How to choose the right material for building a combat robot

Choosing the right material is one of the most important decisions when building a combat robot. The right choice determines whether the robot will survive a crushing blow, whether it will be fast enough, and whether it will even fit within the weight limit. The choice depends primarily on three factors: which part of the robot you will use the material for, which weight class you are competing in, and what your robot’s strategy is.

List of suitable materials

Below is the list of the most suitable materials across all weight categories:

  • Overture Super PLA+ / eSun PLA-ST: Modified PLA that is significantly tougher and more durable than standard PLA.

  • TPU: A flexible material that acts as a bumper, great for absorbing shocks.

  • Cast Polyurethane (PU) / Silicone: PU has extreme abrasion resistance and excellent shock-dampening properties. It is essentially a tough rubber that will not tear even under high stress.

  • Nylon: Has excellent impact toughness and resistance to material fatigue.

  • HDPE: A tough material in sheet form; it does not shatter upon impact but bends instead and is very lightweight.

  • UHMW-PE: An extremely wear-resistant and impact-resistant plastic, even more durable than HDPE.

  • G10 / FR4 Fiberglass sheet: Extremely rigid, lightweight, and impact-resistant. It often replaces aluminum where weight savings are needed while maintaining high strength.

  • Polycarbonate sheets: Compared to printed PC, these sheets have much higher toughness due to the rolling structure. Ideal for transparent protective covers or base plates.

  • Carbon fiber composite: Excellent rigidity at minimal weight. Used as reinforcement or covering plates.

  • Aluminum 7075: Has an excellent strength-to-weight ratio.

  • Titanium (Grade 5): A top-tier material for weapons and parts that must withstand direct collisions. It is lighter than steel and extremely resistant to deformation.

  • Hardox: The king of the arenas. Used for front wedges and weapons that must withstand direct hits from spinners. It is practically indestructible, though heavy.

  • S7 Tool Steel: Steel specifically designed to withstand impacts. Often used for manufacturing weapons or the striking parts of hammers, where standard steel might crack.

Of course, there are other materials with suitable properties; this is just an overview of the most commonly used and easily accessible ones.

Selection according to strategy

  • Spinner: The majority of the weight must be allocated to the weapon and the drivetrain. The body should be as lightweight as possible, and the armor as durable as possible, especially in areas prone to frequent hits.

  • Flipper or other control robots: The weapon is relatively lightweight, so more weight remains for a robust body and durable armor. The goal is to survive hits and control the opponent.

Practical procedure for material selection

  1. Set a financial budget and a weight limit.

  2. Decide on the robot type and strategy.

  3. Perform a weight breakdown: Estimate the weight of the mandatory components (motors, battery, electronics).

  4. Allocate the remaining weight: Based on your strategy, distribute the remaining weight among the weapon, armor, and body.

  5. Select specific materials: Considering the allocated weight and the function of individual parts, choose the most suitable materials from the list above.