15. System Integration¶
Overview¶
This week brought together every element of the Vahan CO₂/CO gas monitoring device into a single finished product. The work covered enclosure design in FreeCAD using GrabCAD components, 3D printing, surface preparation with putty and sanding, priming, painting, and final assembly of all electronics.
Enclosure Design¶
The process started with a hand sketch to work out the overall form, proportions, and internal layout before opening any software. The key decisions at this stage were the placement of the gas sensors, the PCB mounting points, and the alert outputs — making sure everything had a defined position before modeling began.
The enclosure was modeled in FreeCAD. To make the 3D model accurate, I downloaded the real component models — PCB, sensors, and other parts — directly from GrabCAD and placed them inside the enclosure model. This allowed me to verify clearances and check that every part fit in its intended position before printing anything.
The enclosure features dedicated openings for the gas sensors, sized to match the actual components.
The PCB mounting points were designed to accept screws, keeping the board firmly in place inside the housing.
The internal layout was validated with all GrabCAD components placed in position, confirming clearances before committing to print.
3D Printing¶
All enclosure parts were printed in PETG on the Prusa MK4S. PETG was the right choice for this project — it handles heat better than PLA and is more resistant to the fumes and conditions present in a forge environment, which is exactly where Vahan is intended to be used.
The parts came off the printer with good dimensional accuracy, and all openings aligned correctly with their intended components.
After removing the parts from the build plate, support material was cleaned up and the fit of each piece was checked before moving to finishing.
Surface Finishing¶
Fresh off the printer, the parts had visible layer lines that needed to be addressed before painting. Putty was applied over the surfaces to fill the gaps and imperfections.
After the putty cured, the surfaces were sanded smooth. This step makes a significant difference in the final appearance — the goal was for the enclosure to look manufactured rather than printed.
Painting¶
A primer coat was applied first to seal the surface and improve paint adhesion. It also helped reveal any remaining low spots that needed a second pass before the final color.
The enclosure was then painted in dark asphalt grey — a color chosen to suit the industrial context of a forge workshop.
Final Assembly¶
With the painted enclosure fully cured, all components were installed. The PCB was screwed into its mounting points inside the housing. The gas sensors were seated into their dedicated openings in the enclosure wall, positioned to sample the surrounding air directly. All wiring was routed neatly inside the housing with proper headers.
The XIAO RP2040 serves as the brain of the device, reading sensor data and triggering the LED indicators and buzzer when gas levels exceed safe thresholds — giving the user clear visual and audible alerts without the need for a display.
The enclosure also features a decorative metal element cut from steel sheet, designed to reference the shape of a shield — directly connecting the physical form of the device to its name, Vahan, which means “shield” in Armenian. This piece was produced during Wildcard Week using metal laser cutting. For details on the cutting process, see the
