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Overview

Computer-Aided Design (CAD) allows you to create accurate 3D models of your robot before building it. This saves time, money, and prevents costly mistakes during assembly.
Recommended Software: Fusion 360 (free for students) or SolidWorks (university license) Alternative: FreeCAD (free, open-source)

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Design Workflow

1

Define Requirements

List all components, dimensions, and constraints from simulation and component datasheets
2

Sketch Base Plate

Create main chassis platform with mounting holes
3

Add Motor Mounts

Design or import motor mounting brackets
4

Position Components

Place all electronics, sensors, battery in assembly
5

Check Clearances

Verify no interference between parts, adequate cable routing space
6

Refine and Detail

Add fasteners, wire management, access panels
7

Generate Outputs

Export STL for 3D printing, create technical drawings, finalize BOM

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Key Dimensions

Based on your MATLAB simulation and component sizes:

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Robot Footprint

Suggested dimensions (adjust for your design):
- Wheelbase (L): 300mm (front-rear distance)
- Track Width (W): 250mm (left-right distance)
- Overall length: ~350mm (including wheel protrusion)
- Overall width: ~300mm
- Height: ~150-200mm (accommodate battery + electronics)

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Component Clearances

  • Wheel clearance: 5-10mm from chassis edges
  • Motor shaft alignment: Critical! Must be precise for Mecanum wheels
  • Electronics spacing: 10mm minimum between boards for airflow
  • Battery access: Easy removal without disassembly
  • Cable routing: 15-20mm channels or space

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Design Guide by Component

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1. Base Chassis Plate

Material Options:
  • 3D Printed PLA/PETG: Quick, customizable, adequate strength
  • Laser-cut Acrylic: Flat, precise, good for electronics mounting
  • Aluminum sheet: Strong, professional, requires machining
Design Considerations: 
Thickness: 3-5mm (3D print) or 5mm (acrylic)
Mounting holes: M3 or M4 throughout
Corner radius: 5-10mm (reduce stress concentration)
Weight: Keep under 500g if possible
Fusion 360 Tutorial - Base Plate: 
1. Create new component: "Base Plate"
2. Create sketch on XY plane
3. Draw rectangle: 300mm × 250mm
4. Fillet corners: 10mm radius
5. Extrude: 4mm thickness
6. Add mounting holes using Rectangular Pattern:
   - Hole size: 3.2mm (for M3 screws)
   - Spacing: 20mm grid
   - Counterbore if needed for flush fitment
Base chassis plate with mounting holes

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2. Motor Mounts

Critical Requirements:
  • Precise hole spacing matching motor face
  • Rigid mounting (no flex during operation)
  • Proper shaft alignment (perpendicular to chassis)
  • Encoder wire routing clearance
Design Approach: 
Option A: L-bracket style
- Vertical plate mounts to motor
- Horizontal plate mounts to chassis
- Simple, easy to print

Option B: Integrated standoff
- Motor face mounts flush to bracket
- Bracket elevates motor above chassis
- Better wire routing, cleaner look

Recommended: Use Option B with 4× M3 holes matching motor
Fusion 360 - Motor Mount: 
1. Measure your DC motor:
   - Body diameter: typically 37mm
   - Mounting hole pattern: e.g., 4× M3 on 30mm PCD
   - Shaft position and diameter

2. Create sketch with motor hole pattern
3. Add mounting tabs to chassis (M3 holes, 40mm spacing)
4. Extrude with adequate thickness (4-5mm walls)
5. Add shaft clearance hole
6. Fillet edges for strength
Critical: Motor shaft must be perfectly perpendicular to chassis! Any misalignment causes Mecanum wheel malfunction and excessive wear.

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3. Wheel Assembly

Mecanum Wheel Considerations:
  • Wheels come in pairs: Left-hand and Right-hand rollers
  • Typical sizes: 60mm, 80mm, 100mm diameter
  • Hub bore: Check your wheel’s bore diameter and shaft diameter
  • Coupling: May need adapter or set-screw hub
Mounting: 
1. Motor shaft → Coupling/hub → Wheel
2. Ensure wheel can't slide off (set screw, retaining clip)
3. Check wheel doesn't rub chassis at full rotation
4. Minimum 5mm clearance all around
Importing Commercial Wheels: Many suppliers provide CAD models (STEP or STL):
  • Check manufacturer website
  • GrabCAD library
  • Or model simplified version yourself

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4. Electronics Mounting

ESP32:
  • Mount on standoffs (M2.5 or M3, height: 10-15mm)
  • Access to USB port for programming
  • Ventilation for heat dissipation
Motor Drivers (4× IBT-2):
  • Can get hot! Mount with airflow
  • Short wires to motors (minimize EMI)
  • Accessible for debugging
  • Consider stacking or side-mounting
Raspberry Pi:
  • Standard mounting: 4× M2.5 holes, 58mm × 49mm spacing
  • Access to all ports (USB, Ethernet, HDMI, GPIO)
  • microSD card accessible
  • Active cooling recommended (small fan or heatsink)
IMU (ICM-20948):
  • Rigid mounting (no vibration)
  • Centered on robot for best results
  • I2C wire length: keep under 300mm
LiDAR (A1M8):
  • Top-mounted, elevated above chassis
  • 360° clear view (no obstructions)
  • Stable mounting (no wobble)
  • Height: 100-150mm above ground

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5. Power System

Battery Placement:
  • Low and centered (improve stability, CG)
  • Secured with straps or cage (prevent movement)
  • Easy access for charging/replacement
  • Consider LiPo safety bag
Power Distribution:
  • Centralized bus or PCB for distribution
  • Fuse holders accessible
  • Clear labeling of voltages (12V, 5V, GND)

