extrusion width, especially if the wall is made only of external perimeters (without infill).

• Export to STL or 3MF: Once you are satisfied with the model, export it to STL or 3MF format. These are standard formats that slicing software (for print preparation) understands.