# Structure
Building a reliable robot starts with a solid structural foundation, the frame and supporting components that everything else attaches to. A well‑designed frame provides rigidity, aligns mechanisms properly, protects internal systems, and ensures your robot meets FRC perimeter and bumper rules.
In FRC, you’re constantly balancing:
* Weight (lighter = faster, easier on motors)
* Strength (won’t bend or break)
* Stiffness (won’t flex)
* Manufacturability (can your team actually make it?)
* Cost & availability
No single material is best everywhere.
## Material Choices
Material
Strength
Weight
Impact Resistance
Stiffness
Best Use
Aluminum
High
Medium
Medium
Medium
Structure
Polycarb
Medium
Light
High
Low
Intakes, guards
Perf Poly
Low
Very light
Medium
Very low
Electronics mounting
Steel
Very high
Heavy
Medium
High
Shafts, high-load parts
3D Print
Low–Medium
Variable
Low–Medium
Low
Custom parts
### 1. Aluminum
The primary structural material in FRC robots.
**Key properties:** Excellent strength-to-weight ratio, easy to machine and cut, available in many forms (tube, extrusion stock, plate). Most FRC robots are built primarily from aluminum, with alloys like 6061, 5052, and 7075 commonly used.
**Common Uses:** [Drivetrain frame](https://andymark.com/products/am14u6-6-wheel-drop-center-robot-drive-base-2025-frc-kit-of-parts-drive-base), [structural members](https://andymark.com/products/pre-drilled-box-tube-extrusion), [gussets](https://andymark.com/products/1-2-in-pitch-gussets), [spacers](https://andymark.com/pages/search-results-page?q=aluminum%20spacer), [shafts](https://andymark.com/products/0-5-in-7075-aluminum-hex-shaft-stock), [gears](https://andymark.com/products/standard-20-dp-gears?variant=), and [plate](https://andymark.com/products/47-in-x-24-in-aluminum-sheets).
**Limitations:** Can bend under high impact, less stiff than steel
**Default to aluminum when:** You need structure, you care about weight, or you can machine parts.
{% hint style="info" %}
The 2025 kitbot used aluminum tube structure and machined aluminum gusset plates.
{% endhint %}
### 2. Polycarbonate
Polycarbonate (often called Lexan) is the most common plastic in FRC.
**Key properties:** Very high impact resistance, flexible (bends instead of breaking), lightweight. Polycarbonate is widely used in FRC because it can take hits and return to shape without cracking.
**Common uses:** [Sheets](https://andymark.com/products/0-220-in-thick-36-in-x-14-in-polycarbonate-sheet), [rollers](https://andymark.com/products/polycarbonate-and-silicon-tubing-kit), intake arms, mechanisms outside the frame, shields and guards, and other flexible structural elements.
**Limitations:** Low stiffness (can flex too much), can deform under sustained load
**Default to polycarbonate when:** A part will get hit and needs to flex instead of fail
{% hint style="info" %}
The 2026 kitbot used polycarbonate sidewalls for the hopper
{% endhint %}
### 2b. Perforated Polycarbonate
Polycarbonate sheet with a grid of pre-drilled holes.
**Key properties:** Lightweight, very easy to assemble with, modular mounting pattern. Use perf poly when you need fast assembly and a flexible layout for components.
**Common uses:** [Sheets](https://andymark.com/products/0-03-in-thick-perforated-polycarbonate-sheet), electronics boards, and quick prototyping.
**Limitations:** Low stiffness due to holes, not suitable for structure
**Default to perf poly when:** You're prototyping, need a lot of hole in one piece, or wiring your electronics.
### 3. Steel
High-strength metal used selectively.
**Key properties:** Very high strength, high stiffness, good wear resistance. Steel is stronger than aluminum but significantly heavier and harder to machine.
**Common uses:** [Corner brackets](https://andymark.com/products/bumper-wood-corner-bracket), [shafts](https://andymark.com/products/1-2-in-steel-hex-shaft-stock), [gears](https://andymark.com/products/standard-20-dp-gears?variant=44493353910444), high-stress components, adding weight to shift your center of gravity or adding to inertial momentum.
**Limitations:** Heavy, harder to fabricate
**Default to steel when**: Loads are very high, failure would be critical, or more weight is needed in certain positions.
### 4. 3D Printed Materials
Additive manufacturing plastics - typically [PLA](https://andymark.com/products/black-bambu-pla-basic-3d-printer-filament-1-75mm), PETG, ABS, and Nylon.
**Key properties:** Highly customizable geometry, fast iteration and prototyping, lightweight. 3D printing is widely used in FRC because it enables rapid iteration and custom parts that would be difficult to machine.
**Common uses:** Sensor mounts, wire management, pulleys and spacers, prototypes
**Limitations**: Weaker than metals, layer-based weakness (direction-dependent strength), can fail under shock loads
**Default to 3D printing for:** Custom geometry, low-to-medium load parts, rapid iteration
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