Key Attributes:

• Developed system+code to enlarge diameter of polyurethane tubing.

• Utilized glass cylinders, or drilled, reamed, and electropolished copper, as size was too small for mechanical polishing/honing etc.

• PID controlled temperature + static pressure; pressure drop indicates balloon formation.

• Made heating element out of Ni-Cr wire, wrapped around the core, then cast whole assembly in silicone rubber for heat insulation.

• Controlled heat with high-amperage motor controller + arduino; Sensors+pid/master program through NI DAQ and MATLAB.

Challenges

• High temperature fluctuations led to balloon ripping; PID had to be fine-tuned.

• Accurate temperature reading; could only sense outside of core. Thus, temperature set points/PID tuning were configured per core material.

• Surface roughness of balloon was of upmost importance; took many iterations of core manufacturing methodology.