Aluminum
What is an Alloy?
An alloy is a mixture of two or more elements, at least one of which is a metal, that results in a material with properties different from its constituent elements. Aluminum alloys are created by adding elements like magnesium, silicon, copper, and zinc to pure aluminum to enhance specific properties such as strength, corrosion resistance, or machinability.
Common Aluminum Alloys
5052
Pros for FRC:
- Excellent for bending and forming - ideal for sheet metal brackets and panels
- Softer than 6061, making it easier to work with hand tools
- Great for non-structural components that need to be bent
- Good for sheet metal intake flaps or light guards
- Relatively affordable
Cons for FRC:
- Too soft for structural applications or high-load components
- Not suitable for parts requiring precise machining
- Cannot be used for drivetrain or mechanism components under stress
- Difficult to tap threads that will hold under load
6060
Pros for FRC:
- Commonly available in extruded profiles (like 1x1” tubing)
- Good for light structural frames
- Easier to cut with hand tools than 6061
- Welds well for teams with welding capability
Cons for FRC:
- Harder to machine than 6061 - not ideal for CNC parts
- Lower strength than 6061 - not suitable for high-stress applications
- Less common in plate/sheet form
- May not hold threads as well as 6061
6061
Pros for FRC:
- The “go-to” alloy for FRC - excellent for machined parts
- Great machinability - ideal for CNC mills and lathes
- Strong enough for drivetrain components, gearboxes, and structural elements
- Widely available in tube, plate, and bar stock
- Holds threads well
- Good balance of strength, weight, and cost
Cons for FRC:
- More expensive than 5052
- Harder to bend than 5052 - not ideal for formed sheet metal parts
- Requires carbide tooling for best results
- Can be overkill for low-stress applications
7075
Pros for FRC:
- Highest strength - excellent for critical drivetrain components
- Great for parts that need maximum strength with minimum weight
- Ideal for custom swerve modules, gearbox plates, or suspension components
- Machines to a beautiful finish
Cons for FRC:
- Very expensive - often 2-3x the cost of 6061
- Difficult to source in small quantities
- Cannot be welded easily
- Requires careful machining - can crack if machined incorrectly
- Overkill for most FRC applications
- Work hardens quickly - dulls tools faster
Tubing
Common FRC Tubing Shapes
1x1” Square Tubing
Wall Thicknesses:
- 1/16” (0.063”) - Most common for FRC
- Good balance of strength and weight
- Easy to work with hand tools
- Standard for most robot frames
- 1/8” (0.125”) - Heavy duty
- Used for high-stress areas like climbers
- Significantly heavier
- Harder to cut with hand tools
2x1” Rectangular Tubing
Wall Thicknesses:
- 1/16” (0.063”) - Standard choice
- Great for drivetrains and elevators
- Provides directional strength
- 1/8” (0.125”) - Extra strength
- Used for heavy-duty applications
- Often overkill for most FRC uses
1x2” Box Tubing (Versaframe/MAXTube)
Wall Thickness:
- 1/16” (0.063”) with rounded corners
- Lighter than traditional square tubing
- Designed for T-slot nuts and brackets
- Easy integration with gussets and plates
Round Tubing
Common Sizes:
- 1” OD x 1/16” wall - Rotating shafts, lightweight structures
- 1” OD x 1/8” wall - Heavy duty shafts
- 3/4” OD x 1/16” wall - Lighter applications, spacers
Material Recommendations by Application
- Frame/Chassis: 1x1” or 2x1” x 1/16” wall 6061 or 6063
- Elevators: 2x1” x 1/16” wall 6061
- Arms/Manipulators: 1x1” x 1/16” wall 6061
- Climbers: 1x1” or 2x1” x 1/8” wall 6061
Sheet Metal
Lexan (Polycarbonate)
Common Thicknesses for FRC
1/16” (0.063”) Polycarbonate
Best for:
- Light-duty guards and shields
- Electronics panels
- Sponsor panels
Pros:
- Very lightweight
- Easy to cut with hand tools
- Flexible - can bend without breaking
Cons:
- Too flexible for structural use
- Can vibrate at high speeds
- Not suitable for game piece contact generally
1/8” (0.125”) Polycarbonate
Best for:
- Intake guards
- Moderate-duty shields
- Hopper walls
Pros:
- Good balance of weight and stiffness
- Still cuttable with hand tools
- Impact resistant
Cons:
- Can still flex under heavy loads
- May crack at mounting points if over-tightened
3/16” (0.187”) Polycarbonate
Best for:
- Heavy-duty guards
- Structural panels
- High-impact areas
Pros:
- Very stiff and strong
- Excellent impact resistance
- Can handle direct game piece impacts
Cons:
- Heavier weight
- Requires power tools to cut effectively
- More expensive
1/4” (0.250”) Polycarbonate
Best for:
- Extreme impact areas
- Defensive mechanisms
Pros:
- Maximum strength and stiffness
- Nearly indestructible in FRC applications
Cons:
- Heavy - significant weight penalty
- Difficult to machine
- Expensive and often overkill
SRPP (Self-Reinforced Polypropylene)
Overview
SRPP is a composite material that’s becoming popular in FRC as a lighter, tougher alternative to polycarbonate.
Comparison to Polycarbonate
Advantages:
- Lighter weight - Approximately 30% lighter than polycarbonate
- Higher impact resistance - Won’t crack or shatter like polycarb
- Stiffer - Less flex under load
- No stress cracking - Unlike polycarb around bolt holes
Disadvantages:
- More expensive - Typically 2-3x the cost of polycarbonate
- Harder to source - Limited suppliers
- Different machining - Requires different speeds/feeds than polycarb
- Can delaminate - If cut improperly
Common Thicknesses for FRC
1/8” (3mm) SRPP
Best for:
- Intake plates
- Light guards
- Anywhere you’d use 1/8” polycarb but want weight savings
3/16” (5mm) SRPP
Best for:
- Heavy-duty intake systems
- Bumper backing
- High-impact guards
- Structural panels
1/4” (6mm) SRPP
Best for:
- Extreme impact applications
- When maximum stiffness is needed with minimal weight
Application Guidelines
- Intakes: Use 3/16” SRPP instead of 1/4” polycarb for same strength at less weight
- Guards: 1/8” SRPP can replace 3/16” polycarb in many applications
- Bumpers: Excellent backing material due to impact resistance
- Mounting: Use washers to distribute load - material can compress