Compact Materials Testing Machine

Compact Materials Testing Machine (April 2025)

Design Lead and Project Manager, First Year Engineering Projects at CU Boulder

Project Objective: Developed an interactive, open-source testing rig to help engineering students visualize and measure flexure in a cantilevered beam. The system bridges the gap between theoretical deflection equations and physical material behavior.
Accessible Architecture: Engineered specifically as a low-cost classroom tool with a total budget under $350. The open-source design allows engineering professors to easily replicate the system for demonstrations using standard rapid-prototyping tools.
Material Testing: The machine is designed to securely clamp and apply a cantilever bending load to interchangeable 30mm x 150mm x 5mm material samples of varying compositions.

Final Device

Full CAD: Orange—Acrylic, Red—Moving PLA Parts, Green—Fixed PLA Parts

Chassis & Structural Routing: Constructed from 3D-printed PLA and laser-cut acrylic using standard M3 hardware. The chassis geometry was specifically engineered to route the generated bending forces in-plane with the relatively flexible acrylic side panels, significantly maximizing the machine's overall rigidity.
Actuation & Intuitive Design: A NEMA 17 stepper motor and GT2 timing belt drive a lead screw, moving the load cell assembly along a standard 3D-printer linear rail. To enhance visual learning, the force applicator was shaped like a downward arrow and prominently embossed with the letter "F" to intuitively represent the applied force vector.
Portability & Accessibility: Designed as a compact, battery-powered unit capable of several hours of runtime for easy classroom portability and storage. The Arduino is mounted with its programming and power ports fully accessible through custom side-panel cutouts, allowing users to plug in a computer to externally power the device and easily modify test variables (such as material thickness) without taking the machine apart.

Mechanical Components

Force Applicator Subassembly

Rotation Transfering System

Sensing & Positioning: An integrated load cell measures applied force, while vertical displacement is tracked precisely via stepper motor steps, eliminating the need for an external encoder. Limit switches allow reliable vertical axis re-zeroing before each test.
User Interface: The control panel features dedicated Start and Emergency Stop buttons, plus adjustable knobs allowing the user to dial in the target force and the specific Young’s Modulus of the test material.
Data Output & Accuracy: An LCD screen displays real-time applied force alongside both the measured and theoretical deflections. During physical validation, the machine successfully modeled cantilever equations with sub-0.5mm accuracy.

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