HOIISP

H.A.R.S — Hygroscopic Aerodynamic Restoration System

Repository: https://github.com/BasilSaeedBari-bb09892/H.A.R.S
Approved: 2026-05-11 08:56:48
Last Push: 2026-05-11T09:02:11Z

An Open-Source, Ultra-Low-Cost Closed-Loop Active Convection Desiccant Chamber for 3D Printing Filament Restoration Polymer hydration is the primary point of failure in 3D printing in high-humidity environments. In Karachi, where ambient relative humidity regularly exceeds 70–90%, hygroscopic filaments such as PLA, PETG, and Nylon rapidly absorb atmospheric moisture. This absorbed water vaporises explosively inside the extruder nozzle at printing temperatures, causing stringing, bubbling, poor layer adhesion, and structurally compromised prints. The H.A.R.S (Hygroscopic Aerodynamic Restoration System) project addresses this problem by engineering an ultra-low-cost, open-source, closed-loop active desiccant chamber that actively strips moisture from saturated filament using four integrated physical mechanisms: forced convection via a 3D-printed Venturi nozzle (Bernoulli's Principle), bulk moisture removal via a copper cold coil (phase-change condensation), trace humidity adsorption via an indicating silica gel bed, and precise thermal regulation via a PID control loop running on an ESP32 microcontroller. The system is designed entirely around scrap, repurposed, and locally sourced Pakistani market components, targeting a total Bill of Materials cost under ₨5,500. A successful outcome is defined as dropping internal relative humidity below 15% within 30 minutes of activation while maintaining a stable chamber temperature of 45°C ± 2°C — well below the glass transition temperature of the polymers being dried. All hardware schematics, 3D-printable STL files, and firmware will be released as open-source for the wider Pakistani maker and engineering community. Future milestones will progressively downscale the electronics stack from an ESP32 development board to bare-metal AVR ICs and ultimately to a sub-₨200 analogue control circuit.

In Karachi's high-humidity climate, 3D printing filament degradation due to moisture absorption is a persistent, unsolved problem for hobbyists, hardware engineers, and university makerspaces. Hygroscopic polymers — PLA, PETG, Nylon, TPU — absorb water at the molecular level from ambient air within hours of exposure. Once hydrated, the filament cannot simply be "used carefully"; the moisture must be physically extracted before printing. The two categories of available solutions are both inadequate for the local context. Commercial active filament dryers (Sunlu, eSun, PrintDry) are imported products subject to heavy Pakistani customs duties, placing them in the ₨8,000–15,000 price range — unviable for student budgets. Beyond cost, these devices rely on brute-force convection heating that risks thermally warping the lower layers of a spool if left unattended, and they provide no feedback control to prevent this. DIY passive dry boxes — airtight containers with loose silica gel — are the community's default response. However, these are preventive tools, not restorative ones. Stagnant air inside the box maintains a near-equilibrium humidity with the saturated silica, and without forced convection, the Vapor Pressure Deficit driving moisture out of the filament approaches zero. A heavily hydrated spool of PETG requires many days in a passive dry box to reach printable moisture levels. There is a critical, unmet need for an accessible, reproducible, restorative drying system that applies the correct physics — forced convection, phase-change condensation, and active desiccation — to rapidly restore hydrated filament to printable condition, built entirely from components available in the Pakistani local market.