Computer-Aided Design

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.

Create a Hybrid Design

In Fusion 360, start a new Hybrid Design — this supports both solid modeling and assembly components in one file.

Create a new component

After the design opens, create a separate Component in the browser — each link of the arm lives in its own component.

Activate the component

Select (double-click) the new component so it becomes active — all sketches and features are added inside this component.

Create Sketch

With the component active, click Create Sketch and choose a plane to start drawing the profile.

Draw the sketch profile

Use the sketch tools in the toolbar — lines, circles, dimensions, and constraints — to build the 2D profile before extruding.

Set up parametric parameters

Open Modify → Change Parameters, click the + button to add new parameters, and drive sketch dimensions from the parameter table. You can also use formulas to link dependent values to independent ones — e.g. set hole spacing as Base_Diameter / 4 so the whole design updates when a single value changes.

Parameter list in the design

Parameters with formulas linking dependent values

Extrude the sketch

Click Extrude, select the closed sketch profile, and set the extrusion distance. Link the extrude height to a parameter the same way as the sketch — type the parameter name (e.g. Base_Height) so the 3D body updates when the value changes.

Extrude the closed sketch profile

Set extrusion distance with a parameter

Base — add joint and complete first link

Added a central shaft on the extruded base and applied a Revolute Joint between Base and Link 1 for 360° rotation (first DOF).

Parameters: Base_Diameter, Base_Height, Mount_Hole_Diameter, Joint_Shaft_Diameter

Base side sketch

Base parameters

Base final result

Link 1 (Shoulder) — U-bracket and two joints

Created a new component, sketched a U-shaped bracket, and extruded it. Added two Revolute Joints: one to the base for horizontal rotation, one to Link 2 for vertical pitch.

Parameters: Link1_Length, Link1_Thickness, Joint_Spacing, Bracket_Width

Link 2 (Upper arm) — beam with ribs

Extruded a rectangular beam with internal ribs, then added a Revolute Joint to Link 1 for elbow motion, limited by Elbow_Max_Angle.

Parameters: Link2_Length, Link2_Width, Link2_Height, Rib_Thickness, Elbow_Max_Angle

Link 3 (Forearm) — lighter distal link

Modeled a smaller beam with cable channels and prepared the wrist mount before connecting to Link 2 at the elbow.

Parameters: Link3_Length, Link3_Width, Cable_Channel_Diameter, Wrist_Mount_Offset

Wrist assembly — pitch and roll

Built a compact housing with two orthogonal Revolute Joints for wrist pitch and roll, plus an end-effector mount.

Parameters: Wrist_Housing_Diameter, Wrist_Pitch_Range, Wrist_Roll_Range, End_Effector_Mount_Diameter

End effector base — tool mount and 6th DOF

Extruded a circular tool-mounting base with retention features, then added the final Revolute Joint for independent end-effector rotation (sixth DOF).

Parameters: End_Effector_Base_Diameter, Tool_Mount_Pattern, Retention_Feature_Depth, Rotation_Range

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