Desktop Robotic Arm

Overview

This project is a fully custom desktop robotic arm designed from scratch with a focus on precision, structural reliability, and practical system integration. Unlike my previous software-heavy projects, this build pushes into physical engineering: mechanical design, torque constraints, actuation choices, PCB design, and power distribution.

The goal is to develop a functional prototype capable of lifting a 300g load at maximum reach while keeping backlash low, maintaining a realistic budget, and avoiding prebuilt robotic arm kits or tutorial-based designs.

Design Constraints

• Working prototype targeted within 2–3 months
• Lift 300g at maximum reach
• Keep backlash as low as possible
• Stay within a total budget of $300
• Prioritize strength, precision, and reliability over cosmetic complexity
• No outsourced robotic arm designs or tutorial-based builds

Architecture Decisions

Early design work focused on choosing an arm structure that balanced cost, strength, and manufacturability. After reviewing different robotic arm layouts, I chose a double-supported segmented structure rather than a more expensive industrial-style modular gearbox design.

I also compared steppers and servos for different joints. Stepper motors were selected for the base roll, base pitch, and elbow due to their positional control and compatibility with higher external gear reduction. Servo motors were reserved for lower-load wrist and gripper functions where compact integrated actuation makes more sense.

Mechanical Design

The arm is being designed in FreeCAD, with ongoing iteration around geometry, joint spacing, and weight distribution. A key design goal is to keep heavier components closer to the base while preserving enough reach for useful desk-scale tasks.

For power transmission, I moved away from large spur gear stacks and toward belt-driven reduction. This makes high gear ratios more compact, easier to route, and better suited to remote actuation where the motors can stay closer to the base.

CAD model of the robotic arm structure

Electronics & PCB

A custom PCB was designed to support motor control, power regulation, and cleaner system integration. The board is built around TMC2209 stepper drivers and a Raspberry Pi Pico, with separate power handling for motor drivers, servos, and control logic.

This design was not just for cleaner wiring. It also improves modularity, simplifies debugging, and creates a more scalable platform for future revisions and added features.

Custom PCB for motor control and power distribution

Engineering Focus

• Torque analysis and load-driven design decisions
• Weight distribution and structural tradeoffs
• Backlash reduction and motion precision
• Remote actuation and compact power transmission
• System-level integration of mechanics, electronics, and control

Current Status

The CAD model is complete in its current revision, the PCB has been designed, and major components have been selected. The project is now moving into optimization, prototyping, and physical validation.

Next steps include refining the structure for weight and manufacturability, validating torque assumptions in the real build, and iterating on any issues that appear during assembly and testing.

Why This Project Matters

This project is important to me because it moves beyond software into full engineering system design. It requires balancing constraints, making design tradeoffs, and building something that must work in the real world rather than only in code.

More than anything, it reflects the kind of work I want to keep doing: practical, hands-on engineering that combines hardware, software, and thoughtful design decisions.