02

Computer-Aided Design

CAD Design & Parametric Modeling

📌 Assignment Overview

This week focused on two main tasks: designing a 6-axis robotic arm prototype (Final Project Draft) and revisiting the modular box from Week 3. Used Fusion 360 with parametric modeling to make design changes easier.

📋 Assignment Process

This section documents the step-by-step process of completing this week's assignment.

1. Technical Workflow & AI Assistance

Environment Setup

  • Operating System: macOS
  • CAD Software: Fusion 360
  • AI Tool: Gemini (for troubleshooting)

AI-Assisted Problem Solving

Used Gemini to solve these issues:

  • Constraint Issues: Sketch constraints didn't update when parameters changed. Fixed by using "Update" command.
  • Joint Alignment: Revolute Joints were misaligned. Used construction geometry and "Align" tool to fix.
  • Parameter Organization: Grouped related parameters and used clear names for easier management.

2. Parametric Robotic Arm Design

Design Strategy

Started a new Fusion 360 file and:

  • Created 6 empty components first
  • Set the height of two cylinders and the circle diameter, shown in the parameter diagram below
  • Made each component independent but connected

Component 1: Base

Design Process: Created a circular sketch with mounting holes. Used Extrude to make a cylindrical base. Added a central shaft for the joint connection.

Joint & Motion: Applied a Revolute Joint between Base and Link 1 for 360° rotation (first DOF).

Parameters:

  • Base_Diameter: Overall size
  • Base_Height: Height
  • Mount_Hole_Diameter: Hole sizes
  • Joint_Shaft_Diameter: Connection size
Component 1 Side Sketch

Component 1 Side Sketch

Component 1 Parameters

Component 1 Parameters

Component 1 Final Result

Component 1 Final Result

Component 2: Link 1 (Shoulder)

Design Process: Created a U-shaped bracket sketch. Used Extrude to make the 3D part. Added reinforcement at stress points.

Joint & Motion: Two Revolute Joints:

  1. To Base: Horizontal rotation
  2. To Link 2: Vertical rotation

Provides two DOF.

Parameters:

  • Link1_Length: Horizontal reach
  • Link1_Thickness: Material thickness
  • Joint_Spacing: Distance between joints
  • Bracket_Width: U-shape size

Component 2 Sketch

Component 2 Parameters

Component 2 Final Result

Component 3: Link 2 (Upper Arm)

Design Process: Made a rectangular sketch with rounded corners. Used Extrude to create a beam with internal ribs to reduce weight.

Joint & Motion: Revolute Joint to Link 1 for elbow bend/straighten motion.

Parameters:

  • Link2_Length: Length
  • Link2_Width: Width
  • Link2_Height: Height
  • Rib_Thickness: Rib size
  • Elbow_Max_Angle: Max rotation

Component 3 Sketch

Component 3 Parameters

Component 3 Final Result

Component 4: Link 3 (Forearm)

Design Process: Similar to Link 2 but smaller to reduce weight. Added wrist mounting and cable channels. Used Extrude for the main body.

Joint & Motion: Revolute Joint at elbow for rotation. Prepared wrist connection point.

Parameters:

  • Link3_Length: Length
  • Link3_Width: Width
  • Cable_Channel_Diameter: Cable space
  • Wrist_Mount_Offset: Wrist position

Component 4 Sketch

Component 4 Parameters

Component 4 Final Result

Component 5: Wrist Assembly

Design Process: Created a compact housing with two joints for pitch and roll. Added end effector mount and actuator space. Used Extrude for the housing.

Joint & Motion: Two Revolute Joints:

  1. Wrist Pitch: Up/down motion
  2. Wrist Roll: Rotation around forearm

Parameters:

  • Wrist_Housing_Diameter: Size
  • Wrist_Pitch_Range: Pitch limit
  • Wrist_Roll_Range: Roll limit
  • End_Effector_Mount_Diameter: Mount size

Component 5 Sketch

Component 5 Parameters

Component 5 Final Result

Component 6: End Effector Base

Design Process: Created a circular sketch for tool mounting. Used Extrude to make a cylindrical base with tool retention features. Added alignment and fastener holes.

Joint & Motion: Final Revolute Joint to wrist (6th DOF) for independent rotation.

Parameters:

  • End_Effector_Base_Diameter: Mount size
  • Tool_Mount_Pattern: Hole pattern
  • Retention_Feature_Depth: Lock depth
  • Rotation_Range: Max rotation

Component 6 Sketch

Component 6 Parameters

Component 6 Final Result

3. Modular Box Integration

Revisited the modular box from Week 3 and made it parametric:

  • Fitment: Joint clearances controlled by parameters (Joint_Clearance, Material_Thickness)
  • Scalability: Box size adjustable via parameters (Box_Length, Box_Width, Box_Height)
  • Quick Changes: Can try different sizes without recalculating joints

📝 Assignment Notes

Parametric modeling worked well for this project. Key benefits:

  • Quick Changes: Modify parameters instead of editing sketches
  • Consistency: Related dimensions stay synchronized
  • Easy to Maintain: Clear structure and naming
  • Manufacturing Ready: Can quickly generate different sizes

All 6 components respond to parameter changes while keeping joints and assembly correct. This will help with future development.