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05 Design

Robot Parts

Pick the right materials, set tolerances, and design chassis plates and brackets that survive the arena.

Interactive 3D Model: Wheel & Axle — a revolved wheel with spokes and central hub on an axle shaft.

Designing Durable Robot Parts

Understanding materials, geometry, and tolerances ensures your parts survive real-world forces.

Common Materials in Robotics
Material Pros Cons Common Use
Aluminum (6061) Light, strong, machinable More expensive than steel Structural plates, brackets
PLA Plastic Easy to 3D print, cheap Brittle, low heat tolerance Prototypes, sensor mounts
PETG Tough, flexible, printable Harder to print than PLA Functional parts, guards
Polycarbonate Extremely impact-resistant Needs enclosure to print Armor, shields, gears
Steel Very strong, durable Heavy, harder to machine Shafts, axles, gears
Tolerances & Fits

Tolerance is the acceptable variation range for a dimension. Getting this right means parts actually fit.

Clearance Fit

Shaft always smaller than hole — parts slide or rotate freely. Used for pivot pins, axles in bearings.

1 Experience
2 Reflect
3 Theorize
4 Apply
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Quick Review Opportunity

Revisit
Transition Fit

Shaft and hole nearly the same size; may need light pressing. Used for locating pins, alignment features.

Interference Fit

Shaft larger than hole — requires force to assemble. Used for press-fit bearings, permanent joints.

Design Features for Strength
  • Fillets on internal corners: Reduce stress concentrations that cause cracks. Always fillet load-bearing corners.
  • Ribs and gussets: Thin walls of material that add stiffness without adding much weight.
  • Lightening patterns: Pocketing or hex patterns remove material from low-stress areas to reduce weight.
  • Uniform wall thickness: Especially important for 3D-printed and injection-molded parts to prevent warping.
Robotics Tip: For 3D-printed parts, orient your print so that layer lines run parallel to the forces, not perpendicular. A part is weakest between layers.
⚙

Challenge

Find the print orientation that maximizes strength while keeping support material under 20%.

⚠ Predict First

Which print orientation do you think will produce the strongest part?

Layer adhesion is the weakest link in FDM prints. Parts are weakest perpendicular to layer lines.

Flat: maximum cross-section bonded per layer. Upright: tall but layers shear easily under side loads. Angled: compromise but needs more support material.

Rule of thumb: orient so the primary load runs parallel to layer lines.

Guided Exploration
  1. Set orientation to flat. Note the strength and support values.
  2. Switch to upright. How much did strength change? Why?
  3. Find the orientation that maximizes strength while keeping support under 15%.
Stage 2 Pause and Reflect
✓ Your reflections are saved automatically
Stage 4 Apply What You Learned

Design a sensor mounting bracket that must withstand vibration, be 3D-printable, and allow easy sensor replacement.

  • Choose a material based on the vibration and precision requirements
  • Identify the load-bearing direction and orient print layers accordingly
  • Add features for sensor retention (clips, slots, or screw holes)
  • Evaluate: does your design need supports? Can you redesign to avoid them?
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