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Bill of Materials (BOM)

Your CAD model helps generate accurate BOM:

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BOM Structure

Part NumberDescriptionQtyMaterial/SupplierUnit CostNotes
BP-001Base Plate13D Print PLA-STL provided
MM-001Motor Mount43D Print PETG-STL provided
MW-001Mecanum Wheel 100mm4AndyMark #am-3655$25Left+Right pairs
FS-M3-10M3×10mm Socket Head Screw20McMaster-Carr$0.10Stainless
FS-M3-NUTM3 Hex Nut20McMaster-Carr$0.05Stainless
………………
Categories to include:
  • Structural (chassis, mounts, standoffs)
  • Fasteners (screws, nuts, washers, spacers)
  • Electronics (see hardware BOM)
  • Wiring (cables, connectors, heat shrink)
  • Miscellaneous (velcro, zip ties, adhesive)
Spares: Order 10-20% extra fasteners and connectors. They’re cheap and you WILL drop some!

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Assembly Planning

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Assembly Sequence

Document step-by-step assembly: 
1. Prepare base plate
2. Install motor mounts (4×)
3. Mount motors to brackets
4. Attach wheels to motor shafts
5. Install electronics standoffs
6. Mount ESP32
7. Mount motor drivers
8. Mount Raspberry Pi
9. Mount IMU
10. Install LiDAR tower/mount
11. Wire power distribution
12. Connect signal wires
13. Secure battery
14. Cable management (zip ties)
15. Final inspection

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Exploded View

Create exploded assembly view in CAD:
  • Shows how parts fit together
  • Useful for documentation and assembly instructions
  • In Fusion 360: Right-click assembly → “Create Exploded View”

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3D Printing Guidelines

Reminder: Maximum 2 prints per group. Make them count!

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Pre-Print Checklist

  • All parts fit within printer build volume (check dimensions)
  • Wall thickness ≥ 2mm (structural parts)
  • No unsupported overhangs >45° (or add supports)
  • Mounting holes sized for post-printing (3.2mm for M3 tapping)
  • Parts oriented for optimal strength (layer direction matters!)
  • STL exported without errors
Material: PLA or PETG
Layer Height: 0.2mm (good balance speed/quality)
Infill: 20-30% (structural parts), 10-15% (cosmetic)
Wall Thickness: 3-4 perimeters
Top/Bottom Layers: 4-5 layers
Supports: Only if needed (add manually in slicer)
Brim/Raft: Use brim for better bed adhesion

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Post-Processing

  • Cleanup: Remove supports, clean holes with drill bit
  • Hole tapping: Tap M3 holes for threads (or use heat-set inserts)
  • Surface finish: Sand if needed (start 220 grit → 400 grit)
  • Assembly test: Dry-fit before final assembly

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Technical Drawing

Create 2D engineering drawing showing:
  • Top view: Overall dimensions, mounting hole locations
  • Side view: Heights, clearances
  • Detail views: Motor mounts, critical features
  • Dimensions: All key measurements
  • Notes: Materials, tolerances, special instructions
In Fusion 360: 
1. Create new drawing: Right-click design → "Create Drawing"
2. Insert base view (Top, Front, Right)
3. Add dimensions
4. Add section views if needed
5. Export as PDF

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CAD Resources

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Learning Resources

  • Fusion 360:
  • SolidWorks:
    • University tutorials (check your course portal)
    • YouTube: “SolidWorks Tutorial for Beginners”
  • FreeCAD:

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CAD Model Libraries

  • GrabCAD: Free CAD models (motors, electronics, fasteners)
  • McMaster-Carr: Downloadable CAD for all hardware
  • TraceParts: Large library of commercial components
  • Manufacturer websites: Often provide STEP files

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Useful Tools

  • Fastener calculators: Proper hole sizing for tapped vs clearance
  • Tolerance calculators: Fit types (slide, press, clearance)
  • Stress analysis: Fusion 360 and SolidWorks have built-in FEA

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Common CAD Mistakes

Problem: Part designed flat won’t print well in that orientationFix: Consider layer strength. Mount holes perpendicular to loads, critical features oriented for minimal supports
Problem: 3D prints have ±0.2mm tolerance, parts don’t fitFix: Add 0.3-0.5mm clearance for sliding fits, test fit before final print
Problem: 1mm walls crack under loadFix: Minimum 2-3mm for structural parts, use ribs/gussets for reinforcement
Problem: Wires interfere with movement, look messyFix: Design channels, clips, or conduits in CAD. Plan cable paths early!
Problem: Can’t reach screws for assembly/disassemblyFix: Check tool access (hex key, screwdriver). Add access holes or chamfers

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Tips for Success

Start Simple

Begin with basic box, add complexity gradually. Don’t try perfect design first iteration.

Use Parameters

Parametric design lets you easily adjust dimensions (wheelbase, track width) and update entire model.

Real Measurements

Measure components with calipers! Datasheets sometimes have errors or tolerance ranges.

Learn from Others

Study existing Mecanum robot designs online (GrabCAD, Thingiverse, research papers).

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Next Steps

PCB Design

Design electrical connections and wiring

Mechanical Assembly

Assembly guide and integration

Hardware Specs

Component dimensions for CAD modeling

Fusion 360 Guide

Software installation and tips

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References

[1] Fusion 360 Student Download: https://www.autodesk.com/education/home [2] GrabCAD Library: https://grabcad.com/library [3] McMaster-Carr (CAD models): https://www.mcmaster.com/