Choosing the ideal material for your combat bot is a widely discussed and varied decision. Key factors will depend on a few key considerations such as:
- The size of your bot. (1lb, 3lbs, 250lbs, etc.)
- The type of combat event you will attend.
- The design of YOUR bot, including it’s weaknesses and strengths.
- The design of OTHER bots you will compete against.
- What you can afford!
Below are some starting points, links to articles, and other resources to help you in your journey. We strongly recommend you do your research on what other bots of a similar size and competition are made out of. Ask other builders what they use. This can save you a LOT of time and money!
250 lb Heavyweight Bots Article: BattleBots & Choosing the Right Materials Written by Leanne Cushing of Team Valkyrie
Below is a list of common materials used in robot construction of all sizes:
Metal – Aluminum bars or plates (lightweight and pliable) Low cost / Aluminum 6061 is the most commonly used / easy to machine yourself / easy to order designed parts online from vendors like PCBWay or LT Century Prototyping
Metal – Steel bars or plates (strong but less common due to high weight) Medium cost / “mild” steel hot or cold rolled is a good starting place / some alloys like AR500 or Hardox are what is used in 250lb armor and are much more expensive / Here is an example of AR500 “teeth” made for a specific 3lb weapon bar design commonly used. / Many modern bot weapons are made of hardened steel, such as S7 tool steel
Metal – Titanium bars or plates (usually used for wedge construction, forks, or single armor plates on a larger bot) / Medium-High cost / difficult to machine or weld / high strength to weight ratio than most steel options / Typically bought as Grade 5 titanium for a balance of strength and cost efficiency
Plastic – UHMW (ultra high molecular weight polyethylene) (tough plastic similar to a kitchen cutting board) / Low-Medium cost / easy to machine / useful for components that will receive repeated damage or need flexibility (e.g., very large wheels or arms)
Plastic – Lexan panels (plastic, also used for the arena walls) / Low-Medium cost when not used for arena walls / easy to machine / useful for top or side armor to deflect hits without shattering easily (acrylic plastic DOES NOT hold up as well as Lexan)
Other Plastic – 3D printed materials (PLA, PLA+, ABS, TPU, PETG, Nylon, etc. – see the 3D printing section below for more details) / Cost can vary depending on the quality and type of material / TPU90 is commonly used in smaller (1-3lb bots) for it’s ability to flex and retain it’s shape under multiple impacts
Carbon Fiber sheets – Medium-High cost / 2-5 mm thickness is often used in bot body structure and armor / very high impact resistance and low weight / challenging to machine without a CNC router / You can typically order parts you have designed for minimal cost from a vendor, such as CNC Madness.
Are these the only materials I can use? Absolutely not. The only restrictions on construction materials are the event rules and your imagination! Builders have used things from cardboard to wood to copper. Even duct tape! Be creative in your design but always think about the benefits versus drawbacks of the material you are using.
How to choose materials? Every bot typically uses a combination of materials for armor and internal parts depending on your design and placement. (Protecting the wheels, top/bottom plates for the internal electronics and motors, etc.)
As with most materials, each have their own benefits and drawbacks. Some are heavier but stronger, some are more flexible but can tear or bend. Some are light and strong, but are expensive. Choose your materials based on your design and budget, test it, and make changes as needed.
Quick Tip: Iterative design is a design methodology based on a cyclic process of prototyping, testing, analyzing, and refining a product or process. Based on the results of testing the most recent iteration of a design, changes and refinements are made.
3D Printing
3D printing has become extremely popular in recent years. Before you get into 3D printing a bot, make sure understand how it works and the limitations of the materials themselves (filament type). Choosing the wrong filament can mean the difference between a tough bot and one that shatters like glass on impact!
Simplify 3D maintains a fantastic “Ultimate 3D Printing Materials Guide” to help you better understand the qualities and drawbacks of most commercially available 3D filament materials on the market today. Below is a summary to get your started:
- ABS – ABS is a low-cost material, great for printing tough and durable parts that can withstand high temperatures.
- TPU – Flexible filaments, commonly referred to as TPE or TPU, are known for their elasticity allowing the material to easily stretch and bend.
- PLA – PLA is the go-to material for most users due to its ease-of-use, dimensional accuracy, and low cost.
- PLA Plus (+) – This is a newer version of PLA that combines the ease-of-use quality of regular PLA with the durability qualities of ABS.
- HIPS – HIPS is a lightweight material most commonly used as a dissolvable support structure for ABS models.
- PETG – PET and PETG filaments are known for their ease of printability, smooth surface finish, and water resistance.
- Nylon – Nylon is a tough and semi-flexible material that offers high impact and abrasion resistance. It is an ideal choice for printing durable parts.
- ASA – ASA is a common alternative to ABS and is great for outdoor applications due to its high UV, temperature, and impact resistance.
- Polycarbonate – Polycarbonate is known for its strength and durability. It has very high heat and impact resistance making it an ideal choice for tough environments.
- Polypropylene – Polypropylene is great for high-cycle, low strength applications due to its fatigue resistance, semi-flexible, and lightweight characteristics.
- PVA – PVA is commonly known for its ability to be dissolved in water and is often used as a support material for complex prints.
- Metal Filled – Metal filled filaments are made by mixing a fine metal powder into a base material, providing a unique metallic finish and added weight.
- Wood Filled – Wood filaments combine a PLA base material with cork, wood dust, or other derivatives, giving the models a real wooden look and feel.
- Carbon or Glass Fiber Filled – Filaments contain short fibers that are infused into a 3D printable base material to help increase strength and stiffness.
Working with Metals
KEY SAFETY LESSON! Always use extreme caution when using any tool to cut, drill, or weld. Follow the manufacturer’s instructions and use all recommended safety equipment. This is especially true when it comes to working with metal. Trust me, you don’t want to get steel dust particles in your eyes or mouth!
Cutting, Drilling, and Grinding Metals: In general, the tool you use will need to have equal or greater hardness when compared to the metal you are attempting to cut. For example, you would not want to use a saw motor or blade designed for cutting wood on steel or other types of metals.
How do I know if my tool can cut the metal I’m working on? The easiest way to tell if your saw or drill should be used to cut the metal you are working with is to look at the label. Almost all tools, drill bits, and blades used for cutting metal will specifically say so in their description.
Example of saw blades used for cutting wood and plastic. There are typically less teeth on the blade.
Example of saw blade used for cutting soft to harder metals. There are typically many more teeth or the teeth are replaced with a solid coating of a hardened abrasive; such as cobalt or diamond tipped.
